PATENT DOCUMENT

Publication Number: US-8751667-B2
Application Number: US-201113223266-A
Country: US
Kind Code: B2

Title: Supporting hands-free services via a hands-free device for IP video calls

Abstract:
Hands-free services for Internet Protocol (IP) video calls through a peered hands-free device can begin when an IP video call invitation request that requests the client computing device participate in a P2P (peer-to-peer) IP video call is received. A generic incoming call object is generated based on the IP video call invitation request in a format that can be common for both incoming audio only cellular calls and IP video call invitation requests. The hands-free device is alerted of the incoming call based on the incoming call object. Responsive to receiving an indication from the hands-free device that a user has indicated to answer the incoming call, an IP video call accept message is transmitted and a P2P connection is established for the P2P IP video call, and the hands-free device can act as an auditory relay during the P2P IP video call.

Claims:
What is claimed is: 
     
       1. A method performed in a client computing device for providing hands-free services for Internet Protocol (IP) video calls through a hands-free device, comprising:
 receiving an IP video call invitation request that requests the client computing device participate in a P2P (peer-to-peer) IP video call; 
 generating a generic incoming call object based on the IP video call invitation request in a format that is common for both incoming audio only cellular calls and IP video call invitation requests, the incoming call object including a set of parameters regarding the incoming call, wherein the set of parameters regarding the call includes a status of the call, a call participant identifier, a start time, and a call identifier; 
 alerting the hands-free device of the incoming call based on the incoming call object; 
 responsive to receiving an indication from the hands-free device that a user has indicated to answer the incoming call, transmitting an IP video call accept message; 
 establishing a P2P connection for the P2P IP video call; and 
 routing an audio portion of the P2P IP video call through the hands-free device such that the hands free device acts as an auditory relay during the P2P IP video call, while displaying a portion of the video call on the client device. 
 
     
     
       2. The method of  claim 1 , further comprising establishing an audio connection with the hands-free device after establishing the P2P connection for the P2P IP video call. 
     
     
       3. The method of  claim 1 , wherein the hands-free device is a car-kit. 
     
     
       4. The method of  claim 1 , further comprising routing the audio portion of the IP video call through the hands-free device responsive to receiving a command from the hands-free device to transfer the audio. 
     
     
       5. A non-transitory machine-readable storage medium that provides instructions that, when executed by a processor, will cause the processor to perform operations for providing hands-free services for Internet Protocol (IP) video calls through a hands-free device, the operations comprising:
 receiving an IP video call invitation request specific to the client computing device that requests the client computing device to participate in a P2P (peer-to-peer) IP video call; 
 generating a generic incoming call object based on the IP video call invitation request in a format that is common for both incoming audio only cellular calls and IP video call invitation requests, the incoming call object including a set of parameters regarding the incoming call, wherein the set of parameters regarding the call includes a status of the call, a call participant identifier, a start time, and a call identifier; 
 alerting the hands-free device of the incoming call based on the incoming call object; 
 responsive to receiving an indication from the hands-free device that a user has indicated to answer the incoming call, transmitting a device specific IP video call accept message; 
 establishing a P2P connection for the P2P IP video call; and 
 routing an audio portion of the P2P IP video call through the hands-free device such that the hands free device acts as an auditory relay during the P2P IP video call. 
 
     
     
       6. The machine-readable storage medium  claim 5 , further comprising instructions to perform operations including establishing an audio connection with the hands-free device after establishing the P2P connection for the P2P IP video call. 
     
     
       7. The machine-readable storage medium of  claim 5 , wherein the hands-free device is a car-kit. 
     
     
       8. The machine-readable storage medium of  claim 5 , further comprising instructions to perform operations including routing the audio portion of the IP video call through the hands-free device responsive to receiving a command from the hands-free device to transfer the audio, while continuing to display a video portion of the video call on the client device. 
     
     
       9. A client computing device, comprising:
 a processor system including a system on an integrated circuit; 
 an internet protocol (IP) video call manager coupled to the processor system, to manage establishment of IP video calls and to generate and transmit a first call object, the first call object including a set of parameters regarding the IP video call; 
 a cellular call manager coupled to the processor system, to manage establishment of audio only cellular calls, and to generate and transmit a second call object, the second call object including a set of parameters regarding the audio only cellular call, wherein the first call object and second call object have a common format, and wherein the set of parameters regarding the IP video call and the set of parameters regarding the audio only cellular call each include a status of the call, a call participant identifier, a start time, and a call identifier; 
 a telephony manager coupled with the processing system, the IP video call manager and the cellular call manager to provide hands-free services via an external hands-free device for both IP video calls and audio only cellular calls on behalf of the IP video call manager and the cellular call manager, the hands-free services including: answer an incoming call via the external hands-free device, end a call via the external hands-free device, and initiate a call via the external hands-free device; and 
 a hands-free manager coupled to the telephony manager, to establish an audio connection with the hands-free device, wherein the hands-free manager sends a request to an audio manager to route an audio portion of the IP video call through the hands-free device while a video portion of the video call is displayed on the client device. 
 
     
     
       10. The computing device of  claim 9 , wherein the external hands-free device is a car-kit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/382,479, filed Sep. 13, 2010, and claims the benefit of U.S. Provisional Application Nos. 61/378,924 and 61/378,926, each filed Aug. 31, 2010, all of which are each hereby incorporated by reference. This application is also a continuation-in-part of U.S. patent application Ser. No. 12/886,479, filed on Sep. 20, 2010 and is incorporated herein by reference. This application is also a continuation-in-part of U.S. patent application Ser. No. 12/886,485, filed on Sep. 20, 2010 and is incorporated herein by reference. This application is also a continuation-in-part of U.S. patent application Ser. No. 12/886,490, filed on Sep. 20, 2010 and is incorporated herein by reference. U.S. patent application Ser. Nos. 12/886,479, 12/886,485, and 12/886,490 claim priority to U.S. Provisional Application Nos.:
         (1) Application No. 61/321,865 filed on Apr. 7, 2010;   (2) Application No. 61/321,866 filed on Apr. 7, 2010;   (3) Application No. 61/351,814 filed on Jun. 4, 2010;   (4) Application No. 61/378,924 filed on Aug. 31, 2010;   (5) Application No. 61/378,926 filed on Aug. 31, 2010; and   (6) Application No. 61/382,479 filed on Sep. 13, 2010.       

     This application may include related subject matter to co-pending, co-assigned U.S. Provisional Application No. 61/321,832, filed Apr. 7, 2010, and entitled: Apparatus and Method for Inviting Users to Online Sessions, which is incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments of the invention relate to the field of computer networking; and more specifically for supporting hands-free services for IP video calls with a hands-free unit (e.g., a headset, a car kit) over a WPAN (e.g., Bluetooth) network. 
     2. Background 
     Many implementations to provide online communication sessions (e.g., instant messaging, video conferencing, etc.) require users of computing devices to install software and/or register with the service. Thus as a prerequisite for a user to establish an online communication session with another user, both users must be registered and/or have the same software installed. Many implementations also maintain presence (e.g., a friendlist) that allows users to determine the status of other users (e.g., online, offline, away, etc.). 
     Large public networks, such as the Internet, frequently have connections to smaller private networks, such as those maintained by a corporation, Internet service provider, or even individual households. By their very nature, public networks must have a commonly agreed upon allocation of network addresses, i.e., public addresses. For a variety of reasons, maintainers of private networks often choose to use private network addresses for the private networks that are not part of the commonly agreed upon allocation. Thus, for network traffic from the private network to be able to traverse the public network, some form of private/public network address translation (“NAT”) is required. 
     A device performing NAT operations alters the data packets being sent out of the private network to comply with the addressing scheme of the public network. Particularly, the network address translator replaces the originating private address and port number of a packet with its own public address and an assigned port number. A network address translator also alters the data packets being received for computers on the private network to replace the destination public address and port number with the correct private address and port number of the intended recipient. As used herein, the term address should be construed to include both an address and a port number if appropriate in the context, as would be understood by one of ordinary skill in the art. 
     NAT has become increasingly common in modern network computing. One advantage of NAT is that it slows the depletion of public network address space. For example, TCP/IP addressing, which is used on the Internet, comprises four strings of three digits each, thus providing a finite address space. Additionally, certain portions of this address space are reserved for particular uses or users, further depleting the actual number of addresses available. However, if NAT is used, a private network or subnet may use an arbitrary number of addresses, and still present only a single, standardized public address to the outside world. This makes the number of available addresses practically limitless, because each private network could, theoretically, use exactly the same private addresses. 
     One advantage provided by NAT is increased security arising from the fact that those on the public network cannot determine the actual (i.e., private) network address of a computer on a private network. This is because only the public address is provided on the public network by the network address translator. Additionally, this public address may correspond to any number of computers on the private network. 
     Different NAT types employ different levels of security. For example, with a “full cone NAT,” once an internal address (iAddr:iPort) is mapped to an external address (eAddr:ePort), any external host can send packets to iAddr:iPort by sending packets to eAddr:ePort. With a “restricted cone NAT,” an external host with an address hAddr can send packets to iAddr:iPort by sending packets to eAddr:ePort only if iAddr:iPort had previously sent a packet to hAddr. The port of the external host is irrelevant. With a “Port Restricted Cone NAT,” an external host having an address/port hAddr:hPort can send packets to iAddr:iPort by sending packets to eAddr:ePort only if iAddr:iPort previously sent a packet to hAddr:hPort. Finally, with a Symmetric NAT, each request from the same iAddr:iPort to a specific destination IP address and port is mapped to a unique eAddr:ePort. If the same internal host sends a packet to a different destination, a different external address and port mapping is used. Only an external host that receives a packet from an internal host can send a packet back to the internal host. 
     Peer-to-peer (“P2P”) computing refers to a distributed network architecture comprised of computing nodes which make a portion of their resources directly available to other network participants. Peers in a P2P network establish direct communication channels with one another and act as both clients and servers, in contrast to the traditional client-server model in which servers supply resources and clients consume resources. 
     The NAT operations described above pose numerous problems for P2P connections. For example, establishing a direct connection between two peers becomes increasingly difficult if one or both of the peers is located behind one or more of the NAT types described above. This problem is exacerbated by the fact that client devices such as the Apple iPod Touch®, Apple iPhone®, Apple iPad® and various other devices (e.g., RIM Blackberry® devices, Palm Pre® devices, etc) are frequently moved between networks having different NAT implementations. For example, the Apple iPhone™ is capable of communicating over Wi-Fi networks (e.g., 802.11b, g, n networks); 3G networks (e.g., Universal Mobile Telecommunications System (“UMTS”) networks, High-Speed Uplink Packet Access (“HSUPA”) networks, etc); and Bluetooth networks (known as personal area networks (“PANs”)). Future client devices will be capable of communicating over additional communication channels such as WiMAX, International Mobile Telecommunication (“IMT”) Advanced, and Long Term Evolution (“LTE”) Advanced, to name a few. 
     Hands-free units (e.g., headsets, car kits) are typically used to peer with a computing device for hands-free services. For example, it is common for a computing device that includes cellular telephony functionality to include the ability to peer with a hands-free unit that acts as an auditory relay between the hands-free unit and the computing device. 
     SUMMARY 
     Providing hands-free services for Internet Protocol (IP) video calls through a peered hands-free device is described herein. In one embodiment, an IP video call invitation request that requests the client computing device participate in a P2P (peer-to-peer) IP video call is received. A generic incoming call object is generated based on the IP video call invitation request in a format that is common for both incoming audio only cellular calls and IP video call invitation requests. The hands-free device is alerted of the incoming call based on the incoming call object. Responsive to receiving an indication from the hands-free device that a user has indicated to answer the incoming call, an IP video call accept message is transmitted and a P2P connection is established for the P2P IP video call. The audio portion of the P2P IP video call is routed through the hands-free device such that it can act as an auditory relay during the P2P IP video call. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings: 
         FIG. 1  is a data flow diagram illustrating registering a client device for online communication sessions according to one embodiment; 
         FIG. 2  is a block diagram illustrating the client device of  FIG. 1  in more detail according to one embodiment; 
         FIG. 3  is a block diagram illustrating the registration server of  FIG. 1  in more detail according to one embodiment; 
         FIG. 4  is a flow diagram illustrating exemplary operations for registering a client device for online communication sessions according to one embodiment; 
         FIG. 5  illustrates an exemplary registration data store according to one embodiment; 
         FIG. 6  illustrates a general network topology of one embodiment; 
         FIG. 7  is a data flow diagram illustrating online communication session establishment between client devices according to one embodiment; 
         FIG. 8  is a block diagram illustrating an exemplary relay service according to one embodiment; 
         FIG. 9  illustrates one embodiment of an API architecture according to one embodiment; 
         FIG. 10  illustrates an exemplary registration data store according to one embodiment; 
         FIG. 11  illustrates an exemplary NAT compatibility table according to one embodiment; 
         FIG. 12  illustrates an exemplary client device and a graphical user interface that is used to transition between circuit switched calls and video calls in accordance with some embodiments; 
         FIG. 13  illustrates the client device of  FIG. 12  displaying a video preview according to one embodiment; 
         FIG. 14  illustrates an exemplary client device and graphical user interface that is used to accept or deny video call invitations according to one embodiment; 
         FIGS. 15 and 16  illustrate client devices after transitioning to a video call according to one embodiment; 
         FIGS. 17 and 18  are flow diagrams that illustrate exemplary operations for transitioning between an audio only circuit switched phone call to a video call according to one embodiment; 
         FIG. 19  is a flow diagram illustrating exemplary operations performed on a client device that has received a video call reject message according to one embodiment; 
         FIG. 20  is a flow diagram illustrating exemplary operations performed on a client device for transitioning from a video call to a circuit switched call according to one embodiment; 
         FIG. 21  illustrates a general network topology used to register a client device for online communication sessions using an email address as an online communication session endpoint identifier according to one embodiment; 
         FIGS. 22A-B  are flow diagrams illustrating exemplary operations for registering an email address as an online communication session endpoint identifier according to one embodiment; 
         FIG. 23  is a flow diagram that illustrates exemplary operations for a user providing initialization information for registering an email address as an online communication session endpoint identifier according to one embodiment; 
         FIG. 24  illustrates exemplary operations for validating an email address according to one embodiment; 
         FIG. 25  is a flow diagram illustrating exemplary operations performed on a registration service when an email address has been validated according to one embodiment; 
         FIG. 26  is a data flow diagram illustrating exemplary operations for managing invitations when a user has multiple client devices that are associated with the same online communication session endpoint identifier according to one embodiment; 
         FIG. 27  is a data flow diagram that illustrates exemplary operations that are performed when a direct P2P connection is feasible according to one embodiment; 
         FIG. 28  is a data flow diagram illustrating exemplary operations that are performed when a direct P2P connection is infeasible according to one embodiment; 
         FIG. 29  is a data flow diagram that illustrates exemplary operations performed when an online communication session ends according to one embodiment; 
         FIG. 30  is a flow diagram illustrating exemplary operations performed to transfer an online communication session from one client device to another client device according to one embodiment; 
         FIG. 31  is a flow diagram illustrating exemplary operations for initiating and establishing an online communication session with multiple users according to one embodiment; 
         FIG. 32  is a block diagram illustrating a client computing device interfacing with a hands-free unit in accordance with one embodiment; 
         FIG. 33  illustrates a client computing device receiving an invitation for a video call, causing a hands-free device to ring, receiving an answer indication from the hands-free device, establishing the video call, and routing the audio to the hands-free device in accordance with one embodiment; 
         FIG. 34  illustrates a client computing device initiating a video call and routing the audio for the established video call through a hands-free device in accordance with one embodiment; 
         FIG. 35  illustrates a client computing device initiating a video call responsive to receiving a call request from a hands-free device in accordance with one embodiment; 
         FIG. 36  illustrates a client computing device routing audio of an established video call to a hands-free device in accordance with one embodiment; 
         FIG. 37  illustrates a client computing device terminating a video call responsive to receiving an end call request from a hands-free device in accordance with one embodiment; 
         FIG. 38  is a block diagram illustrating an exemplary computer system which may be used in some embodiments; and 
         FIG. 39  is a block diagram illustrating an exemplary data processing system which may be used in some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation. 
     References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
     In the following description and claims, the terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. “Coupled” is used to indicate that two or more elements, which may or may not be in direct physical or electrical contact with each other, co-operate or interact with each other. “Connected” is used to indicate the establishment of communication between two or more elements that are coupled with each other. 
     Automatically Registering for Online Communication Sessions 
     A method and apparatus for automatically registering a client computing device (“client device”) (e.g., a workstation, a laptop, a palmtop, a mobile phone, a smartphone, a multimedia phone, a tablet, a portable media player, a GPS unit, a gaming system, etc.) for online communication sessions (e.g., P2P video conferencing, P2P instant messaging, etc.) is described. In one embodiment, upon an event at a computing device (e.g., the computing device powering on), the client device automatically begins a registration process for online communication sessions. The automatic registration process includes the client device transmitting an SMS (short message service) message with an identifying token (e.g., its push token) and a client device identifier to an SMS transit device (e.g., an SMS gateway or an SMS aggregator). The identifying token uniquely identifies a client device for online communication session messages (e.g., invite request and accept invite messages), and in one embodiment, is a push token that can contain information that allows a push notification service to locate the client device. The identifying token in the push notification service embodiment is also used as a way of establishing trust that a particular notification is legitimate. In other embodiments, any registry or mapping of client devices to unique tokens may be used to associate identifying tokens with client devices and to provide a trusted method of associating the identity of the client device with a uniquely identified token. The device identifier uniquely identifies the client device and is typically based on one or more hardware identifiers (e.g., a serial number of the device, an ICC-ID (Integrated Circuit Card ID) of a SIM (Subscriber Identity Module) card, etc.). 
     The SMS transit device determines the phone number of the client device (e.g., by examining the header of the SMS message) and transmits an IP (Internet Protocol) message to a registration server with the identifying token, device identifier, and the phone number. The registration server generates a signature based on the identifying token, device identifier, and the phone number, and transmits these to the SMS transit device for delivery to the client device. The SMS transit device transmits an SMS message to the client device including the signature and phone number. The client device then transmits an IP message to the registration server with the signature, device identifier, identifying token, and phone number. 
     The registration server validates the information from the client device and stores an association between the identifying token and the phone number in an online communication session registration data store. Together, the associated pair of the identifying token and the phone number uniquely identify the device in an online communication session network. After the client device has been registered, a user at the client device may initiate and/or accept an invitation for an online communication session (e.g., video chat/conference session, instant messaging session, etc.). In one embodiment, the phone number of a client device is used as the online communication session endpoint identifier of an online communication session. By way of example, a user at a client device may invite other user(s) at other client device(s) to participate in an online communication session using their phone number(s). In some embodiments, the client device does not natively know its own phone number. 
       FIG. 1  is a data flow diagram illustrating registering a client device for online communication sessions according to one embodiment.  FIG. 1  includes the client device  110 , the SMS network  120 , the registration server  140 , and the IP messaging data store  150 . The client device  110  (e.g., a workstation, a laptop, a palmtop, a computing phone, a smartphone, a multimedia phone, a tablet, a portable media player, a GPS unit, a gaming system, etc.) includes the identifying token  115  (which may be a push token in one embodiment). The identifying token  115  uniquely identifies the client device  110  for receiving invitation request and invitation accept (or deny) messages, which will be described in greater detail later herein. The device identifier  117  uniquely identifies the client device and is typically based on one or more hardware identifiers (e.g., a serial number of the device, an ICC-ID (Integrated Circuit Card ID) of a SIM (Subscriber Identity Module) card, etc.). The client device  110  includes the ability to transmit and receive SMS messages as well as the ability to connect and send/receive IP messages. 
     After registering for online communication sessions, the client device  110  can invite and/or accept invitations for online communication sessions. The client device  110  is identified in the online communication sessions through an online communication session endpoint identifier. While in one embodiment the online communication session endpoint identifier is a phone number of the client device  110 , in other embodiments the online communication session endpoint identifier is a different identifier (e.g., a username (e.g., an Apple ID), an email address, a mailing address, a MAC address, or other identifier). 
     The SMS network  120 , which includes the carrier SMSC (Short Message Service Center)  125  and the SMS transit device  130  (e.g., an SMS gateway or an SMS aggregator). The carrier SMSC  125  is computing carrier specific and receives and delivers SMS messages. For example, the carrier SMSC  125  delivers SMS messages sent from the client device  110  to the SMS transit device  130 , and delivers SMS messages sent from the SMS transit device  130  to the client device  110 . The SMS transit device  130  separates the mobile network and the IP network. 
     The registration server  140  registers client devices such as the client device  110  for online communication sessions. Registering a client device for online communication sessions includes associating an identifying token of a device with the phone number of the device (or other online communication session endpoint identifier). The associations between identifying tokens and online communication session end identifiers are stored in the online communication session registration data store  150 . 
     Upon an event occurring at the client device  110  (e.g., the client device powering on, an online communication session application (e.g., a P2P video conferencing application, a P2P instant message application, etc.) launching, etc.), the client device  110  begins a registration process for online communication sessions. In one embodiment the registration process begins automatically (without user interaction) while in other embodiments the registration process begins after a user selects to register the client device for online communication sessions. 
     In embodiments where the phone number of the client device  110  is used as the online communication session endpoint identifier, and is thus to be associated with the identifying token  115  of the client device  110  in the registration data store  150 , the phone number of the client device  110  must be determined. Since the client device  110  does not natively know its own phone number, in some embodiments the phone number of the client device  110  is determined through the client device  110  transmitting an SMS message. For example, at operation  1 , the client device  110  transmits an SMS message with its identifying token  115  and the device identifier  117  to the SMS transit device  130  through the carrier SMSC  125 . In some embodiments, the SMS message is addressed to a phone number, which may be a standard length number or a short code (a type of phone number that is typically significantly shorter than a full telephone number), that is specifically established for online communication session registration. The phone number that the SMS message is addressed to is stored in the client device (e.g., in a carrier bundle). 
     The carrier SMSC  125  receives the SMS message and delivers it to the SMS transit device  130 . The SMS transit device  130  determines the phone number of the client device at operation  2 . For example, the SMS transit device  130  examines the header of the SMS message to determine the phone number of the client device  110 . After determining the phone number, the SMS transit device  130  transmits an IP message to the registration server  140  with the phone number of the client device  110  the identifying token  115 , and the device identifier  117 . This is sometimes referred to as a registration request message. 
     The registration server  140  receives the IP message from the SMS transit device including the phone number of the client device  110 , the identifying token  115 , and the device identifier  117 , and creates a signature. The signature may be based on the phone number of the client device  110 , the identifying token  115 , and/or the device identifier  117 , and is used for validation purposes (which will be described in greater detail later herein). In some embodiments, a random number is also used when generating the signature to account for situations where multiple client devices have the same phone number. The registration server  140  transmits the signature, phone number, device identifier, and the token back to the SMS transit device  130  at operation  5  (e.g., in an IP message). This is sometimes referred to as a registration response message. 
     The SMS transit device  130  receives the signature, phone number, device identifier, and token from the registration server  140  and generates an SMS message with the signature and phone number for the client device  110 . The SMS transit device  130  transmits the SMS message to the client device  110  with the signature and phone number at operation  6  (through the carrier SMSC  125 ). 
     The client device  110  receives and processes the SMS message including storing its phone number. The client device  110  transmits an IP message with its identifying token  115 , device identifier  117 , its phone number, and the signature generated by the registration server to the registration server  140  at operation  7 . This is sometimes referred to as a registration validation request message. 
     Using the signature, the registration server  140  validates the data sent by the client device  110 . For example, the registration server  140  compares the signature sent by the client device  110  with the signature generated during operation  4 . If they match, then the data is validated. Assuming that the data is valid, the registration server  140  stores an association between the identifying token  115  and the phone number of the client device  110  in the online communication session registration data store  150 . 
     In an alternative embodiment, instead of determining the phone number of the client device  110  through transmission of SMS messages, the user of the device is prompted to input the phone number of the client device  110 . In these embodiments, the client device  110  directly transmits the phone number of the client device  110  (as input by the user) and its identifying token  115  to the registration server  140 , which may associate them in the online communication session registration data store  150 . 
       FIG. 5  illustrates an exemplary registration data store  150  according to one embodiment. As illustrated in  FIG. 5 , each of the online communication session identifier records  510  include a identifying token field  520  and a phone number field  525 . In some situations, it is possible for a single phone number to be associated with multiple identifying tokens. For example, different client devices may have the same phone number. In these cases, these different client devices would have different identifying tokens. Thus, when an online communication session invitation is sent for a phone number associated with multiple identifying tokens, an invite will be transmitted each device associated with the identifying token. 
       FIG. 2  is a block diagram illustrating the client device  110  in more detail according to one embodiment.  FIG. 2  will be described with reference to the exemplary embodiment of  FIG. 4 , which is a flow diagram illustrating exemplary operations for registering a client device for online communication sessions. However, it should be understood that the operations of  FIG. 4  can be performed by embodiments other than those discussed with reference to  FIG. 2 , and the embodiments discussed with reference to  FIG. 2  can perform operations different than those discussed with reference to  FIG. 4 . 
     As illustrated in  FIG. 2 , the client device  110  includes the client online communication session registration module (“client registration module”)  210 , the carrier bundle(s)  215 , the push token  115 , the device identifier  117 , the SMS module  220 , and the client online communication session registration data store (“client registration data store”)  230 . The client registration module  210  controls the registration of the client device  110  for online communication sessions. The carrier bundle(s)  215  include settings specific to a carrier including the phone number for the SMS transit device used for registration (e.g., the number for the SMS transit device  130 ) and other settings (e.g., Access Point Name (APN) settings, multimedia messaging service (MMS) settings, etc.). The SMS module  220  transmits and receives SMS messages. The client registration data store  230  stores data related to online communication session registration (e.g., the phone number of the client device  110  once determined). 
     Referring to  FIG. 4 , at block  410 , the client registration module  210  detects or receives an event that triggers online communication session registration. Examples of such events include the client device  110  powering on, a user opening an online communication application (e.g., a P2P video conferencing application, a P2P instant messaging application, etc.), etc. In some embodiments the registration process is performed each time the client device  410  powers on, while in other embodiments the registration process is performed the first time the client device  110  is powered on. Flow moves from block  410  to block  415 . 
     At block  415 , the client registration module  210  determines whether there is a valid identifying token for the client device  110 . If there is not a identifying token, or the identifying token has expired, then flow moves to block  425  where alternative action is taken. For example, in embodiments using push tokens, the client device  110  can initiate a token generation procedure by requesting a push token be generated by a push notification service (which is typically remote from the client device  110 ). The push notification service generates a push token specific to the client device  110  and returns it to the client device  110 . If there is a valid identifying token, then flow moves to block  420  where the client registration module  210  access the identifying token  115 . Flow moves from block  420  to block  428 . 
     At block  428 , the client registration module  210  accesses the device identifier  117 . Flow then moves to block  430 , where the client registration module  210  determines the phone number for the SMS transit device used in the registration process. For example, the client registration module  210  accesses the carrier bundle(s)  215  to determine the phone number of the SMS transit device. The phone number may be a short code or may be a standard length number. In this example, the SMS transit device used in the registration process is the SMS transit device  130 . Flow moves from block  430  to block  435 . 
     At block  435 , an SMS message having the identifying token  115  and the device identifier  117  is transmitted to the determined number (the SMS transit device  130 ). For example, the client registration module  210  requests the SMS module  220  to transmit an SMS message with the identifying token  115  and device identifier  117  to the determined number. The SMS module  220  transmits the SMS message with the identifying token to the determined number. Flow moves from block  435  to block  440 . The SMS message will be received by the carrier SMSC  125 , which delivers it to the SMS transit device  130 . 
     At block  440 , the SMS transit device  130  determines the phone number of the client device  110  based on the received SMS message. For example, the SMS transit device examines the header of the SMS message, which will include the phone number of the sender, which in this case is the client device  110 . Flow then moves to block  445  where the SMS transit device  130  transmits the phone number of the client device  110  the identifying token  115 , and the device identifier  117  to the registration server  140  (e.g., in a secure IP message). Flow moves from block  445  to block  450 . 
       FIG. 3  is a block diagram illustrating the registration server  140  in more detail according to one embodiment.  FIG. 3  will be described with reference to the exemplary embodiment of  FIG. 4 . However, it should be understood that the operations of  FIG. 4  can be performed by embodiments other than those discussed with reference to  FIG. 3 , and the embodiments discussed with reference to  FIG. 3  can perform operations different than those discussed with reference to  FIG. 4 . As illustrated in  FIG. 3 , the registration server  140  includes the server online communication session registration module  305 , which includes the SMS transit interface  310 , the signature generator  315 , the client device interface  325 , the validation module  330 , the validation data store  335 , and the association module  340 . The SMS transit interface  310  receives and sends messages to the SMS transit device  130 . For example, the SMS transit interface  310  receives phone number, identifying token, and device identifier tuples from the SMS transit interface  310 , and transmits phone number, identifying token, device identifier and signature tuples (sometimes referred to as “validation tuples”) to the SMS transit interface  310 . The client device interface  325  receives and may transmit messages to client devices. For example, the client device interface  325  receives validation tuples from client devices. 
     Referring back to  FIG. 4 , at block  450 , the signature generator  310  generates a signature for the phone number, identifying token, and device identifier tuple it received from the SMS transit device  130 . The signature will be used to validate the pairing of the phone number and the identifying token prior to storing the pair in the registration data store  150 . In some embodiments the signature is based on the phone number, identifying token, and/or device identifier (e.g., a cryptographic hash is applied to phone number, identifying token, and/or device identifier, or some portion thereof, to generate the signature). In some embodiments, the signature is also based on a random number to account for situations where multiple client devices have the same phone number. The signature generator  310  stores the signature and optionally the phone number, identifying token, and/or device identifier in the validation data store  325 . Flow then moves to block  455 , where the SMS transit interface  310  transmits the signature, phone number, device identifier, and identifying token to the SMS transit device  130 . Flow moves from block  455  to block  460 . 
     The SMS transit device  130  receives the signature, phone number, and identifying token from the registration server  140 . At block  460 , the SMS transit device transmits an SMS message (through the carrier SMSC  125 ) with the signature and phone number for the client device  110 . Flow next moves to block  465 . 
     At block  465 , the SMS module  220  receives the SMS message with the signature and the phone number and stores the signature and the phone number in the client registration data store  230 . Flow then moves to block  470 , where the client registration module  210  transmits an IP message to the registration server with its phone number, identifying token  115 , device identifier  117 , and signature. Flow then moves to block  475 . 
     The client device interface  325  receives the phone number, identifying token, device identifier, and signature from the client device. The information is passed to the validation module  330  which determines whether the data is valid at block  475 . For example, the same hash function as applied when generating the signature is used on the phone number, identifying token, and/or device identifier received from the client device, and the validation module  330  compares the result with the signature that was previously generated (stored in the validation data store  335 ). If the signatures match, then the data is valid and flow moves to block  480 . 
     At block  480 , the association module  330  of the registration server  140  stores an association of the phone number of the client device and the identifying token of the client device in the registration data store  150 . In some embodiments, the registration server  140  may transmit a registration status message to the client device  110  alerting the client device  110  whether registration was successful. 
     After the client device has been registered, a user at the client device may initiate and/or accept an invitation for an online communication session (e.g., video chat/conference session, instant messaging session, etc.). By way of example, a user at a client device may invite other user(s) at other client device(s) to participate in an online communication session using their phone number(s). In some embodiments, the client device does not natively know its own phone number. While embodiments have described the use of SMS messages during registration, in other embodiments other types of text messaging may be used (e.g., MMS (Multimedia Messaging Service)). 
     Registering Email Addresses for Online Communication Sessions 
     While  FIG. 1  was described in relation to registering a phone number as an online communication session endpoint identifier, in other embodiments an email address is used as an online communication session endpoint identifier.  FIG. 21  illustrates a general network topology used to register a client device for online communication sessions using an email address as an online communication session endpoint identifier. The client devices  2110 A-N use the registration service  2130  to register for online communication sessions. For example, in one embodiment, the user of a client device  2110 A uses the online communication session client  2115  to register an email address for use as an online communication session identifier for online communications over the network  2180  (e.g., the Internet). 
       FIGS. 22A-B  are flow diagrams illustrating exemplary operations for registering an email address as an online communication session endpoint identifier according to one embodiment.  FIGS. 22A-B  will be described with reference to the exemplary embodiment illustrated in  FIG. 21 . However, it should be understood that the operations of  FIGS. 22A-B  can be performed by embodiments other than those discussed with reference to  FIG. 21 , and the embodiments discussed with reference to  FIG. 21  can perform operations different than those discussed with reference to  FIGS. 22A-B . 
     At operation  2210 , the registration service  2130  receives an authentication request from the client device  2110 A. For example, with reference to  FIG. 23 , which describes exemplary operations for a user providing initialization information, at operation  2310 , the online communication session application  2115  is started on the client device  2110 A. Flow then moves to operation  2315  and the client device  2110 A receives input from the user including a user ID and password and one or more email address to register for use as online communication session endpoint identifier(s). Flow then moves to operation  2320  and the client device  2110 A transmits the user ID and password to the registration service  2130 . 
     Although the client device  2110 A is registering an email address as an online communication session endpoint identifier and may not include phone functionality, it may send an online communication session invitation using a phone number instead of an email address. In addition to receiving a user ID, password, and one or more email addresses to register, in some embodiments the user can also provide information regarding what country and/or region they are currently located so that a corresponding country code and/or region code can be used if the user initiates an online communication session to a phone number that does not include a country code and/or region code. For example, in the United States, a local telephone call can be placed by using 7 digits (thus the country code and area code are not required). The underlying telephone system automatically determines the country and area code and completes the call. However, in cases where the client device  2110 A does not include telephone functionality, the client device  2110 A cannot rely on the underlying telephone system to automatically include the country code and/or region code when inviting a user to an online communication session using a telephone number that does not include the country code and/or region code. 
     At operation  2320 , the client device  2110 A receives input from the user regarding what country and/or region (e.g., area code, state, province, city, etc.) they are located in. Flow then moves to operation  2320  where the client device  2320  associates the corresponding country and/or region telephone codes with the online communication session application  2115  for use if the user initiates an online communication session to a phone number that does not include a country code and/or region code. For example, if the user indicates that they are located in the United States and the user invites a user to an online communication session using a 10 digit phone number that does not include the country code, the client device  2110 A automatically adds the country code for the United States to the phone number. 
     With reference back to  FIG. 22A , after receiving the authentication request from the client device  2110 A, an authentication process is performed using the provided username and password. In one embodiment the registration service  2130  performs the authentication process while in another embodiment the user directory service  2160  performs the authentication process. The user directory service  2160  is a centralized service that provides user accounting, authentication, and other services. The user directory service  2160  manages the user records  2165 . In one embodiment, each authenticated user is associated with a user record that includes various information (e.g., one or more of a user ID, password, mailing address, telephone number, name, birthday, country, a list of emails associated with the user (which may also indicate whether the email address is validated), etc.). If authentication is successful, then flow moves to operation  2216 . If authentication fails, then flow moves to operation  2214  and alternative action is taken (e.g., the registration service  2130  transmits an error message to the client device  2110 A that indicates that the username and/or password is not correct). 
     At operation  2216 , the registration service  2130  generates and/or access an online communication session profile associated with the user ID. For example, the registration service  2130  may include an online communication session account server  2140  that manages the online communication session profile records  2150 . In one embodiment, each user that is registering or registered for online communication sessions has a corresponding online communication session profile record. Each online communication session profile record may include a set of one or more email addresses, including their validation status, that are associated with the profile. Each online communication session profile record may also include one or more push tokens that correspond to one or more client devices respectively that are registered for online communication sessions. Each profile record may also include profile credentials which are used to validate certain communications from the client devices. Each profile record may also indicate which client devices (as indicated by push tokens) have registered or are trying to register which email addresses. 
     Flow moves from operation  2216  to operation  2218  and the registration service  2130  transmits an authentication reply to the client device  2110 A that includes the profile ID (e.g., a string that identifies the profile associated with the provided user ID) and the profile credentials. The authentication reply may also indicate that the authentication was successful. Flow then moves to operation  2220  and the registration service  2130  receives an email validation request from the client device  2110 A that includes one or more email addresses to validate, profile ID, profile credentials, and the push token of the client device  2110 A. The email validation request message may also include the device ID of the client device  2110 A. The registration service  2130  then determines whether the profile credentials are valid for the profile ID at operation  2222 . If they are not, then flow moves to operation  2224  and alternative action is taken (e.g., the registration service  2130  transmits an error message to the client device  2110 A). If they profile credentials are valid, then flow moves to operation  2223 . At operation  2223 , the registration service  2130  associates the push token with the profile. For example, the online communication session account server  2140  stores the push token in the profile record for the user. 
     Flow then moves to operation  2226  and the registration service  2130  determines whether the email address is validated. A validated email address is an email address that has been validated as belonging to the user requesting that is requesting it to be registered for use as an online communication session endpoint identifier. The online communication session account server  2140  accesses the user&#39;s profile record  2150  to determine whether the email address is validated. If the profile record does not indicate that the email address is validated, in some embodiments the registration service  2130  transmits an email address validation request to the user directory service  2160  to determine whether the user record  2165  for the user indicates that the email address is validated. If the email address is not validated, then flow moves to operation  2227  and the registration service  2130  causes a validation email message to be sent to the email address that includes a link that when selected (or when entered into an Internet browser) causes the email address to be validated. For example, selection of the link causes an email address validation message to be sent that includes the email address and a validation token that are used to validate the email address. The registration service  2130  may also transmit an email address needs validating message to the client device that indicates that the email address is not validated (and thus needs to be validated) and may also indicate a validation email message was sent to the email address in question. Flow then moves to operation  2410 , which will be described in reference to  FIG. 24 . However, if the email address is validated, then flow moves to operation  2228 . 
     At operation  2228 , the registration service  2130  transmits an email address validated success message to the client device  2228  that indicates that the email address has been validated. Flow then moves to operation  2230  and the registration service  2130  receives an activate email request from the client device  2228  that includes the email address, profile ID, and profile credentials. The registration service  2130  then determines whether the profile credentials are valid for the profile ID at operation  2232 . If they are not, then flow moves to operation  2224  and alternative action is taken (e.g., the registration service  2130  transmits an error message to the client device  2110 A). If they profile credentials are valid, then flow moves to operation  2240 . 
     At operation  2240 , the registration service  2130  generates or accesses email credentials for the email address. For example, in one embodiment, the online communication session account server  2140  stores the email credentials for each validated email address of a user in that user&#39;s profile record  2150 . Flow then moves to operation  2242  and the registration service  2130  transmits an activation success message to the client device  2110 A that includes the email address and the email credentials. 
     Flow moves from operation  2242  to operation  2244  and the registration service  2130  receives a registration request message that includes the email address, the email credentials, the profile ID, the profile credentials, the push token of the client device  2110 A, and the device ID of the client device  2110 A. In one embodiment, the request message is received at the online communication session registration server  2145 . The online communication session registration server manages the online communication session registration data store  2155 . The online communication session registration data store  2155  associates a push token (and optionally the device ID) with the profile that has a set of one or more email addresses as online communication session endpoint identifier(s). Thus, each record in the communication session registration data store  2155  represents that a particular device with a particular push token is using an online communication session profile that has one or more email addresses that can be used to invite a user at that device to an online communication session. Flow moves from operation  2244  to operation  2246 . 
     At operation  2246 , the registration service  2130  (e.g., the online communication session registration server  2145 ) determines whether the profile credentials are valid. If they are not valid, then flow moves to operation  2250  and alternative action is taken (e.g., the registration service  2130  transmits an error message to the client device  2110 A). If they are valid, then flow moves to operation  2248  and the registration service  2130  (e.g., the online communication session registration server  2145 ) determines whether the email address credentials are valid. If they are not, then flow moves to operation  2250 . If they are valid, then flow moves to operation  2252 . 
     At operation  2252 , the registration service  2130  (e.g., the online communication session registration server  2145 ) associates the client device  2110 A with its push token with the profile having the email address and stores the association in the registration data store  2155 . Flow then moves to operation  2254  and the registration service  2130  generates an online communication session account identifier and online communication session credentials and transmits them to the client device  2110 A at operation  2256 . 
     There are different ways to validate email addresses in different embodiments. With reference to  FIG. 24 , which is a flow diagram that illustrates exemplary operations for validating an email address, at operation  2410  the client device  2110 A determines whether it includes an email client that includes an account for an email address that it has tried to register and has not received a positive validation email message. If it does not include such an email client, then flow moves to operation  2440 , otherwise flow moves to operation  2415 . 
     At operation  2415 , the email account is automatically periodically checked for a validation email message (e.g., the validation email message transmitted in operation  2227 ). In one embodiment, the online communication session application  2115  periodically requests the email client  2120  to check for the validation email message (the email client  2120  may poll the email server  2170  to check for the validation email message). The validation email message is identified by a set of one or more criteria including the From: field, the To: field, and a validation token (the validation token may be unique for each email address being validated) that is used to validate the email address. The validation token may be located in the header or the body of the validation email message. If the validation email message is received, then flow moves from operation  2420  to operation  2425 , otherwise flow moves to operation  2435 . 
     At operation  2425 , the validation email message is returned to the online communication session application  2115  and it parses the message to locate the validation token. After locating the validation token, the online communication session application  2115  transmits an email address validation message to the registration service  2130  with the validation token, the email address, the profile ID and profile credentials. Thus in this embodiment, the email address is automatically validated without requiring the user to click on a link or otherwise validate the email address. In one embodiment, after receiving the message and determining that the profile credentials are valid, the registration service  2130  transmits an email validated push message (via the push notification service  640 ) to the device that indicates that the email address has been successfully validated. Thus, flow moves from operation  2425  to operation  2430  and the client device  2110 A waits to receive the email address validated push message. 
     If a validation email message has not been received, then flow moves to operation  2435  where the client device determines whether an email validated push message has been received that indicates that the email address that is trying to be registered has been validated. If such a message is received, then flow moves to operation  2445 , otherwise flow moves back to operation  2415 . 
     At operation  2440  (the client device  2110 A does not include an email client that includes an account for the email address that is being registered), the client device  2110 A waits to receive an email validated push message has been received that indicates that the email address that is trying to be registered has been validated. If such a message is received, then flow moves to operation  2445 , otherwise flow remains at operation  2440 . 
     At operation  2445 , the client device  2110 A displays that the email address has been validated and queries the user to continue with the registration process with that email address. If the client device  2110 A receives input indicating to continue with the registration process, then flow moves to operation  2455  and the client device  2110 A transmits an active email request that includes the email address, the profile ID, and the profile credentials to the registration server. The operations described beginning at operation  2230  of  FIG. 22  are then performed. If the client device  2110 A receives input indicating that the user does not want to continue with the registration process, then flow moves from operation  2450  to operation  2460  and the process exits. 
       FIG. 25  is a flow diagram illustrating exemplary operations performed on the registration service when an email address has been validated according to one embodiment. At operation  2510 , the registration service  2130  receives an email address validated status message that indicates that an email address that is associated with an online communication session profile has been validated. The email address validated status message may have been received as a result of operation  2425 , or may have been received as a result of the email address being validated in a different way (e.g., a user clicking on a validation link in a validation email message that causes the email address to be validated, which may be sent on a different device than the device that is trying to register the email address for use in online communication sessions). 
     Flow then moves to operation  2515  and the registration service  2130  updates the validation state for the email address in the profile records  2150 . Flow then moves to operation  2515  and the registration service  2130  determines whether there are client devices that are associated with the online communication session profile that have asked to validate the email address that have not received an email address validated message. For example, the registration service  2130  accesses the profile record  2150  for the online communication session profile to determine which client devices (e.g., as identified by unique push tokens) have asked to validate the email address and which have not received an email address validation message for that email address. For each such client device, the registration service transmits an email validated push message to that client device that includes the profile ID, profile credentials, and the email address that has been validated at operation  2525 . The email validated push message may also include a status update to indicate that the email address has been validated. If there are no devices that have asked to validate the email address that have not received an email address validated message, then flow moves to operation  2530  and the process exits. 
     Establishing Online Communication Sessions 
     As illustrated in  FIG. 6 , a general network topology implemented in one embodiment can include a number of client devices A-N,  670 A-N respectively, communicating with one another and with one or more services  610 ,  620 ,  630 ,  640 , and  650  over a network  660 . Although illustrated as a single network cloud, the network  660  can include a variety of different components including public networks such as the Internet and private networks such as local Wi-Fi networks (e.g., 802.11n home wireless networks or wireless hotspots), local area Ethernet networks, cellular data networks (e.g., 3G, 4G, Edge, etc.) and WiMAXs networks, to name a few. The client devices  670 A-N may connect to the network  660  over different network links. For example client device  670 A may be connected to a home Wi-Fi network represented by network link  675 A and the client device  670 N may be connected to a 3G network (e.g., Universal Mobile Telecommunications System (“UMTS”), High-Speed Uplink Packet Access (“HSUPA”), etc.) over the network link  675 N. Each of the network links  675 A-N over which the client devices  670 A-N are connected may be coupled to a public network such as the Internet through a gateway and/or NAT (Network Address Translation) device (not shown in  FIG. 6 ), thereby enabling communication between the various client devices  670 A-N over the public network. However, if two client devices are on the same local or private network (e.g., the same Wi-Fi network), then the two devices may communicate directly over that local/private network, bypassing the public network. It should be noted, of course, that the underlying principles of the invention are not limited to any particular set of network types or network topologies. 
     Each of the client devices  670 A-N can communicate with a connection data exchange (CDX) service  610 , an invitation service  620 , a registration service  630 , a push notification service  640 , and a relay service  650 . In one embodiment, the services  610 - 650  can be implemented as software executed across one or more physical computing devices such as servers. 
     In one embodiment, the CDX service  610  operates as a central exchange point for connection data required to establish online communication sessions between two or more client devices. Specifically, one embodiment of the CDX service  610  generates NAT traversal data (sometimes referred to as “Hole Punch” data) in response to client device requests to enable external services and clients to communicate through the NAT of each client device (i.e., to “punch a hole” through the NAT to reach the device). For example, in one embodiment, the CDX service detects the external IP address and port needed to communicate with the client device and provides this information to the client device. In one embodiment, the CDX service also receives and processes lists of client devices generated by the invitation service  620  and efficiently and securely distributes connection data to each of the client devices included on the lists (as described in detail below). 
     Users of the client devices  670 A-N use the invitation service  620  to invite users to participate in collaborative online communication sessions (e.g., P2P video conferencing, P2P instant messaging chats/conference, etc.). For example, a user of the client device  670 A requests an online communication session with one or more users of one or more different client devices by transmitting an invitation request to the invitation service  620  that includes an online communication session endpoint identifier of each of the other users. The online communication session endpoint identifier may be different in different embodiments (e.g., a telephone number, a username (e.g., an Apple ID), an email address, a mailing address, a MAC address, or other identifier). The invitation service  620  reads the online communication session endpoint identifier(s) from the invitation request and performs a lookup in the registration data store  655  to locate the client device(s) that are associated with the online communication session endpoint identifier(s). 
     The client devices  670 A-N use the registration service  630  to register for online communication sessions. For example, in one embodiment, when each of the client devices  670 A-N is powered on and is activated on the network, it causes its identifying token (e.g., its push token) to be associated with an online communication session endpoint identifier. The associations are stored in the registration data store  655 . In one embodiment, the client devices  670 A-N register for participation for online communication session service using the registration service  630  as described with respect to  FIG. 4 , while in other embodiments the registration process occurs differently (e.g., by providing both their push token and their online communication session endpoint identifier). 
     The push notification service  640  uses the push tokens of the client devices  670 A-N to transmit push notifications to the client devices  670 A-N. In one embodiment, the push notifications are used to transmit the invitations for the online communication sessions. The relay service  650  establishes online communication session connections between client devices when the NAT types of the client devices are not compatible or P2P connection establishment has failed between the client devices. 
     In one embodiment, communication between the client devices and the CDX service  610  is established using a relatively lightweight network protocol such as User Datagram Protocol (“UDP”) sockets. As is known by those of skill in the art, UDP socket connections do not require hand-shaking dialogues for guaranteeing packet reliability, ordering, or data integrity and, therefore, do not consume as much packet processing overhead as TCP socket connections. Consequently, UDP&#39;s lightweight, stateless nature is useful for servers that answer small queries from a vast number of clients. Moreover, unlike TCP, UDP is compatible with packet broadcasting (in which packets are sent to all devices on a local network) and multicasting (in which packets are sent to a subset of devices on the local network). As described below, even though UDP may be used, security can be maintained on the CDX service  610  by encrypting NAT traversal data using session keys. 
     In contrast to the low-overhead, lightweight network protocol used by the CDX service  610 , in one embodiment, communication between the client devices  670 A-N and the invitation service  620 , registration service  630 , push notification service  640 , and/or the relay service  650  is established with an inherently secure network protocol such as Hypertext Transfer Protocol Secure (“HTTPS”), which relies on Secure Sockets Layer (“SSL”) or Transport Layer Security (“TLS”) connections. Details associated with these protocols are well known by those of skill in the art. 
       FIG. 7  is a data flow diagram illustrating online communication session establishment between client devices according to one embodiment. In the example of  FIG. 7 , a user at the client device A  710  invites a user at the client device B  720  to an online communication session (e.g., a P2P video conference, a P2P instant messaging system, etc.). In this example, the client device A  710  is sometimes referred to as an initiating client device, the user of the client device B  720  is sometimes referred to as an intended recipient, and the client device B  720  is sometimes referred to as an intended recipient client device. In some embodiments, the online communication session invite is a blind invitation without presence. For example, the user at the client device A  710  does not know whether the user at the client device B  720  is currently online or available to participate in the online communication session. 
     While embodiments described in reference to  FIGS. 6 and 7  are specific to using push tokens and push notifications, other embodiments are not so limited. For example, in other embodiments, any registry or mapping of client devices to unique tokens may be used to associate identifying tokens with client devices and to provide a trusted method of associating the identity of the client device with a uniquely identified token. 
     At operation  1 , the client device A  710  requests its connection data from the connection data exchange  610 . The connection data includes information for client devices to exchange with each other to establish an online communication session (e.g., a P2P session). Connection data includes the IP address of the client device (e.g., the public IP address), the port number of the request, and other information (e.g., priority information, etc.). The connection data exchange  610  determines the connection data of the client device A  710  (e.g., the public/private IP addresses and ports, NAT type of the client device A&#39;s NAT device). At operation  2 , the connection data exchange  610  returns the connection data to the client device A  710 . 
     At operation  3 , the client device A  710  transmits an online communication session invitation request to the invitation service  620  to invite the client device B  720  to an online communication session (e.g., a P2P video conference, a P2P instant messaging session, etc.). In one embodiment, the invitation includes the connection data of client device A  710 , which may include public/private IP addresses and ports for client device A  710  and the NAT type for client device A&#39;s NAT device, and an online communication session endpoint identifier associated with the user at the client device B  720  (e.g., a telephone number of client device B  720 , a username of the user (e.g., an Apple ID), an email address, a mailing address, a MAC address, etc.). The online communication session invitation request can take the form of an HTTPS request and may include a client certificate signed by a pre-specified certificate authority. 
     At operation  4 , the invitation service  620  determines the push token(s) associated with the online communication session endpoint identifier included in the request of operation  3 . For example, the invitation service  620  accesses the registration data store  655  to determine the push token(s) that are associated with the online communication session endpoint identifier. As illustrated in  FIG. 7 , the push token  725  is assigned to the client device B  720  and thus is associated with its online communication session endpoint identifier.  FIG. 10  illustrates an exemplary registration data store  655  according to one embodiment. As illustrated in  FIG. 10 , each of the online communication session identifier records  1010  includes a push token field  1015  and an online communication session identifier field  1020 . As illustrated in  FIG. 10 , the same online communication session identifier may be associated with multiple push tokens. In such a case, multiple invitations will be transmitted (e.g., one per push token). 
     The invitation service  620  transmits a push request message to the push notification service  640 . At operation  5 , the push notification service  640  transmits an online communication session invite request, in the form of a push notification message, to the client device B  720 . The request includes the connection data, the online communication session endpoint identifier, and the push token of the client device A  710  (the push token  715 ). The invite request may also include information specific to the online communication session to provide the user of the client device B  720  with information about the invite (e.g., the name of the person sending the invite (e.g., username, real name, phone number, or some combination thereof), what the invite is for (e.g., a P2P video conference, a P2P instant messaging session, etc.), etc.). 
     The online communication session invite request will be received and displayed on the client device B  720  if it is turned on and operating correctly. The invite request includes a mechanism for the user to accept or decline the invitation (e.g., an accept button and a decline button). The user at the client device A  710  may receive a notification if invite request is denied. Assuming that a user at the client device B  720  accepts the invitation request, at operation  6  the client device B  720  requests its connection data from the connection data exchange  610 . The connection data exchange  610  determines the connection data of the client device B  720  (e.g., the public/private IP addresses and ports, NAT type of the client device B&#39;s NAT device), and at operation  7 , returns the connection data to the client device B  720 . 
     The client device B  720  then transmits an accept message to the invitation service  620  at operation  8 . The accept message includes the client device B&#39;s  720  connection data and includes the push token of the client device A  710 . The accept message may also contain an indication as to whether it is a retry from a previous failed direct P2P connection attempt between the client device A  710  and client device B  720 . The accept message can take the form of an HTTPS message. 
     In some embodiments, the invitation service  620  determines whether a P2P connection between the client device A  710  and the client device B  720  is feasible. At operation  9 , the invitation service  620  determines whether a direct P2P connection between client devices A and B is feasible. For example, in one embodiment, if the accept message received from the client device B  620  indicates that it is a retry from a previous failed direct connection attempt (or a specified number of previous failed direct connection attempts), then the invitation service  620  may conclude that a direct P2P connection is infeasible. To determine feasibility, the invitation service  620  may compare the NAT type data for the client devices A and B to determine if the NAT devices of the client devices A and B will support a direct P2P connection. In one embodiment, the accept message described above does not include an indication of previous failed attempts. Rather, after a failed direct connection attempt, either of the client devices  710 - 720  may transmit a special “relay invitation” request (e.g., in place of the invite request at operation  3  in  FIG. 7 ) indicating that a relay connection is needed. In response, the invitation service may automatically invoke the relay operations described herein (as described below). 
     Certain combinations of NAT types are known to be incompatible for establishing P2P connections. For example, a full cone NAT may be used with any other NAT type except a closed/firewalled NAT to establish a direct P2P connection. By contrast, a symmetric NAT can only be used with a full cone NAT to establish a direct P2P connection. The feasibility of combining various NAT types in one embodiment is set forth in the NAT compatibility table  1110  shown in  FIG. 11 , in which columns represent NAT types of one client device (e.g., client device A  710 ) and rows represent NAT types of the other client device (e.g., client device B  720 ). A “1.0” in a cell indicates that the NAT types in the associated row and column are compatible and a “0.0” indicates that the NAT types are incompatible. 
     If the invitation service  620  determines that a direct P2P connection is feasible, then the invitation service  620  transmits a push request to the push notification service  640  to transmit acceptance of the invitation request. Thus at operation  10 B, the push notification service  640  transmits an online communication session accept message, in the form of a push notification, to the client device A  710 . The accept message includes the connection data, the online communication session endpoint identifier, and the push token of the client device B  720 . The accept message will be displayed on the client device A  710 . Since the client devices A and B have each other&#39;s connection data, the client devices A and B have sufficient information to establish a direct P2P connection. Thus at operation  11 A, the client devices A and B establish a direct P2P connection using the exchanged connection data. The direct P2P connection may be established through known mechanisms (e.g., using Internet Connectivity Establishment (ICE) or other known P2P connectivity mechanisms). 
     If, however, the invitation service  620  determines that a direct P2P connection is infeasible, then it transmits a relay lookup request at operation  10 B to the relay service  650  to determine one or more relay hosts for the client devices A and B to use for the connection. The relay lookup request may contain the networking information for the client devices A and B (e.g., NAT traversal/connection data and/or NAT type data) which is used by the relay service  650  to select appropriate relay hosts for both of the client devices. 
     As illustrated in  FIG. 8 , in one embodiment, the relay service  650  includes a relay lookup module  805 , a multiple relay hosts  815 A-B, and a relay host database  810  containing network information related to each of the relay hosts  815 A-B. While  FIG. 8  illustrates two relay hosts, it should be understood that there may be more or less relay hosts in some embodiments. The invitation service  620  transmits a relay lookup request to the relay lookup module  805 , which queries the relay host database  810  using the network information for the client devices A and B. Upon receiving the database results, the relay lookup module  805  provides a response identifying the selected relay hosts  815 A-B at operation  11 B to the invitation service  620 . 
     In one embodiment, the relay lookup response contains a relay token generated by the relay service  650  and the network addresses (IP addresses/ports) of the selected relay hosts  815 A-B to be used by client devices A and B for the relay connection. In one embodiment, the relay token is associated with the relay session and is used by the relay hosts  815 A-B to authenticate the client devices A and B upon connecting to the relay service  650 . The token may take on various forms including, for example, unique ID relay session ID code, a digital certificate and/or a unique encryption key associated with the relay session. 
     The invitation service  620  transmits a relay response to the client devices A and B indicating that a relay connection will be made. In one embodiment, the relay response to the client device B can include the relay token and the network information for the relay host  815 B. In one embodiment, the response to the client device B can be sent directly (bypassing the push notification service  640 ) because it is being sent in response to the client device B&#39;s invite accept message. The invitation service  620  also transmits a relay response to the client device A, which can include the relay token and the network information for relay host A  815 A. In this instance, the response is pushed to client device A via the push notification service  640 . 
     At operation  12 B, the client device A  710  uses the network information for relay host  815 A to establish a connection with the relay service  650 . Similarly, at operation  13 B, the client device B  720  uses the network information for relay host  815 B to establish a connection with the relay service  650 . In each of these transactions, new holes are opened in any NAT firewalls of the client devices A and B and the NAT traversal/connection data for the client devices A and B may be determined by the relay service  650  and returned to client devices A and B, respectively (e.g., by determining the public IP/port for the devices). In one embodiment, the relay service  650  and the client devices A and B implement the Traversal Using Relay NAT (“TURN”) protocol, which, as understood by those of skill in the art, allows an element behind a NAT or firewall to receive incoming data over TCP or UDP connections. 
     At operation  14 B, the client device A  710  transmits a relay update to the invitation service  620 , which is forwarded to the push notification service and pushed to the client device B  720  at operation  17 B. Similarly, at operation  15 B, the client device B  720  transmits a relay update to the invitation service  620  which is forwarded to the push notification service  620  and pushed to client device A  610  at operation  16 B. The relay update transmitted by the client device A  710  can include the session token, each device&#39;s online communication session endpoint identifier, and the NAT traversal/connection data determined by the relay service  650   
     At operation  18 B and  19 B the client devices A and B, respectively, establish an online communication session connection through the relay service  650 . In one embodiment, the relay connections can be established when client device A  710  sends the NAT traversal/connection data of client device B  720  to the relay service  650 , and vice versa, thereby allowing the relay service to determine the correct path to each peer&#39;s relay host  815 A-B. 
     Using the techniques described above, the invitation service  620  may be implemented as a stateless service, which is inherently scalable and resilient, even in a large-scale system with a vast number of client devices. For example, because the push notification service  640  is inherently capable of locating and pushing content to registered client devices, the invitation service  620  is not required to track the current location of each device. Additionally, because devices can transmit NAT traversal/connection data with requests and responses, the invitation service  620  is never required to maintain any per-connection state information, thereby reducing the storage and processing requirements of the invitation service. Such an implementation is particularly useful in a large-scale system. 
     While  FIG. 7  describes a user at a client device inviting a single user to an online communication session, embodiments are not so limited. For example, in some embodiments, a user at a client device may invite multiple users to an online communication session. For example, the user may transmit a single invite request message to the invitation service with multiple online communication session endpoint identifiers to invite multiple users at different client devices to participate in an online communication session. 
     In some situations, a user may have multiple client devices that are associated with the same online communication session endpoint identifier.  FIG. 26  is a data flow diagram illustrating exemplary operations for managing invitations when a user has multiple client devices that are associated with the same online communication session endpoint identifier. 
     The client device A (operated by the user A)  2610  transmits a request for its connection data from the connection data exchange  610  at operation  2632 . The connection data exchange  610  returns client device A&#39;s connection data at operation  2634 . The client device then transmits an online communication session invitation request to the invitation service  620  with a user ID B to invite the user B to an online communication session (e.g., a P2P video conference, a P2P instant messaging session, a video call, etc.). The invite request includes A&#39;s connection data. 
     The invitation service performs a directory lookup at operation  2638  based on B&#39;s ID included in the invite request message. In this example, the directory lookup operation returns a push token for the client device B 1  and a push token for the client device B 2 . Thus, the client devices B 1  and B 2  are associated with B&#39;s ID. The invitation service  620  then transmits a push request message at operation  2640  to the push notification service  640  to push the invite request messages to the client device B 1   2615  and the client device B 2   2620 . The push notification service  640  transmits an online communication session invite request, in the form of a push notification message, to the client device B 1   2615  at operation  2642  and to the client device B 2   2620  at operation  2644 . Each invite request message includes the connection data of the client device A  2610 , the online communication session endpoint identifier used by user A, and the push token of the client device A  2610 . The invite requests may also include information specific to the online communication session (e.g., the name of the person sending the invite (e.g., username, real name, phone number, or some combination thereof), what the invite is for (e.g., a P2P video conference, a P2P instant messaging session, etc.), etc.). Thus, an online communication session invite request is sent to each of the devices that are associated with the online communication session endpoint identifier included in the original invitation request. 
     In one embodiment, the invitation service  620  transmits a status message to the inviting client device to indicate which client device(s) the invite was transmitted to. Thus, at operation  2646 , the invitation service  620  transmits an invite status update to the client device A  2610  that indicates that an online communication session invite request was sent to the client device B 1   2615  and the client device B 2   2620 . In one embodiment, the client device A  2610  tracks which client devices accept the invitation and keeps the other client devices apprised of the state of the online communication session. 
     In one embodiment, the client device B 1   2615  and the client device B 2   2620  will display an invitation request if they are powered on and capable of receiving the invite request. In the example illustrated in  FIG. 26 , a user at the client device B 1   2615  will be accepting the invitation. Thus at operation  2648  the client device B 1   2615  requests its connection data from the connection data exchange  610 . The connection data exchange  610  determines the connection data of the client device B 1   2615  and at operation  2650  returns it to the client device B 1   2615 . 
     The client device B 1   2615  then transmits an accept message to the invitation service  620  at operation  2652 . The accept message includes the connection data of the client device B 1   2615  and the push token of the client device A  2610 . The accept message may also contain an indication as to whether it is a retry from a previous failed direct P2P connection attempt between the client device A  2610  and the client device B 1   2615 . In addition, the accept message can also include the online communication session endpoint identifiers of A and B and the push token for the client device B  2615 . 
     In some embodiments, after receiving an accept message to an online communication session, the invitation service  620  determines whether a direct P2P connection is feasible. Thus, at operation  2654 , the invitation service  620  performs a direct P2P compatibility check to determine whether a direct P2P connection between the client device A  2610  and the client device B 1   2615  is feasible, in a similar fashion as previously described. If the client devices are compatible for a direct P2P connection, then the operations described in reference to  FIG. 27  (beginning at operation  2710 ) are performed. If the client devices are not compatible for a direct P2P connection, then the operations described in reference to  FIG. 28  (beginning at operation  2810 ) are performed. 
     With reference to  FIG. 27 , which illustrates operations performed when a direct P2P connection is feasible, at operation  2710  the invitation service  620  transmits a push request to the push notification service  640  to transmit acceptance of the invitation by the client device B 1   2615 . At operation  2712 , the push notification service  640  transmits an online communication session accept message, in the form of a push notification, to the client device A  2610 . This accept message includes the connection data and the push token of the client device B 1   2615 , and the online communication session endpoint identifier used by the user B. 
     In one embodiment, sometime after receiving the accept message that indicates that the client device B 1   2615  has accepted the invite, the client device A  2610  informs the client device B 2   2620  that client device A  2620  has accepted the invite. Thus, at operation  2714 , the client device A  2610  transmits an invite update request to the invitation service that includes the online communication session endpoint identifier of user B and indicates that the client device B 1   2615  has accepted the invite. The invite update request may also instruct or indicate to the invitation service  620  which client device associated with the online communication session endpoint identifier of user B should receive the invite update message (in this example, the client device B 2   2620  should receive the invite update message). 
     The invitation service  620  performs a directory lookup  2716  based on the online communication session endpoint identifier of user B to determine the push token of the client device B 2   2620 . After determining the push token, the invitation service transmits a push request at operation  2718  to the push notification service  640  to push the invite update message to the client device B 2   2620 . At operation  2720 , the push notification service  640  transmits an invite update message, in the form of a push notification message, to the client device B 2   2620 . The invite update message indicates that the client device B 1   2615  has accepted the online communication session invitation. The client device B 2   2620  may display the invite update message and may maintain state of the online communication session between the client device A  2610  and the client device B 1   2615  (e.g., the duration of the online communication session, etc.). As will be described in greater detail with reference to  FIG. 30 , in one embodiment, the client device B 2   2620  can transmit a transfer request to cause the online communication session to transfer from the client device B 1   2615  to the client device B 2   2620 . 
     Sometime after receiving the invite accept message in operation  2712 , the client device A  2610  and the client device B 1   2615  establish a direct P2P connection using the exchanged connection data at operation  2722 . The direct P2P connection may be established through known mechanisms (e.g., using Internet Connectivity Establishment (ICE) or other known P2P connectivity mechanisms). It should be understood that the operation  2722  may be performed prior to or during the operations  2714 - 2720 . 
     While  FIG. 26  describes an example where only a single client device accepts the invite message, in some situations multiple client devices may accept an invitation to an online communication session directed to a single user. For example, the client device B 1   2615  and the client device B 2   2620  may accept the invitation in some situations. In one embodiment, the client device A  2610  establishes an online communication session with the first client device it receives an accept message from. The client device A  2610  may cause a cancel message to be sent to the other client device(s) (e.g., the cancel message may be transmitted to the invitation service and then pushed, via the push notification service, to those other client device(s)). Referring back to operation  2654  of  FIG. 26 , if a direct P2P connection is not feasible between the client device A  2610  and client device B 1   2615 , then the operations described in  FIG. 28  are performed.  FIG. 28  is a data flow diagram illustrating exemplary operations that are performed when a direct P2P connection is infeasible. At operation  2810 , the invitation service  620  transmits a relay lookup request  2810  to the relay service  650  to determine a relay host to be used by the client device A  2610  and the client device B 1   2615 . The relay lookup request may contain the networking information for the client devices (e.g., NAT traversal/connection data and/or NAT type data) which is used by the relay service  650  to select appropriate relay hosts for the client devices. As illustrated in  FIG. 8 , one embodiment of the relay service  650  includes a plurality of relay hosts  815 A-B and a relay host database  810  containing network information related to each of the relay hosts. For example, the invitation service  620  transmits a relay lookup request to a relay service  650 , which queries the relay host database  810  using the network information for the client devices. Upon receiving the database lookup results, the relay service  650  provides a relay lookup response at operation  1201  identifying the selected relay hosts  815 A-B. In one embodiment, the relay lookup response contains a relay token generated by the relay service  650  and the network addresses (IP addresses/ports) of the relay hosts  815 A-B to be used by the client devices for the relay connection. In one embodiment, the relay token is associated with the relay session and is used by the relay hosts  815 A-B to authenticate the client device A  2610  and the client device B 1   2615  upon connecting to the relay service  650 . The token may take on various forms including, for example, unique ID relay session ID code, a digital certificate and/or a unique encryption key associated with the relay session. 
     The invitation service  620  then transmits a relay response to the client device B 1   2615  at operation  2814  that contains an indication that a relay connection will be made. In one embodiment, the relay response can include the relay token and the network information for the relay host selected for the client device B 1   2615 . In one embodiment, the relay response can be sent directly to the client device B 1   2615  (bypassing the push notification service  640 ). The invitation service  620  also transmits a relay response to the client device A  2610  at operation  2816  that includes the relay token and the network information for the relay host selected for the client device A  2610 . In some embodiments, the relay response is pushed to mobile device A via the push notification service  640 . 
     At operation  2818 , the client device A  2610  then transmits an invite update request to the invitation service  620  that includes the online communication session endpoint identifier of user B and indicates that the client device B 1   2615  has accepted the invite. The invite update request may also instruct or indicate to the invitation service  620  which client device associated with the online communication session endpoint identifier of user B should receive the invite update message (in this example, the client device B 2   2620  should receive the invite update message). 
     The invitation service  620  performs a directory lookup  2820  based on the online communication session endpoint identifier of user B to determine the push token of the client device B 2   2620 . After determining the push token, the invitation service transmits a push request at operation  2822  to the push notification service  640  to push the invite update message to the client device B 2   2620 . At operation  2824 , the push notification service  640  transmits an invite update message, in the form of a push notification message, to the client device B 2   2620 . The invite update message indicates that the client device B 1   2615  has accepted the online communication session invitation. The client device B 2   2620  may display the invite update message and may maintain state of the online communication session between the client device A  2610  and the client device B 1   2615  (e.g., the duration of the online communication session, etc.). In one embodiment, the client device B 2   2620  can transmit a transfer request to cause the online communication session to transfer from the client device B 1   2615  to the client device B 2   2620 . 
     At operation  2826 , the client device A  2610  uses the network information for its selected relay host to establish a connection with the relay service  650 . Similarly, at operation  2828 , the client device B 1   2620  uses the network information for its selected relay host to establish a connection with the relay service  650 . In each of these operations, new holes can be opened in any NAT firewalls of the client devices and the NAT traversal/connection data for the client devices may be determined by the relay service  650  and returned to them (e.g., by determining the public IP/port of the client devices). In one embodiment, the relay service  650  and the client device A  2610  and the client device B 1   2615  implement the Traversal Using Relay NAT (“TURN”) protocol which, as understood by those of skill in the art, allows an element behind a NAT or firewall to receive incoming data over TCP or UDP connections. 
     At operation  2830 , the client device A  2610  transmits a relay update to the invitation service  620  which is forwarded to the push notification service at operation  2832  and pushed to the client device B 1   2615  at operation  2834 . Similarly, at operation  2836  the client device B 1   2615  transmits a relay update to the invitation service  620  which is forwarded to the push notification service  640  at operation  2838  and pushed to the client device A  2610  at operation  2840 . The relay update message transmitted by the client device A  2610  can include the relay token, each online communication session identifier, and the NAT traversal/connection data determined by the relay service  650  at operations  2826  and  2828 . In one embodiment, the relay update operations are performed since one or more of the client device&#39;s NAT information may have changed. Finally, at operations  2842  and  2844 , the client device A  2610  and the client device B 1   2620  respectively establish a P2P connection through the relay service  650 . In one embodiment, the relay connections can be established responsive to the client device A  2610  transmitting the NAT traversal/connection data of the client device B 1   2615  to the relay service  650 , and vice versa, thereby allowing the relay service  650  to determine the correct path to each peer&#39;s relay host. 
       FIG. 29  is a data flow diagram that illustrates exemplary operations performed when an online communication session ends according to one embodiment. At operation  2910 , the online communication session between the client device A  2610  and the client device B 1   2615  has ended. For example, either the client device A  2610  or the client device B 1   2615  has terminated the online communication session (or the online communication session otherwise has been terminated). The online communication session may have been through a direct P2P connection or through a relay. 
     Sometime after the online communication session has ended, at operation  2912 , the client device A  2610  transmits an online communication session update request to the invitation service  620 . The online communication session update is sent to notify the client device B 2   2620 , which was not part of the online communication session, of the termination of the online communication session. The online communication session update request may include user B&#39;s online communication session identifier and may instruct or indicate to the invitation service  620  which client device associated with user B (e.g., the client device B 2   2620 ) is to receive the update. 
     The invitation service  620  performs a directory lookup operation  2914  based on the online communication session endpoint identifier of user B to determine the push token of the client device B 2   2620 . After determining the push token, the invitation service transmits a push request at operation  2916  to the push notification service  640  to push the update message to the client device B 2   2620 . At operation  2720 , the push notification service  640  transmits an online communication session update message, in the form of a push notification message, to the client device B 2   2620 . The online communication session update message indicates that the online communication session between the client device A  2910  and the client device B 1   2615  has ended. 
       FIG. 30  is a flow diagram illustrating exemplary operations performed to transfer an online communication session from one client device to another client device according to one embodiment. In the example illustrated in  FIG. 30 , it is assumed that each of the client devices B 1   2615  and B 2   2620  received an invitation to an online communication session originated by client device A  2610  (they each share the online communication session endpoint identifier that was used in the invitation) and the client device B 1   2615  accepted and established an online communication session with the client device A  2610  (as described in  FIGS. 26 and 27  or  28 ). In addition, the client device B 2   2620  has received an invite update that indicates that the client device B 1   2615  has accepted the invitation. In the example illustrated in  FIG. 30 , the online communication session will be transferred from the client device B 1   2615  to the client device B 2   2620 . For example, a user at the client device B 2   2620  has indicated that it wants to take over the online communications session between the client devices A  2610  and the client device B 1   2620 . In one embodiment, the online communication session application  2115  displays a state of the online communication session between the client device A  2610  and the client device B 1   2615  that allows a user at the client device B 2   2620  to issue a transfer online communication session request (e.g., through a click or press of a link or virtual button available on the online communication session application  2115  of the client device B 1   2615 ). 
     At operation  3010 , the client device B 2   2620  requests its connection data from the connection data exchange  610  and receives the requested connection data at operation  3012  (if it does not already know its connection data). The client device B 2   2620  then transmits a transfer request message at operation  3014  to the invitation service  620  that includes the push token of the client device A  2610  and the connection data of the client device B 2   2620 . The transfer request message may also include the online communication session endpoint identifiers of A and/or B and/or the push token for the client device A  2610 . 
     The invitation service  620  then transmits a push request to the push notification service  640  at operation  3016  to cause the push notification service  640  to transmit the transfer message, in the form of a push notification, to the client device A  2610 . The invitation service  620  also performs a direct P2P compatibility check at operation  3018  to determine whether a direct P2P connection between the client device A  2610  and the client device B 2   2620  is feasible. For purposes of this example a direct connection is feasible, however it should be understood that an online communication session transfer may also occur in a relay situation. 
     At operation  3020 , the push notification service transmits the transfer request message to the client device A  2610 . The transfer request message may include B&#39;s online communication session endpoint identifier and the connection data for the client device B 2   2620 . The transfer request message also indicates which device (i.e., the client device B 2   2620 ) that is requesting the online communication session transfer (e.g., through a device ID and/or push token of the client device B 2   2620 ). The transfer request message may cause the online communication session application  2115  of the client device A  2610  to display the transfer request, and may allow the user to accept or deny the transfer request. Assuming that the transfer request is accepted, the client device A  2610  establishes a direct P2P connection with the client device B  2620  using the exchanged connection data at operation  3022 . It should be understood that at this point the online communication session between the client device A  2610  and the client device B 1   2615  is active. The client device A  2610  then transmits an online communication session update to the client device B 1   2615  that indicates that the online communication session will transfer to the client device B 2   2620 . In one embodiment, this update message is transmitted on the existing online communication session between the client devices. The client device A  2610  then switches to the online communication session with the client device B 2   2620  at operation  3026  and tears down the online communication session with the client device B 1   2615  at operation  3028 . 
     While embodiments have been described with reference to inviting a single user to an online communication session (which may or may not be associated with multiple client device), in some embodiments multiple users may be invited to an online communication session.  FIG. 31  is a flow diagram illustrating exemplary operations for initiating and establishing an online communication session with multiple users. 
     The client device  3110  requests its connection data from the connection data exchange  610  at operation  3132  and the requested connection data is returned at operation  3134 . At operation  3136 , the client device A  3110  transmits an invitation request to the invitation service  620  that includes the connection data of the client device A  3110 , an online communication session endpoint identifier associated with user B and an online communication session endpoint identifier associated with user C. Thus, a user at the client device A  3110  is inviting multiple users to an online communication session. 
     The invitation service  620  performs a directory lookup operation  3138  to determine the push tokens associated with user B&#39;s online communication session endpoint identifier and user C&#39;s online communication session endpoint identifier. In this example and for purposes of simplicity, the directory lookup returns a result of the client device B  3115  being associated with user B&#39;s online communication session endpoint identifier and the client device C  3120  being associated with user C&#39;s online communication session endpoint identifier. The invitation service  620  then transmits a push request  3140  to the push notification service  640  to request that the push notification service  640  transmit the invitations, in the form of push messages, to the client devices B and C. The push notification service  640  then transmits the invite request to the client device B  3115  at operation  3142  and transmits the invite request to the client device C  3120  at operation  3144 . Each invite request message includes the connection data of the client device A  3110 , the online communication session endpoint identifier used by user A, and the push token of the client device A  3110 . 
     In one embodiment, the invitation service  620  transmits a status message to the inviting client device to indicate which client device(s) the invite was transmitted to. Thus, at operation  3146 , the invitation service  620  transmits an invite status update to the client device A  3110  that indicates that an online communication session invite request was sent to the client device B  3115  and the client device C  3120 . In one embodiment, the client device B  3115  and the client device C  3120  will display an invitation request if they are powered on and capable of receiving the invite request. 
     In the example illustrated in  FIG. 31 , each of the invitations will be accepted. Thus at operation  3148  the client device B  3115  requests its connection data from the connection data exchange  610 . The connection data exchange  610  determines the connection data of the client device B  3115  and at operation  3150  returns it to the client device B  3115 . Similarly, the client device C  3120  requests its connection data from the connection data exchange  610  at operation  3152 . The connection data exchange  610  determines the connection data of the client device C  3120  and at operation  3154  returns it to the client device C  3120 . The client device B  3115  then transmits an accept message to the invitation service  620  at operation  3156 , and the client device C  3120  transmits an accept message to the invitation service  620  at operation  3158 . The invitation service  620  then performs a direct P2P compatibility check  3160  to determine whether a direct P2P connection is feasible between the client device A  3110  and the client device B  3115 , and between the client device A  3110  and the client device C  3120 . For purposes of this example, a direct P2P connection is feasible between the client devices. Thus, using the exchanged connection data, the client device A  3110  and the client device B  3115  establish a direct P2P connection for the online communication session at operation  3162 , and the client device A  3110  and the client device B  3120  establish a direct P2P connection for the online communication session at operation  3164 . In this example, the client device A  3110  essentially acts as the host of the online communication session. Thus, data being transmitted between the client device B  3115  and the client device C  3120  is relayed by the client device A  3110 . In other embodiments, a full mesh of connections is established between the parties. In such an embodiment, another P2P connection would be established between the client device B  3115  and the client device C  3120 . 
     While embodiments described herein describe a mechanism to register client devices for online communication sessions, in some embodiments the registration  140  may implement an API to allow different applications to register online communication session endpoint identifier and push tokens. The API implemented in one embodiment, is an interface implemented by a software component (hereinafter “API implementing software component”) that allows a different software component (hereinafter “API calling software component”) to access and use one or more functions, methods, procedures, data structures, and/or other services provided by the API implementing software component. For example, an API allows a developer of an API calling software component (which may be a third party developer) to leverage specified features provided by an API implementing software component. There may be one API calling software component or there may be more than one such software component. An API can be a source code interface that a computer system or program library provides in order to support requests for services from a software application. An API can be specified in terms of a programming language that can be interpretative or compiled when an application is built, rather than an explicit low level description of how data is laid out in memory. 
     The API defines the language and parameters that API calling software components use when accessing and using specified features of the API implementing software component. For example, an API calling software component accesses the specified features of the API implementing software component through one or more API calls (sometimes referred to as function or method calls) exposed by the API. The API implementing software component may return a value through the API in response to an API call from an API calling software component. While the API defines the syntax and result of an API call (e.g., how to invoke the API call and what the API call does), the API typically does not reveal how the API call accomplishes the function specified by the API call. Various function calls or messages are transferred via the one or more application programming interfaces between the calling software (API calling software component) and an API implementing software component. Transferring the function calls or messages may include issuing, initiating, invoking, calling, receiving, returning, or responding to the function calls or messages. Hence, an API calling software component can transfer a call and an API implementing software component can transfer a call. 
     By way of example, the API implementing software component and the API calling software component may be an operating system, a library, a device driver, an API, an application program, or other software module (it should be understood that the API implementing software component and the API calling software component may be the same or different type of software module from each other). The API calling software component may be a local software component (i.e., on the same data processing system as the API implementing software component) or a remote software component (i.e., on a different data processing system as the API implementing software component) that communicates with the API implementing software component through the API over a network. It should be understood that an API implementing software component may also act as an API calling software component (i.e., it may make API calls to an API exposed by a different API implementing software component) and an API calling software component may also act as an API implementing software component by implementing an API that is exposed to a different API calling software component. 
     The API may allow multiple API calling software components written in different programming languages to communicate with the API implementing software component (thus the API may include features for translating calls and returns between the API implementing software component and the API calling software component); however the API may be implemented in terms of a specific programming language. 
       FIG. 9  illustrates one embodiment of an API architecture which includes an API implementing software component  910  (e.g., an operating system, a library, a device driver, an API, an application program, or other software module) that implements the API  920 . The API  920  specifies one or more functions, methods, classes, objects, protocols, data structures, formats and/or other features of the API implementing software component that may be used by the API calling software component  930 . The API  920  can specify at least one calling convention that specifies how a function in the API implementing software component receives parameters from the API calling software component and how the function returns a result to the API calling software component. The API calling software component  930  (e.g., an operating system, a library, a device driver, an API, an application program, or other software module), makes API calls through the API  920  to access and use the features of the API implementing software component  910  that are specified by the API  920 . The API implementing software component  910  may return a value through the API  920  to the API calling software component  930  in response to an API call. 
     It will be appreciated that the API implementing software component  910  may include additional functions, methods, classes, data structures, and/or other features that are not specified through the API  920  and are not available to the API calling software component  930 . It should be understood that the API calling software component  930  may be on the same system as the API implementing software component  910  or may be located remotely and accesses the API implementing software component  910  using the API  920  over a network. While  FIG. 9  illustrates a single API calling software component  930  interacting with the API  920 , it should be understood that other API calling software components, which may be written in different languages (or the same language) than the API calling software component  930 , may use the API  920 . 
     The API implementing software component  910 , the API  920 , and the API calling software component  930  may be stored in a machine-readable medium, which includes any mechanism for storing information in a form readable by a machine (e.g., a computer or other data processing system). For example, a machine-readable medium includes magnetic disks, optical disks, random access memory; read only memory, flash memory devices, etc. 
     Transitioning Between Circuit Switched Calls and Video Calls 
     In some embodiments, a client device can transition from an established audio only circuit switched call to a video call without significantly interrupting communication between the parties. For example, one party of an established audio only circuit switched call selects to transition to a video call (which includes video frames and audio), which causes a video call initiation message (a form of an online communication session invitation message) to be sent to the other participant(s) of the call. If the other participant(s) accept the video call invitation, a P2P connection will be established between the participant&#39;s client devices. While the P2P connection is being negotiated, the participants are able to communicate through the audio only circuit switched call. After the P2P connection is established and video is communicated between the parties, the client devices transition to the video call. The audio only circuit switched call is then dropped, and the participants are able to communicate through the video call. 
       FIG. 12  illustrates an exemplary client device  1210  and a graphical user interface that is used to transition between circuit switched calls and video calls in accordance with some embodiments. The client device  1210  includes the speaker  1255  (which is used during speakerphone mode), front facing camera  1260  (which captures video used for the video call), microphone  1265  (which captures sound), the receiver/speaker  1270  (which is typically used when a user holds the client device  1210  to their ear during a call), and the display screen  1275  (which is a touch screen in some embodiments). The client device  1210  may also include a headphone/headset jack, a proximity sensor, an ambient light sensor, accelerometer(s), and other components. It should be understood that the architecture of the client device  1210  is exemplary and different architectures that include more or less components may be used in embodiments. 
     As illustrated in  FIG. 12 , the graphical user interface  1205  is currently being displayed on the display screen  1275 . The user of the client device  1210  is currently participating in an audio only phone call (with the phone number (408) 555-1234). The graphical user interface  1205  includes several different options for the user during the call. For example, the client device  1210  performs the following responsive to receiving user input (e.g., tapping or other predefined gestures on the appropriate icon): ends the call when input is applied to the end call icon  1250 , mutes the audio call responsive to input being applied to the mute icon  1220 , displays a numeric keypad (e.g., to add additional phone numbers to the call) responsive to input being applied to the keypad icon  1225 , places the call on speakerphone responsive to input being applied to the speaker icon  1230  (which changes the audio output to the speaker  1255 ), adds a call responsive to input being applied to the add call icon  1235 , places the call on hold responsive to input being applied to the hold icon  1240 , displays the user&#39;s contact list responsive to input being applied to the contacts icon  1245 , and transitions to a video call responsive to input being applied to the video call icon  1215 . 
       FIGS. 17-18  are flow diagrams that illustrate exemplary operations for transitioning between an audio only circuit switched call to a video call according to one embodiment.  FIGS. 17-18  will be described with reference to the exemplary embodiments of  FIGS. 12 ,  13 , and  14 . However, it should be understood that the operations of  FIGS. 17-18  can be performed by embodiments of the invention other than those discussed with reference to  FIGS. 12 ,  13 , and  14 , and the embodiments discussed with reference to  FIGS. 12 ,  13 , and  14  can perform operations different than those discussed with reference to the  FIGS. 17-18 . 
     As illustrated in  FIG. 17 , the client devices  1210  and  1410  are connected through an audio only circuit switched call  1710  (either the user of the client device  1210  or the user of the client device  1410  initiated the call). Thus, the users of the client device  1210  and  1410  can communicate over the established circuit switched audio call. At block  1712 , the client device  1210  receives input to transition to a video call. For example, the user has selected to transition to a video call by tapping or performing another defined gesture on the video call icon  1215 . 
     Flow then moves to block  1714 , where the client device  1210  causes a video call invite message (which is a form of an online communication session invitation request message) to be sent to the client device  1410  (as identified by the phone number of the client device  1410 ). In some embodiments, the online communication session invitation request message is sent using the architecture described in  FIGS. 6 and 7 . Flow then moves to block  1716 . 
     At block  1716 , the client device  1210  determines whether the audio is presently being routed through the speakerphone (e.g., the speaker  1255 ) or through the headphone/headset jack. If it is, then flow moves to block  1720 . If it is not, then flow moves to block  1718  where client device  1210  routes the audio through the speakerphone of the client device  1210  (e.g., the speaker  1255 ) and flow moves to block  1720 . 
     At block  1720 , the client device  1210  displays a video preview of what the front facing camera  1260  is currently capturing to allow the user of the client device  1210  to prepare for the video call (e.g., to properly position the client device  1210  for the video call).  FIG. 13  illustrates the client device  1210  displaying the video preview  1310  that displays video of what the front facing camera  1260  is currently capturing. Although not illustrated in  FIG. 13 , in some embodiments a cancel button is also displayed on the GUI  1305  that allows the user to cancel the video call invitation. Flow moves from block  1720  to block  1722 . 
     At block  1726 , the client device  1410  receives a video call invite message inviting the user of the client device  1410  to a video call. Flow moves from block  1726  to block  1728 . In some embodiments, the client device  1410  has an architecture that is similar to the client device  1210 . For example, as illustrated in  FIG. 14 , the client device  1410  includes the speaker  1455  (which is used during speakerphone mode), front facing camera  1460  (which captures video used for the video call), microphone  1465  (which captures sound), the receiver/speaker  1470  (which is typically used when a user holds the client device  1210  to their ear during a call), and the display screen  1475  (which is a touch screen in some embodiments). The client device  1410  may also include a headphone/headset jack, a proximity sensor, an ambient light sensor, accelerometer(s), and other components. It should be understood that the architecture of the client device  1410  is exemplary and different architectures that include more or less components may be used in embodiments. 
     At block  1728 , the client device  1410  plays one or more audio tones indicating receipt of the message to alert the user of the message. The audio tones may be different in different embodiments (e.g., the audio tones may be similar to call waiting tones used on the client device  1410  (although they are not originated by the carrier associated with the client device  1410 ), the audio tones may be unique and specific for video calls, etc.). In some embodiments, the client device  1410  does not play audio tones indicating receipt of the video call invite message if the client device  1410  is not near the user&#39;s ear (e.g., as indicated by a proximity sensor of the client device  1410 ) and/or if the call is currently on speakerphone mode. Flow moves from block  1728  to block  1730 . 
     At block  1730 , the client device  1410  displays the video call invite message and optionally displays a video preview of what the front facing camera  1460  is currently capturing to allow the user of the client device  1410  to prepare for the video call, and flow moves to block  1732 .  FIG. 14  illustrates the GUI  1405  that displays the video call invite  1440 . As illustrated in  FIG. 14 , the video call invite  1440  includes an accept button  1432 , a deny button  1434 , and the video preview  1430  (which shows what the front facing camera  1460  is currently capturing). Although  FIG. 1410  illustrates the video call invite  1440  including the video preview  1430  (that is, the video preview  1430  is contained within the video call invite  1440 ), in other embodiments the video preview  1430  is located outside and/or is overlapping the video call invite  1440 . The user of the client device  1410  may select the accept button  1432  to accept the video call invite (e.g., by tapping or performing another predefined gesture for input on the accept button  1432 ) and can select the deny button  1434  to deny the video call invite (e.g., by tapping or performing another predefined gesture for input on the deny button  1434 ). 
     At block  1732 , the client device  1410  determines whether input has been received to accept the video call (e.g., whether the user has accepted the video call invite by selecting the accept button  1432 ). If the client device  1410  receives input to accept the video call, then flow moves to block  1734 , otherwise flow moves to block  1736 . At block  1734  the client device  1410  causes a video call accept message to be transmitted to the client device  1210 . In some embodiments, the accept message is transmitted to the client device  1210  using the architecture described in  FIGS. 6 and 7 . Flow then moves to block  1810 . 
     At block  1736 , it is determined whether input has been received to reject the video call request (e.g., whether the user has rejected the video call invite by selecting the deny button  1434 ). If the client device  1410  receives input to deny the video call invitation, then flow moves to block  1738 , otherwise flow moves back to block  1732 . At block  1738 , the client device  1410  causes a video call deny message to be transmitted to the client device  1210 . The client device  1410  may also clear the video call invite  1440  and stop displaying the video preview  1430 . In some embodiments, the video call deny message is transmitted to the client device  1210  using the architecture described in  FIGS. 6 and 7 . 
     At block  1722 , the client device  1210  determines whether it has received a video call accept message from the client device  1410 . If it has, then flow moves to block  1816 , otherwise flow moves to block  1724  where the client device  1210  determines whether it has received a video call deny message from the client device  1410 . If it has, then flow moves to block  1910 , otherwise flow moves back to block  1722 . 
     With reference to  FIG. 18 , at block  1810  (the user at the client device  1410  has accepted the video call invitation), the client device  1410  determines whether audio is presently being routed through the speakerphone (e.g., the speaker  1470 ) or the headset of the client device  1410 . If it is not, then flow moves to block  1812  where the audio route is changed from the speaker  1455  to the speakerphone (e.g., the speaker  1470 ), and flow moves to block  1814 . If the audio is already being routed through the speakerphone or a headset, then flow moves to block  1814 . 
     At block  1814 , the client device  1410  displays a video preview of what the front facing camera  1460  is currently capturing. The operation in block  1814  is performed only if the video preview is not currently being displayed as a result of the operation in block  1730 . Flow moves from block  1814  to block  1820 . 
     At blocks  1818  and  1820 , the client devices  1210  and  1410  establish a P2P connection with each other. The P2P connection may be established through known mechanisms (e.g., using Internet Connectivity Establishment (ICE) or other known P2P connectivity mechanisms). Assuming that the P2P connection is successfully established, flow moves from blocks  1818  and  1820  to blocks  1822  and  1824  respectively, where the client devices  1210  and  1410  begin transmitting video to each other over the P2P connection (the video from the front facing video cameras  1260  and  1460 ). In some embodiments, the video includes both video frames and corresponding audio (captured by the microphones  1265  and  1465  of the client devices  1210  and  1410  respectively), while in other embodiments the video and audio are separate streams communicated across the P2P connection. 
     Flow moves from blocks  1822  and  1824  to blocks  1826  and  1828  respectively. At blocks  1826  and  1828 , the client devices  1210  and  1410  respectively determine whether they have received one or more video frames from their peer. If they have, then flow moves from blocks  1826  and  1828  to blocks  1830  and  1832  respectively. If they have not, then flow remains at blocks  1826  and  1828  until one or more video frames have been received. 
     In some embodiments, the client devices  1210  and  1410  wait to receive video frames from each other for a certain amount of time and if they do not exchange video frames over that time alternative action is taken. For example, in some embodiments the video call is cancelled and a message is displayed on the screens of the client devices  1210  and  1410  that the video call could not be established. The video call may fail to establish for a number of reasons including that bandwidth is insufficient for the video call, the video frames have failed to transmit or be received, etc. While in some embodiments the client devices wait for a single frame of video before proceeding, in other embodiments the client devices wait to receive a number of frames over a given time period (e.g., a flow of video frames) before proceeding. 
     At blocks  1830  and  1832 , the client devices  1210  and  1410  respectively transition to the video call. Transitioning to the video call includes displaying the video that is being received and changing the audio route from the circuit switched audio call to the video call. In some embodiments, the video preview (e.g., the video preview  1310 ) moves to a corner of the screen (and shrinks in size) and the video being received from the peer is revealed. Thus, it should be understood that until the audio route has been changed from the circuit switched audio call to the video call, the participants can communicate through the circuit switched audio call (that is, the circuit switched audio call remains established while the video call is being negotiated). After transitioning to the video call, the circuit switched audio call can be dropped. Thus, flow moves from blocks  1830  and  1832  to blocks  1834  and  1836  respectively where the circuit switched audio call is dropped. 
       FIGS. 15 and 16  illustrate the client devices  1210  and  1410  respectively after they have transitioned to the video call. As illustrated in  FIG. 15 , the client device  1210  displays the video  1510 , which is video of what is being captured by the front facing camera  1460  of the client device  1410 . The client device  1210  also displays the video  1515 , which is video of what is being captured by the front facing camera  1260 . The GUI  1505  also includes the end video button  1520  and the end video and call button  1625 . The end video button  1520  allows the user to end the video call and return to an audio call only. The end video and call button  1525  allows the user to end the video call completely (e.g., to end the conversation with the user at the client device  1410 ). As illustrated in  FIG. 16 , the client device  1410  displays the video  1610 , which is video of what is being captured by the front facing camera  1260  of the client device  1210 . The client device  1410  also displays the video  1615 , which is video of what is being captured by the front facing camera  1460 . The GUI  1605  also includes the end video button  1620  and the end video and call button  1625 . 
       FIG. 19  is a flow diagram illustrating exemplary operations performed on a client device that has received a video call reject message according to one embodiment. At block  1910 , the client device  1210  receives a video call reject message (the user at the client device  1410  has rejected the video call invitation). Flow moves from block  1910  to block  1912  and the client device  1210  displays a video call rejected message and optionally plays one or more audio tones indicating receipt of the video call reject message. Flow then moves to block  1914  where the client device  1210  stops displaying its own video preview. The client device  1210  may also prompt the user to return to the original audio output (e.g., through the speaker  1270 ) if the audio output was previously changed to the speakerphone in block  1718 . 
       FIG. 20  is a flow diagram illustrating exemplary operations performed on a client device for transitioning from a video call to a circuit switched call according to one embodiment. A video call  2010  is established between the client devices  1210  and  1410  (the video call may be established according to mechanisms described in reference to  FIGS. 17 and 18  or may be established without transitioning from a circuit switched audio call). At block  1712 , the client device  1210  receives input to transition to an audio only circuit switched call. For example, with reference to  FIG. 15 , the user of the client device  1210  has selected the end video button  1520  (e.g., by tapping or performing another predefined gesture on the end video button  1520 ). The client device  1210  then transmits a message to the client device  1410  that indicates a transition to an audio only circuit switched call  2014 . 
     The client device  1210  then initiates a circuit switched audio call request to the client device  1410  (e.g., the client device  1210  automatically calls the number of the client device  1410 ). In some embodiments this is performed in the background and does not require user interaction. The call is routed through a number of network elements of the carrier network infrastructure (e.g., base stations, mobile switching centers, etc.). 
     The client device  1410  receives and answers the circuit switched call  2020 . In one embodiment the client device  1410  displays the incoming call request and may play audio tones indicating the incoming call request (e.g., call waiting tones or other tones), and requires user intervention to answer the call. In another embodiment, the client device  1410  automatically answers the call without user intervention (and may or may not play audio tones indicating the incoming call request). After the call is answered, the audio only circuit switched call is established  2030  between the client devices  1210  and  1410 . 
     After the audio only circuit switched call is successfully established, the client devices  1210  and  1410  transition to the audio only call  2032  and  2034  respectively. For example, transitioning to the audio only call includes changing the audio route from the video call to the circuit switched call, stopping displaying the video that is being received, and stopping transmitting video. The client device may also stop displaying the video preview. Thus, it should be understood that while the circuit switched audio only call is being negotiated, users at the client devices  1210  and  1410  can communicate through the video call (that is, the video call remains established while the audio only circuit switched call is being negotiated). After successfully transitioning to the audio only circuit switched call, the client devices  1210  and  1410  end the P2P connection  2040 . The users at the client devices  1210  and  1410  may then communicate through the audio only circuit switched call. 
     While embodiments of the invention have been described in relation to a video call having two participants, embodiments are not so limited as there may be more participants in the video call. In such embodiments, the client device may display multiple video streams from each different participant in the video chat. 
     While embodiments of the invention have been described in relation to a video call having two participants where each participant transmits video, embodiments are not so limited. For example, in some embodiments only a single party may be transmitting video to the other participant(s) and those other participant(s) may only be transmitting audio. In some embodiments each participant may determine whether to suspend transmitting video at any point during the video call. 
     In some embodiments, the quality of the video transmitted during the call is dynamically adjusted based on network conditions. For example, during periods when the network is congested, the bitrate of the video may be lowered. Similarly, during periods when the network is relatively free of congestion, the bitrate of the video may be increased. In some embodiments, if network conditions prevent video from being transmitted, the participant client devices automatically transition to an audio only circuit switched call. Thus, if the bandwidth drops below a certain level, the participant client devices may automatically transition to an audio only circuit switched call (or may prompt the user to transition to an audio only circuit switched call). 
     Hands-Free Services Support Via a Hands-Free Device for IP Video Calls 
     In one embodiment, the client devices include functionality to support interaction with a hands-free device (e.g., a headset, a car kit) over a WPAN (Wireless Personal Area Network) (e.g., Bluetooth, ZigBee, etc.) including support to manage IP video calls with the hands-free unit.  FIG. 32  is a block diagram illustrating a client device interfacing with a hands-free unit to manage IP video calls in accordance with one embodiment. The client device  3210  includes the ability to initiate video calls (e.g., invite one or more recipients to an online communication session that is a video call) and the ability to accept video calls. In some embodiments, the client device  3210  also includes cellular telephony components to make and receive cellular telephone calls and/or access the Internet or other network through a cellular connection. 
     As depicted in  FIG. 32 , the client device  3210  includes the IP video call manager  3250 , the telephony manager  3260 , the audio manager  3275 , and the hands-free manager  3270 . In some embodiments, the client device  3210  also includes the cellular call manager  3255 . The IP video call manager  3250  manages a P2P video call application including establishing an IP P2P video call over the IP network  3235  through the IP video call service  3230  as previously described herein. In one embodiment, the IP video call service  3230  includes one or more of the invitation service  620 , the push notification service  640 , the registration service  630  and/or the registration service  2130 , and the relay service  650 . The cellular call manager  3255  manages the cellular components to make and receive audio only cellular telephone calls over the cellular network  3245  using the cellular audio call service  3240 . 
     The IP video call manager  3250  and the cellular call manager  3255  are coupled with the telephony manager  3260 . The telephony manager  3260  manages the telephony operations for both of the IP video call manager  3250  and the cellular call manager  3255  including tracking the call history (both for video calls and audio only cellular calls) and other information related to the calls. The telephony manager  3260  also interfaces with the hands-free manager  3270  to provide hands-free services via an external hands-free device for IP video calls and cellular calls on behalf of the IP video call manager  3250  and the cellular call manager  3255 . In one embodiment a common message format is used between the IP video call manager  3250 , the cellular call manager  3255 , and the telephony manager  3260 , to provide support for the hands-free services for disparate protocol and call types (IP video call and audio only cellular call). Thus, the telephony manager  3260  provides similar support for hands-free services regardless of whether the hands-free services are for an IP video call or an audio only cellular call. This also prevents the hands-free manager  3270  from the need to understand whether the hands-free services are for an IP video call or for an audio only cellular call such that standard commands that are understandable by the hands-free devices can be used to provide hands-free services for IP video calls as well as for audio only cellular calls. 
     In one embodiment, the telephony manager  3260  also arbitrates between the IP video call manager  3250  and the cellular call manager  3255 . For example, the telephony manager  3260  can cause an IP video call to be placed on hold to switch to an established audio-only cellular call and/or cause an audio-only cellular call to be placed on hold to switch to an IP video call. 
     The hands-free manager  3270  provides support for hands-free processing. In one embodiment, the hands-free manager  3270  implements a Bluetooth protocol stack for connection to Bluetooth compliant hands-free devices such as Bluetooth headset and Bluetooth car kits. In one specific embodiment, the hands-free manager  3270  implements a Bluetooth headset profile (e.g., as defined in the Headset Profile (HSP) 1.2 specification of Dec. 18, 2008) and/or a Bluetooth hands-free profile (e.g., as defined in the Hands-Free Profile 1.5 (HFP 1.5) specification of Nov. 25, 2005). The hands-free manager  3270  allows the hands-free unit  3220  to act as an auditory relay for an IP video call and for an audio only cellular call over the WPAN  3225 , as well as perform other hands-free services. For example, in the case of an IP video call, the audio portion of the call may be routed through the hands-free unit  3220  instead of a speaker of the client device  3210  while the video portion of the call remains being displayed by the client device  3210  (or by an attached display). The hands-free unit  3220  also includes a microphone to capture audio information which is then transmitted to the client computing device  3210 . Thus, a user can use the hands-free unit  3220  to talk and or listen to audio during an IP video call and/or during an audio only cellular call. 
     The hands-free manager  3270  also supports other hands-free services responsive to receiving input from the hands-free unit  3220  including performing one or more of the following for IP video calls and/or audio only cellular calls: allowing a user to answer a call; end a call; place a call on hold; mute a call; increase/decrease volume of a call; transfer audio to the client device; transfer audio to the hands-free unit; place a call; and redial the last call. Thus, a user can use the hands-free unit  3220  to answer an IP video call, end an IP video call, place an IP video call on hold and/or on mute, increase/decrease the volume of an IP video call, transfer audio of the IP video call to be output to a speaker of the client device  3210 , transfer audio from the client device  3210  to the hands-free unit  3220 , place an IP video call, and redial the last IP video call. 
     The IP video call manager  3250 , the cellular call manager  3255 , and the hands-free manager  3270  are also coupled with the audio manager  3275 . The audio manager  3275  routes audio of the IP video calls and the audio only cellular calls through different sources. For example, the audio manager  3275  can cause the audio to be output through a speaker of the client device  3210  suitable for speakerphone mode, through a speaker of the client device  3210  used when a user holds the client device  3210  to their ear during a call, through a headset/headphone jack to a headset or headphone that is plugged into the client device  3210 , and through a peered hands-free unit (such as the hands-free unit  3220 ). 
       FIG. 33  illustrates the client device  3210  receiving an invitation for a video call, causing the hands-free device to ring, receiving an answer indication from the hands-free device, establishing the video call, and routing the audio to the hands-free device in accordance with one embodiment.  FIG. 33  will be described with reference to the exemplary embodiment of  FIG. 32 . However, it should be understood that the operations of  FIG. 33  can be performed by embodiments other than those discussed with reference to  FIG. 32 , and the embodiments discussed with reference to  FIG. 32  can perform operations different than those discussed with reference to  FIG. 33 . 
     At operation  3310 , the IP video call manager  3250  receives an IP video call invitation from another client device that invites the user of the client device  3210  to participate in an IP video call. The IP video call invitation may take the form of the invitation as described previously herein. The IP video call manager  3250  processes the invitation request including causing the invitation to be displayed at operation  3315 . For example, the invitation request may be displayed in a similar way as the exemplary video call invitation  1440  illustrated in  FIG. 14 . 
     In addition, the IP video call manager  3250  generates and transmits a call object  3320  to the telephony manager  3260 . The call object  3320  includes a set of parameters regarding the call. For example, the call object parameters include one or more of a status of the call (e.g., connecting), and call participant identifier (e.g., the phone number, email address, or other online communication session endpoint identifier), a start time, an indication whether it is an outgoing or incoming call, and a call identifier used internally to identify the call. 
     In one embodiment, the call object  3320  is a generic call object that, while the parameters are based on the information from the IP video call invitation, is in a format that is common for both IP video call invitation requests and incoming audio-only cellular calls. Thus, when receiving an incoming audio only cellular call, the cellular call manager  3255  generates a incoming call object of the same format. Thus, from the perspective of the telephony manager  3260 , an IP video call invitation request or an incoming audio only cellular call appears to be same. 
     The telephony manager  3260  stores the information in the call object  3320  as part of a call history structure. The telephony manager  3260  also generates and sends an incoming call message  3322  to the hands-free manager  3270 . In one embodiment, the telephony manager  3260  only sends the incoming call message  3322  if there is a hands-free device such as the hands-free device  3220  peered with the client device  3210  (e.g., the telephony manager  3260  first checks whether there is a hands-free device that is peered with the client device  3210 ). In other embodiments, the telephony manager  3260  sends the incoming call message  33220  to the hands-free manager  3270  regardless of whether there is a peered hands-free device and the hands-free manager  3270  determines whether to drop/ignore the message or process it depending on whether there is a peered hands-free device. For the purposes of  FIG. 33  and subsequent Figures, it is assumed that the hands-free device  3220  is peered to the client computing device  3210 . In one embodiment, the incoming call message  3322  includes the call identifier. 
     Responsive to receiving the incoming call message  3322 , the hands-free manager  3270  causes a series of messages to be transmitted to the hands-free device  3220  alerting it and the user that there is an incoming call. As depicted in  FIG. 33 , the hands-free manager establishes an audio connection  3325  (e.g., a Synchronous Connection Oriented (SCO) link) with the hands-free device  3220  prior to sending a ring tone message  3330  over the established audio connection  3325 . This ring tone message is selected by the client device  3210  and may be customizable by the user of the client device  3210 . In one embodiment, the ring tone message for IP video calls is different than the ring tone for audio only cellular calls. In another embodiment, an audio connection is not established until after the call is answered. In such an embodiment, a ring alert message is sent to the hands-free device  3220  which then determines locally whether to play a ring-tone to alert the user of the incoming call (the ring alert message may also be sent prior to sending the ring tone message  3330 ). In such an embodiment, the ring alert message may be sent multiple times to the hands-free device  3220  until the call is answered or terminated. 
     Sometime after receiving the ring alert message and/or the ring message  3330 , the hands-free device  3220  transmits the answered message  3335  that indicates that a user has answered the call. For example, the user has pressed an answer button on their hands-free device  3220  or otherwise has taken action on the hands-free device  3220  to answer the call. The hands-free manager  3270  receives the answered message  3335  and transmits an answered message  3340  to the telephony manager  3260 . In one embodiment, the answered message  3340  includes the call identifier. Although not illustrated in  FIG. 33 , the hands-free manager  3270  may also transmit an acknowledgement message to the hands-free device  3220  responsive to receiving the answered message  3335 . 
     The telephony manager  3260  determines that the answered call message  3340  belongs to the call indicated in the call object  3320  (e.g., by comparing the call identifier included in the message  3340  with the information stored from the call object  3320 ) and transmits a message  3345  to the IP video call manager  3250  that indicates that the call has been answered. Responsive to receiving this message, the IP video call manager  3250  establishes an IP video call at an operation  3350 . For example, the IP video call manager  3250  causes an IP video call accept message to be sent to an invitation service as described previously herein and a P2P connection is established (either direct or through a relay) with the computing device that transmitted the invitation. 
     Sometime after the IP video call has been established, the IP video call manager  3250  transmits a call object  3355  to the telephony manager  3260 . The call object  3355  includes a similar set of parameters as the call object  3320  with the exception that the status has changed from connecting to connected. In one embodiment, the call object  3355  is a generic call object that is in a format that is common for both established IP video calls and connected audio-only cellular calls. 
     In addition, sometime after the IP video call has been established, audio manager  3275  routes the audio portion of the established IP video call through the hands-free device  3220 . In one embodiment, the IP video call manager  3250  or the telephony manager  3260  requests the audio manager  3275  to route the audio through the hands-free device. The audio manager  3275  may also transmit a message  3360  to the hands-free manager  3270  that indicates that the audio route will be changed to go through the hands-free device  3220 . If an audio connection is not yet established, the hands-free manager  3270  will establish an audio connection with the hands-free device  3220 . Assuming that there is an established audio connection, the audio portion  3365  of the video call is routed to the hands-free device  3220 . Thus, the audio portion of the video call is handled through the hands-free device  3220  while the video portion of the video call is displayed on the client device  3210 . 
       FIG. 34  illustrates the client device  3210  initiating a video call and routing the audio for the established video call through a hands-free device in accordance with one embodiment.  FIG. 34  will be described with reference to the exemplary embodiment of  FIG. 32 . However, it should be understood that the operations of  FIG. 34  can be performed by embodiments other than those discussed with reference to  FIG. 32 , and the embodiments discussed with reference to  FIG. 32  can perform operations different than those discussed with reference to  FIG. 34 . 
     At operation  3410 , the IP video call manager  3250  causes one or more IP video call invitation messages to be sent to other client device(s) to invite user(s) to an IP video call. The IP video call invitation message(s) may take the form of the invitation as described previously herein. The IP video call manager  3250  generates and transmits a call object  3415  to the telephony manager  3260 . Similar to the call object  3320 , the call object  3415  includes a set of parameters regarding the call and is in a generic format. The telephony manager  3260  stores the information in the call object  3415  as part of a call history structure. 
     In one embodiment, the telephony manager  3260  also generates and sends an outgoing call message  3420  to the hands-free manager  3270  that indicates that there is an outgoing call. Responsive to this message, the hands-free manager  3270  establishes an audio connection  3425  with the hands-free device  3220  (if a custom in-band ring tone is to be sent) and then transmits a ring tone message  3430  to the hands-free device  3220 . In other embodiment, the hands-free manager  3270  transmits only a ring tone alert message to the hands-free device  3220  instead of establishing an audio connection and transmitting an in-band ring tone. 
     Sometime after sending the IP video call invitation, the IP video call manager  3250  receives an IP video call accept message  3435 , which may take the form of a video call accept message as previously described herein. After receiving this message, a P2P IP video call is established with the accepting client device at operation  3440  (e.g., a P2P connection (either direct or through a relay) is established with the computing device that accepted the invitation). 
     Sometime after the IP video call has been established, the IP video call manager  3250  transmits a call object  3445  to the telephony manager  3260 . The call object  3445  includes a similar set of parameters as the call object  3415  with the exception that the status has changed from connecting to connected. The call object  3445  is also in a generic format. In addition, sometime after the IP video call has been established, audio manager  3275  routes the audio portion of the established IP video call through the hands-free device  3220 . In one embodiment, the IP video call manager  3250  or the telephony manager  3260  requests the audio manager  3275  to route the audio through the hands-free device. The audio manager  3275  may also transmit a message  3455  to the hands-free manager  3270  that indicates that the audio route will be changed to go through the hands-free device  3220 . If an audio connection is not yet established, the hands-free manager  3270  will establish an audio connection with the hands-free device  3220 . Assuming that there is an established audio connection, the audio portion  3460  of the video call is routed to the hands-free device  3220 . Thus, the audio portion of the video call is handled through the hands-free device  3220  while the video portion of the video call is displayed on the client device  3210 . 
       FIG. 35  illustrates the client device  3210  initiating a video call responsive to receiving a call request from the hands-free device  3220  in accordance with one embodiment.  FIG. 35  will be described with reference to the exemplary embodiment of  FIG. 32 . However, it should be understood that the operations of  FIG. 35  can be performed by embodiments other than those discussed with reference to  FIG. 32 , and the embodiments discussed with reference to  FIG. 32  can perform operations different than those discussed with reference to  FIG. 35 . 
     The hands-free manager  3270  receives a call request  3510  from the hands-free device  3220 . The call request  3510  may be generated in response to a user selecting a phone number or other online communication session endpoint identifier to be called. For example, the user may select a redial button on the hands-free device  3220  which requests that the last call be redialed. The hands-free manager  3270  transmits a call request message  3520  to the telephony manager  3260 . The telephony manager  3260  determines whether the call request message  3520  is requesting a call to an identifier that is associated with a video call (and thus the call request message should be sent to the IP video call manager  3250 ) or associated with a phone number for an audio only cellular call (and thus should be sent to the cellular call manager  3255 ). For example, in case that the call request  3520  is a redial request, the telephony manager  3260  accesses the last dialed call, which can be either an IP video call or an audio only cellular call, to determine where to send the call request. As depicted in  FIG. 35 , the telephony manager sends the call request message  3525  to the IP video call manager  3250 . The call request message  3525  includes the identifier of the requested participant for the video call (e.g., a phone number, an email address, or other online communication session endpoint identifier). Responsive to receiving the call request message  3525 , the IP video call manager  3250  causes an IP video call invitation message to be sent to the indicated participant at operation  3410  as described in  FIG. 34 . The remaining operations depicted in  FIG. 35  are performed as described in reference to  FIG. 34 . Thus, the client device  3210  supports establishing an IP video call as a result of user action at a peered hands-free device. 
       FIG. 36  illustrates the client device  3210  routing audio of an established video call to the hands-free device  3220  in accordance with one embodiment. There is an established IP video call  3610  between the client device  3210  and one or more other client devices. The audio portion of this call is currently being output by a speaker of the client device  3210  or through headphones that are plugged in the client device  3210 . At operation  3615 , the IP video call manager  3250  receives input to transfer the audio to the hands-free device  3220 . For example, a user of the client device  3210  has provided input to the IP video call application to transfer the audio to a peered hands-free device. Responsive to receiving such input, the IP video call manager  3250  sends an audio route request  3620  to the audio manager  3275  to route the audio portion of the video call through the hands-free device  3220 . The audio manager  3275  may transmit a message  3625  to the hands-free manager  3270  that indicates that the audio route will be changed to go through the hands-free device  3220 . If an audio connection is not yet established, the hands-free manager  3270  will establish an audio connection  3630  with the hands-free device  3220 . Assuming that there is an established audio connection, the audio portion  3635  of the video call is routed to the hands-free device  3220 . Thus, after an IP video call is established, the client device  3210  allows the user to transfer the audio to a hands-free device. 
     While  FIG. 36  illustrates transferring audio to a hands-free device responsive to receiving direct input at the client device, in other embodiments the user may cause the audio to be transferred to the hands-free device  3220  through input at the hands-free device  3220 . In such embodiments, the hands-free manager  3270  receives a command from the hands-free device  3220  to transfer the audio. The hands-free manager  3270  then sends the request to the audio manager  3275  which then reroutes the audio. 
     In addition, while  FIG. 36  illustrates transferring audio to a hands-free device, in some embodiments audio can also be transferred from the hands-free device to a speaker (or headphones) of the client device  3210 . This can be initiated at the client device  3210  and/or the hands-free device  3220 . In such embodiments, the audio manager  3275  receives the route audio request (either from the IP video call manager  3250  or the hands-free manager  3270 ) to route the audio to the client device  3210  and acts accordingly. 
       FIG. 37  illustrates the client device  3210  terminating a video call responsive to receiving an end call request from the hands-free device  3220  in accordance with one embodiment. The hands-free manager  3270  receives an end call message  3710  from the hands-free device  3220  responsive to a user selecting to end a call (e.g., an end button was selected on the hands-free device  3220 ) at the hands-free device  3220 . The hands-free manager  3270  transmits the end call request  3715  to the telephony manager  3260 . In one embodiment, the end call request  3715  includes a call identifier to indicate which call to end (in case there are multiple calls). The telephony manager  3260  determines that the call to end is associated with the IP video call manager  3250  and sends the end call message  3720  to the IP video call manager  3250 . Responsive to receiving the end call message  3720 , the IP video call manager  3250  causes the IP video call to be terminated and cause the client device  3210  to disconnect from the P2P connection. Thus, the client device  3210  supports allowing the user to end an IP video call using a peered hands-free device. 
       FIG. 38  is a block diagram illustrating an exemplary computer system which may be used in some embodiments. For example, the exemplary architecture of the computer system  3800  may be included in the client devices  110 ,  1210 ,  1410 ,  2110 ,  2610 ,  3210 , etc. or other computing devices described herein. It should be understood that while  FIG. 38  illustrates various components of a computer system, it is not intended to represent any particular architecture or manner of interconnecting the components as such details are not germane to the present invention. It will be appreciated that other computer systems that have fewer components or more components may also be used. 
     As illustrated in  FIG. 38 , the computer system  3800 , which is a form of a data processing system, includes the bus(es)  3850  which is coupled with the processing system  3820 , power supply  3825 , memory  3830 , and the nonvolatile memory  3840  (e.g., a hard drive, flash memory, Phase-Change Memory (PCM), etc.). The bus(es)  3850  may be connected to each other through various bridges, controllers, and/or adapters as is well known in the art. The processing system  3820  may retrieve instruction(s) from the memory  30  and/or the nonvolatile memory  3840 , and execute the instructions to perform operations as described above. The bus  3850  interconnects the above components together and also interconnects those components to the optional dock  3860 , the display controller &amp; display device  3870 , Input/Output devices  3880  (e.g., NIC (Network Interface Card), a cursor control (e.g., mouse, touchscreen, touchpad, etc.), a keyboard, etc.), and the optional wireless transceiver(s)  3890  (e.g., Bluetooth, WiFi, Infrared, etc.). 
       FIG. 39  is a block diagram illustrating an exemplary data processing system which may be used in some embodiments. For example, the data processing system  3900  may be a handheld computer, a personal digital assistant (PDA), a mobile telephone, a portable gaming system, a portable media player, a tablet or a handheld computing device which may include a mobile telephone, a media player, and/or a gaming system. As another example, the data processing system  3900  may be a network computer or an embedded processing device within another device. 
     According to one embodiment, the exemplary architecture of the data processing system  3900  may be included in the client devices  110 ,  1210 ,  1410 ,  2110 ,  2610 ,  3210 , etc. or other computing devices described herein. The data processing system  3900  includes the processing system  3920 , which may include one or more microprocessors and/or a system on an integrated circuit. The processing system  3920  is coupled with a memory  3910 , a power supply  3925  (which includes one or more batteries) an audio input/output  3940 , a display controller and display device  3960 , optional input/output  3950 , input device(s)  3970 , and wireless transceiver(s)  3930 . It will be appreciated that additional components, not shown in  FIG. 39 , may also be a part of the data processing system  3900  in certain embodiments, and in certain embodiments fewer components than shown in  FIG. 39  may be used. In addition, it will be appreciated that one or more buses, not shown in  FIG. 39 , may be used to interconnect the various components as is well known in the art. 
     The memory  3910  may store data and/or programs for execution by the data processing system  3900 . The audio input/output  3940  may include a microphone and/or a speaker to, for example, play music and/or provide telephony functionality through the speaker and microphone. The display controller and display device  3960  may include a graphical user interface (GUI). The wireless (e.g., RF) transceivers  3930  (e.g., a WiFi transceiver, an infrared transceiver, a Bluetooth transceiver, a wireless cellular telephony transceiver, etc.) may be used to communicate with other data processing systems. The one or more input devices  3970  allow a user to provide input to the system. These input devices may be a keypad, keyboard, touch panel, multi touch panel, etc. The optional other input/output  3950  may be a connector for a dock. 
     The techniques shown in the figures can be implemented using code and data stored and executed on one or more computing devices (e.g., client devices, servers, etc.). Such computing devices stores and transmits (internally and/or with other computing devices over a network) code (composed of software instructions) and data using machine-readable media, such as non-transitory tangible machine-readable media (e.g., machine readable storage media such as magnetic disks; optical disks; read only memory; flash memory devices) and transitory-propagating signals (e.g., electrical, optical, acoustical or other form of propagated signals—such as carrier waves, infrared signals, digital signals, etc.). In addition, such computing devices typically include a set of one or more processors coupled to one or more other components, such as one or more non-transitory tangible machine-readable media (to store code and/or data), user input/output devices (e.g., a keyboard, a touchscreen, and/or a display), and network connections (to transmit code and/or data using transitory propagating signals). The coupling of the set of processors and other components is typically through one or more busses and bridges (also termed as bus controllers). Thus, a non-transitory machine-readable medium of a given computing device typically stores instructions for execution on the set of one or more processors of that computing device. One or more parts of an embodiment may be implemented using different combinations of software, firmware, and/or hardware. 
     While operations have been described herein with reference to automatically validating an email address without requiring a user to click on a link included in a validation email message with respect to validating an email address for use as an online communication session endpoint identifier, embodiments are not so limited. For example, in some embodiments the operations described with reference to automatically validating an email address are performed when an email address needs to be validated for other reasons. For example, a user may be registering for a service that requires an email address to be validated as belonging to that user as a part of the registration process. The user provides the email address to the service and receives a message (e.g., through display of a web page of the service) that indicates that the email address needs to be validated and that a validation email message has been sent or will be sent to the email address that was provided (the validation email message may or may not include a validation link). An application on the client device may automatically check an email account corresponding to the email address for the validation message and when it is located, automatically parse the message to locate a validation token and transmit an email address validation message that includes the email address and the validation token to an email validation server associated with the service to validate the email address. While the flow diagrams in the figures show a particular order of operations performed by certain embodiments, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.). 
     While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20110831
Publication Date: 20140610
Grant Date: 20140610
Priority Date: 20100407
Inventors: SANTAMARIA JUSTIN
WOOD JUSTIN
KLAHN MATTHEW
Assignee: APPLE INC
CPC Classifications: [{"code": "H04L65/1094", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1083", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1104", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1104", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1069", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L61/256", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/403", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M7/0057", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L65/1083", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1073", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/4061", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L65/1089", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1089", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M7/0057", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L65/403", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L65/1073", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/4061", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L61/256", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1069", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 45696682