Patent Publication Number: US-9838241-B2

Title: Discovery of services over infrastructure networks

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/936,830, entitled “Service Discovery System,” filed on Feb. 6, 2014, which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     The present description relates generally to service discovery over a network, including discovery of services over infrastructure networks. 
     BACKGROUND 
     Wi-Fi Direct, WiDi, and other wireless standards enable wireless devices to communicate directly with one another without requiring a wireless access point. The wide adoption of Wi-Fi across multiple different types of user devices, e.g. computers, mobile phones, tablets, etc., makes Wi-Fi well-suited for direct communications with peripheral devices, such as external displays, printers, user input devices, and the like. Furthermore, some of these wireless standards, such as Wi-Fi Direct, provide service discovery at the link layer, such that devices can exchange messages to identify available services before associating (e.g. connecting) with one another. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain features of the subject technology are set forth in the appended claims. However, for purpose of explanation, several embodiments of the subject technology are set forth in the following figures. 
         FIG. 1  illustrates an example network environment in which a system for discovery of services over an infrastructure network may be implemented in accordance with one or more implementations. 
         FIG. 2  illustrates an example network environment in which a system for discovery of services over an infrastructure network may be implemented in accordance with one or more implementations. 
         FIG. 3  illustrates a flow diagram of an example process of an electronic device in accordance with one or more implementations. 
         FIG. 4  illustrates a flow diagram of an example process of an electronic device in accordance with one or more implementations. 
         FIG. 5  illustrates an example extensible markup language (XML) file template for an example service in accordance with one or more implementations. 
         FIG. 6  illustrates an example domain name system text (DNS-TXT) record format for an example service in accordance with one or more implementations. 
         FIG. 7  conceptually illustrates an example electronic system with which one or more implementations of the subject technology can be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below is intended as a description of various configurations of the subject technology and is not intended to represent the only configurations in which the subject technology may be practiced. The appended drawings are incorporated herein and constitute a part of the detailed description. The detailed description includes specific details for the purpose of providing a thorough understanding of the subject technology. However, the subject technology is not limited to the specific details set forth herein and may be practiced using one or more implementations. In one or more instances, structures and components are shown in block diagram form in order to avoid obscuring the concepts of the subject technology. 
     The subject system allows electronic devices in an infrastructure network to discover services, such as direct peer-to-peer services including screencasting, access to peripheral devices, etc., that can be provided over the infrastructure network. Since the electronic devices already have a layer two (link layer) connection with each other over the infrastructure network, pre-association device and/or service discovery protocols, such as those provided by Wi-Fi Direct and the like, are not available to the electronic devices. Thus, the subject system provides a post-association mechanism that allows the electronic devices to query, advertise, discover, and access services, such as direct peer-to-peer services, over the infrastructure network. Furthermore, for electronic devices that only include a wireless network interface, such as Wi-Fi Direct, WiDi, etc., the subject system extends access of services, such as direct peer-to-peer services, to wired networks, such as Ethernet networks, Multimedia over Coax Alliance (MoCA) networks, powerline networks, and the like. In this manner, the subject system allows a user to connect to their home network and access the direct peer-to-peer services provided by devices on their home network. 
       FIG. 1  illustrates an example network environment  100  in which a system for discovery of services over an infrastructure network may be implemented in accordance with one or more implementations. Not all of the depicted components may be used, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made without departing from the spirit or scope of the claims as set forth herein. Additional components, different components, or fewer components may be provided. 
     The network environment  100  includes one or more electronic devices  102 A-E and a set-top box device  120  that are communicably coupled to an infrastructure network  108 . The infrastructure network  108  may include one or more wired and/or wireless network devices, such as wireless access devices, routers, switches, etc. In one or more implementations, the infrastructure network includes wired Ethernet devices, MoCA devices, power line devices, and the like. 
     The set-top box device  120  may be coupled to, and capable of presenting video content on, an output device  124 , such as a television, a monitor, speakers, or any device capable of presenting video content. In one or more implementations, the set-top box device  120  is integrated into the output device  124 . In one or more implementations, the set-top box device  120  communicatively couples the electronic devices  102 A-E to an external network, such as the Internet. The set-top box device  120  may also include and/or be communicatively coupled to a wireless access point which allows the electronic devices  102 A-E to connect to the infrastructure network  108 . In this instance, the set-top box device  120 , or the communicatively coupled wireless access point, assigns internet protocol (IP) addresses to the electronic devices  102 A-E for communicating over the infrastructure network  108 . In one or more implementations, the set-top box device  120  may communicatively couple an additional device (not shown) to the infrastructure network  108  via a wired connection, such as an Ethernet connection, a MoCA connection, and/or a power line connection. 
     The electronic devices  102 A-E can be computing devices such as laptop or desktop computers, smartphones, set-top boxes, peripheral devices, user input devices, tablets, televisions or other displays with one or more processors coupled thereto and/or embedded therein, or other appropriate devices that include wireless network interfaces, such as wireless local area network (WLAN) radios. In the example of  FIG. 1 , the electronic device  102 A is depicted as a tablet device, the electronic device  102 B is depicted as a keyboard device, the electronic device  102 C is depicted as a mouse device, the electronic device  102 D is depicted as a television, and the electronic device  102 E is depicted as a printer device. One or more of the electronic devices  102 A-E, the set-top box device  120  and/or the output device  124  may be and/or may include all or part of the electronic system discussed below with respect to  FIG. 7 . 
     The electronic devices  102 A-E and/or the set-top box device  120  may include appropriate wireless network interfaces for connecting to the infrastructure network  108  and also for establishing direct, e.g. peer-to-peer, network connections, such as Wi-Fi Direct connections, Bluetooth connections, or generally any direct wireless network connections. In  FIG. 1 , the electronic devices  102 A is illustrated as capable of forming peer-to-peer connections with each of the electronic devices  102 B-E. However, the electronic devices  102 B-E and/or the set-top box device  120  may also be capable of forming peer-to-peer connections with one another, e.g. independent of the electronic device  102 A. 
     The peer-to-peer connections may be utilized by the electronic device  102 A to access services provided by the electronic devices  102 B-E, such as user input services provided by the electronic devices  102 B-C, display services provided by the electronic device  102 D, and/or printing services provided by the electronic device  102 E. For example, the electronic device  102 A may deliver audio and/or video streams over the direct connection to the electronic device  102 D, and/or to a device coupled to the electronic device  102 D, such as an adapter, a dongle, etc. In one or more implementations, the electronic device  102 A may transcode the audio and/or video streams prior to delivering the audio and/or video streams to the electronic device  102 D. The electronic device  102 D outputs and/or presents the audio and/or video streams, e.g. to a user. In one or more implementations, the electronic devices  102 A,D also communicate control information over the direct connection, e.g. the electronic device  102 D may communicate user input received via an infra-red remote control to the electronic device  102 A. 
     The electronic devices  102 A-E may rely on a pre-association wireless discovery protocol, such as the pre-association discovery protocol of Wi-Fi Direct, to discover, pair, and form the direct peer-to-peer network connections. Thus, when the electronic devices  102 A-E are associated with one another, such as over the infrastructure network  108 , the pre-association discovery protocol will be unavailable. Furthermore, if the set-top box device  120  communicatively couples an additional device (not shown) to the infrastructure network  108  via a wired connection, such as an Ethernet network interface, a MoCA network interface, a power line network interface (e.g. HomePlug), the additional device may be unable to partake in the pre-association wireless discovery protocol due to its lack of a wireless network interface. 
     The subject system provides a discovery protocol that allows the electronic devices  102 A-E, and/or the set-top box device  120 , when connected to the infrastructure network  108 , to advertise, discover and access services over the infrastructure network  108 . The services may include, for example, direct peer-to-peer services, services typically provided over the infrastructure network  108 , or generally any service that may be provided over a network connection. In one or more implementations, the electronic devices  102 A-E may utilize an architecture and/or technology, such as a universal plug and play (UPnP) device architecture, a domain name system (DNS) architecture, and/or a RUI-H architecture, to advertise and/or discover capable devices, such as DLNA HTML5 RUI capable devices, RVU RUI capable devices, Miracast capable devices, etc., that are on infrastructure connections, e.g. connected to the infrastructure network  108 . In this manner, the subject system allows services, such as direct peer-to-peer services, to be accessed over an infrastructure network  108  and also allows access to the services, such as direct peer-to-peer services, by electronic devices without wireless network interfaces, such as wired Ethernet devices, MoCA devices, power line devices, etc. 
     For example, after connecting to the infrastructure network  108 , the electronic devices  102 A-E may transmit messages over the infrastructure network  108  that advertise, and/or request information regarding, services, such as direct peer-to-peer services, that are available. The advertising messages, and/or messages responding to search requests, may include resource identifiers, such as uniform resource locators (URLs), for accessing service descriptions corresponding to the available services. The electronic devices  102 A-E and/or the set-top box device  120 , may retrieve the service descriptions over the infrastructure network  108  via the resource identifiers. The service descriptions may include attributes related to accessing the available services over the infrastructure network  108 . Example service description messages are discussed further below with respect to  FIGS. 5 and 6 . The electronic devices  102 A-E and/or the set-top box device  120  may then access and/or provide access to, the services over the infrastructure network  108  based at least in part on the attributes of the service descriptions. An example process for discovering and accessing a service, such as a direct peer-to-peer service, over an infrastructure network  108  is discussed further below with respect to  FIG. 3 , and an example process for providing a service, such as a direct peer-to-peer service, over an infrastructure network  108  is discussed further below with respect to  FIG. 4 . 
       FIG. 2  illustrates an example network environment  200  in which a system for discovery of services over infrastructure networks may be implemented in accordance with one or more implementations. Not all of the depicted components may be used, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made without departing from the spirit or scope of the claims as set forth herein. Additional components, different components, or fewer components may be provided. 
     The network environment  200  includes the electronic devices  102 A,D and the infrastructure network  108 . For explanatory purposes, the network environment  200  is illustrated as including the electronic devices  102 A,D which are implementing a direct peer-to-peer screencasting, or audio-video streaming, service, such as Miracast. However, the principles discussed with respect to the network environment  200  can be applied to any other service, such as access to a printing service provided by the electronic device  102 E and/or access to a user input service provided by the electronic devices  102 B,C. 
     The electronic device  102 A includes a content source  202 , such as stored, downloaded, or generated content, a content composer  203 , a buffer  204 , such as a dynamic random access memory (DRAM) screen buffer, an encoder  206 , such as an H.264 encoder, a session controller  208 , and a network interface  210 . The electronic device  102 D includes a renderer  212 , a decoder  216 , such as a H.264 decoder, a session controller  218 , and a network interface  220 . 
     In one or more implementations, the electronic devices  102 A,D may utilize the network interfaces  210 ,  220  to associate directly with one another via a peer-to-peer connection. For example, the electronic devices  102 A,D may perform a pre-association discovery protocol to discover one another and the services that each provides, and may then associate, e.g. connect, with one another. However, in the network environment  200 , the electronic devices  102 A,D are associated with one another via the infrastructure network  108 . Furthermore, the electronic device  102 D may be coupled to the infrastructure network  108  via a wired network connection. Accordingly, pre-association discovery protocols are not available to the electronic devices  102 A,D since they are already associated with one another via the infrastructure network  108 . Thus, the electronic devices  102 A,D may perform one or more of the example processes discussed below with respect to  FIGS. 3 and 4  in order to discover one another and access services, such as direct peer-to-peer services, over the infrastructure network  108 . 
     The session controllers  208 ,  218  of the respective electronic devices  102 A,D transmit control information over the infrastructure network  108  to configure the service, such as using the real-time streaming transport protocol (RTSP) over the transmission control protocol (TCP). The control information may include device capability negotiation and session maintenance information. Once the electronic devices  102 A,D have completed device/service discovery and configuration, the electronic device  102 A begins providing encoded content to the electronic device  102 D over the infrastructure network  108 . 
     For example, the content composer  203  retrieves content from the content source  202  and provides the content to the encoder  206 . The encoder  206  encodes the content in a format suitable for the electronic device  102 D and provides the encoded content to the network interface  210  for transmission to the electronic device  102 D over the infrastructure network  108 , such as using the real-time transport protocol (RTP) over user datagram protocol (UDP). The electronic device  102 D receives the content via the network interface  220 , decodes the content with the decoder  216 , renders the decoded content using the renderer  212 , and outputs the rendered content. The electronic device  102 A that provides the encoded content may be referred to as a source device, and the electronic device  102 D that outputs the decoded content may be referred to as a sink device. 
     In one or more implementations, the electronic device  102 A may generate a user interface, encode the user interface into a video stream, and provide the user interface to the electronic device  102 A. When a user interacts with the user interface output by the electronic device  102 D, the electronic device  102 D provides an indication of the user interaction to the electronic device  102 A, for example via the control information exchanged by the session controllers  208 ,  218 . The electronic device  102 A may update the user interface in view of the user interaction, to provide for remote user interface functionality, and may provide the updated user interface to the electronic device  102 D. In one or more implementations, remote user interface functionality may be provided via Digital Living Network Alliance (DLNA) hypertext markup language 5 (HTML5) remote user interface (RUI), RVU remote user interface (RUI), and/or Miracast technologies. In one or more implementations, Miracast and similar technologies allow the display of an electronic device  102 A, such as a tablet or smart phone, to be mirrored onto a display device, such as the electronic device  102 D and/or a set-top box device  120 , and vice-versa. 
     In one or more implementations, one or more of the content source  202 , the content composer  203 , the buffer  204 , the encoder  206 , the session controllers  208 , 218 , the network interfaces  210 , 220 , the decoder  216 , and/or the renderer  212  may be implemented in software (e.g., subroutines and code) and/or in hardware (e.g., an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Programmable Logic Device (PLD), a controller, a state machine, gated logic, discrete hardware components, or any other suitable devices) and/or a combination of both. Additional features and functions of these modules according to various aspects of the subject technology are further described in the present disclosure. 
       FIG. 3  illustrates a flow diagram of an example process  300  of an electronic device  102 A in accordance with one or more implementations. For explanatory purposes, the example process  300  is primarily described herein with reference to the electronic device  102 A of  FIGS. 1-2 ; however, the example process  300  is not limited to the electronic device  102 A of  FIGS. 1-2 , e.g. the example process  300  may be performed by one or more of the electronic devices  102 B-E and/or the set-top box device  120 , and/or the example process  300  may be performed by one or more components of the electronic device  102 A. Further for explanatory purposes, the blocks of the example process  300  are described herein as occurring in serial, or linearly. However, multiple blocks of the example process  300  may occur in parallel. In addition, the blocks of the example process  300  may be performed a different order than the order shown and/or one or more of the blocks of the example process  300  may not be performed. 
     The electronic device  102 A connects to the infrastructure network  108  ( 302 ). For example, the electronic device  102 A may be assigned an IP address by a router associated with the infrastructure network  108 , such as the set-top box device  120 . After connecting to the infrastructure network  108  ( 302 ), the electronic device  102 A transmits a search request message ( 304 ), such as an M-SEARCH request message for simple service discovery protocol (SSDP) implementations and/or a multicast domain name system (mDNS) message with a DNS pointer record (DNS-PTR) format for a Browse( ) request of zero configuration networking (Zeroconf) implementations. The mDNS message includes an identifier of the service type being searched for, such as “_miracast._tcp” for a Miracast service, and returns any available service instances. The mDNS message is addressed to a multicast address, such as 224.0.0.251 for IPv4 and ff02:fb for IPv6 link-local addressing 
     The M-SEARCH messaging may be bi-directional in that the electronic device  102 A may also receive, and respond to, M-SEARCH messages from the other electronic devices  102 B-E on the infrastructure network  108 . In one or more implementations, the electronic device  102 A transmits an M-SEARCH request message over UDP to the IP version 4 (IPv4) multicast address 239.255.255.250 and UDP port  1900 . The M-SEARCH request message may include the following information: 
     M-SEARCH*HTTP/1.1 
     HOST: 239.255.255.250:1900 
     MAN: “ssdp:discover” 
     MX: 10 
     ST:urn:schemas-upnp-org:service-1-0 
     The electronic device  102 A then receives a discovery message, such as an M-SEARCH response message or one or more DNS-PTR records, that includes a resource identifier of a device that is configured to provide a service over a peer-to-peer connection ( 306 ), such as the electronic device  102 D. In one or more implementations that support Zeroconf, the received DNS-PTR records may include service instance information for each available service instance. The services instances may utilize a naming convention such as “_sessionNN._servicetype._tcp.DNSdomain”. The NN represents each session (or service instance) that the device can support, the servicetype identifies the type of service (such as “_miracast” for Miracast services), and the DNSdomain is the hostname or IP address of the device. The session value may be used to distinguish between different sessions in a multi-session environment to allow support for devices that simultaneously implement sink and multi-session source support. 
     The M-SEARCH response includes a LOCATION header containing an absolute HTTP URL for accessing the service description, e.g. a UPnP description, associated with the electronic device  102 D. In one or more implementations, the host portion of the URL resolves to an IPv4 address, or is an IPv4 address. The M-SEARCH response may include the following information: 
     HTTP/1.1 200 OK 
     LOCATION: http://192.168.1.155:1900/WFDisplayInfo.xml 
     CACHE-CONTROL: max-age=1800 
     EXT: 
     BOOTID.UPNP.ORG: 1 
     SERVER: OS/version UPnP/1.0 product/version 
     ST: urn:schemas-upnp-org:service-1-0 
     USN: uuid:550e8400-e29b-41d4-a716-446655440000 
     urn:schemas-upnp-org:service-1-0 
     In one or more implementations, the electronic device  102 A receives an advertisement message that includes a resource identifier, or an unsolicited discovery message that includes a resource identifier, over the infrastructure network  108  without transmitting a search request. For example, the electronic device  102 A may receive an unsolicited mDNS message (for Zeroconf implementations) and/or an unsolicited multicast HTTP message (for SSDP implementations) from one or more of the electronic devices  102 A-E, such as the electronic device  102 D. 
     The electronic device  102 A then retrieves service description information from the electronic device  102 D utilizing the resource identifier included in the discovery message, such as the location header of the M-SEARCH response, or a service instance (including DNSdomain) identified in a DNS-PTR record ( 308 ). In one or more implementations that utilize Zeroconf, the electronic device  102 A utilizes the Query( ) request to transmit a DNS service (DNS-SVR) record request for the service instance to the electronic device  102 D and then retrieves the DNS-SVR and DNS text (DNS-TXT) records for the service instance from the electronic device  102 D In one or more implementations that utilize SSDP, the electronic device  102 A issues an HTTP GET request to the URL received in the LOCATION header of the M-SEARCH response. An example HTTP GET request may be: 
     GET/WFDisplayInfo.xml HTTP/1.1 
     Host: 192.168.1.155:1900 
     Accept: */* 
     The retrieved service description includes attributes for accessing the service, such as a direct peer-to-peer service, of the electronic device  102 D over the infrastructure network  108 . In one or more implementations supporting Zeroconf, the service description is retrieved in the form of a DNS-SVR record and/or a DNS-TXT record. The DNS-SVR record may include attributes that indicate a port number, such as an RTSP port number, and IP address (or hostname) for accessing the service, such as a direct peer-to-peer service, over the infrastructure network  108 . The DNS-TXT record may include service specific attributes, such as session availability information (is the service/session available for connection), device type information (e.g. primary sink, secondary sink, source), and content protection information, e.g. for a Miracast service. An example DNS-TXT record is discussed further below with respect to  FIG. 6 . 
     In one or more implementations, the DNS-SVR and/or DNS-TXT records published by the electronic device  102 D, e.g. without being requested by the electronic device  102 A. Publishing is the act of registering (advertising) a service to an embedded DNS server running on the device. The DNS server then broadcasts the DNS-SVR and/or DNS-TXT records over the infrastructure network  108  using mDNS messages and then waits for incoming DNS-PTR or DNS-SVR requests to respond to with the local services instances information. 
     In one or more implementations supporting SSDP, the service description is retrieved in the form of an extensible markup language (XML) file. The service description XML file may include attributes for accessing the service, such as a direct peer-to-peer service, over the infrastructure network  108 , such as a port number and/or IP address. The service description XML file may also include service specific attributes, such as the number of sessions that are supported, device type information (e.g. primary sink, secondary sink, source) for each session, port numbers for accessing each session, and content protection information (whether content protection is supported) for each session, e.g. for a Miracast service. An example service description XML file is discussed further below with respect to  FIG. 5 . 
     The electronic device  102 A then accesses the service, such as a direct peer-to-peer service, provided by the electronic device  102 D over the infrastructure network  108  based at least in part on the attributes of the service description ( 310 ). For example, the electronic device  102 A may determine that the electronic device  102 D is has an available session as a sink device, and the electronic device  102 A may transmit an audio and/or video stream over the infrastructure network  108  for presentation on the electronic device  102 D. 
       FIG. 4  illustrates a flow diagram of an example process  400  of an electronic device  102 D in accordance with one or more implementations. For explanatory purposes, the example process  400  is primarily described herein with reference to the electronic device  102 D of  FIGS. 1-2 ; however, the example process  400  is not limited to the electronic device  102 D of  FIGS. 1-2 , e.g. the example process  400  may be performed by one or more of the electronic devices  102 B-E and/or the set-top box device  120 , and/or the example process  400  may be performed by one or more components of the electronic device  102 D. Further for explanatory purposes, the blocks of the example process  400  are described herein as occurring in serial, or linearly. However, multiple blocks of the example process  400  may occur in parallel. In addition, the blocks of the example process  400  may be performed a different order than the order shown and/or one or more of the blocks of the example process  400  may not be performed. 
     The electronic device  102 D connects to the infrastructure network  108  ( 402 ). For example, the electronic device  102 D may be assigned an IP address by a router associated with the infrastructure network  108 , such as the set-top box device  120 . The electronic device  102 D receives a search request from the electronic device  102 A, such as an M-SEARCH request message, or an mDNS message of a Browse( ) request ( 404 ). The electronic device  102 D transmits a response to the search request that includes a resource identifier for accessing a service description, such as an M-SEARCH response message or one or more DNS-PTR records ( 406 ). 
     The electronic device  102 D receives a request from the electronic device  102 A to retrieve the service description via the resource identifier, such as in the form of an HTTP GET request or a Query( ) request ( 408 ). The electronic device  102 D provides the service description to the electronic device  102 A, such as in the form of a service description XML file and/or DNS-SVR and DNS-TXT records ( 410 ). The service description includes one or more attributes for accessing a service, such as a direct peer-to-peer service, provided by the electronic device  102 D, such as an IP address, port number, and availability of the service. 
     The electronic device  102 D then receives, from the electronic device  102 A, a request to access the service, such as a direct peer-to-peer service, over the infrastructure network  108  based at least in part on the attributes of the service description. The electronic device  102 D provides the electronic device  102 A with access to the service over the infrastructure network  108  ( 412 ). 
       FIG. 5  illustrates an example XML file template  510  for an example service in accordance with one or more implementations. Not all of the depicted components may be used, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made without departing from the spirit or scope of the claims as set forth herein. Additional components, different components, or fewer components may be provided. 
     For explanatory purposes, the example XML file template  510  pertains to a screencasting service, such as a Miracast service. However, the example XML file template  510  can be modified to accommodate any other service, such as any other direct peer-to-peer service. As described in the example XML tag description  520 , the XML file template  510  includes a NumberWFDisplaySessionInstances tag that indicates a number of possible sessions supported by the device. The XML file template  510  further includes a WFDisplaySession tag that is used to open and close unique session information. The XML file template  510  further includes a WFDisplaySessionType tag that indicates whether the role of the device in the session corresponds to a source, a primary sink, or a secondary sink. The XML file template  510  further includes a WFDisplayControlPort tag that indicates the RTSP port number for the session. The XML file template  510  further includes a ContentProtectionSupportedVersions tag that lists the supported content protection technology(ies), such as none, HDCP2.0, and/or HDCP2.1. The WFDisplaySessionAvailability tag indicates whether the session is available or not available (e.g. in use). 
       FIG. 6  illustrates an example DNS-TXT record format  610  for an example service in accordance with one or more implementations. Not all of the depicted components may be used, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made without departing from the spirit or scope of the claims as set forth herein. Additional components, different components, or fewer components may be provided. 
     For explanatory purposes, the example DNS-TXT record format  610  pertains to a screencasting service, such as a Miracast service. However, the example DNS-TXT record format  610  can be modified to accommodate any other service, such as any other direct peer-to-peer service. The DNS-TXT record format  610  includes a device type item which indicates whether the role of the device is a source, primary sink or secondary sink, a session availability item which indicates whether the session is available, and a content protection item which indicates which content protection technologies is supported for the service. The content protection value size may vary depending on the supported version and should match the total number of characters in the string “content_protection=&lt;version&gt;”. The DNS-TXT record example  620  illustrates an example DNS-TXT record for a device that is a source device, has an available session, and supports HDCP2.1 for the session. 
       FIG. 7  conceptually illustrates an example electronic system  700  with which one or more implementations of the subject technology can be implemented. The electronic system  700 , for example, may be, or may include, one or more of the electronic devices  102 A-E, and/or the set-top box device  120 , one or more wearable devices, a desktop computer, a laptop computer, a tablet device, a phone, and/or generally any electronic device. Such an electronic system  700  includes various types of computer readable media and interfaces for various other types of computer readable media. The electronic system  700  includes a bus  708 , one or more processing unit(s)  712 , a system memory  704 , a read-only memory (ROM)  710 , a permanent storage device  702 , an input device interface  714 , an output device interface  706 , one or more network interface(s)  716 , and/or subsets and variations thereof. 
     The bus  708  collectively represents all system, peripheral, and chipset buses that communicatively connect the numerous internal devices of the electronic system  700 . In one or more implementations, the bus  708  communicatively connects the one or more processing unit(s)  712  with the ROM  710 , the system memory  704 , and the permanent storage device  702 . From these various memory units, the one or more processing unit(s)  712  retrieves instructions to execute and data to process in order to execute the processes of the subject disclosure. The one or more processing unit(s)  712  can be a single processor or a multi-core processor in different implementations. 
     The ROM  710  stores static data and instructions that are utilized by the one or more processing unit(s)  712  and other modules of the electronic system  700 . The permanent storage device  702 , on the other hand, may be a read-and-write memory device. The permanent storage device  702  may be a non-volatile memory unit that stores instructions and data even when the electronic system  700  is off. In one or more implementations, a mass-storage device (such as a magnetic or optical disk and its corresponding disk drive) may be used as the permanent storage device  702 . 
     In one or more implementations, a removable storage device (such as a floppy disk, flash drive, and its corresponding disk drive) may be used as the permanent storage device  702 . Like the permanent storage device  702 , the system memory  704  may be a read-and-write memory device. However, unlike the permanent storage device  702 , the system memory  704  may be a volatile read-and-write memory, such as random access memory (RAM). The system memory  704  may store one or more of the instructions and/or data that the one or more processing unit(s)  712  may utilize at runtime. In one or more implementations, the processes of the subject disclosure are stored in the system memory  704 , the permanent storage device  702 , and/or the ROM  710 . From these various memory units, the one or more processing unit(s)  712  retrieve instructions to execute and data to process in order to execute the processes of one or more implementations. 
     The bus  708  also connects to the input and output device interfaces  714  and  706 . The input device interface  714  enables a user to communicate information and select commands to the electronic system  700 . Input devices that may be used with the input device interface  714  may include, for example, alphanumeric keyboards and pointing devices (also called “cursor control devices”). The output device interface  706  may enable, for example, the display of images generated by the electronic system  700 . Output devices that may be used with the output device interface  706  may include, for example, printers and display devices, such as a liquid crystal display (LCD), a light emitting diode (LED) display, an organic light emitting diode (OLED) display, a flexible display, a flat panel display, a solid state display, a projector, or any other device for outputting information. One or more implementations may include devices that function as both input and output devices, such as a touchscreen. In these implementations, feedback provided to the user can be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. 
     As shown in  FIG. 7 , bus  708  also couples electronic system  700  to one or more networks (not shown) through one or more network interface(s)  716 . The one or more network interface(s) may include Bluetooth interface, a Bluetooth low energy (BLE) interface, a Zigbee interface, an Ethernet interface, a Wi-Fi interface, a MoCA interface, a reduced gigabit media independent interface (RGMII), or generally any interface for connecting to a network. In this manner, electronic system  700  can be a part of one or more networks of computers (such as a local area network (LAN), a personal area network (PAN), a peer-to-peer network (P2P), a wide area network (WAN), or an Intranet, or a network of networks, such as the Internet. Any or all components of electronic system  700  can be used in conjunction with the subject disclosure. 
     Implementations within the scope of the present disclosure can be partially or entirely realized using a tangible computer-readable storage medium (or multiple tangible computer-readable storage media of one or more types) encoding one or more instructions. The tangible computer-readable storage medium also can be non-transitory in nature. 
     The computer-readable storage medium can be any storage medium that can be read, written, or otherwise accessed by a general purpose or special purpose computing device, including any processing electronics and/or processing circuitry capable of executing instructions. For example, without limitation, the computer-readable medium can include any volatile semiconductor memory, such as RAM, DRAM, SRAM, T-RAM, Z-RAM, and TTRAM. The computer-readable medium also can include any non-volatile semiconductor memory, such as ROM, PROM, EPROM, EEPROM, NVRAM, flash, SSD, nvSRAM, FeRAM, FeTRAM, MRAM, PRAM, CBRAM, SONOS, RRAM, NRAM, racetrack memory, FJG, and Millipede memory. 
     Further, the computer-readable storage medium can include any non-semiconductor memory, such as optical disk storage, magnetic disk storage, magnetic tape, other magnetic storage devices, or any other medium capable of storing one or more instructions. In one or more implementations, the tangible computer-readable storage medium can be directly coupled to a computing device, while in other implementations, the tangible computer-readable storage medium can be indirectly coupled to a computing device, e.g., via one or more wired connections, one or more wireless connections, or any combination thereof. 
     Instructions can be directly executable or can be used to develop executable instructions. For example, instructions can be realized as executable or non-executable machine code or as instructions in a high-level language that can be compiled to produce executable or non-executable machine code. Further, instructions also can be realized as or can include data. Computer-executable instructions also can be organized in any format, including routines, subroutines, programs, data structures, objects, modules, applications, applets, functions, etc. As recognized by those of skill in the art, details including, but not limited to, the number, structure, sequence, and organization of instructions can vary significantly without varying the underlying logic, function, processing, and output. 
     While the above discussion primarily refers to microprocessor or multi-core processors that execute software, one or more implementations are performed by one or more integrated circuits, such as application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs). In one or more implementations, such integrated circuits execute instructions that are stored on the circuit itself. 
     Those of skill in the art would appreciate that the various illustrative blocks, modules, elements, components, methods, and algorithms described herein may be implemented as electronic hardware, computer software, or combinations of both. To illustrate this interchangeability of hardware and software, various illustrative blocks, modules, elements, components, methods, and algorithms have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application. Various components and blocks may be arranged differently (e.g., arranged in a different order, or partitioned in a different way) all without departing from the scope of the subject technology. 
     It is understood that any specific order or hierarchy of blocks in the processes disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes may be rearranged, or that all illustrated blocks be performed. Any of the blocks may be performed simultaneously. In one or more implementations, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     As used in this specification and any claims of this application, the terms “access point”, “receiver”, “computer”, “server”, “processor”, and “memory” all refer to electronic or other technological devices. These terms exclude people or groups of people. For the purposes of the specification, the terms “display” or “displaying” means displaying on or by an electronic device. 
     As used herein, the phrase “at least one of” preceding a series of items, with the term “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (e.g., each item). The phrase “at least one of” does not require selection of at least one of each item listed; rather, the phrase allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C. 
     The predicate words “configured to”, “operable to”, and “programmed to” do not imply any particular tangible or intangible modification of a subject, but, rather, are intended to be used interchangeably. In one or more implementations, a processor configured to monitor and control an operation or a component may also mean the processor being programmed to monitor and control the operation or the processor being operable to monitor and control the operation. Likewise, a processor configured to execute code can be construed as a processor programmed to execute code or operable to execute code. 
     Phrases such as an aspect, the aspect, another aspect, some aspects, one or more aspects, an implementation, the implementation, another implementation, some implementations, one or more implementations, an embodiment, the embodiment, another embodiment, some embodiments, one or more embodiments, a configuration, the configuration, another configuration, some configurations, one or more configurations, the subject technology, the disclosure, the present disclosure, other variations thereof and alike are for convenience and do not imply that a disclosure relating to such phrase(s) is essential to the subject technology or that such disclosure applies to all configurations of the subject technology. A disclosure relating to such phrase(s) may apply to all configurations, or one or more configurations. A disclosure relating to such phrase(s) may provide one or more examples. A phrase such as an aspect or some aspects may refer to one or more aspects and vice versa, and this applies similarly to other foregoing phrases. 
     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” or as an “example” is not necessarily to be construed as preferred or advantageous over other embodiments. Furthermore, to the extent that the term “include,” “have,” or the like is used in the description or the claims, such term is intended to be inclusive in a manner similar to the term “comprise” as “comprise” is interpreted when employed as a transitional word in a claim. 
     All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.” 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. Pronouns in the masculine (e.g., his) include the feminine and neuter gender (e.g., her and its) and vice versa. Headings and subheadings, if any, are used for convenience only and do not limit the subject disclosure.