Abstract:
This document describes Toll Free IP (TIP), a business model and its enabling methods to provide no-charge-to-user (“toll-free”) connectivity through IP-based access networks (e.g., public wireless hotspot networks based on IEEE 802.11), which may be operated by different network operators. With TIP, the use of networks to communicate with a toll-free IP destination will be paid by the owner of the toll-free IP destination. A toll-free IP destination can be identified in many ways, e.g., by a toll-free IP address, toll-free Internet Domain Name, a toll-free Universal Resource Identifier or Universal Resource Locator. TIP enables a user to use networks without prior service subscriptions with network or service providers and without any special terminal software or hardware for gaining permission to use a network. It allows users to use more access networks, i.e., larger “footprints”, than any individual network operator or aggregator can provide. With TIP, a service provider can provide services over IP-based access networks without the need to have business arrangements with each individual network operator or aggregator. TIP can also be used to enable other value-added services such as Prepaid IP, Collect IP, Selective Charging, and a single prepaid account across access networks of multiple operators or aggregators and even across wireless LANs (e.g., public hotspots and enterprise wireless LANs) and cellular networks.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority of U.S. provisional application No. 60/528,167 filed on Dec. 9, 2003, entitled “System and Method for Toll-Free Internet Protocol.” 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to providing no-charge-to-user (“toll-free”) connectivity through IP-based access networks which may be operated by different network operators. 
     BACKGROUND 
     IP-based access networks, such as wireless local area networks using IEEE 802.11, are being deployed rapidly worldwide in homes, enterprises, and public “hotpots” (e.g., airports, hotels, café shops, train stations, gas stations, parks, and along streets and highways). Higher-speed and longer-range wireless IP access networks, such as IEEE 802.16, are emerging. 
     Today, users have two basic ways to gain permission to use an IP access network. The first approach requires a user to have a service subscription with an access network or service provider. Before a user is allowed to use an access network, he/she needs to use the protocols, software and access control interfaces and procedures mandated by the network or service provider to communicate his/her identity, credentials, and service requests to a policy decision point (e.g., an authentication and authorization server) in the network, which uses the user&#39;s service subscription information to authenticate the user and authorize his/her use of a particular access network. To use networks of multiple providers, a user needs to maintain a service subscription with each network provider. A service provider can establish roaming agreements with other service or network providers so that its subscribers can use other providers&#39; networks without multiple service subscriptions. This, however, is often hard to do in public hotspot markets, where there are many network and service providers each serving a small footprint. 
     The second existing approach is for the network to request a user to pay for network usage when the user attempts to use the network. It does not require a user to have a service subscription. Instead, a user&#39;s attempts to use the network (e.g., user&#39;s outgoing packets) are intercepted (trapped) by the network. The network redirects the trapped traffic to an AAA (Authentication, Authorization, and Accounting) server, which may be operated by a service provider separate from the access network providers. The AAA server prompts the user to agree to pay for network usage and to provide his/her credit card information before allowing the user to use the network. Different access networks may use different protocols, software, user interfaces, and authentication procedures to control network access (e.g., Web-based approaches, IEEE 802.1x, and proprietary solutions). A user terminal has to be equipped with these different protocols and software, and the user has to deal with these different interfaces and authentication procedures, to be able to use different networks. 
     The typical prior art IP network access system is depicted in  FIG. 1 . An Access Server  101  in the visiting access network  100  being visited by a user  102  receives traffic from the user and determines whether a user&#39;s traffic should be allowed to enter the portion of the network beyond the Access Server  101 . Access Servers are also commonly referred to as Network Access Servers (NAS), Access Gateways, or Access Routers. 
     The Access Server  101  is a critical component in supporting network access control functions such as Authentication, Authorization, and Accounting (AAA). Authentication is a process whereby a network verifies the identity of a user  102  and sometimes a user also verifies the identity of the network. Authorization is a process whereby a network determines whether a user should be allowed to use a network or a network service. Accounting is a process whereby a network collects information on the resources used by a user. 
     In the prior art, when a user  102  wants to use a visiting network  100 , it will first need to first acquire a local IP address from the access network  100  from the access server  101 . The user terminal can acquire a local IP address in any way supported by the access network  100 . A common approach is to use a standard IP auto-configuration protocol such as the Dynamic Host Configuration Protocol (DHCP) defined by the IETF. It will then have to perform user authentication with that network  100 . 
     To perform user authentication, the user will need to use the protocols required by the network to communicate his/her authentication information (e.g., user identity, credentials and his request to use the network) to the network. Such authentication information is typically sent by the user  102  to an Access Server  101  in the network. Today, different networks may use different protocols and procedures for user authentication. For example, a World-Wide Web (WWW) browser can be used as the interface for a user to enter his/her authentication information, which can then be communicated to the network using the Hypertext Transfer Protocol (HTTP) or the Secure HTTP (S-HTTP) defined by the Internet Engineering Task Force (IETF). Alternatively, a user may use a link-layer protocol below the IP layer, such as the Point-to-Point Protocol (PPP), which has authentication packets to carry the authentication information to the network. The IETF PANA Working Group is working on a standard IP-layer protocol for carrying user authentication information between the user and a control entity (e.g., an Access Server) in the network. 
     Upon receiving a user&#39;s authentication information, an Access Server  101  will act as an AAA client to forward the user&#39;s authentication information to local AAA servers  103 . The local AAA  103  servers will authenticate the user and return all the configuration information needed for the Access Server  101  to control network access. If the local AAA servers  103  do not have sufficient information to authenticate the user, they could forward the authentication requests to AAA servers  104  in the user&#39;s home network  105 . An AAA server that forwards requests to remote servers is commonly referred to as an AAA Proxy. 
     Signaling between AAA client and AAA server can use any AAA protocol defined by the IETF. Today, RADIUS (Remote Authentication Dial In User Service) is the most widely deployed AAA protocol for this purpose. DIAMETER is a newer protocol defined by the IETF to overcome some of the limitations of RADIUS. Both RADIUS and DIAMETER are client/server protocols. When RADIUS is used for example, the Access Server will act as the RADIUS client and the AAA servers will act as RADIUS servers. 
     These existing methods belong to the “caller pay” model, in which a user who initiates the network connectivity pays for the use of the network. Accordingly, access by a user to a network will require an authorization process which may vary from network to network, and is time consuming and complicated to complete. There is a need in the art for a simply model for network access in an IP environment. In the telephony realm, Toll-free telephony has been globally successful over circuit-switched Public Switched Telephone Networks (PSTN) for providing a called party pay model that obviates the need for the calling party to have their call services authenticated or authorized. However, the concept of Toll-Free IP (“TIP”) networks has not been well developed in the art. It is therefore an object of the present invention to provide for a system, method and architecture for a TIP network that obviates the need for the party initiating the communication session to follow a suite of procedures necessary to have their service request and network access authorized. 
     SUMMARY 
     The present invention is a new method, system and network architecture that enables a user to gain no-charge-to-user (“toll-free”) access through an IP access network, Toll-Free IP (TIP). With TIP, a user who initiates the network connectivity does not pay for his/her use of the access network. 
     A key concept in our invention is a TIP destination. A TIP destination can be expressed in different forms, including toll-free IP addresses, toll-free Internet Domain Names, toll-free Universal Resource Identifiers (URI) or Universal Resource Locators (URL). To describe our invention, we use toll-free IP address as an illustrative example. However, the methods, systems and architecture described hereing also apply equally to other TIP destination systems. 
     In our invention an IP address is a toll-free IP address, or TIP address, if IP packets carrying this IP address as the destination IP address are allowed to pass through an access network without requiring the senders of the packets to be first authenticated by the access network or service provider. 
     Usage of an access network to communicate with a TIP address is paid by the TIP address owner, called a TIP owner, which is a company or individual that owns the IP addressing space including the TIP address. A user, without any prior arrangement with, and without having to be authenticated by, the access network or service provider, can send IP packets to a TIP address immediately after it establishes wireless or wired connectivity to the access network. 
     A TIP server, a functional entity, is used to maintain TIP address databases and to verify whether an IP address is a TIP address upon request. A TIP server can be centralized or distributed. A company that operates TIP servers is called a TIP administrator. A TIP administrator may also be a network or service provider or aggregator, an ISP, or even an enterprise network. 
     Unlike toll-free telephone numbers that have unique prefixes such as 800 or 888, any IP address can be made a TIP address by registering it as a TIP address with a TIP administrator. With the registration, the owner of the address agrees to pay, according to a policy, for the use of access networks to communicate with this TIP address. A TIP address can be an IP network prefix to allow toll-free access to any IP address inside the network identified by the TIP network prefix. 
     When an access network receives an IP packet with an unauthorized IP source or destination address, the access network sends a TIP Query message to a TIP server to query whether the destination IP address is a TIP address. Responses from the TIP Server are referred to as TIP Response messages. If the destination IP address is not a TIP address, the access network discards the packet. Then, the access network or the user may initiate conventional procedures to authenticate and authorize the user. If the destination address is a TIP address, the access network allows packets between the user and the TIP address to pass through without authenticating the user and his/her terminal. 
     TIP owners do not need direct business relationships with access network or service providers. TIP owners, and access network/service providers establish business relationships with TIP Administrators, which in turn broker network services with TIP owners&#39; demands. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a depiction of a prior art IP network with access control; 
         FIG. 2  is a depiction of one embodiment Toll-free IP network in accordance with our invention; 
         FIG. 3  is a depiction of a second embodiment or our Toll-free IP network with dynamic assisted control; 
         FIG. 4  is illustrates as sample signaling flow in accordance with one embodiment of our invention; 
         FIG. 5  is a second illustrative signaling flow in accordance with another embodiment of our invention; 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  illustrates a basic logical system architecture for supporting our invention. The basic components of a network implementing our invention are the access network  210 , the TIP owner&#39;s network  220  and the TIP administer function  230 . The key functions for implementing our inventive method in the network depicting in  FIG. 2  are performed by the TIP administrator  230 . The TIP administrator function  230  is be implemented on the following two main logical components: TIP Databases  232  and the TIP servers  231 . The TIP databases  232  store the TIP destinations and their associated TIP policies. The TIP servers  231  are used to perform the main transaction processing needed by the TIP administrator to support TIP. These functions include: A) receiving and answering queries from access networks  210  on whether an IP destination is a TIP destination; B) providing TIP policy information to access networks  210 , and C) interacting with TIP owner networks  220  to obtain TIP policies dynamically from the TIP owner networks. It could also be generate usage and billing records. Primarily, the TIP Servers  231  are the TIP administrator&#39;s interface with the access networks and with the TIP owner networks (when such interfaces are implemented). The TIP servers  231  may also be used to support other value-added services, such as directory services. 
     Within the access network, the functions needed to support TIP are implemented in the TIP Client. Specifically, a TIP client  211  has the following main functionality: A) to receive, from the access network  210 , packets that are potentially destined to TIP destinations, B) to query TIP servers  231  to determine if a destination is a TIP destination, and C) to forward packets destined to TIP destinations toward the TIP destination  221 . It also may maintain a temporary cache of TIP destinations learned from a TIP administrator to reduce the frequency of queries sent to TIP servers and it may maintain a local database of TIP destinations and TIP polices that is independent of any external TIP administrator. 
     Both the TIP client  211  and TIP server  231  are logical entities. They may be co-located or integrated with other network entities or implemented as new network entities separate from other network entities. TIP client  211  and TIP server  231  may also be implemented as an integrated entity. To increase system scalability and improve system performance, TIP databases  232  and TIP servers  231  may be implemented in a distributed fashion, potentially over multiple physical platforms in different geographical locations. 
     TIP servers  231  may also be implemented hierarchically. For example, regional TIP servers may be used to manage a subset of TIP destinations that are most relevant to that region. If a regional TIP server does not know if a destination is a TIP destination, it can then ask a TIP server at the next higher level in the TIP server hierarchy to help determine whether the destination is a TIP destination. 
     The basic operation of our invention is also illustrated in  FIG. 2 . When a user  201  first arrives at an IP access network  210 , it acquires a local IP address to receive packets from this access network. A network can allocate IP addresses to a mobile terminal without authenticating the terminal or its user. IP address allocation can be supported using, for example, the Dynamic Host configuration Protocol (DHCP) defined by the Internet Engineering Task Force (IETF). After acquiring a local IP address, the user  201  can send its packets over the local access network  210  to TIP destination  221  without having to first go through any user-to-network authentication and authorization procedure with the access network or service provider. 
     An one embodiment of our invention a Policy Enforcement Point (PEP)  212  located with the IP access network  210  which determines how packets should be handled within the IP access network (e.g., allowed to traverse the access network, discarded, or forwarded to other network entities). Examples of PEPs in the current art include IP access servers, access gateways, access routers, security proxies, wireless access points, the Gateway GPRS Support Nodes (GGSN) in a GPRS (General Packet Radio Service) network or 3GPP (Third Generation Partnership Project) network, or the Packet Data Serving Nodes (PDSN) in a 3GPP2 (Third Generation Partnership Project 2) network. When a PEP  212  receives a packet from a user  201  and discovers that its source and/or destination IP addresses have not been authorized, the PEP  212  forwards the packet to a TIP Client  211 . Alternatively, the PEP  212  may cache the packet and send a signaling packet to the TIP client  211 . The TIP client  211 , which can be collocated on the PEP  212  or implemented as a separate entity, will send a TIP Query message  213  to a TIP server  231  to check whether the destination address of the user packet is a TIP address. 
     If the TIP Response message  214  indicates that the IP address is a TIP address, the TIP client  211  instructs the PEP  212  to allow packets between the user&#39;s local address  201  and the TIP destination  221  to pass through. If the PEP  212  has packets destined to this TIP destination  221  still in its packet cache, it sends these packets into the network. From this point on, packets will flow directly between the user  212  and the TIP distination  221  without having to go through any TIP client  211  or TIP server  231 . 
     A user may also use a TIP address to communicate with non-TIP destinations. There are two basic ways to accomplish this: 
     The first approach is for the user to use the TIP owner&#39;s network to communicate with non-TIP destinations. This is similar to remote dialup into the user&#39;s enterprise network or a public service provider network and then using that network to go to other destinations. For example, a security gateway in the service provider&#39;s network can be addressed by a TIP address. A user can use the TIP address to establish a tunnel (e.g., an IPsec tunnel) to the gateway and then use it to send and receive packets to and from any destination inside or outside the service provider&#39;s network. 
     The second approach is for the user to first use a TIP address to communicate with a service provider. The service provider authenticates the user and then authorizes, via the TIP administrator, the user&#39;s use of the access network to communicate with any or specified non-TIP destinations. 
     A TIP owner can dynamically control how its TIP destinations are accessed dynamically. These more sophisticated controls over how a TIP address can be accessed can be achieved using policy-based control mechanisms and can enable other value added services such as Prepaid IP or Collect IP services. A policy on how a TIP address should be accessed is called a TIP policy. For example, TIP policies may specify the amount of time a user can access a TIP address and the amount of money a TIP owner is willing to pay for the use of access networks to communicate with a TIP address within a given time period. 
     There are two basic ways to implement TIP policies: TIP administrator-driven approaches and TIP owner-driven approaches. With a TIP administrator-driven approach, the TIP administrator performs policy-based control without relying on dynamic information from the TIP owners. With a TIP owner-driven approach, the TIP owner supplies TIP policies dynamically. 
     Using TIP administrator-driven policy-based control, a TIP owner and the TIP administrator agrees on a TIP policy, which is then configured at the TIP administrator&#39;s databases. The TIP administrator uses the information in its databases to answer TIP Query messages and instruct the access network on how to handle packets destined to a TIP address. Such pre-configured TIP policies may be used, for example, when they can be applied to any user uniformly. 
     TIP owner-driven policy control gives a TIP owner more control over how its TIP address is accessed. For example, an enterprise network may only allow its employees to use a TIP address to access its networks. An Internet service or application provider may want to use a TIP address to allow only its paying subscribers to access its networks and services. In these cases, a TIP address may identify a gateway in the TIP owner&#39;s network. Such a gateway may be, for example, a firewall or an AAA server. The TIP address will allow a user to pass through an access network to communicate with the gateway, which will authenticate the user to determine whether to allow his/her traffic to enter the TIP owner&#39;s intranets. The TIP owner can then instruct the TIP administrator dynamically on how to handle the traffic of an authorized user and reject traffic from an unauthorized user. A TIP owner can do so by issuing an Authorization Ticket, which contains TIP policy information needed by the TIP administrator and the IP access networks to control access to the TIP address for a specific user based on the result of the user authentication and authorization. 
     The basic operation of our invention in an embodiment using Authorization Tickets is illustrated in  FIG. 3 . When the TIP administrator  330  receives a TIP Query message  313  from an access network, it responds first with an initial TIP Response message  314  to authorize network access for a pre-determined temporary and short free access time (e.g., time for the user to be authenticated by the TIP owner) and to inform the TIP client  311  to wait for further TIP Response messages. Simultaneously, the TIP Administrator  330  asks the TIP owner  320  for an Authorization Ticket for the user  301 . The user  301  gains free access through the access network  310  to the TIP destination  321  during the temporary free access time. Once the user  301  gets in touch with the TIP owner  320 , the TIP owner  320  authenticates the user  301 . Upon positive authentication, a TIP Owner Client  322  in the TIP owner network  320  issues an Authorization Ticket  323 , which carries the TIP policy information, to the TIP Administrator  310 . The TIP Administrator  310  forwards the TIP policy information in the Authorization Ticket to the access network  310  in the TIP Response messages  324 . The TIP client  311  in the access network provider&#39;s network records the TIP policy information from the TIP Administrator  330  and uses it to determine how the user&#39;s  301  traffic should be handled inside the access network  310 . To prevent malicious use of the network, the access network blocks the user&#39;s packet flow if the authorization expires. The TIP system does not impose any restriction on how a TIP owner processes the packets delivered to a TIP destination. For example, an enterprise network may use its firewall and virtual private network procedures and protocols to authenticate a user. 
     Protocol Implementations 
     To support our TIP invention, a signaling protocol for the interface between TIP client and TIP server is needed. A signaling protocol between TIP server and TIP owner network is also needed to support dynamic TIP owner-driven policy control. These signaling protocols are used primarily for authentication and authorization purposes. One such protocol is known in the art as the Diameter Base Protocol (P. Calhoun, “Diameter Base Protocol” IETF RFC 3588, September 2003) and can be used as the baseline protocol for signaling over these interfaces. Diameter is envisioned to be the future AAA protocol in IP networks. To use Diameter to support a service, a Diameter application needs to be developed for the Toll-Free service. 
     Our invention includes the use of a Diameter TIP Access Network Application (TANA) that runs on the TIP client and on the TIP server with the TIP client  18  acting as the Diameter client and the TIP server as the Diameter server. 
       FIG. 4  illustrates a sample signaling flow of the TANA. Diameter uses a request and answer model in which a Diameter client sends request messages to a Diameter server that will reply with answer messages. TANA uses the following new request messages. First, AA-TIP-client-Request  410  is a request sent by TIP client  420  to TIP server  430  to query if an IP address is a TIP address and to obtain TIP policy information. This message is an example of the “TIP Query” message in  FIG. 4 . Second, AA-TIP-client-Answer  440  is an answer sent by TIP server  430  to TIP client  420  in response to an AA-TIP-client-Request  410 . This message is an example of the “TIP Response” message shown in  FIG. 4 . Third, Re-Auth-TIP-Client-Request  441  is a request sent by TIP client  420  to TIP server  430  to request for permission to extend the lifetime of an authorization for a TIP address and to update other authorization parameters. Finally, Re-Auth-TIP-Client-Answer  443  is an answer sent by TIP server  430  to TIP client  420  in response to a Re-Auth-TIP-Client-Request  410 .
         &lt;AA-TIP-client-Request&gt;::=&lt;Diameter Heather&gt;&lt;Session-Id&gt;{Auth-Application-Id} {Origin-Host} {Origin-Realm} {Destination-Realm} {Auth-Request-Type} {MH-IP-Address} {Access-Network} {Target-IP-Address}       

     Each &lt;*&gt; indicates a fixed Attribute Value Pair (AVP) that must be present and has a fixed position in the message, each {*} indicates a required AVP that must be present and can appear anywhere in the message, and each [*] indicates an optional AVP that may appear anywhere in the message. The Diameter Heather contains information used to distinguish different Diameter messages. 
     The attributes are used to support TIP and the other attributes are standard Diameter attributes. Auth-Request-Type is a standard Diameter attribute with one standard Diameter attribute value AUTHORIE_ONLY, for the TIP application. MH-IP-Address is a new attribute used to carry the source IP address of the mobile for which the Diameter session is to be established. Access-Network is a new attribute used to carry the identifier of the access network. Target-IP-Address is a new attribute that carries the IP address to be checked by the TIP server to see if it is a TIP address. 
     After processing an AA-TIP-client-Request, the TIP server returns an AA-TIP-client-Answer to inform the TIP client of the results of the AA-TIP-client-Request and what further processing, if any, needs to be taken by the TIP client. The AA-TIP-client-Answer contains all the attributes required by the Diameter Base Protocol plus new attributes that are needed to support TIP. A sample message format is as follows:
         &lt;AA-TIP-client-Answer&gt;::=&lt;Diameter Heather&gt;&lt;Session-Id&gt;{Auth-Application-Id} {Auth-Request-Type} {Result-Code} {Origin-Host} {Origin-Realm} [Auth-Grace-Period] [Authorizafion-Lifetime] [Target-IP-Address] [TIP-Network-Prefix] [Session-Timeout] [Error Message] [Failed-AVP]       

     AA-TIP-client-Answer uses a Result-Code to tell the TIP client of the result of its AA-TIP-client-Request and any further actions the TIP client should take. Some times, the TIP server may not have all the necessary TIP policy information when it receives an AA-TIP-client-Request. This may occur, for example, when the TIP server needs to get Authorization Tickets from the TIP owner dynamically. In such cases, the TIP server answers the AA-TIP-client-Request immediately with an AA-TIP-client-Answer that carries a special Result-Code value to tell the TIP client that the target IP address is a TIP address, but the TIP client should expect further TIP policy information. The following are sample values of the Result-Code in an AA-TIP-client-Answer:
         2001 DIAMETER_SUCCESS: The IP address is a TIP address and the access network should allow the user&#39;s traffic to go through according to the TIP policy attributes in the answer message. The TIP policy attributes in the sample message format include (other attributes may be added): 1) Authorization-Lifetime: A standard Diameter attribute carrying the period of time toll-free access to the target IP address is authorized, 2) Auth-Grace-Period: A standard Diameter attribute used to carry the extra period of time, beyond the Authorization-Lifetime, that can be used by the access network to gain extension to the Authorization-Lifetime, 3) Target-IP-Address: A new attribute used to carry the Target-IP-Address copied from the Target-IP-Address attribute in the corresponding AA-TIP-client-Request message, and 4) TIP-Network-Prefix: A new attribute used to carry the network prefix that specifies a TIP network prefix in the TIP owner network.   2002 DIAMETER_LIMITED_SUCCESS: The target IP address is a TIP address and the access network should allow the user&#39;s packets to pass through for a limited time as specified in the Authorization-Lifetime attribute plus the time specified in the Auth-Grace-Period. The TIP client should expect new TIP policy information from the TIP server.   5003 DIAMETER_AUTHENTICATION_REJECTED: The target IP address is not a TIP address. The AA-TIP-client-Answer message also carries a text Error-Message “IP address is not a TIP address” to provide the specific reason that caused the TIP Administrator to reject the AA-TIP-client-Request message.       

     If the user continues to send packets to the TIP address immediately after the Authorization-Lifetime expires, the TIP client will send a Re-Auth-TIP-Client-Request message to the TIP server to request the TIP server to extend the Authorization-Lifetime. This message has the same format and contains the same attributes and attribute values as the AA-TIP-Client-Request message with the following exception: the Auth-Request-Type attribute is replaced with a Re-Auth-Request-Type attribute. The value of the Re-Auth-Request-Type attribute is set to AUTHORIZE_ONLY. The Result-Code in the answer message to the Re-Auth-TIP-Client-Request can only be “2001” or “5003”. The TIP client or server can terminate a Diameter session by sending a Session-Termination-Request message to the other end of the session. 
     In another embodiment of our invention, we define a Diameter TIP Owner Application. In this embodiment a TIP server uses the Diameter TIP Owner Application (TOA) to retrieve TIP policy information dynamically from a TIP owner. The TIP server will act as a Diameter client and TIP owner network will act as a Diameter server.  FIG. 5  shows a sample signaling flow when both TANA and TOA are used to authorize access to a TIP address. The TIP server  510  initiates a Diameter session with the TIP owner  530  network by sending an AA-TIP-admin-Request message  511  to the TIP owner network  530 . This request contains all the attributes required by the Diameter Base Protocol plus new attributes used to support TIP operations. A sample format of the AA-TIP-admin-Request message is as follows:
         &lt;AA-TIP-admin-Request&gt;::=&lt;Diameter Heather&gt;&lt;Session-Id&gt;{Auth-Application-Id} {Origin-Host} {Origin-Realm} {Destination-Host} {Destination-Realm} {Auth-Request-Type} {MH-IP-Address} {Access-Network}       

     Upon receiving the AA-TIP-admin-Request message  511 , the TIP owner network  530  checks if any user with source address “MH-IP-Address” has been authorized. If the answer is yes, the TIP owner network  530  waits to see if any such user will appear during an Authorization-Timeout period. Upon detecting such a user or upon expiration of the Authorization-Timeout period, the TIP owner network  530  will return an AA-TIP-admin-Answer message  531  to the TIP server  510 . This message will contain the result of the AA-TIP-admin-Request message  511  and the TIP policy for this particular user. A sample format of the AA-TIP-admin-Answer is as follows:
         &lt;AA-TIP-admin-Answer&gt;::=&lt;Diameter Heather&gt;&lt;Session-Id&gt;{Auth-Application-Id} {Auth-Request-Type} {Result-Code} {Origin-Host} {Origin-Realm} [Authorization-Lifetime] [Auth-Grace-Period]   [Target-IP-Address]   [TIP-Network-Prefix]   [Session-Timeout] [Error-Message]   Sample values of the Result-Code include:   1) 2001 DIAMETER_SUCCESS: The user is authorized and its access to the TIP address should be controlled based on the TIP policy attributes in the AA-TIP-admin-Answer message; and   2) 5004 DIAMETER_AUTHENTICATION_REJECTED: Rejected by TIP owner or authorization failure.       

     To support TIP Authorization Tickets, the following two additional messages also need to be added to TANA. First, upon receiving an AA-TIP-admin-Answer message, the TIP server sends an Access-Granted-Message to provide the additional TIP policy information to the TIP client in the access network. A sample format of the Access-Granted-Message is as follows:
         &lt;Access-Granted-Message&gt;::=&lt;Diameter Heather&gt;&lt;Session-Id&gt;{Auth-Application-Id} {OriginHost} {OriginRealm} {Destination-Host} {Destination-Realm} [Auth-Grace-Period] [Authorization-Lifetime]   {MH-IP-Address} {Access-Network} {Target-Destination} [TIP-Network-Prefix] [Session-Timeout]       

     Second, the TIP client replies to the Access-Granted-Message with an Access-Granted-Ack message. A sample format of the Access-Granted-Ack message is as follows:
         &lt;Access-Granted-Ack&gt;::=&lt;Diameter Heather&gt;&lt;Session-Id&gt;{Auth-Application-Id} {Result-Code} {Origin-Host} {Origin-Realm} [Error-Message] [Failed-AVP]       

     The Access-Granted-Ack message carries a Result-Code value 2001 if the Access-Granted-Message is successfully processed. If any error occurred when processing the Access-Granted-Message, the Access-Granted-Ack message will carry a Result-Code value to indicate the error. The Error-Message and the Failed-AVP fields may also contain additional error messages. 
     The foregoing detailed description discloses a method and architecture for provided Toll-free IP networks services and describes proposed enabling protocols. The above described embodiments of the invention oare intended to be illustrative only. Numerous alternative embodiments may be devised by those skilled in the art without departing from the spirit and scope of the following claims. As an example, the invention described herein could be used to support other new value-added services over IP-based access networks. Such other services could include but are not limited to the following: 
     Selective Charging: With Selective Charging, charging is only incurred when a user communicates with a selected set of destinations. Such destinations, for example, may provide value-added contents or services. The use of the networks to communicate with this selected set of destinations may be paid by these destinations. Users may be allowed to use the network to communicate with other destinations for free. Selective Charging may also be used with the “caller-pay” models. In such a case, a user will be charged only when he/she communicates with any destination in a selected destination set. The user may use the access network to communicate with other destinations for free. 
     Pre-Paid IP: A user may first use TIP to gain free access to a Prepaid IP Service Provider that may be independent of the access network operators. The Prepaid IP Service Provider authenticates the user, verifies his/her pre-paid account and then authorizes the access network to allow the user to use the access network for a given time period. During this authorized time, the user may also be authorized to communicate with non-TIP destinations. With TIP, the Prepaid IP Service Provider does not necessarily have to interact with the access networks directly in order to authorize a user&#39;s use of the access networks. 
     Collect IP Call: A user may first use TIP to gain free access to a Collect IP Call Service Provider that may be independent of the access network operators. Then, the Collect IP Call Service Provider either forwards the user traffic to the final destination or authorizes the access network to allow the user to connect to the final destination directly, provided that the final destination agrees to pay for the connection. With TIP, the service provider does not necessarily have to interact with the access networks directly in order to authorize a user&#39;s use of the access networks. 
     TIP allows a content provider (e.g., an online merchant) to offer a convenient way for everyone to access its WWW sites free. 
     Our invention can be used to support seamless roaming across hotspots of different operators/aggregators and across hotspots and cellular networks, by eliminating the need for a roaming user or terminal to handle the heterogeneous user-to-network authorization protocols and the heterogeneous charging plans used by different operators/aggregators. With TIP, a user will not have to be concerned with roaming charges or the varying pricing plans of different access network operators. 
     Our invention could potentially reduce the cost of high-speed access for business travelers. Today, a business traveler typically pays a daily fee for Internet access at hotels. TIP allows the travelers to incur costs to their corporations only when they use the network.