Method of and system for providing quality of service in IP telephony

A method and system for providing quality of service in an IP telephony session between a calling party and a called party establishes a high quality of service ATM virtual circuit for the session between first and second devices, each of the devices having ATM capability and IP capability. The first and second devices provide bidirectional translation between IP media and ATM media. The system transports IP media for the session between the calling party and the first device, and between said called party and a second device. The virtual circuit transports ATM media for the session between the first and second devices. An intelligent control layer provides IP and ATM signaling to set up the session.

BACKGROUND

The present invention relates generally to the field of Internet telephony, and more particularly to a method of and system for providing quality of service in an Internet telephony session.

Two trends are currently occurring in the telecommunications marketplace. First, telephony services are being added to Internet protocol-based devices. Second, Asynchronous Transfer Mode (ATM) networks are being built with the ability to support user specified quality of service (QoS) on a per connection basis, as part of the ATM switched virtual circuit service capability.

Each of these trends have problems. The primary problem with the introduction of telephony services to the IP network is one providing predictable QoS on a per call/connection basis. Although technologies are being developed in the Internet community to address this problem, there is currently no way to guarantee QoS on a per connection basis through an IP network. The primary problem with the second trend is not one of basic service capability, but is rather one of access to the service. Today virtually all desktop devices have access to an IP network through some sort of local area network technology, for example through Ethernet. The problem is that these desktop devices generally do not have access to ATM networks that provide the per call/connection guarantee QoS.

The primary method of addressing QoS in the current IP-BASED networks is to over-provision the amount of bandwidth available in the network. This approach will work as long as the usage of the network stays within the bounds of the available bandwidth. If the usage of the network is not predictable, then it is difficult, for example, to prevent a low priority file transfer from interfering with a connection established to carry real-time voice or video data.

The primary method of providing ATM switched virtual circuit services to devices that do not have native ATM support is to install routers between the IP network and the ATM network that have the ability to generate ATM switched virtual circuits on a per IP flow basis. The problems with this approach are: (1) possible destination IP addresses need to be provisioned in the router ahead of time, and (2) it is not possible to define, on an IP flow basis, which IP flow should get the ATM switched virtual circuit service and which should get IP best efforts service. If a destination address is provisioned in the ATM interworking router, then all connections to that destination address will require an ATM switched virtual circuit.

SUMMARY

The present invention provides a method of and a system for providing quality of service in an IP telephony session between a calling party client and a called party client. The system of the present invention establishes a high quality of service ATM virtual circuit for the session between first and second devices, each of the devices having ATM capability and IP capability. The first and second devices provide bidirectional translation between Internet Protocol (IP) media and ATM media. The system transports IP media for the session between the calling party client and the first device, and between the called party client and the second device. The virtual circuit transports ATM media for the session between the first and second devices. An intelligent control layer provides IP and ATM signaling to set up the session.

In one embodiment of the present invention, the first and second devices include access control managers that are bridges between an IP network and an ATM network. The intelligent control layer assigns a temporary session IP proxy address for the called party at the first access control manager and a temporary session IP proxy address for the calling party at the second access control manager. The system establishes a switched virtual circuit through the ATM network for the session between the first access control manager and the second access control manager by assigning a temporary session calling party number at the first access control manager and a temporary session called party number at the second access control manager.

During the session, the system routes IP media from the calling party to the temporary IP proxy address of the called party at the first access control manager. The first access control manager packages the IP media in ATM cells for transport through the virtual circuit to the second access control manager. The system then routes IP media from the second access control manager to the called party. Similarly, the system routes IP media from the called party to the temporary IP proxy address of the calling party at the second access control manager. The second access control manager packages the IP media in ATM cells for transport through the virtual circuit to the first access control manager. The system then routes IP media from the first access control manager to the calling party.

In an alternative embodiment, the first and second devices include routers that have both IP and ATM capability. The calling party client obtains an authentication ticket and then initiates an IP telephony session with a quality of service request. When the called party client accepts the session, the calling party client initiates setup of a resource reservation protocol IP media session with an ingress router. The ingress router then sets up the IP media session through an egress router to the called party client. When the IP media session is setup, the ingress router sets up an ATM switched virtual connection with the egress router.

DETAILED DESCRIPTION

Referring now to the drawings, and first toFIG. 1, a system according to a preferred embodiment of the present invention is designated generally by the numeral11. System11includes a media service control point (MSCP)13. MSCP13includes an IP telephony session establishment server, which in the preferred embodiment is a session initiation protocol (SIP) server15, an ingress Asynchronous Transfer Mode (ATM) MSCP17, and an egress ATM MSCP19. As will be explained in detail hereinafter, MSCP13provides an intelligent control layer for the establishment of an Internet Protocol (IP) telephony session between a first IP telephony user client21and a second IP telephony user client23.

System11includes an ingress access control manager25and an egress access control manager27. Access control managers25and27provide a media gateway between IP telephony user clients21and23and an ATM network27. Ingress access control manager25provides an ATM media and signaling interface to an ingress ATM switch29of ATM network27. Similarly, egress access control manager27provides an ATM media and signaling interface to an egress ATM switch31of ATM network27.

InFIG. 1, IP signaling paths are indicated with dotted lines and ATM of signaling paths are indicated with dashed lines. IP media paths are indicated with solid lines and ATM media paths are indicated with bold solid lines.

In the embodiment ofFIG. 1, a Quality of Service (QoS) connection is provided by routing traffic on the QoS capable backbone provided by ATM network27. According to the present invention, an ATM connection is created for the IP telephony session between user clients21and23.

QoS extensions to the data network applications part (DNAP) protocol perform the signaling between MSCP13and access control managers25and27. The access control managers25and27establish the ATM QoS capable connection. While in the preferred embodiment of present invention, the QoS capable connection is provided by ATM switched virtual circuits, the present invention can also be implemented in a variety of other technologies, such as SONET, and wave division multiplexing.

As will be explained in detail hereinafter, the data path for the session is secured against unauthorized traffic by the use of proxy addressing. The proxy addressing requires translation by the access control managers25and27to route the media to its intended destination. During session establishment, the addresses of the media stream endpoints are exchanged between user client21and user client23. The signaling message containing the media address of user client21is changed to reflect a proxy address, which is an interface at egress excess control manager27. The excess control manager interface is assigned on a per session basis. The per session interface uniqueness is accomplished by the allocation and deallocating of ephemeral ports at the access control managers. Associated with the ephemeral ports are the addresses used to create and transit the ATM connection. Likewise, the signaling message containing the media address for user client23is changed to reflect a proxy address at ingress access control manager25.

The system of the present invention dynamically configures QoS connections and ensures their security in two ways. First, the QoS connection is dynamically configured by the use of ATM switched virtual connections. The switched virtual connections are created on a per session basis during call establishment. MSCP13invokes the IP to ATM interface mechanisms of access control managers25and27with DNAP QoS messages. As will be explained in detail hereinafter, access control manager25launches a user network interface (UNI) protocol setup. The ATM traffic sent to and received by access control managers25and27is intercepted by ATM switches29and31, respectively, and forwarded to their associated ATM MSCPs17and19. The ATM MSCPs create the switched virtual circuit between ATM switches29and31. Access control managers25and27map the media stream of the session to its switched virtual circuit and the session traffic transits their respective switch virtual circuit.

The second aspect of the real-time configuration solution is the dynamic securing of the access to the connections. This is done by dynamically allocating the proxy addresses during session establishment from a pre-provisioned proxy address pool. The proxy addresses are returned to the user clients21and23in the signaling messages. The session proxy address mapping is created at the MSCP and communicated to access control managers25and27by the DNAP protocol. The proxy addresses and the actual session addresses are held at the SIP server15and the access control managers25and27for the duration of the session. When the session is terminated, proxy addresses are deallocate.

Referring now toFIG. 2, there is shown a call flow diagram of session initiation according to the embodiment ofFIG. 1. User client21initiates the session by sending a SIP INVITE message33to user client23. For purposes of illustration, the IP address of user client21is A@XYZ.COM. The SIP INVITE is addressed to user client23at a proxy address at MSCP SIP server15, which for purposes to illustration is B@XYZ-SIP.COM. The SIP INVITE specifies the audio source as the real IP address of user client21, and specifies that QoS is requested. Upon receipt of invite33, SIP server15sends an invite35to the real IP address of user client23, at B@XYZ2000.COM. Invite35specifies the audio source as a temporary IP proxy address allocated to user client21at egress access control manager27, which for purposes of illustration is A@ACM-Y.COM. If user client23accepts the session, user client23sends a 200OK SIP response37back to SIP SERVER15, specifying an audio destination as its real IP address. While in the preferred embodiment, SIP IP telephony signaling is used, other IP signaling protocols, such as H.323 may be used.

Upon receipt of response37, SIP server15allocates a call tag, and sends a reserve bandwidth message39to ingress ATM MSCP17. Message39specifies the audio destination for the session of as a temporary IP proxy address allocated to user client23at ingress access control manager25. For purposes of illustration, the temporary IP proxy address allocated user client23is B@ACM-X.COM. The bandwidth reservation message also identifies the call tag and specifies the called number for the ATM connection as egress access control manager27.

Upon receipt of bandwidth reservation message39, ingress ATM MSCP17sends a QoS setup request41to ingress access control manager25. Setup request41identifies the real source address and proxy source address for user client21. Setup request41also identifies the call tag and the called party number. Ingress ATM MSCP17also sends a QoS setup indication message43to egress access control manager27. Setup indication43identifies the real destination address and proxy destination address for user client23, as well as the call tag and the called party number for the ATM session. Egress access control manager27responds to setup indication23with a setup indication acknowledgment45back to ingress ATM MSCP17. Upon receipt of the QoS setup request41, ingress access control manager25sends a user network interface (UNI) protocol setup message47to ingress ATM switch29. Upon receipt of UNI setup message47, ingress ATM switch29sends a DNAP setup49to ingress ATM MSCP17. When ingress ATM MSCP17responds, as indicated at51, ingress ATM switch29sends a setup message53to egress ATM switch31. Upon receipt of setup message53, egress ATM switch31sends a DNAP setup message55to egress ATM MSCP19. When egress ATM MSCP19responds, as indicated at57, egress ATM switch31sends a UNI setup message59to egress access control manager27.

Upon receipt of setup message59, egress access control manager27sends a CONNECT message61to ingress access control manager25. Upon receipt of CONNECT message61, ingress access control manager25responds to QoS setup request41with a QoS setup request acknowledgment63back to ingress ATM MSCP17. Upon receipt of setup request acknowledgment61, ingress ATM MSCP17responds to the reserve bandwidth message39with a reserve bandwidth acknowledgment message65back to MSCP SIP server15. Upon receipt of reserve bandwidth acknowledgment65, SIP server15deallocate the call tag and sends a SIP 200 OK response67back to user client21. The OK response identifies the audio destination as the temporary IP proxy address allocated to user client23at ingress access control manager25. Then, user client21sends IP media packets addressed to user client23at the temporary proxy address at access control manager25. Similarly, user client23sends IP media packet addressed to user client21at the temporary proxy address at egress access control manager27.

From the foregoing, it may be seen that the embodiment ofFIG. 1provides QoS for IP telephony sessions between IP user clients. Through the use of temporary proxies, user clients21and23are unaware that their session is carried on an ATM switched virtual circuit. User clients21and23use standard SIP messaging and standard proxying for call setup and no special intelligence is required on the part of the user clients21and23. An intelligent network layer makes the system of the present invention transparent to user clients21and23.

Referring now toFIG. 3, an alternative embodiment of the system of the present invention is designated generally by the numeral71. System71includes MSCP indicated generally at73. MSCP73includes an MSCP SIP server75, an ingress ATM MSCP77, and an egress ATM MSCP79. Additionally, MSCP73includes a policy server81. MSCP73is adapted to establish a QoS IP telephony session between a calling user client83and a called user client85.

An ingress router87provides an interface between IP user client83and an ATM network89. An egress router91provides interface between user client85and ATM network89. Ingress router87provides an interface to an ingress ATM switch93of ATM network89. Similarly, egress router91provides an interface to an egress ATM switch95of ATM network89.

Referring now toFIG. 4, there is shown a call flow diagram of session initiation according to the embodiment ofFIG. 3. User client83initiates the session with a Diameter protocol session authentication request97addressed to MSCP SIP server75. Server75responds with a Diameter session authentication response (ticket), as indicated at99. Then, user client83sends a SIP INVITE message101to user client85. For purposes of illustration, the IP address of user client85is A@XYZ.COM. The SIP INVITE101is addressed to user client85at a proxy address at MSCP SIP server75, which for purposes to illustration is B@XYZ-SIP.COM. The SIP INVITE101specifies the audio source as the real IP address of user client83, and specifies that QoS is requested. The SIP INVITE101also includes the authentication ticket received in response to Diameter session authentication request97. Upon receipt of the SIP INVITE101, SIP server75sends an INVITE103to the real IP address of user client85, at B@XYZ2000.COM. INVITE103specifies the audio source as the IP address of user client83. If user client85accepts the session, user client85sends a 200OK SIP response105back to SIP Server75, specifying an audio destination as its real IP address.

Upon receipt of 200OK SIP response105, SIP server75sends a reserve bandwidth message107to MSCP policy server81. Message107specifies the audio source for the session of as the real IP address of user client83, and the audio destination for the session as the real IP address of user client85. The message107also includes the authentication ticket. Upon receipt of the message107, MSCP policy server81sends a response109back to MSCP SIP server81. Then, SIP server75sends a SIP 200OK response111to user client83.

Upon receipt of 200OK response111, user client83sends a resource reservation protocol (RSVP) path message113to ingress router87. Then, ingress router87sends a COPS request handle message115to MSCP policy server81. When MSCP policy server81responds, as indicated at117, ingress router87sends an RSVP path message119to egress router91. Then, egress router91sends an RSVP path message121to user client85. User client85responds with an RSVP reservation response123back to egress router91. Egress router91then responds with an RSVP reservation response125back to ingress router87.

Upon receipt of response125, ingress router87sends a UNI setup message127to ingress ATM switch93. Upon receipt of UNI setup message127, ingress ATM switch93sends a DNAP setup129to ingress ATM MSCP77. When ingress ATM MSCP77responds, as indicated at131, ingress ATM switch93sends a setup message133to egress ATM switch95. Upon receipt of setup message133, egress ATM switch95sends a DNAP setup message135to egress ATM MSCP79. When egress ATM MSCP79responds, as indicated at137, egress ATM switch95sends a UNI setup message139to egress router91.

Upon receipt of setup message139, egress router91sends a CONNECT message141to ingress router87. Upon receipt of CONNECT message141, ingress router87responds to RSVP path message113with an RSVP reserve response143back to user client83. Then, the IP telephony session is established between user client83and user client85.

The embodiment ofFIGS. 3 and 4, distributes a certain amount of system intelligence to user clients83and85. User clients83and85are responsible for a greater part of call setup than are user clients21and23of the embodiment ofFIGS. 1 and 2. User clients83and85process signaling in Diameter and RSVP protocols in addition to signaling in SIP protocol.

From the foregoing it may be seen that the present invention overcomes the shortcomings of the prior art. The present invention dynamically establishes and secures QoS IP telephony sessions by routing traffic on a high QoS backbone, which is preferably an ATM backbone. Those skilled in the art will recognize alternative embodiments, given the benefit of this disclosure. Accordingly, the foregoing disclosure is intended for purposes of illustration and not limitation.