Serving gateway proxies for non-SIP speakers in a next generation network

1. In a communication network in which Session Initiation Protocol (SIP) is used to establish communications sessions with QoS treatment of bearer flows, a method of providing QoS treatment of a bearer flow destined to a non-SIP client attached to the network via an attachment segment connected to an attachment gateway, the method comprising steps of:

receiving a SIP-INVITE message in respect of the bearer flow, the SIP-INVITE message containing a Universal Resource Identifier (URI) identifying the non-SIP client as a destination of the bearer flow;

attempting to install a QoS policy on the attachment segment in accordance with a Traffic Specification (T-Spec) identified in the SIP-INVITE message;

detecting a result of the attempt to install the QoS policy; and

generating appropriate SIP messaging on behalf of the non-SIP client to either accept or refuse the bearer flow, based on the detected result.

2. A method as claimed in claim 1 , wherein the step of receiving a SIP-INVITE message comprises the steps of:

determining that the URI is a Serving Gateway URI type;

examining the Serving Gateway URI, the Serving Gateway URI comprising an Internet protocol (IP) address; and

determining an IP address for the attachment gateway based on the examined Serving Gateway URI.

3. A method as claimed in claim 1 , wherein the steps of receiving the SIP-INVITE message, attempting to install the QoS policy and detecting a result of the attempt to install the QoS policy are performed by a Call State Control Function (CSCF) that controls the attachment gateway.

4. A method as claimed in claim 2 , wherein the step of determining an IP address for the attachment gateway comprises the step of using a table of IP routes advertised by the attachment gateway.

5. A method as claimed in claim 3 , wherein, when the attempt to install the QoS policy is successful, the step of generating appropriate SIP messaging on behalf of the non-SIP client comprises a step of forwarding the SIP-INVITE message to a generic client proxy for the non-SIP client, the generic client proxy being responsive to receipt of the SIP INVITE message to generate the SIP messaging on behalf of the non-SIP client.

6. A method as claimed in claim 5 , wherein the generic client proxy is an extension of the CSCF functionality.

7. A method as claimed in claim 1 , wherein the SIP-INVITE message comprises an explicit identification of a desired QoS treatment of the bearer flow.

8. A method as claimed in claim 7 , wherein the explicit identification of desired QoS treatment comprises information identifying at least a required bandwidth.

9. A method as claimed in claim 8 , wherein the information comprises an identifier representative of at least a predetermined bandwidth.

10. A method as claimed in claim 7 , wherein the explicit identification of desired QoS treatment further comprises information identifying a required traffic class.

11. In a communication network in which Session Initiation Protocol (SIP) is used to establish communications sessions with QoS treatment of bearer flows, a Call State Control Function (CSCF) network element to provide QoS treatment of a bearer flow destined to a non-SIP client attached to the network via an attachment segment connected to an attachment gateway, the CSCF network element being configured to:

receive a SIP-INVITE message in respect of the bearer flow, the SIP-INVITE message containing a Universal Resource Identifier (URI) identifying the non-SIP client as a destination of the bearer flow;

attempt to install a QoS policy on the attachment segment in accordance with a Traffic Specification (T Spec) identified in the SIP-INVITE message;

detect a result of the attempt to install the QoS policy; and

generate appropriate SIP messaging on behalf of the non-SIP client to either accept or refuse the bearer flow, based on the detected result.

12. A network element as claimed in claim 11 , wherein the URI identifying the non-SIP client in the SIP-INVITE message is a Serving Gateway URI comprising an Internet Protocol (IP) address advertised by the attachment gateway for reaching the non-SIP client.

13. A network element as claimed in claim 11 , wherein, when the attempt to install the QoS policy is successful, the CSCF forwards the SIP-INVITE message to a generic client proxy for the non-SIP client, the generic client proxy being responsive to receipt of the SIP INVITE message to generate the SIP messaging on behalf of the non-SIP client.

14. A network element as claimed in claim 13 , wherein the generic client proxy is an extension of the CSCF functionality.

15. A network element as claimed in claim 11 , wherein the SIP-INVITE message comprises an explicit identification of a desired QoS treatment of the bearer flow.

16. A network element as claimed in claim 15 , wherein the explicit identification of a desired QoS treatment comprises information identifying at least a required bandwidth.

17. A network element as claimed in claim 16 , wherein the information comprises an identifier representative of at least a predetermined bandwidth.

18. A network element as claimed in claim 15 , wherein the explicit identification of the desired QoS treatment further comprises information identifying a required traffic class.