System and method for implementing quality of service fallback using resource reservation protocol

1. A method for implementing a Quality of Service (QoS) failback using Resource Reservation Protocol (RSVP), comprising:

initiating a communication session with a QoS precondition between a first domain and a second domain;

determining whether the second domain supports the QoS precondition;

establishing intra-domain RSVP in the first domain if the second domain does not support the QoS precondition and end-to-end RSVP is not available;

retrying the communication session with the second domain without the QoS precondition; and

facilitating communication between the first domain and the second domain using the intra-domain RSVP in the first domain.

2. The method of claim 1 , further comprising:

receiving a response that the second domain does not support the QoS precondition; and

releasing the communication session in the second domain.

3. The method of claim 1 , further comprising maintaining the communication session in the first domain.

4. The method of claim 1 , wherein establishing the intra-domain RSVP comprises communicating with one or more RSVP agents to establish QoS in the first domain.

5. The method of claim 1 , wherein establishing the intra-domain RSVP comprises:

communicating with a first RSVP agent;

allocating a second RSVP agent; and

reserving bandwidth between the first RSVP agent and the second RSVP agent to establish the intra-domain RSVP.

6. The method of claim 5 , wherein:

the first RSVP agent is associated with an endpoint in the first domain; and

the second RSVP agent is associated with a Session Initiation Protocol trunk that facilitates the communication between the first domain and the second domain.

7. A system for implementing a Quality of Service (QoS) fallback using Resource Reservation Protocol (RSVP), comprising:

an endpoint in a first domain operable to initiate a communication session with a QoS precondition between the first domain and a second domain;

a call manager in the first domain coupled to the endpoint, the call manager operable to:

determine whether the second domain supports the QoS precondition; and

establish intra-domain RSVP in the first domain if the second domain does not support the QoS precondition and end-to-end RSVP is not available;

retry the communication session with the second domain without the QoS precondition; and

facilitate communication between the first domain and the second domain using the intra-domain RSVP in the first domain; and

one or more RSVP agents in the first domain coupled to the call manager, the RSVP agents operable to facilitate the intra-domain RSVP in the first domain.

8. The system of claim 7 , the call manager further operable to:

receive a response that the second domain does not support the QoS precondition; and

release the communication session in the second domain.

9. The system of claim 7 , the call manager further operable to maintain the communication session in the first domain.

10. The system of claim 7 , the call manager further operable to communicate with the one or more RSVP agents to establish QoS in the first domain.

11. The system of claim 7 , the call manager further operable to:

communicate with a first RSVP agent;

allocate a second RSVP agent; and

reserve bandwidth between the first RSVP agent and the second RSVP agent to establish the intra-domain RSVP.

12. The system of claim 11 , further comprising a Session Initiation Protocol (SIP) trunk operable to facilitate communication between the first domain and the second domain, wherein:

the first RSVP agent is associated with the endpoint in the first domain; and

the second RSVP agent is associated with the SIP trunk.

13. A system for implementing a Quality of Service (QoS) failback using Resource Reservation Protocol (RSVP), comprising:

means for initiating a communication session with a QoS precondition between a first domain and a second domain;

means for determining whether the second domain supports the QoS precondition;

means for establishing intra-domain RSVP in the first domain if the second domain does not support the QoS precondition and end-to-end RSVP is not available;

means for retrying the communication session with the second domain without the QoS precondition; and

means for facilitating communication between the first domain and the second domain using the intra-domain RSVP in the first domain.

14. A method for implementing a Quality of Service (QoS) fallback using Resource Reservation Protocol (RSVP), comprising:

initiating a communication session with a QoS precondition between a first domain and a second domain;

determining whether the first domain supports the QoS precondition;

establishing intra-domain RSVP in the second domain if the first domain does not support the QoS precondition and end-to-end RSVP is not available;

retrying the communication session with the first domain without the QoS precondition; and

facilitating communication between the first domain and the second domain using the intra-domain RSVP in the second domain.

15. The method of claim 14 , further comprising:

receiving a response that the first domain does not support the QoS precondition; and

releasing the communication session in the first domain.

16. The method of claim 14 , further comprising maintaining the communication session in the second domain.

17. The method of claim 14 , wherein establishing the intra-domain RSVP comprises communicating with one or more RSVP agents to establish QoS in the second domain.

18. The method of claim 14 , wherein establishing the intra-domain RSVP comprises:

communicating with a first RSVP agent;

allocating a second RSVP agent; and

reserving bandwidth between the first RSVP agent and the second RSVP agent to establish the intra-domain RSVP.

19. The method of claim 18 , wherein:

the first RSVP agent is associated with an endpoint in the second domain; and

the second RSVP agent is associated with a Session Initiation Protocol trunk that facilitates communication between the first domain and the second domain.