Tandem call admission control by proxy for use with Non-Hop-By-Hop VoIP signaling protocols

1. A method of determining whether to set up a delay-sensitive communication session over an internet protocol (IP) based network, the IP based network comprising at least one link state protocol controlled network, the link state protocol controlled network comprising a plurality of network nodes interconnected by links, the method comprising:

sharing link state information among the network nodes of the link state protocol controlled network;

receiving an IP packet conveying a request to set up a delay-sensitive communication session over the IP based network;

determining, based on the shared link state information, a shortest path through the link state protocol controlled network for the requested delay-sensitive communication session;

determining, based on the shared link state information, whether the shortest path is deemed suitable for the delay-sensitive communication session; and

setting up the delay-sensitive communication session over the shortest path only when the shortest path is deemed suitable for the delay-sensitive communication session.

2. The method of claim 1 , wherein the IP packet conveying a request to set up a delay-sensitive communication session comprises a session initiation protocol (SIP) message.

3. The method of claim 1 , wherein a network device external to the link state protocol controlled network determines the shortest path, determines whether the shortest path is deemed suitable for the delay-sensitive communication session and initiates setting up of the delay-sensitive communication session only when the shortest path is deemed suitable for the delay-sensitive communication session based on link status information received from the link state protocol controlled network.

4. The method of claim 3 , wherein the network device external to the link state protocol controlled network requests link state information from at least one network node of the link state protocol controlled network.

5. The method of claim 4 , wherein the network device external to the link state protocol controlled network requests link state information from each network node of the link state protocol controlled network.

6. The method of claim 5 , wherein the link state information requested from each network node comprises respective link status information for each outgoing link of that network node.

7. The method of claim 3 , wherein the network device external to the link state protocol controlled network comprises a gateway connected to the link state protocol controlled network.

8. The method of claim 3 , wherein the IP packet conveying the request to set up a delay-sensitive communication session is received at the network device external to the link state protocol controlled network.

9. The method of claim 3 , wherein the link state controlled network is a Multi-Protocol Label Switching (MPLS) network and the shortest path comprises an MPLS tunnel.

10. The method of claim 1 , wherein a network node of the link state protocol controlled network determines the shortest path, determines whether the shortest path is deemed suitable for the delay-sensitive communication session and initiates setting up of the delay-sensitive communication session only when the shortest path is deemed suitable for the delay-sensitive communication session based on the link state information shared among the network nodes.

11. The method of claim 10 , wherein the link state information shared among the network nodes comprises link status information for each outgoing link of each network node.

12. The method of claim 1 , wherein the IP packet conveying the request to set up a delay-sensitive communication session is received at a network node of the link state protocol controlled network.

13. The method of claim 1 , wherein sharing link state information among network nodes of the link state protocol controlled network comprises receiving by each network node link state information from neighboring network nodes and populating at each network node a database containing link state information on each link in the link state protocol controlled network.

14. The method of claim 1 , wherein determining a shortest path through the link state protocol controlled network for the delay-sensitive communication session comprises determining a path that meets a minimum metric.

15. The method of claim 14 , wherein the minimum metric comprises a minimum number of hops.

16. The method of claim 14 , wherein the minimum metric comprises a minimum packet delay.

17. The method of claim 1 , wherein determining that the shortest path is deemed suitable for the delay-sensitive communication session comprises determining that each link on the shortest path is deemed suitable for the delay-sensitive communication session.

18. The method of claim 17 , wherein determining that each link on the shortest path is deemed suitable for the delay-sensitive communication session comprises determining that each link on the shortest path has sufficient available bandwidth.

19. The method of claim 18 , wherein determining that each link on the shortest path has sufficient available bandwidth comprises determining that each link on the shortest path has sufficient unused bandwidth.

20. The method of claim 18 , wherein determining that each link on the shortest path has sufficient available bandwidth comprises determining that each link on the shortest path has a sufficient combination of unused bandwidth and bandwidth that can be taken from lower priority traffic.

21. The method of claim 18 , wherein determining that each link on the shortest path has sufficient available bandwidth comprises:

monitoring link utilization for at least one class of traffic;

comparing the monitored link utilization to a threshold; and

determining that the shortest path has sufficient bandwidth based on the comparison.

22. The method of claim 17 , wherein determining that each link on the shortest path is deemed suitable for the delay-sensitive communication session comprises determining that the delay-sensitive communication session is consistent with traffic engineering policy set for each link on the shortest path.

23. The method of claim 1 , comprising issuing a communication session rejection message when the shortest path is not deemed suitable for the delay-sensitive communication session.

24. The method of claim 1 , wherein the delay-sensitive communication session comprises at least one of a voice call, a video session and a combined voice and video session.

25. The method of claim 1 , wherein the delay-sensitive communication session entails exchange of at least one of data and command signals.