Verification of the Capability Exchange Signalling protocol

The Capability Exchange Signalling (CES) protocol is one of the sub-protocols of recommendation H.245, “Control protocol for multimedia communication” issued by the International Telecommunication Union. In this paper, we model the CES protocol with Coloured Petri Nets and verify it using state space and language analyses. The results reveal that the CES protocol could fail when the sequence numbers used by the protocol wrap. To solve this problem, we propose a set of changes to the CES protocol. State space and language analyses are then applied to the revised protocol. Verification results suggest that the revised protocol satisfies the desired properties with the errors discovered being eliminated.