A SIP cancel message is directly comparable to which type of ISUP message?

A SIP cancel message serves a similar purpose to the ISUP Release message in that both are used to terminate a session or call that was in the process of being set up. The SIP cancel message is specifically used to indicate that a call setup request should be aborted if the caller decides to cancel the call before it is completed, effectively instructing the network to halt the call establishment process.

In contrast, the ISUP Release message is employed once a call is established and indicates the need to terminate the call. Both messages function to end an ongoing call process, whether it's during setup in the case of SIP or during an established session in the context of ISUP. This similarity highlights how SIP and ISUP deal with call management and termination, making the comparison valid and aligning the roles of these messages within their respective protocols.