Midcall signaling

Midcall signaling

Midcall signaling used when the session parameters don’t change, to exchange information between two user agents via the body of an INFO message. If the session parameters did change then you would use a re-INVITE.

Note in the above figure the ISUP messages: IAM (Initial address message), ANM (Answer message), and USR (user-to-user message).

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Transcript

[slide161] Mid-call signaling. This is to be able to support communication between two gateways, because we saw we could have two public switch telephony users, we could trunk all of their traffic through voice over IP, we need some way for those two voice over IP gateways to talk to each other, that's mid-call signaling.