Subject: SIP INFO: What is "mid-session"; sessions w/o media

From: [email-masked]
Date: Thu, 30 Mar 2000 14:47:34 -0600

1. The draft on the INFO method says that the INFO method may be used
"mid-session"; exactly what that means is not clear to me. Does it mean that
the UAC may send an INFO right after sending an INVITE, and the UAS may send
an INFO right after receiving an INVITE?

2. Is it possible to create a session without a media stream, solely for the
purpose of sending one or more INFOs, and if so, is there a standard or
preferred way of doing so?

Thanks,

Cliff Harris

---

From: Sunitha Kumar <[email-masked]>
Date: Thu, 30 Mar 2000 14:26:32 -0800

> an INFO right after receiving an INVITE?

INFO msg is used to convey something more about the session. Hence, the
requirement is that this msg has to match an existing callLeg, else it will be
rejected at the UAS.
So, you can send INFO once the callLeg is established, i.e after sending an
INVITE.

> preferred way of doing so?

I read somewhere that you can send INVITE without including the media details
(i.e without the SDP). If that is correct, then you can send INFO after this
INVITE.
So, in essence, the media stream is not (yet) opened at this time.

Hope that helps.
sunitha