Subject: [Sip] SIP-ISUP-03 draft SUS/RES INFO or RE-INVITE

From: "Shafique, Hashim" <[email-masked]>
Date: Wed, 31 Oct 2001 11:47:01 -0500

In Section 8.1 of the SIP-ISUP-03 draft, the call flows for SUS and RES show
re-INVITEs.  Should not the INFO method be used to carry mid call ISUP
messages. Is there any reason why RE-INVITEs are used instead of INFO?
Thanks
HashimS.

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From: "Bob Penfield" <[email-masked]>
Date: Wed, 31 Oct 2001 13:17:21 -0500

INVITEs must be used to convey SDP to cause the media flow to be stopped and
restarted. INFO cannot be used because you're not allowed to change call
state with INFO.

(-:bob

Robert F. Penfield
Chief Software Architect
Acme Packet, Inc.
130 New Boston Street
Woburn, MA 01801
[email-masked]

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From: Christer Holmberg <[email-masked]>
Date: Wed, 31 Oct 2001 20:57:57 +0200

Hi,

This has been much discussed before, and one problem is what network
scenario you are looking at:

Consider the following case:

PSTN1 ---- GW1 ---- SIP ---- GW2 ---- PSTN2

Now, in this case you may not want your gateways (GW) to do anything to
the media, but simply forward the SUS/RES messages from one PSTN side to
the other. If you don't support ISUP MIME, the only way is for GW1 to
generate a re-INVITE. BUT, you still don't want GW2 to do anything to
the media, but simply to generate SUS/RES towards the other PSTN side.

So, the question is: should a PSTN/SIP GW be allowed to map a call
hold/un-hold message into a SUS/RES, without doing anything to the
media?

Regards,

Christer Holmberg
Ericsson Finland