Subject: [Sip] [SIP}: Comments on draft-ietf-sip-overlap-01

From: "Chiou, Mark" <[email-masked]>
Date: Wed, 5 Dec 2001 17:58:22 -0600

1. Section 3.3 Sending overlap signalling to the SIP network

I don't understand the desire at all. As addressed in the introduction
of this draft SIP uses en-bloc dialing approach, then any incomplete
address call will be failed with a status code indicating "484 Address
Incomplete". I did not see the desire for the MGC/MG to send overlap
signalling to the SIP network.

2. Section 4 SIP to ISUP

The whole paragraph does not make sense at all. 

I would suggest put down " It is not applicable."

In SIP, every INVITE request message MUST have a unique CSeq number
unless it is a re-transmission message. Plus, a call-leg is a
combination of a CSeq number, Call-ID, local (i.e. From address) and
remote (To address). Any content changed in any of the four fields is a
brand new call. So an incomplete address for To field shall be resulted
a failure, such that overlapping is not applicable to SIP at all.

By the way, so far I used Cisco and 3Com's SIP phones, both of them are
changing the Call-ID for every new call (i.e. any new INVITE request
message).

Mark Chiou
Santera Systems Inc.

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