Subject: [SIP] Overlap dialing in SIP

From: Aseem Agarwal <[email-masked]>
Date: Mon, 18 Sep 2000 16:14:01 -0700

I need some clarification about overlap dialing in SIP as referred in
Section 4.2.1

"A UAC MUST NOT issue another INVITE request for the same call leg
before the previous transaction has completed"

"A UAS acting as a gateway ..."

The above two references are confusing. If a UAC can not initiate 
a reINVITE before receiving a definite response, how does a UAS at a
GW get additional digits ? A Gateway can get additional digits once 
the call is established (may be for supplementary services)but not 
in call set up phase. Is this correct ? 

Another source of confusion :

"If the UAC wishes to modify the session after the call set up has
begun, it MUST use another INVITE request"

Can a UA after sending an INVITE, send another INVITE for modifying the
session parameters before getting a definite response ( in call set up 
phase itself) ?

-aseem

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From: "Pathangi N Janardhanan" <[email-masked]>
Date: Wed, 20 Sep 2000 07:15:23 +0530

Hi Aseem,

> in call set up phase. Is this correct ?

 Please see draft-camarillo-sip-isup-bcp-00.txt for a detailed
call flow scenario of overlap dialing in SIP-ISUP mapping.

> session parameters before getting a definite response ( in call set
up

 A re-invite for the same call leg can be sent only after the first
INVITE
has got a definite response.

Jana