[SIPForum-discussion] Diversion Header (INVITE Without SDP)

[Hadriel Kaplan]

Diversion was only defined in a draft and never got to RFC, with History-Info in its place for an RFC.  However, since Diversion is arguably more popular than History-Info...
I've seen your scenario happen due to ISUP-to-SIP interworking, where the ISUP IAM had both Redirecting Number and Original Called Number parameters that were actually the same number.  In that case, due to the rules in the diversion draft, some devices will create two Diversion headers, each with the same number, because they were just copying the numbers from ISUP parameters per the draft.
The counter parameter tracks the number of redirections for a diversion entry.  Normally it would be 1 each; but in an ISUP-SIP interworking scenario, since ISUP does not track all redirections but only the most recent one, you can't generate meaningful Diversion information for each redirection (the data doesn't exist).  But since ISUP does track the count of redirections, that count is used by Diversion, so you can tell how many redirections occurred.  The counter parameter for the bottom one should have been 1, not 3; but the top one could be 3 if the ISUP Redirect Counter was 4.  It's not technically malformed for the bottom to be 3, however, and could happen due to privacy issues where the redirecting proxy didn't want to identify some individual redirecting parties.  But it probably was an error.

-hadriel

________________________________
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Shakil, Rashid
Sent: Wednesday, November 19, 2008 12:27 PM
To: discussion at sipforum.org; discussion at sipforum.com
Subject: Re: [SIPForum-discussion] Diversion Header (INVITE Without SDP)

Any comments on my previous request ...

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Shakil, Rashid
Sent: Friday, November 14, 2008 2:58 PM
To: discussion at sipforum.org; discussion at sipforum.com
Subject: [SIPForum-discussion] Diversion Header (INVITE Without SDP)

Hello,

While working with SIP carrier I came across to an issue where particular SIP providers rejecting my calls to a cell phone number. The call happen to be a redirected call (means inbound call redirected to an offnet TN). For the redirected call (call to an offnet number) our AS is sending an INVITE without SDP with diversion headers. My SIP carrier is saying that the issue is because we are sending two identical diversion headers and we should only send "1" and the other thing they pointed out is the "counter=3" in diversion header. They mentioned that the "counter" should be 1 instead of three. Can anyone please tell me if sending 2 identical diversions is a problem also what is the significance of "counter" in diversion header.

INVITE sip:7202730836 at 67.135.78.227:5060 SIP/2.0
Via: SIP/2.0/UDP 78.33.28.55:5060;branch=z9hG4bKut2ins00bo7gqdkee7s0.1
From: <sip:7034319130 at 78.33.28.55>;tag=9ae82760-1dd1-11b2-a243-b03162323164+a4c9e520
Contact: <sip:SDao6c8-u2tgvd144pfmf20a2i22ll3v2pmhvmhvg8rpfgsg4opsvii33es1000010 at 78.33.28.55:5060;transport=udp>
To: <sip:2405993731 at 67.15.78.227>
Call-ID: 2563935-1801424197 at 69.22.23.61
CSeq: 2 INVITE
Max-Forwards: 69
Allow: INVITE,BYE,ACK,CANCEL,PRACK,REFER,OPTIONS,REGISTER,NOTIFY
Diversion: <sip:2405993731 at 69.22.23.65>;reason=no-answer;privacy=off;counter=3
Diversion: <sip:2405993731 at 69.22.23.65>;reason=no-answer;counter=3;privacy=off
Remote-Party-ID: "7034319130" <sip:7034319130 at 69.22.23.65>;party=calling;id-type=subscriber;privacy=off
P-Asserted-Identity: "7034319130" <sip:7034319130 at x.com>
Content-Length: 0


RS
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