Subject: [Sip] a question on tags when INVITE is challenged

From: "Wang, Jin-Gen" <[email-masked]>
Date: Tue, 4 Jan 2005 22:14:50 -0700

We are running into an inter-op problem in SIP. It involves the interpretation of RFC 3261. Hopefully we can get some input from the list. Here is the call flow:

UAC                                UAS
  |     ----- INVITE (F1) ------>  |
  |     <--- 401 (F2) ------------   |
  |     ------ ACK (F3) ---------> |
  |     ------ INVITE (F4) ------> |
  |     ...............................  |
  |    <----- 200 (F5) ----------   |
  |    ------- ACK (F6) -------->  |

where INVITE (F1) has no credential and INVITE (F4) has credential. 

The vendor 1 believes INVITE (F1) and INVITE (F4) should have same From tag and 401 (F2) and 200 (F5) should have same To tag. The following quote from section 22.2 in RFC 3261 indicates F4 is an updated request.

"When a UAC resubmits a request with its credentials after receiving a
   401 (Unauthorized) or 407 (Proxy Authentication Required) response,
   it MUST increment the CSeq header field value as it would normally
   when sending an updated request."

It implicitly indicates that INVITE (F1) and INVITE (F4) are within the same dialog for a same call even though the dialog is created after INVITE (F4).

The vendor 2 believes INVITE (F1) and INVITE (F4) should have different >From tag and/or 401 (F2) and 200 (F5) should have different To tags because of the quote from section 19.3 in RFC 3261:

"When a tag is generated by a UA for insertion into a request or
   response, it MUST be globally unique and cryptographically random
   with at least 32 bits of randomness.  A property of this selection
   requirement is that a UA will place a different tag into the From
   header of an INVITE than it would place into the To header of the
   response to the same INVITE.  This is needed in order for a UA to
   invite itself to a session, a common case for "hairpinning" of calls
   in PSTN gateways.  Similarly, two INVITEs for different calls will
   have different From tags, and two responses for different calls will
   have different To tags."

Which vendor interprets the tag requirements correctly?

Thanks.

Jin-Gen Wang
Level3 Communications Inc.
1025 Eldorado Blvd.
Broomfield, CO 80021

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: "Nataraju A B" <[email-masked]>
Date: Wed, 5 Jan 2005 11:18:54 +0530

Comments inline...

Best Regards,
Nataraju A.B.
-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Wang, Jin-Gen
Sent: Wednesday, January 05, 2005 10:45 AM
To: [email-masked]
Subject: [Sip] a question on tags when INVITE is challenged

We are running into an inter-op problem in SIP. It involves the
interpretation of RFC 3261. Hopefully we can get some input from the
list. Here is the call flow:

UAC                                UAS

The vendor 1 believes INVITE (F1) and INVITE (F4) should have same From
tag and 401 (F2) and 200 (F5) should have same To tag. The following
quote from section 22.2 in RFC 3261 indicates F4 is an updated request.

It implicitly indicates that INVITE (F1) and INVITE (F4) are within the
same dialog for a same call even though the dialog is created after
INVITE (F4).

[ABN] this might be confusing text... may needs to be modified...

The vendor 2 believes INVITE (F1) and INVITE (F4) should have different
>From tag and/or 401 (F2) and 200 (F5) should have different To tags
because of the quote from section 19.3 in RFC 3261:

[ABN] I feel the vendor 2 interprets correctly...
Once the failure response received for an INVITE request and that
transaction is closed the session will also be deleted since there are
no other dialog exists as part of the same session. Hence the
application (no the user) has to initiate a new session with new from
tag to send the INVITE (F4) with challenge response...

Thanks.

Jin-Gen Wang

---

From: Vijay Gaur <[email-masked]>
Date: Wed, 5 Jan 2005 07:20:20 -0800 (PST)

Hi Wang,
  Vendor1's SIP implementation should not expect same To-tag which is present in 401. There is no dialog established by 401 response. New INVITE with credentials is totaly different request. In fact few SIP implementations might send the same From tag of original INVITE. 
 
You can see similar call flows in the draft below:
http://www.iptel.org/info/players/ietf/callflows/draft-ietf-sipping-basic-call-flows-02.txt
 
Thanks,
Vijay Gaur

Nataraju A B <[email-masked]> wrote:
Comments inline...

Best Regards,
Nataraju A.B.
-----Original Message-----

UAC UAS

Thanks.

Jin-Gen Wang

Vijay Gaur
It's how you deal with failure that determines how you achieve success.
Au revoir, Adios, Namaste
		
---------------------------------
Do you Yahoo!?
 Take Yahoo! Mail with you! Get it on your mobile phone.