Subject: [Sip] Question on via branch computation

From: Andonegui Jesus-JANDONE1 <[email-masked]>
Date: Thu, 4 Aug 2005 18:06:07 +0200

Hi,
 
I have a question related to the via branch computation: why is it possible (according to RFC3216 section 16.6 step 8) to use the topmost via header entry in the computation of the cryptographic hash ? If there is a loop, a server may get the same request from different servers and in that case the topmost via header entry will differ. If you use the topmost via header entry to compute the branch you will not detect the loop in that case.
 
Thanks,
Jesus
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---

From: "Gururaj M K" <[email-masked]>
Date: Fri, 5 Aug 2005 18:27:36 +0530

Hi,

            I think this condition happens only when maddr header is present
as part of the Via header of the request being processed.

We can chose to include topmost via header field in the computation of
cryptographic hash only if the request doesn't contain maddr header as part
of Via.

If maddr is present as part of the request then we can dropout topmost via
header field in the computation of cryptographic hash.

Regards,

Guru

  _____  

From: [email-masked] [mailto:[email-masked]] On Behalf Of
Andonegui Jesus-JANDONE1
Sent: Thursday, August 04, 2005 9:36 PM
To: [email-masked]
Subject: [Sip] Question on via branch computation

Hi,

I have a question related to the via branch computation: why is it possible
(according to RFC3216 section 16.6 step 8) to use the topmost via header
entry in the computation of the cryptographic hash ? If there is a loop, a
server may get the same request from different servers and in that case the
topmost via header entry will differ. If you use the topmost via header
entry to compute the branch you will not detect the loop in that case.

Thanks,

Jesus

---

From: Rocky Wang <[email-masked]>
Date: Wed, 17 Aug 2005 19:08:52 +0800

It is up to the implementation on how to guarantee that the loop can be
detected immediately.  And it is also very important to select the input
set.

For instance, the input can input the request-URI, all the route
headers, Call-ID, From-tag and To-tag. Based on the last 3 parameters,
it has enough information to ensure the branch ID is in the dialog, and
all the other parameters to ensure that the next processes will cause
the same behavior to all the related SIP nodes.

You can also add some other information which will impact on the route
selection and further processes.

Regards,

Rocky Wang

-----Original Message-----
Sent: 2005?8?5? 0:06

Hi,

I have a question related to the via branch computation: why is it
possible (according to RFC3216 section 16.6 step 8) to use the topmost
via header entry in the computation of the cryptographic hash ? If there
is a loop, a server may get the same request from different servers and
in that case the topmost via header entry will differ. If you use the
topmost via header entry to compute the branch you will not detect the
loop in that case.

Thanks,

Jesus