Subject: [SIP] "Legal" redirect loops

From: Shail Bhatnagar <[email-masked]>
Date: Sat, 1 Jul 2000 10:03:24 -0400 (EDT)

The loop detection algorithm has been changed for proxies so that Request-URI
is also included in it. This allows spiralling of requests. What is
the policy for a client that is redirected. For example :

INVITE sip:u@p
---------------->

302 Moved Temporarily
<----------------
Contact: sip:x@p

Should the client retry the INVITE with the changed request-URI. Note that
this INVITE will be directed to same address and port.
As per the bis version :

"To avoid forwarding loops, a user agent client or proxy MUST check whether
the address returned by a redirect server equals an address tried earlier.
(Addresses match if their host and port number match.)"

Comments ??

Thanks,
Shail

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---

From: Igor Slepchin <[email-masked]>
Date: Sat, 01 Jul 2000 17:14:40 -0400

> the policy for a client that is redirected. For example :

Yes (if it wants to, of course).

> the address returned by a redirect server equals an address tried earlier.

Sounds good so far.

> (Addresses match if their host and port number match.)"
Well, this quote is taken from the previous paragraph, which talks about
Via headers:

"Any redirection (3xx) response MUST NOT suggest any of the addresses in
the Via path of the request in the Contact header field. (Addresses
match if their host and port number match.)"

I believe this is an artifact from RFC 2543, which never mentions spiral
loops.

---
Igor Slepchin

---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 05 Jul 2000 00:20:48 -0400

> I believe this is an artifact from RFC 2543, which never mentions spiral

Correct. THis paragraph needs to be removed. It is OK to suggest
addresses in the via path of the request. However, a 3xx response MUST
NOT suggest the same URL in the request URI of the request being
redirected.

-Jonathan R.
-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
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