[SIPForum-discussion] loop and Spiral

srinivas.banda at wipro.com srinivas.banda at wipro.com
Wed Dec 5 05:56:27 UTC 2007

Hi find the diff b/w loop and spiral below



Loop: A request that arrives at a proxy, is forwarded, and later arrives
back at the same proxy. When it arrives the second time, its Request-URI
is identical to the first time, and other header fields that affect
proxy operation are unchanged, so that the proxy would make the same
processing decision on the request it made the first time. Looped
requests are errors, and the procedures for detecting them and handling
them are described by the protocol.


Spiral: A spiral is a SIP request that is routed to a proxy, forwarded
onwards, and arrives once again at that proxy, but this time differs in
a way that will result in a different processing decision than the
original request. Typically, this means that the request's Request-URI
differs from its previous arrival. A spiral is not an error condition,
unlike a loop. A typical cause for this is call forwarding. A user calls
joe at example.com. The example.com proxy forwards it to Joe's PC, which in
turn, forwards it to bob at example.com. This request is proxied back to
the example.com proxy. However, this is not a loop. Since the request is
targeted at a different user, it is considered a spiral, and is a valid



Srinivas Banda




From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of nidhi jain
Sent: Wednesday, December 05, 2007 10:53 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] loop and Spiral


what is loop and Spiral ?



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