2009/1/23 Bogdan-Andrei Iancu <[email protected]>:
> Hi,
>
> actually the scenario does not imply any actual looping or spiralling.
> Maybe the following chart will be more explicit:
>
> X Proxy DSLM (A and B)
> -----------> -----INVITE A------>
> <-----486-----------
> serial fork
> -----INVITE B------>
> <-----482-----------
>
>
> So the DSLM identifies as a loop the second branch of a call for which
> it already declined the first branch.
The RURI in INVITE B is different than the RURI in INVITE A. That is
enough not to detect the request as looped:
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
[email protected]. The example.com proxy forwards it to Joe's
PC, which in turn, forwards it to [email protected]. 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
condition.
I think there is no doubt about the wrong behaviour if the DSLM.
Best regards.
--
Iñaki Baz Castillo
<[email protected]>
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