Thanks for the response. On reading the definition again, it does cover it as you say.
I would still like to suggest a change in wording for a couple of reasons:
1. The R-URI should be expected to be unchanged as loose routing gets more and
more adopted. Therefore, this may not be typical.
2. The example that follows is a carry over of the strict routing days.
Spiralling should be expected to happen much more with loose routing than before.
This clarification could be very useful.
Is this the forum to request change or should I post it elsewhere?
Thanks, Ganesh
Chris Boulton wrote:
Ganesh,
I think the text already adequately covers this in the definitions section (6):-
....but this time differs in a way that will result in a different processing decision than the original request.
It does say that 'Typically' this will be a change in the R-URI BUT doesn't explicitly suggest this scenario. The fact that the route set has changed should be enough to differentiate from being a loop and fall into the category of being a spiral.
Regards,
Chris.
-----Original Message----- From: Ganesh Jayadevan [mailto:[EMAIL PROTECTED] Sent: Tue 07/10/2003 18:09 To: [EMAIL PROTECTED] Cc: Subject: [Sip-implementors] when is a INVITE in a spiral (when not in a loop?)
This isa repost. Sorry about the typo in the Subject line.
Folks,
I wonder if the definitions of Spiral and Loop needs to be updated.
I am speaking within the context of using SIP in the 3G/UMTS architecture:
S-CSCF or Serving call session control function is essentially a SIP proxy + more.
A S-CSCF , can send an initial INVITE to a SIP application server (AS) for application processing. This can be done by loose-routing the request by including a set of one more route headers to the initial INVITE.
If the AS is working as a proxy, it can manipulate the INVITE and send it right back to the S-CSCF. If the AS happened to be a loose router, it will not hammer the R-URI of the INVITE and instead will follow the route set as it sees it.
The INVITE that comes back to the S-CSCF must not be thought of as being in a loop. It's route-set and Via headers, will be different and so the S-CSCF can distinguish it from the initially received INVITE. It will also fail the loop detection test as defined in section 16.6, step 8, 3rd paragraph (since the test includes hashing on the top-most Via).
imho, an INVITE arriving at an proxy more than once has to fall into one of two buckets: Loop or Spiral. Currently I see the gap between the two caused due to R-URI being the same because of loose routing.
What does the cognoscenti think of this? Should not the definitions of 'loop' and 'Spiral' be updated in Section 6?
Thanks, Ganesh
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