[Sip] Re: draft-ietf-sip-sips-04: 403 instead of last hop exception

["Jeroen van Bemmel" <jbemmel at zonnet.nl>]

Francois,

Refer to RFC3261 16.5: if a proxy is not responsible for the request URI it 
MUST NOT recurse on 302

416 does not have the right semantics (since the endpoint may in fact 
support sips, proxies currently should never generate this response) and 
RFC3261 section 16.7 step 4 says that a proxy responsible for the URI should 
recurse on it (should only happen in call forwarding scenarios, but still)

Lots of other error responses would prevent automatic recursion, but that 
does not make them any more suitable than 403 (which is not suitable either, 
IMHO)

If you really want to be on the safe side, a new 4xx response code would be 
best

Regards,
Jeroen

Francois Audet wrote:
> Actually, 416 would achieve what you want.
> 302 would not be backward compatible because some proxy somewhere
> could recurse on it, resulting in a downgrade.
>
> If people prefer a 416, I can put that.
>
> I do personaly prefer the 403, because I'd like to avoid any thing
> that would cause a proxy to "automatically" recurse, thereby resulting
> in a downgrade.
>
> ________________________________
>
> From: Jeroen van Bemmel [mailto:jbemmel at zonnet.nl]
> Sent: Monday, June 04, 2007 16:20
> To: sip at ietf.org
> Cc: Audet, Francois (SC100:3055)
> Subject: draft-ietf-sip-sips-04: 403 instead of last hop
> exception
>
>
> In section 4.2
> http://www.ietf.org/internet-drafts/draft-ietf-sip-sips-04.txt
> proposes that a proxy should send 403 rather than apply the last hop
> exception.
>
> Instead, I would propose that it would send a 302 with either
> the registered Contact or the received request URI with a "sip:"
> scheme. 403 would be confusing, because the caller cannot distinguish
> between this case and the callee refusing his call. Perhaps a new
> response code (4xx Unsecure transport not allowed) would be better.
>
> Perhaps a caller preference should be defined to request such
> behavior, similar to "fork" and "no-fork" (RFC3841). Say "no-sips-sip"
>
> Regards,
> Jeroen 



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