[SIPForum-techwg] comments on Interoperability Draft 3

[Dale R. Worley]

On Mon, 2005-12-12 at 11:54 -0500, Chris Sibley wrote:
> > Section 15.2: Cause Code 1,2 and 3 map to 404. I'm not an SS7 expert,
> > but after Cause Code 1, I would think that there is no reason why the
> > PBX should try this number using another route. But after reception of
> > Cause Code 2 or 3 I would think the PBX may try another route (e.g. via
> > another service provider). Thus, wouldn't it be better to use another
> > SIP response code, e.g. 604 for cause code 1?
> >
> 
> Yes, I agree, 604 would be a better choice. The "condition" of being
> "unallocated" in the PSTN is a yes or no proposition, so choosing
> another SIP server to send the call to isn't going to help.

While I can't speak to the larger issue here, I strongly recommend that
"604" be replaced by "404".  In general, the 6xx codes are a bad idea.
Whereas a 4xx code indicates that a particular agent has determined that
a particular fork of a request cannot be serviced, a 6xx code indicates
that the agent has determined that all forks of a request cannot be
serviced, and tears down all the forks.  But the recipient of one fork
can not know what URI the UAC originally requested, and so can never
know if *all* forks of the request are useless.

Dale