Re: ERROR 483 too many hops

On 11/14/2017 10:42 PM, Kai Dupke wrote:
> I looked into the dumps and what I get is
> 
> TK.5062 > siproxd.5060: SIP: OPTIONS sip:kai@voip SIP/2.0
> siproxd.5060 > TK.5062: SIP: SIP/2.0 483 Too Many Hops
> 
> The dumps show the telephone system sends with "Max-Forwards:0" which is
> rejected by siproxd for obvious reasons.

Never believe in something that looks obvious.

RFC3261:
The target of the OPTIONS request is identified by the Request-URI,
   which could identify another UA or a SIP server.  If the OPTIONS is
   addressed to a proxy server, the Request-URI is set without a user
   part, similar to the way a Request-URI is set for a REGISTER request.

   Alternatively, a server receiving an OPTIONS request with a *Max-
   Forwards* header field value of 0 *MAY* respond to the request
   regardless of the Request-URI.

So, it looks like the phone system tries to get some data from the
proxy, by setting max-forward to zero.

Not sure if the 'may' in the RFC could be answered by the 483 siproxd
sends or if this is a bug in siproxd handling of the OPTIONS message.

Does siproxd implements options handling at all (not forwarding an
options message, but answering a dedicated request via options message
to the proxy)?

However, this might explains why it still is working, as the answer is
optional, even I doubt optional is same as 483.

Best regards,
kai


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