Subject: [SIP] Stateless proxy handling for looped requests

From: [email-masked]
Date: Mon, 15 Jan 2001 10:02:08 +0530

Hi,

Does a stateless proxy always forward every request it receives ? What
about requests that have looped or have a max-forwards indicating 0 ? Can
it generate responses to such requests ? Is a stateless proxy allowed to
send "Forbidden" response to requests from a particular user or domain ?

If a stateless proxy does respond to such requests with "Loop Detected" or
"Too Many Hops" responses, should these responses be retransmitted if the
request was an INVITE ?

I have another doubt about the Allow header. Since a proxy forwards
requests of any kind, what are the methods that it adds in the Allow
headers if it needs to respond to an OPTIONS request ?

Regards,
Binu

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---

From: "Jo Hornsby" <[email-masked]>
Date: Mon, 15 Jan 2001 09:37:32 -0000

First, look at: http://www.cs.columbia.edu/%7Ehgs/sip/faq/cache/36.html
Bearing this in mind....

> send "Forbidden" response to requests from a particular user or domain ?

A proxy that is behaving stateless does not generate responses.
In cases such as these, the proxy would have to respond in a
stateful fashion.

> "Too Many Hops" responses, should these responses be retransmitted if the

Yes.

> headers if it needs to respond to an OPTIONS request ?

When a "proxy" responds to an OPTIONS, it is not responding as a
proxy, but as a server.  Therefore, I would imagine a SIP proxy-like
entity that always behaved statelessly (except in the error cases
you listed above) would respond to OPTIONS with
  Allow: ACK, CANCEL
Alternatively, a chimeric beast consisting of a registrar and proxy
would respond with
  Allow: ACK, CANCEL, REGISTER

Cheers,

 - Jo.