Subject: [SIP] Via's in CANCEL

From: "Provin Gurung" <[email-masked]>
Date: Sun, 30 Jul 2000 14:43:35 -0400

I have a doubt about the Via fields in the CANCEL request. If a proxy issues
a CANCEL for any branch, the Via field is initialized to the proxy. This is
made clear by the following excerpt in the bisRfc.

Section 4.2.5
"....The Via header field is initialized to the proxy issuing the CANCEL
request. (Thus, responses to this CANCEL request only reach the issuing
proxy.)"

However what happens in the case when a proxy is proxying a CANCEL request
downstream. Should it also remove all the via fields from the upstream
proxies and initialize the Via with just its own address. Seems that should
be this way to me, since CANCEL being a hop by hop request, a proxy
receiving a CANCEL has already sent a 200 OK to its  upstream proxy/ua
before proxying the request downstream and besides the response for the
CANCEL coming from downstream server is not proxied upstream.

Proveen

---

From: Igor Slepchin <[email-masked]>
Date: Mon, 31 Jul 2000 12:13:45 -0400

Provin Gurung wrote:
> downstream. 

The problem is with the meaning you put into "proxying a CANCEL
request". As you noted, CANCELs are hop-by-hop and are regenerated by
each proxy, hence, the Via of outgoing CANCELs is naturally initialized
to the address of the proxy sending the CANCEL. 

The only exception to this rule are stateless proxies. But for them,
CANCEL is no different from all other requests they are proxying. Note
that stateless proxies never generate responses.

---
Igor Slepchin

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