Subject: Re: [Sip] SIP Extensions

From: Dean Willis <[email-masked]>
Date: Mon, 01 Nov 2004 20:32:56 -0600

Egil C. Østhus wrote:
> Hi,
> 
> I have a question about section 8.1.1.9 in rfc3261.
> It is said in this section that "The option tags listed MUST only refer to
> extensions defined in standards-track RFCs". Does this mean that the only
> legal extensions to SIP is those how are described in RFCs? If I would
> like to define a method in SIP, is it possible to use this method some way
> and at the same time be 100% SIP compliant?

Aboslutely. To make your extension 100% standards compliant, write a 
standards-track RFC describing your extension.

There's more discussion of this process in RFC 3427

ftp://ftp.rfc-editor.org/in-notes/rfc3427.txt

The basic theory is that it is not standards-compliant to REQUIRE an 
implementation manifest a non-standard extension.

So, you can invent your own extension and use it to your heart's 
content, but your implementation should work in such a way that if your 
extension is not available, it must "fall back" in some fairly graceful 
manner to standard behavior. That way, if somebody accidentally connects 
using a "standard" client, the world doesn't self-destruct underneath them.

--
Dean Willis
co-chair, SIP Working Group

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