Subject: [Sip] Re: draft-ietf-sip-outbound-01: determining STUN support

From: Cullen Jennings <[email-masked]>
Date: Thu, 05 Jan 2006 15:44:27 -0800

On 12/20/05 6:22 AM, "[email-masked]" <[email-masked]>
wrote:

> Hi,
> 
> Is it so that the only way for a UA to know if the proxy supports STUN for
> keep-alive purposes is so that the UA needs to be configured to know it? Is
> the only reason for the existence of sip-stun URI parameter that it is a
> convenient way to represent the configuration information, i.e. it makes no
> difference if the parameter is present in the actual SIP requests sent by the
> UA?

yes - it's just a way to provide the configuration information

> 
> Would there be any problem for the UA to test the support by sending a STUN
> request to proxy IP address and port?

This was originally suggested but many people were against sending a message
that would be invalid and wanted to require configuration indicating STUN
was allowed before sending a stun message.

> If it does not succeed, it can start
> using e.g. SIP OPTIONS as  a keep-alive mechanism. Perhaps this kind of thing
> could be mentioned in the draft.

I think people thought the SIP OPTIONS was always a worse idea than the CRLF
keep alive but I follow your idea.

> Regards,
> Markus  

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