Subject: Re: [Sip] an alternative approach for outbound proxy discovery

From: "Christer Holmberg" <[email-masked]>
Date: Fri, 7 Jul 2006 02:08:56 +0300

Hi Jonathan,

There are a couple of issues/deployment restrictions with your proposal.

1. The home proxy has, as you indicate, to know that an edge proxy is needed. If the edge proxy is used only for STUN keepalive that may be difficult, because the home proxy would need to know when keepalive is needed in the first place. Or, of course it could force all registrations to go via the edge proxy.

2. The home proxy and the edge proxy may be in different administrative domains, so the home proxy may not know the address of the edge proxy (maybe not even in which domain it's located).

3. The request may traverse a numbet of proxies in any case, so the home proxy would have to know whether one of those is the edge proxy or not.

Regards,

Christer

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From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 10 Jul 2006 11:21:08 -0400

Thanks for reading. Responses below.

Christer Holmberg wrote:

> 1. The home proxy has, as you indicate, to know that an edge proxy is
> needed. If the edge proxy is used only for STUN keepalive that may be
> difficult, because the home proxy would need to know when keepalive
> is needed in the first place. Or, of course it could force all
> registrations to go via the edge proxy.

You lost me on this one. The idea is that, within a particular service 
provider network, the home proxy knows whether the user should be using 
an edge proxy from that provider.

> 
> 2. The home proxy and the edge proxy may be in different
> administrative domains, so the home proxy may not know the address of
> the edge proxy (maybe not even in which domain it's located).

Right. This is a good point. In this particular case, I think you would 
discover the edge proxy through DHCP rather from the AOR. Then, the 
procedure works as I described, with Service-Route providing a URI with 
the keepalive=stun and the Additional-Proxies header with more proxies.

> 
> 3. The request may traverse a numbet of proxies in any case, so the
> home proxy would have to know whether one of those is the edge proxy
> or not.

If the request arrives to the home proxy from a different proxy, it 
wouldn't redirect.

-Jonathan R.

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