Subject: RE: [Sip] I-D ACTION:draft-ietf-sip-outbound-03.txt

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Fri, 24 Mar 2006 13:52:23 +0100

Hi, 

 > What I am saying is: if your outbound proxy is located in the ISP A
> network (evil.walled.garden.com), and you do the DNS lookup based on
ISP  > C (free.and.open.tutpro.com), where your registrar is located,
how will  > the DNS return the address of a outbound proxy within the  >
evil.walled.garden.com domain?

>i have said already two times that in the default common case, there
are no walled gardens or firewalls that would prevent outbound sip
traffic.

So, why do you need an outbound proxy in the first place??? You simply
do a DNS lookup based on the AoR, and receive the address of the
registrar - or a proxy in the same domain. This is pure RFC3261/3263
behavior, so I don't see what there is to standardize...

I thought the outbound draft is trying to solve the case when you DO
have a NAT, or something similar...

>>I don't think we can assume that the outbound proxy and the registrar

>>are the same thing, or that they are located in the same domain/AoR.
>in the default common case we can assume that the registrar and
outbound proxy for a domain are the same.

So, again, what is there to standardize?

>this what most SIP phones on the market assume today and i haven't seen
any problems with it.

As far as I know, most SIP phones gives you the possibility to configure
an outbound proxy, which is completely separate from the AoR where
requests are addressed...

>i understand that in walled gardens this may not work, but for those
environment you are welcome to do something more complicated that the
default 
>operation.

In 3GPP the terminals get the address of the P-CSCF using a discovery
mechanism, and I believe it works quite well. You don't have to
configure the proxy address...

Regards,

Christer

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---

From: Juha Heinanen <[email-masked]>
Date: Fri, 24 Mar 2006 15:17:23 +0200 (EET)

> behavior, so I don't see what there is to standardize...

normal SRV lookup does return names of proxies of the domain, but my
perhaps poor understanding of outbound is that that is not enough.  UA
also needs to somehow get the tags, e.g., ";lr;sip-stun" associated with
an outbound proxy.  i'm not sure if those can be added after hostname in
regular SRV reply.

 > have a NAT, or something similar...

sure, and i don't have any problems with regular NATs.  what i said that
the common case does not include firewalls or walled gardens that would
prevent outbound SIP traffic.  NATs don't do so.

 > So, again, what is there to standardize?

see above.  how does the UA learn the tags associated with the proxies.
if they can be just appended after the hostname in regular SRV lookup,
then fine, we don't need to standardize any new protocols.  however,
the draft MUST mandate that each UA that implement outbound, MUST also
implement the lookup as default behavior.

 > requests are addressed...

sure, but manual configuration is not a good thing.  if we don't want
SIP to be ridiculed by skype folks, we need to start taking
auto-configuration very seriously.

 > configure the proxy address...

fine, and i want the same for regular SIP UAs and i want it to be
such implementation to be mandated by the outbound spec.

-- juha