Subject: RE: [SIP] [SIP]How do the proxy server search the next proxy serv er ?

From: "Rolland, Frederic" <[email-masked]>
Date: Fri, 12 Jan 2001 17:25:06 +0100

Hello!
I think there are 3 differents URIs that can be used...
* Since "UAc" wants to contact UAs "dragon" registered at "bbb.com" domain,
requested URI would normally be "sip:[email-masked]"... (no host address,
just domain identifier, then "sip.bbb.com" must locate "dragon" user)
In this case, "sip.aaa.com" proxy has simply to place DNS requests for a
relevant SIP service handler at "bbb.com", that is "sip.bbb.com", to get
the proper address and so the route to it..

* If "UAc" knows current static host address mapping for UAs "dragon", like
"dragon.bbb.com" (host address, this time), or if no location service is
used at "sip.bbb.com" (allowing proxy to locate the user's current host)
"UAc " must use [email-masked], but I'm not sure that the session
will go through "sip.bbb.com" this time...

* "sip:[email-masked]" is certainly valid too, it is a bit like for the
first case, but now we already know the SIP server for "bbb.com"...

Hope I'm right and it helps

Frederic.

-----Original Message-----
From: [email-masked] [ mailto:[email-masked] <mailto:[email-masked]> ]
Sent: Friday, January 12, 2001 11:27 AM
To: [email-masked]
Subject: [SIP] [SIP]How do the proxy server search the next proxy server ?

proxy 1 : sip.aaa.com
proxy 2 : sip.bbb.com
UAc : [email-masked]
UAs : [email-masked]

1) When UAc sends a request(INVITE) to proxy 1, what is the Request-URI in
the Request-Line ?
    (a) INVITE : sip:[email-masked]
    (b) INVITE : sip:[email-masked]
    Which is the correct answer ?

If (b) is right,
2) How do the proxy server 1 search the next proxy server 2?

Please, Could you correct me ?
Happy new year and have a good healthy!!!

_______________________________________________
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http://lists.bell-labs.com/mailman/listinfo/sip

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 16 Jan 2001 02:09:03 -0500

> From: Rolland, Frederic [mailto:[email-masked]]
> Sent: Friday, January 12, 2001 11:25 AM
> To: '???'
> Cc: [email-masked]
> Subject: RE: [SIP] [SIP]How do the proxy server search the 
> next proxy serv er ?
> 
> 
> Hello!

That is correct. Users will not normally know the host names of the machines
that they want to call; all they have is a machine independent identifier
(exactly like the email address), which is translated and routed to the
called party's machine.

> the proper address and so the route to it..

Thats not quite right. THe actual DNS query (see
http://www.normos.org/ietf/rfc/rfc2782.txt) would be for:

_sip._udp.bbb.com

> will go through "sip.bbb.com" this time...

If you know the host name of the machine where the user resides, you can
send it directly there, yes. It will, of course, not flow through proxies.
In most real scenarios you will not know the machine name.

-Jonathan R.

proxy 1 : sip.aaa.com
proxy 2 : sip.bbb.com

If (b) is right,

---
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.cs.columbia.edu/~jdrosen         PHONE: (973) 952-5000
http://www.dynamicsoft.com