Basic SIP questions go on [EMAIL PROTECTED]

  
-----Original Message-----
From: Hasnaa MOUSTAFA [mailto:[EMAIL PROTECTED]]
Sent: Friday, November 16, 2001 7:43 AM
To: [EMAIL PROTECTED]
Subject: [Sip] Session Initiation Protocol


>Hello all,
>
>Concerning the Session Initiation Protocol (SIP),
>Its architecture is composed of a number of servers.
>
>1- About the Location service or Database, is it seperate for each server
or all 
>    servers access the same location service to locate users.

A location service is associated with a domain (foo.com), and all proxies or
registrars for that domain would share a location service.
Proxies/registrars in a different domain (bar.com) would use an unrelated
location service. 

>2- I am a little bit mixed between the use of Redirect Server & Proxy
Server
>   ==> When exactly does the UAC contact a proxy server and when does it  
>          contact the redirect server???

The UAC does not know which. There is no way to tell when it first sends the
request. If it gets back a 3xx, then it knows it contacted a redirect
server. A UAC contacts a server for a domain (like foo.com), and that is
whatever it is, proxy, redirect, or UAS.


>   ==> Is this is a mode chosen either to contact the redirect server or a
proxy   
>          server whenever the UAS address is not known?

The UAC does not choose. Each server decides what type of element is. When a
client wishes to make a call to a user (identified by a sip url like
sip:[EMAIL PROTECTED]), it either uses DNS to locate the server for foo.com, or
passes it to a configured server, called an outbound proxy, which performs
that dns query.

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[EMAIL PROTECTED]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com
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