Subject: [SIP] need some info abt SIP proxy

From: [email-masked]
Date: Wed, 9 May 2001 15:12:10 +0530

hi,
i'm trying to implement SIP proxy server, i have 
few questions and hope to get the answeres 
ASAP :)
1) when ever a INVITE request comes to the 
proxy, first should it check for whether the 
user is registered for the proxy?

if so.. the user should also get registerd in 
all the proxies the mesage gets routed?

2)How the billing is implemented in a proxy?

3) I guess its always two proxies that is 
required to establish a session... is that true? 
if not kindly explain.

4) how exactly the message gets routed to its 
destination ( i.e. how the proxy comes to know 
destination IP address..etc)?

thanks in advance :)
Sachin K

Enjoy being an Indyan at http://www.indya.com

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---

From: "Ranjit Avasarala" <[email-masked]>
Date: Wed, 9 May 2001 11:30:07 -0500

Sachin see my comments inline...

Regards
Ranjit
Mascon Communication Technologies
http://www.masconit.com

----- Original Message -----
From: <[email-masked]>
To: <[email-masked]>
Sent: Wednesday, May 09, 2001 4:42 AM
Subject: [SIP] need some info abt SIP proxy

hi,

the user does not register with proxy but registers with registrar.
say if u have both registrar and proxy residing in same machine then u can
say user registers with proxy.

proxies do the routing

i don't think proxies establish any sessions. It will be thw user agents
that will establish sessions.

may be proxy could use location service ( location servers) to find the
location of the UAS.

thanks in advance :)
Sachin K

---

From: Brian Gracely <[email-masked]>
Date: Wed, 09 May 2001 12:47:35 -0400

comments inline

BG

>all the proxies the mesage gets routed?

##  not all devices (such as SIP-GW) will register.  Proxies should also be 
able to handle INVITE messages from devices that are not registered.  The 
logic by which they decide to "trust" that end-point is implementation 
specific.

>2)How the billing is implemented in a proxy?

##  billing or accounting?  accounting could be done based on having 
Record-Route enable and creating Start & Stop records on the 200OK and 
BYE.  Billing is beyond the scope of SIP as it involves formatting the 
records, rate-tarrifs, etc..

##  btw - it's not mandated that the SIP Proxy even do accounting, in fact 
many in the industry believe that it should not be done for IP to IP calls 
(no PSTN involved) and only done at the SIP-GW where it touches the 
PSTN.  this is mostly a religious argument, but there is nothing in the 
protocol which prevents you from doing accounting in either place or both.

>that will establish sessions.

##  a session can be directly established between two UAs.  Proxies provide 
a routing function.

>may be proxy could use location service ( location servers) to find the

##  Location-Server is one "function" and this is implemented differently 
by different people.  In essence, you're asking how should you find the 
thing that knows about where a user is.  This could be ENUM, a 
Subscriber-DB (Oracle, SQL, etc..) a Redirect-Server fronting a 
Least-Cost-Routing engine, etc..