[SIPForum-discussion] very imp question about route& recordroute

Wed Apr 25 05:57:46 UTC 2007

My comments inline.

________________________________

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of William Prusty
Sent: Wednesday, April 25, 2007 9:24 AM
To: Deepanshu
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] very imp question about route&
recordroute

Can u tell me whether in the implementation it is mandatory that any UAC
must be configured  to any proxy (let P1).

[Srinivas] It is not mandatory to configure UAC to any proxy. The
advantage if you configured any proxy is time save to identify the next
hop ip address and port. Suppose the outbound proxy is not configured
for UAC (A), then A should do DNS look up and server will return list of
servers to try. The returned list should cache in UAC till the
successful invite is sent to any server and response is received for
that. 

All these can be avoided if you configure outbound proxy.

As SIP is used for the establishment of interactive communications
services, the time it takes to complete a transaction between a caller
and called party is important. Typically, the time from when the caller
initiates a call until the time the called party is alerted should be no
more than a few seconds. Given that there can be multiple hops, each of
which is doing DNS lookups in addition to other potentially
time-intensive operations, the amount of time

available for DNS lookups at each hop is limited.

I don't think so bcz if this will be the case , then every request
generated from UAC will must have an ROUTE header field.

[Srinivas]  You are right. 

But RFC doesn't says that Route is mandatory in the invite request

[Srinivas] You are right

Plz answer

________________________________

From: Deepanshu [mailto:deepanshu at huawei.com] 
Sent: Wednesday, April 25, 2007 6:54 AM
To: William Prusty
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] very imp question about route&
recordroute

yes, i think so............... P1 is a default proxy for user A to
forward his request.

request will contain the route header, now if p1 wants to be in media
path then it will record route

	----- Original Message ----- 

	From: William Prusty <mailto:williamp at TechMahindra.com>  

	To: Deepanshu <mailto:deepanshu at huawei.com>  

	Sent: Tuesday, April 24, 2007 5:12 PM

	Subject: RE: [SIPForum-discussion] very imp question about
route& recordroute

	If P1 must be configured at   A ;s client , then every time the
request generated by A will contains the route header field containing
the address of P1

	Am I right?? Plz clarify

________________________________

	From: Deepanshu [mailto:deepanshu at huawei.com] 
	Sent: Tuesday, April 24, 2007 2:34 PM
	To: William Prusty
	Cc: discussion at sipforum.org
	Subject: Re: [SIPForum-discussion] very imp question about
route& recordroute

	P1 MUST be configured in A's client

		----- Original Message ----- 

		From: William Prusty <mailto:williamp at TechMahindra.com>

		To: Deepanshu <mailto:deepanshu at huawei.com>  ; Srinivas
. <mailto:nsrinivas at TechMahindra.com>  

		Cc: discussion at sipforum.org 

		Sent: Tuesday, April 24, 2007 11:52 AM

		Subject: RE: [SIPForum-discussion] very imp question
about route& recordroute

		Thank u deepansu. 

		If p1 is not configured in A "s client , then whether at
that time A required help of DNS to find the address of p1.????

________________________________

		From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Deepanshu
		Sent: Tuesday, April 24, 2007 7:23 AM
		To: Srinivas .
		Cc: discussion at sipforum.org
		Subject: Re: [SIPForum-discussion] very imp question
about route& recordroute

		My understanding about this is:

		P1 is the proxy server in A's domain, so the address of
P1 should be configured in the A's client.

		when P1 receive the request it will do the DNS query to
find the location of the next hop in the target domain (as per the line
mentioned by Srinivas) and then send the request to P2 which will inturn
forward the request to B

		Deepanshu Gautam
		R&D Engineer
		Huawei Technologies Co. Ltd.
		Nanjing Institute, No 91 BaiXia Rd. 
		Nanjing, Jiangsu, P. R. China 210001
		Mobile: +86-13585147627
		Email: depanshu at huawei.com

			----- Original Message ----- 

			From: Srinivas .
<mailto:nsrinivas at techmahindra.com>  

			To: William Prusty
<mailto:williamp at techmahindra.com>  ; mwilliam prusty
<mailto:callwilliam90653 at rediffmail.com>  ; discussion at sipforum.org 

			Sent: Monday, April 23, 2007 6:44 PM

			Subject: Re: [SIPForum-discussion] very imp
question about route & recordroute

			William Refer RFC 3261 Section.10.

			If a user wants to initiate a

			session with another user, SIP must discover the
current host(s) at

			which the destination user is reachable. This
discovery process is

			frequently accomplished by SIP network elements
such as proxy servers

			and redirect servers which are responsible for
receiving a request,

			determining where to send it based on knowledge
of the location of

			the user, and then sending it there.

________________________________

			From: William Prusty 
			Sent: Monday, April 23, 2007 1:36 PM
			To: Srinivas .; mwilliam prusty;
discussion at sipforum.org
			Subject: RE: [SIPForum-discussion] very imp
question about route & recordroute

			Thank a lot srinivas. Plz make me clarify one
thing more 

			                If A doesn't know IP address of
p1 then how the invite request will reached at B

________________________________

			From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Srinivas .
			Sent: Monday, April 23, 2007 11:05 AM
			To: mwilliam prusty; discussion at sipforum.org
			Subject: Re: [SIPForum-discussion] very imp
question about route & recordroute

			William my comments inline

________________________________

			From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of mwilliam prusty
			Sent: Saturday, April 21, 2007 10:20 AM
			To: discussion at sipforum.org
			Subject: [SIPForum-discussion] very imp question
about route & record route

			can any body tell that 

			suppose the call setup is lke  A  p1    p2    B

			here A is user agent client. B is user agent
server. p1 & p2 are proxy. 
			1.let A has generated an  INVITE request to B .
in which case the invite request generated by A will conatin ROUTE
header field.????
			[Srinivas]  Generally , proxy P1 gets IP address
of B from location server also if there are any proxies in between. 

			               Proxy P1 (generate INVITE) fills
route and send  INVITE. 

			User A can fill route set only if it knows the
proxies between user A and user B.

			2. let p1 has rcved the INVITE request containg
ROUTE heder field.
			is it mandatory that the invite from point p1 to
p2 will conatin RECORD ROUTE heder field.????? if yes why if not why???

			[Srinivas] In some cases, it may be useful for
proxies in the SIP signaling path to see all the messages pass between
the endpoints for the session. In that case it will add RECORD ROUTE.
If it don't want to be in the path, it will not add the RECORD ROUTE.

			plz anser

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