Subject: [SIP] Reply Requested Immediately Please

From: Sameer sheth <[email-masked]>
Date: Thu, 17 May 2001 13:07:41 +0530

Respected Sir

	I have a few very basic queries regarding the SIP protocol, like 

1) Who controls the voice when it is transmitted over the network.?

2) What is the main purpose of User Agent in SIP ?

3) Through SIP we can switch between various devices like PDA, Mobile, etc..
can we make a voice call to an ordinary PSTN phone ?
if yes how does the entire process work ?

4) What are the various voice channel in SIP?

5) Can we transmit data and voice at the same time ? (i.e.) I wish to
transmit the voice as well images to an mobile device which is 
connected to the SIP Server ?

6) Where should the SIP User Agent reside ?

7) Please explain in detail regarding USER AGENT.

8) How much does a SIP Server , User Agent and Proxy Server cost ?

	I would appreciate if you could send me any basic information
regarding SIP, I am sure by going through the above questions you would have
understood that I am trying to get hold of SIP core working. I have
downloaded SIP RFCs, and have gone through faq which is located at
http://www.cs.columbia.edu/~hgs/sip/faq/cache/1.html. 

	If there is any other URLs located on the web that you feel will
help me better understand the technical detail and the working of SIP then
please do let me know. I hope to hear from you soon. Please reply as soon as
possible. 

Thank you

Regards
> -----------------------------------
> Sameer.Sheth
> Analysts
> Justvox ---> We(b) Speak, Your Way
> T/F: +91-422-446127 / 456753 
> 
> 

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---

From: "Ranjit Avasarala" <[email-masked]>
Date: Mon, 21 May 2001 13:07:37 -0500

sameer see my comments inline...

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

----- Original Message -----
From: Sameer sheth <[email-masked]>
To: <[email-masked]>
Sent: Thursday, May 17, 2001 2:37 AM
Subject: [SIP] Reply Requested Immediately Please

Respected Sir

like u transmit voice thru audio channel ...i.e basically thru real time
protocol (RTP).

user agent is the client / server entity that transmit / receive audio /
video data.

yes you can make a voice call to a PSTN phone using SIP - PSTN gateway. to
switch between PDA, Mobile , first of all
u need have user agent softeware running in them.

there are no various vocie channel, but different codecs. like G.723, G.711,
etc.

yes. u can. like u need to open different sessions for that. like for audio
we have session id 1, for video session id 2 and for data
session id 3.

in the device say a IP phone. or mobile  or PC to which a telephone is
connected.

may be u could go to sip rfc for this ( RFC 2543)

check with rescpective vendors

go to http://www.sipcentre.com. or give a search in google.

Thank you

Regards