Subject: RE: [mediactrl] draft-boulton-sip-control-framework-00

From: "Chris Boulton" <[email-masked]>
Date: Mon, 30 Jan 2006 16:01:25 GMT

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>OK – before I start this reply –
I would like to point out that I am in no way an authority on RTSP.  It
would be really cool if someone with more knowledge in this area could
contribute.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'> 

<span
style='font-size:10.0pt;font-family:Arial'>Greetings,

<span
style='font-size:10.0pt;font-family:Arial'> 

<span
style='font-size:10.0pt;font-family:Arial'>I am investigating the use of SIP
and a control protocol for management of media. The basic functions I need are
typical VCR-like control (play/pause/…) but I also will need other
primitives (like camera control). I have been working through scenarios of how
to use SIP to negotiate the SDP, in which one media is a control channel which
in turn runs RTSP.

<span
style='font-size:10.0pt;font-family:Arial'> 

<span
style='font-size:10.0pt;font-family:Arial'>It occurs to me that one could use
this framework to base a control package to accomplish the VCR-like control.
RTSP-lite anyone?

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face=Arial> 

<span
style='font-size:10.0pt;font-family:Arial;color:navy;font-weight:bold;
font-style:italic'>[Chris Boulton] Certainly the framework provides the ability
to create ‘Control’ typed commands and receive feedback at a later
point (or immediately) on the success failure of the operation.  

<span style='font-size:
10.0pt;font-family:Arial;color:navy'> 

<span
style='font-size:10.0pt;font-family:Arial'>My question is, has anyone thought
about how such a control package might relate to a protocol like RTSP? 

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face=Arial> 

<span
style='font-size:10.0pt;font-family:Arial;color:navy;font-weight:bold;
font-style:italic'>[Chris Boulton] I would imagine that no-one has as this
framework is particularly new.  As the framework is generic it allows for any
specified set of control commands and responses to be specified.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'> 

<span
style='font-size:10.0pt;font-family:Arial'>In particular, I appreciate the
section relating this to COMEDIA and the potential that an external server may
initiate the TCP connection. I think this will help in a wide variety of NAT
scenarios (for example, if the media server is behind a NAT). One item that I
am thinking through is how this might work in practice. If the client sends in
its SDP (a=setup:passive<CRLF>a=connection:new), and subsequently the
server initiates the control connection back to the client, how is the client
to identify which server initiated the TCP connection (assume it was setting
two of these up in parallel)?

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face=Arial> 

<span
style='font-size:10.0pt;font-family:Arial;color:navy;font-weight:bold;
font-style:italic'>[Chris Boulton] Very good question and one we need to think
about for the next revision.  The identification of connecting clients
etc. is certainly planned for the 01 release which will be published soon.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'> 

<span
style='font-size:10.0pt;font-family:Arial'>Thanks in advance for any thoughts
on this…

<span
style='font-size:10.0pt;font-family:Arial'> 

<span
style='font-size:10.0pt;font-family:Arial'>Rob Hagens

<span
style='font-size:10.0pt;font-family:Arial'>Envysion

<span
style='font-size:10.0pt;font-family:Arial'> 

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