Connection Sharing in MSRP

Hi All,

With Reference to draft-ietf-simple-message-sessions-2.txt

"When an MSRP endpoint wishes to send a request to a
peer identified by an  
MSRP URL, it first needs a transport connection, with the
appropriate  
security properties, to the host specified in the URL. If
the sender  
already has such a connection, that is, one associated with
the same host,  
port, and URL scheme, then it SHOULD reuse that
connection."

In this case,

If the Source Port, Target Port, Source IP, Traget IP and
security scehme  
of a particular connection matches it can be reused.

Hence same connection can be used by 2 or more sessions each
of them  
having differnt Session IDs.

My doubt here is when does such a scenario arise? The msrp
URLs are given  
by SDP. The SDP doesnt reuse the same port in the MSRP URL
when it is  
already in Use.

Can you please help me on understanding the scenario when
MSRP
Connection sharing may occur.

Regds,
Sudha
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On Feb 6, 2006, at 9:07 AM, Sudha wrote:

> Hi All,
>
> With Reference to
draft-ietf-simple-message-sessions-2.txt

First, you are looking at a very old draft--the current one
is draft- 
ietf-simple-message-sessions-13. A version 14 will be coming
out  
shortly, but I do not expect it to contain any substantive
changes.

>
> "When an MSRP endpoint wishes to send a request to
a peer  
> identified by an MSRP URL, it first needs a transport
connection,  
> with the appropriate security properties, to the host
specified in  
> the URL. If the sender already has such a connection,
that is, one  
> associated with the same host, port, and URL scheme,
then it SHOULD  
> reuse that connection."
>
> In this case,
>
> If the Source Port, Target Port, Source IP, Traget IP
and security  
> scehme of a particular connection matches it can be
reused.
>
> Hence same connection can be used by 2 or more sessions
each of  
> them having differnt Session IDs.
>
> My doubt here is when does such a scenario arise? The
msrp URLs are  
> given by SDP. The SDP doesnt reuse the same port in the
MSRP URL  
> when it is already in Use.
>
> Can you please help me on understanding the scenario
when MSRP
> Connection sharing may occur.

The SDP certainly can reuse the same MSRP port if an
implementation  
chooses to do so. But the real use of this is for when
relays are  
involved. You could have any number of MSRP sessions with
multiple  
peers going across the same outbound relay. In this case,
you should  
not create a separate TCP connection to that relay for each
of the  
sessions. This is even more true for connections between an
adjacent  
pair of relays that may carry any number of active sessions.

Hope this helps.

Ben.


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