Subject: [Ieprep] SIP and Resource Reservation

From: "King, Kimberly S." <[email-masked]>
Date: Mon, 9 Dec 2002 16:48:40 -0500

Ayyasamy, Senthilkumar said:

>No Dial tone = No connection (PSTN) 
>Welcome to the world of SIP, where you get dial tone but still
>remain disconnected. This is due to the interesting concept of 
>separation of session establishment and resource reservation in
>SIP based systems. If for some reason the resource reservation 
>fails, the call will be set up even though network doesnt support.

Resource reservation is not typically supported for SIP systems running over
the Internet.  Instead, there is a graceful degradation for all callers over
a congested link rather than a complete inability to achieve a connection.
As we have talked about (and I believe agreed to!), congested links
typically occur in access links and congestion is not much of an issue in
core U.S. ISPs.

Kimberly
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From: "Ayyasamy, Senthilkumar (UMKC-Student)" <[email-masked]>
Date: Mon, 9 Dec 2002 16:08:03 -0600

> Resource reservation is not typically supported for SIP 
> systems running over  the Internet. Instead, there is a 
> graceful degradation for  all callers over  a congested link rather 
> than a complete inability to achieve  a connection.
> typically occur in access links and congestion is not much of 
> an issue in  core U.S. ISPs.

I completely agree. I used that as an example to explain that their 
may be situations where dial tone doesn't always mean connection is
ok ( as in PSTN.) Also, the assumption being using RSVP for resource 
reservation. Try reading RFC 3312. 

( Note: I did not consider any deployment feasibility for this 
example.) 
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