Subject: How to calculate the actual delay when signaling QoS

From: shen jing <[email-masked]>
Date: Fri, 11 May 2001 20:14:42 +0800

Dear sir/madam:

If the question following is stupid, forgive me please.

As providing a QoS enabled service over internet,  signaling the remote
end along the path calcultated is needed. As I know  RSVP is the
possible solution.

My question is:  the signaling procedure only consider the
bandwidth needed, real transmission dely and jitter can  not be got when

calculating a explicit path, right?

What I want to ask is: is  there any method proposed to solve this
question? In a multicast situation, how to adjust the behavior when
a new member join the multicast tree and request a high QoS level to
server ?

 And would you please tell me any site where  documents on this
subject can be found?

Jame Shen

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From: David Charlap <[email-masked]>
Date: Fri, 11 May 2001 10:03:02 -0400

shen jing wrote:
> bandwidth needed, real transmission dely and jitter can  not be
> got when calculating a explicit path, right?

And it doesn't matter because none of the three MPLS signaling protocols
let you make delay/jitter-based reservations.

-- David

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From: Philip Chen <[email-masked]>
Date: Fri, 11 May 2001 10:43:53 -0400

> calculating a explicit path, right?

Yes, the current RSVP signaling protocol only considers bandwidth. But that
does not mean an explicit path calculation cannot take into consideration of
delays (not only transmission delay, but rather an end-to-end delay) and
delay jitters. In general, path delays and jitters are difficult to
determine, as they depend on many things, such as physical media length,
link capacity, buffering/queuing delay etc... A few researches have shown
that under certain assumptions, delay/jitter requirements can be converted
into equivalent bandwidth requirement. This can be done by the explicit
route calculating node and then use this equivalent bandwidth to calculate
the explicit routes and a signaling protocol like RSVP to reserve resources
along the explicit route path.

--Phil