Subject: Re: [Diffserv] Assured Rate PDB

From: Larry Ayres <[email-masked]>
Date: Fri, 05 Jan 2001 13:30:11 -0800

I have some more fundamental misgivings about this draft.

The reason for the Assured Rate PDB is for "traffic aggregates that require
rate assurance but do not require delay and jitter bounds"; which is a
noble cause. However, as delay and jitter increase, depending on link
speed, it may become impossible to assure the rate (depending on the time
interval allowed for averaging the rate). Given fairly long time intervals
for rate measurement, it may be possible to assure a rate on a packet
stream with delay and jitter, as long as the delay and jitter times are
less than the measuring interval and the link speed is sufficient to accept
the traffic.

It would seem to be necessary to state some basic time relationships. I see
that these are touched upon in section 7.0 Example Uses, but I am concerned
that they should be stated up front and the scope or limitations of what is
being proposed are explicit and well known.

It is still a noble cause.

Larry Ayres

---------------------------------------------------------
Lawrence Ayres
Principle Software Engineer

Ericsson Datacom, Inc
IP Network Edge & Access Product Unit
Data Backbone and Optical Networks
70 Castilian Drive
Santa Barbara, CA 93117
[email-masked]
Phone: 805-562-6656
---------------------------------------------------------

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From: demir <[email-masked]>
Date: Fri, 5 Jan 2001 17:14:28 -0800 (PST)

I don't understand why this is a "fundamental misgiving". Isn't it a
general problem related to "measurement" and "traffic"? The rate is
protected by a minimum configured rate and in global, by "assumption".
Am I missing something?

Alper K. Demir

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From: Brian E Carpenter <[email-masked]>
Date: Mon, 08 Jan 2001 09:03:41 -0600

I've always understood that these were exactly the things we *don't * worry
about in AF, and therefore in PDBs based on AF. These are the things we just
spent 6 months debating with respect to EF, and we know how easy that was.

  Brian

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From: Scott Brim <[email-masked]>
Date: Mon, 8 Jan 2001 16:10:55 -0500

I'm preaching to the choir, but it's possible to build various PDBs with
various PHBs, e.g. it MIGHT be possible to build time-sensitive PDBs
using AF, therefore a statement about time sensitivity or the lack
thereof might be useful.

...Scott

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From: Juha Heinanen <[email-masked]>
Date: Tue, 9 Jan 2001 00:05:21 +0200 (EET)

> using AF, therefore a statement about time sensitivity or the lack

i agree and what comes to ar pdb, it is the "lack of" time sensitivity
that characterized the pdb.  even if there might be a relationship
between rate and delay, the ar pdb doesn't care about it.

-- juha