Subject: [Diffserv] Simulation code of RFC 2598 (EF PHB)

From: Jaeyoung Kim <[email-masked]>
Date: Tue, 14 Aug 2001 17:52:52 +0900

Hi, I'm just curious whether it is possible to obtain the simulation
program code written for RFC 2598, EF PHB. Has this been publicized ever?
I'd like to study the ns-2 implementation of EF PHBs.

Thanks in advance.
Jay Kim

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   \/   ** Jaeyoung Kim      Computer Science & Engineering, POSTECH, KOREA

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From: Kathleen Nichols <[email-masked]>
Date: Fri, 17 Aug 2001 14:59:47 -0700

I assume you are talking about the original version that Van 
Jacobson, Kedar Poduri and I wrote since I don't believe
there are any simulations of the 2598-bis stuff. Kedar has
made code available in the past, but we used a lot of
our own modifications to ns-2 because their TCP was inadequate
for our purposes. Unfortunately, we haven't really updated this.
We did give our code to the ns-2 people. This isn't really
mainstream for us anymore, particularly as the PHB we simulated
is no longer what's called "EF". Perhaps you could simulate
the 2598-bis EF?

This is probably marginal for the diffserv list since it
doesn't really concern an item in front of the WG. Perhaps
you should move further discussion to diffserv-interest?

	Kathie

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From: Steve Blake <[email-masked]>
Date: Fri, 17 Aug 2001 18:36:06 -0400

> is no longer what's called "EF". Perhaps you could simulate

Kathie,

Do you think that there is any packet scheduler that can support
the the RFC2598 behavior but cannot support the 2598-bis behavior?
Or vice versa?

I'm not trying to start another flame war, but my understanding was
that, irrespective of the math, each "camp" thought that there was a
core set of schedulers that supported their favorite behavior, and
those two sets of schedulers are (almost?) identical.

Regards,

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Steven L. Blake               <[email-masked]>
Ericsson IP Infrastructure                  (919)472-9913

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From: Kathleen Nichols <[email-masked]>
Date: Wed, 22 Aug 2001 16:26:53 -0700

Steve Blake wrote:
...
> the the RFC2598 behavior but cannot support the 2598-bis behavior?

If not, then it's hard to understand why there is a 2598-bis.

> those two sets of schedulers are (almost?) identical.

Let's see, here. First, my previous reply on this message was just to
let
the questioner know that our simulation code had been made available
before, but the caveats in trying to use that with "box standard ns-2"
and the fact that it *may* not be helpful with the 2598-bis PHB. I think
I can speak for Van and Kedar in that our purpose was to define the
behavior a packet marked in a particular way could expect when it was
processed by a node. This description of behavior was not to expect or
require a particular scheduler implementation. The major goal was a
bounded delay, bounded jitter per-domain behavior that could be
constructed
employing, among other things, network nodes configured to a certain
behavior. The per-hop behavior described by Joel Halpern's design team
can
be used to constuct such a PDB and I believe can be used to describe
the per-hop behaviors we simulated and reported on in the appendix of
rfc2598. I believe a wide range of schedulers can be configured to give
that per-hop behavior. I don't have any interest in implementing or
simulating
the 2598-bis PHB, so I can't speak to that topic.

I believe that most vendors have schedulers that can be configured to
give
a range of per-hop behaviors, the first goal of diffserv (as you well
know!). 
My current diffserv interests are focused on PDBs, or what one can do
now that
the basic diffserv building blocks are available.

	Kathie