Subject: [bmwg] Comments on Terminology for Benchmarking Network-layer Traffic Co ntrol Mechanisms

From: "Uyeshiro, Robin" <[email-masked]>
Date: Wed, 28 Feb 2001 17:55:04 -1000

Jerry,

This is a valuable ID.  Very timely and nicely done, I think.

I have some minor comments on specific sections of the ID:

In section 3.5 Congestion, it seems to me that the last sentence of the
Discussion is a better definition than what is under the Definition.  It is
broader since it defines congestion in terms of the whole device, rather
than just the egress interfaces of the device.  Also, the discussion brought
an interesting point to light: should delay be considered when declaring
congestion?  A device with infinite storage would never drop a packet (and
therefore is never congested?), but the delay could be infinite.

In section 3.6 Congestion Management, would it be helpful to give some
examples of congestion management (e.g. RED, ingress policing/shaping,
explicit congestion notification, TCP congestion behavior) and maybe
categorize them under avoidance or control?

In section 3.7 Delay, it might make sense to define average or min/max delay
also, as is done for jitter.

In section 3.9 Flow, there may be an exception to all packets of a flow
entering on the same ingress interface and exiting on the same egress
interface: redundant links with load balancing. Also multiple links like IMA
or MLPPP, perhaps.

In section 3.10 Jitter, lost packets are not counted in the jitter
measurement.  An issue came up in the IPPM working group list about how late
a packet can be before being considered lost.  As I understand it, jitter is
mostly an issue for media streams where jitter buffers must be sized, and
media streams often must discard packets later than some threshold because
the device cannot wait for it.  Though this may never get into the
definition, maybe some mention of it in the discussion is possible?

In section 3.12 Offered Load Vector, under the Issues heading, it seesm to
me that peak rate should be an issue only if variable rate or variable size
packets are offered.  I was under the impression that most BMWG tests used
periodic fixed size packets, as the tests were more deterministic and
repeatable.  Maybe this won't be much of an issue?

That's all,
Robin Uyeshiro
Adtech/Spirent