Traffic Shape or Rate Limit

Tue Oct 2 20:12:20 UTC 2001

Although very similar, both shaping and limiting are designed to do separate
functions, and could in fact operate together.

Generally speaking, shaping uses a queuing mechanism to "delay" flows that
do not meet predefined bandwidth parameters.  Shaping attempts to keep your
average throughput the same, giving you a more predictable flow.

Rate limiting is a little more rudimentary with respect to policing traffic
flows.  When packets exceed bandwidth thresdholds defined, the router makes
a decision to 1) lower the priority of packets that have exceeded the
threshold, or 2) discard the packet.

You can actually utilize both technologies in your network.  Policing could
be done inbound or outbound and shaping could be done on outbound
interfaces.  Shaping is usually a little more forgiving with respect to
bursy traffic flows, however, queueing is introduced that may introduce
additional delays.

So, I think the answer is, it depends.  It depends on where you are in the
network, edge vs. core, and giving up processing/delay vs. overall
throughput.

My 2 cents worth,

Brad

-----Original Message-----
From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu]On Behalf Of
Christopher J. Wolff
Sent: Tuesday, October 02, 2001 11:36 AM
To: nanog at merit.edu
Subject: Traffic Shape or Rate Limit

Hello,

I'm wondering what the list's opinions are on Traffic-Shaping vs. Rate-Limit
for DIA customers (Frac DS3, for example).  From what I've read, Traffic
Shaping is a better option since it doesn't drop packets.  Just curious as
to what the opinions are.

Regards,
Christopher J. Wolff, VP, CIO
Broadband Laboratories, Inc.
http://www.bblabs.com
email:chris at bblabs.com
phone:520.622.4338 x234