From: Charles Church (cchurch@wamnet.com)
Date: Mon Apr 07 2003 - 23:27:41 GMT-3
Anthony,
"Policing it coming in" will help for many applications, particularly
anything TCP based. Think about it. An incoming datagram is dropped. The
receiving station doesn't receive it, so it waits. The sender also waits
for an ACK. This second or so of waiting can save a ton of bandwidth if you
multiply it by dozens or hundreds of individual flows. It won't show much
of an improvement in a hopeless situation like a congested 56 kb circuit,
but for a T1 and above that can handle many flows at once, it'll help a
bunch. I've used NBAR to rate limit file-sharing apps inbound at a college.
The circuit usage dropped about 70% over the course of a month. Use NBAR
protocol-discovery on the internet interface, and rate limit what you deem
as less-critical. It'll take some experimentation, but it really works.
HTH,
Chuck Church
CCIE #8776, MCNE, MCSE
Wam!Net Government Services
13665 Dulles Technology Dr. Ste 250
Herndon, VA 20171
Office: 703-480-2569
Cell: 585-233-2706
cchurch@wamnet.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Anthony Pace
Sent: Monday, April 07, 2003 9:01 PM
To: ccielab@groupstudy.com
Subject: QOS, traffic policing and shaping (real-world)
I have a sort of generic real world question about traffic engineering.
How can you control the bursty traffic on a connection to the Internet
(or anywhere) when the EGRESS traffic is relatively light compared to the
massive amount of traffic coming back. In this scenario we don't control
the upstream (PROVIDER) router.
- "Police it coming in" won't help as it has already done it's damage by
consuming the link
- "Shape it going out" won't help because the "requests" are not
bandwidth intensive, and queuing never really kicks in; unless the
outbound traffic begins to fill the queue (which it doesn't).
I have used traffic-policing in the past to control a customers INGRESS
traffic, as it leaves their spoke destined for the HUB, stopping them
from getting more bandwidth than they paid for. I have also worked
through the countless traffic shaping and QOS labs for CCIE, and read all
the examples on this in books, where we are asked to divide the bandwidth
up by managing who gets dropped out of the queue as their packets are
waiting to be put on the wire.
Does this question make sense? I don't see the Asymmetrical nature of
Internet or Client/Server traffic addressed in any of the books I have or
on CCO. It is seems like everyone is always more obsessed with the "exact
byte count in the queues".
Anthony Pace CCIE 10349
-- Anthony Pace anthonypace@fastmail.fm-- http://www.fastmail.fm - The way an email service should be
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