From: Paul Dardinski (pauld@marshallcomm.com)
Date: Sun Jul 22 2007 - 07:39:45 ART
John,
QoS is not designed to protect against packet loss. It's only purpose is
to ensure preferential treatment of one packet type over another in the
area of latency, jitter or in the decision of which packet to drop in
the case of data overflow.
Data overflow is not a generally a function of a well designed router or
switch. QoS is not there to repair an overutilized CPU. Data overflow is
most often derived from temporary oversubscription of a link, hence the
need for QoS. If a link if regularly oversubscribed, then all the QoS in
the world won't fix it, the pipe has to be made larger.
Network hardware is designed for certain throughput capacities defined
by the manufacturer. Generally they are designed with the capacities of
the possible ports allowed in the box as much as possible (ie. switches
should be nonblocking across the backplane up to the capacity of traffic
they are rated for). The core CPU as you had mentioned often handles the
backplane throughput. Most enterprise equipment today uses distributed
architectures allowing multiple CPU's across the architecture, each with
defined tasks to ensure that processing and serialization are minimized
as much as possible. QoS queuing purpose is to have a place to hold
traffic for differentiation and availability, not to compensate for the
CPU.
PD (#16842
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
johngibson1541@yahoo.com
Sent: Saturday, July 21, 2007 11:25 PM
To: ccielab@groupstudy.com
Subject: Re: We want to prevent packet lost? But TCP needs packet lost.
Even smarter these people. The TCP protocol is designed to
have packet lost. And they can just come up with more and more
sophisticated queues every month to "prevent packet lost".
It is designed to have packet lost, and they come to their
work every day to "prevent packet lost". How smart is that.
They will never need to create any thing and they have
a job guaranteed for life.
This is like the lawyers working with law makers to come up
with more sophisticated forms to do the same thing every
month so that citizens need lawyers.
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