From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Wed Apr 04 2007 - 16:50:00 ART
The point of the output queue is to have packets contend to be
sent to the transmit ring. As the queue depth of the transmit ring
increases as does the minimum latency a priority packet will receive in
the output queue while waiting for admission to the transmit ring.
For example suppose that you have a 64K VoIP packet that has
been prioritized and sent to the front of the output queue as soon as it
was admitted. If there are 10 packets sitting on the transmit ring
waiting to be FIFO dequeued more latency will be incurred as opposed to
there being only 1 packet on the transmit ring (assuming comparable
packet sizes). Therefore by setting the queue depth of the transmit
ring to one, in conjunction with fragmentation, you can minimize and
calculate exactly what is the maximum worst case latency a priority
packet will get while waiting to be admitted to the transmit ring.
HTH,
Brian McGahan, CCIE #8593 (R&S/SP)
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
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-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
johngibson1541@yahoo.com
Sent: Wednesday, April 04, 2007 12:53 PM
To: ccielab@groupstudy.com
Subject: Re: definition of
The Tx ring is always FIFO and have no special treatment for any
packets.
I remember a ciscopress book says something like "to have better use of
LLQ
and better control over packet treatment, set Tx ring depth to as small
as possible".
When Tx ring depth is 1 (the smallest possible), doesn't that mean the
interface is always "congested" by the functional definition (Tx ring is
full)
when the interface is sending packets then? When the interface is always
congested when it is at work doesn't matter how fast packets are
arriving
why do we need to define a time of congestion? I am totally lost.
This archive was generated by hypermail 2.1.4 : Tue May 01 2007 - 08:28:34 ART