Re: Question regard output of data from router TX-Ring and qos

From: Pavel Bykov (slidersv@gmail.com)
Date: Mon Mar 30 2009 - 17:40:52 ART

Eshedalonie, first you need to think what is sending to whom, using which
protocol, and so on. Only then you will see that network only enables this
communication with some restrictions.
You first need to understand TCP before going more into buffers and
interface speeds.

Interface always operates at it's speed. So in case of 100Mbps interface it
will send data only at this speed.
But it doesn't mean it has to send data, otherwise it will explode... No, it
can send a packet at mentioned 100Mbps speed, then wait for quite some time
before another packet arrives, and then send it again, therefore over time
the speed averages out to a much lower one.

Tx-ring is there mainly to improve hardware functionality and make interface
less dependant on CPU. Interface can send packets directly from tx_ring
without waiting for CPU.
Tx-ring legth is usually said in packets. But "packets" in this terminology
are actually 200-byte cells, I believe, and therefore a 64-byte packet is
one cell, and 200-byte packet is one cell, but 1500-byte packet is 8 cells.
It would be great if someone had more info regardingto what IOS considers a
"packet".

2009/3/27 WW)W WWWW W <eshedalonie@gmail.com>

> Does It Mean I can Send in one second Full 100 Mbits ?
> How much Bytes/Data/Packets will be send in one milisecond - if tx-ring is
> configured for 15 ?
> How much Bytes/Data/Packets will be send in one Second ?
>
> Does it mean regard my topolgy I Have mentioned - that there could be drops
> due to bursty applications in the Service Provider - because it gives me
> only 4 Mbits line
>
> And Then I Need to use Parent Qos Shaping + Child Qos for LLQ ?
>
>
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--
Pavel Bykov
----------------
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