From: HP-France,ex2 ("SANCHEZ-MONGE,ANTONIO)
Date: Wed Apr 21 2004 - 05:17:54 GMT-3
Hi William,
Shaping takes place BEFORE. The shaping algorithm buffers all the packets
that exceeded the CIR up to the "shape max-buffers" value. The packets that
are within the CIR are scheduled.
If the interface is not congested, the packets are then sent rightaway. If
it is congested, the fair queue algorithm takes place and the "queue limit"
controls how many packets can be buffered by the scheduler.
For example, imagine you want to shape a flow to 64kbps in a T1 interface.
The T1 interface can have its buffers completely free, so "queue limit" will
never kick in. If the real flow for that class is 128kbps, the "shape
max-buffers" will control the packets queued by the shaping engine.
On the other hand, if you configure "bandwidth 1544" for an interface whose
real line rate is 64kbps, you shape a class to 256kbps, and the real traffic
flow for that class is 128kbps, the shaping engine will let all go through,
but the scheduler will have to drop at least 50% of the incoming packets as
soon as "queue limit" kicks in.
Cheers,
Ato.
-----Original Message-----
From: William Chen [mailto:kwchen@netvigator.com]
Sent: miircoles, 21 de abril de 2004 2:47
To: ccielab@groupstudy.com
Subject: Traffic Shaping Buffer.
Dear all,
I understand that the command "shape max-buffers xxx" is using in a
CB-Shaping to configure the maximum number of packets will be queued in the
shaping buffer. However, what is the difference of the command with
"queue-limit'? For example:
policy-map testing
class class-default
shape average 128000
shape max-buffers 2048
fair-queue
queue-limit 256
R5#sh policy-map testing
Policy Map testing
Class class-default
Traffic Shaping
Average Rate Traffic Shaping
CIR 128000 (bps) Max. Buffers Limit 2048 (Packets)
Weighted Fair Queueing
Flow based Fair Queueing Max Threshold 256 (packets)
Then, how many packets are allowed to be buffered? 256 or 2048?
Moreover, is there any command to do the similar in GTS?
Best Regards,
William Chen
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