From: Schulz, Dave (DSchulz@dpsciences.com)
Date: Wed Jul 05 2006 - 10:11:51 ART
Greetings, Joe. You also have the CAR options.... check, "rate-limit"
on the docCD.
Dave Schulz
Email: dschulz@dpsciences.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Joe Gagznos
Sent: Tuesday, July 04, 2006 8:44 PM
To: ccielab@groupstudy.com
Subject: Shaping Average / Peak vs. Policing
I am trying to find another way to limit outbound traffic through an
interface similar in manner to policing. I understand that functionally
the
two are different. With shaping you are going to be queuing excess
traffic
to a predetermined rate where with policing you are going to be
executing
some kind of action on traffic that exceeds the contract (usually
dropping).
For comparison purposes, I have configured shaping and policing on two
separate subinterfaces in the following manner:
interface Ethernet0/0.1
encapsulation dot1Q 10
ip address 10.1.1.1 255.255.255.0
service-policy output shape
interface Ethernet0/0.2
encapsulation dot1Q 20
ip address 10.1.2.1 255.255.255.0
service-policy output police
Both interfaces are configured to limit traffic to no more than 2.5 Mbps
as
follows:
policy-map police
class class-default
police 2500000 conform-action transmit exceed-action drop
policy-map shape
class class-default
shape average 2500000
What I find is that the shaping interface initializes the parameters as
follows:
R1#sh policy-map interface e0/0.1
Ethernet0/0.1
Service-policy output: shape
Class-map: class-default (match-any)
19 packets, 1729 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval
Increment
Rate Limit bits/int bits/int
(ms)
(bytes)
2500000/2500000 15000 60000 60000 24 7500
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 19 1729 0 0 no
A couple things to note here - Be is initialized to the same value as Bc
of
60000 (or 7500 bytes). The byte limit is 15000 bytes, though. This
must
mean that the byte limit is initialized to Bc+Be=15000. With a 24 ms
interval, does this mean that the interface will send 5 Mbps (15000 * 8
bits
/ byte * 1 sec/.024 = 5000000) instead of the contracted 2.5 Mbps? If
shape average is allowing the interface to transmit Bc+Be each interval,
then how does this differ from configuring shape peak which accomplishes
the
same thing?
With policing it appears that things are much more straightforward.
R1#sh policy-map int e0/0.2
Ethernet0/0.2
Service-policy output: police
Class-map: class-default (match-any)
107 packets, 7473 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
police:
cir 2500000 bps, bc 78125 bytes
conformed 63 packets, 4305 bytes; actions:
transmit
exceeded 0 packets, 0 bytes; actions:
drop
conformed 0 bps, exceed 0 bps
Thanks for any response!
Joe Gagznos
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