From: Montgomery, Jerry (jerry.montgomery@eds.com)
Date: Tue Jul 11 2006 - 12:41:42 ART
Good morning, Chris,
What is the main difference between shape average and shape peak?
I am trying to answer the following scenario:
Limit all traffic leaving FA0/0 with IP Precedence of 128K. Do not use
policing or rate-limiting.
Sometimes I convince myself that "shape average 128000 16000 0" is the
answer (assuming Tc=125ms). And then sometimes I convince myself that
"shape peak 128000" is the answer (default to Bc and Be).
Any inside as to what the difference between "shape average" and "shape
peak" are?
Also, can you send me a link regarding Be being sent in addition to Bc
on the first interval of a second only? I did not find that information
explicitly stated.
Thanks in advance.
Respectfully,
Jerry Montgomery
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Chris Lewis
Sent: Wednesday, July 05, 2006 9:27 AM
To: Joe Gagznos
Cc: ccielab@groupstudy.com
Subject: Re: Shaping Average / Peak vs. Policing
Shape average does not allow Bc + Be to be sent every interval.
Shape average allows Be to be sent in addition to Bc on the first
interval of a second only, also the shaper needs to have built up credit
in previous intervals to use Be. The effect of Be in shape average is to
allow the shaper to achieve CIR over a long period of time,
accommodating periods of lull where less than CIR is sent in one second,
with an additional Be amount of data in a later period should the credit
be available and the shaper needing to send more data.
Chris
On 7/4/06, Joe Gagznos <joegagznos@comcast.net> wrote:
>
> 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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