From: Chris Lewis (chrlewiscsco@yahoo.com)
Date: Fri Oct 07 2005 - 15:55:24 GMT-3
Dennis,
I think you overstate things a little in this reply.
Given that we are talking about shape average in an MQC policy-map, Bc and Be are in fact still used in the same way that the legacy Bc and Be were in the map-class configuration.
Looking at the following output from a router for the shape average command
Router2(config-pmap-c)#shape ?
adaptive Enable Traffic Shaping adaptation to BECN
average configure token bucket: CIR (bps) [Bc (bits) [Be (bits)]],
send out Bc only per interval
fecn-adapt Enable Traffic Shaping reflection of FECN as BECN
fr-voice-adapt Enable rate adjustment depending on voice presence
max-buffers Set Maximum Buffer Limit
peak configure token bucket: CIR (bps) [Bc (bits) [Be (bits)]],
send out Bc+Be per interval
The key thing to note is that if you type in shape average, you have the option to put in additional values as shown in the following output:
Router2(config-pmap-c)#shape average 16000 ?
<256-154400000> bits per interval, sustained. Needs to be multiple of 128.
Recommend not to configure it, the algorithm will find out
the best value
For sure you do not explicitly type in Bc, but if you type in a figure here, it specifies the bits per interval that will be used to achieve CIR, which is the definition of Bc. The formula CIR=Bc/Tc still holds for shape average. So just as in the legacy map-class configuration, if you are told to optimize to a given Tc value, you would configure a Bc value after shape average 16000 to set the Tc.
I don't actually understand the term "shape average traffic to CIR + Bc" Bc defines the number of bits transmitted per time interval to reach CIR.
As previously discussed, all shape peak does is allow Bc +Be to be transmitted each time interval.
Chris
"Dennis J. Hartmann" <dennisjhartmann@hotmail.com> wrote:
Bob: The Shape average command does not use either Bc or Be so
they're irrelevant. Shape average shapes traffic to CIR. Older version of
IOS (12.1) used to shape average traffic to CIR + Bc (even though IOS
documentation showed something different. 12.2 T code trains will shape
average traffic to CIR.
Where this does apply is with the Shape Peak command. The shape
peak command uses both Bc and Be using the formula "average rate (CIR) * Bc
/ Be". Since Bc and Be default to 8000, the formula is CIR * 2 which
results in twice the effective bandwidth over time (assuming wire rate
traffic at CIR * 2.
-Dennis Hartmann
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Bob
Sinclair
Sent: Wednesday, June 15, 2005 1:23 PM
To: Thomwin Chen; ccielab@groupstudy.com
Subject: Re: MQC-Based FRTS
Thomwin,
No, do not configure the command "frame-relay traffic-shaping" when doing
MQC-based shaping. When doing MQC-based shaping remember that the "shape
average" command automatically sets Be equal to Bc, so set Be explictly to 0
if the task does not require an excess burst. Also remember that if you
want to shape at the DLCI level, using a map-class frame-relay, then you
must shape class class-default.
HTH,
Bob Sinclair
CCIE #10427, CCSI 30427, CISSP
www.netmasterclass.net
----- Original Message -----
From: Thomwin Chen
To: ccielab@groupstudy.com
Sent: Wednesday, June 15, 2005 1:02 PM
Subject: MQC-Based FRTS
Hi All,
just want to confirm.
to configure MQC-Based FRTS, should I use frame-relay traffic-shaping
command in main interface ?
In CiscoDoc, MQC-Based FRTS don't have frame-relay traffic-shaping command
in main interface ??
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/12
2t/122t13/frqosmqc.htm
thanks
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