From: Pat Bodin (pbodin@xxxxxxxxx)
Date: Sat Apr 28 2001 - 13:15:16 GMT-3
This should help!
Terminology:
Tc = Bc/Cir ! time interval (the internalized version of Tc where the
time interval can't exceed 125ms)
CIR = Average rate you want to send out (This is generally not the
same as the CIR you get from your provider unless you aren't
allowed to send above CIR) This is measured in bits/second.
Bc = Amount of data to send per each Tc interval. This is
measured in bits.
(this also gets internalized and real amount of data sent per
interval is expressed in bytes by the "increment" variable).
Be = Amount of excess data allowed to be sent during first
interval once credit is built up. Also measured in bits.
Mincir = Minimum amount of data to be sent during periods of congestion.
This defaults to half of CIR.
Interval = Bc/CIR with the maximum size being 125ms.
byte increment = Bc/8 . Must be > 125. Upper side has no bound
or limitation except if interval is locked at 125ms.
limit = byte increment + Be/8 (measured in bytes)
--------------------------------------------------------------------
OK let me throw some numbers in which may help explain this better.
Let's say you have a frame relay link with following parameters:
Physical port speed 64KB
CIR = 16KB (In this case I mean CIR your provider has guarenteed
you in their network)
Now let's say your provider has told you that you can send data on your PVC
up to port speed as long as there is no congestion in their network but that
when there is congestion they will only guarantee you CIR on your PVC.
Here is what you should configure on the router:
encap frame-relay
ip address 10.10.10.1 255.255.255.0
frame-relay traffic-shaping
frame-relay map ip 10.10.10.2 200 broadcast
frame-relay interface-dlci 200
class 64KB
map-class frame-relay 64KB
frame-relay cir 64000 ! This is rate you want to normally send at
when
there is no congestion
frame-relay bc 8000 ! This is amount you will send per interval.
rule of thumb is to make it 1/8 CIR
frame-relay be 0 ! This is extra amount to send in first
interval. In this case you are already
sending at port speed so this should be 0.
frame-relay mincir 16000 ! This is what you will slow down to during
congestion. This should be set to your true
CIR that your provider has guarenteed you
when
there is congestion in their network
*Note that BECN Response(ie dropping down when receiving BECNs) is
enabled by default in 11.2
Now here are a couple of other numbers that are used in traffic shaping:
Tc= Bc/CIR where Tc is the measurement interval. This value should
be no larger than 1/8 second for good shaping to take affect.
So in above example Tc = 8K/64K = 1/8 second
So basically here is what you would see transmitted in 1/8 second intervals:
8000(Bc+Be), 8000(Bc), 8000, 8000, 8000, 8000, 8000, 8000
which equals 64000bits/second.
Now if you actually had a 128KB port speed but you left all numbers the same
except you changed Be = 64000 then here is what you would see.
72000, 8000, 8000, 8000 ....
You would keep sending at Bc(8000) until you had an idle interval or only a
partially used interval and you built up credit again. The maximum credit
you
can build up is Be.
Here are some show commands that you can use to see these numbers:
interface Serial5/1:1
ip address 10.10.10.1 255.255.255.0
encapsulation frame-relay
no ip mroute-cache
frame-relay traffic-shaping
frame-relay interface-dlci 50
class test
map-class frame-relay test
frame-relay adaptive-shaping becn
frame-relay cir 64000
frame-relay bc 8000
frame-relay be 72000
frame-relay mincir 16000
wan-7507a#sh fr pvc 50
PVC Statistics for interface Serial5/1:1 (Frame Relay DTE)
DLCI = 50, DLCI USAGE = LOCAL, PVC STATUS = INACTIVE, INTERFACE =
Serial5/1:1
input pkts 0 output pkts 0 in bytes 0
out bytes 0 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 0 out bcast bytes 0
Shaping adapts to BECN
pvc create time 23:34:33, last time pvc status changed 23:34:33
cir 64000 bc 8000 be 72000 limit 10000 interval 125
mincir 16000 byte increment 1000 BECN response yes
pkts 0 bytes 0 pkts delayed 0 bytes delayed 0
shaping inactive
Serial5/1:1 dlci 50 is first come first serve default queueing
Output queue 0/40, 0 drop, 0 dequeued
wan-7507a#sh traffic-shape
Access Target Byte Sustain Excess Interval Increment Adapt
I/F List Rate Limit bits/int bits/int (ms) (bytes) Active
Se5/1:1 64000 10000 8000 72000 125 1000 BECN
wan-7507a#sh traffic-shape statistics
Access Queue Packets Bytes Packets Bytes Shaping
I/F List Depth Delayed Delayed Active
Se5/1:1 0 0 0 0 0 no
wan-7507a#
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
JAY
Sent: Saturday, April 28, 2001 9:21 PM
To: ccielab@groupstudy.com
Subject: Frame-Relay traffic shaping
How do accomplish the task below?
Frame port speed is 64K, CIR is 16K. Make the Frame cloud aware of this and
set the Bc bit to 1/8th of the speed that you would want traffic to flow if
there were no congestion in the Frame cloud.
-TIA-
JAY
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