From: Nick Shah (nshah@xxxxxxxxxxxxxx)
Date: Mon May 13 2002 - 01:54:41 GMT-3
Correction & Apologies(my answer was incorrect)... but this is what I found
in the archives, It has come from Patrick @ cisco systems. It seems to make
more sense when you read thru it...
----Pat's original mail----
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
//snip//
Nick
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.
-----Original Message-----
From: Bezverkhi, Serguei <Serguei.Bezverkhi@hp.com>
To: Michael Kilpatrick <mjkilpat@yahoo.com>
Cc: ccielab@groupstudy.com <ccielab@groupstudy.com>
Date: Monday, 13 May 2002 1:43
Subject: RE: Generic Traffic Shaping - Fatkid Lab #461
>Hello,
>
>I think this should meet the requirements
>
>traffic-shape group 101 16000 2000 14000
>
>16000 it is CIR, so we guarantee 16kb
>2000 it is Bc, just number of bit sent
>14000 it is Be, so it can burst up to 30kbps but no more, and even after
>30kb burst it will be able to send 16kbps.
>
>What do you think about this calculations??
>
>Serguei
>
>-----Original Message-----
>From: Michael Kilpatrick [mailto:mjkilpat@yahoo.com]
>Sent: May 12, 2002 8:43 PM
>To: ccielab@groupstudy.com
>Subject: Generic Traffic Shaping - Fatkid Lab #461
>
>
>In Fatkid Lab #461, can someone please verify the given solution for
>item #5.
>
>Item #5 says:
>5. Configure R3 so that users on the Token Ring segment get at least 16K
>of bandwidth, but not more than 32K, for their telnet traffic, and the
>remaining bandwidth for everything else.
>
>And the given solution is:
>interface Serial0
> traffic-shape group 101 16000 32000 32000 1000
>access-list 101 permit tcp any any eq telnet
>
>Please correct me if I am wrong, but it seems to me that this does
>nothing to guarantee users get at least 16K of bandwidth. In addition,
>this traffic-shape command would allow bursts up to the 64k access-rate
>and would apply a tc interval of 2 seconds which would be very
>inefficient.
>
>I think the solution should read:
>interface Serial 0
> custom-queue-list 1
> traffic-shape group 101 32000 4000 0
>access-list 101 permit tcp any any eq telnet
>queue-list 1 protocol ip 1 tcp telnet
>queue-list 1 default 2
>queue-list 1 queue 1 byte-count 100
>queue-list 1 queue 2 byte-count 300
>
>Can someone please verify?
>Thanks alot! Mike
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:58:55 GMT-3