From: Colin Barber (Colin.Barber@xxxxxxxxxxxxxx)
Date: Wed Aug 28 2002 - 16:30:19 GMT-3
I think the confusion is:
can (BC+BE)/Tc be greater than AR as Jim is saying because the interface
will buffer the excess or
(BC+BE)/Tc <= AR because the burst has to be transmitted within one Tc
Your link states that the parameters control the rate of traffic onto the
interface but not onto the line so is the interface buffering any excess and
can you have a large excess?
To put it another way: if your CIR is less than the access speed of the
interface and you wish to burst to the full access speed, do you work out BE
so that the access rate is achieved only in the first Tc or the access rate
is achieved over a full second?
I think we need a vote on the two options - I'm for option 2
For example:
CIR = 64000
Access rate = 96000
Tc = 1/8th sec
BC=8000
To burst up to the AR what is the value of BE?
option 1 BC=32000 (8*BC)+BE = 96000
option 2 BC=4000 at one Tc BC+BE=12000*Tc = 96000
Colin
-----Original Message-----
From: Bauer, Rick [mailto:BAUERR@toysrus.com]
Sent: 28 August 2002 19:55
To: 'ccielab@groupstudy.com'
Subject: RE: I need FRTS help or review
This should help. The first couple of lines will answer your question in
regard to CIR, BE, BC.
http://www.cisco.com/warp/customer/125/21.shtml
Rick, #9482
-----Original Message-----
From: Volkov, Dmitry (Toronto - BCE) [mailto:dmitry_volkov@ca.ml.com]
Sent: Wednesday, August 28, 2002 2:07 PM
To: 'Jim Brown'; 'Colin Barber'; 'Omer Ansari'
Cc: 'ccielab@groupstudy.com'
Subject: RE: I need FRTS help or review
Jim,
You are right traffic will be delayed and sent within 9th Tc interval
(assuming Tc=1/8 sec).
But Be is still Be - it is number of bits, and Be+Bc =< Port Speed
(clocking) * Tc.
We have to put actual number in config.
40000 bits will not be transmitted during 1st Tc - only 12000 bits.
Other bits will be delayed until 9th Tc.
Be - number of bits will be transmitted within 1st Tc ==> be = 12000
-8000(Bc) = 4000 bits
and this number 4000 we have to put in config as Be. The other bits will be
delayed / dropped, whatever.
I'm not 100% sure about it, but I got this logic from CCO.
Colin right - the documentation on this subj is very unclear.
This subj is like religion for me - believe or not believe :)
Dmitry
> -----Original Message-----
> From: Jim Brown [mailto:Jim.Brown@caselogic.com]
> Sent: Wednesday, August 28, 2002 11:35 AM
> To: 'Colin Barber'; 'Omer Ansari'; 'ccielab@groupstudy.com'
> Subject: RE: I need FRTS help or review
>
>
> You do not necessarily need 320Kps available during the first
> interval. The
> packets are software queued before they are placed onto the
> TxRing. This is
> the whole idea behind shaping.
>
> They are not placed on the wire at exactly the same speed
> designated per TC
> interval.
>
> List, if I'm way off base please correct me and help me see the light.
>
> -----Original Message-----
> From: Colin Barber [mailto:Colin.Barber@telewest.co.uk]
> Sent: Wednesday, August 28, 2002 9:09 AM
> To: 'Omer Ansari'; 'ccielab@groupstudy.com'
> Subject: RE: I need FRTS help or review
>
>
> What's the access speed of the interface? If it's 96k then this is
> incorrect. In the first time slot BC+BE=40000. For that
> amount of data to be
> transferred in the first timeslot the access speed will need to be
> 40000*8=320kbps.
>
> Colin
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