From: Chris Lewis (chrlewiscsco@yahoo.com)
Date: Fri Nov 04 2005 - 14:44:24 GMT-3
Similar in some ways, but different in others :)
The key issue that differentiates normal burst in rate-limit terminology from Bc in frame technology is when they deliver tokens to the bucket and that is driven by the basic difference between shaping and policing, that being that shaping can queue packets up, whereas policing drops.
I wrote a longish post on this at this link
http://www.groupstudy.com/archives/ccielab/200509/msg00978.html
The key issue to Leigh's question is for the legacy rate limit command. The two burst figures here are burst normal and burst max. burst normal is the figure you set, so that the policing function can reach line rate over the long term, if it does not transmit at CIR for a while. The burst max needs to be qual to or greater than the burst normal. If it is equal to, there is no burst above the average CIR, if it is greater than burst normal, it defines how much above CIR you can go if you have the credit.
The above link mainly references the MQC police command, but teh basic principles apply
Chris
Lee Donald <Lee.Donald@t-systems.co.uk> wrote:
Leigh,
NO, this means that your cir is 4mb. The BC and BE is what will be sent
should you build up any credit and the isp will agree to send the extra.
The BC and BE are on top of your cir.
Similar to Frame.
Regards
Lee.
-----Original Message-----
From: Leigh Harrison [mailto:ccileigh@gmail.com]
Sent: Friday, November 04, 2005 4:11 PM
To: Leigh Harrison
Cc: FORUM
Subject: Re: Rate-Limit - I just don't get it !!
To clarify,
I do get it a bit.
My understanding is that:-
Burst means "in chunks of"
i.e
rate-limit 4000000 500000 600000 conform transmit exceed drop
Does this mean "you can send you data up to 4 meg a second in chunks of
up to 500k, but no more than 600k"
If so - what's the point of the 600k ?!
LH
Leigh Harrison wrote:
> All,
>
> I'm having a hard time getting my head around some of the bits of
> QoS. No matter how much I read about it - it doesn't seem to sink in.
>
> I had a requirement to set the bandwidth on an incoming interface to 4
> meg.
>
> No problem I thought and did it thusly:-
>
> policy-map traffic_in
> class class-default
> police 4000000
>
> int f0/0
> service policy input traffic_in
>
> But then I thought to myself - hang on, what if in the lab I couldn't
> use a policy map, what else could I do? Ah-ha, I thought,
> Rate-Limiting. Then it hit me - I've no idea why there are so many
> variables for rate limiting!! To be honest - I think I'm going mad.
> I got quite angry with my telnet session when it wanted me to specify
> normal burst size and extended burst size.
>
> Could someone put this into simple(ton) terms for me?
>
> Many thanks in advance,
> LH
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