From: Wade Edwards (wade.edwards@xxxxxxxxxxxxxxxxxxx)
Date: Fri Feb 02 2001 - 13:19:15 GMT-3
I have read the URL you gave me and I still have some questions. Here is
something from that URL:
Rate limits define which packets conform or exceed based on the three
parameters: average rate, normal burst size, and excess burst size:
1 The average rate determines the long-term average transmission rate.
Traffic that falls under this rate will always conform.
2 The normal burst size determines how large traffic bursts can be before
some traffic exceeds the rate limit.
3 The excess burst size determines how large traffic bursts can be before
all traffic exceeds the rate limit.
Question about number 1 - What is meant by long-term average. Is that an
average for 1 second, 10 seconds, 10 minutes, 10 hours?
Question about number 2 and number 3 - Does the author mean bursts sizes
above the average rate or burst sizes during a given interval that are above
the average rate during that interval and what is that interval? Does the
interval change based upon the type of interface it is or is that interval
fixed for a router platform or IOS version?
Sorry to be such a pest but this just doesn't make sense to me and the
documentation does not explain it very well.
-----Original Message-----
From: dgoldsmi@cisco.com [mailto:dgoldsmi@cisco.com]
Sent: Friday, February 02, 2001 9:54 AM
To: Wade Edwards
Cc: Michael E. Flannagan; Robert DeVito; ccielab@groupstudy.com
Subject: Re: CAR question
Wade,
The rate-limit section.
Dave
http://www.cisco.com/univercd/cc/td/doc/product/software/ios111/cc111/car.ht
m#xtocid255427
Wade Edwards wrote:
> OK I am now confused. How are you getting 6.6 Mbps from the command
below.
>
> rate-limit input access-group 101 3000000 450000 500000 conform-action
> transmit exceed-action drop
>
> It should be 3 Mbps with a normal burst of .45 Mbps and a max burst at .5
> Mbps. Is the formula first number + second number is normal traffic and
> first number + second number + first number + third number is the max
burst
> rate? I don't understand what is meant by burst then. I thought normal
> burst was what you are given above the first number and still be within
your
> budget and max burst is what will be dropped.
>
> I am so confused about CAR now.
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Michael E. Flannagan
> Sent: Friday, February 02, 2001 8:55 AM
> To: David Goldsmith
> Cc: Robert DeVito; ccielab@groupstudy.com
> Subject: Re: CAR question
>
> Dave is exactly right...I love zeros - just got carried away :-)
>
> Sorry for the confusion.
>
> ------------------------------------------------------------
> C i s c o S y s t e m s Michael E. Flannagan
> | | Network Consulting Engineer
> ||| ||| Research Triangle Park, NC
> ||||||| ||||||| (919) 392-4550
> .:|||||||||||:.:|||||||||||:. mflannag@cisco.com
> ------------------------------------------------------------
>
> On Fri, 2 Feb 2001, David Goldsmith wrote:
>
> > Group,
> >
> > Actually, that is incorrect. This would allow 3mega bits for the first
> number
> > and 3.6 mega bits for the burst.
> >
> > the second number is in bytes. This statement will allow 6.6 M bits
> through.
> >
> > Thanks,
> > Dave
> >
> >
> > "Michael E. Flannagan" wrote:
> >
> > > Robert -
> > >
> > > Look at it this way. 1st number + 2nd number = where your action
begins
> > > to be selectively applied to traffic (in this case, the action is
> > > 'drop'). The 3rd number is the point beyond which the exceed-action
> will
> > > be applied to ALL traffic. If you truly wanted to limit traffic to
not
> > > exceed 3.5Mb, then you would want to make sure that rate+Eb = 3.5Mb
> > >
> > > ex: rate-limit input access-group 101 3000000 450000 500000
> conform-action
> > > transmit exceed-action drop
> > >
> > > That would allow up to 3.45Mb of traffic before any action was taken
and
> > > would drop *some* traffic between 3.45Mb and 3.5Mb, but would drop all
> > > traffic over 3.5Mb.
> > >
> > > Hope that helps,
> > >
> > > ------------------------------------------------------------
> > > C i s c o S y s t e m s Michael E. Flannagan
> > > | | Network Consulting Engineer
> > > ||| ||| Research Triangle Park, NC
> > > ||||||| ||||||| (919) 392-4550
> > > .:|||||||||||:.:|||||||||||:. mflannag@cisco.com
> > > ------------------------------------------------------------
> > >
> > > On Fri, 2 Feb 2001, Robert DeVito wrote:
> > >
> > > > If I wanted to limit SMTP to 3.5 MB on my ethernet port I would do
the
> > > > following?
> > > >
> > > > rate-limit input access-group 101 3500000 8000 8000 conform-action
> transmit
> > > > exceed-limit drop
> > > > !
> > > > access-list 101 permit tcp any any eq smtp
> > > >
> > > > My question is, when configuring CAR, it requires me to add the bps
> > > > burst-normal and burst-max. If I came across an scenario when it ask
> me to
> > > > limit bandwidth to a specific protocol, in this case smtp, to
3.5mbs,
> if I
> > > > configure it to burst 8k, I am really not limiting it to 3.5mbs. Am
I
> > > > thinking correctly? Is there a different way of doing this?
> > > >
> > > > Thank you,
> > > > RobertRobert DeVito
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