From: Bob Sinclair (bsinclair@netmasterclass.net)
Date: Wed Oct 20 2004 - 18:58:39 GMT-3
Gladston,
The major difference between the single-rate and two-rate policer is in how
tokens get into a second bucket. In the single-rate policer, tokens are
placed into the second (Be) bucket only when you are below the the average
rate. It acts like a savings account to let you burst above cir. With the
two-rate policer the buckets are filled independently, you do not have to
go below cir in order to put tokens in the second bucket.
By analogy, the single rate policer is like getting a $10/week allowance.
The only way you can spend $15 in a week is to save $5 from a previous week.
The two rate policer is like getting two allowances per week - $10 from your
parents and $5 from your grand parents. You can spend $15/week without
having to first save.
If you want a three-color marker (conform, exceed, violate), you can use
either method. The RFCs (2697 and 2698) say that the single-rate is most
useful when the it is the LENGTH of a burst, not its peak rate that
determines service elilbility. The two-rate is most useful when peak rate
needs to be enforced separately from a committed rate. The two-rate method
allows for a sustained excess rate, and seems easier to configure, to me,
but it really depends on the traffic profile you want to enforce.
HTH,
Bob Sinclair
CCIE #10427, CISSP, MCSE
www.netmasterclass.net
----- Original Message -----
From: <gladston@br.ibm.com>
To: <ccielab@groupstudy.com>
Sent: Wednesday, October 20, 2004 4:44 PM
Subject: Two Rate Policer
> Kind of confuse with this statement:
>
> =================
> quoted
> this feature was available, you could police traffic with the single-rate
> Traffic Policing feature.
> http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t4/ft2rtplc.htm
> ================
>
> Because this another Cisco URL seems to says it differently:
> ================
> quoted
> There are currently two types of token bucket algorithms: a single token
> bucket algorithm and a two token bucket algorithm. A single token bucket
> system is used when the violate-action option is not specified, and a two
> token bucket system is used when the violate-action option is specified.
> http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t2/ftpoli.htm
> =================
>
>
> Am I taking an erroneous assumption that "single-rate" and single token"
> are the same terms?
>
> Behind that question is that it is not clear to me what task would require
> using one or another.
> police cir pir
> or
> police (bps) (burst-normal)...
>
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