From: gladston@br.ibm.com
Date: Mon Jul 04 2005 - 09:27:51 GMT-3
Thanks Kumara,
That link is very good. I studied it for the first attempt and forgotten
about it.
As it seems there is always a problem on Theory-Implementation on the
most complicated topics, this has its own. Even though this doc explains
that without violate action just one tocken is used, when we type Be
without violate, IOS take the command:
Rack2R1(config)#police 64000 1000 2000
Rack2R1#sh policy-map testex
Policy Map testex
Class testex
police cir 64000 bc 1000 be 2000
conform-action transmit
exceed-action drop
I understand that the theory is correct and the result of the command in
this case is just what the IOS developer choose to show, with no effects.
What do you think?
====================
And because there's no term of violation-action here, we can assume that,
packets over Exceed Burst bucket will be droped
===================
Andy,
As you probably know, CAR uses a more complicated algorithm than CB
Policing, trying to simulate WRED, discarding some packets before all
tokens on Be buckets be used.
Cordially,
------------------------------------------------------------------
Gladston
<kumara.shunmugam@wipro.com>
02/07/2005 10:44
To
<simon.hart@btinternet.com>, <trung@vnsystem.net>, Alaerte Gladston
Vidali/Brazil/IBM@IBMBR
cc
<ccielab@groupstudy.com>
Subject
RE: CB Policing with Be and Without Violate Action
Team
The below URL is crystal Clear for the below raised concern
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_r/qrfcmd5.htm#wp1064737
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
simon hart
Sent: Saturday, July 02, 2005 1:14 PM
To: Andy; gladston@br.ibm.com
Cc: ccielab@groupstudy.com
Subject: RE: CB Policing with Be and Without Violate Action
Andy,
That just about sums it up nicely
Simon
-----Original Message-----
From: Andy [mailto:trung@vnsystem.net]
Sent: 02 July 2005 05:48
To: gladston@br.ibm.com; SIMON HART
Cc: ccielab@groupstudy.com
Subject: Re: CB Policing with Be and Without Violate Action
Hi Sim and Gladston,
As a conclusion, i just want to clarify things we discuss here, pls
correct me if i'm wrong:
- With CAR, the MaxBurst is actually Be+Bc. We can't configure a Be value
that lower than Bc, this text message will display : ! Illegal extended
burst size Increasing extended burst size to xxxx ! And because there's no
term of violation-action here, we can assume that, packets over Exceed
Burst bucket will be droped
- With CB without violate
Ex: Police cir 64000 bc 8000 be 1000 conform transmit exceed drop and we
do show policy-map interface s0/0 ....
police:
cir 64000 bps, bc 8000 bytes
....
don't see Be anymore, so i think the configuration of Be without
violation-action will take no effect, just like we do not set the Be at
all. The action will always be the exceed action no matter what Be value
you configured or what action you specified in exceed command.
Andy.
----- Original Message -----
From: <gladston@br.ibm.com>
To: "SIMON HART" <simon.hart@btinternet.com>
Cc: <ccielab@groupstudy.com>
Sent: Saturday, July 02, 2005 2:06 AM
Subject: Re: CB Policing with Be and Without Violate Action
> Simon,
>
> Giving it a second though I got confused with the follwowing:
>
> You said that using drop for exceed action is strange because even
> though there is tokens on Be packets will be dropped. First time I
> read I makes a lot of sense. But thinking about it again, any action
> for exceed and Be has no sense (if violate action is not used),
> because anything above Bc will exceed for CB shaping.
>
> If the keyword violate is not used, I expected CB Policing do
> something similar to CAR (even considering they use algorithm and CAR
> uses Da/Dc). That is, if the exceed action is 'drop' (when violate is
> not used) I expected CB policing used tokens on Be. But your post made
> me thing again about it and read again Wendell.
>
> So, comparing with CAR:
>
> CAR
> rate-limit output 64000 8000 9000 conform transmit exceed drop <----
> on T0, when 10 packets (1000bytes) arrive, Bc is used to transmit 8
> packets and Be is used to transmit 1 packet.
>
> CB Police without violate
> Police cir 64000 bc 8000 be 1000 conform transmit exceed drop <---- on
> T0, when 10 packets (1000bytes) arrived, Bc is used to transmit 8
> packets and then....everything above is discarded.
>
> So, there is only sense to use CB Police without the keyword Violate
> if the exceed action is anything but Drop. (as you pointed) But, if
> that is true, there is no sense to use a value for Be even if the
> action is other than Drop, because everything above 8 packets on this
> example (no matter if Be is 1000 or 100000) will follow the exceed
> action.
>
> Would you agree?
>
> Cordially
> ------------------------------------------------------------------
> Gladston
>
>
>
> SIMON HART <simon.hart@btinternet.com>
> 01/07/2005 10:23
>
> To
> SIMON HART <simon.hart@btinternet.com>, Alaerte Gladston
> Vidali/Brazil/IBM@IBMBR, ccielab@groupstudy.com cc
>
> Subject
> Re: CB Policing with Be and Without Violate Action
>
>
>
>
>
>
> Sorry, I have noticed a mistake on example 4, should
> read
>
> At Tc4
> Offered packets 10
> In contract first 8 packets - transmit
> Remaining 2 packets - try and use Be
> Decrement Be by 1 token
> Take exceed action on Be - set the dscp of af13
>
> Violate action - drop - therefore drop the remaining
> packet.
>
> HTH
>
> Simon
>
> --- SIMON HART <simon.hart@btinternet.com> wrote:
>
>> Hi Gladston,
>>
>> CB Policing without violate action is valid. Your
>> configs below, however, do not make a great deal of
>> sense. I shall try and explain.
>>
>> Police cir 64000 bc 8000 be 1000
>>
>> Now this statement dictates that we can transmit
>> conforming bits at a rate of 64000 bits (8000bytes)
>> every second. So our Tc is 1 second. The statement
>> also suggests that during any Tc interval of 1
>> second
>> we can send an additional 8000 bits (1000bytes), if
>> the be bucket has not been used up.
>>
>> Now in order to explore this further we need to make
>> some assumptions. Firstly lets assume that the
>> packets offered are 1000bytes (8000 bits).
>>
>> Therefore for each Tc we can transmit 64000/8000 = 8
>> packets that conform.
>>
>> We need to determine the actions for conforming and non-conforming
>> traffic
>>
>> so in your config:
>>
>> conform-action transmit
>> exceed-action drop
>> violate-action drop
>>
>>
>> Example 1
>>
>> Now look at what happens as packets are offered
>>
>> At Tc0
>>
>> Bc = 8 packets
>> Be = 1 packet
>>
>> At Tc1 (end of first period)
>> Offered packets 9
>> In contract first 8 packets - transmit
>> Remaining 1 packet - try and use Be
>> Decrement Be by 1 token
>> Take action on Be - in this case drop, therefore
>> packet is dropped.
>>
>> At Tc2
>> Offered packets 10
>> In contract first 8 packets - transmit
>> Remaining 2 packets - try and use Be
>> Be = 0
>> therefore take Violate action - which is drop
>> remaining packets
>>
>> At Tc3
>> Offered packets 5
>> In contract first 5 packets - transmit
>> Because Bc has not been fully used (3 tokens spare)
>> We can now add 1 token to Be
>>
>> At Tc4
>> Offered packets 10
>> In contract first 8 packets - transmit
>> Remaining 2 packets - try and use Be
>> Decrement Be by 1 token
>> Take exceed action on Be - in this case drop,
>> therefore packet is dropped.
>> 1 packet now violates - take violate action -
>> therefore drop this packet.
>>
>> Hopefully from the above example you can see that Be
>> is not really being used for any purpose. This is
>> because the Be action is the same as the violate
>> action, and hence any non-conforming packets will be dropped.
>>
>>
>> Example 2
>>
>> Now see what happens when we remove the violate
>> action
>> on the previous example.
>>
>> At Tc0
>>
>> Bc = 8 packets
>> Be = 1 packet
>>
>> At Tc1 (end of first period)
>> Offered packets 9
>> In contract first 8 packets - transmit
>> Remaining 1 packet - try and use Be
>> Decrement Be by 1 token
>> Take action on Be - in this case drop, therefore
>> packet is dropped.
>>
>> At Tc2
>> Offered packets 10
>> In contract first 8 packets - transmit
>> Remaining 2 packets - try and use Be
>> Be = 0
>> No violate action - however therefore take Be action
>> -
>> drop packets
>>
>> At Tc3
>> Offered packets 5
>> In contract first 5 packets - transmit
>> Because Bc has not been fully used (3 tokens spare)
>> We can now add 1 token to Be
>>
>> At Tc4
>> Offered packets 10
>> In contract first 8 packets - transmit
>> Remaining 2 packets - try and use Be
>> Decrement Be by 1 token
>> Take exceed action on Be - in this case drop,
>> therefore packet is dropped.
>> No violate action, therefore take exceed action -
>> which is drop the remaining packet.
>>
>>
>> Example 3
>>
>> This time we have no violate action and the exceed
>> action is set-dscp to af13
>>
>> exceed-action set-dscp-transmit af13
>>
>> At Tc0
>>
>> Bc = 8 packets
>> Be = 1 packet
>>
>> At Tc1 (end of first period)
>> Offered packets 9
>> In contract first 8 packets - transmit
>> Remaining 1 packet - try and use Be
>> Decrement Be by 1 token
>> Take action on Be - transmit with dscp of af13
>>
>> At Tc2
>> Offered packets 10
>> In contract first 8 packets - transmit
>> Remaining 2 packets - try and use Be
>> Be = 0
>> No violate action - however therefore take Be action
>> -
>> transmit with dscp of af13
>>
>> At Tc3
>> Offered packets 5
>> In contract first 5 packets - transmit
>> Because Bc has not been fully used (3 tokens spare)
>> We can now add 1 token to Be
>>
>> At Tc4
>> Offered packets 10
>> In contract first 8 packets - transmit
>> Remaining 2 packets - try and use Be
>> Decrement Be by 1 token
>> Take exceed action on Be - set dscp of af13
>> No violate action, therefore take exceed action -
>> which is transmit with dscp of af13
>>
>> In this example it should be clear that the class is
>> no longer policed as all traffic is transmitted,
>> however the out of contract traffic (everything
>> above
>> cir) will be marked as af13.
>>
>>
>> Example 4
>>
>> One final example to round this off.
>>
>> We shall use an exceed action that sets dscp and a
>> violate action that drops packets
>>
>> exceed-action set-dscp-transmit af13
>> violate-action drop
>>
>> At Tc0
>>
>> Bc = 8 packets
>> Be = 1 packet
>>
>> At Tc1 (end of first period)
>> Offered packets 9
>> In contract first 8 packets - transmit
>> Remaining 1 packet - try and use Be
>> Decrement Be by 1 token
>> Take action on Be - transmit with dscp of af13
>>
>> At Tc2
>> Offered packets 10
>> In contract first 8 packets - transmit
>>
> === message truncated ===
>
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