From: Dennis J. Hartmann (dennisjhartmann@hotmail.com)
Date: Mon Apr 04 2005 - 21:36:36 GMT-3
PIR and Bc. Let's say that I'm a service provider offering Gigabit
Ethernet handoffs and I want to enforce a CIR of 2Mbps, but allow the
customer to transmit at up to 50Mbps. You can't do this with a Bc because
the Bc can not be configured large enough. The PIR can be set to full port
speed if you wanted to. I hope this helps.
-Dennis Hartmann
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Eric
Taylor
Sent: Monday, March 14, 2005 4:46 PM
To: ccie2be; Jongsoo.Kim@Intelsat.com; ccielab@groupstudy.com
Subject: RE: police (two rates) under policy map
Tim, here is a decent link.
http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1839/products_feat
ure_guide09186a0080087c4f.html
Bandwidth Management Through Rate Limiting This feature provides improved
bandwidth management through rate limiting.
Before this feature was available, you could police traffic with the
single-rate Traffic Policing feature. The Traffic Policing feature provided
a certain amount of bandwidth management by allowing you to set the peak
burst size (be). The Two-Rate Policer supports a higher level of bandwidth
management and supports a sustained excess rate. With the Two-Rate Policer,
you can enforce traffic policing according to two separate rates-CIR and
PIR-specified in bits per second (bps).
Now, out of all that mumbo jumbo above.
I think the sentence that really answers your question is "The Two-Rate
Policer supports a higher level of bandwidth management and supports a
sustained excess rate." Keyword: sustained
Follow this link to read up on the token buckets, etc...:
http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1835/products_conf
iguration_guide_chapter09186a00800bd8ed.html#wp1012025
Here you will see that specifying the excess burst size is a bit different
from using the two-rate policer and specifying cir/pir.
HTH,
Eric
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: Monday, March 14, 2005 3:12 PM
To: 'Eric Taylor'; Jongsoo.Kim@Intelsat.com; ccielab@groupstudy.com
Subject: RE: police (two rates) under policy map
Hey Eric,
Maybe you can explain something about your example config:
What's the benefit of using pir instead of be?
To me, it seems like there's really no difference pir and be.
They both allow for a packet rate over the cir.
If I remember correctly, the only difference (and it may not apply in this
particular example) is that pir is expressed in bps and be is in Bps.
I've read the 2 rate new feature documents several times but never found a
satisfactory explanation.
TIA, Tim
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Eric
Taylor
Sent: Monday, March 14, 2005 1:47 PM
To: ccie2be; Jongsoo.Kim@Intelsat.com; ccielab@groupstudy.com
Subject: RE: police (two rates) under policy map
Guys,
This should clear things up for you on the usage of CIR and PIR.
http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1829/products_feat
ure_guide09186a00801b2410.html#1026768
Router(config)# policy-map police
Router(config-pmap)# class class-default Router(config-pmap-c)# police cir
1000000 pir 2000000 Router(config-pmap-c-police)# conform-action transmit
Router(config-pmap-c-police)# exceed-action set-prec-transmit 4
Router(config-pmap-c-police)# exceed-action set-frde
Router(config-pmap-c-police)# violate-action set-prec-transmit 2
Router(config-pmap-c-police)# violate-action set-frde-transmit
Router(config-pmap-c-police)# end
The following actions will be performed on packets associated with the
policy map called police:
All packets marked as conforming to these rates (that is, packets conforming
to the CIR) will be transmitted unaltered.
All packets marked as exceeding these rates (that is, packets exceeding the
CIR but not exceeding the PIR) will be assigned an IP Precedence level of 4,
the DE bit will be set to 1, and then transmitted.
All packets marked as violating the rate (that is, exceeding the PIR) will
be assigned an IP Precedence level of 2, the DE bit will be set to 1, and
then transmitted.
In a RL scenario, we mark the clp bit on ATM cells that exceeds the CIR but
not the PIR. We drop everything that exceeds the PIR.
HTH,
Eric
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
ccie2be
Sent: Monday, March 14, 2005 7:56 AM
To: Jongsoo.Kim@Intelsat.com; ccielab@groupstudy.com
Subject: RE: police (two rates) under policy map
Hi Jongsoo,
You're raising an issue I've been talking about even since my last lab
attempt where I got my butt kicked especially on QoS.
If you search the GS archives during the period starting in the 2nd half of
last November and going through December, you'll find a number of discussion
threads between me and Bob Sinclair, Scott Morris, and perhaps Marvin
Greenlee on this topic.
As you just discovered, the police command has lots of parameters and can be
extremely confusing.
However, one of things you want to try to avoid is reading too much into the
task.
Take your first example, why wouldn't you just configure:
police 1000000
and let IOS fill-in the rest.
IOW, do you really need to compute "normal burst"? If you let IOS compute
"normal burst", what would be the problem?
Besides, how would you compute "normal burst"? Doesn't that vary depending
on the rate being policed?
I don't remember all the details, but I recall that Tc is determined in a
very different way when policing versus traffic shaping.
In your 2nd example, I don't think you should use pir. That's for the
situation where you have 2 rates: cir and pir - which has never made much
sense to me since cir already has a mechanism for bursting above the cir
rate. It's called be.
Personally, I suspect this pir thing is a result of the wide-spread illicit
drug problem having affected some people at Cisco. :-)
HTH, Tim
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jongsoo.Kim@Intelsat.com
Sent: Sunday, March 13, 2005 2:23 PM
To: ccielab@groupstudy.com
Subject: police (two rates) under policy map
I don't think many of you know about this new command 12.2T.
At least, I found out this today. It may answer one of my QoS questions I
couldn't answer a few weeks.
Pay attention on units "bits" vs "bps"
If question said " police 1Mbps with normal burst = 64Kbits.
police 1000000 8000 conform-action transmit exceed-action drop
But if question ask " police 1 Mbps with burst rate of 64Kbps", how can you
configure?
Maybe it should say peak-rate instead of burst rate?
At least, I am thinking
police cir 1000000 pir 1064000 conform-action transmit exceed-action
transmit violate-action drop
Any feedback is welcomed.
Regards
Jongsoo
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