Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Webcast-Catalyst9k
New Member

FR traffic shaping parameter

Hello

when configure a FR traffic shapping parameters,

frame relay cir

frame relay mincir

frame relay bc

.

.

"During congestion, provider will mark any traffic in excess of ( ) as dsicard eligible"

what is in the blank, cir or mincir?

thanks

11 REPLIES
Purple

Re: FR traffic shaping parameter

Hi,

According to the cisco recommendations, the minCIR should be set to whatever the provider has offered as the CIR for the circuit.

Therefore, the answer to your question is the mincir. Anything in excess of this will exceed the CIR set the CIR and will be marked DE.

Hope that helps - pls rate posts that help.

Regards,

Paresh

Silver

Re: FR traffic shaping parameter

As Paresh indicated, it really is up to you how you configure these parameters. If you know what your CIR is from the Frame Relay provider it is your choice whether you configure this to match 'mincir' or 'cir'.

If your PVC will be carrying voice it is strongly suggested that you configure the actual CIR to 'cir'. This will assure that no voice packets will be dropped by the provider. If the circuit is only carrying reliable transport data traffic, then configuring the actual CIR to 'mincir' will squeeze better performance out of the PVC.

If you choose the later option you may also want to configure 'frame relay adaptive-shaping becn'. This will tell the router to throttle back to 'mincir' if BECNs are received from the provider.

HTH. Please rate this post.

Thanks,

Brad

Re: FR traffic shaping parameter

Hello,

I think it should be CIR. The reason is, that the SP will do whatever is stated in the contract. And there usually CIR will be defined. mincir is a Cisco specific FR traffic shaping parameter on routers. Not even in Cisco WAN switches a mincir will be defined - there is a parameter called MIR used internally for overbooking purposes, but policing will be executed with CIR.

So with Cisco WAN switches (and other vendors as well) FR frames above CIR will be marked with DE.

Hope this helps! Please rate all posts.

Regards, Martin

Purple

Re: FR traffic shaping parameter

I'm afraid I must disagree (as to the answer) with Martin.

It is true that MinCir is solely a Cisco IOS feature...However, the MinCIR is intended to be the lowest rate at which a PVC will be shaped in the face of signals received via BECNs etc (when adaptive shaping is configured). Now, why would you configure minCIR (the lowest shaping rate) to ever be lower than the contract CIR. Usually, you would configure minCIR to be the contracted CIR from the provider and the CIR will be configured to be 95% of the lower of the two frame-relay access rates at each end. This is because most FR providers will enable you to transmit at the access rate on a sustained basis, with the proviso that all traffic in excess of CIR will be marked DE.

Therefore, the IOS parameter minCIR corresponds to the actual PVC CIR and exceeding it will result in frames marked DE at the FR switch.

This view is backup by Cisco. Here's a definition of MinCIR from CCO:

frame relay mincir

" The actual guaranteed rate obtained from service provider in bps. This value should be the minimum rate you should drop to in the event of congestion (dropping below this rate implies you are not getting the bandwidth you are paying for). In certain cases (listed above) the mincir and cir values must be the same. The value of mincir is half of the CIR value in bps by default."

This quote is from:

http://www.cisco.com/en/US/tech/tk713/tk237/technologies_configuration_example09186a00800942f8.shtml

Therefore, the answer is the MinCIR.

Hope that helps - pls rate posts that help.

Regards,

Paresh

Re: FR traffic shaping parameter

Hello,

the original question is about the SP:

"During congestion, provider will mark any traffic in excess of ( ) as dsicard eligible"

An SP will (typically) not use routers, but carrier class FR switches. And those switches will mark traffic above CIR with DE bit. DE bit marking is a function of the policer in a FR switch, and all policers in Cisco WAN switches including IGX and MGX will utilize CIR, Bc and Be. At least this was the case when I did my WAN sitching CCIE. ;-)

So the answer is CIR.

There are different ways of taking this fact into account by configuring the router for FR traffic shaping. Paresh you gave some good explanations about it. But I was relating to the sentence above in the original post.

Router config in my opinion was not the question, though it might be helpful to understand the relation and possibilities for the original poster.

Hope this helps! Please rate all posts.

Regards, Martin

Purple

Re: FR traffic shaping parameter

Hey Martin,

I'm afraid I must still disagree as to the answer :-)

Sure, the question was about the provider marking the traffic. There is no doubt about that.

But the question talks about shaping, which is not really a provider function. And the fact that it mentions MinCIR means that it is referring to the configuration of FR traffic-shaping on a router.

I have no problems with your explanation about marking on the carrier FR switches (in fact, we have a large deployed based on MGX/IGX switches so I am familiar with their operation). For the switches, the policer will indeed mark traffic in excess of CIR with DE. What I am saying is that the MinCIR parameter when configuring FRTS on a router is directly related to the CIR parameter as configured by a provider...

Paresh

Re: FR traffic shaping parameter

Hello,

Paresh, my point was, that we are talking about two different things. And that this is caused by a somewhat difficult to understand original post (being a non native speaker everything in english is difficult to understand ;-).

By the letter, answering the question about the blank between brackets I am right - CIR should be there - no matter what the intention of the original post is. :-)

Interpreting the original post as a request for FR traffic shaping configuration of a router your statements are for sure true.

Regards, Martin

Purple

Re: FR traffic shaping parameter

Yep. Agreed :-)

I guess we have both been saying the same thing all along, haven't we ?

So the answer is:

CIR - if the question is asking about the parameter used by the provider

MinCR - if the question is asking about the frame-relay traffic shaping parameter configured on the router.

How's that ?

I bet we've got the original poster really confused now :-)

Paresh.

VIP Purple

Re: FR traffic shaping parameter

Hello,

I do not want to add to any possible confusion, but I used to work at (former) Worldcom on FR switches, and we usually would mark everything above CIR as DE. I think the mincir would usually be used in the context of frame relay adaptive shaping only...

If this is an exam question, I would opt for CIR.

Regards,

GP

New Member

Re: FR traffic shaping parameter

Hi guys,

sorry for lost attention for a while, i think i should claify my posting early.

it is one of my last CCIE lab test in QoS section.

question was configuring router with aproppriate FR shapping parameters with instruction as below.

"During congestion, provider will mark any traffic in excess of 48Kbps as dsicard eligible"

"Maximum throughput is 128Kbps"

and some more about Tc....

1, cir 128k, min cir 48k

or 2, cir 48k, mincir 24k

at that moment of time, i answered with 1, but i think i couldn't get a credit for this, but i am not sure.

thanks

Purple

Re: FR traffic shaping parameter

"During congestion, provider will mark any traffic in excess of 48Kbps as dsicard eligible"

"Maximum throughput is 128Kbps"

Based on that, the CIR used by the provider is clearly 48kbps.

Therefore, your traffic-shaping parameters should be as follows:

- CIR = 128k

- MinCIR = 48k

That will mean that the router will shape to a minimum of 48kbps - since that is the CIR set by the provider, you are always guaranteed that much, so you should not be shaping to any less than that. Using a shaping CIR will mean that the router will shape to 128kbps unless it starts getting congestion indications from the network (only if adaptive-shaping to BECNs is configured). If it does start getting BECNs, it will then drop the sahping rate, but only to as low as 48kbps.

Hope that helps - pls rate the post if it does.

Paresh

161
Views
20
Helpful
11
Replies
CreatePlease to create content