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vj
New Member

Configuring Asymmetric bandwidth on Cisco Routers

Hello,

I need to configure Asymmetric bandwidth on a frame-relay based network. Network is satellite-based.

Need for asymmetric configuration: The Remote to Hub is 30% of the other way traffic.

I have few queries on QoS config, we implemented.

Is QoS treated as end-to-end and bi-directional?.

Hub Configuration

map-class frame-relay 448k8966k

frame-relay adaptive-shaping becn

frame-relay cir 576000

frame-relay bc 28000

frame-relay mincir 448000

frame-relay holdq 256

service-policy output Policy1

Remote Configuration

map-class frame-relay 128k256k

frame-relay adaptive-shaping becn

frame-relay cir 256000

frame-relay bc 32000

frame-relay mincir 128000

frame-relay holdq 256

service-policy output Policy1

Does this above config work?. What are the ways to test if above config works fine.

Rgds,

VJ

5 REPLIES

Re: Configuring Asymmetric bandwidth on Cisco Routers

Hello,

QoS in the DiffServ frame-work (which is applied here) is dealing with PHB - per hop behaviour. Generally speaking you tell each router which ressources it has locally and which amount of them should be given to which traffic class. So QoS in your scenario is NOT end-to-end.

This is the reason why your config can work even with asymmetric bandwidth. Assuming you are mainly concerned about queueing (CBWFQ, LLQ) the return traffic received over an interface is not even considered - that is why you have only an output policy.

As a sidenote: in case you have VoIP traffic it is recommended to set mincir equal to CIR and not to burst. You do not want the SP to mark FR frames containing voice eventually with DE bit or even drop them.

For normal TCP/IP traffic your config will just be fine, assuming proper classification and queueing and also CIR, MinCIR and Bc settings.

Hope this helps! Please rate all posts.

Regards, Martin

vj
New Member

Re: Configuring Asymmetric bandwidth on Cisco Routers

Hi,

Many thanks for the reply.

As of now, we have only data traffic. But, VOIP may get rolled out in Q3.

Though skeptical, we implemented the above configs in one of the pvc's and didn't find any packet drops. Should I assume here that it worked OK. There is a need to configure other pvc's in asymmetric nature.

Used Bc = 1/8 of CIR.

There was also a suggestion to change the MinCIR as below, any comments?.

map-class frame-relay 448k576k

frame-relay adaptive-shaping becn

frame-relay cir 576000

frame-relay bc 28000

frame-relay mincir 448000

frame-relay holdq 256

service-policy output Policy1

map-class frame-relay 128k576k-LHR

frame-relay adaptive-shaping becn

frame-relay cir 576000

frame-relay bc 32000

frame-relay mincir 128000

frame-relay holdq 256

service-policy output Policy1

Regards, VJ

Purple

Re: Configuring Asymmetric bandwidth on Cisco Routers

Hi VJ,

What is the actual CIR that you have purchased from your provider for these 2 PVCs ?

The MinCIR will be used as the maximum amount of reservable bandwidth on the FR PVC. It will not be used for anything else in your setup since you are not using any form of adaptive-shaping...

Are you running any voice traffic over these PVCs ?

Paresh

vj
New Member

Re: Configuring Asymmetric bandwidth on Cisco Routers

Hello Paresh,

The above configurations are of two routers at end points of the same pvc.

Earlier it used to be minCIR=448k CIR=576K. Based on the demand, we would like to reduce one-way traffic by 30%.

The new requirement is

Remote Router: minCIR = 128k CIR = 256 (or 576?)

Hub Router: minCIR = 448K CIR = 576K

VJ

Purple

Re: Configuring Asymmetric bandwidth on Cisco Routers

Hi VJ,

Under most circumstances, both your sites will be transmitting at the configured CIR rate, unless you encounter congestion in the form of BECNs, at which point it may reduce it down to MinCIR. Therefore, if you want to set a hard ceiling on the transmission rate, I would suggest you configure the following:

Remote router: MinCIR = 128k, CIR = 164k

Hub Site Router: MinCir = 448k CIR = 576k

This would make the ratio of both roughly 3.5

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

Paresh

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