Bandwidth Limiting

[cammaher]

Hi All,

We currently have a 2Mbit ATM connection between two of our sites. A couple of times per week, it seems that the whole bandwidth becomes consumed by individual connections, wether it is a Server updating its database or a user doing a big file download. This clogs up the link and makes it nearly unuseable by other users.

What would be the best way to combat this. Would it be to set-up rate limiting so each connection can only use x% of bandwidth or is there a better solution.

The devices at each end are Cisco 7200 routers.

Thanks in advance,

Cameron

[pkhatri]

Hi Cameron,

I suggest you setup CBWFQ on the link so that different applications are guaranteed certain percentages of your PVC bandwidth. The point of using a queueing discipline like CBWFQ is to ensure a fair distribution of traffic between different classes of traffic (as defined by you) in the event of congestion.

An example follows:

class-map match-all realtime

match ip precedence 6

class-map match-all interactive

match protocol citrix

class-map match-all bulk

match access-group 10

!

policy-map OutPolicy

class realtime

bandwidth 128

class interactive

bandwidth 256

class bulk

bandwidth

class class-default

fair-queue

interface ATM2/0.32 point-to-point

bandwidth 4000

ip address x.x.x.x x.x.x.x

pvc 1/32

vbr-nrt 4000 4000 1

tx-ring-limit 3

encapsulation aal5snap

max-reserved-bandwidth 75

service-policy output OutPolicy

Ok, there are a couple of things to note here:

- the class-maps are a classification mechanism. You can match on a wide variety of things such as ACLs, IP precedence, input interface etc... If you can specify a bit more details on the traffic you want prioritised, we can help you with formulating those

- the bandwidth statement within the policy-map provides a minimum bandwidth reservation to all your classes. If the interface is not congested, these classes can use up to the full interface bandwidth.

You should see a dramatic improvement once you apply this on both sides of the link.

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

Regards,

Paresh.