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CIR with Packet drops

I am working for a client who needs a clarification regarding Frame relay

My client has set a CIR in his network has 64 K and it is burstable till 2 Mbps.

but we are seeing the frames getting dropped eventhough the CIR has not been exceeded.

It would be of great help if somebody can throw more light into the problem,and let me know the possibilities why the frames are getting dropped eventhough the CIR has not been exceeded.

Thanx in advance..

Cisco Employee

Re: CIR with Packet drops


This could have several reasons.

1) the FR service provider typically overbooks even CIR, which might cause the issue.

2) CIR is measured on a small time scale like 125 ms. Are you sure you are not above CIR at some point in time? A simple "show interface" does not help, as there you average over 30 seconds or more. Do you implement FR traffic shaping? If not, this might resolve the issue.

Regards, Martin

Super Bronze

Re: CIR with Packet drops

If you truly are not exceeding your CIR, but take note of the prior poster's comments, complain to the vendor providing your frame-relay. Normally, your frames shouldn't be dropped when you conform to your CIR.

If you client wants to utilize the burstable bandwidth, CIR will often be exceeded and frames might be dropped. Such drops might be minimized if you also configure traffic shaping that responds to FECNs/BECNs.