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New Member

Need Suggestions For Engineering a 0 CIR Wan For Voice

Hello all,

We just brought on a client that has very recently signed a contract with sprint for a 0 cir wan cloud. Basically every frame is marked with the DE bit set to 1 which means every frame can be dropped.

Its a weird circuit in that all of the frame circuits aren't terminated on a layer 2 frame switch, but on a sprint router somewhere. The sessions through the cloud are then re-encapsulated using L2TP and sent across the cloud, which are then reencapsulated as frame on the far end.

The way i am looking at it, there is no way to do any traditional traffic shaping on these frame circuits.

Does anyone have any suggestions for qos on this type of circuit?

Thanks for your help!


Re: Need Suggestions For Engineering a 0 CIR Wan For Voice

Try to get them to buy CIR to cover amount of voice bandwidth on the link.

Other then that, there is no way of knowing when a packet will be dropped. Do you know if the carrier is policing the frame relay portion, or L2TP path and if so what it is shaped to?

Best you can do as-is, is configure FRTS on the router interfaces and policy to prioritize the rtp traffic and shape frame down to a 10ms interval with a bogus? cir value so the router is sending traffic out at 10ms rate. And cross your fingers and hope for the best.. probably would also help to keep any un-needed traffic from going across the WAN also.

Do the current frame relay stats indicate any FECNs/BECNs on the PVCS? This may not be accurate either since it isn't frame end to end though.

New Member

Re: Need Suggestions For Engineering a 0 CIR Wan For Voice

What Sprint has told me is that with a 0 CIR, they are allowed to transmit at full wire speed until the cloud becomes congested, at which time whatever traffic that needs to be dropped will be. Being every frame has the DE bit set, it is indescriminate as to what gets dropped.

I have checked the BECN/FECN count which is 0 all across the board. I imagined this would be so before i checked, with the DE always being 1, the frame switch (or router in this case) has no need to send BECNs back.

This circuit is actually called SprintLink, have you ever heard of it or anything similar to it? I haven't ever come across it before, and the way they transport everything L2TP across their cloud is kinda interesting.

Also, doesn't FRTS just set the DE bit according to a policy or am i way off?

Thanks again!

Re: Need Suggestions For Engineering a 0 CIR Wan For Voice

The router will set the DE bit on packets if you have a frame-relay DE-list configured to mark packets with this bit. By default the DE bit is not set.

The show frame-relay pvc command will show inbound and outbound packets with DE bit set. "in DE pkts" and "out DE pkts". You could clear the counters and send some traffic and see if the in DE pkts counter matches the number of packets transmitted on the other router.

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