Generating FECN's & BECN's When Using IOS for Frame-Relay Switching

[scott.dunn]

Anyone know how to get the IOS (I'm using 2801 with 12.4) to generate FECN's and BECN's when it's being used as a frame switch? It apparently doesn't do it by default.

[pkhatri · Accepted solution]

Hi,

You can use FR congestion management features to do this.

The following link has more info on this:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_guide09186a0080080049.html#1015359

Pls rate the post if it helps.

Paresh

[scott.dunn]

Paresh,

Thank you for the link. I've got the FECN's to work. So far no luck with the BECN's. I'm holding off rating this until I get the BECN's working.

Thanks again.

Scott

[pkhatri]

Hi Scott,

Note that you will only get BECNs if you are sending traffic in both directions.

There is a useful feature that you can use if the end-points are Cisco routers too. Configure 'frame-relay fecn-adapt' in your map-class which will get the router to send test frames with BECN set when it receives FECNs. This way, even if there is no traffic in the other direction, the source router will still get it from the destination router.

Hope that helps,

Paresh.

[scott.dunn]

Hi Paresh,

The configuration is working now. There were two reasons my config wasn't good. First, I was configuring both of the techniques at the same time. Now I know they are mutually exclusive. Second, on one endpoint router I configured traffic shaping, which was restricting traffic to the frame switch, so the frame switch wasn't getting its buffers filled.

I used the fecn-adapt on one endpoint and didn't get the result I expected. when I finally got the config fixed the frame switch started sending FECN's and BECN's. Then, with fecn-adapt on one endpoint I expected to see the sum of BECN's and FECN's reported by the frame switch showing up on the other endpoint. (Thinking it would receive BECN's from the switch, and also the BECN"s reflected by the remote endpoint). It didn't happen that way. The BECN count on the remote end point was the same as what was reported on the frame switch.

Anyway, it's working now.

Thank you very much for the link.

Scott