Topic: Any Openreach engineers here able to answer about packet overhead/mpu for CAKE? (Read 20442 times)

heavyrain · « **on:** July 07, 2025, 10:11:33 AM »

Hello there

As you may know, SQM is becoming more popular and I've looked into setting it up with CAKE. On VDSL2, it's been relatively easy to find exact values (34 packet overhead and 68 minimum packet) but when it comes to the FTTP implementation by Openreach, I can't find any concrete info on this. It just seems like a black box. The general consensus has been to just overestimate values (44 overhead and 84 mpu) but I would like to try and optimise it with proper values if only to learn something.

Thank you

perlen · « **Reply #1 on:** July 07, 2025, 12:16:22 PM »

Openreach FTTP supports baby jumbo frames for pppoe connections (MTU 1508).
So the default setting in CAKE of RAW should be fine, as the standard 1500 MTU is usable.

https://www.man7.org/linux/man-pages/man8/tc-cake.8.html

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Author Topic: Any Openreach engineers here able to answer about packet overhead/mpu for CAKE? (Read 20442 times)

heavyrain

Any Openreach engineers here able to answer about packet overhead/mpu for CAKE?

perlen

Re: Any Openreach engineers here able to answer about packet overhead/mpu for CAKE?