[Cake] FreeNet backhaul

[Pete Heist]

I met with the FreeNet Liberec admins earlier this week, and am just starting to get the first IRTT / SmokePing probe data from a few backhaul routers. I’ll see if I can get snapshots of the SmokePing pages public somewhere, but for now...

https://www.heistp.net/downloads/jerab_ping.pdf <https://www.heistp.net/downloads/jerab_ping.pdf>

https://www.heistp.net/downloads/jerab_irtt.pdf <https://www.heistp.net/downloads/jerab_irtt.pdf>

On this router, there are various “events” that occur with RTT spikes, and in general, UDP RTT maximums appear quite a bit higher than those for ICMP. I speculate that at least some of these events may be bloat, but can’t be sure yet.

This router is an old ALIX with kernel 2.6.26, but on the other hand it does have hfsc + esfq (a variant of sfq with host fairness) deployed, so if it’s actually controlling the queue, one might suspect that sfq it could control inter-flow latency at least somewhat.

I feel the need for better data than this, but this is at least a first look for me at bloat in an ISP’s backhaul. The “elaborate” plan is to gather data for a while, deploy sqm in a couple places (I hope for cake, but the kernel will need to be upgraded on this one), and see what happens… :)

Pete

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