[Cerowrt-devel] Correctly calculating overheads on unknown connections

Andy Furniss adf.lists at gmail.com
Tue Sep 23 11:10:00 EDT 2014

Sebastian Moeller wrote:

> I would just go and account for all overheads I could deduce, so I
> would guess: 8 bytes PPPoE, 4 byte VLAN tags, 14 bytes ethernet
> header (note for tc’s stab method one needs to include the ethernet
> headers in the specified overhead in spite of the man page)

I don't think the man page is wrong - it includes eth in the pppoe example.

There is a difference between shaping on ppp and shaping on eth which
needs to be and is noted.

FWIW I tried a few pings on my VDSL2 and don't think I'll be any use for

I do get an increase with larger packets but it's more than it should be

The trouble is that my ISP does DPI/Ellacoya Qos for my ingress and I
guess this affects things a bit too much for sub milisecond accuracy
needed on a 20/80 line.

At least I don't have to bother so much about ingress shaping (not that
I would @80mbit so much anyway).

Ping and game traffic comes in tos marked 0x0a and gets prio on their
egress which is set slightly lower than my sync profile speed.

Additionally it's probably not the best time to test as they had a
recent outage which caused in-balance on their gateways which seems to
still persist.

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