[Bloat] Bloat on Layer 2 Was: ECN & AQM Hall of Fame?

[Florian Lohoff]

On Sun, Jan 30, 2011 at 11:40:05PM +0100, Richard Scheffenegger wrote:
> Hi,
> 
> wasn't there talk about getting a Hall of Fame for networks / operators,
> which are using and actively supporting AQM and ECN in their administrative
> domain?
> 

The problem is not only in the IP Path.

In the old days i was used to be able to work interactive on a Serial
connection with 33600 Bit/s shared with 10 Dialup users.

After reading Jims blog i started to dig in our Network and found
huge buffers on the Huawei MA5600 DSLAMs which are Ethernet based
DSLAMs. These DSLAMs are basically invisible to the user as they
are only in the L2 PPPoE path for the customer.

I found the Buffer to be roughly 1MByte per Line. With a 1MBit/s DSL 
line this is roughly 10s worth of Buffer which i can observe on my line
in the real world.

There is no way of tuning this buffer based on the speed or even shrink
it so its difficult to fix.

ANCP + a shaper on the BRAS would be a solution which is basically how i solved
it for me - As i have a fixed rate 1MBit/s DSL i attached a 1MBit/s rate
limiter to my profile on the BRAS which immediatly fixed the problem for me.

And the Hall of Shame probably is a good idea - but wont fix it. The
ISPs are not aware of the problem as testing happens on empty lines with
30cm of wire. I sent the link to Jims blog to certain people and the DSLAM
guys immediatly promised to contact Huawei about the non tunable buffersize.

Flo
-- 
Florian Lohoff                                                 f at zz.de
                 Professionell gesehen bin ich zu haben ....
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