Re: [LARTC] Unshapeable traffic

[Andy Furniss <andy.furniss@dsl.pipex.com>]

Tomasz Wrona wrote:
> AF> Do you know roughly how many active connections you have?
> 
> Up to 30K.

I think this could be the problem - If 30k connections all tried to send 
through 4mbit then a quick prod at xcalc tells me that each would get to 
send 1 1500 byte packet every 90 seconds.

> 
> However I just found propably reason of issue...
> 
> As p2p is both direction transfer most of it sends large ACK packets.
> After short investigation there are some facts:
> 
> 1)  40% of p2p ACK packets have payload larger than 1KB, other are regular
> ACKs
> 
> 2) 15% of all other traffic ACKs are longer than 1KB, 85% are regular
> ACKs.

Maybe - depends how you are testing, remember that all tcp packets have 
ack set after the initial handshake.

I know p2p like bittorrent does use a single connection in full duplex , 
but I never noticed it hurting upstream shaping - it does make 
downstream more bursty as the empty acks can get sent ahead of the 
piggybacked ones stuck in the queue and ack a large chunk of data.


> 
> I have priority class only for regular short ACKs, so other goes to
> custom p2p class.
> Cause ACKs have to be send after receiving some data propably that's why I can't
> slow down traffic to defined value. Every time customer receive p2p data,
> sends LARGE ACK. Outcome is that shaping p2p upload have impact on
> p2p download and vice versa or in other words, to shape upload, shape
> download also.
> Giving extra prio for large ACKs would be suicide. I suppose the only
> way to shape p2p is to dominate it by hard limits [up/down].
> 
> Please correct me if it's fake [and give an advise ;)].
>

Maybe limiting the number of connections per user would be best - if you 
can.

Andy.


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