Re: [LARTC] tail and head drop qdiscs

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

vincent perrier wrote:
> I think that there are no qdiscs that permit to drop the oldest
> frame of a queue when this queue is full, but I would like to
> be wrong: 
> 
> bfifo drops arriving frames when the max queue length is reached. 
> 
> red also drops arriving frames in a more elaborate fashion, with
> a drop probability that increases above a limit and becomes 
> a drop certitude when the max queue length is reached.
> 
> sfq drops "fairly", it piles frames with same (ip source, ip dest, 
> port source and port dest) and drops a frame from the
> biggest pile to favour the smaller flows. 
> 
> But I cannot find the qdisc that reacts like a bfifo or red qdisc
> but drops the oldest message of the queue when a drop is needed.
> 
> Even better: a qdisc with an autodestruct algorithm for each
> frame in the queue that would garantee the "freshness" of 
> each frame coming out. 
> 
> If you know of such qdiscs, please share.
>  

What sort of thing do you want this for?

I made a version of esfq head drop for use in specific circumstances.

The only other thing I thought head drop generally could be usefull for 
is a game server, but then maybe a policer would be better than a queue 
WRT latency.

Andy.

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