[Codel] About Packet Drop in Codel

[Rick Jones]

On 03/02/2015 09:43 AM, divya singla wrote:
> please explain me this also:
>
> how codel controls the delay like it drops the packet when it spends
> more time than target and after that it will be retransmitted.
> So in case of retransmission and all, i think delay should be more.
> isn't it?

At the risk of typing beyond my understanding...

CoDel is expected to be deployed in situations where the maximum 
possible queuing is rather large at a bottleneck link.  Probably several 
multiples of the RTT in time/size.  It is a response to a belief that 
throwing more and more memory at queues and holding that every packet is 
sacred is a good thing.  Consider what would/could happen with such 
queues without CoDel and what that would mean to delay.

> Next , How  does UDP react like tcp adjusts its rate when there is
> packet loss and UDP?

UDP doesn't.  The *application* using UDP is expected too, just as 
applications using UDP have been expected to do "the right things" from 
the beginning.

rick jones

>
> On Fri, Feb 27, 2015 at 4:44 AM, Stephen Hemminger
> <stephen at networkplumber.org <mailto:stephen at networkplumber.org>> wrote:
>
>     On Thu, 26 Feb 2015 19:32:58 +0100
>     "Richard Scheffenegger" <rscheff at gmx.at <mailto:rscheff at gmx.at>> wrote:
>
>     > Hi Members,
>     > i am doing M.tech and my research topic is AQM.
>     > i tried to run codel with ns-2.35.
>     > And i found packet loss is more in codel as compared to RED.
>
>     More packet loss is no necessarily a bad thing.
>     You need to measure throughput and latency together.
>
>
>
>
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