why upload with adsl is faster than 100M ethernet ?

Fri Oct 15 14:04:05 UTC 2004

Alex Bligh wrote:

>
>
>
> --On 15 October 2004 13:33 +0200 Iljitsch van Beijnum 
> <iljitsch at muada.com> wrote:
>
>> However, the cause can also be rate limiting. Rate limiting is deadly 
>> for
>> TCP performance so it shouldn't be used on TCP traffic.
>
>
> Add "unless appropriate shaping is performed prior to the rate-limiting
> with the parameters carefully tuned to the rate-limiting"
>
> You can also see an effect similar to rate-limiting from inadequate
> buffering where there is a higher input media speed than output.
>
The following link provided a great overview of tcp throughput
 http://rdweb.cns.vt.edu/public/notes/win2k-tcpip.htm

> I can't remember what the tool is now, but there used to be a tool which
> worked like ping but sent a udp stream at a given rate per second and 
> told
> you about packet drops, and also allowed for some parameter to be tweaked
> to give stochastic variation in interpacket delay (i.e. massive jitter).
> You could use this to show inadequate buffering on gigabit interfaces 
> where
> a 2Mb/s stream would get through, but if you wound up the jitter
> sufficiently, a whole burst of packets would arrive together and a 
> gigabit
> interface with (deliberately) misconfigured buffers would then drop 
> packets.
>
> Alex

netiq's qcheck (the artist formerly known as ganymede) is a utility we 
commonly use to prove to customers that they are indeed receiving 
correct throughput.

http://www.ixiacom.com/products/performance_applications/pa_display.php?skey=pa_q_check

-Gordon