perfsonar development work

[Sven Ubik <>]

Hi,

> > the question that is typically asked is
> > 1) why do we need OWD?
>
> .... instead of ping? The answer to this question would probably be: If you
> have an asymmetric path where one direction is significantly slower (or
> faster ;) ) than the other direction, you cannot see this with ping, because
> ping measures only the round trip time.
> You need to measure both directions seperately to find out such behaviour.

I think this describes what OWD measurement does, but not why we NEED it. 
In my opinion importance of OWD is sometimes overstated, RTT is usually 
enough to assess effect of delay on throughput. It is rather hard to find 
an application that would really benefit from OWD instead of RTT. I think 
that one use of OWD (or detection of assymetry in delay) could be in 
assessing whether router queues fill up, which a sort of TCP 
implementations starting from Vegas unsuccessfully tried to do using RTT.

Regards,

Sven