Re: One-way delay measurement for netperf-wrapper

[Rick Jones <rick.jones2@hp.com>]

On 11/29/2013 01:42 AM, Toke Høiland-Jørgensen wrote:
> Well, what the LINCS people have done (the link in my previous mail) is
> basically this: Sniff TCP packets that have timestamps on them (i.e.
> with the TCP timestamp option enabled), and compute the delta between
> the timestamps as a latency measure. Now this only gives an absolute
> latency measure if the clocks are synchronised; however, if we're
> interested in measuring queueing latency, i.e. induced *extra* latency,
> this can be calculated as (latency - min-latency) where min-latency is
> the minimum observed latency throughout the lifetime of the connection
> (this is the same mechanism LEDBAT uses, btw).

Those TCP timestamps are generated (iirc) when TCP transmits the data, 
not when the application presents the data to TCP.  Not a deal breaker 
necessarily, but something to keep in mind.

rick jones