Thanks. My problem is solved.
It seems to me paping can sample for the RTT over this particular port, not
the whole connection setup time. Maybe it only record for the sync time but
I am not fully sure. From the latency result, it is quite close to RTT of
the link.

-Mo


2013/12/5 Toke Høiland-Jørgensen <toke@toke.dk>

> Dong Mo <montedong@gmail.com> writes:
>
> > I also found this to sample tcp latency performance:
> > https://code.google.com/p/paping/
>
> Right; note that that measures time to establish a new connection, not
> the delay of packets within an already established connection. My guess
> would be that each established connection would have a new source port,
> thus hashing into a new bin.
>
> > Does fq_codel's flow classification supports external classifier
> > filter? Say I only want to hash on dst port in my case.
>
> I'm pretty sure it supports the normal classifier (tc filter). That
> overrides the built-in hashing completely, but IIRC you can do your own
> hashing in tc filter :)
>
> -Toke
>