Re: [PATCH 2/2] net: netem: always adjust now/delay when not reordering

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 21 Aug 2013 10:00:17 -0700
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> On Wed, 2013-08-21 at 18:14 +0200, Ferry Huberts wrote:
> 
> > Well no. We expected no reordering because reordering is not enabled.
> 
> 
> Sending packets with random delays happening in the 'network' _will_
> reorder packets at the receiver.
> 
> The 'reorder' netem attribute is quite limited and not practical,
> because it only queues the packet at the head of the queue instead of
> tail. This is not what happens on the networks.
> 
> You want something very special, and this needs a new parameter to netem
> qdisc, or a new qdisc.
> 
> If I setup "netem rate 1Mbit delay 1000ms 50ms", and send a burst of 100
> small packets, I expect these _all_ packets reach the destination in
> less than 1050ms.
> 
> I do not want packet1 being delivered at t0+1020ms,
> packet2 being delivered at t0+1020+1030ms
> packet100 being delivered at t0+1020+1030++...+ = t0+~100sec
> 
> If your patch solves the problem, good, but I see no clear test of this.

The current behavior followed what NISTnet did. At the time, I wanted
NISTnet users to be able to use netem without a lot of surprises.
  http://www-x.antd.nist.gov/nistnet/