[Click] LinkUnqueue multiple flows shaping issues

[milos rovcanin]

Greetings to all,

I have noticed an awkward behaviour of the LinkUnqueue() element when trying
to send two flows at the same time (UDP/UDP, TCP/TCP, UDP/UDP). This is,
pretty much, what my configuration looks like:

 ...
  ->Qtag0::Queue(20)
  -> LinkUnqueue(LATENCY 0,BANDWIDTH 13000000 bps)
  -> Queue()
  -> [0]output;

 ...
  -> Qtag1::Queue(20)
  -> LinkUnqueue(LATENCY 0,BANDWIDTH 9000000 bps)
  -> Queue()
  -> [1]output;

and while I am sending at rates lower than the ones defined in the
LinkUnqueue() element, everything seems to be working fine. Problems start
to occur when one or both of the flows exceed the threshold. In other words,
when LinkUnque() starts to shape. Both flow rates drop significantly, but
only if the packet size is over 850 bytes! For example, if I use MSS of 1000
bytes, everything work fine even with higher rates.

I used Clicky to check the status of the LinkUnqueue() element and I noticed
this:
- Qtag0/Qtag1 lenghts are 1 all the time and LinkEnqueue's handler
"scheduled" is true - when I send smaller packets (the ones that cause
problems)
- Qtag0/Qtag1 gets immediately full all the time and LinkEnqueue's handler
"scheduled" is false - when I send larger packets (~850B and larger)

Does anyone have any idea what could be the problem and how to solve it?

Thank you in advance!

-- 
Milos Rovcanin
Department of Information Technology
Internet Based Communication Networks and Services research group (IBCN)
Ghent University - IBBT
Gaston Crommenlaan 8 (Bus 201), B-9050 Gent, Belgium
T: +32 9 33 14946 ; T Secr: +32 9 33 14900
E: Milos.Rovcanin at intec.UGent.be
W: www.ibcn.intec.UGent.be