hi matthias
Dear colleagues,
Currently we are looking for a magic tool with which it is possible to
generate specific (realistic) traffic patterns between client and server
to analyze (monitor) traffic characteristics (jitter, delay, inter
arrival times, etc.).
generating traffic and monitoring traffic is usually not done
by the same apps .... there's hundreds of monitoring apps
and hundreds of traffic generators
delay is done very nicely by dummynet in FreeBSD or
(untested by me ) with NS3 in linux
i don't understand simulating jitter, but, one can always use
"delay + random number"
It would be good if that wanted tool is not only able to generate
different traffic patterns
if you want to play with the headers ... that'd imply playing with
nmap/hping3/socat and dozens of other equivalent apps
if you're just trying to flood the wire ... nc/socat/iperf etc
but also is able to collect different traffic
metrics over time. So that it is possible to create catchy plots. 
"what metrics" you want to collect and how to you want to see it
would dictate which apps you'd be using
  - tcp queue/buffers
  - dropped packets
  - delays
  - retries
  - udp vs tcp vs icmp vs ...
  - stuff ...
xmit/recv buffers in the hardware, default buffers in the OS and
buffers in the software apps must all be tuned to the same gigE
or 10gigE speeds otherwise, whacky stuff will happen
for "catchy plots", you'd want gnuplot so you can (infinitely) zoom in
into the section you want to see dot-by-dot
for big picture ... netstat, ntop, (not much info) mrtg, etc, etc
big list of apps
  Packet-Craft.net/Apps
Any hints or links would be greatly appreciated.
if you're a proficient python'er, you'd probably like scapy
which can do everything you'd need to customize any packet
magic pixie dust
alvin