1

In a NS3 network simulation, I'm trying to transmit packets from 40 echo clients to a central echo server using OLSR routing on 802.11 simultaneously.

However, only eight of these packets are consistently received by the server. (Imgur Link)

If, however, I try to serve the packets individually at an interval of 0.1s from each station, it seems to work fine.

Is this a protocol limit?

Sorry, I'm kind of new to networking but I tried to explain it as well as I could.

Please wait, populating routing tables (30s)....
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32s client sent 1024 bytes to 10.1.3.1 port 9
At time 32.0029s server received 1024 bytes from 10.1.3.3 port 49153
At time 32.0029s server sent 1024 bytes to 10.1.3.3 port 49153
At time 32.0089s server received 1024 bytes from 10.1.3.5 port 49153
At time 32.0089s server sent 1024 bytes to 10.1.3.5 port 49153
At time 32.0108s server received 1024 bytes from 10.1.3.12 port 49153
At time 32.0108s server sent 1024 bytes to 10.1.3.12 port 49153
At time 32.0299s server received 1024 bytes from 10.1.3.13 port 49153
At time 32.0299s server sent 1024 bytes to 10.1.3.13 port 49153
At time 32.0317s client received 1024 bytes from 10.1.3.1 port 9
At time 32.0631s client received 1024 bytes from 10.1.3.1 port 9
At time 32.0651s client received 1024 bytes from 10.1.3.1 port 9
At time 33.0049s client received 1024 bytes from 10.1.3.1 port 9
At time 33.0158s server received 1024 bytes from 10.1.3.25 port 49153
At time 33.0158s server sent 1024 bytes to 10.1.3.25 port 49153
At time 33.0294s server received 1024 bytes from 10.1.3.18 port 49153
At time 33.0294s server sent 1024 bytes to 10.1.3.18 port 49153
At time 33.038s server received 1024 bytes from 10.1.3.28 port 49153
At time 33.038s server sent 1024 bytes to 10.1.3.28 port 49153
At time 33.0495s client received 1024 bytes from 10.1.3.1 port 9
At time 33.0611s client received 1024 bytes from 10.1.3.1 port 9
At time 33.068s client received 1024 bytes from 10.1.3.1 port 9
At time 34.0066s server received 1024 bytes from 10.1.3.41 port 49153
At time 34.0066s server sent 1024 bytes to 10.1.3.41 port 49153
At time 34.0153s client received 1024 bytes from 10.1.3.1 port 9

2

802.11 is CSMA/CA, so there is no "simultaneous transmission." Stations wait until the channel is clear and then begin transmitting. So only one station transmits at a time. My guess is some of your stations never see an idle channel.

| improve this answer | |
  • Normally, a stochastic backoff algorithm is applied specifically to avoid these stalls ... – BatchyX Feb 16 '14 at 15:48
  • I agree. I wonder, though, how well his simulator simulates that. – Ron Trunk Feb 17 '14 at 14:21

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