Packets get dropped at Mac-Low

[harald...@gmail.com]

My topology looks like the following

Server ----------p2p-----------AP*   *WLAN*     *client0

                                                                      *client1

Clients request segment sizes between 100.000 bytes and 15.000.000 bytes (sometimes even 25.000.000 bytes) from server.

So what happens:

I look at the output of the pcap file from the APs point of view and after around 80 seconds, client1 has an enormous drop of throughput, barely every 1 sec an ACK arrives at the server.

So I look at the output of ApWifiMac, and all the packets the server sends get enqueued and therefore sent down to Mac Low Layer.

So I look at the output of the Mac Low Layer and I see that client1 just doesn't get to using the WiFi channel.

Over 300 seconds of simulation time, 

client0 has 1.733 "rx drop CTL_BACKRESP"

client1 has 49.121 "rx drop CTL_BACKRESP"

And it gets worse: At around 125 seconds the Access Point does not forward a single packet that he receives from the server to client1.

They all seem to be getting dropped.

Even after client0 is finished (after 422 seconds), the AP doesn't proceed sending packets to client1.

I've attached my set-up

the command to reproduce my results is

./waf --run="tcp-stream --simulationId=0 --numberOfClients=2 --adaptationAlgo=tobasco --segmentDuration=2000000 --segmentSizeFile=bitrates.txt"

[harald...@gmail.com]

After further investigation of the log-level-all outputs of MacLow, it seems as if client1 just very rare is granted access to the WiFi channel starting at around 80 seconds.

Later he gets granted access in so big time interval, that at some point it looks like he just seems to be giving up.

As stated before, this is not the case before 80 seconds, this starts all of a sudden and I have no idea why. It then ramps up a little bit a

Client0 just keeps communicating with the AP, and client1 is not experiencing any fairness.

How is this possible?

This looks to me like some problem in the framework, or I am missing something else completely.

This can't have anything to do with my Application Layer, because when I do this simulation connecting clients with a CSMA with the server, there are no problems. I can even do 10 clients at a time.

This is only a problem at the WiFi-Component.

[harald...@gmail.com]

It seems like I've been able to solve this, hope it will be of help to anyone in the future:

The data rate on the p2p link must not be higher than the maximum theoretical data rate on the WLAN, which is 600Mbit when using 4 antennas