[ns] Lost Packets / Drops

[Renan Cunha]

Hi everyone,

I'm simulating a protocol for adhoc networks but I'm facing a problem with
packets loss. The configuration parameters are:

   set opt(chan)          Channel/WirelessChannel
   set opt(prop)          Propagation/TwoRayGround
   set opt(netif)         Phy/WirelessPhy
   set opt(mac)           Mac/802_11
   set opt(ifq)           Queue/DropTail/PriQueue
   set opt(ll)            LL
   set opt(ant)           Antenna/OmniAntenna
   set opt(eMod)          EnergyModel
   set opt(god)           on
   set opt(iEne)          50.0
   set opt(rxP)           0       ;
   set opt(txP)           0.0001       ;
   set opt(idlePower)     0000285  ;
   set opt(logeng)        "on"
   set opt(x)             50   ;# X dimension of the topography
   set opt(y)             50   ;# Y dimension of the topography
   set opt(ifqlen)        1000            ;# max packet in ifq
   set opt(seed)          0.0
   set opt(adhocRouting)  "NullRouter"
   set opt(nn)            50      ;# number of sensor nodes are simulated
   set opt(cp)            ""
   set opt(sc)          "./scn/scen- 50x50-50.sce"
   set opt(stop)          900            ;# simulation time
   set opt(tr)            "./log/out.tr"           ;# trace file
   set opt(nam)           ""        ;# nam file# Change here if needed
   set opt(range)      15

I've tried to disseminate my packets with broadcast but the amount of lost
packets was very high.
So, I've changed to unicast messages to the nodes' neighbors and the amount
of lost packets decreased. But I'm still losing important packets. In my
trace file I can see (END)

d -t 900.000100000 -Hs 40 -Hd -1 -Ni 40 -Nx 40.00 -Ny 40.00 -Nz 0.00 -Ne
28.976234 -Nl IFQ -Nw END -Ma 0 -Md 0 -Ms 28 -Mt 800 -Is 40.251 -Id
49.251-It INITCOLLECT -Il 0 -If 0 -Ii 868 -Iv 1 -Is
40.251 -Id 49.251 -It INITCOLLECT -Il 0 -If 0 -Ii 868 -Iv 1

and sometimes I read (ARP):

d -t 601.500028645 -Hs 20 -Hd -1 -Ni 20 -Nx 20.00 -Ny 20.00 -Nz 0.00 -Ne
35.574376 -Nl IFQ -Nw ARP -Ma 0 -Md 0 -Ms 14 -Mt 800 -Is 20.251 -Id
12.251-It INITCOLLECT -Il 0 -If 0 -Ii 334 -Iv 1 -Is
20.251 -Id 12.251 -It INITCOLLECT -Il 0 -If 0 -Ii 334 -Iv 1

and sometimes there is no drops in my trace file but I'm sure that some of
them were lost ( I count the amount of packets sent and the amount of of
packets received and they should match).

* Why are these packets (the ones that don't appear in the trace file) being
dropped?

* Why are those packets (the ones that show  "-Nw ARP" in the trace file)
being dropped?

* And, most important, what can I do to avoid these drops?

Thank you in advance.

Regards,
Renan