[ns] problem with bandwith_

[Laurent <lcavallin@run.montefiore.ulg.ac.be>]

Hi,

I make simulation in a wired-wireless environment.
the bandwith of the wired network is 2Mb/s, a node in the wired network
send 150KB by FTP to a node in the wireless environment (the mobile node
doesn't move in this simulation and  he is near is base station)
the others nodes do nothing.
the topology of the network is:
#
#           [N0] [N1]
#             \    |
#              \   |  2Mb/s + 10ms
#               \  |
#                [N2]
#                  |
#                  |  2Mb/s + 10ms
#                  |
#                [BS]
#
#
#
#        [MN0]                                [MN1]
#
#
#                         [MN2]
#

When the bandwith of the wireless channel is between 0.2Mb and 2Mb I
have no problem
but when I set it to 0.1Mb, I don't understand the trace file results:
Could you explain me this result?

I set the bandwith like this: Mac/802_11 set bandwidth_ 0.1Mb
I use ns 2.1b7 under SuSE 6.3 with kernel 2.2.18.

------------------------------------------------------------------------------------
M 0.0 nn 3 x 670 y 670 rp  DSDV
M 0.0 sc scen-3-test cp none seed 0.0
M 0.0 prop Propagation/TwoRayGround ant Antenna/OmniAntenna
M 5.00000 4194305 (5.00, 10.00, 0.00), (10.00, 20.00), 15.00
+ 10 0 2 tcp 1500 ------- 0 0.0.0.0 1.0.1.0 0 0
- 10 0 2 tcp 1500 ------- 0 0.0.0.0 1.0.1.0 0 0
M 10.00000 4194306 (50.00, 3.00, 0.00), (70.00, 20.00), 6.00
r 10.016 0 2 tcp 1500 ------- 0 0.0.0.0 1.0.1.0 0 0
+ 10.016 2 3 tcp 1500 ------- 0 0.0.0.0 1.0.1.0 0 0
- 10.016 2 3 tcp 1500 ------- 0 0.0.0.0 1.0.1.0 0 0
r 10.032 2 3 tcp 1500 ------- 0 0.0.0.0 1.0.1.0 0 0
d -t 10.725450939 -Hs 3 -Hd 4194305 -Ni 3 -Nx 1.00 -Ny 2.00 -Nz 0.00 -Ne
-1.000000 -Nl RTR -Nw CBK -Ma bea -Md 1 -Ms 0 -Mt 800 -Is 0.0 -Id
4194305.0 -It tcp -Il 1500 -If 0 -Ii 0 -Iv 29 -Pn tcp -Ps 0 -Pa 0 -Pf 0
-Po 0 
M 15.00000 4194305 (10.00, 20.00, 0.00), (18.00, 10.00), 8.00
+ 16 0 2 tcp 1500 ---A--- 0 0.0.0.0 1.0.1.0 0 1
- 16 0 2 tcp 1500 ---A--- 0 0.0.0.0 1.0.1.0 0 1
r 16.016 0 2 tcp 1500 ---A--- 0 0.0.0.0 1.0.1.0 0 1
+ 16.016 2 3 tcp 1500 ---A--- 0 0.0.0.0 1.0.1.0 0 1
- 16.016 2 3 tcp 1500 ---A--- 0 0.0.0.0 1.0.1.0 0 1
r 16.032 2 3 tcp 1500 ---A--- 0 0.0.0.0 1.0.1.0 0 1
d -t 16.704635615 -Hs 3 -Hd 4194305 -Ni 3 -Nx 1.00 -Ny 2.00 -Nz 0.00 -Ne
-1.000000 -Nl RTR -Nw CBK -Ma bea -Md 1 -Ms 0 -Mt 800 -Is 0.0 -Id
4194305.0 -It tcp -Il 1500 -If 0 -Ii 1 -Iv 29 -Pn tcp -Ps 0 -Pa 0 -Pf 0
-Po 0 
----------------------------------------------------------------------------------------

My simulation doesn't use error model so we can consider there is no
drop due to packet corruption.
But what is the meaning of this 2 drops (I already read the chap 16.1.6
in ns doc about the revised format for wireless traces).

Regards,
Laurent