[NS] Strange simulation result

[Shen Ren]

Hi, All,
	I am sending one packet from a cbr agent to another node using
NOAH, however, on the mac layer, I find there are all together 5 sending
operation. 
	Among the 5 send operation, I found only the first one is the
real data send operation from node (1 1). The other four might be the
ACK packets sending back from the node (20 20). But why does it send 4
ACK packets back????  One ACK is enough, I think.
	Anyone know what happened? Below is the simulation result: Thank
u first

s -t 5.000675000 -Hs 0 -Hd -2 -Ni 0 -Nx 1.00 -Ny 1.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw --- -Ma 0 -Md ffffffff -Ms 0 -Mt 806 -P arp -Po
REQUEST -Pms 0 -Ps 0 -Pmd 0 -Pd 1

r -t 5.001315090 -Hs 1 -Hd -2 -Ni 1 -Nx 20.00 -Ny 20.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw --- -Ma 0 -Md ffffffff -Ms 0 -Mt 806 -P arp -Po
REQUEST -Pms 0 -Ps 0 -Pmd 0 -Pd 1

s -t 5.001990090 -Hs 1 -Hd -2 -Ni 1 -Nx 20.00 -Ny 20.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw --- -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

d -t 5.002630179 -Hs 0 -Hd -2 -Ni 0 -Nx 1.00 -Ny 1.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw BSY -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

s -t 5.003618090 -Hs 1 -Hd -2 -Ni 1 -Nx 20.00 -Ny 20.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw --- -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

d -t 5.004258179 -Hs 0 -Hd -2 -Ni 0 -Nx 1.00 -Ny 1.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw BSY -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

s -t 5.005246090 -Hs 1 -Hd -2 -Ni 1 -Nx 20.00 -Ny 20.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw --- -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

d -t 5.005886179 -Hs 0 -Hd -2 -Ni 0 -Nx 1.00 -Ny 1.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw BSY -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

s -t 5.006874090 -Hs 1 -Hd -2 -Ni 1 -Nx 20.00 -Ny 20.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw --- -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

d -t 5.007514179 -Hs 0 -Hd -2 -Ni 0 -Nx 1.00 -Ny 1.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw BSY -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

d -t 5.007832090 -Hs 1 -Hd -2 -Ni 1 -Nx 20.00 -Ny 20.00 -Nz 0.00 -Ne
-1.000000 -Nl MAC -Nw RET -Ma 13a -Md 0 -Ms 1 -Mt 806 -P arp -Po REPLY
-Pms 1 -Ps 1 -Pmd 0 -Pd 0

d -t 10.000000000 -Hs 0 -Hd 1 -Ni 0 -Nx 1.00 -Ny 1.00 -Nz 0.00 -Ne
-1.000000 -Nl IFQ -Nw END -Ma 0 -Md 0 -Ms 0 -Mt 800 -Is 0.0 -Id 1.0 -It
cbr -Il 25 -If 0 -Ii 0 -Iv 32 -Pn cbr -Pi 0 -Pf 0 -Po 0