[ns] Why the message is not delivered (ARP requests lost?)

["YY YY" <yy_yaoyong@hotmail.com>]

Hi, there:

I am using ns2 to simulate the ad hoc network and the routing protocol is 
directed diffusion. The scenario is simple enough with only three nodes, one 
sink and three sources(one node has both a sink and a source). When two 
nodes unicast positive reinforcement messages to the third one 
simultaneously, only one message is delivered. I checked the trace file and 
found that both nodes sended an ARP request first, but only one is received 
by the destination. So only one ARP reply message is generated. The network 
is far from overload and the lost positive message is critical to the 
protocol. I don't understand why only the ARP Requests are dropped. Is it 
because of confict? But all data messages are delivered successfully.

Thanks a lot.

Yong


Node 1 sends Pos to 0; (Generate ARP request)
Node 2 sends Pos to 0; (Generate ARP request)

0 receivs 1's request and replies;
0 doesn't receive the ARP request from 2;

r 0.117095713 _2_ AGT  --- 16 diffusion 36 [0 0 0 0] [energy 9999.994047] 
------- [2:255 2:0 32 0]
s 0.117150647 _1_ MAC  --- 0 ARP 80 [0 ffffffff 1 806] [energy 9999.994017] 
------- [REQUEST 1/1 0/0]
s 0.117150713 _2_ MAC  --- 0 ARP 80 [0 ffffffff 2 806] [energy 9999.994047] 
------- [REQUEST 2/2 0/0]
r 0.117470668 _0_ MAC  --- 0 ARP 28 [0 ffffffff 1 806] [energy 9999.994070] 
------- [REQUEST 1/1 0/0]
s 0.118329800 _0_ MAC  --- 0 MAC 44 [28f 1 0 0] [energy 9999.994070]
r 0.118505821 _1_ MAC  --- 0 MAC 44 [28f 1 0 0] [energy 9999.993703]
s 0.118515821 _1_ MAC  --- 0 MAC 38 [1ed 0 0 0] [energy 9999.993703]
r 0.118667841 _0_ MAC  --- 0 MAC 38 [1ed 0 0 0] [energy 9999.993863]
s 0.118717841 _0_ MAC  --- 0 ARP 80 [a2 1 0 806] [energy 9999.993863] 
------- [REPLY 0/0 1/1]
r 0.119037862 _1_ MAC  --- 0 ARP 28 [a2 1 0 806] [energy 9999.993475] 
------- [REPLY 0/0 1/1]
s 0.119047862 _1_ MAC  --- 0 MAC 38 [0 0 0 0] [energy 9999.993475]
r 0.119199883 _0_ MAC  --- 0 MAC 38 [0 0 0 0] [energy 9999.993590]

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