[ns] Problems with FEC, Poisson and Errmodel

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hello,all
now,I am modelling random losses in the incoming link (uplink) and congestion losses at node, I consider an M/M/1 queue with a finite buffer of size K,and I assume that losses can caused either by a buffer overflow or randomly with probability r in the incoming link .The arrival process from the source is assumed to be Poisson with rate ¦Ë and the service times of packets is exponentially distributed with rate ¦Ì.My scene for the model is as follows:
I use three mobile nodes,node(0),node(1) and node(2). node(1) forwards the packets from node(0) to node(2).and now I have two problems:
(1) how to apply the errmodel to the incoming link with a random loss probability whose value is r;
(2) how to implement the arrival process from the source is the Poisson with rate ¦Ë;
(3) how to add FEC to the model 
I am a NS-begniner ,can anyone give some help ,thank you very much !


       
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