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// bounded retransmission protocol [D'AJJL01]
// gxn/dxp 23/05/2001
dtmc
// number of chunks
const int N = 16;
// maximum number of retransmissions
const int MAX = 2;
// reliability of channels
const double pL;
const double pK;
// timeouts
const double TOMsg;
const double TOAck;
module sender
s : [0..6];
// 0 idle
// 1 next_frame
// 2 wait_ack
// 3 retransmit
// 4 success
// 5 error
// 6 wait sync
srep : [0..3];
// 0 bottom
// 1 not ok (nok)
// 2 do not know (dk)
// 3 ok (ok)
nrtr : [0..MAX];
i : [0..N];
bs : bool;
s_ab : bool;
fs : bool;
ls : bool;
// idle
[NewFile] (s=0) -> (s'=1) & (i'=1) & (srep'=0);
// next_frame
[aF] (s=1) -> (s'=2) & (fs'=(i=1)) & (ls'=(i=N)) & (bs'=s_ab) & (nrtr'=0);
// wait_ack
[aB] (s=2) -> (s'=4) & (s_ab'=!s_ab);
[TO_Msg] (s=2) -> (s'=3);
[TO_Ack] (s=2) -> (s'=3);
// retransmit
[aF] (s=3) & (nrtr<MAX) -> (s'=2) & (fs'=(i=1)) & (ls'=(i=N)) & (bs'=s_ab) & (nrtr'=nrtr+1);
[] (s=3) & (nrtr=MAX) & (i<N) -> (s'=5) & (srep'=1);
[] (s=3) & (nrtr=MAX) & (i=N) -> (s'=5) & (srep'=2);
// success
[] (s=4) & (i<N) -> (s'=1) & (i'=i+1);
[] (s=4) & (i=N) -> (s'=0) & (srep'=3);
// error
[SyncWait] (s=5) -> (s'=6);
// wait sync
[SyncWait] (s=6) -> (s'=0) & (s_ab'=false);
endmodule
module receiver
r : [0..5];
// 0 new_file
// 1 fst_safe
// 2 frame_received
// 3 frame_reported
// 4 idle
// 5 resync
rrep : [0..4];
// 0 bottom
// 1 fst
// 2 inc
// 3 ok
// 4 nok
fr : bool;
lr : bool;
br : bool;
r_ab : bool;
recv : bool;
// new_file
[SyncWait] (r=0) -> (r'=0);
[aG] (r=0) -> (r'=1) & (fr'=fs) & (lr'=ls) & (br'=bs) & (recv'=T);
// fst_safe_frame
[] (r=1) -> (r'=2) & (r_ab'=br);
// frame_received
[] (r=2) & (r_ab=br) & (fr=true) & (lr=false) -> (r'=3) & (rrep'=1);
[] (r=2) & (r_ab=br) & (fr=false) & (lr=false) -> (r'=3) & (rrep'=2);
[] (r=2) & (r_ab=br) & (fr=false) & (lr=true) -> (r'=3) & (rrep'=3);
[aA] (r=2) & !(r_ab=br) -> (r'=4);
// frame_reported
[aA] (r=3) -> (r'=4) & (r_ab'=!r_ab);
// idle
[aG] (r=4) -> (r'=2) & (fr'=fs) & (lr'=ls) & (br'=bs) & (recv'=T);
[SyncWait] (r=4) & (ls=true) -> (r'=5);
[SyncWait] (r=4) & (ls=false) -> (r'=5) & (rrep'=4);
// resync
[SyncWait] (r=5) -> (r'=0) & (rrep'=0);
endmodule
// prevents more than one file being sent
module tester
T : bool;
[NewFile] (T=false) -> (T'=true);
endmodule
module channelK
k : [0..2];
// idle
[aF] (k=0) -> 1-pK : (k'=1) + pK : (k'=2);
// sending
[aG] (k=1) -> (k'=0);
// lost
[TO_Msg] (k=2) -> (k'=0);
endmodule
module channelL
l : [0..2];
// idle
[aA] (l=0) -> 1-pL : (l'=1) + pL : (l'=2);
// sending
[aB] (l=1) -> (l'=0);
// lost
[TO_Ack] (l=2) -> (l'=0);
endmodule
label "error" = s=5;
rewards
[TO_Msg] true : TOMsg;
[TO_Ack] true : TOAck;
endrewards