Flow dan Error Control

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while(true) // ulangi selamanya

{

WaitForEvent(); // sleep sampai terjadi event

if(Event(RequestToSend)) // ada paket untuk dikirim {

GetData(); MakeFrame();

SendFrame(); // kirim frame

} }

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{

if(Event(ArrivalNotification)) // Frame data diterima {

ReceiveData(); ExtractData();

DeliverData(); // kirim data ke network layer

} }

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canSend = true // ijinkan frame pertama dikirim

{

if(Event(RequestToSend) AND canSend) {

GetData(); MakeFrame();

SendFrame(); // kirim frame

canSend = false; // tidak bisa kirim sampai ACK

}

WaitForEvent() // sleep sampai terjadi event

if(Event(ArrivalNotification)) // ACK diterima {

ReceiveFrame(); // frame ACK diterima

canSend = true; } }

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{

ReceiveData(); ExtractData();

SendFrame(); // kirim frame ACK

} }

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Sn = 0; // frame 0 hrs dikirim dulu

canSend = true; // ijinkan request pertama dikirim

{

if(Event(RequestToSend) AND canSend) {

GetData();

MakeFrame(Sn); // nomor urut Sn

StoreFrame(Sn); // simpan salinannya

SendFrame(Sn); // kirim frame

StartTimer(); Sn = Sn + 1; canSend = false; }

WaitForEvent() // sleep sampai terjadi event

if(Event(ArrivalNotification)) // ACK diterima {

ReceiveFrame(ackNo); // frame ACK diterima if(Not corrupted AND ackNo == Sn) // ACK valid {

StopTimer();

PurgeFrame(Sn-1); // frame tidak perlu lagi

canSend = true; }

}

If(Event(TimeOut)) // timer expired

{

StartTimer();

ResendFrame(Sn-1); // kirim ulang salinan

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Rn = 0; // frame 0 diharapkan dtg dulu

{

ReceiveFrame(); If(corrupted(frame)); Sleep();

If(seqNo == Rn) // no frame valid

{

ExtractData();

Rn= Rn + 1; }

SendFrame(Rn); // kirim frame ACK

} }

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Sw = 2m – 1; Sf = 0; Sn = 0;

While(true) // ulangi terus

{

WaitForEvent();

If(Event(RequestToSend)) // jika paket hendak dikirim {

If(Sn-Sf >= Sw) // jika window penuh

Sleep(); GetData(); MakeFrame(Sn); StoreFrame(Sn); SendFrame(sn); Sn = Sn + 1;

If(timer not running) StartTimer(); }

If(event(ArrivalNotification)) // ACK dtg {

Receive(ACK); If(corrupted(ACK)) Sleep();

If((ackNo>Sf)&&(ackNo<=<=Sn)) // jika ACK valid While(Sf <= ackNo)

{

(11)

31 32 33 34 35 36 37 38 39 40 41 42 43 44 StopTimer(); }

If(event(TimeOut)) // timer expires

{

StartTimer(); Temp = Sf; While(Temp < Sn) {

SendFrame(Sf); Sf = Sf + 1; } } }

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Rn = 0; // frame 0 diharapkan dtg dulu

{

ReceiveFrame(); If(corrupted(frame)); Sleep();

If(seqNo == Rn) // no frame valid

{

Rn= Rn + 1; SendACK(Rn); }

} }

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Sw = 2m – 1; Sf = 0; Sn = 0;

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$ $$ $ 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 { WaitForEvent();

If(Event(RequestToSend)) // jika paket hendak dikirim {

If(Sn-Sf >= Sw) // jika window penuh

Sleep(); GetData(); MakeFrame(Sn); StoreFrame(Sn); SendFrame(sn); Sn = Sn + 1; StartTimer(Sn); }

If(event(ArrivalNotification)) // ACK dtg {

Receive(frame); // terima ACK atau NAK

If(corrupted(frame)) Sleep();

If(FrameType == NAK)

If(nakNo betweeen Sf and Sn) {

Resend(nakNo); StartTimer(nakNo); }

If(FrameType == ACK)

If(nakNo between Sf and Sn) {

While(Sf<ackNo) {

Purge(Sf); StopTimer(Sf); Sf = Sf +1; }

} }

If(event(TimeOut(t))) // timer expires

{ StartTimer(t); SendFrame(t); } }

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Rn = 0;

Naksent = false; Ackneeded = false; Repeat(for all slots) Marked(slot) = false;

{

ReceiveFrame();

If(corrupted(frame) && (NOT naksent) {

(14)

& && & 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 }

If(seqNo <> Rn) && (NOT naksent) {

sendNAK(Rn); naksent = true;

if((seqNo in window) && (!marked(seqno)) {

Storeframe(seqno) Marked(seqno) = true; While(marked(Rn)) {

DeliverData(Rn); Purge(Rn); Rn = Rn + 1; Ackneeded = true; }

If(ackneeded) {

Sendack(Rn); Ackneeded = false; Naksent = false; }

} } } }

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