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GBN_cumulative_ack.h
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GBN_cumulative_ack.h
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//
// Created by Subangkar on 26-Jan-19.
//
#include "Utils.h"
#ifndef RDT_GBN_H
#define RDT_GBN_H
#define BIDIRECTIONAL 0 /* change to 1 if you're doing extra credit */
/* and write a routine called B_output */
/* a "msg" is the data unit passed from layer 5 (teachers code) to layer */
/* 4 (students' code).It contains the data (characters) to be delivered */
/* to layer 5 via the students transport level protocol entities.*/
struct msg {
char data[20];
};
/* a packet is the data unit passed from layer 4 (students code) to layer */
/* 3 (teachers code).Note the pre-defined packet structure, which all */
/* students must follow.*/
struct pkt {
int seqnum;
int acknum;
int checksum;
char payload[20];
};
/// base-nextseq-cnt3-cnt5-windBuf-msgBuf
struct rtp_layer_gbn_t {
int base;// current send base
int nextseqnum;// current expected seq
int cnt_layer3;// kept only for stat
int cnt_layer5;// kept only for stat
pkt *windowbuffer;// congestion windows buffer
std::queue<msg> *msgbuffer;// extra buffer
};
/********* FUNCTION PROTOTYPES.DEFINED IN THE LATER PART******************/
void tolayer3(int AorB, struct pkt packet);
void tolayer5(int AorB, char datasent[20]);
void printLog(int AorB, char *msg, const struct pkt *p, struct msg *m);
void printStat();
int calc_checksum(const pkt *p);
pkt make_pkt(msg message, int seqNum, int ackNum = ACK_ABP_DEFAULT);
pkt make_pkt(const char data[MSG_LEN], int seqNum, int ackNum);
///============================ Timer Functions ============================
/* Multiple timer implemented in cpp with single timer using following functions */
void starttimer(int AorB, float increment);
void startTimer(int AorB, int timerNo, float increment);
void stoptimer(int AorB);
void stopTimer(int AorB, int timerNo = 0);
void resetTimers(int AorB);
void clearTimerFlag(int AorB);
///=========================================================================
/********* STUDENTS WRITE THE NEXT SEVEN ROUTINES *********/
void A_output(msg);
#define A 0
#define B 1
#define TIMEOUT 40.0
#define EXTRA_BUFFER_SIZE 50
#define SEQ_NUM_SIZE 8
#define WINDOW_SIZE 7
std::queue<msg> A_buffer;
pkt A_window[SEQ_NUM_SIZE];
rtp_layer_gbn_t A_rtp, B_rtp;
bool windowIsEmpty(const rtp_layer_gbn_t &rtp_layer) {
return rtp_layer.nextseqnum == rtp_layer.base;
}
bool windowIsFull(const rtp_layer_gbn_t &rtp_layer) {
return rtp_layer.nextseqnum == ((rtp_layer.base + WINDOW_SIZE) % SEQ_NUM_SIZE);
}
void slideWindowForward(int acknum) {
rtp_layer_gbn_t &rtp_layer = A_rtp;
if (acknum == rtp_layer.nextseqnum)return;// ack num out of window
int count = (acknum - rtp_layer.base + 1 + SEQ_NUM_SIZE) % SEQ_NUM_SIZE;
rtp_layer.base = (acknum + 1) % SEQ_NUM_SIZE;
for (int i = 0; i < count; ++i) stopTimer(A);
//when the window size decrease, check the
//extra buffer, if we need any message need to send
while (count > 0 && !A_rtp.msgbuffer->empty()) {
msg message = A_rtp.msgbuffer->front();
A_rtp.msgbuffer->pop();
A_output(message);
count--;
}
}
/* adds a packet at last of the window and also forwards nextseqnum */
void addPacketToWindow(rtp_layer_gbn_t &rtp_layer, pkt &packet) {
rtp_layer.windowbuffer[rtp_layer.nextseqnum] = packet;
rtp_layer.nextseqnum = (rtp_layer.nextseqnum + 1) % SEQ_NUM_SIZE;
}
void retransmitCurrentWindow(rtp_layer_gbn_t &rtp_layer) {
for (int i = rtp_layer.base; i != rtp_layer.nextseqnum; i = (i + 1) % SEQ_NUM_SIZE) {
tolayer3(A, rtp_layer.windowbuffer[i]);
startTimer(A, i, TIMEOUT);
++A_rtp.cnt_layer3;
printLog(A, const_cast<char *>(">Resend the packet again"), &rtp_layer.windowbuffer[i], NULL);
}
}
/* called from layer 5, passed the data to be sent to other side */
/* Every time there is a new packet come,
* a) append this packet at the end of the extra buffer.
* b) check the window is full or not; If the window is full, we just leave the packet in the extra buffer;
* c) If the window is not full, retrieve one packet at the beginning of the extra buffer, and process it.*/
void A_output(struct msg message) {
rtp_layer_gbn_t &rtp_layer = A_rtp;
printLog(A, const_cast<char *>("Receive an message from layer5"), NULL, &message);
if (rtp_layer.msgbuffer->size() >= EXTRA_BUFFER_SIZE) {
++nDroppedMessages;
printLog(A, const_cast<char *>("Extra Buffer full. Dropping Message!!!"), nullptr, &message);
return;
}
rtp_layer.msgbuffer->push(message);
/// if windows is full then just push
if (windowIsFull(A_rtp)) {
printLog(A, const_cast<char *>("Window is full already, save message to extra buffer"), NULL, &message);
return;
}
// if windows is not full then current message is the only message in buffer
rtp_layer.msgbuffer->pop();
++rtp_layer.cnt_layer5;
printLog(A, const_cast<char *>("Processed an message from layer5"), NULL, &message);
pkt packet = make_pkt(message, rtp_layer.nextseqnum, ACK_GBN_DEFAULT);
addPacketToWindow(rtp_layer, packet);//nextseqnum is updated here
tolayer3(A, packet);
startTimer(A, rtp_layer.nextseqnum, TIMEOUT);
++rtp_layer.cnt_layer3;
printLog(A, const_cast<char *>("Send packet to layer3"), &packet, &message);
}
void B_output(struct msg message) {
}
/* called from layer 3, when a packet arrives for layer 4 */
void A_input(struct pkt packet) {
rtp_layer_gbn_t &rtp_layer = A_rtp;
printLog(A, const_cast<char *>("Receive ACK packet from layer3"), &packet, NULL);
/* Corrupted ACK -> ignore */
if (packet.checksum != calc_checksum(&packet)) {
printLog(A, const_cast<char *>("ACK packet is corrupted"), &packet, NULL);
return;
}
/* Duplicate ACK: NACK -> resend all */
if (packet.acknum == ((rtp_layer.base + WINDOW_SIZE) % SEQ_NUM_SIZE)) {
printLog(A, const_cast<char *>("Received duplicate ACK"), &packet, NULL);
resetTimers(A);
retransmitCurrentWindow(A_rtp);
return;
}
/* go to the next base,seq and stop the timer */
slideWindowForward(packet.acknum);
printLog(A, const_cast<char *>("ACK packet processed successfully !!"), &packet, NULL);
}
/* called when A's timer goes off */
void A_timerinterrupt() {
clearTimerFlag(A);
resetTimers(A);
rtp_layer_gbn_t &rtp_layer = A_rtp;
if (windowIsEmpty(rtp_layer)) {
perror(">> Problem: timer interrupt occurred with empty window\n");
return;
}
printLog(A, const_cast<char *>("Timer interrupt occurred"), NULL, NULL);
/* if current packets not ACKed, resend it */
retransmitCurrentWindow(rtp_layer);
}
/* the following routine will be called once (only) before any other */
/* entity A routines are called.You can use it to do any initialization */
void A_init() {
A_rtp = {0, 0, 0, 0, nullptr, nullptr};
A_rtp.msgbuffer = &A_buffer;
A_rtp.windowbuffer = A_window;
}
/* Note that with simplex transfer from a-to-B, there is no B_output() */
/* called from layer 3, when a packet arrives for layer 4 at B*/
bool ackTimerStarted = false;
void B_input(struct pkt packet) {
rtp_layer_gbn_t &rtp_layer = B_rtp;
printLog(B, const_cast<char *>("Receive a packet from layer3"), &packet, NULL);
++rtp_layer.cnt_layer3;
/* if corrupted, just drop the package */
if (packet.checksum != calc_checksum(&packet)) {
printLog(B, const_cast<char *>("Packet is corrupted"), &packet, NULL);
// return;
} else if (packet.seqnum == rtp_layer.nextseqnum) {
/* normal packet, deliver data to layer5 */
tolayer5(B, packet.payload);
rtp_layer.nextseqnum = (rtp_layer.nextseqnum + 1) % SEQ_NUM_SIZE;
++rtp_layer.cnt_layer5;
printLog(B, const_cast<char *>("Send packet to layer5"), &packet, NULL);
if (!ackTimerStarted) {
printLog(B, const_cast<char *>("Cumulative Timer Started!!!"), nullptr, nullptr);
starttimer(B, static_cast<float>(TIMEOUT * 0.6));
ackTimerStarted = true;
}
return;
} else {
/* duplicate packet, resend the latest ACK again */
printLog(B, const_cast<char *>("Disordered packet received"), &packet, NULL);
}
if (ackTimerStarted) {
stoptimer(B);
ackTimerStarted = false;
}
/* send back ACK with the last received seqnum */
packet.acknum = (rtp_layer.nextseqnum + SEQ_NUM_SIZE - 1) % SEQ_NUM_SIZE; /* resend the latest ACK */
packet.checksum = calc_checksum(&packet);
tolayer3(B, packet);
printLog(B, const_cast<char *>("Send NACK packet to layer3"), &packet, NULL);
}
/* called when B's timer goes off */
void B_timerinterrupt() {
printLog(B, const_cast<char *>("Timer interrupt occurred @B !!!"), nullptr, nullptr);
pkt packet = make_pkt("ack_packet", 0xFF, (B_rtp.nextseqnum + SEQ_NUM_SIZE - 1) % SEQ_NUM_SIZE);
ackTimerStarted = false;
tolayer3(B, packet);
printLog(B, const_cast<char *>("Send cumulative ACK packet to layer3"), &packet, NULL);
}
/* the following rouytine will be called once (only) before any other */
/* entity B routines are called.You can use it to do any initialization */
void B_init() {
B_rtp = {0, 0, 0, 0, nullptr, nullptr};
}
//===================== Utils =====================
int calc_checksum(const pkt *p) {
calc_checksum(p->seqnum, p->acknum, p->payload);
}
pkt make_pkt(msg message, int seqNum, int ackNum) {
pkt packet = {seqNum, ackNum, 0, ""};
strncpy(packet.payload, message.data, MSG_LEN);
packet.checksum = calc_checksum(&packet);
return packet;
}
pkt make_pkt(const char data[MSG_LEN], int seqNum, int ackNum) {
pkt packet = {seqNum, ackNum, 0, ""};
strncpy(packet.payload, data, MSG_LEN);
packet.checksum = calc_checksum(&packet);
return packet;
}
//===================== Log Files ==================
void writeLog(FILE *fp, int AorB, char *msg, const struct pkt *p, struct msg *m, float time) {
char ch = (AorB == A) ? 'A' : 'B';
if (AorB == A) {
if (p != NULL) {
fprintf(fp, "[%c] @%f %s.Window[%d,%d) Packet[seq=%d,ack=%d,check=%d,data=%s..]\n", ch, time, msg,
A_rtp.base, A_rtp.nextseqnum, p->seqnum, p->acknum, p->checksum, p->payload);
} else if (m != NULL) {
fprintf(fp, "[%c] @%f %s.Window[%d,%d) Message[data=%s..]\n", ch, time, msg, A_rtp.base, A_rtp.nextseqnum,
m->data);
} else {
fprintf(fp, "[%c] @%f %s.Window[%d,%d)\n", ch, time, msg, A_rtp.base, A_rtp.nextseqnum);
}
} else {
if (p != NULL) {
fprintf(fp, "[%c] @%f %s.Expected[%d] Packet[seq=%d,ack=%d,check=%d,data=%s..]\n", ch, time, msg,
B_rtp.nextseqnum, p->seqnum, p->acknum, p->checksum, p->payload);
} else if (m != NULL) {
fprintf(fp, "[%c] @%f %s.Expected[%d] Message[data=%s..]\n", ch, time, msg, B_rtp.nextseqnum, m->data);
} else {
fprintf(fp, "[%c] @%f %s.Expected[%d]\n", ch, time, msg, B_rtp.nextseqnum);
}
}
}
void printStat() {
printf("#Sent Messages from Layer5-to A: %d\n", A_rtp.cnt_layer5);
printf("#Sent Messages to Layer3-from A: %d\n", A_rtp.cnt_layer5 - nDroppedMessages);
printf("#Sent Packets to Layer3-from A: %d\n", A_rtp.cnt_layer3);
printf("#Sent Packets from Layer3-to B: %d\n", B_rtp.cnt_layer3);
printf("#Sent Messages to Layer5-from B: %d\n", B_rtp.cnt_layer5);
}
#endif //RDT_GBN_H