For the second programming assignment you will be implementing a si...
Question
For the second programming assignment you will be implementing a simple reliable transport protocol. The protocol will be unidirectional. Host A will be sending segments, and Host B will be receiving and acknowledging those segments, but Host B will not be sending any application data of its own. Host A is the sender, Host B is the receiver.
1.First, read section 3.4.1 – "Building a Reliable Data Transfer Protocol" of Kurose and Ross, Computer Networking: A Top-Down Approach. You will be implementing the Alternating Bit protocol, which they call rdt3.0.
2.Read the directions, descriptions, and suggestions in the attached assignment description from the textbook authors carefully.
3.Examine the files prog2.c and prog2.py carefully. All of your code will be added to one of these files to fill in the function stubs. That is how you will implement rdt3.0 as a part of this network simulation program.
4.You must implement the following functions in prog2.py or prog2.c, please read their descriptions in the assignment description carefully.
a.A_init
b.A_output
c.A_input
d.A_timerinterrupt
e.B_init
f.B_input
5.Do not implement either B_output or B_timerinterrupt.Those functions are only required for a bi-directional version of the protocol. Please ignore these two function stubs.
6.Your implementation should include some output to STDOUT describing events that occur and protocol actions that are taken during the simulation. For example, message arrival, packet arrival, timer interrupt, or data corruption detection, etc. should all be reported to STDOUT. In addition, describe the actions your functions take in response. For example, building a packet, sending a packet, retransmitting a message, restarting the timer, etc. Part of your submission will be a trace of your program—we need output for the trace.
7.Try running the simulation program first – to see what it looks like before you start adding your own code.
8.Submit your source code, which should consist of a single file—your modified prog2.py or prog2.c
9.Submit a README that briefly explains your strategy for implementing each of the functions required rdt3.0.
10.Submit a trace of your completed program running to the point where about 10 messages have been sent and correctly acknowledged. Use the following settings: loss probability of 0.1, corruption probability of 0.3, and a trace level of 2. You can use screenshots, or you can redirect the output to a file. You might want to annotate your trace to indicate where interesting things happened (e.g., recovery from packet loss or packet corruption).
1.First, read section 3.4.1 – "Building a Reliable Data Transfer Protocol" of Kurose and Ross, Computer Networking: A Top-Down Approach. You will be implementing the Alternating Bit protocol, which they call rdt3.0.
2.Read the directions, descriptions, and suggestions in the attached assignment description from the textbook authors carefully.
3.Examine the files prog2.c and prog2.py carefully. All of your code will be added to one of these files to fill in the function stubs. That is how you will implement rdt3.0 as a part of this network simulation program.
4.You must implement the following functions in prog2.py or prog2.c, please read their descriptions in the assignment description carefully.
a.A_init
b.A_output
c.A_input
d.A_timerinterrupt
e.B_init
f.B_input
5.Do not implement either B_output or B_timerinterrupt.Those functions are only required for a bi-directional version of the protocol. Please ignore these two function stubs.
6.Your implementation should include some output to STDOUT describing events that occur and protocol actions that are taken during the simulation. For example, message arrival, packet arrival, timer interrupt, or data corruption detection, etc. should all be reported to STDOUT. In addition, describe the actions your functions take in response. For example, building a packet, sending a packet, retransmitting a message, restarting the timer, etc. Part of your submission will be a trace of your program—we need output for the trace.
7.Try running the simulation program first – to see what it looks like before you start adding your own code.
8.Submit your source code, which should consist of a single file—your modified prog2.py or prog2.c
9.Submit a README that briefly explains your strategy for implementing each of the functions required rdt3.0.
10.Submit a trace of your completed program running to the point where about 10 messages have been sent and correctly acknowledged. Use the following settings: loss probability of 0.1, corruption probability of 0.3, and a trace level of 2. You can use screenshots, or you can redirect the output to a file. You might want to annotate your trace to indicate where interesting things happened (e.g., recovery from packet loss or packet corruption).
Solution Preview
These solutions may offer step-by-step problem-solving explanations or good writing examples that include modern styles of formatting and construction of bibliographies out of text citations and references.
Students may use these solutions for personal skill-building and practice.
Unethical use is strictly forbidden.
#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];
};
/********* STUDENTS WRITE THE NEXT SEVEN ROUTINES *********/
void starttimer(int AorB, float increment);
void stoptimer(int AorB);
void tolayer3(int AorB, struct pkt packet);
void tolayer5(int AorB, char datasent[20]);
#define SWAP(x) (x == 0 ? 1 : 0)
#define A_B_RTT 15
int A_seq;
int A_waiting_ack;
struct pkt A_last_packet;
int B_seq;
int B_waiting_ack;
struct pkt B_last_packet;
// The checksum of a packet is calculated
//Take all the bits in the packet and do the summation
int calculate_checksum(struct pkt *packet){
int cs = 0;
cs += packet->seqnum;
cs += packet->acknum;
for (int i = 0; i < 20; ++i)
cs += packet->payload[i];
return cs;
}
/* called from layer 5, passed the data to be sent to other side */
void A_output(message)
struct msg message;
{
if (A_waiting_ack){
/* If A is waiting for ACK from B, ignore new packet from layer 5 */
printf("\tA_output: Waiting for ACK from B. Ignore new message: [%s]\n", message.data);
return;
}else{
/* A is waiting for upper layer, send new msg comming from layer 5 to B */
printf("\tA_output: Sending new message to B: [%s]\n", message.data);
/* Create new packet with the msg and send it to layer 3 below*/
struct pkt packet;
packet.seqnum = A_seq;
memmove(packet.payload, message.data, 20);
packet.checksum = calculate_checksum(&packet);
A_last_packet = packet;
A_waiting_ack = 1;
tolayer3(0, packet);
starttimer(0, A_B_RTT);
}
}
void B_output(message)
struct msg message;
{
}
/* called from layer 3, when a packet arrives for layer 4 */
void A_input(packet)
struct pkt packet;
{
/* if the checksum of the packet is not matching, ignore the packet.[ACK]*/
if (packet.checksum != calculate_checksum(&packet)){
printf("\tA_input: Corrupted packet received and droped.\n");
return;
}
/* if the sequence of the received ACK is not the expected sequence, drop it*/
if (packet.acknum != A_seq){
printf("\tA_input: Unexpected packet received and droped.\n");
return;
}
/* valid ACK received for last packet */
printf("\tA_input: ACK received for Last packet.\n");
stoptimer(0);
// change the sequence and change the state.
A_seq = SWAP(A_seq);
A_waiting_ack = 0;
}
/* This is called when A's timer goes off */
void A_timerinterrupt()
{
/* if A is waiitng for ACK from B, resend the packet*/
if (A_waiting_ack){
printf("\tA_timerinterrupt: Resending last packet after timeout: [%s].\n", A_last_packet.payload);
tolayer3(0, A_last_packet);
starttimer(0, A_B_RTT);
}
}
/* 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_seq = 0;
A_waiting_ack = 0;
}
/* 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*/
void B_input(packet)
struct pkt packet;
{
// If the checksum of the packet is not matching, ignore the packet and send NAK
if(packet.checksum != calculate_checksum(&packet)){
printf("\tB_input: Corrupted packet received. Droped and sending NAK.\n");
struct pkt nak_packet;
nak_packet.acknum = SWAP(B_seq);
nak_packet.checksum = calculate_checksum(&nak_packet);
tolayer3(1, nak_packet);
return
/* 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];
};
/********* STUDENTS WRITE THE NEXT SEVEN ROUTINES *********/
void starttimer(int AorB, float increment);
void stoptimer(int AorB);
void tolayer3(int AorB, struct pkt packet);
void tolayer5(int AorB, char datasent[20]);
#define SWAP(x) (x == 0 ? 1 : 0)
#define A_B_RTT 15
int A_seq;
int A_waiting_ack;
struct pkt A_last_packet;
int B_seq;
int B_waiting_ack;
struct pkt B_last_packet;
// The checksum of a packet is calculated
//Take all the bits in the packet and do the summation
int calculate_checksum(struct pkt *packet){
int cs = 0;
cs += packet->seqnum;
cs += packet->acknum;
for (int i = 0; i < 20; ++i)
cs += packet->payload[i];
return cs;
}
/* called from layer 5, passed the data to be sent to other side */
void A_output(message)
struct msg message;
{
if (A_waiting_ack){
/* If A is waiting for ACK from B, ignore new packet from layer 5 */
printf("\tA_output: Waiting for ACK from B. Ignore new message: [%s]\n", message.data);
return;
}else{
/* A is waiting for upper layer, send new msg comming from layer 5 to B */
printf("\tA_output: Sending new message to B: [%s]\n", message.data);
/* Create new packet with the msg and send it to layer 3 below*/
struct pkt packet;
packet.seqnum = A_seq;
memmove(packet.payload, message.data, 20);
packet.checksum = calculate_checksum(&packet);
A_last_packet = packet;
A_waiting_ack = 1;
tolayer3(0, packet);
starttimer(0, A_B_RTT);
}
}
void B_output(message)
struct msg message;
{
}
/* called from layer 3, when a packet arrives for layer 4 */
void A_input(packet)
struct pkt packet;
{
/* if the checksum of the packet is not matching, ignore the packet.[ACK]*/
if (packet.checksum != calculate_checksum(&packet)){
printf("\tA_input: Corrupted packet received and droped.\n");
return;
}
/* if the sequence of the received ACK is not the expected sequence, drop it*/
if (packet.acknum != A_seq){
printf("\tA_input: Unexpected packet received and droped.\n");
return;
}
/* valid ACK received for last packet */
printf("\tA_input: ACK received for Last packet.\n");
stoptimer(0);
// change the sequence and change the state.
A_seq = SWAP(A_seq);
A_waiting_ack = 0;
}
/* This is called when A's timer goes off */
void A_timerinterrupt()
{
/* if A is waiitng for ACK from B, resend the packet*/
if (A_waiting_ack){
printf("\tA_timerinterrupt: Resending last packet after timeout: [%s].\n", A_last_packet.payload);
tolayer3(0, A_last_packet);
starttimer(0, A_B_RTT);
}
}
/* 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_seq = 0;
A_waiting_ack = 0;
}
/* 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*/
void B_input(packet)
struct pkt packet;
{
// If the checksum of the packet is not matching, ignore the packet and send NAK
if(packet.checksum != calculate_checksum(&packet)){
printf("\tB_input: Corrupted packet received. Droped and sending NAK.\n");
struct pkt nak_packet;
nak_packet.acknum = SWAP(B_seq);
nak_packet.checksum = calculate_checksum(&nak_packet);
tolayer3(1, nak_packet);
return
This is only a preview of the solution.
Please use the purchase button to see the entire solution.
Please use the purchase button to see the entire solution.
By purchasing this solution you'll be able to access the following files:
Solution.zip
Purchase Solution
$50.00
View Available
Computer Science Tutors 529 tutors matched
Ionut
(ionut)
Hi! MSc Applied Informatics & Computer Science Engineer. Practical experience in many CS & IT branches.Research work & homework
5/5 (5,654+ sessions)
2 hours avg response
Leo
(Leo)
Hi!
I have been a professor in New York and taught in a math department and in an applied math department.
4.9/5 (5,652+ sessions)
2 hours avg response
Pranay
(math1983)
Ph.D. in mathematics and working as an Assistant Professor in University. I can provide help in mathematics, statistics and allied areas.
4.6/5 (5,512+ sessions)
1 hour avg response