COMP3234B Computer and Communication Networks
代做web | 代做Network | network | assignment作业 – 本题是一个利用network进行练习的代做, 对network的流程进行训练解析, 涵盖了web/Network/network等方面, 该题目是值得借鉴的assignment代写的题目
ELEC3443B Computer Networks
assignment Two Problem-Set
Total 6 points
Due date: 17:00 March 1, 2023
Answer all questions. Hand-in the assignment via the Moodle System.
Question 1 (20%) (This question is related to to ILO1 be able to explain the terminologies of computer networks; be able to describe the services and functions provided by each layer.)
Consider the data transfer between a web server and Web client using TCP. Suppose the Web server needs to send a video file of size 160 MiB ( 160 220 bytes) to the client. The HTTP layer adds a HTTP header of size 256 bytes to the video object before passing it to the TCP layer. The TCP layer is going to segment the application data into multiple TCP segments and each segment is being carried by an IP datagram of maximum size 1440 bytes (including header and data payload). Assume TCP adds a header of size 44 bytes to each segment and IP has a header of size 28 bytes in each datagram. Further down the protocol stack, the IP layer passes the datagram (of maximum size 1440 bytes) to the Link layer, which adds 34 bytes as the header+trailer to form the Link layer frame. Calculate a) (10%) the number of frames being generated for this traffic; b) (10%) the amount of overhead bytes incurred in this communication for delivering the video file and find the fraction of bandwidth wasted in carrying this data traffic. Assume the communication did not encounter any packet losses.
Question 2 (30%) (This question is related to ILO2 be able to describe the working principles behind key network technologies.) a) ( 12 %) Consider a 1 Mb/s circuit-switched path between two stations A & B and the path consists of five switching nodes in between. It needs 1.2 seconds to set up the circuit (i.e., completion of the call setup and accept) before transmitting any data or voice signals. Further assume that A and B is of 3 km apart and the signal propagation speed is 2 108 m/s. Suppose we are using this path to transmit a 4 MiB file ( 4 220 ) from A to B. Assume the circuit does not exist yet, how long it will take to deliver this file to B using this channel? Give your answer in full precision. b) (18%) If the above circuit-switched path is replaced by a packet-switched system with five packet switches utilizing 1.5 Mbps links. How long does it take to transfer the same amount of data (4 MiB)? Assuming that there is no queuing delay at any of the switches, but each switch needs 10 s to process a packet. Further assume that each packet has a header of size 40 bytes and can carry at most 2048 bytes of data payload. Give your answer in full precision.
Question 3 (50%) (This question is related to ILO2a be able to comprehend the challenges and explain the principles in providing reliable communication in an unreliable medium, and ILO3 be able to calculate packet delay, throughput, and channel efficiency according to different network protocols.) a) ( 20 %) Your team is implementing the RDT3.0 reliable layer for a File Transfer application. To help the team to understand the RDT3.0 logic for the sender and the receiver, your team leader creates the following table that lists possible events experienced by a peer. Please complete the table. For the Action column, provide descriptive information to describe what the peer would do in response to the event at that state; the team will use the information to implement the program logic. For the Next State column, give the state of the peer after the event. We have completed the first row as an example for your reference.
Peer Current State Event Action Next State
Sender seq# = 0 Upper layer calls
rdt_send() to pass a
message to rdt layer.
Build a packet with seq# 0
that contains the upper
layer message, compute
the Internet checksum of
the whole packet, and add
the checksum to the
packet.
Call udt_send() to send the
packet and then start the
retransmission timer.
Buffer this packet for
retransmission.
seq# = 0
wait for ACK
Sender seq# = 0 Lower layer passes an
ACK with seq# 0 to rdt
layer.
Sender seq# = 0 Lower layer passes an
ACK with seq# 1 to rdt
layer.
Sender seq# = 0
wait for ACK
Lower layer passes an
ACK with seq# 1 to rdt
layer.
Sender seq# = 0
wait for ACK
Timeout
Sender seq# = 0
wait for ACK
Lower layer passes a
corrupted ACK with
seq# 0 to rdt layer.
Sender seq# = 0
wait for ACK
Lower layer passes an
ACK with seq# 0 to rdt
layer.
Receiver Expectseq# = 0 Lower layer passes a
corrupted message
with seq# 0 to rdt
layer.
Receiver Expectseq# = 0 Lower layer passes a
corrupted message
with seq# 1 to rdt
layer.
Receiver Expectseq# = 0 Lower layer passes a
message with seq# 0 to
rdt layer.
Updated
Receiver Expectseq# = 0 Lower layer passes a
message with seq# 1 to
rdt layer.
b) Consider the above RDT3.0 protocol is running on a link with 1 Mb/s transmission rate and the propagation delay between two peers is 1 ms. In your design, you add a 10-byte header to the data packet and the packet can carry at most 1500 bytes of payload. The ACK packet is of size 10 bytes as it contains header information only. i. (10%) Given the above operation parameters, calculate the best channel utilization rate for this RDT3.0 protocol on this network. Channel utilization is defined as the fraction of time the channel is busy transmitting bits in the channel. Include the acknowledgment packet in the analysis. ii. (10%) Consider transferring a 3 106 bytes file from the sender to the receiver using the above protocol. Assume the transmissions are error-free, find the best application file transfer throughput. iii. (10%) Assume your RDT3.0 protocol adopts a fixed retransmission timeout duration of 3 ms and the network has an error rate of 1%, i.e., one packet loss/corruption out of 100 transmitted packets. Estimate how long it would take to transfer the same 3 106 bytes file and calculate the result application throughput. Please note that from part a) above, the retransmission timer is started right after the RDT layer sent the data packet.