Week 7

Question 1

What is the Transport Layer and how is it different from a Network Layer?

Answer 1

Transport layer: process to process

Network layer: host to host

Transport layer relies on the network layer service, and it manages movements from app layer to network, and vice versa.

Question 2

What services does the TCP provide in a transport layer?

Answer 2

• reliable, in-order
• congestion control
• flow control
• connection setup

Question 3

What services does the UDP provide in a transport layer?

Answer 3

• error checking

Question 4

What services are NOT provided by the TCP and UDP?

Answer 4

Throughput and delay and bandwidth guarantees

Question 5

What is demultiplexing

Answer 5

[RECEIVER SIDE] the job of delivering the data in a receiving transport-layer segment to the correct socket (going into the application layer) by analyzing the header info

Question 6

What is multiplexing

Answer 6

[SENDER SIDE] collecting data from sockets (from the app layer) and encapsulating it with header information to be analyzed through demultiplexing

Question 7

What are the restricted port numbers

Answer 7

0 to 1023

Question 8

How are UDP sockets identified for multiplexing/demuxing

Answer 8

2 tuples: destination address & destination port number

Question 9

How are TCP sockets identified for multiplexing/demuxing

Answer 9

4 tuples: destination address, destination port number, source address, source port number

Question 10

Why does UDP exist for Transport layer? (Pros)

Answer 10

1. saves time by not setting up connection
2. simple to implement
3. small header size
4. no congestion control. can function even congested

Question 11

What are some uses for UDP?

Answer 11

multimedia apps (loss tolerant)

DNS

HTTP/3

Question 12

What type of connection is checksum used for?

Answer 12

UDP

Question 13

How is checksum calculated?

Answer 13

1. add bits
2. reverse the bits