IP-based Communications

Question 1

Explain the encapsulation process on the sending host.

Answer 1

1. Application layer encodes data.
2. Transport layer breaks data into segments and adds header.
3. Internet layer converts segments into packets with IP addresses.
4. Link layer adds MAC addresses and converts packets into frames.
5. Frames are transmitted as bits.

Question 2

What is the purpose of Link layer headers in IP-based communications?

Answer 2

Link layer headers specify source and destination MAC addresses for each frame.

Question 3

How are IP addresses used in determining network transmission?

Answer 3

IP addresses are used to determine whether hosts reside on the same or different networks.

Question 4

Describe the Address Resolution Protocol (ARP) process for IP-based communications.

Answer 4

1. Sending host checks ARP cache for MAC address.
2. If not found, sends ARP broadcast.
3. Destination host responds with MAC address.
4. Source caches destination MAC address and transmits frames.

Question 5

What happens if the source and destination hosts reside on different networks in IP-based communications?

Answer 5

Packets must be forwarded from router to router until they reach the appropriate destination network and host.

Question 6

Why does the source system use ARP to determine the MAC address of the first hop router in IP-based communications?

Answer 6

To obtain the MAC address of the first hop router if not already cached for forwarding packets.

Question 7

What is the role of the source MAC address in frames?

Answer 7

It is set to the MAC address of the sending system.

Question 8

How does the router identify the destination MAC address in frames?

Answer 8

It uses ARP to discover the MAC address.

Question 9

When a router receives packets, what does it examine?

Answer 9

It examines the packets for their source and destination IP addresses.

Question 10

What does a router do if the destination host is on a directly connected network?

Answer 10

It re-encapsulates the packets with the destination host’s MAC address.

Question 11

How does a router determine the next router to send packets to?

Answer 11

It uses its routing table.

Question 12

What happens if the destination host is not on a directly connected network?

Answer 12

The router re-encapsulates the packets and sends them to the next router.

Question 13

Explain the process of de-encapsulation on the destination host.

Answer 13

Data is moved from the bottom layer to the top layer for processing.