IPv4

Question 1

IP - general characteristics

Answer 1

• part of TCP/IP, used by Internet
• specifies interfaces with higher layer, e.g. TCP
• specifies protocol format and mechanisms

Question 2

IP - services

Answer 2

Primitives:
- send: request transmission of data unit
- deliver: notify user of arrival of data unit

Question 3

IP - parameters

Answer 3

• used to pass data and control info
• parameters: source address, destination address, protocol (e.g. TCP), type of service (specify treatment of data unit during transmission through networks)

Question 4

IP - header fields

Answer 4

1. version, IHL (internet header length), type of service, total length
2. identification, flags, fragment offset
3. time-to-live, protocol, header checksum
4. source address
5. destination address
6. options + padding

visualize it from 6 to 1.

Question 5

IP addresses - classes

Answer 5

Class A: 1.x.x.x - 126.x.x.x
Class B: 128.x.x.x - 191.x.x.x
Class C: 192.x.x.x - 223.x.x.x
Class D: multicast addresses for group users, 224 - 239
Class E: reserved for research and future developments, 240-255

Question 6

ICMP - Internet Control Message Protocol

role

Answer 6

• provides error reporting mechanisms (ICMP messages sent in response to incoming datagrams with problems; datagrams with problems are discarded)
• need for appending to IP (used only for data transfer) of some control protocols
• encapsulate in IP datagram (not a very reliable protocol due to its best-effort delivery)