Computer Comms & Networking

Question 1

220.20.20.0/24
A = 32 B = 60 C = 2 D = 12 E =20 Hosts required

Using ANDing show the below are from which n/w?
220.20.20.70
220.20.20.140
220.20.20.178

Question 2

192.168.1.0/24
A = 28 B = 52 C = 15 D = 5 Hosts required

Using ANDing show the below are from which n/w?
192.168.1.80
192.168.1.120

Question 3

What is Bit Stuffing. Flag Pattern

Question 4

Stop and Wait Flow Control
What the Sending station does:
What the Transmission Station does:
Type of transmission:

Question 5

Sliding Window Flow Control
What the Sending/Transmission do, what they keep track,
Type of transmission

What happens if frames 4,5,6 arrives and the buffer is full? What if it still has space:

Question 6

Stop and Wait x Sliding Window

Question 7

Stop-and-Wait Error Control
If frame contains error
If frame is lost.
If frame is not acknowledged
If ACK is sent but is lost or damaged in transit.

Question 8

Go-Back-N
If no errors
Lost frames or Damaged frames
Lost ACKs

Question 9

Selective Reject
why more efficient?
If the frame is lost or damaged?
why more complex?
Which one is preferred?

Question 10

IP Address
Purpose
Used by
In Routing Table
Destination IP

Answer 10

Purpose: Identifies devices logically on a network; can change depending on the network.
Used by: Routers to determine the best path to send packets
In Routing Table: Routers store IP addresses (network prefixes and next hops)
Destination IP: Identifies the final recipient of a packet, even across networks

Question 11

MAC Address
Purpose
Used by
In Routing Table
Destination MAC

Answer 11

Purpose: Uniquely identifies a device on a local network (LAN)
Used by: Switches, Bridges and hosts to deliver frames within a LAN
In Routing Table: Not stored in IP routing tables; MACs are resolved via ARP (Address Resolution Protocol)
Destination MAC: Used only for local delivery (e.g., delivering to a device on the same subnet)

Question 12

IP Address x MAC address Example

Answer 12

When Host A sends data to Host B:
It uses Host B’s IP address as the destination in the IP header.
To deliver locally, it uses Host B’s MAC address in the Ethernet frame (resolved via ARP if needed).
Routers forward the packet using IP addresses only.
At each hop, the destination MAC address changes (to the next hop), but the IP address stays the same.

Question 13

Universal service provision and associated issues

Answer 13

Universal Service Provision refers to the goal of ensuring all users, regardless of location, socioeconomic status, or network type, can access communication services. In an internetwork, this implies seamless and reliable data communication across different networks and service providers.

Different protocols, hardware, and network topologies must cooperate.
High traffic leads to congestion, packet loss, and reduced throughput.
Need for firewalls, VPNs, encryption, authentication mechanisms.

Question 14

IP Addressing
Classful
Classless

Answer 14

Classful
See image
Class A 0 prefix suffix 16m
Class B 10 prefix suffix 65k
Class C 110 prefix suffix 256

Classless
CIDR
uses of masks /25 etc .