Introduction

Question 1

What is the Internet?

Answer 1

A network of networks

Question 2

What is a Packet?

Answer 2

A packet is a small amount of data sent over a network

Question 3

What is a Packet switch?

Answer 3

Forwards packets e.g. routers and switches

Question 4

Whats is a Protocol?

Answer 4

Protocols define the format and the order of messages sent and received among network entities.

Question 5

Name the four types of delays and explain them .

Answer 5

1) Processing Delay: The amount of time taken by a router between receiving the packet and forwarding the packet out.
2) Queueing delay: time waiting at output link for transmission. depends on congestion level of router.
3) Transmission delay: the amount of time taken by a router to push out the packet . Considers L: packet length (bits), R: link bandwidth (bps). =L/R
4) Propagation delay: the amount of time taken by a packet to travel from one of the output links to the other. Consider d: length, s: speed, =d/s

Question 6

What is a traceroute program?

Answer 6

Provides delay measurement from source to router

Question 7

What is a Throughput?

Answer 7

rate at which bits are transferred between sender and receiver. Bits/sec

Question 8

What is a network core?

Answer 8

A mesh of interconnected routers

Question 9

Name two key network core functions

Answer 9

Routing and Forwarding

Question 10

Why is packet switching more widely used compared to circuit switching?

Answer 10

Packet switching can support more users, there is no limit. Circuit switching is no longer in use. It was used in traditional telephones.

Question 11

What is Encapsulation?

Answer 11

Encapsulation is the process of taking data from one protocol and translating it into another protocol, so the data can continue across a network. For example, a TCP/IP packet contained within an ATM frame is a form of encapsulation.

Question 12

How does loss and delay occur?

Answer 12

When packets arrival rate to link temporarily exceeds the output link capacity

Question 13

What is a bottleneck?

Answer 13

A point of congestion that occurs where workloads arrive too quickly for the output link to handle.

Question 14

Difference between LANs and WANs

Answer 14

Local Area Network provides connection to router within a building (WiFi)
Wide Area Network provides the connection to router in a wide area (Cellular 4G)

Question 15

Name 3 types of Physical media

Answer 15

1. Physical link
2. guided media e.g. fiber, copper
3. unguided media e.g. radio(wan, lan, satellite)

Question 16

Explain what packet switching is

Answer 16

This is when hosts break up application layer messages into packets. i.e. the internet works in this way

Question 17

What is the store and forward approach?

Answer 17

The entire packet must arrive at the router before it can be transmitted on to the next link.

Question 18

How do you calculate end-to-end delay?

Answer 18

2L/R (Assuming 0 propagation delay else L/R)

Question 19

What is routing?

Answer 19

The process that determines the source to destination route for packets

Question 20

What is forwarding?

Answer 20

Moves packets from router’s input to appropriate router output

Question 21

What does the network layer do?

Answer 21

Responsible for routing of datagrams from source to destination. Eg IP, routing protocols

Question 22

What does the link layer do?

Answer 22

Provides data transfer between neighbouring network elements. Eg ethernet, WiFi