Network Models

Question 1

what is a protocol?

Answer 1

A protocol defines the rules that the sender and receiver and all intermediaries need to follow to be able to communicate effectively

Question 2

what is modularity in protocol layering?

Answer 2

Modularity means independent layers. A module (layer) is a black box with inputs and outputs, and as long as the inputs and outputs are the same they can be replaced.

Question 3

what are some advantages of protocol layering?

Answer 3

• separates services from implementation

- intermediate steps do not need all layers

Question 4

what is the first principle of protocol layering?

Answer 4

If we need bidirectional communication, we need to make each layer so that it is able to perform 2 opposite tasks one in each direction.

Question 5

what is the second principle of protocol layering?

Answer 5

The objects under each layer at both sites (sender and receiver) should be identical

Question 6

what is a logical connection?

Answer 6

an imaginary connection between identical objects at the same layer of different sites

Question 7

what does TCP/IP stand for?

Answer 7

Transmission Control Protocol/Internet Protocol

Question 8

what does the physical layer do?

Answer 8

It takes electrical signals from the transmission media and turns them into bits

Question 9

what does the data-link layer do?

Answer 9

When a router choose the best link, the data- link protocol moves the datagram across the link.

Question 10

what does the network layer do?

Answer 10

chooses and routes the packet through possible routes.

Question 11

what does the transport layer do?

Answer 11

provides signals to the application layer adds a transport header and information on ports etc, and the type of program to be used

Question 12

What does the application layer do?

Answer 12

Logical connection between two applications. Sends the message between applications, usually with no header

Question 13

Identify the five components of a data communications system.

Answer 13

Message
Sender
Receiver
Transmission medium
Protocol

Question 14

What are the three criteria necessary for an effective and efficient network?

Answer 14

Performance - throughput and delay
Reliability - frequency of failure, recovery time, robustness in a catastrophe
Security - access, damage, development, recovery

Question 15

What are the advantages of a multipoint connection over a point to point connection?

Answer 15

Advantages of a multipoint over a point-to-point configuration (type of connection) include
ease of installation and low cost.

Question 16

What are the two types of line configuration?

Answer 16

point to point

multi point

Question 17

Categorise the four basic topologies in terms of line configuration

Answer 17

mesh - p2p
star - p2p
bus - multipoint
ring - p2p

Question 18

what is the difference between half duplex and full duplex transmission modes?

Answer 18

half duplex - no transmission and receiving at the same time

full duplex both stations can transmit and receive simultaneously

Question 19

for n devices in a network, what is the number of cable links required for a mesh, ring, bus and star topology?

Answer 19

mesh n(n-1)/2
ring n
bus n+1
star n

Question 20

What is an RFC and what difference between a required RFC and a Recommended RFC?

Answer 20

Before a new Internet standard is adhered to it must be an Internet Draft (ID). Once the ID is endorsed, it becomes a Request for Comment (RFC). Required RFC must be adhered to for minimum conformance. Recommended RFC are recommended for their usefulness, e.g. FTP and TELNET.

Question 21

What is the maximum number of symbols that can be represented by unicode?

Answer 21

2^(32) I think…

Question 22

A color image uses 16 bits to represent a pixel. What is the maximum number of different colors that can be represented?

Answer 22

2^(16)

Question 23

How many input/output ports are required on each device in a mesh topology

Answer 23

n-1

Question 24

Which layers of the TCP/IP protocol suite are involved in a link-layer switch?

Answer 24

The link-layer switch is normally involved in the first two layers of the TCP/ IP protocol
suite:
a. the physical layer,
b. and the data-link layer

Question 25

At what protocol layer is the main protocol IP?

Answer 25

Network layer

Question 26

At what protocol layer is TCP and UDP?

Answer 26

Transport. Transmission Control Protocol and User Datagram Protocol.

Question 27

At what layer protocol is HTTP and SMTP and FTP

Answer 27

application layer. Hypertext Transfer Protocol, Simple Mail Transfer Protocol, File Transfer Protocol