Layers

Question 1

What is a Network?

Answer 1

group of computers connected together so they can communicate with each other

Question 2

What is networks of networks?

Answer 2

group of networks connected together so they can communicate with each other

Question 3

What is a private network?

Answer 3

Networks restricted for by one group e.g UoN

Question 4

What is a public network

Answer 4

owned by a service provider and offer service to anyone who pays for access

Question 5

What is circuit switching?

Answer 5

circuit formed between 2 machines to allow communication

Question 6

What is packet switching?

Answer 6

network communication sent in small packets
sent interleaved with other network packets down a single set of wires

Question 7

Which one is better for network utilisation?

Answer 7

Packet switching

Question 8

What does a packet contain?

Answer 8

destination address
source address
packet header

Question 9

What is an OSI network layer model?

Answer 9

Conceptual model

Question 10

How many does OSI layers does it have?

Answer 10

7

Question 11

What are the 7 OSI layers?

Answer 11

Physical
Data link
Network
Transport
Session
Presentation
Application
(1-7, 1 on the bottom)

Question 12

How does OSI work?

Answer 12

Each layer abstracts and builds on the layer below it

Question 13

what do you mean by abstract?

Answer 13

placing packets of one layer inside a packet of the layer which is then placed inside the packet of the layer below and so on

Question 14

How many layers in TCP/IP layer?

Answer 14

5

Question 15

which layer is the internet built on?

Answer 15

TCP/IP

Question 16

can TCP/IP fit into the OSI model?

Answer 16

sort of

Question 17

What is TCP/IP used for?

Answer 17

to communicate between machines

Question 18

Describe the physical layer

Answer 18

This is layer 1
might not be wire
describes how bits get converted into electrical signals and sent
can be a shared medium or point-to-point
e.g ethernet, WIFI, cellullar

Question 19

describe the data link layer

Answer 19

how the data is formatted on the wire into frames
destination address
size of packet
e.g ethernet/WIFI

Question 20

describe the network layer

Answer 20

responsible for enabling forwarding of packets between networks
connectionless service
e.g IPv4, IPv6

Question 21

what is connectionless service?

Answer 21

communication in terms of individual packets
they can just be sent to the destination

Question 22

What is connection-oriented service?

Answer 22

Computers agree to form a connection
once established can communicate down the connection by sending data down the connection

Question 23

Describe the transport layer

Answer 23

this is layer 4
end-to-end communication
ensures reliability,flow control and multiplexing
e.g TCP, UDP

Question 24

Describe the session layer

Answer 24

this is layer 5
managing a session between end-user application processes
not really used in TCP/IP
e.g SPVD, SOCKS, RPC

Question 25

desribe the presentation layer

Answer 25

this is layer 6
manages how data is presented to application
e.g HTML, CSS, GIF, JPG, MP3

Question 26

Describe the application layer

Answer 26

this is layer 7
in OSI its the user interface
in TCP/IP the protocols used between applications
e.g HTTP, POP3, IMAP

Question 27

How do layers work?

Answer 27

they will provide a service capable of transmitting data

Question 28

Which service do layers use to send data

Answer 28

the service above

Question 29

what is presented to the layer?

Answer 29

ancilary information (destination address, source address)

Question 30

What kind of connection do layers use?

Answer 30

connectionless, connection-oriented service

Question 31

What else must the layer be able to do?

Answer 31

Receive data from the equivalent layer or another peer

Question 32

How does the layer know if data has arrived?

Answer 32

the layer below will inform it

Question 33

How many phases do Connection-Oriented Service have?

Answer 33

3

Question 34

what are the 3 phases Connection-Oriented Service have?

Answer 34

connection setup
data transfer
connection release

Question 35

what are the 2 functions required for each phase in Connection-Oriented Service?

Answer 35

one in the layer to initiate the function
one in the layer below to inform it that a peer has initiated the function

Question 36

what does IP layer need addresses for?

Answer 36

to identify both a specific machine and also the network it is on

Question 37

What does layer 2 need addressing for?

Answer 37

to ensure machines on the same network dont have the same address