Layers Flashcards
What is a Network?
group of computers connected together so they can communicate with each other
What is networks of networks?
group of networks connected together so they can communicate with each other
What is a private network?
Networks restricted for by one group e.g UoN
What is a public network
owned by a service provider and offer service to anyone who pays for access
What is circuit switching?
circuit formed between 2 machines to allow communication
What is packet switching?
network communication sent in small packets
sent interleaved with other network packets down a single set of wires
Which one is better for network utilisation?
Packet switching
What does a packet contain?
destination address
source address
packet header
What is an OSI network layer model?
Conceptual model
How many does OSI layers does it have?
7
What are the 7 OSI layers?
Physical
Data link
Network
Transport
Session
Presentation
Application
(1-7, 1 on the bottom)
How does OSI work?
Each layer abstracts and builds on the layer below it
what do you mean by abstract?
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
How many layers in TCP/IP layer?
5
which layer is the internet built on?
TCP/IP
can TCP/IP fit into the OSI model?
sort of
What is TCP/IP used for?
to communicate between machines
Describe the physical layer
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
describe the data link layer
how the data is formatted on the wire into frames
destination address
size of packet
e.g ethernet/WIFI
describe the network layer
responsible for enabling forwarding of packets between networks
connectionless service
e.g IPv4, IPv6
what is connectionless service?
communication in terms of individual packets
they can just be sent to the destination
What is connection-oriented service?
Computers agree to form a connection
once established can communicate down the connection by sending data down the connection
Describe the transport layer
this is layer 4
end-to-end communication
ensures reliability,flow control and multiplexing
e.g TCP, UDP
Describe the session layer
this is layer 5
managing a session between end-user application processes
not really used in TCP/IP
e.g SPVD, SOCKS, RPC
desribe the presentation layer
this is layer 6
manages how data is presented to application
e.g HTML, CSS, GIF, JPG, MP3
Describe the application layer
this is layer 7
in OSI its the user interface
in TCP/IP the protocols used between applications
e.g HTTP, POP3, IMAP
What is the job of layers?
they will provide a service capable of transmitting data
Which service do layers use to send data
the service above
what is presented to the layer?
ancilary information (destination address, source address)
What kind of connection do layers use?
connectionless, connection-oriented service
What else must the layer be able to do?
Receive data from the equivalent layer or another peer
How does the layer know if data has arrived?
the layer below will inform it
How many phases do Connection-Oriented Service have?
3
what are the 3 phases Connection-Oriented Service have?
connection setup
data transfer
connection release
what are the 2 functions required for each phase in Connection-Oriented Service?
one in the layer to initiate the function
one in the layer below to inform it that a peer has initiated the function
what does IP layer need addresses for?
to identify both a specific machine and also the network it is on
What does layer 2 need addressing for?
to ensure machines on the same network dont have the same address
