OSI (Open Systems Interconnect)

Question 1

What is OSI?

Answer 1

Open Systems Intercom

Question 2

Different layers of OSI?

Answer 2

Layer 1: Physical Layer
Layer 2: Data link Layer
Layer 3: Network Layer
Layer 4: Transport Layer
Layer 5: Session 
Layer 6: Presentation Layer
Layer 7: Application Layer

Question 3

Physical Layer

Answer 3

Signalling, Cabling, Connectors

Physical problem that will need fixing

Question 4

Data link Layer

Answer 4

DLC (Data link control)
Foundation of the communication
Transfers data between nodes on a network
Sends across the physical layer

Question 5

Network Layer

Answer 5

The “routing” layer
Used as an internet protocol
Provides data routing paths for network communication
Fragments frames to traverse different networks

Question 6

Transport Layer

Answer 6

TCP (Transmission Control Protocol)
UDP (User Datagram Protocol)
Provides Transfer of data between end users
Control’s reliability of a given link

Question 7

Session Layer

Answer 7

Communication management between devices
Half duplex, full duplex
Duplex Communication System: Point-to-point communication system. Compromised of two or more connection devices. Both of which can communicate with one another
Full-Duplex: a system or circuit can transmit and receiving data at the same time
Half-Duplex: Communication can only go in one direction at a time
Controls protocols, tunnelling protocols

Question 8

Presentation Layer

Answer 8

Character encoding
Application encryption
Often combined with application layer
Translator between application and the network
Addresses syntax representation of user information
Data compression, decompression, encryption, decryption

Question 9

Application Layer

Answer 9

The layer we usually see
HTTP, FTP, DNS. POP3
Abstraction layer
Specifies shared communications, protocols and interface methods used by hosts in a communication of networks

Question 10

TCP

Answer 10

Slower than UDP
Can usually retransmit lost packets
Extensive error checking 
Guarantee of delivery
Transmission to end point means it must establish a connection first

Question 11

UDP

Answer 11

Faster than TCP 
Usually is connectionless 
No retransmissions 
Reliability handles by the application layer 
Only cares about fast transmissions