OSI Model

Question 1

OSI Model Layer 1

Answer 1

Physical Layer
PDU = symbol
function: transmission and reception of raw bit streams over a physical medium

example: full-duplex, RJ45

Question 2

OSI Model Layer 2

Answer 2

Data Link Layer
PDU = frame
function: reliable transmission of data frames between 2 nodes connected by a physical layer

example: ARP, token ring, bit stuffing, CRC, ethernet

Question 3

OSI Model Layer 3

Answer 3

Network Layer
PDU = Packet
function: structuring and managing a multi-node network, including addressing, routing, and traffic control

protocols: IP, ICMP, RIP

Question 4

OSI Model Layer 4

Answer 4

Transport Layer
PDU = segment, datagram
function: reliable transmission of data segments between points on a network, including segmentation, acknowledgement, and multiplexing

example: NetBios Frames
protocols: TCP, UDP

Question 5

OSI Model Layer 5

Answer 5

Session Layer
PDU = data
function: managing communication sessions (i.e. continuous exchange of info in the form of multiple back and forth transmissions between 2 nodes)

protocols: sockets

Question 6

OSI Model Layer 6

Answer 6

Presentation Layer
PDU = data
function: translation of data between a networking service and an application; including character encoding, data compression, and encryption/decryption

protocols: SSL, TLS

Question 7

OSI Model Layer 7

Answer 7

Application Layer
PDU = data
function: high-level APIs, including resource sharing, remote file access

example: HTTP, websocket

Question 8

OSI Model Host Layers

Answer 8

Layers 7 - 4

7 application
6 presentation
5 session
4 transport

Question 9

OSI Model Media Layers

Answer 9

Layers 3 - 1

3 network
2 data link
1 physical