Lesson 1: OSI Model

Question 1

What is a network?

Answer 1

Two or more computer systems ‘link’ed by transmission media to share information

Question 2

Characteristics of a LAN

Answer 2

Local Area Network

Internal / Private network
Network in a singular location.
Can be 2 PC’s in a SOHO or an enterprise network

Question 3

Characteristics of a WAN

Answer 3

Wide Area Network,
External/Public network,
Networks in different geographic locations but with shared links,
“The Internet”

Question 4

What is a node?

Answer 4

A device communicating on the network via one or more interfaces
(Can include endpoints such as computers)
(Can include forwarding nodes such as switches and routers)

Question 5

What is a host?

Answer 5

Host typically refers to a computing device (not a switch or a router)

Question 6

What is transmission media?

Answer 6

Cabled or wireless ‘links’ between nodes

Question 7

What is a protocol?

Answer 7

A set of rules enabling systems to communicate by exchanging data in a structured format

Question 8

What is addressing?

Answer 8

Describes where data should go

Question 9

Explain encapsulation

Answer 9

Describes how data should be packaged for transmission

Header / payload

Question 10

What devices operate at the Physical layer?

Answer 10

Transceiver, Hub, Repeater, Modem

Question 11

Layer 1 of the OSI model

Answer 11

Physical (Bit Stream)
Nodes, stations, and hosts (computing device)
Transmission media: cabled or wireless ‘links’ between nodes

Question 12

Layer 2 of the OSI model

Answer 12

Data Link (Frames)
Organizes bits into frames
Destination and source hardware addresses (MAC addresses)
Error detection

Question 13

Layer 3 of the OSI model

Answer 13

Network (Packets),
Moving data around a network of networks,
Logical addressing between networks,
IP addresses,
Routing

Question 14

Layer 4 of the OSI model

Answer 14

Transport (Segment)
Multiplexing and de-multiplexing
TCP/UDP
Responsible for ensuring reliable data delivery

Question 15

Layers 5 and 6 of the OSI model

Answer 15

Session and Presentation (Data)

Divisions between upper layers less important in real-world protocols

Question 16

Layer 7 of the OSI model

Answer 16

Application (Data)
Provides communication protocols and interfaces for software processes running on different hosts
Application programming interfaces (APIs) for software programs

Question 17

What devices operate at the Data Link layer?

Answer 17

Network adaptor or Network Interface Card (NIC),
Basic switch,
Wireless Access point (AP)

Question 18

What devices operate at the Network layer?

Answer 18

Router

Layer-3 switch

Question 19

What devices operate at the Transport layer

Answer 19

Security devices like advanced firewalls and IDSs (Intrusion Detection System)

Question 20

What is multiplexing/de-multiplexing?

Answer 20

Packages data in a stream of segments
Merges segments from different applications over the network link
Port numbers allow receiving host to de-multiplex and reassemble data for the appropriate application handler