1.0 OSI Model

Question 1

What are the 7 layers of the OSI Model?

Answer 1

Application
Presentation
Session
Transport
Netowork
Data Link
Physical

Question 2

What is the application layer? Provide an example.

Answer 2

Used by human-computer interface software to communicate between applications and access network services.

Eg. SMTP, HTTP, DNS

Question 3

What is the Presentation Layer? Provide an example.

Answer 3

Formats the data to be read by the application.

Eg. JPEG, txt, PNG

Question 4

What is the Session Layer? Provide an example.

Answer 4

Establishes and tears down sockets to create and tear down the communication link.

Eg. SMPP

Question 5

What is CoS?

Answer 5

Class of Service.

Classifies the type of data traffic.

Question 6

What is QoS?

Answer 6

Quality of Service.

Regulates the flow of traffic according to its class.

Question 7

What are the factors to measure QoS?

Answer 7

Packet Loss
Bandwidth
Latency (time it takes a packet to travel to its destination)
Jitter (variablity of latency over time)

Question 8

What is the Transport Layer? Provide an example.

Answer 8

Transmits data on the network using transmission protocols. Includes segmenting data, multiplexing, flow control.

Eg. TCP, UDP.

Question 9

What is reliable delivery of data?

Answer 9

Requires a check after each data packet is sent, to ensure delivery. Uses more bandwidth.

Question 10

What is unreliable delivery of data?

Answer 10

No check after sending data. Uses less bandwidth.

Question 11

What is the Network Layer? Provide an example.

Answer 11

Deciding which physical path the data will take by defining the logical topology of the network.

Relies on IP addressing.

Eg. Router, IPv4, IPv6.

Question 12

What is ARP?

Answer 12

Address Resolution Protocol.

Used in the Network Layer. When a computer is trying to reach an IP address but does not know the associated MAC address, it uses ARP to inquire to all the computers in the network, “what is your MAC address”.

Question 13

What is the Data Link Layer? Provide an example.

Answer 13

Defines the mechanics of physical communication by defining the format of data on the network.

Uses MAC Addresses.

Eg. Switch

Question 14

What is the Physical Layer? Provide an example.

Answer 14

Defines the physical components and interfacing of network devices.

Eg. CAT 5, hub, booster

Question 15

What are the layers of the TCP/IP model?

Answer 15

Application
Transport
Internetwork
Link and Physical

Question 16

What is the TCP/IP model?

Answer 16

Transmit Control Protocol / Internet Protocol

Conceptual model that provides end-to-end data communication.

Covers Transport and Network layers.

Question 17

What is DNS?

Answer 17

Domain Name System

Hierarchical decentralized naming system for internet resources. Domains are mapped out in a directory service such that for each successive domain name, one does not have to search the entire internet, just within that domain.

Question 18

What is ICMP?

Answer 18

Internet Control Message Protocol

Used by network devices to send error messages and operation information (eg. router could not be reached). Typically used by routers.

Question 19

What is UDP?

Answer 19

User Datagram Protocol

Similary to TCP but it is an enreliable transmission.