ECM 1413 The Application Layer

Question 1

What does the application layer represent?

Answer 1

The Application Layer represents the Human Interface to the Network (Covers HTTP, DHCP, DNS, SMTP, FTP, SSH)

Question 2

The 2 network models

Answer 2

• Client-server
• Peer-to-Peer Model

Question 3

Client-server model

Answer 3

• Client requests a service
• Server offers a service
• Centralized Administration

Question 4

Peer-to-Peer Model

Answer 4

• A device to act as both a client and a server within the same communication session
• No need for a centralized server
• Example: BitTorrent

Question 5

The Hypertext Transfer Protocol (HTTP)

Answer 5

• WWW is a massive collection of intrelinked documents and resources
• HTTP facilitates the transfer of these resources (e.g. HTML files)

Question 6

HTTP Request
Format:

Answer 6

Method Path Version
Request Headers provide information about the request context

Question 7

HTTP Response
Format: Version Status-code Status-message

Answer 7

Version Status-code Status-message

Question 8

HTTP Request methods

Answer 8

GET: Retrieves data
POST: Submits data
DELETE: Deletes data

Question 9

HTTP Response status codes and messages

Answer 9

200: OK
301: Moved Permanently
404: Not Found

Question 10

HTTPS

Answer 10

Ensures the identity of the server
Encrypts transmitted data

Question 11

HTTP versions

Answer 11

HTTP/1.1 -> 1997
HTTP/2 -> 2015
HTTP/3 -> 2022

Question 12

HTTP/2

Answer 12

enables efficient use of network resources to reduce latency:
- Header field compression
- Multiplexing - multiple concurrent exchanges on the same connection

Question 13

HTTP/3:

Answer 13

• QUIC instead of TCP
• Built-in Secure Communication

Question 14

Web server software examples

Answer 14

Apache, Nginx

Question 15

Dynamic Host Configuration Protocol

Answer 15

DHCP automates the assignment of IP address, subnet mask, default gateway, and DNS server

Question 16

Telnet and SSH

Answer 16

Remote access protocols
Telnet transfers data as plain text