L1 - Application Layer 1

Question 1

What are hosts in the Internet?

Answer 1

• End systems running network applications.
• Examples: Smartphones, PCs, Servers, Wireless Laptops.

Question 2

What types of communication links exist in the Internet?

Answer 2

• Fiber, copper, radio, satellite.
• Transmission determined by bandwidth.

Question 3

What are packet switches?

Answer 3

• Devices like routers and switches that forward data packets across networks.

Question 4

What defines a network protocol?

Answer 4

• Format, order of messages, and actions upon sending and receiving messages.

Question 5

What are Internet standards and who defines them?

Answer 5

• RFC (Request for Comments) documents and the IETF (Internet Engineering Task Force).

Question 6

What is the Internet Service View?

Answer 6

• Infrastructure providing services to apps like Web, VoIP, Email, etc., through an API.

Question 7

Why do we use layers in network architecture?

Answer 7

• Each layer provides services independently while relying on lower layers.

Question 8

Name the five layers of the Internet Protocol Stack.

Answer 8

• Application, Transport, Network, Link, Physical.

Question 9

What are the ISO/OSI additional layers beyond the Internet Stack?

Answer 9

• Presentation (interpret meaning of data)
• Session (synchronization, checkpointing, recovery)

Question 10

What is the Client-Server architecture?

Answer 10

• Server is always on, has a permanent IP.
• Clients connect intermittently and usually do not connect directly to each other.

Question 11

What is the Peer-to-Peer (P2P) architecture?

Answer 11

• No always-on server; peers communicate and share services directly.

Question 12

What is a socket in networking?

Answer 12

• An endpoint for sending or receiving messages at the process level.

Question 13

How is a process uniquely identified in a network?

Answer 13

• By a combination of IP address and port number.

Question 14

What does an app-layer protocol define?

Answer 14

• Message types, syntax, semantics, and transmission rules.

Question 15

What transport needs must a network application consider?

Answer 15

• Data integrity, throughput, timing, and security.

Question 16

What services does TCP provide?

Answer 16

• Reliable data transfer, flow control, congestion control, connection setup.

Question 17

What services does UDP lack compared to TCP?

Answer 17

• No reliability, no flow control, no congestion control, no guaranteed timing.

Question 18

How is TCP secured?

Answer 18

• Using SSL/TLS protocols for encryption, integrity, and endpoint authentication.

Question 19

What networks are connected through ISPs in the diagram?

Answer 19

• Mobile network, Home network, Institutional network.

Question 20

What are global and regional ISPs responsible for?

Answer 20

• Interconnecting smaller networks and ensuring data delivery across regions.

Question 21

What roles do routers play in the network?

Answer 21

• Forwarding packets from source to destination across links.

Question 22

What types of links connect devices in the Internet?

Answer 22

• Wired links (fiber, copper) and Wireless links (radio signals).

Question 23

How do mobile devices connect to the Internet in the diagram?

Answer 23

• Through wireless networks and mobile ISPs.

Question 24

How is network layering compared to airline operations?

Answer 24

• Each service (ticketing, baggage, gates, runways) operates in layers, just like network layers.

Question 25

What does the 'runway' layer correspond to in networking?

Answer 25

* The physical transfer of data, like takeoff/landing of airplanes.

Question 26

What internal-layer actions happen during baggage handling in the analogy?

Answer 26

* Internal processes like loading, unloading, and claiming baggage, similar to data encapsulation.

Question 27

What does encapsulation mean in networking?

Answer 27

* Wrapping data with headers at each protocol layer for transmission.

Question 28

At which layers is data encapsulated in the source device?

Answer 28

* Application, Transport, Network, Link, and Physical layers.

Question 29

What transformation does a message undergo before reaching the physical medium?

Answer 29

* It becomes a frame, including headers for link, network, and transport.

Question 30

Which layers are visible on both the sending and receiving ends in the diagram?

Answer 30

* Application, Transport, Network, Data Link, and Physical layers.

Question 31

How does application-layer communication occur over the Internet?

Answer 31

* Through service layers using encapsulated data.

Question 32

In client-server architecture, where are the arrows directed?

Answer 32

* From clients to servers in centralized fashion.

Question 33

Do clients directly communicate with each other in client-server models?

Answer 33

* No, they only communicate with the server.

Question 34

In P2P architecture, how do communication paths look?

Answer 34

* Multiple arrows between peers and sometimes to servers.

Question 35

What are the advantages of P2P over client-server?

Answer 35

* Scalability, resilience, and resource sharing.

Question 36

What is a socket in the context of two processes communicating?

Answer 36

* It acts like a door through which messages pass from one process to another.

Question 37

Who controls the application layer and the transport layer?

Answer 37

* Application developer controls application layer; OS controls transport layer and below.