Internet Protocol Stack

Question 1

What is the internet

Answer 1

A global network connecting millions of computers, allowing them to communicate and share resources

Question 2

What is the world wide web

Answer 2

A system of interlinked hypertext documents which can be accessed via the internet.

Question 3

What is Address Resolution Protocol

Answer 3

Operating at the link layer, ARP resolves IP addresses to MAC addresses

Question 4

What is Transmission Control Protocol

Answer 4

Operating at the transport Layer, TCP provides reliable, ordered, and error free delivery of data between applications running on internet-connected hosts.

Question 5

What is the purpose of layering in network protocols?

Answer 5

Layering helps in dealing with complex systems by providing an explicit structure that allows for the identification and relationship of various components.

Question 6

What are the layers in the Internet protocol stack?

Answer 6

Application layer
Transport layer
Network layer
Link layer
Physical layer

Question 7

What are some examples of protocols at the application layer?

Answer 7

FTP (File Transfer Protocol)
SMTP (Simple Mail Transfer Protocol)
HTTP (Hypertext Transfer Protocol)

Question 8

What are the two main architectures for network applications?

Answer 8

Client-server architecture
Peer-to-peer (P2P) architecture

Question 9

Describe the client-server architecture.

Answer 9

In the client-server architecture, there is an always-on server with a permanent IP address, communicating with clients which may be periodically connected. Clients do not communicate directly with each other but interact with the server.

Question 10

What are the characteristics of the P2P architecture?

Answer 10

In the P2P architecture, there is no always-on server. Instead, arbitrary end systems communicate directly with each other. Peers request services from other peers and provide services in return, leading to self-scalability.

Question 11

What are some examples of application-layer protocols and their underlying transport protocols?

Answer 11

SMTP (TCP)
Telnet (TCP)
HTTP (TCP)
FTP (TCP)
RTP (TCP or UDP)
SIP, proprietary protocols like Skype (TCP or UDP)

Question 12

What are the services provided by TCP and UDP?

Answer 12

TCP (Transmission Control Protocol) provides reliable transport, flow control, and congestion control. It’s connection-oriented.
UDP (User Datagram Protocol) provides unreliable data transfer without the mentioned features of TCP. It’s connectionless.

Question 13

What is DNS and its purpose?

Answer 13

DNS stands for Domain Name System, a distributed database implemented in a hierarchy of name servers. Its purpose is to resolve human-readable domain names to IP addresses and vice versa.

Question 14

Why is DNS distributed rather than centralized?

Answer 14

Distributing DNS prevents a single point of failure, reduces traffic volume, and eliminates the need for a distant centralized database, making it more scalable and easier to maintain.

Question 15

What are TLD servers and authoritative DNS servers?

Answer 15

TLD (Top-Level Domain) servers are responsible for managing top-level domains like .com, .org, etc. Authoritative DNS servers are maintained by organizations or service providers and provide authoritative hostname to IP mappings for the organization’s named hosts.

Question 16

What is the role of a local DNS server?

Answer 16

A local DNS server, also known as a default name server, serves clients within an ISP, company, or university. It maintains a cache of recent name-to-address translation pairs and forwards queries into the DNS hierarchy.

Question 17

Describe the process of DNS name resolution.

Answer 17

DNS name resolution involves a client querying a series of DNS servers starting from the root server to resolve a domain name to an IP address, typically through iterative or recursive queries.

Question 18

What are some common HTTP methods used in HTTP request messages?

Answer 18

Common HTTP methods include GET (retrieve a resource), POST (submit data to be processed), and HEAD (retrieve headers only).

Question 19

What are HTTP response status codes and their significance?

Answer 19

HTTP response status codes indicate the outcome of a request. For example, “200 OK” signifies success, “301 Moved Permanently” indicates a resource has moved, and “404 Not Found” signifies the requested resource was not found.

Question 20

What is the purpose of cookies in web browsing?

Answer 20

Cookies are used to maintain user-state information, such as session data, preferences, and authentication tokens, across multiple HTTP requests and responses.

Question 21

How do web caches (proxy servers) work?

Answer 21

eb caches store copies of web content to serve to clients, reducing latency and bandwidth usage by satisfying requests without involving the origin server. If the cache doesn’t have the requested content, it fetches it from the origin server and caches it for future requests.

Question 22

What are some potential uses of cookies, and what concerns are associated with them?

Answer 22

Cookies can be used for authorization, shopping carts, recommendations, and maintaining user session state. However, they raise privacy concerns as they allow sites to track user behavior and may potentially be misused.

Question 23

What are the three major components of email systems?

Answer 23

The three major components of email systems are user agents, mail servers, and the Simple Mail Transfer Protocol (SMTP).

Question 24

What is a User Agent in the context of email?

Answer 24

A User Agent (UA) is also known as a “mail reader” and is responsible for composing, editing, and reading email messages. Examples include Outlook, Thunderbird, and iPhone mail clients.

Question 25

Describe the role of SMTP in email communication

Answer 25

SMTP (Simple Mail Transfer Protocol) is used to reliably transfer email messages from a client to a server. It operates over TCP, typically on port 25, and facilitates the transfer of messages between sending and receiving mail server

Question 26

How do mail servers handle incoming and outgoing email messages?

Answer 26

Mail servers maintain a mailbox for incoming messages and a queue for outgoing messages. They use SMTP to transfer messages between servers, and the messages are stored until accessed by the user agent.

Question 27

Explain the process of SMTP communication between a client and a server.

Answer 27

SMTP communication involves three phases: handshaking, transfer of messages, and closure. It uses ASCII text commands and responses exchanged between the client and server over a TCP connection.

Question 28

What are POP3 and IMAP, and how do they differ?

Answer 28

POP3 (Post Office Protocol) and IMAP (Internet Mail Access Protocol) are mail access protocols used by clients to retrieve emails from a server. POP3 typically downloads messages to the client, while IMAP allows messages to be manipulated on the server.

Question 29

What is the purpose of FTP (File Transfer Protocol)?

Answer 29

FTP is used for transferring files between a client and a server over a network. It allows users to upload and download files to and from a remote host.

Question 30

How does FTP establish data connections for file transfer?

Answer 30

FTP uses separate control and data connections. The control connection is established on port 21, and the server opens a data connection on port 20 for transferring files directly to the client.

Question 31

What are some common FTP commands and their meanings?

Answer 31

Common FTP commands include USER (specify username), PASS (specify password), LIST (retrieve a list of files), RETR (retrieve a file), and STOR (store a file onto the server).

Question 32

What is the role of the transport layer in networking?

Answer 32

The transport layer links the application layer with the network layer, extending the network layer's delivery service between two hosts to an application-layer delivery service between two processes via UDP/TCP.

Question 33

What are the two fundamental issues in networking?

Answer 33

how to communicate reliably over a medium that may lose or corrupt data, how to control transmission rates of transport-layer entities to avoid or recover from congestion.

Question 34

What are transport services and protocols responsible for?

Answer 34

Transport services and protocols provide logical communication between application processes running on different hosts. They are implemented in end systems, breaking app-layer messages into segments at the sender and reassembling them at the receiver.

Question 35

Name two Internet transport-layer protocols and describe their characteristics.

Answer 35

UDP (User Datagram Protocol), which provides unreliable and unordered delivery TCP (Transmission Control Protocol), which offers reliable and ordered delivery, as well as congestion control.

Question 36

What is multiplexing and demultiplexing in the context of transport-layer protocols?

Answer 36

Multiplexing involves handling data from multiple sockets at the sender and adding transport headers for demultiplexing at the receiver, ensuring that received segments are delivered to the correct socket.

Question 37

What is the purpose of UDP (User Datagram Protocol)?

Answer 37

UDP is a connectionless transport protocol that offers unreliable and unordered delivery. It is commonly used for streaming multimedia apps, DNS, and other applications where loss tolerance is acceptable.

Question 38

Describe the UDP segment structure.

Answer 38

The UDP segment structure includes source and destination port numbers, a length field indicating the length of the segment, a checksum for error detection, and application data payload.

Question 39

What are the characteristics of TCP (Transmission Control Protocol)?

Answer 39

TCP is a connection-oriented, reliable, and ordered transport protocol. It supports pipelining, full bi-directional data flow, flow control, and congestion control to ensure efficient data transmission.

Question 40

How does TCP manage retransmission in case of lost segments?

Answer 40

TCP uses timeouts and acknowledgments to manage retransmission. If a timeout occurs or an acknowledgment for a segment is not received, the sender retransmits the segment and restarts the timer.

Question 41

Explain the TCP 3-way handshake for connection establishment.

Answer 41

The TCP 3-way handshake involves SYN, SYN-ACK, and ACK segments exchanged between the client and server to establish a connection. It ensures that both parties agree to establish a connection and exchange initial sequence numbers.

Question 42

What are two key functions of the network layer?

Answer 42

The two key functions of the network layer are routing, which determines the route taken by packets from source to destination, and forwarding, which involves moving packets from the input link to the appropriate output link.

Question 43

What are datagram networks, and how do they forward packets?

Answer 43

Datagram networks forward packets using the destination host address. Each packet is forwarded based on its destination address, allowing for independent routing of packets without establishing a connection.

Question 44

What are the main components of the Internet network layer, and what are their functions?

Answer 44

The main components of the Internet network layer are the transport layer (TCP, UDP), the IP protocol (Internet Protocol), which handles addressing, datagram format, and packet handling conventions, routing protocols like RIP, OSPF, and BGP.

Question 45

Describe the IPv4 datagram format.

Answer 45

The IPv4 datagram format includes fields such as version number, header length, total datagram length, time to live, type of service, source and destination IP addresses, options, data payload, and header checksum.

Question 46

What is IP addressing, and how are IP addresses structured?

Answer 46

IP addressing involves assigning 32-bit identifiers to each interface of a host or router. IP addresses are structured into network and host parts, with subnetting used to group devices with the same subnet part of the IP address.

Question 47

What are forwarding tables, and how are they used in routing?

Answer 47

Forwarding tables are used by routers and hosts to determine how to process outgoing packets. These tables contain destination addresses and corresponding output interfaces, helping routers decide where to forward incoming packets.

Question 48

How does forwarding table lookup work in routing?

Answer 48

Forwarding table lookup involves using the destination address of an IP datagram as a key to search the routing table. The result of the lookup provides the IP address of the next hop or the name of a network interface.

Question 49

Explain the process of getting a datagram from source to destination.

Answer 49

The process involves forwarding the datagram based on the destination address. At each router, the forwarding table is consulted to determine the next hop. The datagram travels unchanged from source to destination, reaching its destination through multiple routers if necessary.

Question 50

What are some motivations for IPv6, and how does it differ from IPv4?

Answer 50

IPv6 was motivated by the need for a larger address space and improved header format for faster processing. IPv6 has a 128-bit address space, a simplified header format, and removes the checksum field to reduce processing time.

Question 51

What is the purpose of DHCP in connecting a device to a network?

Answer 51

DHCP (Dynamic Host Configuration Protocol) is used to obtain the device's IP address, the address of the first-hop router, and the address of the DNS server.

Question 52

How does DHCP work in obtaining network configuration information?

Answer 52

The DHCP request, encapsulated in UDP, IP, and Ethernet frames, is broadcasted on the LAN. The DHCP server formulates a DHCP ACK containing the client's IP address, the first-hop router's IP address, and the DNS server's information.

Question 53

What is ARP, and why is it used before sending a DNS query?

Answer 53

ARP (Address Resolution Protocol) is used to obtain the MAC (physical) address of the router interface before sending a DNS query, as the Ethernet frame requires the MAC address for transmission

Question 54

What role does DNS play in the web request process?

Answer 54

DNS (Domain Name System) resolves domain names to IP addresses. It translates human-readable domain names like "www.google.com" into IP addresses like "64.233.169.105" to facilitate communication over the Internet.

Question 55

How is TCP involved in establishing a connection between the client and the web server?

Answer 55

TCP (Transmission Control Protocol) is used to establish a connection between the client and the web server. This involves a three-way handshake where the client sends a SYN segment, the server responds with a SYN-ACK, and the client acknowledges the SYN-ACK, establishing the connection.

Question 56

What is the purpose of the HTTP protocol in the web request process?

Answer 56

HTTP (Hypertext Transfer Protocol) is responsible for fetching web pages and other resources from web servers. It facilitates the request and response process between the client's browser and the web server.

Question 57

How does packet switching differ from circuit switching?

Answer 57

In packet switching, data streams are divided into packets, and users share network resources. Each packet uses the full link bandwidth, and resources are used as needed, allowing for more efficient use of network resources compared to circuit switching.

Question 58

What are some examples of network applications, and how do they function?

Answer 58

Network applications include email, web browsing, file sharing, video streaming, and social networking. These applications facilitate communication and data exchange between users over the Internet, often using protocols like SMTP, HTTP, and BitTorrent.