Key Concepts of Internet Protocols and TCP

Five layers of the Internet Protocol Stack

Application, Transport, Network, Link, Physical

Protocol in networking

A set of rules that define how data is transmitted and received between networked devices.

Difference between network edge and network core

Network edge includes hosts (clients and servers), while the network core consists of interconnected routers that forward packets.

Four types of network delay

Processing delay, queuing delay, transmission delay, propagation delay.

Difference between circuit switching and packet switching

Circuit switching reserves a dedicated path for communication, whereas packet switching breaks data into packets and routes them independently.

Role of the Application Layer in the Internet protocol stack

It provides network services directly to applications, such as HTTP, DNS, and SMTP.

Difference between Client-Server and Peer-to-Peer (P2P) architectures

Client-server has centralized servers serving multiple clients, while P2P allows direct communication between peers without a central server.

How the Domain Name System (DNS) works

DNS translates domain names (e.g., google.com) into IP addresses using a hierarchical lookup process.

Key characteristics of HTTP

Stateless, request-response protocol using TCP, supports persistent and non-persistent connections.

Difference between non-persistent and persistent HTTP

Non-persistent HTTP opens a new TCP connection for each object request, while persistent HTTP reuses the same connection for multiple requests.

Two main transport layer protocols

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).

Difference between TCP and UDP

TCP is reliable and connection-oriented, while UDP is fast and connectionless without reliability mechanisms.

Multiplexing and demultiplexing in the transport layer

Multiplexing allows multiple applications to share the same network connection, while demultiplexing directs incoming data to the correct application.

Purpose of the three-way handshake in TCP

To establish a reliable connection by synchronizing sequence numbers between sender and receiver.

Three steps of the TCP three-way handshake

1. SYN (client initiates connection) 2. SYN-ACK (server acknowledges) 3. ACK (client confirms connection).

Flow control in TCP

A mechanism to prevent a sender from overwhelming a receiver by managing the amount of data sent before acknowledgment.

Congestion control in TCP

A technique to prevent excessive data from overloading the network, using mechanisms like slow start and congestion avoidance.

How UDP handles lost or out-of-order packets

UDP does not handle lost or out-of-order packets; applications must implement their own reliability mechanisms if needed.

TCP timeout and how it is determined

A TCP timeout is the duration TCP waits for an acknowledgment before retransmitting a segment. It is estimated using the RTT (Round Trip Time).

Purpose of sequence numbers and acknowledgment numbers in TCP

Sequence numbers keep track of the order of bytes sent, and acknowledgment numbers confirm receipt of data and indicate the next expected byte.

How TCP uses cumulative acknowledgments

TCP acknowledges the highest contiguous sequence number received, reducing the number of ACKs needed for reliable communication.

Difference between Stop-and-Wait and Pipelined protocols

Stop-and-Wait sends one packet at a time, waiting for an ACK before sending the next, while pipelining allows multiple packets to be sent before receiving ACKs.

Advantage of Go-Back-N over Stop-and-Wait

Go-Back-N improves efficiency by allowing multiple packets to be in transit before requiring acknowledgments, whereas Stop-and-Wait only sends one at a time.

Difference between flow control and congestion control

Flow control prevents the sender from overwhelming the receiver, while congestion control prevents excessive traffic from overwhelming the network.

Why TCP uses exponential backoff for retransmissions

To reduce congestion by doubling the retransmission timeout when a segment is lost, avoiding excessive retransmissions.

TCP's Fast Retransmit mechanism

When three duplicate ACKs are received, TCP assumes a packet is lost and retransmits it immediately without waiting for a timeout.

Why TCP uses a congestion window (cwnd)

To dynamically adjust the number of unacknowledged packets a sender can transmit, preventing congestion collapse.

Difference between selective repeat and Go-Back-N

Selective repeat retransmits only lost packets, whereas Go-Back-N retransmits all packets after a lost one.

What happens during TCP connection termination

Both sender and receiver exchange FIN (finish) and ACK messages to gracefully close the connection.