Mod 14 Transport Layer Protocols: TCP and UDP Overview

Transport Layer

Facilitates logical communication between different applications.

Transport Layer Responsibilities

Tracks conversations, segments data, and manages headers.

Transport Layer Protocols

Defines message transfer methods between hosts.

Transmission Control Protocol (TCP)

Ensures reliable, ordered delivery of data segments.

User Datagram Protocol (UDP)

Connectionless protocol with minimal overhead for datagrams.

Best-Effort Delivery

No acknowledgment of data receipt in UDP.

Session Establishment

TCP negotiates a permanent connection before data transfer.

Reliable Delivery

TCP ensures all segments arrive at the destination.

Same-Order Delivery

TCP reorders segments arriving out of sequence.

Flow Control

TCP manages data transmission rates based on resources.

TCP Header

Contains fields for tracking communication state.

UDP Features

No session establishment; lost segments are not resent.

UDP Header

Simpler than TCP header, requires 8 bytes.

Applications Using UDP

Includes VoIP, live streaming, and DNS requests.

Port Numbers

Manage multiple simultaneous conversations in protocols.

Socket

Combination of IP address and port number.

Well-Known Port Numbers

Standardized port numbers for common services.

Netstat Command

Tool to verify active TCP connections.

TCP Server Processes

Each server application uses a unique port number.

Open Port

An active server application ready to accept connections.

Client-to-Server Communication

Initiating client requests a session with the server.

Server-to-Client Communication

Server acknowledges and requests session back to client.

Data Segmentation

Divides data into manageable packets for transmission.

Multiplexing

Interleaves multiple conversations on the same network.

Retransmission

TCP resends unacknowledged data after timeout.

Data Efficiency

TCP sends data at acceptable rates for receivers.

Request-and-Reply Applications

Use UDP for minimal data and quick retransmission.

Unidirectional Communications

Applications handle reliability without TCP support.

Live Multimedia Applications

Require low delay, tolerate some data loss.

TCP Communication Process

Steps for establishing a reliable TCP session.

Three-Way Handshake

A method used in TCP to establish a connection between a client and a server.

SYN

A control flag used to initiate a TCP connection.

ACK

Acknowledgment flag used in connection establishment and session termination.

FIN

Flag indicating no more data from sender and used in session termination.

URG

Urgent pointer field significant control flag.

PSH

Push function control flag.

RST

Reset the connection when an error or timeout occurs.

Initial Sequence Number (ISN)

The starting point for sequence numbers in a TCP connection.

Selective Acknowledgment (SACK)

A TCP feature that allows the receiver to acknowledge specific segments received.

Sliding Window

A flow control mechanism that allows a sender to send multiple packets before needing an acknowledgment.

Maximum Segment Size (MSS)

The maximum amount of data that the destination device can receive, typically 1,460 bytes when using IPv4.

Maximum Transmission Unit (MTU)

The largest size a packet can be for transmission over a network, commonly 1500 bytes for Ethernet.

Congestion Avoidance

Techniques used by TCP to prevent network congestion and manage packet transmission.

Segments

The units of data that TCP uses to transmit information.

Datagrams

The units of data that UDP uses to transmit information.

Connection-Oriented Protocol

A protocol that establishes a connection before transmitting data, such as TCP.

Connectionless Protocol

A protocol that sends data without establishing a connection, such as UDP.

Stateless Protocol

A protocol that does not maintain session information between requests, like UDP.

Socket Pairs

A combination of IP address and port number used to identify a communication endpoint.

netstat

A command-line tool used to display network connections, routing tables, and interface statistics.