Transport Layer - Transport Layer

Transport Layer Functions

  • The transport layer is essential for reliable computer networking with several key functions including:
    • Multiplexing and Demultiplexing
    • Establishing long-running connections
    • Ensuring data integrity through error checking and data verification

Key Concepts

Multiplexing and Demultiplexing

  • Multiplexing: Refers to directing traffic from multiple sources to different services on a network.
  • Demultiplexing: The reverse process where incoming traffic, directed to a single node, is delivered to the appropriate receiving service.
  • Mechanism Used: Ports are employed to facilitate multiplexing and demultiplexing.

Ports

  • A port is a 16-bit number used to direct traffic to specific services running on a networked computer.
  • Role of Server and Client:
    • Server: A program that runs on a computer, waiting for requests for data.
    • Client: A program requesting data from the server.

Example of Ports

  • Commonly used ports include:
    • HTTP (Hypertext Transfer Protocol): Listens on port 80 for unencrypted web traffic.
    • Example: Requesting a web page from a server at IP 1011100 would look like 101110080 (socket address format).
    • FTP (File Transfer Protocol): Traditionally uses port 21 for file transfer.
    • If FTP is also hosted on the same server, the socket address would be 101110021.

Multiplexing in a Business Setting

  • In IT support for businesses, a single server may host multiple applications and services directly:
    • Internal websites
    • Mail servers
    • File servers
    • Print servers
  • Multiplexing and demultiplexing enable these diverse functions on a single machine using ports effectively.

Differences Between TCP and UDP

  • TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) differ in reliability and connection management.
    • TCP: Connection-oriented, ensuring data is received accurately and in order.
    • UDP: Connectionless, providing faster but less reliable data transmission.

TCP Three-way Handshake

  • A method used by TCP to establish a connection:
    • Step 1: Client sends a SYN (synchronize) packet to the server.
    • Step 2: Server responds with a SYN-ACK (synchronize-acknowledge) packet.
    • Step 3: Client sends an ACK (acknowledge) packet back to the server.

Usage of TCP Flags

  • TCP flags are used during the connection setup and management processes to control the communication between a client and server, ensuring effective data transfer.

Firewalls and Network Security

  • Firewalls play a crucial role in network security by controlling incoming and outgoing network traffic based on predetermined security rules. They help protect networks from unauthorized access and potential threats.