TCP/IP

Overview

The TCP/IP (Transmission Control Protocol/Internet Protocol) stack is a set of protocols that define how data is transmitted over the Internet. The TCP/IP model breaks down data transmission into layers, each responsible for specific tasks, ensuring that data moves from one device to another efficiently and accurately. This model is essential for networking as it provides a standardised method of communication across different systems and devices.

Purpose and Benefits of Layering Protocols

Layering protocols in networking provides several key benefits:

1. Modularity: Each layer in the TCP/IP stack performs a specific function, making the network model easier to manage and troubleshoot. Changes or updates can be made to individual layers without affecting others.
2. Interoperability: By following standardised layers, devices and software from different manufacturers can communicate and work together across a network.
3. Efficient Data Transmission: Layering allows each protocol layer to specialise, in optimising processes like routing, addressing, and data verification, which ensures faster and more reliable data transfer.

Layers of the TCP/IP Stack

The TCP/IP stack is divided into four layers:

Application Layer

• Purpose: This layer interacts directly with user applications and provides network services like web browsing and email. It enables applications to format, encrypt, and prepare data for transfer.
• Protocols: Common protocols at this layer include HTTP (for web browsing), FTP (file transfer), SMTP (email), and DNS (domain name system).
• Example: When a user accesses a webpage, the browser uses HTTP to request data from the server.

Transport Layer

• Purpose: Responsible for establishing, maintaining, and terminating connections between devices. It ensures data is transferred reliably by breaking it into packets, managing error checking, and controlling data flow.
• Protocols:
  • TCP (Transmission Control Protocol): Ensures reliable, ordered data transmission. Used in applications where data accuracy is critical, such as file transfers and emails.
  • UDP (User Datagram Protocol): Offers faster but less reliable data transfer, suitable for applications where speed is prioritised over accuracy, such as streaming or online gaming.
• Example: TCP divides a large email message into smaller packets and reassembles them at the receiver's end in the correct order.

Internet Layer

• Purpose: This layer handles logical addressing and routing, directing data packets across networks. It determines the best path for data to travel to reach its destination.
• Protocols:
  • IP (Internet Protocol): Responsible for assigning IP addresses to devices and routing packets to their destinations. Every device on a network has a unique IP address that identifies it.
• Example: When a user requests a webpage, IP identifies the destination server's IP address and directs the packets accordingly.

Network Access Layer (also known as the Link Layer)

• Purpose: This layer is responsible for physically transmitting data across the network. It includes the hardware and physical protocols needed to send and receive data on a specific network medium (like Ethernet or Wi-Fi).
• Protocols: Protocols like Ethernet and Wi-Fi operate at this layer, converting data into signals suitable for the physical network medium.
• Example: When data reaches the Network Access Layer, it's converted into electrical, optical, or radio signals and transmitted over the appropriate medium (cable or wireless).

Data Transmission on the Internet

The TCP/IP stack facilitates reliable data transmission through packet switching and IP addressing:

IP Addresses

• Definition: An IP address is a unique numerical identifier assigned to each device on a network. It allows devices to locate and communicate with each other over the internet.
• IPv4 and IPv6: IPv4 uses 32-bit addresses, limiting the total number of unique addresses. IPv6, which uses 128-bit addresses, was developed to provide a vastly larger address space for future growth.
• Example: A user's computer may have an IP address like 192.168.1.10, while the server it wants to reach has an IP like 203.0.113.5.

Packets

• Definition: Data is divided into small, manageable units called packets. Each packet contains part of the original data, along with information such as the sender's and receiver's IP addresses and a sequence number.
• Purpose: Dividing data into packets makes transmission faster and more efficient, especially over congested networks, as packets can travel independently and be reassembled at the destination.
• Example: When a user sends a large file, the file is divided into packets, each routed individually to the destination. If one packet is lost, only that packet needs to be resent, not the entire file.

How Data Travels

1. Data is broken into packets: At the Transport Layer, data from applications is split into packets.
2. Addressing and routing: At the Internet Layer, each packet is assigned a destination IP address and routed independently to reach its target.
3. Transmission over physical media: At the Network Access Layer, packets are sent over cables, fibre, or wireless networks to reach the destination.
4. Reassembly: At the destination, packets are reassembled in the correct order and presented to the application.

Benefits of the TCP/IP Model

1. Reliability: The layered approach ensures that each part of data transmission is handled efficiently, with protocols like TCP providing error checking and recovery if packets are lost.
2. Flexibility: TCP/IP is compatible with almost all hardware and operating systems, making it highly adaptable to new technologies and different network environments.
3. Scalability: TCP/IP supports vast, complex networks and can scale from small LANs to the global internet without significant changes.
4. Interoperability: TCP/IP standardises communication across devices, making it easier for hardware and software from different vendors to work together.

Note Summary