Lecture Notes on Networking: Internet Protocol and Data Transmission

Introduction to Networking

• Moving Truck Analogy: Moving a box using a moving truck is analogous to sending data over a network.
  • Network as the Road: Different types of networks (wireless, DSL, cable, Ethernet) serve as the roads.
  • Internet Protocol as the Truck: IP acts as the truck transporting data.
  • Data as the Box: Data is encapsulated in packets (boxes) within the IP (truck).

Data Encapsulation in Networking

• Encapsulation allows various types of data to be moved across networks efficiently.
• Data is placed inside a 'box' (packet), sent over the network, and unpacked at the destination.

Network Data Flow

• Ethernet Frame: Data travels in Ethernet packets, which contain payloads and headers.
  • IP Header: Contains details about the IP packet.
  • TCP Data: Transmission Control Protocol data is within the IP packet.
  • HTTP Data: HTTP information is within the TCP payload.

Transport Layer Protocols

• TCP (Transmission Control Protocol):

  • Connection-oriented.
  • Reliable delivery with acknowledgment and flow control.
  • Reorders messages and handles retransmission if needed.

• UDP (User Datagram Protocol):

  • Connectionless.
  • Unreliable, no acknowledgment of receipt.
  • Often used for real-time communication (e.g., VoIP, DHCP).

Port Numbers and Multiplexing

• Purpose of Port Numbers: Port numbers direct data to the correct application on the server.

  • Each service (e.g., HTTP, HTTPS, Mail) runs on specific ports.
  • Well-known ports (e.g., 80, 443, 25) are standardized for specific services.

• Ephemeral Ports: Temporary ports used on the client for establishing connections.

  • Range: 1024 to 65535, assigned dynamically.

TCP vs UDP

• TCP Features:

  • Reliable, connection-oriented, with error-checking.
  • Used for applications where data integrity is critical (e.g., HTTPS, SSH).

• UDP Features:

  • Faster, less overhead, ideal for real-time applications.
  • Used when occasional loss of packets is acceptable (e.g., streaming, VoIP).

Security and Port Numbers

• Port Scanning: Port numbers are not for security but for service identification.
  • Easily scanned; not secure by obscurity.

Networking Scenarios

• Client-Server Communication:

  • Each device has a unique IP address.
  • Communication involves specific port numbers for different services.

• Protocol and Port Number Examples:

  • HTTP uses TCP port 80, HTTPS uses TCP port 443.
  • Email might use TCP port 143.

• Service Differentiation: TCP and UDP can use the same port numbers for different services, but it’s not common practice.

Summary

• IP as a Delivery Service: Moves data between IP addresses.
• Port Numbers as Room Numbers: Direct data to specific services on a host.
• Understanding Protocols: Critical for managing data flow and ensuring correct delivery on networks.