Networking and Internet Protocols Lecture Notes

Moving Data Analogy

• Truck Analogy: Moving data is like moving boxes with a truck.
  • Network as Roads: Different types of networks (wireless, DSL, cable, Ethernet) act as roads.
  • Internet Protocol (IP) as Trucks: IP is the truck transporting data.
  • Data as Boxes: Data is encapsulated in boxes within the truck, which can be specific to applications or functions.

Data Encapsulation Process

• Visual Representation: Device on one side, server on the other (web, mail server, etc.).
• Ethernet Frame: Contains the Ethernet payload, which includes IP header and payload.
• IP Payload: Can contain TCP or UDP data.
• Data Encapsulation: Layers within the data – Ethernet, IP, TCP/UDP, HTTP.

TCP and UDP Protocols

• Encapsulation in IP: Both are encapsulated within IP.
• Transport Layer (OSI Layer 4): TCP and UDP operate at this layer.

TCP (Transmission Control Protocol)

• Connection-Oriented: Formal setup and teardown process.
• Reliable Delivery: Ensures data is received and can reorder or retransmit packets if needed.
• Flow Control: Mechanism to adjust sending rate based on receiving capabilities.

UDP (User Datagram Protocol)

• Connectionless: No formal setup or teardown.
• Unreliable: No receipt confirmation, no flow control.
• Use Cases: Real-time communication (e.g., VoIP).

Port Numbers

• Multiplexing: Use of port numbers to direct data to correct application.
• Non-Ephemeral Ports: Permanent ports for consistent access (e.g., HTTP on port 80).
• Ephemeral Ports: Temporary ports used by clients in communication.
• Common Port Numbers: TCP 80 (HTTP), TCP 443 (HTTPS), TCP 25 (Mail), UDP 123 (Time).

IP Addressing

• Unique Addresses: Each device on a network has a unique IP address, similar to mailing addresses.

Communication Example

• Client to Server Communication:
  • Client IP: 10.0.0.1, Server IP: 10.0.0.2.
  • HTTP via TCP port 80, VoIP via UDP port 5004, Email via TCP port 143.
  • Source and Destination Ports: Random source ports; destination ports are well-known.

Security and Port Scanning

• Port Scanning: Port numbers are not security mechanisms; they can be scanned and identified.

Summary

• Port numbers and IP addresses help manage multiple simultaneous connections.
• TCP and UDP serve different roles based on the need for reliable delivery or speed.