Moving truck: Represents Internet Protocol (IP) in networking, transporting data (boxes) over networks (roads).
Roads: Different types of networks (wireless, DSL, cable modem, Ethernet switch).
Data Encapsulation
Encapsulation: Wrapping data within data units (boxes in trucks), moving it over networks.
Payloads: Different data types (application data) encapsulated within protocols.
Network Protocols
Ethernet Frames
Ethernet Payload: Contains IP header and IP payload.
IP Payload: Can contain TCP (Transmission Control Protocol) with headers and data.
IP Protocol
IP Addressing: Unique addresses for devices in a network.
IP Packet: Contains encapsulated TCP or UDP (User Datagram Protocol) data.
TCP vs. UDP
Transmission Control Protocol (TCP)
Connection-oriented: Formal setup and teardown of communication.
Reliable delivery: Ensures data is received and can reorder out-of-order messages.
Flow control: Manages data transmission rates.
User Datagram Protocol (UDP)
Connectionless: Simple, no formal setup/teardown.
Unreliable by design: No acknowledgments, used for real-time communication (e.g., VoIP).
Common applications: DHCP (Dynamic Host Configuration Protocol), TFTP (Trivial File Transfer Protocol).
Port Numbers and Multiplexing
Port Numbering System
Purpose: Directs data to specific applications/services (rooms in a house metaphor).
Common Port Examples:
Port 80: HTTP
Port 443: HTTPS
Port 25: Email (SMTP)
Port 123: Time server
Well-Known and Ephemeral Ports
Non-ephemeral ports: Permanent, used consistently for known services.
Ephemeral ports: Temporary, dynamically assigned for client-server communication.
Server and Client Communication
Client IP and server IP: Identify devices in communication.
Protocols: TCP/UDP used to transport data.
Multiplexing: Allows multiple applications to communicate simultaneously.
Security Considerations
Port Numbers in Security
Not a security mechanism: Ports are for identifying services, not securing them.
Port scanning: Can detect open ports, showing services available on servers.
Practical Scenario
Client-server interaction: Example of communication between devices with IPs, using specific port numbers for different services (web traffic, VoIP, email).
Ports and protocols: Ensure data is routed correctly within networks.