Networking 2: Review of Basics

Network Topologies

• Network topologies define the physical or logical connections between devices in a communication network.
• Star Topology: Devices connect to a central hub (often a switch or router) with easy management but a single point of failure.
• Ring Topology: Data travels in a circular path, reducing packet collisions, enhancing orderly data transmission.
• Bus Topology: All devices link to a single communication line (bus), simple but can be prone to failures if the bus is damaged.
• Mesh Topology: Every device has a direct link to every other device, promoting high reliability and fault tolerance, commonly used in critical systems.

Networking Devices

• Routers: Connect different networks, directing data packets using headers and forwarding tables for efficient traffic management.
• Switches: Operate at the data link layer, connecting devices within the same network, filtering traffic based on MAC addresses.
• Gateways: Bridge different networks by allowing communication across various protocols (e.g., IP, TCP, HTTP).
• Modems: Convert data between digital and analog formats, essential for internet communication.
• Hubs: Basic devices connecting multiple Ethernet devices, functioning as a single network segment.
• Bridges: Connect multiple networks at the data link layer, filtering traffic by storing MAC addresses.
• Brouters: Combine the functions of bridges and routers, filtering data and routing packets across networks.

OSI Model

• The OSI Model consists of seven layers that describe how data moves through a network.
  • Physical Layer: Transmits raw data through physical media (e.g., Ethernet cables, fiber optics).
  • Data Link Layer: Manages framing of data between devices (e.g., switches, bridges).
  • Network Layer: Routes data packets (e.g., routers).
  • Transport Layer: Ensures reliable data transfer (e.g., TCP, UDP).
  • Session Layer: Manages sessions between applications (e.g., APIs, sockets).
  • Presentation Layer: Translates data formats between network and applications (e.g., encryption protocols).
  • Application Layer: Provides networking services to applications (e.g., HTTP, SMTP, FTP).

IP Addressing

• IP addressing assigns unique numeric identifiers to devices, facilitating their communication.
• Two types of IP addresses:
  • IPv4: Consists of four octets (e.g., 192.168.1.1), limited to about 4.29 billion unique addresses, often extended using NAT.
  • IPv6: Contains eight groups of hexadecimal numbers (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334), vastly expands address space to about 340 undecillion addresses, eliminating the need for NAT.

IPv4 vs. IPv6

• Address Space: IPv4 uses 32 bits while IPv6 uses 128 bits, accommodating a much larger number of devices.
• Notation: IPv4 is expressed in decimal format; IPv6 uses hexadecimal, highlighting the difference in structure and scalability.