Lecture Notes: Network Topologies and Communication Devices

Network Topologies

• Topology Definition: The layout of how a network communicates with different devices.
  • Star Topology
    • Central wiring point (hub or switch).
    • Data passes through central point.
    • Advantages:
      • If one computer fails or a cable breaks, others are unaffected.
    • Disadvantages:
      • Central hub/switch failure affects the entire network (single point of failure).
  • Bus Topology
    • Uses a single cable or backbone.
    • Connects via BNC (T-connectors).
    • Advantages:
      • Cost-effective and easy to implement.
    • Disadvantages:
      • Requires terminators at both ends.
      • Open connections lead to signal reflection, disrupting data flow.
  • Ring Topology
    • Computers connected in a closed loop.
    • Advantages:
      • Easy to install and troubleshoot.
    • Disadvantages:
      • Single computer or cable break disrupts communication.
  • Mesh Topology
    • Each computer connected to every other computer.
    • Advantages:
      • High redundancy; handles failure well.
    • Disadvantages:
      • Requires extensive cabling; expensive.
    • Example: The Internet.
  • Hybrid Topologies
    • Combination of multiple topologies.
    • Common Forms: Star-ring, Star-bus.
  • Point-to-Point Topology
    • Direct connection between two hosts.
  • Client-Server Topology
    • Clients connect to a centralized server for resources.
  • Point-to-Multipoint Topology
    • Central wireless base station with multiple connecting clients.
  • Peer-to-Peer Topology
    • Clients share resources with each other directly.

Network Connectors and Cables

• RJ-11 Connector
  • 4-wire connector mainly used for telephone equipment.
  • RJ-45 Connector
    • 8-wire connector for local area networks (LAN).
  • RJ-48C Connector
    • Used with shielded twisted pair (STP) cable, primarily for T1 lines.
  • UTP Coupler
    • Extends unshielded twisted pair (UTP) cables.
  • BNC Connector
    • Used on coaxial cable for RF connectors.
  • Fiber Couplers and Adapters
    • Join similar or different types of fiber optic connectors.
  • F-type Connector
    • Threaded connector for coaxial cables, often used by cable providers.
  • USB Connector
    • Common for desktops and laptops.
  • IEEE 1394 (FireWire) Connector
    • Used for multimedia devices.
  • Fiber Optic Connectors
    • Includes MTRJ, ST, LC, SC types each with specific uses and locking mechanisms.

Cable Standards and Specifications

• Serial Cables
  • Carries data one bit at a time (RS-232 standard).
  • Ethernet Cable Standards
    • Examples: 10 BASE-T, 10 BASE-2, 100 BASE-T, 100 BASE-FX, 1000 BASE-T, 10G BASE-T, 10G BASE-SR, etc.
  • Plenum-rated Cables
    • Required for spaces with open airflow (fire-resistant and low-toxic if burned).
  • DOCSIS Standards
    • Data over cable service interface specifications, e.g., DOCSIS 3.1 supports 10 Gbps downstream.

Networking Devices

• Hub
  • Multiple ports, not intelligent (copies data to all ports).
  • Switch
    • Intelligent, directs data to intended destination (stores MAC addresses).
    • Multilayer Switch: Operates at Layers 2 and 3 of the OSI model.
    • Content Switch: Operates at Layers 4-7, performs load balancing.
  • Power over Ethernet (PoE)
    • Provides power and data through Ethernet cable.
  • Spanning Tree Protocol (STP)
    • Prevents data loops and allows for fault tolerance in networks.
  • Bridges
    • Divides network into separate collision domains.
  • Routers
    • Routes data based on IP addresses, acts as a gateway.
  • Wireless Access Points
    • Connects wireless devices to a wired network.
  • Modems (Dial-up, ISDN, DSL)
    • Converts data for transmission over telephone lines.

OSI Model

• Seven Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.
  • Functions and Examples:
    • Application: Manages application protocols (email, HTTP, FTP).
    • Presentation: Data compression, encryption, decryption.
    • Session: Establishes and manages sessions (dialogue control).
    • Transport: Ensures data delivery and resending lost packets (TCP).
    • Network: Routes data based on IP addresses.
    • Data Link: Encodes and decodes data packets into bits.
    • Physical: Defines electrical and physical network characteristics.

IP Addressing

• IPv4: 32-bit numeric address, written in 4 octets.
  • IPv6: 128-bit hexadecimal address, written in 8 sets of 16 bits.
  • Subnet Masks: Defines network and host portions of an IP address (default masks for Class A, B, C).
  • Classful IP Addressing: Describes IP address distribution (Classes A, B, C, ranges, and default subnet masks).
  • Private vs. Public IP Addresses: Private IPs not publicly registered, used internally.
  • Subnetting: Breaking down a network into smaller subnets for better management.

DHCP

• Dynamic IP Addressing: Automatically assigns IP addresses from a DHCP server.
  • Static IP Addressing: Manually assigned IP addresses.
  • APIPA: Automatic Private IP Address Assignment used when DHCP server is unreachable.
  • DHCP Scope: Range of IP addresses assigned by the DHCP server.
  • Reservations: Ensures specific devices always get the same IP address.
  • Lease Duration: Time an IP address is assigned to a device before renewal.
  • DHCP Relay: Forwards DHCP requests from different subnets.

Protocols

• TCP: Connection-oriented, ensures data delivery with a 3-way handshake.
  • UDP: Connectionless, no guarantee of data delivery.
  • FTP, TFTP, SMTP, POP3, IMAP4, HTTP, HTTPS: Various protocols for file transfer and messaging.
  • Telnet and SSH: Remote access protocols (SSH is secure).
  • ARP and RARP: Resolves IP addresses to MAC addresses (and vice versa).
  • DNS and WINS: Resolves domain names to IP addresses and NetBIO names to IP addresses, respectively.
  • NAT and PAT: Translates private IP addresses to public IP addresses (PAT uses port numbers).
  • Snmp: Collects data from network devices.
  • RTP/RTCP: Used for real-time data like audio and video.
  • VPN and IPsec: Secure networks over the internet, encrypt data.
  • PPP and PPTP: Protocols for point-to-point and tunneling.

Network Troubleshooting

• TCP/IP Utilities: ping, tracert, netstat, ipconfig, nslookup, dig, etc.
  • Network Testing Tools: Wire crimper, media tester, cable stripper, TDR/OTDR, multimeter, etc.
  • Wireless Issues: Interference, antenna type/placement, encryption mismatches.
  • Common Problems: Media issues, wrong cables, DHCP failures, DNS problems, link LED indicators.
  • Troubleshooting Steps:
    • Identify symptoms and causes.
    • Identify affected area.
    • Establish changes made.
    • Select probable cause.
    • Implement and test action plan.
    • Document solution and process.

Network Virtualization

• Virtualization: Consolidates physical servers into one virtual server running multiple OSs.
  • Virtual Devices: Virtual Switch, Virtual Router, Virtual Firewall.

Cloud Computing

• Types of Cloud Services: IAAS, PAAS, SAAS.
  • Benefits: Offloads hardware/software management, remote access.
  • Examples: Amazon Web Services, Microsoft Azure, Google Apps.

Storage Solutions

• NAS: Network Attached Storage, used for storing data, accessed over a network.
  • SAN: Storage Area Network, high-speed network for large data access.
  • RAID Configurations: Used for redundancy in NAS and SAN.

Physical Network Components

• Patch Panels, 66/110 blocks: Connect and manage network cables.
  • MDF/IDF: Main/Intermediate Distribution Frames for wiring.
  • Demarcation Point: Where the service provider's and customer’s equipment meet.
  • Smart Jacks: Monitors network errors and connectivity.

VLAN and Network Access

• VLAN: Virtual LAN, separates network traffic for different departments logically.
  • Intranet vs. Extranet: Intranet is internal access; Extranet allows restricted external access.
  • Bandwidth and Traffic Shaping: Prioritizes important data, controls network traffic.