Lecture on Network Topologies and Related Concepts

Topologies

Star Topology

• Central wiring point (hub or switch)
• Data passes through the central point
• Benefits: Failure of one computer or cable doesn't affect others
• Disadvantage: Central hub/switch failure affects all computers (single point of failure)

Bus Topology

• Computers and network devices connected to a single cable (backbone)
• Backbone: Coaxial cable, connectors BNC (T-connectors)
• Advantages: Cheap, easy to implement
• Disadvantages: Cable must be terminated at both ends; open connections cause data reflection

Ring Topology

• Closed loop configuration; each computer has two neighbors
• Data packets sent around the ring
• Advantages: Easy to install and troubleshoot
• Disadvantages: Single computer or cable failure disrupts data flow

Mesh Topology

• Each computer connected to every other computer
• Advantages: High redundancy; handles failures well
• Disadvantages: Expensive due to cabling and network cards

Hybrid Topology

• Combination of multiple topologies
• Common Forms: Star-ring, star-bus

Point-to-Point Topology

• Two hosts directly connected using a single cable

Client-Server Topology

• Clients connect to a centralized server for resources
• Simplifies administration

Point-to-Multipoint Topology

• Central wireless base station with multiple client locations
• Clients communicate with the base station, not each other

Peer-to-Peer Topology

• Clients share resources directly with each other
• Common in homes and small businesses

Connectors and Cabling

RJ-11 Connector

• 4-wire connector, used for telephone equipment and modems

RJ-45 Connector

• 8-wire connector, most common in networking

RJ-48C Connector

• Used with shielded twisted pair, primarily for T1 lines

UTP Coupler

• Connects UTP cables with RJ-45 connectors

BNC Connector

• Common RF connector for coaxial cable, used in video and audio

Fiber Coupler vs. Fiber Adapter

• Fiber Coupler: Joins two same fiber optic connectors
• Fiber Adapter: Joins different fiber optic connectors

USB Connector

• Widely used in desktops and laptops
• Types: Type A and Type B

IEEE 1394 (Firewire) Connector

• Used for peripheral devices like cameras and printers

Fiber Optic Connectors

• MTRJ: Mechanical Transfer Registered Jack, small form factor
• ST: Straight Tip, half-twist bayonet lock
• LC: Local Connector, jack similar to RJ-45
• SC: Standard Connector, push-pull

Serial Cables (RS-232)

• Send data one bit at a time

UPC vs. APC Connectors

• UPC: Light reflects back, causes signal loss
• APC: Angled connection, reduces signal loss

Ethernet Over HDMI (IEEE 1901-2013)

• Adds data channel to HDMI cable, 100 Mbits per second

Ethernet Over Powerline

• Uses building's electrical wiring for networking

Cable Standards

Ethernet Cable Standards

• 10 BASE-T: 10 Mbits/sec, twisted pair
• 10 BASE-2: 10 Mbits/sec, coaxial cable
• 100 BASE-T: 100 Mbits/sec, Cat 5 or higher
• 100 BASE-FX: 100 Mbits/sec, fiber optic
• 1000 BASE-T: 1000 Mbits/sec, Cat 5 or higher
• 10G BASE-T: 10 Gbits/sec, Cat 6A

Fiber Optic Cable Modes

• Single-Mode: Long distances
• Multi-Mode: Short distances

Networking Devices

Hubs vs. Switches

• Hub: Multiple ports, copies data to all ports, not intelligent
• Switch: Learns device addresses, directs data to specific ports, intelligent
• Multi-layer Switch: Operates at Layer 2 and Layer 3
• Content Switch: Operates at Layers 4-7, performs load balancing

Power Over Ethernet (PoE)

• Provides electrical power and data over ethernet cable

Spanning Tree Protocol (STP)

• Prevents broadcast traffic loops, ensures fault tolerance

Bridges

• Divide network into separate collision domains, filter data based on MAC addresses

Routers

• Forward data between networks based on IP addresses, serve as network gateways

CSU/DSU

• Converts data between LAN and WAN

Network Interface Card (NIC)

• Connects computer to network, converts serial data to parallel data

Transceivers

• Devices with both transmitter and receiver

Wireless Access Points

• Connects wireless devices to a wired network

Dial-Up Modems

• Convert analog data from telephone lines to digital data

Wireless Technologies

IEEE 802.11 Standards

• 802.11a: 1999, 802.11b: 1999, 802.11g: 2003, 802.11n: 2009, 802.11ac: 2014

Infrared

• Requires line of sight, ineffective in direct sunlight

Bluetooth

• Short-range radio, 2.4 GHz, max speed 24 Mbits/sec

IP Addressing

IPv4 and IPv6

• IPv4: 32-bit address, over 4 billion addresses
• IPv6: 128-bit hexadecimal address, 340 undecillion addresses

Subnetting

• Divides large networks into smaller subnets
• Subnet mask defines network and host portions
• Classes: A, B, C, each with default subnet masks

Private vs. Public IP Addresses

• Public: Registered on the internet
• Private: Not registered, used in local networks
• RFC 1918: Defines private IP address ranges

Dynamic vs. Static IP Addressing

• Dynamic: Assigned automatically by DHCP server
• Static: Manually assigned, does not change

DHCP

• APIPA: Automatic private IP address assignment if DHCP server is unavailable
• Scope: Range of IP addresses DHCP can assign
• Reservation: Ensures specific device always gets the same IP

Protocols

TCP vs. UDP

• TCP: Connection-oriented, guarantees data delivery
• UDP: Connectionless, doesn't guarantee data delivery

FTP and TFTP

• FTP: File transfer protocol, uses TCP
• TFTP: Trivial file transfer protocol, uses UDP

SMTP and POP3

• SMTP: Sends email, uses TCP
• POP3: Receives email, downloads to computer

IMAP4

• Manages email on server, syncs with local computer

HTTP and HTTPS

• HTTP: Retrieves web pages, data in clear text
• HTTPS: Secure web pages, encrypts data

Telnet and SSH

• Telnet: Terminal emulation, sends commands, not secure
• SSH: Secure shell, creates secure tunnel for data

ARP and RARP

• ARP: Resolves IP addresses to MAC addresses
• RARP: Resolves MAC addresses to IP addresses

NTP

• Synchronizes clocks with US Naval Observatory Master Clocks

SCP

• Secure Copy Protocol, uses SSH for secure data transfer

SNMP

• Simple Network Management Protocol, collects data from network devices

RTP

• Real-Time Transport Protocol, used for streaming audio and video

ISDN, T1, and T3

• ISDN: Digital transmission over telephone lines
• T1: 1.544 Mbits/sec
• T3: 43 Mbits/sec

VPN

• Site-to-Site: Connects two offices over the internet
• Host-to-Site: Connects individual user to office network
• Host-to-Host: Connects two computers over the internet

Authentication Protocols

• PAP: Password Authentication Protocol, sends clear text
• CHAP: Challenge Handshake Authentication Protocol, encrypts data
• MS-CHAP: Microsoft's version with mutual authentication
• Radius: Centralized authentication
• Kerberos: Uses tickets for authentication
• EAP: Extensible Authentication Protocol, supports multiple methods

Troubleshooting Tools

Wire Crimper

• Makes custom-length network cables

Punch Down Tool

• Connects wires to punch-down blocks

Media Tester

• Tests cables for correct wiring

Cable Stripper

• Removes outer plastic shielding from cables

TDR and OTDR

• TDR: Tests cables by transmitting a signal
• OTDR: Similar to TDR but for fiber optic cables

Multimeter

• Measures voltage, resistance, current, and continuity

Butt Set

• Tests and monitors telephone lines

Voltage Event Recorder

• Collects data on power quality

Tone Generator

• Locates cables by generating a tone

Protocol Analyzer

• Troubleshoots and analyzes network traffic

Security Protocols

Firewalls

• Filter incoming and outgoing traffic
• Host-Based: Protects individual computer
• Network-Based: Protects entire network
• Stateful: Monitors all connections and data streams
• Stateless: Uses access control list only

Content Filtering and Signature Identification

• Content Filtering: Filters data based on content
• Signature Identification: Detects viruses by behavior patterns

Intrusion Detection/Prevention System (IDS/IPS)

• Alerts and prevents network from outside attacks

568A and 568B Standards

• Define how twisted pair cables should be wired to RJ-45 connectors
• Straight Cable: Same standard on both ends
• Crossover Cable: Different standards on each end

Networking Models

OSI Model

• Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application
• Physical Layer: Network standards, connectors, cables, voltages
• Data Link Layer: Encodes/decodes bits, flow control, frame synchronization
• Network Layer: Routes data packets based on IP addresses
• Transport Layer: Ensures data transfer, resends lost packets
• Session Layer: Manages connections
• Presentation Layer: Converts data form for network
• Application Layer: Manages communications between applications

TCP/IP Model

• Used for internet communications
• Layers: Network Interface, Internet, Transport, Application

Additional Topics

Cable Management and Safety

• Use ESD wrist straps and mats to prevent electrostatic discharge
• Proper disposal of equipment to protect the environment
• Safety rules: Turn off power, remove hand jewelry, locate fire extinguishers

Virtualization

• Virtual Servers: Run multiple servers on one physical machine
• Virtual Switches, Routers, Firewalls: Software-based network devices

Cloud Computing

• Types: IAAS, PAAS, SAAS
• IAAS: Manages hardware
• PAAS: Manages hardware and software
• SAAS: Manages entire application

Storage Solutions

• NAS: Network Attached Storage, dedicated for storing data
• SAN: Storage Area Network, high-speed network for large data storage
• Fiber Channel: Standard for SAN, high-speed
• iSCSI: Transports iSCSI requests over TCP/IP

Patch Panels and Blocks

• 66 Block: Outdated punch-down block
• 110 Block: Modern punch-down block, supports Cat 5e
• Patch Panel: Multiple cable connections for networks

Demarcation and Extensions

• Demarc: Point where customer and service provider equipment meet
• Demarc Extension: Extends demarc inside building
• Smart Jack: Terminates T carriers service wires, monitors network

VLANs

• Virtual LAN: Controls network traffic logically, not physically

Network Types

• Intranet: Internal private network
• Extranet: Private network accessible outside organization
• PAN: Personal area network
• LAN: Local area network
• MAN: Metropolitan area network
• WAN: Wide area network

Network Troubleshooting

• Steps: Identify symptoms and cause, affected area, changes, select probable cause, implement action plan, test result, document solution

Network Utilities

• Ping: Tests connectivity
• Pathping: Combines Ping and Tracert
• Tracert: Shows path of data packet
• Nbtstat: Resolves Netbios names
• ARP: Resolves IP to MAC addresses
• Netstat: Displays network connections
• Ipconfig: Shows network configuration
• Nslookup: Looks up DNS information
• Ifconfig: Linux/Unix version of Ipconfig
• Dig: Unix version of Nslookup