IT 520 Midterm Final Prep

3 types of Network Media

Copper, Fiber-Optic and Wireless

Copper Cable

Knows as a twisted pair
Transmits data using electrical signals.

• Common in LANs.

• Includes UTP (Unshielded Twisted Pair) and STP (Shielded Twisted Pair).

Fiber Optic Cable

• Transmits data using light.

• Immune to electromagnetic interference.

  • Used for long-distance, high-speed communication.

Wireless Media

• Transmits data using radio waves or infrared signals.

  • Common in Wi-Fi and Bluetooth networks.

Data Signaling For Each Medium

• Copper: Electrical voltage variations.

• Fiber: Pulses of light.

• Wireless: Radio frequencies (RF signals).

Twisted Pair COnfiguriations

Straight Through, Crossover and Rollover

Straight-Through Cable

• Used to connect different device types (e.g., PC → switch).

• Pins 1→1, 2→2, etc.

Crossover Cable

• Used to connect similar devices (e.g., switch → switch, PC → PC).

  • Transmit and receive pairs are crossed (1→3, 2→6).

Rollover Cable

• Used for console connections between a computer and a router/switch.

  • One end’s pinout is the complete reverse of the other.

Single-Mode Fiber (SMF)

• Transmits one light signal straight down the core.

• Long-distance (tens of kilometers).

• Smaller core (≈9 microns).

• Uses laser light source.

Multi-Mode Fiber

• Transmits multiple light signals bouncing through the core.

• Shorter distances (up to ~2 km).

• Larger core (≈50–62.5 microns).

  • Uses LED light source.

Types of Connectors

RJ-45, LC, SC,ST and BNC

RJ-45

Used for Ethernet (copper cables).

LC,SC and ST

Used for fiber-optic cables.

BNC

Used in older coaxial networks

Types of Antennas

Omnidirectional, Unidirectional and Parabolic

Omnidirectional Antenna

• Sends and receives signals in all directions.

  • Used in most Wi-Fi routers.

Unidirectional Antenna

• Focuses signal in a single direction.

  • Used for long-distance point-to-point links.

Parabolic Antenna

• Uses a curved dish to focus the signal tightly.

• Longest range and high precision.

Types of signal propagation

Reflection, refraction, diffraction scattering and absorption

Reflection

Signal bounces off a surface.

Refraction

Signal bends as it passes through a medium.

Diffraction

Signal bends around obstacles.

Scattering

Signal spreads in multiple directions after hitting a rough surface.

Absorption

Signal is weakened when passing through materials.

Association

The process of a wireless device (station) connecting to an access point (AP).

RTS (Request to send)

• Sent by a device to request permission to transmit.

  • Helps prevent collisions on a shared medium.

CTS (Clear to Send)

Response from the AP granting permission to send data.

Active Scanning

• Device sends probe requests to locate available networks.

• Access points respond with probe responses.

  • Faster but creates traffic.

Passive Scanning

• Device listens for beacon frames from access points.

  • Slower but quieter (less network noise).

WEP (Wireless Security)

Weak, outdated encryption standard.

WPA/WPA2/WPA3

Modern wireless encryption protocols (WPA3 is the most secure).

Layer 2 Addressing

Uses MAC addresses (physical hardware addresses) for communication within the same network segment.

Layer 3 Addressing

Uses IP addresses (logical addresses) for routing data between different networks.

Layer 4 Addressing

Uses port numbers to identify specific applications or services on a host.

Class A

1.0.0.0 – 126.255.255.255
Default Subnet Mask: 255.0.0.0
Large networks (16 million hosts per network).

Class B

128.0.0.0 – 191.255.255.255
Default Subnet Mask: 255.255.0.0
Medium-sized networks (65,000 hosts per network).

Class C

192.0.0.0 – 223.255.255.255
Default Subnet Mask: 255.255.255.0
Small networks (254 hosts per network).

Class D

224.0.0.0 – 239.255.255.255
Used for multicast.

Class E

240.0.0.0 – 255.255.255.255
Experimental; not used for regular networking.

Public IP Addresses

Globally unique and routable on the internet.

Private IP Addresses

Used within private networks; not routable on the internet.
Ranges:

• Class A: 10.0.0.0 – 10.255.255.255

• Class B: 172.16.0.0 – 172.31.255.255

• Class C: 192.168.0.0 – 192.168.255.255

Required Addressing on a Host

IP Address, Subnet Mask, Default Gateway, DNS Server

IP Address

Identifies the device on the network.

Subnet Mask

Defines the network and host portions.

Default Gateway

The route out of the local network.

DNS Server

Resolves domain names to IP addresses.

IPv6 Address

128-bit address written in hexadecimal.

Purpose of IPv7

Provides a vastly larger address space and eliminates the need for NAT.

Data Encapsulation

The process of wrapping data with protocol information at each layer of the OSI model.

Encapsulation Order

Application → Transport → Network → Data Link → Physical

De-Encapsulation Order (receiving data)

Physical → Data Link → Network → Transport → Application

Application Layer

Data

Transport Layer

Segments (uses port numbers)

Network Layer

Packets (uses IP addresses)

Data Link Layer

Frames (uses MAC addresses)

Physical Layer

Bits (raw data transmission)

TCP (transmission Control Protocol)

• Connection-oriented

• Reliable, ordered, and error-checked

  • Used for web (HTTP/HTTPS), email (SMTP), file transfer (FTP)

UDP (User Datagram Protocol)

• Connectionless

• Fast but unreliable

• Used for streaming, gaming, and VoIP

Common TCP Ports

HTTP – 80
HTTPS – 443
FTP – 20/21
SMTP – 25
SSH – 22
Telnet – 23

Common UDP Ports

DNS – 53
DHCP – 67/68
TFTP – 69
SNMP – 161/162

ARP (Address Resolution Protocol) purpose

Resolves IP addresses (Layer 3) to MAC addresses (Layer 2) on a local network.

ARP Taple

Stored locally; lists known IP-to-MAC mappings.

ARP Request

Broadcast asking, “Who has this IP?”

ARP Reply

Response from the device owning that IP address with its MAC address.

Telenet

• Remote terminal protocol using plaintext.

• Insecure (data is not encrypted).

• Port 23.

SSH (Secure Shell)

• Encrypted remote access for secure logins and management.

• Port 22.

• Preferred alternative to Telnet.

Peer-to-Peer (P2P) Network

A network model where each computer can act as both a client and a server; devices share files and resources directly without a central server.

Client-Server Network

A network model where clients request services or resources from centralized servers that manage access and control.

Advantages of Client-Server Model

Centralized management, scalability, better security, and data backup control.

Advantages of Peer-to-Peer Model

Simple setup, inexpensive, and ideal for small networks.

Purpose of OSI Model

A conceptual framework that standardizes the functions of a communication system into seven layers to ensure interoperability.

OSI Layers (Bottom to Top)

Physical, Data link, network, transport, Session, Presentation and Application

Purpose of OSI

A conceptual framework that standardizes the functions of a communication system into seven layers to ensure interoperability.

OSI Layer 7 - Application Layer

Interface for network applications; provides network services to end users (e.g., HTTP, FTP, SMTP).

OSI Layer 6 - Presentation Layer

Formats and encrypts data; ensures compatibility between systems (e.g., encryption, compression).

OSI Layer 5 - Session Layer

Establishes, manages, and terminates sessions between applications.

OSI Layer 4 - Transport Layer

Manages data transfer and reliability (TCP/UDP); segmentation, sequencing, and error checking occur here.

OSI Layer 3 - Network Layer

Handles logical addressing and routing of packets (IP, ICMP).

OSI Layer 2 - Data Link Layer

Responsible for physical addressing (MAC addresses) and error detection on frames (Ethernet).

OSI Layer 1 - Physical Layer

Transmits raw bit streams over a physical medium; includes cables, switches, and NICs.

OSI Layers (Top to Bottom)

Application, Presentation, Session, Transport, Network, Data Link, Physical

TCP/IP Model Layers

Application, Transport, Internet, Network Access

Difference between OSI and TCP/IP Models

OSI has 7 layers, TCP/IP has 4; TCP/IP is a practical model used in real networks.

Transport Layer Protocols

TCP (connection-oriented) and UDP (connectionless).

Switch

Connects devices on the same network and forwards frames using MAC addresses.

Router

Connects multiple networks and forwards packets using IP addresses.

Hub

Broadcasts data to all connected devices; slower and less secure than a switch.

Bridge

Divides a network into segments to reduce traffic.

NIC (Network Interface Card)

Hardware component that connects a computer to a network.

Access Point (AP)

Provides wireless connectivity to wired networks.

Modem

Converts digital signals to analog and vice versa for communication over telephone lines.

Firewall

Monitors and filters incoming/outgoing network traffic based on security rules.

Electrical Safety

Always unplug equipment before servicing; avoid static discharge by grounding.

ESD (Electrostatic Discharge) Prevention

Use anti-static wrist straps, mats, and grounding techniques.

Cable Management

Label and route cables neatly to prevent damage and confusion.

Lifting Safety

Lift heavy equipment with your legs, not your back

Fire Safety

Use Class C fire extinguishers for electrical fires.

Labeling and Naming Conventions

Standardized labels and names help technicians quickly identify devices, cables, and ports for maintenance and troubleshooting.

Good Labeling Practices

Use clear, permanent, and consistent labeling for cables, ports, racks, and rooms.