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Final Exam Notes

Exam Notes for Networking Essentials

Network Media Types

Guided Media (Wired)

Twisted Pair Cable

Unshielded Twisted Pair (UTP)

Commonly used in Ethernet networks.

Cheaper and easier to install.

Susceptible to electromagnetic interference (EMI).

Uses RJ-45 connectors.

Shielded Twisted Pair (STP)

Similar to UTP but includes shielding to reduce EMI.

More expensive than UTP.

Provides better noise protection.

Coaxial Cable

Consists of a central conductor surrounded by insulation, shielding, and an outer cover.

Better shielding and bandwidth than twisted pair cables.

Uses BNC connectors.

Used in cable TV and older Ethernet networks.

Fiber Optic Cable

Transmits data as light pulses through glass or plastic fibers.

Immune to electromagnetic interference.

Offers the highest bandwidth and speed.

Types:

Single-Mode Fiber (SMF): Long-distance communication.

Multi-Mode Fiber (MMF): Shorter distances.

Requires careful installation due to sensitivity to bending.

Unguided Media (Wireless)

Radio Waves

Frequency range: 3 kHz to 1 GHz.

Omnidirectional transmission.

Used in Wi-Fi and mobile communications.

Microwaves

Frequency range: 1 GHz to 300 GHz.

Unidirectional and requires line of sight.

Used in satellite and point-to-point communications.

Infrared

Short-range communication.

Requires line of sight and cannot penetrate walls.

Commonly used in remote controls.

Network Interface Cards (NICs)

Function: Hardware component that connects a computer to a network.

Key Characteristics:

Provides a physical interface for network connections.

Contains a unique MAC address (Media Access Control address).

Operates at both the Physical Layer (Layer 1) and the Data Link Layer (Layer 2) of the OSI model.

Manages data encoding/decoding and media access control.

MAC Address

Structure:

48 bits in length, expressed in hexadecimal format.

First 24 bits (OUI): Organizationally Unique Identifier assigned to the manufacturer.

Last 24 bits: Unique identifier for the NIC.

Broadcast MAC Address: FF-FF-FF-FF-FF-FF used to send data to all devices on a local network.

Ethernet Technology

Overview:

The most common LAN technology.

Uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection) for media access control.

Supports various speeds and standards.

Ethernet Standards and Speeds

10 Mbps: 10Base-T (Ethernet)

100 Mbps: 100Base-TX (Fast Ethernet)

1 Gbps: 1000Base-T (Gigabit Ethernet)

10 Gbps: 10GBase-T (10 Gigabit Ethernet)

Key Concepts

Auto-MDIX

Automatically detects the type of Ethernet cable (straight-through or crossover) and adjusts accordingly.

Eliminates the need for crossover cables.

CSMA/CD

Nodes check if the network medium is free before transmitting.

If a collision is detected, nodes wait for a random backoff time before retrying.

Wi-Fi (Wireless Fidelity)

Frequency Bands:

2.4 GHz Band: 2.4 GHz to 2.4835 GHz.

5 GHz Band: 5.15 GHz to 5.85 GHz.

Characteristics:

Provides mobility and ease of installation.

Susceptible to interference from other devices operating in the same frequency.

Security concerns due to the broadcast nature of wireless signals.

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OSI Model vs. TCP/IP Model

OSI Model (7 Layers)

Application Layer (Layer 7)

User interface layer for network applications (e.g., web browsers, email clients).

Presentation Layer (Layer 6)

Data translation, encryption, and compression.

Session Layer (Layer 5)

Establishes, manages, and terminates sessions between applications.

Transport Layer (Layer 4)

Provides reliable data transfer with error checking and flow control.

Protocols: TCP (Transmission Control Protocol), UDP (User Datagram Protocol).

Network Layer (Layer 3)

Handles logical addressing and routing (IP addresses).

Protocols: IP, ICMP.

Data Link Layer (Layer 2)

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

Divided into LLC (Logical Link Control) and MAC (Media Access Control) sublayers.

Physical Layer (Layer 1)

Transmits raw bitstreams over physical media (cables, radio waves).

TCP/IP Model (4 Layers)

Application Layer

Combines OSI layers 5, 6, and 7.

Protocols: HTTP, FTP, SMTP, DNS.

Transport Layer

Same as OSI Layer 4.

Protocols: TCP, UDP.

Internet Layer

Equivalent to OSI Network Layer.

Handles packet routing and addressing.

Protocols: IP, ICMP, ARP.

Network Access Layer

Combines OSI layers 1 and 2.

Handles physical network hardware and media.

Protocols: Ethernet, Wi-Fi.

Comparison and Key Differences

OSI Model:

A theoretical framework used for understanding and designing a network system.

Provides detailed specifications for each layer.

TCP/IP Model:

A practical model used for real-world network communications, particularly on the internet.

Less granular, combining some OSI layers for simplicity.

TCP Protocol

Transmission Control Protocol (TCP):

Connection-Oriented: Establishes a connection before data transfer using a three-way handshake.

Reliable Data Transfer: Ensures data is delivered accurately and in order.

Flow Control and Congestion Control: Manages data flow to prevent network congestion.

Error Checking: Uses checksums to detect errors in transmitted segments.

TCP Three-Way Handshake

SYN: Client requests a connection by sending a SYN (synchronize) packet to the server.

SYN-ACK: Server acknowledges by sending back a SYN-ACK (synchronize-acknowledge) packet.

ACK: Client sends an ACK (acknowledge) packet to establish the connection.

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IP Addressing and Classes

IP Address Classes

Class A: 1.0.0.0 to 126.255.255.255

Default Subnet Mask: 255.0.0.0

Large networks with many hosts.

Class B: 128.0.0.0 to 191.255.255.255

Default Subnet Mask: 255.255.0.0

Medium-sized networks.

Class C: 192.0.0.0 to 223.255.255.255

Default Subnet Mask: 255.255.255.0

Small networks.

Class D: 224.0.0.0 to 239.255.255.255

Used for multicast.

Class E: 240.0.0.0 to 254.255.255.255

Reserved for experimental use.

Determining IP Address Class Quickly

First Octet Method:

1-126: Class A

128-191: Class B

192-223: Class C

224-239: Class D

240-254: Class E

Note: 127.0.0.0 is reserved for loopback testing.

Private IP Address Ranges

Class A: 10.0.0.0 to 10.255.255.255

Class B: 172.16.0.0 to 172.31.255.255

Class C: 192.168.0.0 to 192.168.255.255

Route Summarization (Supernetting)

Purpose: Reduces the number of routing table entries by combining multiple routes into a single summary route.

Benefits: Simplifies routing, reduces memory usage, and improves routing efficiency.

Quick Method for Summarization

Group Consecutive Networks:

Networks must be contiguous and have the same next hop.

Determine the New Subnet Mask:

Identify the common bits in the network addresses.

Reduce the subnet mask to include all grouped networks.

Use the Lowest Network Address:

The summarized route uses the lowest network address of the group.

Example

Given Routes with Same Next Hop:

192.168.2.0/24

192.168.3.0/24

Summarized Route:

192.168.2.0/23

Includes both 192.168.2.0 and 192.168.3.0 networks.

Important Considerations

Same Next Hop Requirement:

Only summarize routes that share the same next hop.

Avoid Over-Summarization:

Ensure the summarized route does not include unintended networks.

⁠

Understanding Models and Protocols

Models:

Provide a framework for how network communications should occur.

Examples: OSI Model, TCP/IP Model.

Protocols:

Define the rules and conventions for communication between network devices.

Operate within the layers specified by models.

Examples: TCP, IP, HTTP, FTP.

Real-World Analogy

Model: Blueprint of a house, showing different components and their relationships.

Protocol: Specific construction techniques and materials used to build the house according to the blueprint.

Memory Aids

OSI Model Layers:

Mnemonic: "All People Seem To Need Data Processing"

Application

Presentation

Session

Transport

Network

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