USE THIS - WGU D315 - Section 1 - Networks

OSI Model

A conceptual framework used to understand network interactions in seven layers.

Layer 7 - Application

Enables user interaction with applications, provides network services to applications.

Layer 6 - Presentation

Translates data between network and application formats, handles encryption/decryption.

Layer 5 - Session

Manages communication sessions between applications, handles authentication.

Layer 4 - Transport

Ensures reliable data transmission, segments data, performs error-checking.

Layer 3 - Network

Handles packet routing, addressing, and traffic control.

Layer 2 - Data Link

Transmits data frames between nodes, manages access to physical media.

Layer 1 - Physical

Transmits raw bit stream over physical medium, deals with hardware connections.

Hub

Connects multiple devices in a network, broadcasts data to all connected devices.

Modem

Modulates and demodulates signals for data transmission over communication lines.

Repeater

Amplifies and retransmits signals to extend network range.

Switch

Forwards data packets between devices based on MAC addresses.

Bridge

Connects and filters traffic between two network segments.

Router

Forwards data packets between different networks, performs routing.

Shielded Twisted Pair (STP)

Has extra shielding, provides better protection against electromagnetic interference (EMI).

Unshielded Twisted Pair (UTP)

No shielding, suitable for most homes/offices.

RJ45 connector

Connector used with twisted pair cabling.

Electromagnetic Interference (EMI)

Produced by generators, motors, etc., and interferes with electrical pulses over copper cabling.

Cat3

Obsolete Ethernet twisted pair cabling with speed 10 mbps and distance 100 m (328 ft).

Cat4

Obsolete Ethernet twisted pair cabling with speed 16 mbps and distance 100 m (328 ft).

Cat5

Obsolete Ethernet twisted pair cabling with speed 100 mbps and distance 100 m (328 ft).

Cat5e

Modern Ethernet twisted pair cabling with speed 1,000 mbps (1 Gbps) and distance 100 m (328 ft).

Cat6

Modern Ethernet twisted pair cabling with speed 1,000 mbps (1 Gbps) or 10,000 mbps (10 Gbps) over distances of 100 m (328 ft) or 55 m (180 ft).

Cat6a

Modern Ethernet twisted pair cabling, more resistant to interference, with speed 1,000 mbps (1 Gbps) or 10,000 mbps (10 Gbps) over distances of 100 m (328 ft) or 55 m (180 ft).

Ethernet

Outdated cat3 cabling at 10 mbps.

Fast Ethernet

Uses cat5 cabling at 100 mbps.

Gig Ethernet

1,000 mbps (1 Gbps).

Ten Gig Ethernet

10,000 mbps (10 Gbps).

Coaxial Cables

Used for cable TV and some network applications, higher bandwidth than UTP.

Single Mode Fiber

Long-distance transmission, uses laser light.

Multimode Fiber

Shorter distance, uses LED light.

Crossover cable

Connects similar devices directly (e.g., computer to computer).

Patch cable

Connects different devices (e.g., computer to switch).

Ping

Tests network connectivity between hosts.

ipconfig

Displays IP configuration for Windows systems.

ifconfig

Displays IP configuration for Unix/Linux systems.

Traceroute/tracert

Shows the path packets take to reach a destination.

Tracepath

Similar to traceroute, but doesn't require root privileges.

ARP

Displays and modifies the ARP cache.

Netstat

Displays network connections and routing tables.

Nslookup

Queries DNS servers for domain name or IP address mapping.

Dig

More detailed DNS lookup tool.

Whois

Retrieves domain registration information.

Route

Displays and modifies the IP routing table.

SCP

Securely copies files between hosts on a network.

FTP

Transfers files between hosts on a network.

TFTP

Simplified version of FTP for basic file transfers.

Finger

Retrieves information about users on a remote system.

Nmap

Network scanning and security auditing tool.

Tcpdump

Captures and analyzes network traffic.

Telnet/SSH

Remote access to network devices (SSH is secure).

Personal Area Network (PAN)

Small network for personal devices (e.g., Bluetooth).

Local Area Network (LAN)

Network covering a small area (e.g., office, home).

Wireless Local Area Network (WLAN)

LAN using wireless communication.

Storage Area Network (SAN)

Dedicated network for data storage devices.

Campus Area Network (CAN)

Interconnected LANs across multiple buildings.

Metropolitan Area Network (MAN)

Network spanning a city or large campus.

Wide Area Network (WAN)

Large-scale network covering a broad area (e.g., countries).

Bus topology

All devices connect to a single cable.

Ring topology

Devices connect in a circular pattern.

Star topology

All devices connect to a central hub or switch.

Mesh topology

Devices interconnect with multiple paths between them.

Centralized architecture

All resources and control managed from a central point.

Decentralized architecture

Resources and control distributed across multiple points.

Client-Server Model

Clients request services from dedicated servers.

Peer-to-Peer Model

All devices can act as both clients and servers.

Wired network advantage

Higher speeds, more reliable connection.

Wireless network advantage

Mobility, flexibility in device placement.

Type 1 hypervisor

Runs directly on hardware, more efficient.

Type 2 hypervisor

Runs on top of an operating system, easier to set up.

IaaS

Provider manages hardware, customer manages OS and applications.

PaaS

Provider manages hardware and OS, customer manages applications.

SaaS

Provider manages everything, customer only uses the application.

Private Cloud

Cloud infrastructure used by a single organization.

Public Cloud

Cloud services offered to the general public.

Community Cloud

Shared by several organizations with common interests.

Hybrid Cloud

Combination of public and private cloud services.

Multi-Cloud

Use of multiple cloud providers for different services.

Commands UNIQUE to Linux:

tracepath = similar to traceroute, tracing hops
ip = alternative to ipconfig/ifconfig to retrieve IP info
dig = alternative to nslookup for DNS queries
whois = retrieves domain registration info
finger = provides info about logged-in users
SCP = secure file transfer, encrypts data in transit (Secure Copy)

IaaS

Infrastructure as a Service. A cloud computing technology useful for heavily utilized systems and networks. Organizations can limit their hardware footprint and personnel costs by renting access to hardware such as servers.

Paas

Platform as a Service. Provides cloud customers with an easy-to-configure operating system and on-demand computing capabilities.

SaaS

Software as a Service; a subscription service where you purchase licenses for software that expire at a certain date.

A user is experiencing slow internet speeds and suspects network congestion.
Which command can they use to test the latency and response time to a specific destination?

ping

A user suspects that their Windows computer is infected with malware causing network issues.
Which command can they use to display active network connections and processes?

netstat

A user is experiencing network connectivity issues on their Windows computer.
Which command can they use to display the IP configuration of their computer?

ipconfig

A Linux user wants to view the routing table on their system to troubleshoot routing issues.
Which command should they use?

route

A Linux user wants to view detailed information about their network interfaces, including IP addresses, netmasks, and interface status.
Which command should they use?

ifconfig

A Linux user is experiencing slow internet speeds and suspects network congestion. Which command can they use to test network connectivity and measure the round-trip time to a specific destination?

traceroute

IPv6 addresses

128 bits long—use hexadecimal notation separated by colons, while IPv4 addresses are dotted decimals.

Which layer of the OSI model is primarily responsible for translating network addresses into their physical counterparts and deciding how to route data from the sender to the receiver?

OSI Layer 3, Network

A user connects their laptop to a Wi-Fi network in a coffee shop.
Which network component is responsible for managing the wireless connection?

WAP (wireless access point)

A university campus has multiple buildings connected by underground fiber-optic cables.
Which network component manages the flow of data between these buildings?

Router

In a network where all computers communicate through a central server, which type of network architecture is being used?

Client/server

In a network where there is a mainframe computer serving terminals across the organization, which type of network architecture is being used?

Hierarchical

Which OSI layer is responsible for establishing, maintaining, and terminating connections between applications?

OSI Level 5, Session

At which OSI layer does Transmission Control Protocol (TCP) operate?

OSI Layer 4, Transport

Where does Hypertext Transfer Protocol (HTTP) operate in the OSI model?

OSI Layer 7, Application

Four Layers of TCP/IP:

Layer 4 - Application/Process Layer
Layer 3 - Transport/Host-to-Host Layer
Layer 2 - Internet/Internetworking/Network Layer
Layer 1 - Network Interface/Link Layer

TCP/IP model is also called:

DoD Model
DARPA Model

Which TCP/IP layer is responsible for logical addressing and routing?

Layer 2, Internet