Understanding Computer Networks

Networks and Their Importance

• Communication is as vital as air, water, food, and shelter
• Networks connect us like never before
• Global communities foster social interaction regardless of location or time zone
• Communication via the internet promotes global community creation

Host Roles in a Network

• Every computer on a network is a host, end device, or endpoint
• An IP address identifies a host and its network

Common server types and their functions:

• Email Server: Runs email server software, clients need client software to access email
• Web Server: Runs web server software, clients use browsers to access web pages
• File Server: Stores corporate and user files, which clients can access

Peer-to-Peer Networks

• In peer-to-peer networks, a device can function as both a client and a server
• Suited for small networks
• Computers serve as both servers and clients
• Easy to set up, less complex, and lower cost, only suited to simple tasks
• Lacks centralized administration, security, and scalability, plus, slower performance

End Devices

• An end device is where a message originates or is received
• Data starts and ends with an end device, flowing through the network in between

Intermediary Network Devices

• Intermediary devices connect multiple end devices to form an internetwork
• Examples include switches, wireless access points, routers, and firewalls

These devices manage data flow by:

• Regenerating and retransmitting communication signals
• Maintaining pathway information through networks
• Notifying devices of errors
• Directing data along alternate paths during link failures
• Classifying and prioritizing messages
• Permitting/denying data flow based on security settings

Network Media

• Networks use a medium, to carry messages from source to destination
• The choice of media depends on many factors
• Copper cables use electrical impulses
• Fiber optic cables use pulses of light
• Wireless transmission uses modulation of specific electromagnetic wave frequencies

Network Representations

• Network diagrams (topology diagrams) use symbols to represent network devices
• Recognizing logical representations of physical components helps visualize network organization
• Important terms include Network Interface Card (NIC), Physical Port, and Interface
• Physical topology diagrams show physical location of cables and intermediary devices
• Logical topology diagrams show ports, devices, and addressing schemes

Network Types by Size

• Small Home Networks: Connect a few computers to each other and the internet
• Small Office/Home Office: Connect computers within a home or remote office to a corporate network
• Medium to Large Networks: Multiple locations with hundreds/thousands of interconnected computers
• World Wide Networks: Connects hundreds of millions of computers worldwide, such as the internet

LANs and WANs

• LANs interconnect end devices in a limited area and are managed by a single entity, and provide high speed bandwidth to internal devices
• WANs interconnect LANs over wide areas, managed by service providers, and have slower speeds

The Internet

• The internet is a worldwide interconnected network of LANs and WANs
• Uses copper wires, fiber optic cables, and wireless transmissions
• No single entity owns the internet

Intranets and Extranets

• Intranets are private collections of LANs/WANs within an organization
• Access to it is limited to authorized members
• Extranets let external entities access an organization's network securely, like individuals that require access to data

Home and Small Office Connections

• Connection choice relies greatly on location and provider availability
• Cable provides always-on, high-bandwidth internet via cable television infrastructure
• DSL provides always-on, high-bandwidth internet over telephone lines
• Cellular connections use cell phone networks
• Satellite connections benefit rural areas without cable/DSL providers
• Dial-up telephone is a low bandwidth option using a modem

Business Internet Connections

• Businesses require options differing from home use, higher bandwidth, dedicated bandwidth, and managed services
• Dedicated Leased Lines: Reserved circuits that connect distant offices with private voice data networking
• Ethernet WAN: Extends LAN access technology into the WAN
• DSL is available in Symmetric Digital Subscriber Lines (SDSL) formats
• Satellite can provide a connection when a wired solution is not available.

Converged Networks

• Previously, organizations used separate cabling for phone, video, and data networks
• Each network used different technologies
• Converged networks carry multiple services over a single link and can deliver data, voice, and video using a unified infrastructure with shared standards

Network Architecture Characteristics

• Fault Tolerance: Limit impact of failure to affected devices
• Scalability: The network can expand quickly and easily to facilitate new users and applications without impacting the performance of services to exiting users
• Quality of Service: Ensures prioritization for live video and voice and other transmissions that required it
• Security: Protection of the network and its data

Fault Tolerance

• Limits the impact of failures to affected devices
• Requires multiple paths for fault tolerance
• Packet switching splits traffic into packets routed over the network

Scalability

• A scalable network can expand quickly and easily to support new users and applications without impacting the performance of services to existing users
• Network designers follow accepted standards and protocols in order to make the networks scalable.

Quality of Service (QoS)

• Quality of Service (QoS) ensures reliable content delivery for all users
• Congestion happens when demand exceeds available bandwidth
• A QoS policy enables easier management of the flow of data and voice traffic

Network Security

• Includes physical protection of devices and prevention of unauthorized access
• Necessary to protect transmitted data

Three goals of network security:

• Confidentiality: Data is only read by intended recipients
• Integrity: Assurance that data isn't altered during transmission
• Availability: Reliable, timely access to data for authorized users

Bring Your Own Device (BYOD)

• Allows people to use their own devices, increasing flexibility
• BYOD allows end users to have the freedom to use personal tools to access information and communicate using their Laptops, Netbooks, Tablets, Smartphones, and E-readers.
• BYOD is any device, with any ownership, used anywhere.

Online Collaboration and Video Communication

• Collaboration tools like Cisco WebEx enable instant connection/interaction
• Vital to businesses and education
• Cisco Webex Teams: Send messages, post images/videos
• Video calls can be made to any location
• Video conferencing is powerful communication tool
• Critical for effective collaboration
• Cisco Telepresence powers is one way of working where everyone, everywhere

Cloud Computing

• Allows storing personal files or backing up data on remote servers
• Accessible applications
• Enables businesses to deliver content to any device globally

Four Cloud Types:

• Public Clouds: Available to the general public, often through a pay-per-use model or free of charge
• Private Clouds: Dedicated to a specific organization or entity, like government agencies
• Hybrid Clouds: Combine two or more cloud types (e.g., custom and public) while remaining distinct entities connected by the same architecture
• Custom Clouds: Tailored to meet the needs of industries like healthcare or media and can be private or public

Technology Trends in the Home

• Smart home technology integrates technology into appliances for interconnectivity

Powerline Networking

• Connects devices to a LAN using electrical outlets where data cables aren't available
• Uses a standard powerline adapter, sending data on specific frequencies

Wireless Broadband

• Connects homes or small businesses to the internet
• Employs cellular technology, like smartphones

Security Threats

• Integral part of networking
• Implementation should balance data security and expected quality of service
• May be external or internal

External Threats

• Viruses, worms, and Trojan horses
• Spyware and adware
• Zero-day attacks
• Threat Actor attacks
• Denial of service attacks
• Data interception and theft
• Identity theft

Internal Threats

• Lost or stolen devices
• Accidental misuse by employees
• Malicious employees

Security Solutions

• Effective security uses multiple layers
• Network security for small networks includes Antivirus and antispyware software and Firewall filtering.
• Larger networks use:
  • Dedicated firewall systems
  • Access control lists (ACL)
  • Intrusion prevention systems (IPS)
  • Virtual private networks (VPN)