Understanding Computer Networks

Learning Objectives

• Computer networks and their purpose are defined
• Several uses for networks have been described
• The various characteristics of a network, such as topology, architecture, and size, are easily understood
• Characteristics about data and how it travels over a network were understood
• Specific types of wired and wireless networking media and how they transmit data are named
• Common communications protocols and networking standards used with networks today can be identified
• Types of networking hardware and their purpose have been listed

What is a Network?

• A network is a connected system of objects or people
• A computer network is a collection of computers and other hardware devices connected together
• Users can share hardware, software, and data, and electronically communicate through computer networks
• Networks range from small private networks to the Internet
• Networking is essential in most businesses

Networking Applications

• Includes the following services:
  • The Internet
  • Telephone service
  • Television and radio broadcasting
  • Global positioning system (GPS)
  • Monitoring Systems
  • Multimedia Networking
  • Videoconferencing
  • Collaborative Computing
  • Telecommuting
  • Telemedicine

The Internet and Telephone Service

• The Internet is the largest computer network.
• Mobile phones use a wireless network for communications
• Cellular phones need to be within range of a cell tower to function
• Dual-mode phones can send and receive voice and data using two different cellular radio standards, often GSM and CDMA radios
• Satellite phones use satellite technology and are often used by soldiers, journalists, wilderness guides, and researchers

Broadcasting and GPS Applications

• TV and radio content is still delivered over the air
• Cable TV networks and satellite TV networks are also included
• The Global Positioning System (GPS) uses 24 GPS satellites for location and navigational purposes
• GPS receivers determine their exact geographic location
• GPS III was launched in December 2018 and is more powerful and accurate than current systems

GPS Applications

• Individuals can use GPS for hiking, driving directions, maps, work data, Web searches, and social media
• Workers use GPS for location information, guide vehicles and equipment, and emergency services
• The military uses GPS to guide munitions and trucks and to track military aircraft, ships, and submarines

Monitoring Systems

• Networking technology is used in monitoring systems to define location or status of an object
• RFID-based systems monitor the status of objects
• GPS-based monitoring systems monitor the physical location of objects with child and vehicle monitoring systems
• Electronic medical monitors provide home healthcare
• Sensor systems are used for shipping, home automation (smart thermostats), etc.

Multimedia Networking

• Digital multimedia content is distributed through a home network
• This includes smart TVs, streaming media players, etc.
• Placeshifting allows individuals to view multimedia content at a convenient location (i.e., Slingbox)

Videoconferencing, Collaborative Computing, and Telecommuting

• Videoconferencing uses computers, video cameras, microphones, and networking technologies to conduct face-to-face meetings
• Telepresence videoconferencing mimics a real-time meeting environment
• Collaborative computing enables individuals to work together on documents and projects
• This includes markup tools, collaboration software, shared documents, etc.
• Those who telecommute work from a remote location (usually home)
• Communicate with their places of business and clients using networking technologies allows flexibility

Telemedicine

• Networking technology provides medical information and services
• This includes remote monitoring and consultations
• Remote diagnosis
• Provides individuals in rural locations access to medical care
• Telesurgery involves robot-assisted surgery where the doctor's physical location differs from the patient and robot location

Network Characteristics: Wired vs Wireless Networks

• In wired networks, computers and other devices are physically connected to the network with cables
• This is typically in schools, businesses, and government facilities
• In wireless networks, computers and other devices connect to the network with radio wave signals, without physical cables
• These are typically in homes, schools, and businesses
• A public wireless hotspot provides wireless Internet access

Network Topologies

• The physical topology of a network indicates how the devices are arranged
• Star network topology connects all network devices to a central device which will cause the network to fail if it fails
• Bus network topology connects all network devices to a central cable
• Ring topology connects all computers via a cable that loops in a ring or circle
• Networks won't work if a ring topology is a circle because it has no start and no end
• Mesh networks connect devices so that messages can take any of several possible paths

Identifying Network Topologies: Bus Topologies

• A bus topology uses one cable as a main trunk to connect all the systems together
• A bus topology is easy to set up and requires no additional hardware, such as a hub
• A bus network is easy to implement but can be unreliable since the entire bus fails if there is a break in the wire

Identifying Network Topologies: Star Topologies

• Star topology connects all computers through one central device known as a hub or a switch
• A major benefit of a star topology is that a break in the cable affects only the workstation connected to the cable, not the entire network
• If the hub fails in a star topology, the entire network goes down
• Star topologies are popular in today's networking environments

Identifying Network Topologies: Mesh Topologies

• Ring topology connects all computers via a cable that loops in a ring or circle
• A ring topology is a circle that has no start and no end.
• If one computer failed or the cable link was broken, the entire network could go down

Identifying Network Topologies: Mesh Topologies

• A mesh topology is not very common in computer networking today
• In a mesh topology, every workstation is connected to every other component of the network

Identifying Network Topologies: Mesh Topologies - Advantages

• Includes fault tolerance so it is almost impossible for the network to go down due to a cable fault

Identifying Network Topologies: Mesh Topologies - Disadvantages

• This topology is expensive because of the additional cabling and network interfaces to create the multiple pathways between each system
• It is hard to administer and manage because of the numerous connections

Client-Server Networks

• The client is a computer or other device on the network that requests and utilizes network resources
• The server is the computer dedicated to processing client requests

Network Size and Coverage Area

• Personal Area Networks (PANs) connect an individual's personal devices that must be physically located close together
• Local Area Networks (LANs) connect devices located in a small geographic area
• Metropolitan Area Networks (MANs) cover areas such as a city or county
• Wide Area Networks (WANs) cover a large geographic area, such as the internet

Intranets, Extranets, and Virtual Private Networks (VPNs)

• Intranets are private networks only for an organization's employees which are set up like the Internet
• Extranets are company networks accessible to authorized outsiders
• Virtual Private Networks (VPN) provide a private, secure path over the Internet
• VPNs use tunneling and special encryption technology
• Without a VPN, passwords and credit card numbers sent via a hotspot can be intercepted