Network Types and Local Networks

Network Types

• The internet is an everyday feature and often taken for granted
• The internet is viewed as a collection of connections for finding and sharing info
• The internet is a global network of interconnected networks, not owned by one group or individual
• Networks cooperate to exchange info using common standards

Local Networks

• Small home networks connect devices to each other and the internet
• SOHO (small office/home office) networks allow remote offices to connect to corporate networks
• Medium to large networks commonly have hundreds or thousands of interconnected hosts.
• The internet connects hundreds of millions of computers globally

Mobile Devices

• Smart phones combine features of telephones, cameras, GPS, media players, and touch screen computers
• Tablets feature on-screen keyboards for composing emails and browsing the web
• Smartwatches can connect to smartphones for alerts, messages, and health tracking
• Wearable computers like Google Glass show info similarly to a Head-Up Display (HUD)

Connected Home Devices

• Connected home security systems allow remote monitoring and configuration of lighting and climate
• Household appliances like refrigerators, ovens and dishwashers can connect to the internet
• Smart TVs connect to the internet for content without needing traditional TV service provider equipment
• Gaming consoles connect to the internet for downloads and online play

Other Connected Devices

• Smart Cars connect to the internet for maps, audio/video, or destination information
• Radio frequency identification (RFIDs) tags can be used to track objects
• Sensors provide data on temperature, humidity, wind speed, barometric pressure, and soil moisture.
• Actuators can be automatically triggered based on current conditions
• Medical devices like pacemakers and hospital monitors alert users/professionals to vital signs

Data Transmission and Personal Data

• Volunteered data is created and shared by individuals, like social network profiles including media files
• Observed data is captured through recording actions of individuals, like cell phone location data
• Inferred data, like a credit score, is based on analysis of volunteered or observed data

The Bit

• Computers and networks work with binary digits, zeros and ones
• Each bit has a value of 0 or 1
• A bit is the smallest piece of data
• Eight bits form a byte
• The American Standard Code for Information Interchange (ASCII) represents characters with eight bits

Data Transmission Methods

• Data is converted into signals to be sent across the network
• Media refers to the physical path for signal transmission
• Copper wire, fiber-optic cable, and electromagnetic waves are examples of transmission media
• Electrical signals are electrical pulses on copper wire
• Optical signals convert electrical signals into light pulses
• Wireless signals use infrared, microwave, or radio waves

Bandwidth

• Bandwidth is the capacity of a medium to carry data measured in bits per second

• Bits per second (bps) is the fundamental unit of bandwidth

• Other units:

  • Kilobyte (kbps): Thousands of bits per second = 1,000 bps = 103 bps
  • Megabyte (Mbps): Millions of bits per second = 1,000,000 bps = 106 bps
  • Gigabyte (Gbps): Billions of bits per second = 1,000,000,000 bps = 109 bps
  • Terabyte (Tbps): Trillions of bits per second = 1,000,000,000,000 bps = 1012 bps

Throughput

• Throughput measures the transfer of bits across media over time
• Throughput usually does not match specified bandwidth
• Factors influencing throughput include:
  • Amount of data sent and received
  • Types of data transmitted
  • Latency from network devices between source and destination
• Latency is the time it takes for data to travel from one point to another, including delays

Clients and Servers

• Clients are hosts with software to request and display information from the server

• Servers are hosts with software to provide information to other hosts

• Examples:

  • Email servers run email server software accessed by clients with mail client software
  • Web servers run web server software accessed by clients with browser software
  • File servers store files centrally, accessed by clients with file explorer software

Peer-to-Peer Networks

• In peer-to-peer (P2P) networks, computers function as both servers and clients
• The simplest P2P network consists of two directly connected computers
• Advantages of P2P are easy setup, less complexity, lower cost, simple file and printer sharing
• Disadvantages of P2P are no central administration, lower security, non-scalability and potential slowdowns as devices operate as client and server
• P2P applications let a device act as both client/server, requiring a user interface and background service

Multiple Roles in the Network

• A single computer can provide simultaneous services, and also run multiple types of server software
• Computers can act as file servers, web servers, and email servers

Network Infrastructure

• Network infrastructure consists of three hardware categories:
  • End devices
  • Intermediate devices
  • Network media

End Devices

• End devices are the most familiar network devices
• End devices form the interface between users and the network
• Examples are computers, network printers, telephones, teleconferencing equipment, security cameras and mobile devices