Network Types and Data Transmission

Module 1: Communications in a Connected World

1.1 Network Types

• The internet has become a part of everyday life with people taking it for granted
• The internet is a formless collection of connections where people find or share information
• The internet is not owned by any individual or group
• The internet consists of interconnected networks cooperating to exchange information using common standards
• Small home networks connect a few home computers to each other and to the Internet.
• SOHO networks allow computers in a home or remote office to connect to a corporate network and shared resources
• Medium to large networks used by corporations and schools have hundreds or thousands of hosts across many locations

1.2 Data Transmission

• Smart phones combine multiple functions like telephone, camera, GPS, media player and computer
• Tablets feature on-screen keyboards, so users can perform many activities previously done on laptops like email and web browsing
• Smartwatches providing alerts, messages, heart rate monitoring, and step counting
• Wearable computers, like Google Glass, project information on a tiny screen
• Connected home security systems enable remote monitoring and configuration of lighting, climate, and other home systems
• Household appliances like refrigerators, ovens, and dishwashers are becoming connected to the internet
• Smart TVs connect directly to the internet for content, eliminating the need for traditional TV service providers
• Gaming consoles can connect to the internet for game downloads and online play
• Modern "Smart Cars" can access maps, audio, video, and destination information
• Radio Frequency Identification (RFID) tags can be placed to track objects and monitor sensors.
• Connected sensors provide data on temperature, humidity, wind, pressure, and soil conditions that can trigger automatic responses
• Medical devices like pacemakers, insulin pumps, and hospital monitors give users and professionals direct feedback on vital signs

1.3 Data Transmission

• Volunteered data is explicitly shared such as on social networks, in the form of files, pictures, text and audio
• Observed data is captured through actions such as location when individuals are using cell phones
• Inferred data is based on the analysis of volunteered or observed data, an example being a credit score
• Computers work with binary digits of zeros and ones
• A bit is the abbreviation of "binary digit," and is smallest piece of data
• Humans interpret words and pictures while computers only interpret patterns of bits.
• One byte is 8 bits, which represent letters and numbers
• The American Standard Code for Information Interchange (ASCII) represents each character using eight bits

1.4 Common Methods of Data Transmission

• After data is transformed into bits, the bits are converted into signals that can be sent across a network
• Media refers to where the signals are transmitted and examples include copper wire, fiber-optic cable, and electromagnetic waves
• A signal consists of electrical or optical patterns transmitted from one connected device to another
• There are three main methods of signal transmission in networks
  • Electrical signals: transmission is achieved by representing data as electrical pulses on copper wire
  • Optical signals: transmission is achieved by converting the electrical signals into light pulse
  • Wireless signals: transmission is achieved by using infrared, microwave, or radio waves through the air

1.5 Bandwidth and Throughput

• Bandwidth is the capacity of a medium to carry data
• Digital bandwidth measures the amount of data that can flow from from one place to another in a given amount of time
• Bandwidth is measured in the number of bits that can be sent across the media in one second
  • Bits per second (bps) is the fundamental unit of bandwidth
  • 1 Kilobyte (kbps) = 1,000 bps or 103 bps
  • 1 Megabyte (Mbps) = 1,000,000 bps or 106 bps
  • 1 Gigabyte (Gbps) = 1,000,000,000 bps or 109 bps
  • 1 Terabyte (Tbps) = 1,000,000,000,000 bps or 1012 bps
• Throughput measures the transfer of bits across media over a time period
• Throughput does not usually match specified bandwidth and is influenced by the amount of data being sent and received, the types of data being transmitted, and the latency created by the number of network devices encountered
• Latency is the amount of time the data takes to travel between two points, including delays

1.6 Clients and Servers

• Clients are computer hosts with software installed that enables them to request and display data
• Servers are hosts with software enabling them to provide software to other hosts on the network
• Email servers run email software to provide email software for clients
• Web servers run web server software so clients use a web browser
• File servers centrally store files which client devices can then access through certain software
• In P2P networks, computers can function as both clients and servers
• The simplest P2P network consists of two directly connected computers using either a wired or wireless connection
• Advantages to P2P easy to set up, are less complex, lower costs as well as being used for simple tasks
• Disadvantages of P2P include no central administration, not being secure as other networks, not scalable and slow performance
• A P2P application allows a device to act as both a client and a server
• P2P applications require a user interface and a background service run on each end device so that each client is another server
• A single computer with server software can simultaneously provide services to one or multiple clients

1.7 Network Components

• The network infrastructure has three hardware components: End devices, Intermediate devices, Network media
• The network devices that people are most familiar with are called end devices/hosts which form the interface between users and the network
• Examples of end devices:
  • Computers ranging from workstations/laptops/file servers/web servers
  • Network printers
  • Telephones and teleconferencing equipment
  • Security cameras
  • Mobile devices such as smart phones, tablets, PDAs, and wireless debit/credit card readers and barcode scanners