Network Types and Mobile Devices

Network Types

• The internet has been integrated into everyday life
• People often view the internet as a collection of connections for finding or sharing information
• The internet is not owned by anyone
• It is a global collection of interconnected networks that use common standards to exchange information

Local Networks

• Small home networks connect computers to each other and to the internet
• SOHO (Small Office/Home Office) networks allow computers in a home or remote office to connect to a corporate network
• Medium to large networks used by corporations and schools can have hundreds or thousands of hosts
• The internet is a network that connects millions of computers worldwide

Mobile Devices

• Smartphones combine the functions of a telephone, camera, GPS, media player, and touchscreen computer
• Tablets offer on-screen keyboards for tasks previously done on laptops, like composing emails
• Smartwatches alert users with messages and offer functions such as heart rate monitoring
• Wearable computers, like Google Glass, present a Heads-Up Display (HUD) similarly to fighter pilot technology

Connected Home Devices

• Connected security systems enable remote monitoring and configuration of lighting and climate controls using a mobile device
• Household appliances, including refrigerators, ovens, and dishwashers, can connect to the internet
• Smart TVs can access internet content without extra TV service provider equipment
• Gaming consoles connect to the internet to download games and play with friends

Other Connected Devices

• Smart Cars can connect to the internet for maps, audio, video, or destination information
• Radio Frequency Identification (RFIDs) tags are used to track and monitor sensor data for many conditions
• Connected sensors can provide temperature, humidity, wind speed, barometric pressure, and soil moisture data
• Medical devices like pacemakers and insulin pumps offer direct feedback or alerts about vital signs

Data Transmission

• Personal data is classified into types
• Volunteered data is created and shared by individuals, such as social network profiles that include video, images, text and audio
• Observed data is captured by recording individual actions such as cell phone location data
• Inferred Data is data based on volunteered and observed data such as credit scores

The Bit

• Computers and networks operate using binary digits of 0 and 1
• A bit, short for "binary digit", is the smallest unit of data
• Computers interpret patterns of bits, while people interpret words and pictures
• A byte consists of eight bits which represents letters and numbers
• The American Standard Code for Information Interchange (ASCII) represents characters with eight bits
• Capital letter A = 01000001
• Number 9 = 00111001
• Special Character # = 00100011

Common Methods of Data Transmission

• Signals must be converted for transmission across the network
• Media refers to the physical medium that signals are sent across such as copper wire, fiber optic cable, and radio waves
• Electrical signals use 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 for carrying data which is measured in bits per second
• Bits per second (bps): 1 bps is the basic bandwidth unit
• Kilobyte (kbps): 1 kbps is 1,000 bps or 10^3 bps
• Megabyte (Mbps): 1 Mbps is 1,000,000 bps or 10^6 bps
• Gigabyte (Gbps): 1 Gbps is 1,000,000,000 bps or 10^9 bps
• Terabyte (Tbps): 1 Tbps is 1,000,000,000,000 bps or 10^12 bps

Throughput

• Throughput measures the rate of bit transfer across media
• Throughput usually differs from bandwidth
• Factors influencing throughput
• Amount of data sent and received
• Types of data being transmitted
• Latency from network devices between source and destination
• Latency includes the time data travels from one point to another

Clients and Servers

• Clients are computer hosts with software to request information from servers
• Servers are hosts with software to provide information to other network hosts
• Email servers run software for email service and clients use mail client software
• Web servers run web server software and clients use Windows Internet Explorer

Peer-to-Peer Networks

• Peer-to-peer (P2P) networks include computers that function as both servers and clients
• The simplest P2P network is two directly connected computers Advantages of P2P:
• Easy to set up
• Simple network
• Low cost as dedicated servers are not needed
• Used for simple tasks such as file sharing and printer access Disadvantages of P2P:
• No central administration
• Not as secure
• Not scalable
• Performance slows down as all devices act as both clients and servers

Peer-to-Peer Applications

• P2P applications allow a device to act as both client and server in the same communication
• Each client is a server and each server is a client
• P2P applications require a user interface and a background service
• Clients can send and receive messages simultaneously

Multiple Roles in the Network

• A computer can provide server software for many clients simultaneously
• A single computer can also run multiple types of server software
• In small businesses, a computer can serve a multiple purposes like a file server, web server, and email server

Network Infrastructure

• Network infrastructure has three components: end devices, intermediate devices, and network media

End Devices

• End devices (or hosts) provide an interface between users and the communication network
• Examples of end devices are:
• Workstations and laptops
• File and web servers
• Network printers
• Telephones and teleconferencing
• Security cameras
• Smartphones and tablets
• PDAs
• Wireless debit/credit card readers
• Barcode scanners