Understanding Network Types and the Internet

Network Types

• The internet is so integrated into daily life that it's often taken for granted
• When people talk about "the internet," they are usually referring to a concept of interconnectedness rather than physical connections

Who Owns “The Internet?”

• The internet is not owned by any single entity
• It is a global network of interconnected networks that cooperate using common standards for information exchange

Local Networks

• Small home networks link a few computers to each other and the internet
• SOHO (small office/home office) networks let computers in a home or remote office connect to a corporate network to access shared resources

Local Networks (Cont.)

• Medium to large networks, like those in corporations and schools, can span multiple locations with numerous interconnected hosts
• The internet connects hundreds of millions of computers globally

Mobile Devices

• Smartphones combine telephone, camera, GPS, media player, and touchscreen functionalities
• Tablets have on-screen keyboards and allow users to perform tasks similar to those on laptops, like composing emails or browsing

Mobile Devices (Cont.)

• Smartwatches can connect to a smartphone for alerts, messages, heart rate monitoring, and step counting
• Wearable computers like Google Glass display information similar to a fighter pilot's Head-Up Display (HUD)

Connected Home Devices

• Connected security systems enable users to remotely monitor and configure home items like lighting and climate via mobile devices
• Household appliances such as refrigerators, ovens, and dishwashers can be connected to the internet

Connected Home Devices (Cont.)

• Smart TVs can connect to the internet for content without needing traditional TV service provider equipment
• Gaming consoles can connect to the internet to download games and play with friends online

Other Connected Devices

• Modern cars, called Smart Cars, connect to the internet for maps, audio, video, and destination information
• Radio Frequency Identification (RFID) tags are placed on objects to track them or monitor sensor data

Other Connected Devices (Cont.)

• Connected sensors can provide data on temperature, humidity, wind speed, barometric pressure, and soil moisture, while actuator can be automatically triggered based on current conditions
• Medical devices, including pacemakers, insulin pumps, and hospital monitors, offer medical professionals direct feedback or alerts based on a patient's vital signs

Types of Personal Data

• Volunteered data includes information that is actively shared by individuals, such as social network profiles, videos, pictures and audio files
• Observed data is captured through tracking individuals’ actions, like location data from cell phones
• Inferred data includes information like credit scores, which derived from analysis of volunteered or observed data

The Bit

• Computers and networks operate using binary digits: zeros and ones
• A bit, short for "binary digit," is the smallest unit of data, either 0 or 1
• Computers interpret patterns of bits, while humans interpret words and pictures
• A byte is a group of eight bits, used to represent letters, numbers, and symbols
• ASCII (American Standard Code for Information Interchange) represents each character with eight bits

Common Methods of Data Transmission

• Data must be converted into signals to be sent across the network media
• Media is the physical channel for transmitting signals, examples include copper wire, fiber optic cable, and electromagnetic waves
• A signal is made of electrical or optical patterns transmitted between connected devices
• Electrical signals transmit data as electrical pulses over copper wire
• Optical signals convert electrical signals into light pulses for transmission
• Wireless signals use infrared, microwave, or radio waves to transmit data through the air

Bandwidth

• Bandwidth is the capacity of a medium to carry data, measured digitally as the amount of data that can flow from one place to another over a period of time; typically measured in bits per second
• Bits per second (bps) is the fundamental unit of bandwidth
• Kilobyte (kbps): 1 kbps = 1,000 bps or 10^3 bps
• Megabyte (Mbps): 1 Mbps = 1,000,000 bps or 10^6 bps
• Gigabyte (Gbps): 1 Gbps = 1,000,000,000 bps or 10^9 bps
• Terabyte (Tbps): 1 Tbps = 1,000,000,000,000 bps or 10^12 bps

Throughput

• Throughput measures the actual transfer rate of bits across a medium which may be influenced by factors
• Influencing factors include the amount and types of data transmitted
• The impact of latency is determined by the number of 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 Server Roles

• Clients are computer hosts with software enabling them to request and display information from a server
• Servers are hosts with software that enables them to provide information, like email or web pages, to other hosts on the network
• Email servers run email software, with clients using mail client software like Microsoft Outlook to access email on the email server
• Web servers run web server software, with clients using browser software like Windows Internet Explorer to access web pages
• File servers store corporate and user files in a central location, accessed by client devices using client software like Windows File Explorer

Peer-to-Peer Networks

• In small businesses and homes, computers can function as both servers and clients
• This is called a peer-to-peer (P2P) network
• A basic P2P network links two computers directly, either with a wired or wireless connection

Advantages of P2P

• P2P networks are easy to set up and are less complex than other networks
• P2P networks have lower costs because network devices and dedicated servers may not be required
• P2P networks can be used for tasks such as transferring files and sharing printers

Disadvantages of P2P

• P2P networks lack central administration and are less secure and not scalable
• In P2P networks all devices can act as both clients and servers which can slow their performance

Peer-to-Peer Applications

• A P2P application enables a device to function as both client and server in the same communication
• In this model, every client is a server and every server is a client
• P2P applications require a user interface and a background service on each end device
• With P2P both clients can send and receive messages simultaneously

Multiple Roles in the Network

• A single computer with server software can provide services to one or many clients simultaneously
• Additionally, a single computer can run multiple types of server software
• A home or small business may have one computer acting as a file server, a web server, and an email server

Network Infrastructure

• Network infrastructure contains three categories of hardware components
  • End devices
  • Intermediate devices
  • Network media

End Devices

• End devices, or hosts, are the network devices people use most often
• End devices form the interface between users and the underlying communication network
• Examples of end devices
  • Computers (workstations, laptops, file servers, web servers)
  • Network printers
  • Telephone's and teleconferencing equipment
  • Security cameras
  • Mobile devices (such as smart phones, tablets, PDAs, and wireless debit/credit card readers and barcode scanners)