Ch. 8 Intro to Data Processing (Communications & Networks)

Star Network

Each device is connected directly to a central network switch. Whenever a node sends a message, it is routed to the switch, which then passes the message along to the intended recipient. The star network is the most widely used network topology today.

Tree Network

Each device is connected to a central node, either directly or through one or more other devices. This network, also known as a hierarchical network, is often used to share corporate-wide data.

Bus Network

Each device is connected to a common cable called a bus or backbone, and all communications travel along this bus.

Ring Network

Each device is connected to two other devices, forming a ring. When a message is sent, it is passed around the ring until it reaches the intended destination.

Communication Systems

Electronic systems that transmit data from one location to another. Whether wired or wireless, every communication system has four basic elements.

Wireless Access Point

The receiver interprets incoming radio frequencies from a wireless LAN and routes communications to the appropriate devices, which could be separate computers, a shared printer, or a modem. Also known as "Base Station"

Protocols

The rules for exchanging data between computers. For data transmission to be successful, sending and receiving devices must follow a set of communication rules for the exchange of information. Involves: (1) identifying sending and receiving devices. (2) breaking information into small parts, or packets, for transmission across the Internet.

IP Address

The unique numeric address of a computer on the Internet. The Internet uses IP addresses to deliver e-mail and to locate websites. Because these numeric addresses are difficult for people to remember and use, a system was developed to automatically convert text-based addresses to numeric IP addresses called DNS.

Mesh Network

This topology is the newest type and does not use a specific physical layout (such as a star or a tree). Rather, the mesh network requires that each node have more than one connection to the other nodes The resulting pattern forms the appearance of a mesh. If a path between two nodes is somehow disrupted, data can be automatically rerouted around the failure using another path. Wireless technologies are frequently used to build mesh networks.

Network Security

Three technologies commonly used to ensure network security are: (1.) firewalls (2.) intrusion detection systems (3.) virtual private networks

Fiber Optic Cable

Transmits data as pulses of light through tiny tubes of glass. The data transmission speeds of fiber-optic cables are incredible; recently speeds of 1 petabit per second were measured (a petabit is 1 million gigabits). Compared to coaxial cable, it is lighter, faster, and more reliable at transmitting data. Today, fiber-optic cable is rapidly replacing twisted-pair cable telephone lines.

Modem Transfer Rate

Typically measured in millions of bits (megabits) per second (Mbps) The higher the speed, the faster you can send and receive information.

Physical Connections

Use a solid medium to connect sending and receiving devices. These connections include: (cables) 1. twisted-pair 2. coaxial 3. fiber-optic

Client/Server Networks

Use central servers to coordinate and supply services to other nodes on the network. The server provides access to resources such as web pages, databases, application software, and hardware. This strategy is based on specialization. Server nodes coordinate and supply specialized services, and client nodes request the services. Commonly used server operating systems are Windows Server, Mac OS X Server, Linux, and Solaris.

WiFi (Wireless Fidelity)

Uses high-frequency radio signals to transmit data. A number of standards for Wi-Fi exist, and each can send and receive data at a different speed. Most home and business wireless networks use Wi-Fi.

Microwave

Uses high-frequency radio waves. It is sometimes referred to as line-of-sight communication because microwaves can only travel in a straight line. Because the waves cannot bend with the curvature of the earth, they can be transmitted only over relatively short distances. Thus, microwave is a good medium for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of microwave stations with microwave dishes or antennas.

Cellular

Uses multiple antennae (cell towers) to send and receive data within relatively small geographic regions (cells). Most cell phones and mobile devices use cellular networks.

WLAN (Wireless LAN)

Uses radio frequencies to connect computers and other devices. All communications pass through the network's centrally located wireless access point or base station.

GPS (Global Positioning System)

Uses satellite information to uniquely determine the geographic location of a device.

Satellite

Uses satellites orbiting about 22,000 miles above the earth as microwave relay stations. Many of these are offered by Intelsat, the International Telecommunications Satellite Consortium, which is owned by 114 governments and forms a worldwide communication system. Satellites orbit at a precise point and speed above the earth. They can amplify and relay microwave signals from one transmitter on the ground to another. Satellites can be used to send and receive large volumes of data (known as uplink and downlink)

Types of Modems

1. DSL - uses standard phone lines to create a high-speed connection, using USB or Ethernet port 2. Cable - uses the same coaxial cable as your television to create a high-speed connection using the system unit's USB or Ethernet port 3. Wireless - almost all computers today have built-in wireless modems. For those that do not, wireless adapter cards are available that plug into USB or special card ports.

Four Basic Elements of Communication Systems

1. Sending and receiving devices 2. Connection devices. 3. Data transmission specifications. 4. Communication channel

Router

A Node that forwards or routes data packets from one network to their destination in another network.

Client

A Node that requests and uses resources available from other nodes. Typically, a client is a user's personal computer.

Server

A Node that shares resources with other nodes. Dedicated servers specialize in performing specific tasks. Depending on the specific task, they may be called an application server, communication server, database server, file server, printer server, or web server.

Host

Any computer system connected to a network that provides access to its resources.

Node

Any device that is connected to a network. It could be a computer, printer, or data storage device.

Packets

Before a message is sent on the Internet, it is broken down into small parts called packets. Each packet is then sent separately over the Internet. At the receiving end, the packets are reassembled into the correct order.

Switch

Central Node that coordinates the flow of data by sending messages directly between sender and receiver nodes. A hub previously filled this purpose by sending a received message to all connected nodes, rather than just the intended node.

Communication Channels

Channels that physically 'carry' the data from one computer to another. There are 2 types of channels: physical connection or cable (wired/ethernet), or wireless (wifi).

Proxy Server

Computer that acts as a gateway or checkpoint in an organization's firewall. Security hardware and software; All communications into and out of an organization pass through a special security computer, called a proxy server, to protect all systems against external threats.

Firewall

Consists of hardware and software that control access to a company's intranet and other internal networks. Most use software or a special computer called a proxy server.

Twisted Pair Cable

Consists of pairs of copper wire that are twisted together. Both standard telephone lines and Ethernet cables use twisted pair.

Network Operating Systems

Control and coordinate the activities of all computers and other devices on a network. These activities include electronic communication and the sharing of information and resources.

DNS (domain name server)

Converts text-based addresses to IP addresses. For example, whenever you enter a URL, say www.mhhe.com, a DNS converts this to an IP address before a connection can be made.

Virtual Private Network (VPN)

Creates a secure private connection between a remote user and an organization's internal network. Special VPN protocols create the equivalent of a dedicated line between a user's home or laptop computer and a company server. The connection is heavily encrypted, and, from the perspective of the user, it appears that the workstation is actually located on the corporate network.

Network Strategies

Define how information and resources are shared. Every network has a strategy, or way of coordinating the sharing of information and resources. Two of the most common network strategies are: (1.) client/server (2.) peer-to-peer.

Network Architecture

Describes how a network is arranged and how resources are coordinated and shared. It encompasses a variety of different network specifics, including network topologies and strategies.

Network Topology

Describes the physical arrangement of the network. Common topologies are: Bus network Ring network

Computer Network

A communication system that connects two or more computers so that they can exchange information and share resources. A network may consist only of personal computers, or it may integrate personal computers or other devices with larger computers. Networks can be controlled by all nodes working together equally or by specialized nodes coordinating and supplying all resources. Networks may be simple or complex, self-contained or dispersed over a large geographic area.

Network Administrator

A computer specialist responsible for efficient network operations and implementation of new networks.

Coaxial Cable

A high-frequency transmission cable, replaces the multiple wires of telephone lines with a single solid-copper core. In terms of the number of telephone connections, a coaxial cable has over 80 times the transmission capacity of twisted pair. Coaxial cable is used to deliver television signals as well as to connect computers in a network.

Bandwidth

A measurement of the width or capacity of the communication channel. Effectively, it means how much information can move across the communication channel in a given amount of time.

WiMax

A new standard that extends the range of Wi-Fi networks using microwave connections. WiMax is commonly used by universities and others to extend the capability of existing Wi-Fi networks. (WiMax = Worldwide Interoperability for Microwave Access)

Bluetooth

A short-range radio communication standard that transmits data over short distances of up to approximately 33 feet. Bluetooth widely used for wireless headsets, printer connections, and handheld devices.

Directory Server

A specialized server that manages resources, such as user accounts, for an entire network.

Wireless Connections

Moves data through the air, does not use a solid substance to connect devices. Most wireless connections use radio waves to communicate, such as smartphones. Primary technologies used for wireless connections are Bluetooth, Wi-Fi, microwave, WiMax, cellular, and satellite connections.

LAN (Local Area Network)

Networks with nodes that are in close physical proximity—within the same building, for instance. Typically, LANs span distances less than a mile and are owned and operated by individual organizations. LANs are widely used by colleges, universities, and other types of organizations to link personal computers and to share printers and other resources.

Peer-to-Peer Networks

Nodes have equal authority and can act as both clients and servers. The most common way to share games, movies, and music over the Internet is to use a P2P network. For example, special file-sharing software such as BitTorrent can be used to obtain files located on another personal computer and also can provide files to other personal computers.

Modems

Short for "modulator-demodulator." Modulator - converting from digital --> analog Demodulator - converting from analog --> digital The modem enables digital personal computers to communicate across different media, including telephone wires, cable lines, and radio waves.

Intrusion Detection System (IDS)

Works with firewalls to protect an organization's network. These systems use sophisticated statistical techniques to analyze all incoming and outgoing network traffic. Using advanced pattern matching and heuristics, an IDS can recognize signs of a network attack and disable access before an intruder can do damage.