Chapter 8: Local Area Networks Part 2

• Access Point
  • The interconnecting bridge between a wireless local area networks workstation and the wired local area network.
• Active Directory
  • Network directory structure for Window Server or operating system; a hierarchical structure that stores information about all the objects and resources on a network and makes this information available to users, network administrators, and application programs.
• Anti-Spam Software
  • Software designed to detect and block spam that has been sent to a computer.
• Anti-Spyware Software
  • Software designed to detect and remove malicious programs known as spyware.
• Antivirus Software
  • Software designed to detect and remove viruses that have infected a computer’s memory, disks, or operating system.
• Application Programming Interface, API
  • A software module that acts as an interface between application programs and technical entities, such as telephone switching system.
• Backup software
  • Software that allows network administrators to back up the data files currently stored on the network server’s hard drive.
• Basic Service Set, BSS
  • The transmission area surrounding a simple access point in a wireless local area network; it resembles a cell in a cellular telephone network.
• Bindery
  • A database that contains information on every resource connected to this one server, including users, groups of users and data sets.
• Carrier Sense Multiple Access with Collision Avoidance, CSMA/CA
  • A contention-based medium access control protocol for bus and star-wired bus local area networks in which a workstation wanting to transmit can only do so if the medium is idle; otherwise, it has to wait. Signal collisions are detected by transmitting workstation, which then backs off and retransmits.
• Corporate License
  • An agreement that allows a software package to be installed anywhere within a corporation, even if the installation involves multiple sites.
• Crash Protection Software
  • Software whose primary goal is to perform crash stalling; to try to keep the operating system running long enough to perform a graceful exit, on a workstation or network of workstations.
• Disk Mirroring
  • A technique used in RAID systems in which data is duplicated onto two drives simultaneously in order to provide a backup for the data.
• Domain
  • The primary unit of administration in all of the Windows network operating system.
• Extended Service Set, ESS
  • In wireless LAN topology, the collection of all the Basic Service Sets attached to the local area network through its access points.
• General Public License, GPL
  • A software license that allows the creator to distribute the software for free; recipients may alter the software as they wish, but must still give the altered software away for free.
• Hidden Workstation
  • A situation when two wireless devices can communicate to an access point but cannot “see” each other; two devices cannot intercommunicate by themselves.
• 11a
  • A wireless local area network protocol that is capable of supporting a theoretical transmission speed of 54 Mbps in the 5-GHz frequency range.
• 11b
  • An older wireless local area network protocol that is capable of supporting a theoretical transmission speed of 11 Mbps in the 2.4-GHz frequency range.
• IEEE 802.11g
  • A wireless local area network protocol that is capable of supporting a theoretical transmission speed of 54 Mbps in the 2.4-GHz frequency range.
• IEEE802 Suite of Protocols
  • A collection of protocols that define various types of local area networks, metropolitan area networks, and wireless networks. For example, the IEEE 802.3 protocol defines the protocol for CSMA/CD local area networks.
• Interactive User License
  • An agreement in which the number of concurrent active users of a particular software package is strictly controlled.
• Interframe space, IFS
  • The time in which a workstation waits before transmitting on a wireless local area network. There are typically three different interface spaces, depending upon the function to be performed.
• Internet Software
  • The tool set of network software to support Internet-related services that include Web browsers, server software, and Web page publishing software, among other applications.
• Leaf Objects
  • An object in a hierarchical directory structure that is composed of no further objects and includes entities such as users, peripherals, servers, printers, queues, and other network resources.
• Licensing Agreement
  • A legal contract that describes a number of conditions that must be upheld for proper use of the software package.
• Media Converters
  • Devices that convert cables and/or signals from one form to another.
• Multiple Input Multiple Output, MIMIO
  • A technology used in wireless LANs in which sending and receiving devices have multiple streams in an effort to send data faster with fewer errors.
• Multitasking Operating System, MOS
  • An operating system that schedules each task and allocates a small amount of time to the execution of each task.
• NetWare Directory Service, NDS
  • Now called directory, a database that maintains information on, and access to, every resource on the network, including users, groups of users, printers, data sets, and servers.
• Network Attached Storage, NAS
  • A computer system attached to a network that provides both network storage and the file system that controls the storage. Not the same as a storage area network.
• Network-Monitoring Software
  • Software designed to monitor a network and report usage statistics, outages, virus problems, and instructions.
• Network Operating System, NOS
  • A large, complex program that can manage all the resources that are commonly found on most local area networks, in addition to performing the standard functions of an operating system.
• Operating System
  • The program that is initially loaded into computer memory when the computer is turned on; it manages all the other programs, applications, and resources such as disk drives, memory, and peripheral devices in a computer.
• Organization Unit, OU
  • An object in a hierarchical tree structure for local area network operating system that is composed of further objects.
• Peer-to-Peer Network
  • Local area networks that may not have a server; most communication are from workstation to workstation.
• Redirection
  • The technique of moving data signal to an alternate path.
• Redundant Array of Independent Disks, RAID
  • Describes how the data is stored on multiple disk drives.
• Remote Access Software
  • Allows a person to access all of the possible functions of a personal computer workstation from a mobile or remote location.
• Security Assessment Software
  • Software designed to assess the security weaknesses, and strength, of a network.
• Server
  • A computer that stores the network software and shared or private user files.
• Server Appliance
  • A specialized network server, such as a server that is specifically designed for database systems or for Web serving.
• Server Virtualization
  • The process of making one computer, or server, act as if it were multiple computers, or servers, in order to isolate the operations of a server.
• Single-User-Multiple-Station License
  • An agreement that allows a person to install a copy of a software program on multiple computers, for example; on his or her home computer as well as his or her work computer.
• Single-User-Single-Station License
  • An agreement that allows a person to install a single copy of a software program on only one computer.
• Site License
  • An agreement that allows a company to install copies of a software program on all the machines at a single site.
• Sniffers
  • Software and hardware devices that can monitor a network to determine if there are invalid messages being transmitted, report network problems such as malfunction NICs, and detect traffic congestion problems; similar to network monitoring software.
• Spam
  • Unsolicited bulk e-mail, typically commercial in nature, that is becoming a major nuisance to corporate users as well as individuals.
• Spyware
  • Malicious software that has been installed, often unknowingly, on a user’s computer to monitor the user’s actions.
• Storage Area Network, SAN
  • A storage system that allows users to store files on a network. The file system is not controlled by a SAN but is left to the client. Not the same as network attached storage.
• Striping
  • A concept used in RAID in which data is broken into pieces and each piece is stored on a different disk drive.
• Thin Client
  • A workstation computer that is connected to a network and has no CD/DVD drive or hard disk storage.
• Uninstall Software
  • A program that works with the user to locate and remove applications that are no longer needed.
• Uninterruptible power supply, UPS
  • Devices that can maintain power to a computer or device during a power failure for a period long enough to allow a safe shutdown to be performed.
• Utilities
  • A type of network software that often operates in the background and supports one or more functions to keep the network or computer running at optimal performance.
• Web Server Software
  • Software designed to store, maintain, and Web pages.
• Wi-Fi Protected Access II, WPA2
  • A new security standard to replace WPA; supports the IEEE 802.11i standard and uses advanced encryption standards.
• Wi-Fi Protected Access, WPA
  • A set of security standards used to protect wireless LAN transmission that is an improvement over Wired Equivalency Protocol, WEP, in that it provides dynamic key encryption and mutual authentication for wireless clients.
• Wired Equivalent Privacy, WEP
  • The first security protocol used to encrypt wireless LAN transmissions; it uses 40-bit-long encryption keys that are static as opposed to dynamic. Due to the existence of a number of weaknesses, WEP is being replaced.
• Wireless Lan
  • A network configuration that uses radio waves for intercommunication.

Chapter 7: Local Area Networks Part 1

Introduction:

A local area network is a communication network that interconnects a variety of data communications devices within a small geographic area and transmits data at high data transfer rates. The devices that are implied in this definition include: personal computers, computer workstations, mainframe computers, peripheral devices, printers, and modems. The portion of the definition that discusses the "small geographic area" is explaining that a LAN can be a small room, multiple rooms, or multiple floors within a building, and even multiple building on a single campus. The transferring of data at high data rates start from 10 million bits per second to 10 billion bits per second.

Primary function of local area networks:

Users expect a LAN to perform various activities that include: access to internet, file serving, database and application serving, print serving, e-mail serving, process control and monitoring, and distributed processing. Three of the most common application areas for local area networks are office environments, academic environments, and manufacturing environments.

Advantages and disadvantages of local area networks:

Some of the advantages of LANs are their abilities to share resources, independence of system evolution and vice versa, high transfer rates, and low error rates. The disadvantages of local area networks include: high costs for the hardware, operating systems, and software that run the networks; issues with purchasing the wrong user license, and the amount of hours that must dedicate to attending and servicing the networks. The last downfall of a LAN is if an employee upgrades a server, cabling, or network operating system, some other part of the network may need to be improved because of the recent upgrade. A local area network is only as strong as its weakest link.

First local area network: The BUS/TREE:

The bus\tree local area network (bus LAN) was the first physical design when LANs were first available. This network is consisted of a simple cable, or bus, to which all devices are attached. Each device that is attached to the BUS/Tree network is required to have a "tap," which is also called a "passive device." A tap does not alter the signal and does not require electricity to operate. The workstation will contain a "network interface card" (NIC), which is an electric device that performs the necessary signal conversions and protocol operations that allow the workstation to send and receive data.

There are two different types of signaling technologies that can implemented with the BUS/Tree network: baseband signaling and broadband signaling. The baseband signaling uses a digital signal to transmit data over the bus. Baseband transmission is also bidirectional. Broadband technology uses analog signaling in the form of division multiplexing to divide the available medium into multiple channels. The disadvantage with both technologies is that both are difficult to add new workstations if there is no tap for the existing computer.

A more modern LAN:

Star-wired bus LAN is considered to be the most popular configuration for a local area network.  The network logically acts like a bus, but it physically looks like a star. The logical design of a network determines how the data moves around the network from workstation to workstation. The physical design is the pattern the network is formed in. With the networks that contain "hubs" is the medium access control protocol, which is software that allows a device to place data onto a hub-based local area network. There are two basic categories of medium access control protocols for LANs which are: contention-based protocols, and round-robin protocols.

Contention-based protocol is a first-come, first-serve protocol. The first station to recognize that no other station is transmitting data and place its data onto the medium is the first station to transmit. The most popular contention-based protocol is the carrier sense multiple access with collision detection (CSMA/CD). A collision occurs when two workstations listen to the medium at the same time and hear nothing, provoking both workstations to transmit at the same time.

Switches:

Switches use addresses and processing power to direct a frame out of a particular port, thus reducing the amount of traffic on the network. These devices can be used to interconnect multiple workstations on a local area network or multiple LANs.

Virtual LANs:

A virtual LAN (VLAN) is a logical subgroup within a local area network created via switches and software rather than by moving wiring from one network device to another.