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Two or more computers that are linked in order to share resources.

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LAN- Local Area Network

Network that is confined to a small area: writing lab, school or building.

Computers that are connected to a network are broadly categorized as servers or workstations.

Servers generally aren't used by humans directly, run continuously to provide "services" to the other computers on the network.

workstations have human users which interacts with the network through them. Workstations-desktop, consisting of a computer, keyboard, display, and mouse or a laptop.

Servers more powerful than workstations, configurations are guided by need.

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WAN- Wide Area Network

Networks in larger geographic areas- such as United States or the world. Transoceanic cabling or satellite uplinks may be used to connect this type of global network.

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Advantages/Disadvantages of Installing a School Network

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Advantages/Disadvantages of Installing a School Network

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Advantages: user access control, information storing & sharing, connections, services, internet, computer resources, flexible access, and workgroup computing.

Disadvantages: expensive to install, requires administrative time, servers fail, cables may break, and security and compliance.

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Protocol rules that govern the communications between computers on a network. In order for two computers to talk to each other, they need to be speaking the same language.

OSI- Open Systems Interconnection defines seven layers of networking protocols.

OSI Layers: Application, Presentation, Session, Transport, Network, Data Link, Physical

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The physical layer of the network focuses on hardware elements such as cables, repeaters, and network interface cards. The most common protocol used at the physical layer is Ethernet.

Ethernet developed in 1983, had a maximum speed of 10 Mbps over coaxial cable. This cable was heavy, expensive to purchase, install, and maintain and difficult to retrofit into existing facilities.

Fast Ethernet supports transmissions up to 100 Mbsp. requires the use of different more expensive network concentrators/hubs and network interface cards.

Gigabit Ethernet has a transmission speed of 1 Gbps. Can be used with both fiber optic cabling and copper.

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Although there were several popular network protocols used in the 90s and early 21st century they have largely fallen into disuse. Like "LocalTalk" (Apple) or "Token Ring" (IBM). They played an important role in the evolution of networking, but their performance and capacity limitations have put them to the past.

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due to the growth in Internet-based networks, IP/TCP are becoming the leading protocols for most networks.

Every network device have a physical address called a MAC- (Media Access Control) address. Networks using the IP and IPX protocols assign logical addresses to the devices on the network.

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transport layer concerns itself with making sure efficient and reliable transportation of the data packets from one network to another. Most cases, a document, e-mail message or other piece of information is not sent as one unit, it's broken into small data packets.

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Http, Ftp, Smtp, and Dns (Session/Presentation/Application Layers)

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Http, Ftp, Smtp, and Dns (Session/Presentation/Application Layers)

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There are several protocols that overlay the session, presentation, and application layers network: DNS-Domain Name System, DHCP- Dynamic Host Configuration Protocol, FTP-File Transfer Protocol, HTTP- HyperText Transfer Protocol, IMAP- Internet Message Access Protocol, IRC- Internet Relay Chat, POP3- Post Office Protocol Version 3, SMTP- Simple Mail Transfer Protocol.

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networking hardware includes all computers, peripherals, interface cards and other equipment needed to perform data-processing and communications within the network.

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Very fast computers with a large amount of RAM and storage space, along with a one or more fast network interface card. The network operating system provides tools to share server resources and information with network users.

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Workstation- computer that is configured with at network interface card, networking software, and the appropriate cables. Don't necessarily need large storage hard drives, files can be saved on the file server.

Laptops/Mobile- these are becoming more and more common. Have decent internal storage, but also enough power to serve as a workstation on the go. Usually always have a wireless adapter to allow quick network connections.

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Network Interface Card (NIC) the physical connection between the network and the computer workstation. Most are internal and included in the purchase of most computers. The most common network interface connections are Ethernet cards and wireless adapters.

Ethernet Cards- usually included with a computer, although additional cards can be purchased and installed on most computers.

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wireless adapters found in most portable devices, like laptops, smart phones, and tablet devices.

ethernet switch is a device that provides central connection points for cables from workstations, servers, and peripherals.

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Repeaters when a signal looses strength as it passes along a cable, sometimes it's necessary to boost the signal with a device called a repeater. It electrically amplifies the signal it receives and rebroadcasts it. Can be separate or can be incorporated into a concentrator.

Bridges are devices that allows you to segment a large network into two smaller more efficient networks. It monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location.

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routers are considered the traffic directors of the global internet. All routers maintain complex routing tables which allow them to determine appropriate paths for packets destined for any address. Routers communicate with each other and forward network packets out of or into a network.

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a networking device that is installed at the entrance of a LAN when connecting networks together, especially when connecting a private network to a public network like the internet. The firewall uses rules to filter traffic into and out of the private network, protecting private network users and data from hackers.

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the medium which information usually moves from one network device to another. Sometimes a network will utilize only one type of cable, other networks will use a variety of cable types. The types of cables chose for a network is related to the network's topology, protocol, and size.

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1) Unshielded Twisted Pair (UTP) cable

2) Shielded Twisted Pair (STP) cable

3) Coaxial Cable

4) Fiber Optic Cable

5) Cable Installation Guides

6) Wireless LANs

7) Unshielded Twisted Pair (UTP) cable

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Unshielded Twisted Pair/ Shielded Twisted Pair

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Unshielded Twisted Pair/ Shielded Twisted Pair

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Unshielded is the most popular and is generally used for school networks.

Shielded is the least expensive, may be susceptible to radio and electrical frequency interference.

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difficult to install, highly resistant to signal interference. Can support greater cable lengths between network devices than twisted pair cable. There are two types of coaxial cabling; thick and thin.

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consists of a center glass core surrounded by several layers of protective materials. Transmits light instead of electronic signals eliminating the problem of electrical interference. Has the ability to transmit signals over much longer distances than coaxial and twisted pair.

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Uses high frequency radio signals, infrared light beams, or lasers to communicate between the workstations, servers, or hubs.

Great for allowing laptop computers, portable devices, or remote computers to connect to the LAN. Wireless networks are beneficial in older buildings where it may be difficult or impossible to install cables.

Two most common types of infrared communications used in schools are line-of-sight and scattered broadcast.

Line-of-sight must be an unblocked direct line between the workstation and the transceiver.

Scattered broadcast of infrared transmissions sent out in multiple directions that bounces off walls and ceilings until it eventually hits the receiver.

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Three basic techniques to protect networks from unauthorized wireless use.

Encryption- use the strongest encryption supported by the devices. Strong passwords.

Isolation- use wireless router that places all wireless connections on a subnet independent of the primary private network.

Hidden SSID- Disable this feature

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configuration of cables, computers, and other peripherals.

Main Types of Physical Topologies:

1) Linear Bus

2) Star

3) Tree

4) Considerations When Choosing a Topology

5) Summary Chart

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consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connect to the linear cable.

Advantages of a linear bus topology:

1)easy to connect a computer or peripheral to a linear bus

2)requires less cable length than a star topology

Disadvantages of a linear bus topology:

1)entire network shuts down if there is a break-in the main cable.

2)Terminators are required at both ends of the backbone cable.

3)Difficult to identify the problem if the entire network shuts down.

4)Not meant to be used as a stand alone solution in a large building.

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It's designed with each node (file server, Workstations, and Peripherals) connected directly to a central network hub, switch, or concentrator.

Data on a star network passes through the hub, switch, or concentrator before continuing to its destination.

Advantages:

1)easy to install and wire

2)no disruptions to the network when connecting or removing devices

3)easy to detect faults and to remove parts

Disadvantages:

1)requires more cable length than a linear topology

2)if the hub, switch, or concentrator fails, nodes attached are disabled

3)more expensive than linear bus topologies because of the cost of the hubs, etc.

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Combines characteristics of linear bus and star topologies. Consists of star configured workstations connected to linear bus backbone cable. Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Advantages-

1) point-to-point wiring for individual segments

2) supported by several hardware and software venders

Disadvantages-

1) overall length of each segment is limited by the type of cabling used

2) if the backbone lien breaks, the entire segment goes down

3) more difficult to configure and wire than other topologies

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This requires a signal sent out on the network cable reach every part of the network within a specified length of tome. Each concentrator or repeater that a signal goes through adds a small amount of time. Which leads to the rule that between any two nodes on the network there can only be a maximum of 5 segments, connected through 4 repeaters/concentrators. In addition, only 3 of the segments may be populated segments if they are made of coaxial cable.

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Money- a linear bus network may be the least expensive way to install a network; you don't have to purchase concentrators.

Length of Cable Needed- the linear bus network uses shorter lengths of cable.

Future Growth- with a star topology, expanding a network is easily done by adding another concentrator.

Cable Type- The most common cable in schools is unshielded twisted pair, which is most often used with star topologies.

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Chap 6 What is a Network Operating System? NOS

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Chap 6 What is a Network Operating System? NOS

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Unlike Windows that are designed for single users to control one computer, NOS coordinate the activities of multiple computers across a network. The NOS acts as a director to keep the network running smoothly.

Two major types of network operating systems

1) Peer-to-Peer

2) Client/Server

Nearly all modern networks are a combination of both.

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allows users to share resources and files located on their computers and to access shared resources found on other computers. They do not have a file server or a centralized management source. In peer-to-peer network all computers are considered equal; same abilities to use the resources available on the network. Designed for small to medium local are networks.

Advantages-

1) less initial expense- no need for a dedicated server

2) setup- an operating system already in place may only need to be reconfigured for peer-to-peer operations.

Disadvantages-

1) Decentralized- no central repository for files and applications

2) Security- does not provide the security available on a client/server network.

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Allows the network to centralize functions and applications in one or more dedicated file servers. File servers become the heart of the system, providing access to resources and providing security.

Advantages-

1) Centralized-resources and data security controlled through server.

2) Scalability- any or all elements can be replaced individually as needs increase.

3) Flexibility- New technology can be easily integrated into system.

4) Interoperability- all components work together.

5) Accessibility- server can be accessed remotely and across multiple platforms.

Disadvantages-

1) Expense- requires initial investment in dedicated server.

2) Maintenance- large networks will require a staff to ensure efficient operation.

3) Dependence- when server goes down, operations will cease across network.