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Unshielded Twisted Pair (UTP) Cable

Varies from telephone grade wire to high speed cable

Cheapest wire

May be susceptible to radio and electrical frequency interference

Shielded Twisted Pair (STP) Cable

Extends maximus distance of cables

Is less susceptible to radio and electrical frequency interference

3 Configurations

Each pair of wires is individually shielded with foil.

There is a foil or braid shield inside the jacket covering all wires (as a group).

There is a shield around each individual pair, as well as around the entire group of wires (referred to as double shield twisted pair).

Coaxial Cable

Has a single copper conductor at its center

Difficult to install

Highly resistant to interference

Fiber Optic Cable

Has a center that is made from glass or plastic fibers

Surrounded by several layers of protection

Transmits signals over much longer distances than coaxial or STP

Cable Installation Guides

Always use more cable than you need. Leave plenty of slack.

Test every part of a network as you install it. Even if it is brand new, it may have problems that will be difficult to isolate later.

Stay at least 3 feet away from fluorescent light boxes and other sources of electrical interference.

If it is necessary to run cable across the floor, cover the cable with cable protectors.

Label both ends of each cable.

Use cable ties (not tape) to keep cables in the same location together.

Wireless LANs

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

Security can be an issue

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 A network is a system of 2 or more computers that are linked to share resources, exchange files or allow electronic communications. 

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 A network is a system of 2 or more computers that are linked to share resources, exchange files or allow electronic communications. 

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Most widely used:

LAN - Local Area Network

WAN - Wide Area Network

Also:

Metropolitan Area Networks (MAN), a Wireless LAN (WLAN), or a Wireless WAN (WWAN)

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Usually used in a smaller area, confined to a building

Services provided can include printing and faxing, software hosting, file storage and sharing, messaging, data storage and retrieval, complete access control (security) for the network's resources, and many others

Used in work stations, computer labs.

Can be connected by cables or wirelessly

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Connect networks in larger geographic areas, example: statewide

A WAN is more complicated than a LAN

It uses multiplexers, bridges, and routers to connect local and metropolitan networks to global communications networks like the Internet.

To a use a WAN will function like a LAN

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A school network is a LAN.

Advantages:

User access control

User credentials are centrally owned and managed

Can provide specific services to your network

More control

Disadvantages:

Can be expensive

Required maintenance

Network security must be provided but is expensive and

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Protocol is the communication between computers on the network.

OSI (Open Systems Interconnection) define 7 layers of networking protocols:

1. Physical

2. Data Link

3. Network

4. Transport

5. Session

6. Presentation

7. Application

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4 Layers of Communication via the Internet 

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4 Layers of Communication via the Internet 

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1. Ethernet (Physical/Data Link Layers)

1. The physical layer of the network focuses on hardware elements, such as cables, repeaters, and network interface cards

2. Most common layer used at the physical level = cords, how to connect

3. Uses a twisted pair wire

4. Fast Ethernet, Gigabit Ethernet

5. Some old networks are still in operation due to the availability of Ethernet

2. IP/IPX (Network layer)

1. This layer is in charge of routing network messages (data) from one computer to another.

2. Networks using the IP and IPX protocols assign logical addresses (which are made up of the MAC address and the network address) to the devices on the network,

3. The network layer takes care of assigning the correct addresses (via IP or IPX) and then uses routers to send the data packets to other networks.

3. TCP/SPX (Transport Layer)

1. The transport layer is concerned with efficient and reliable transportation of the data packets from one network to another.

2. Example - a document, email.

3. TCP, paired with IP, is by far the most popular protocol at the transport level.

4. HTTP, FTP, TelNet, SMTP, DNS (combined Session/Presentation/ Application Layers)

1. Several protocols overlap the session, presentation, and application layers of networks.

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File Network Server - A part of a LAN. The network operating system provides tools to share server resources and information for network users. Includes the fastest processors, a large amount of RAM, multiple large, fast hard drives, extra expansion slots and a fast network interface card(s).

Workstations - Computers that people use. They are configured with a network interface cared, networking software and appropriate cables.

Network Interface Cards - These provide the physical connection between the network and the computer workstation. It is an internal device and usually is sold with the computer. These determine the speed and performance of the network. The most widely used NIC is an Ethernet card and wireless adapters.

Switches - An Ethernet switch is a device that provides a central connection point for cables from a workstation or server.

Repeaters - These electrically amplify the signal to boost connectivity.

Bridges - These segment the large network into two smaller, more efficient networks. It monitors the traffic online and maintains optimum performance.

Routers - These are the traffic lights of the internet. They communicate with each other and allow access. They are network gateways.

Firewalls - Can be hardware or software. They provide protection to the network.

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Definition: the way in which constituent parts are interrelated or arranged.

The Physical Topology of a Network:

The configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. Logical topology was discussed in the Protocol chapter.

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10Base2 - Ethernet specification for thin coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 185 meters per segment.

10Base5 - Ethernet specification for thick coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 500 meters per segment.

10BaseF - Ethernet specification for fiber optic cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 2000 meters per segment.

10BaseT - Ethernet specification for unshielded twisted pair cable (category 3, 4, or 5), transmits signals at 10 Mbps (megabits per second) with a distance limit of 100 meters per segment.

100BaseT - Ethernet specification for unshielded twisted pair cabling that is used to transmit data at 100 Mbps (megabits per second) with a distance limit of 100 meters per segment.

1000BaseTX -Ethernet specification for unshielded twisted pair cabling that is used to transmit data at 1 Gbps (gigabits per second) with a distance limitation of 220 meters per segment.

Asynchronous Transfer Mode (ATM) - A network protocol that transmits data at a speed of 155 Mbps and higher. It is most often used to interconnect two or more local area networks.

AppleTalk - Apple Computer's network protocol originally designed to run over LocalTalk networks, but can also run on Ethernet and Token Ring.

AUI Connector (Attachment Unit Interface) - A 15 pin connector found on Ethernet cards that can be used for attaching coaxial, fiber optic, or twisted pair cable.

Backbone - A cable to which multiple nodes or workstations are attached.

Bit - Binary digit in the binary numbering system. Its value can be 0 or 1. In an 8-bit character scheme, it takes 8 bits to make a byte (character) of data.

BNC Connector (Bayone-Neill-Concelman) - Standard connector used to connect 10Base2 coaxial cable.

Bridge - Devices that connect and pass packets between two network segments that use the same communications protocol.

Byte - an 8-bit long binary value, which originally mapped to text character values (between 0 and 255 decimal). For example, a decimal value of 65, represented in a binary byte is "01000001" and represents the capital letter "A". A byte also is the atomic value of data storage, so a megabyte is the amount of memory required to store a million bytes.

Cable - Transmission medium of copper wire or optical fiber wrapped in a protective cover.

Client/Server - A networking system in which one or more file servers (Server) provide services; such as network management, application and centralized data storage for workstations (Clients).

CSMA/CA - Carrier Sense Multiple Access Collision Avoidance is a network access method in which each device signals its intent to transmit before it actually does so. This prevents other devices from sending information, thus preventing collisions from occurring between signals from two or more devices. This is the access method used by LocalTalk.

CSMA/CD - Carrier Sense Multiple Access Collision Detection is a network access method in which devices that are ready to transmit data first check the channel for a carrier. If no carrier is sensed, a device can transmit. If two devices transmit at once, a collision occurs and each computer backs off and waits a random amount of time before attempting to retransmit. This is the access method used by Ethernet.

Coaxial Cable - Cable consisting of a single copper conductor in the center surrounded by a plastic layer for insulation and a braided metal outer shield.

Concentrator - A device that provides a central connection point for cables from workstations, servers, and peripherals. Most concentrators contain the ability to amplify the electrical signal they receive.

DIN - A plug and socket connector consisting of a circular pattern of pins in a metal sleeve. This type of connector is commonly seen on keyboards.

Dumb Terminal - Refers to devices that are designed to communicate exclusively with a host (main frame) computer. It receives all screen layouts from the host computer and sends all keyboard entry to the host. It cannot function without the host computer.

E-mail - An electronic mail message sent from a host computer to a remote computer.

End User - Refers to the human executing applications on the workstation.

Ethernet - A network protocol invented by Xerox Corporation and developed jointly by Xerox, Intel and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps (megabits per second).

Expansion Slot - Area in a computer that accepts additional input/output boards to increase the capability of the computer.

Fast Ethernet - An Ethernet standard that supports 100 Mbps using category 5 twisted pair or fiber optic cable.

Fiber Distributed Data Interface (FDDI) - A network protocol that is used primarily to interconnect two or more local area networks, often over large distances.

Fiber Optic Cable - A cable, consisting of a center glass core surrounded by layers of plastic, that transmits data using light rather than electricity. It has the ability to carry more information over much longer distances.

File Server - A computer connected to the network that contains primary files/applications and shares them as requested with the other computers on the network. If the file server is dedicated for that purpose only, it is connected to a client/server network. An example of a legacy client/server network is Novell Netware. All the computers connected to a peer-to-peer network are capable of being the file server. Most modern operating systems can operate as servers or as clients, greying the distinction in the server architecture.

Firewall - A security device which inspects traffic entering and leaving a network, and allows or disallows the traffic, depending on rules describing acceptable use of the network, by filtering out unwanted packets. The firewall is usually positioned as the gateway device to another network, such as the internet. Many routers now contain firewalls. A personal firewall is usually software that runs on a workstation or server to filter unwanted traffic at the individual machine.

Gigabit Ethernet - An Ethernet protocol that raises the transmission rates to 1 Gbps (gigabits per second). Most school, corporate, and household networks provide gigabit ethernet to the workstations via cabled connections.

Gigabyte (GB) - One billion bytes of information. One thousand megabytes.

Hub - A hardware device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat but merely split signals sent through them).

Infrared - Electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum.

Intranet - Network internal to an organization that uses Internet protocols.

Internet - A global network of networks used to exchange information using the TCP/IP protocol. It allows for electronic mail and the accessing ad retrieval of information from remote sources.

LAN (Local Area Network) - A network connecting computers in a relatively small area such as a building.

Linear Bus - A network topology in which each node attaches directly to a common cable.

LocalTalk - Apple Corporation proprietary protocol that uses CSMA/CA media access scheme and supports transmissions at speeds of 230 Kbps (Kilobits per second).

MAN (Metropolitan Area Network) - A network connecting computers over a large geographical area, such as a city or school district.

MAU (Multistation Access Unit) - A Token Ring wiring hub.

Modem (Modulator/Demodulator) - Devices that convert digital and analog signals. Modems allow computer data (digital) to be transmitted over voice-grade telephone lines (analog).

Multiplexer - A device that allows multiple logical signals to be transmitted simultaneously across a single physical channel.

Network Modem - A modem connected to a Local Area Network (LAN) that is accessible from any workstation on the network.

Network Interface Card (NIC) - A board that provides network communication capabilities to and from a computer.

Network Operating System (NOS) - Operating system designed to pass information and communicate between more than one computer. Examples include Linux/Unix and Windows Server.

Node - End point of a network connection. Nodes include any device attached to a network such as file servers, printers, or workstations.

Node Devices - Any computer or peripheral that is connected to the network.

PCMCIA - (later versions were PCMCIA2 and PC Card) An expansion slot found in many laptop computers. Largely replaced by USB in the 2000-2010 period.

Peer-to-Peer Network - A network in which resources and files are shared without a centralized management source.

Physical Topology - The physical layout of the network; how the cables are arranged; and how the computers are connected.

Point-to-Point - A direct link between two objects in a network.

Ports - A connection point for a cable.

Protocol -A formal description of a set of rules and conventions that govern how devices on a network exchange information.

RAID (Redundant Array of Inexpensive Disks) - A configuration of multiple disks designed to preserve data after a disk casualty.

RAM (Random Access Memory) - The working memory of a computer where data and programs are temporarily stored. RAM only holds information when the computer is on.

Repeater - A device used in a network to strengthen a signal as it is passed along the network cable.

RJ-45 - Standard connectors used for unshielded twisted-pair cable.

Router -A device that routes information between interconnected networks. It can select the best path to route a message, as well as translate information from one network to another. Many routers now contain firewalls. Home routers can contain firewall, router, switching (for cabled connections), and a wireless access point.

SCSI (Small Computer Serial Interface) - An interface controller that allows several peripherals to be connected to the same port on a computer.

Segment - Refers to a section of cable on a network. In Ethernet networks, two types of segments are defined. A populated or trunk segment is a network cable that has one or more nodes attached to it. A link segment is a cable that connects a computer to an interconnecting device, such as a repeater or concentrator, or connects a interconnecting device to another interconnecting device.

Sneaker-Net - Refers to a manual method of sharing files in which a file is copied from a computer to a floppy disk, transported to a second computer by a person physically walking (apparently wearing sneakers) to the second computer, and manually transferring the file from floppy disk to the second computer.

Speed of Data Transfer - The rate at which information travels through a network, usually measured in megabits per second.

Star Topology - LAN topology in which each node on a network is connected directly to a central network hub or concentrator.

Star-Wired Ring - Network topology that connects network devices (such as computers and printers) in a complete circle.

Switch - A "intelligent" type of hub, in that it sends packets only to the intended ports, rather than all computers on the network.

Tape Back-Up - A common server or network peripheral which allows copying data and programs from a computer system to magnetic tape. On tape, data is stored sequentially. When retrieving data, the tape is searched from the beginning of tape until the data is found.

Terminator - A device that provides electrical resistance at the end of a transmission line. Its function is to absorb signals on the line, thereby keeping them from bouncing back and being received again by the network.

Thicknet - A thick coaxial cable that is used with a 10Base5 Ethernet LAN.

Thinnet - A thin coaxial cable that is used with a 10Base2 Ethernet LAN.

Token - A special packet that contains data and acts as a messenger or carrier between each computer and device on a ring topology. Each computer must wait for the messenger to stop at its node before it can send data over the network.

Token Ring - A network protocol developed by IBM in which computers access the network through token-passing. Usually uses a star-wired ring topology.

Topology - There are two types of topology: physical and logical. The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Logical topology is the method used to pass the information between workstations. Issues involving logical topologies are discussed on the Protocol chapter

Transceiver (Transmitter/Receiver) - A Device that receives and sends signals over a medium. In networks, it is generally used to allow for the connection between two different types of cable connectors, such as AUI and RJ-45.

Tree Topology - LAN topology similar to linear bus topology, except that tree networks can contain branches with multiple nodes.

Twisted Pair - Network cabling that consists of four pairs of wires that are manufactured with the wires twisted to certain specifications. Available in shielded and unshielded versions.

USB/ USB2 Port - A hardware interface for peripherals from keyboards to hard drives, widely used on all computers.

WAN (Wide Area Network) - A network connecting computers within very large areas, such as states, countries, and the world.

Workgroup - A collection of workstations and servers on a LAN that are designated to communicate and exchange data with one another.

Workstation - A computer connected to a network at which users interact with software stored on the network.

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redundant array of inexpensive 
      disks

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This is a glossary of computer network terms.

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Network Operating System (NOS):

Coordinates the activities of multiple computers across a network. The network operating system acts as a director to keep the network running smoothly.

1. Peer to peer

Allows users to share resources and files located on their computers and to access shared resources found on other computers. However, they do not have a file server or a centralized management source.

Security is an issue.

Is decentralized.

2. Client/Server

Allows the network to centralize functions and applications in one or more dedicated file servers (See fig. 2). The file servers become the heart of the system, providing access to resources and providing security. Individual workstations (clients) have access to the resources available on the file servers. The network operating system provides the mechanism to integrate all the components of the network and allow multiple users to simultaneously share the same resources irrespective of physical location. UNIX/Linux and the Microsoft family of Windows Servers are examples of client/server network operating systems.

Expensive and requires maintenance.

If the server goes down the network ceases to exist.

NOS Software: Microsoft Windows Server, Macintosh OSX, UNIX/Linux

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Advantages -

Easy to connect a computer or peripheral to a linear bus.

Requires less cable length than a star topology.

Disadvantages -

Entire network shuts down if there is a break in the main cable.

Terminators are required at both ends of the backbone cable.

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

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

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Advantages -

Easy to install and wire.

No disruptions to the network when connecting or removing devices.

Easy to detect faults and to remove parts.

Disadvantages -

Requires more cable length than a linear topology.

If the hub, switch, or concentrator fails, nodes attached are disabled.

More expensive than linear bus topologies because of the cost of the hubs, etc.

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Advantages -

Point-to-point wiring for individual segments.

Supported by several hardware and software venders.

Disadvantages -

Overall length of each segment is limited by the type of cabling used.

If the backbone line breaks, the entire segment goes down.

More difficult to configure and wire than other topologies.