Chapter 7a(networking Basics)

Chapter-7A Networking Basics

Networks A group of two or more computer systems linked together.

Data Backup In information technology, backup refers to making copies of data so that these additional copies may be used to restore the original after a data loss event. These additional copies are typically called "backups." Backups are useful primarily for two purposes. The first is to restore a computer to an operational state following a disaster (called disaster recovery). The second is to restore small numbers of files after they have been accidentally deleted

Data Backup Open file backup Many backup software packages feature the ability to back up open files.. Cold database backup During a cold backup, the database is closed or locked and not available to users. Hot database backup Some database management systems offer a means to generate a backup image of the database while it is online and usable ("hot").

Types Of Network LAN A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. Most LANs connect workstations and personal computers. Each node (individual computer ) in a LAN has its own CPU with which it executes programs, but it also is able to access data and devices anywhere on the LAN. This means that many users can share expensive devices, such as laser printers, as well as data. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions.

LAN

WAN A computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs). Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites. The largest WAN in existence is the Internet.

WAN

Campus Area Network(CANs) Acronym for campus-area network. An interconnection of local-area networks within a limited geographical space, such as a school campus or a military base.

Metropolitan Area Network(MAN) Short for Metropolitan Area Network, a data network designed for a town or city. In terms of geographic breadth, MANs are larger than local-area networks (LANs), but smaller than widearea networks (WANs).

Home Area Network(HANs) Short for home area network. A HAN is a network contained within a user's home that connects a person's digital devices, from multiple computers and their peripheral devices to telephones, VCRs, televisions, video games, home security systems, "smart" appliances, fax machines and other digital devices that are wired into the network.

Intranet Network based on belonging to an organization, usually a corporation, accessible only by the organization's members, employees, or others with authorization. An intranet's Web sites look and act just like any other Web sites, but the firewall surrounding an intranet fends off unauthorized access.

Extranet An intranet that is partially accessible to authorized outsiders. Whereas an intranet is accessible only to people who are members of the same company or organization, an extranet provides various levels of accessibility to outsiders. You can access an extranet only if you have a valid username and password, and your identity determines which parts of the extranet you can view. Extranets are becoming a very popular means for business partners to exchange information.

How Network Are Structured

Server-Based Network User gain access to files, printers and other network based objects by obtaining permission given through a centrally controlled server.

Client/server Network A network architecture in which each computer or process on the network is either a client or a server. Servers are powerful computers or processes dedicated to managing disk drives (file servers), printers (print servers), or network traffic (network server ). Clients are PCs or workstations on which users run applications. Clients rely on servers for resources, such as files, devices, and even processing power.

Client/server Network

Peer to Peer Network Often referred to simply as peerto-peer, or abbreviated P2P, a type of network in which each workstation has equivalent capabilities and responsibilities.

Peer to Peer Network

TOPOLOGIES Topology refers to the shape of a network, or the network's layout. How different nodes in a network are connected to each other and how they communicate are determined by the network's topology. Topologies are either physical or logical. Below are diagrams of the five most common network topologies. Mesh Topology Devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network.

Star Topology All devices are connected to a central hub. Nodes communicate across the network by passing data through the hub.

Bus Topology All devices are connected to a central cable, called the bus or backbone.

Ring Topology All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it.

Tree Topology A hybrid topology. Groups of starconfigured networks are connected to a linear bus backbone.

Protocol An agreed-upon format for transmitting data between two devices. The protocol determines the following: the type of error checking to be used data compression method, if any how the sending device will indicate that it has finished sending a message how the receiving device will indicate that it has received a message There are a variety of standard protocols from which programmers can choose. Each has particular advantages and disadvantages; for example, some are simpler than others, some are more reliable, and some are faster. From a user's point of view, the only interesting aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers.

TCP/IP pronounced as separate letters) Short for Transmission Control Protocol/Internet Protocol, the suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the standard (format, language)for transmitting data over networks.

IPX/SPX Short for Internet work Packet Exchange, a networking protocol used by the Novell NetWare operating systems. IPX is datagram protocol used for connectionless communications.

Short for Sequenced Packet Eexchange, a transport layer protocol used in Novell Netware networks. The SPX layer sits on top of the IPX layer and provides connection-oriented services between two nodes on the network. SPX is used primarily by client/server applications. Whereas the IPX protocol is similar to IP, SPX is similar to TCP. Together, therefore, IPX/SPX provides connection services similar to TCP/IP.

NetBIOS/NetBEUI Pronounced net-booey, NetBEUI is short for NetBios Extended User Interface. It is an enhanced version of the NetBIOS protocol (Network Basic Input Output System)used by network operating systems such Windows 95 and Windows NT. Netbeui was originally designed by IBM for their Lan Manager server and later extended by Microsoft and Novell.

Network Media Twisted Pair wire coaxial Cable Fiber optic cable

Twisted pair wire A type of cable that consists of two independently insulated wires twisted around one another. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. While twisted-pair cable is used by older telephone networks and is the least expensive type of local-area network (LAN) cable, most networks contain some twisted-pair cabling at some point along the network.

Twisted pair cable

Coaxial Cable A type of wire that consists of a center wire surrounded by insulation and then a grounded shield of braided wire. The shield minimizes electrical and radio frequency interference. Coaxial cabling is the primary type of cabling used by the cable television industry and is also widely used for computer networks, such as Ethernet. Although more expensive than standard telephone wire, it is much less susceptible to interference and can carry

Coaxial Cable.

Fiber optic cable A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. Fiber optics has several advantages over traditional metal communications lines: Fiber optic cables have a much greater bandwidth than metal cables. This means that they can carry more data. Fiber optic cables are less susceptible than metal cables to interference. Fiber optic cables are much thinner and lighter than metal wires. Data can be transmitted digitally (the natural form for computer data) rather than analogically. The main disadvantage of fiber optics is that the cables are expensive to install. In addition, they are more fragile than wire. Fiber optics is a particularly popular technology for local-area networks. In addition, telephone companies are steadily replacing traditional telephone lines with fiber optic cables. In the future, almost all communications will employ fiber optics.

Fiber Optic Cable

Fiber Optic Cable

Wireless Media The word wireless is dictionary defined as "having no wires". In networking terminology, wireless is the term used to describe any computer network where there is no physical wired connection between sender and receiver, but rather the network is connected by radio waves and/or microwaves to maintain communications.

NIC Card Often abbreviated as NIC, an expansion board you insert into a computer so the computer can be connected to a network. Most NICs are designed for a particular type of network, protocol.

NIC Card

Network Linking Device HUB Bridge Switches Router

HUB A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets

HUB

Switch In networks, a device that filters and forwards packets between LAN segments

Bridge A device that connects two localarea networks (LANs), or two segments of the same LAN that use the same protocol.

Bridge

Router A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where two or more networks connect. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols to communicate with each other and configure the best route between any two hosts. Very little filtering of data is done through routers.

Router

UTP Cable Short for unshielded twisted pair, a popular type of cable that consists of two unshielded wires twisted around each other. Due to its low cost, UTP cabling is used extensively for local-area networks (LANs) and telephone connections. UTP cabling does not offer as high bandwidth or as good protection from interference as coaxial or fiber optic cables, but it is less expensive and easier to work with. Examplke-twisted cable likeCAT5,CAT6 cable

RJ-45 Connector Short for Registered Jack-45, an eight-wire connector used commonly to connect computers onto a localarea networks (LAN), especially Ethernets. RJ-45 connectors look similar to the RJ-11 connectors used for connecting telephone equipment, but they are somewhat wider.

RJ45 Connector

Gateway A node on a network that serves as an entrance to another network. In enterprises, the gateway is the computer that routes the traffic from a workstation to the outside network that is serving the Web pages. In homes, the gateway is the ISP that connects the user to the internet. In enterprises, the gateway node often acts as a proxy server and a firewall. The gateway is also associated with both a router, which use headers and forwarding tables to determine where packets are sent, and a switch, which provides the actual path for the packet in and out of the gateway.