T2.ppt

INFORMATION TECHNOLOGY Networks and Telecommunications

Learning Outcomes
Summarize the individual components of a computer network
Describe the three main network topologies
Explain the difference between the three main forms of network access methods
Summarize the difference between guided media and unguided media
Explain how a network operating system works
List the transmitting and receiving devices used in a computer network
Describe the function of TCP/IP
Summarize the use of a VPN

Introduction
introduces the concept of computer networks
Computer network ( or network) - a group of two or more computer systems linked together using wires or radio waves over a geographical area
Computer networks that do not use physical wires are called wireless
takes a detailed look at the key concepts that are integrating computer networks and data communications

The Need for Networking
A network provides two principle benefits:
The ability to communicate
The ability to share
Groupware - software that supports team interactions and dynamics including calendaring, scheduling, and videoconferencing
is the most popular form of network communication E-Mail

The Benefits of Computer Networking
Store virtually any kind of information at, and retrieve it from, a central location on the network
Combines the power and capabilities of diverse equipment providing a collaborative medium to combine the skills of different people, regardless of physical location
Enables people to share information and ideas easily
They can work more efficiently and productively

Networking Basics
Networks are assembled according to certain rules:
Each cabling strand can only support a certain amount of network traffic, etc
Topology - the actual physical organization of the computer devices including connections
Bandwidth - indicates how much information can be carried in a given time period over a wired or wireless communications link

Networking Basics (continued)
The network industry refers to nearly every type of network as an “area network”
Local Area Network (LAN) - connects network devices over a relatively short distance
Sometimes one building will contain a few small LANs, and occasionally a LAN will span a group of nearby buildings
Wide Area Network (WAN) - is a geographically dispersed telecommunications network
Metropolitan Area Network (MAN) - interconnects users in a geographic area or region larger than a local area network, but smaller than a wide area network
Example: A university may have a MAN that joins together many of their local area networks situated around its campus

Networks – The Big Picture
A network is made up of many physical elements:
Computers, printers, and other devices
The manner in which all these items are connected is referred to as the network topology
Network topologies are further subdivided into two categories:
Physical topologies
Logical topologies

Physical Topologies
the actual physical organization of the computers on the network and its connections
Bus topology - all devices are connected to a central cable
Star topology - all devices are connected to a hub
Ring topology - all devices are connected to one another in a closed loop
Tree topology - combines the characteristics of the bus and star topologies
Wireless topology - all devices are connected by a receiver/transmitter to a special network interface card that transmits signals between a computer and a server; all within an acceptable transmission range

Physical Topologies

Network Access Methods (Protocols)
Protocol - the predefined way that someone (who wants to use a service) talks with or utilizes that service
The most popular LAN protocols include:
Token Ring
Ethernet
Fiber Distributed Data Interface (FDDI)

Token Ring
Token ring network - a LAN in which all computers are connected in a ring or star topology and a token-passing schema is used in order to prevent the collision of data between two computers that want to send messages at the same time
Second most widely used protocol on local area networks
Data transfer rates of either 4 or 16 megabits per second

Ethernet
Ethernet is the most widely installed LAN access method originally developed by Xerox
When it first began to be widely deployed in the 1980s, Ethernet supported a maximum data rate of 10 megabits per second ( Mbps )
Fast Ethernet standards have extended traditional Ethernet technology to 100 Mbps peak
Gigabit Ethernet technology extends performance up to 1000 Mbps

Ethernet and Token Ring Network

Fiber Distributed Data Interface (FDDI)
FDDI - a set of protocols for sending digital data over fiber optic cable
FDDI networks are token-passing networks that supports data rates of up to 100 megabits per second
FDDI networks are typically used as backbones for wide area networks

Fiber Distributed Data Interface

Networking Hardware
To be sent from one location to another, a signal must travel along a physical path
The physical path that is used to carry a signal between a signal transmitter and a signal receiver is called the transmission medium
Network transmission media - the various types of media used to carry the signal between computers
Two types of transmission media: Guided and Unguided

Guided media
Transmissions material manufactured so that signals will be confined to a narrow path and will behave predictably
Three common types of guided media are: twisted-pair wiring, coaxial cable, and fiber optic cable

Twisted-Pair Wiring
a type of cable composed of four (or more) copper wires twisted around each other within a plastic sheath
The wires are twisted to reduce outside electrical interference
The RJ-45 connectors on twisted-pair cables resemble large telephone jacks

Coaxial Cable
cable that can carry a wide range of frequencies with low signal loss
Consists of a metallic shield with a single wire placed along the center of a shield and isolated from the shield by an insulator
Two different types
Thinnet coaxial cable - similar to the cable used by cable television companies
Thicknet coaxial cable - similar to thinnet except that it is larger in diameter

Fiber Optic Cable
Fiber optic (or " optical fiber ") - the technology associated with the transmission of information as light impulses along a glass or plastic wire or fiber
Optical fiber cable can transmit data over long distances with little loss in data integrity
Optical fiber is not subject to interference

Cable Summary

Unguided Media
Unguided media - natural parts of the Earth’s environment that can be used as physical paths to carry electrical signals
Examples include microwaves, infrared light waves, and radio waves

Transmitting and Receiving Devices
Network adapters
Modems
Repeaters
Wiring concentrators, hubs, and switches
Bridges, routers, and gateways
Microwave transmitters
Infrared and laser transmitters
Cellular transmitters
Wireless LAN transmitters

Network Adapters
Network adapter - the hardware installed in computers that enables them to communicate on a network
The most common form is designed to be installed directly into a standard expansion slot inside a PC

Modems
Modems - provide the means to transmit digital computer data typically over ordinary telephone lines
The transmitting modem converts the encoded data signal to an audible signal and transmits it
A modem connected at the other end of the line receives the audible signal and converts it back into a digital signal for the receiving computer
Modems are commonly used for inexpensive communications between a network and geographically isolated computers

Repeaters
used to increase the distance over which a network signal can be propagated
A signal travels through a transmission medium, it encounters resistance and gradually becomes weak and distorted
The repeater receives the network signal and retransmits it at the original transmission strength

Concentrators, Hubs, and Switches
Concentrators, hubs, and switches - provide a common physical connection point for computing devices
Most hubs and all wiring concentrators and switches have built-in signal repeating capability to perform signal repair and retransmission

Bridges, Routers, and Gateways
used to interconnect network segments
Bridges
Routers
Bridges and routers - generally used to connect networks that use similar protocols
Gateways
used to connect networks that use dissimilar protocols; examples includes TCP/IP and IPX

Microwave Transmitters & Receivers
commonly used to transmit network signals over great distances

Infrared and Laser Transmitters
Infrared and laser transmitters - similar to microwave systems: they use the atmosphere and outer space as transmission media
They require a line-of-sight transmission path
Useful for signaling across short distances where it is impractical to lay cable

Cellular Transmitters
Cellular transmitters - radio transmissions and therefore have the advantage of being able to penetrate solid objects
A cellular base station at the center of each cell contains:
Low-power transmitters
Receivers
Antennas
Common control computer equipment
Cellular devices are configured to operate at low power to avoid interfering with other cellular devices in the area

Wireless LAN Transmitters
function like hubs and switches in a wired environment, only they propagate signals through radio waves or infrared light instead of wires

The Network Operating System
an operating system that includes special functions for connecting computers and devices into a local area network
Two categories:
Client-server
Peer-to-peer

Client-Server Networks
a versatile, message-based, and modular infrastructure that is intended to improve usability , flexibility , interoperability , and scalability as compared to centralized, mainframe computing

Thin Client-Server Networks
Thin clients - similar to terminals connected to mainframes, the server performs the bulk of the processing, and the client presents the interface
Thin clients are usually devoid of floppy drives, expansion slots, and hard disks; consequently, the “box” or central processing unit is much smaller than that of a conventional PC

Peer-to-Peer Networks
Enable networked computers to function as both servers and workstations

Internet Technology
The world’s largest computer network
Two most influential technologies:
Transmission Control Protocol/Internet Protocol (TCP/IP) suite
World Wide Web (WWW)

TCP/IP
TCP/IP - a group, or suite, of networking protocols used to connect computers on the Internet
Two main protocols in the suite are:
TCP provides transport functions, ensuring, among other things, that the amount of data received is the same as the amount transmitted
The IP part of TCP/IP provides the addressing and routing mechanism

The TCP/IP suite of applications
File Transfer Protocol (FTP) - allows files to be downloaded off or uploaded onto a network
Simple Mail Transfer Protocol (SMTP) - TCP/IP’s own messaging system for e-mail
Telnet protocol - provides terminal emulation
Hypertext Transfer Protocol (HTTP) - allows Web browsers and servers to send and receive Web pages
Simple Network Management Protocol (SNTP) - allows the management of networked nodes to be managed from a single point

The TCP/IP Protocol Suite

World Wide Web
The World Wide Web is a client-server environment
Information is managed through Web sites on computers called Web servers
Accessing Web sites is done through the use of client software (i.e., a browser) and the Internet’s HTTP
Computers and Web sites on the Internet are linked through documents called Web pages written in HTML

Intranet vs. Extranet
Intranet – an internalized portion of the Internet, protected from outside access, that allows an organization to provide access to information and application software to only its employees
Extranet - a private network that uses the Internet protocol and the public telecommunication system to securely share part of a business's information or operations with suppliers, vendors, partners, customers, or other businesses

Virtual Private Network (VPN)
VPN - a private WAN that uses the Internet as a low-cost WAN backbone to transport data between two or more geographically separate sites
Advantages that a VPN has over a dedicated-line WAN:
The cost of implementation
No need to lay cable or lease dedicated lines between the remote sites needing to connect
Businesses can network remote offices into one large WAN and provide access to the Internet

Intranet, Extranet, and VPN Technologies

T2.ppt

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