Lecture-8/ T. Nouf Almujally
description
Transcript of Lecture-8/ T. Nouf Almujally
Telecommunications
and NetworksSection 2 “Telecommunications Network Alternatives”
CHAPTER 6
Lecture-8/ T. Nouf Almujally
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Telecommunications Network Alternatives
Telecommunications is a highly technical, rapidly changing field
Most business professionals don’t needdetailed technical knowledge
However, understanding basic componentsand their characteristics is necessary
Can help you make informed decisions abouttelecommunications alternatives
Telecommunications Network Model
A telecommunications network is any arrangement where… A sender transmits a message to a receiver Over a channel Consisting of some sort of medium
Key Telecommunications Network Component Categories
1. Terminals Any input/output device that uses
telecommunications networks to transmit or receive data
Example: Networked personal computers, network computers or information appliances.
Con.2. Telecommunications processors
Devices that support data transmission and reception between terminals and computers.
Control and support functions in telecommunications network.
Convert data from digital to analog and back code and decode data control the speed, accuracy, and efficiency of the
communications flow between computers and terminals in a network.
Example: modems, switches, and routers
3. Telecommunications channels Media over which data are transmitted and
received Example: copper wires, coaxial cables,
microwave, cellular systems
4. Computers All sizes and types of computers are
interconnected by telecommunications networks.
Con.
Con.5. Telecommunications control software
Controls telecommunications activities Manages the functions of telecommunications
networks
Example: network management programs of all kinds such as,
Telecommunications monitors (mainframes) Network operating systems (network servers) Web browsers (microcomputers)
Types of Communications Networks
CommunicationNetworks
Wide Area
Peer-to-Peer
Client/Server
Virtual Private
Local Area
1- Wide Area Network (WAN)
• Telecommunications networks covering a large geographic area.
• WANs are used by many multinational companies to transmit and receive information among their employees, customers, suppliers, and other organizations across cities, regions, countries, and the world.
2- Local Area Network (LAN)• Connects computers within a limited physical
area, such as an office, classroom, or building.• To communicate over the network:
• each PC usually has a circuit board called “network interface card”
• Most LANs use more powerful microcomputer with a large hard disk capacity, called “file server” or “network server”.
• It contains a network operating system program that controls telecommunications and the use and the sharing of network resources.
Local Area Network (LAN)
• LAN allows users to share hardware, software, and data resources.
3- Virtual Private Network• VPN is used to establish secure
intranets and extranets• The Internet is the main backbone network• Relies on network firewalls, encryption, and
other security features• VPN = “pipe” travelling through the Internet• Creates a private network without the high cost
of a separate proprietary connection
Virtual Private Network
4- Client/Server Network• Clients
• End user personal computers or networked computers
• Servers• Used to manage the networks
• Processing• Shared between the clients and servers• Sometimes called a two-tier architecture
• Downsizing: Larger computer systems are being replaced with multiple client/server networks
Client/Server Network
Network Computing• Called network centric• Views networks as the central computing resource
of the organization• Thin clients provide a browser-based user interface for
processing small application program called applets• Thin clients include:
• Network computers• Net PCs• Other low-cost network devices or information
appliances
Network Computing• Application and database servers provide
• The operating system• Application software• Applets• Databases• Database management software
• Sometimes called a three-tier client/server model because it consists of:• Thin clients• Application servers• Database servers
Network Computing
5- Peer-to-Peer Networks
Central Server Architecture
P2P file-sharing software connects all PCsto a central server
Clicking a link connects the two PCs andautomatically transfers the file to the
requesting PC
The server sends the requesting PC a list oflinks to all active peers who have the file
Peer-to-Peer Networks
Pure Peer-to-Peer Architecture
No central directory or server
File-sharing software connectsone PC to another online user
When you request a file, the softwaresearches every online user, then sends
you a list of active file names
Clicking a link automatically transfers the filefrom that user’s hard drive to yours
Peer-to-Peer Network Diagrams
Central Server Peer-to-Peer Networks
Advantages
Can better protect the integrity and security of the
content and users of the network
Disadvantages
Directory servercan be slowed or overwhelmed by
too many users or technical problems
Pure Peer-to-Peer Networks
Disadvantages
Slow response times bogus and corrupted
files
Telecommunications Media• Telecommunications channels make use
of a variety of telecommunications media.
• These include:• Wired technologies: which physically link
the devices in a network.• Wireless technologies: which uses
microwave, radio waves or infrared light to transport digital communications without wires between communication devices.
Wired Technologies
• Twisted-Pair Wire• Ordinary telephone wire• Copper wire is twisted into pairs• The most widely used medium for
telecommunications, used in home and office telephone systems and many LANs and WANs.
• Used in established communications networks throughout the world for both voice and data transmission.
• Transmission speeds can range from 2 million bits per second (unshielded) to 100 million bits per second (shielded).
Twisted-Pair Wire
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Shielded Twisted–pair cable
Unshielded Twisted–pair cable
Wired Technologies• Coaxial Cable
• Sturdy copper or aluminum wire wrapped with spacers to insulate and protect it.
• The cable’s cover minimize interference and distortion of the signals the cable carries.
• They allow high speed data transmission from 200 to more than 500 million bits per second (200-500 Mbps).
• Used in high-service metropolitan areas, LANs and for short distance connections of computers and peripheral devices.
Wired Technologies• Fiber-Optic Cable
• One or more hair-thin filaments of glass fiber wrapped in a protective jacket.
• Transmission rates are high (trillions of bits per second)
• Fiber-optic are not affected by and do not generate electromagnetic radiation; therefore multiple fibers can be placed in the same cable.
• Need less repeaters for signal retransmissions.
• Expected to replace other communications media
The Problem of “The Last Mile”• Network providers use fiber optic cable as a
communications backbone.• Houses connected to the backbone are wired
with twisted pair (can’t handle the bandwidth provided by fiber)
• Users don’t benefit from the faster, better technology.
• Methods to solve this problem:• Using sophisticated technologies, only coaxial wire that
originally put there.• Bypassing the old wired network completely and provide
high speed services via a satellite or other wireless approach.
• WiMax (still under development stages)
WiMax
Wireless TechnologiesTerrestrialMicrowave
Earthbound microwave systems transmit high-speed radio signals in a line-of-sight path between relay systems spaced about 30 miles apartAntennas placed on top of buildings, towers, and mountain peaks.
Communications Satellites
Use microwave radio signalsServe as relay stationsEarth stations beam signals to the satellites that amplify and retransmit the signals to other earth stationsNot suitable for interactive, real-time processing
Cellular andPager Systems
Use radio technologiesGeographic areas divided into cellsEach cell has low-power transmitter or radio relay antennaComputers & other communications processors coordinate/control transmissions to/from mobile users
Wireless Technologies
Terrestrial Microwave
Communications Satellites Cellular,PCS telephone &Pager Systems
Wireless TechnologiesWireless
LANS
Uses wireless radio-wave technology to connect PCs within an office or building
Wi-Fi is faster and less expensive than common wire-based LAN technologies
Bluetooth
Short-range wirelessConnects PCs to peripheral devicesOperating at 1 Mbps – range from 10 to 100 metersIts a cable replacement technology
Wireless Web
Wireless access to the Internet is growing as more web-enabled information appliances appear.Smart telephones, PDAs all are very thin clients in wireless networksWAP (Wireless Application Protocol) is the foundation of wireless mobile Internet and Web Applications.
The Wireless Protocol (WAP)
Telecommunications Processors
• Telecommunication Processors:Perform a variety of support functions between the computers and other devices in a telecommunications network.1- Modems:
• the most common type of communications processor. Converts a digital signal to an analog frequency that can be transmitted over phone lines, then back into a digital signal (modulation and demodulation).
• Come in several forms.• Support a variety of functions.
• Transmission error control, faxing, and Automatic dialling and answering
Telecommunications Processors
Telecommunications networks are interconnected by special-purpose communications processors called :2. Internetwork Processors: such as
Hub and Switch: makes connections between telecommunications circuits in a network. They provide automatic switching among connections called “ports” for shared access to a network’s resources.
Bridge: connect two or more LANs that use the same communications rules or protocol.
Router: intelligent communications processor that interconnects networks based on different protocols
Telecommunications Processors
Communications Processors
3. Multiplexer:• Allows a single communications channel to carry simultaneous data transmissions from many terminals.• Multiplexers work to increase the
number of transmissions possible without increasing the number of physical data channels.
Telecommunications Software• Telecommunications and network
management SW may reside in PCs, servers, mainframes, and communications processors.• Vital part of all telecommunications networks.• Used to manage network performance.• Servers rely on network operating systems like
Novell Netware, UNIX, Microsoft Widows Servers.
Network Management Functions
Traffic Management
Manage network resources & traffic to avoid congestion, optimize service levels
Security Provide authentication, encryption, firewall, auditing.
Network Monitoring
Troubleshoot & watch over the network, alerting administrators to problems
Capacity Planning
Survey network resources, traffic patterns, and users’ needs
Determine the best way to accommodate network needs as it grows and changes
Network TopologiesTopology: The structure of a network• Star Network
• Ties end user computers to a central computer• Ring Network
• Ties local computer processors together in a ring on a relatively equal basis
• Bus Network• Local processors share the same communications channel
• Mesh Networks• Uses direct communications lines to connect some or all of
the computers to one another.
Network Topologies
Read from Chapter 6 (Section 2)