Download Chapter 12 from Stalling`s book

Course Objectives
The University of New Mexico
• Data communications play a key role in modern
information systems.
• Objective of this course is to make students familiar with
data communication technologies and how to use them to:
– Design
– Implement
– Operate
– Manage
enterprise networks.
© Copyright 1997, The University of New Mexico
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Course Format
The University of New Mexico
• Formal lectures
• Lab sessions
– Design and implementation
– Operation and management
– Fault diagnosis and problem resolution.
• Lecture notes will be provided and supplemented with
vendor specific materials.
• A certificate will be provided upon course completion.
© Copyright 1997, The University of New Mexico
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Course Overview and Outline
The University of New Mexico
• Introductory material
• Network architectures
• Protocols, transmission media, and network
electronics
• Internet / Intranet services
• Network security and management
• Network applications
© Copyright 1997, The University of New Mexico
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The University of New Mexico
•
•
•
•
•
•
Course Overview and Outline
(Cont.)
High speed networking
Wireless communications
Networking trends (futures)
LAN and WAN design
LAN and WAN case studies
Design and implementation Laboratory
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The University of New Mexico
Simple Definition of a “Computer
Network”
• A computer network interconnects a variety of
computing devices (end nodes) so that they may
communicate with each other.
– It consists of computing devices, transmission media
(communication channels) to transmit data and control
signals, communication electronics for routing/switching
data from sources to destination and the software for
doing so.
– Networks may span small to large geographical areas
(LANs, MANs, WANs).
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Building Blocks of a Network
The University of New Mexico
• Terminals, Workstations, Computers, and other
devices (end nodes)
• Transmission Media ( for transmitting data and
control signals)
• Network electronics ( intermediate devices for
routing data from source to destination)
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The University of New Mexico
Building Blocks of a Network
(Cont.)
• Software to control data transmission
• Network Architecture Standards (Standards to
ensure interoperability between different
equipments made by different vendors)
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Terminals and Workstations
The University of New Mexico
• These devices are the data sources and destinations in a
network (ie., end nodes where data originates or is
received).
• Examples
– Personal computers
– Terminals
– Workstations
– Computers
– Point of sale cash registers
– Automatic teller machines
© Copyright 1997, The University of New Mexico
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Transmission Media
The University of New Mexico
• These transmit electronic or light signals and
consist of different media. Transmission media
may be bounded or unbounded.
© Copyright 1997, The University of New Mexico
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Transmission Media (Cont.)
The University of New Mexico
• Bounded Media
- Twisted pair wire
- Co-axial cable
- Fiber optic cables
- Wave guides
© Copyright 1997, The University of New Mexico
• Unbounded Media (air or
a vacuum)
- AM and FM radio
- TV broadcasting
- Satellite communication
- Microwave radio
- Infrared signals
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Network Electronics
The University of New Mexico
• Network electronic devices serve a variety of
functions including routing or switching data from
source to destination or for providing the interface
between different transmission media or different
communication protocols.
© Copyright 1997, The University of New Mexico
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Network Electronics (Cont.)
The University of New Mexico
• Examples
- Bridges
- Routers
- Private Branch
Exchange (PBX)
- Multiplexers
© Copyright 1997, The University of New Mexico
- Concentrators
- Front End Processors
- Switches
- Hubs
- Gateways
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Software
The University of New Mexico
• Software in end nodes implements techniques and
protocols which define the rules and end
procedures for initiating and terminating data
transfers, interpreting how data is represented and
transmitted and how errors are handled.
• Software in the network electronics performs other
functions to ensure data is transmitted from source
to destination(s).
© Copyright 1997, The University of New Mexico
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Network Architecture Standards
The University of New Mexico
• Interface: the point of interaction between two
devices such as a printer and a PC.
• Interconnection standards: specification of the
methods of interfacing two devices, making it
unnecessary for vendors to know the insides of
each other’s equipment as long as the
specifications at the boundaryare met.
© Copyright 1997, The University of New Mexico
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The University of New Mexico
Network Architecture Standards
(Cont.)
• Architecture: blueprint of standards for a network
consisting of items such as choice of media, media
interfaces, encoding methods, transmission
protocols, routing protocols, etc.
• Needed to ensure interoperability between various
devices and equipment made by different vendors.
© Copyright 1997, The University of New Mexico
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Networks for Companies Provide:
The University of New Mexico
• Resource sharing (ending the tyranny of
geography): making all programs, computing
equipment and data available to anyone on the
network without regard to the physical location of
the resource and the user.
• Time independence, can be accessed at any time.
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The University of New Mexico
Networks for Companies Provide:
(Cont.)
• High reliability:
– Redundancy in hardware, software and the network
continue to make services available in a transparent way
to the user even if some components fail. An airline can
lose millions of $’s if its reservation system is not
available 100% of the time.
– Networks also allow physical redundancy, ensuring
continued service if a disaster strikes one location.
© Copyright 1997, The University of New Mexico
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The University of New Mexico
Networks for Companies Provide:
(Cont.)
• Scalability
– Computer networks provide an effective mechanism to
scale up and provide services to more users at more
locations where needed and when needed.
• Manageability
– Networks allow remote resources to be managed
effectively (eg., remote control of telescopes or other
resources).
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The University of New Mexico
Networks for Companies Provide:
(Cont.)
• Cost - Effectiveness
– Networks allow effective implementation of complex
distributed systems that must work together (cooperate).
Eg., combination of mainframes, workstations, PC’s,
networked storage and networked printers.
– Provide access to needed resources from anywhere at
anytime.
– Support collaborative group work independent of
location
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Networks for People Provide:
The University of New Mexico
• Access to remote information through connection
between a person and a remote database.
– financial institutions: people pay their bills, manage
bank accounts, handle investments electronically.
– home shopping through on line catalogs of many
companies.
– personalized on line newspapers.
– on line job search and resume submission.
– access to the World Wide Web and digital libraries with
information on any conceivable topic.
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The University of New Mexico
Networks for People Provide:
(Cont.)
• Person to person communication.
– 21st century’s answer to 20th century telephone-EMAIL
or electronic mail
– technology of the future will bring about video
conferencing over the network.
– worldwide newsgroups with discussions on educational,
academic and other topics.
– electronic university offering classes over the network to
students in far-off and remote areas.
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The University of New Mexico
Networks for People Provide:
(Cont.)
• Interactive entertainment.
– multimedia games.
– video on demand:
• order movies or television shows of choice at anytime from
anywhere
• interactive movies and shows
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Why Networking Is Important
The University of New Mexico
• Key technology of 20th century is information
gathering, processing, and distribution.
• World wide telephone networks were constructed.
• Radio and television networks have reached every
corner of the world.
• Communications satellites have been launched.
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The University of New Mexico
Why Networking Is Important
(Cont.)
• In the past 20 years very powerful affordable
standalone computers have been interconnected to
form computer networks.
• These computer networks are changing the way we
teach, learn, do business, and communicate with
each other.
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Driving Forces
The University of New Mexico
• Technological
• Social
• Economical
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Technological Driving Forces
The University of New Mexico
• Computers are getting cheaper, faster, smaller, and
more reliable.
• The cost of storage is decreasing rapidly.
• Software is getting more useful and easier to use.
• Communication links are getting cheaper and
faster.
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Social Driving Forces
The University of New Mexico
• Convenient access to information at anytime from
anywhere there is a communication link.
• Asynchronous, location independent
communication is possible.
• Everybody (who is anybody) uses it.
• Information (white collar) industries are more
valued than manufacturing (blue collar) industries.
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Economical Driving Forces
The University of New Mexico
• Effective use of computer and communication
technologies can:
–
–
–
–
Enhance business revenues
Reduce operating costs
Avoid costs by increasing people productivity
Create new business opportunities (ATM machine
networks, internet commerce etc.)
– Provide a competitive edge (eg., SABRE reservation
system, United Parcel Service, Levi Strauss)
© Copyright 1997, The University of New Mexico
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Network Evolution
The University of New Mexico
• In the past, networks tended to be designed specifically to
carry voice, video, or data signals.
• The design of voice, video, or data networks differed
because of fundamental differences between voice, video,
and data signals.
eg., voice is analog, data is digital in nature
• The telephone network was the first and is by far the largest
network supporting wired telephones, fax machines,
cellular phones, cordless phones, answering machines, and
modems (for data transmission over the phone network).
© Copyright 1997, The University of New Mexico
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Network Evolution (Cont.)
The University of New Mexico
• The TV network uses a combination of coaxial cable,
satellite links, and electromagnetic propagation
through air to transmit video (including voice) signals.
• The data network uses a variety of transmission media,
including the voice and TV networks, to transmit data
in the form of digital signals.
• Today voice and video are becoming increasingly
digitized (digital phones, high resolution digital TV)
and are increasingly transmitted by data networks.
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Network Evolution (Cont.)
The University of New Mexico
• Ultimately all voice, video, and data will be digital
and will be transmitted by digital (data) networks.
• The reason is that it is far more cost effective to
build, operate and manage networks that use digital
rather than analog signals. (eg., if the telephone
network were built today, it would be an all digital
network).
• Future data networks will interconnect multimedia
devices capable of handling voice, video, and data.
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The University of New Mexico
Differences In Characteristics
Between Data And Telephone (Voice)
Communication
Data Communication
Voice Communication
• Desirable set-up time in one • One second to one minute
second or less
to set up a connection
• One or two way transmission • Two way transmission in
most cases
• Data received is error free
• Tolerant of noise and some
errors
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The University of New Mexico
Differences In Characteristics
Between Data And Telephone (Voice)
Communication (Cont.)
Data Communication
Voice Communication
• Little or no redundancy in
information
• Transmission usually in
bursts
• Much inherent redundant
information
• Transmit or receive
continuously until call is
disconnected
• Data can be stored and
• Not tolerant of transmission
transmitted when convenient delays
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The University of New Mexico
Differences In Characteristics
Between Data And Telephone (Voice)
Communication (Cont.)
Data Communication
Voice Communication
• Transmission has high peaks • Transmission rate relatively
Peak to average ratios as high constant
as 1,000.
• Connection may be required • Duration of connection
for 24 hrs/day, 7 days/week
usually limited to
(eg., cash machine)
several minutes
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The University of New Mexico
Differences In Characteristics
Between Data And Telephone (Voice)
Communication (Cont.)
Data Communication
Voice Communication
• May require wide range of
• Requires a fixed bandwidth
bandwidths-from thousands of about 4,000 Hz.
to millions of Hz.
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Network Evolution (Pre-Internet)
The University of New Mexico
• Computer networking started to evolve in the early
and mid 1960’s with the advent of timesharing.
• By 1970 timesharing machines supported networks
of local and remote terminals.
• These early networks supported timesharing and
remote batch processing.
• In the latter part of the 1970’s, computer to computer
network connections were used for loadsharing and
data interchange (eg., early electronic funds transfer).
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Network Evolution (Early Internet)
The University of New Mexico
• In the late 1970’s and early 1980’s, ARPA (Advanced
Research Projects Agency) started to test networks for
peer-to-peer computer communication and terminal
support on a national scale.
• By the mid 1980’s this network became available to the
universities and NSF (National Science Foundation)
started funding university connectivity.
• Early applications of these networks included electronic
mail, downloading large data sets (ftp) and remote access
to computers (telnet).
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The University of New Mexico
Network Evolution
(Current Internet)
• By the early 1990’s, there were several million
workstations connected to the Internet and use was
growing very rapidly.
• By the mid 1990’s, the internet was a proven
reliable technology and began to be
commercialized.
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The University of New Mexico
Network Evolution
(Current Internet) (Cont.)
• Companies such as Compuserve and America On
Line began to provide a number of services using the
internet, including providing internet connectivity to
personal computers in people’s homes.
• Today, about 20 million workstations are connected
to the commodity Internet and usage continues to
increase, resulting in congestion at peak times of the
day over many parts of the network.
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Network Evolution (Internet 2)
The University of New Mexico
• The increasing network congestion reduced the value
of the Internet for new applications such as webbased distance education and low latency, high
bandwidth connection to and among supercomputers.
• These applications require support for QoS (Quality
of Service) not available on the current Internet.
– eg., bandwidth reservation
– low variance in latency to prevent jerkiness in video
transmission.
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The University of New Mexico
Network Evolution (Internet 2)
(Cont.)
• Consequently, leading research institutions are
leading the development of Internet 2, a new high
bandwidth network strictly for universities to avoid
congestion due to commercial traffic and one that
supports QoS functions required by multimedia
and other applications.
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Functions of Data Networks
The University of New Mexico
• In general, the vast majority of today’s networks are
store and forward networks in that stored data is
forwarded from its source to its destination in a series
of hops when it is convenient to do so.
• While the store and forward technique has several
disadvantages (eg., it is difficult to transmit voice
because the transmission delays are highly variable), it
has the advantage that results in more affordable
networks and it allows errors to be detected and
corrected through retransmission.
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The University of New Mexico
Functions of Data Networks
(Cont.)
• The store and forward concept makes it convenient
for networks to be used for:
– Exchanging electronic mail
– Reading and posting to electronic bulletin boards
– Accessing files and information anywhere in the
network (eg., library and web services)
– Accessing unique hardware and software resources
– Sharing of information (workgroup collaboration)
© Copyright 1997, The University of New Mexico
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The University of New Mexico
Functions of Data Networks
(Cont.)
• Such applications provide users with access to needed
information and resources when they are needed from
wherever there is telephone or some other means of
network access.
• This is changing how we play, work, communicate, teach,
learn, and conduct business.
• They provide both new opportunities and new challenges.
• These challenges will slow the deployment of networks to a
rush from what would otherwise be a stampede.
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Network Challenges
The University of New Mexico
• Address space shortage. IP addresses are limited to
2**32 and efforts are underway to increase this to
2**128.
– enterprises cannot use all 2**24 addresses allowed by a
class A license.
– Class C addresses are more effective but they increase
the size of routing tables in routers, reducing the
efficiency of packet forwarding.
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Network Challenges (Cont.)
The University of New Mexico
• Decentralized control allows the network to easily
scale.
• It also threatens to turn it into an anarchy where
reliable service is not guaranteed. Security is also
an issue.
• It also means there is no uniform way to do usage
accounting, which is required to guarantee Quality
of Service for emerging applications (eg.,
multimedia).
© Copyright 1997, The University of New Mexico
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Network Challenges (Cont.)
The University of New Mexico
• Multimedia (voice, video, and data) applications
need real-time performance guarantees such as a
certain minimum bandwidth or bounded latency
with small variance (jitter).
• These Quality of Service (QoS) performance
parameters are not well supported with the current
Internet technologies.
© Copyright 1997, The University of New Mexico
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Network Challenges (Cont.)
The University of New Mexico
• QoS requires signaling to inform all routers in the
path about the quality of service parameters for
each class of traffic. New traffic streams must be
allowed or denied entry to the network depending
upon the current traffic streams and their QoS
parameters.
• This is difficult to accomplish under decentralized
network control.
© Copyright 1997, The University of New Mexico
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Network Terminology
The University of New Mexico
•
•
•
•
•
•
•
•
General High Usage Terms
Network Electronics Terms
Network Technology Terms
Computing Terms
Services and Application Terms
Standards Organizations
Popular Protocols
Operating Systems
© Copyright 1997, The University of New Mexico
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General High Usage Terms
The University of New Mexico
• Telecommunication - communication (usually
involving computers) over the telephone network.
• Transmission - the movement of data along a
communication link
• PSTN - Public Switched Telephone Network
• LANs - Local Area Networks
• WANs - Wide Area Networks
• MANs - Metropolitan Area Networks
© Copyright 1997, The University of New Mexico
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The University of New Mexico
General High Usage Terms
(Cont.)
• Internet - Term used for the largest global
internetwork connecting tens of thousands of local
area networks.
• WWW - World Wide Web. Large network of
Internet servers providing hypertext and other
services to client workstations
• JAVA - Language for network applications
© Copyright 1997, The University of New Mexico
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Local Area Networks
The University of New Mexico
• Link together enterprise devices that are located
close to each other, typically within a single
building or within a few kilometers of each other.
• Usually implemented and operated by user
organization.
• The delay experienced by workstations is relatively
low while the bandwidth is relatively high.
© Copyright 1997, The University of New Mexico
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Local Area Networks (Cont.)
The University of New Mexico
• The error rate during data transmission is low.
• Workstations have ability to transmit unicast or
multicast messages.
• Peer to peer relationship amongst attached
workstations as opposed to master/slave
relationship.
© Copyright 1997, The University of New Mexico
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Wide area Networks
The University of New Mexico
• Span a large geographical area
• Connect a very large number of devices carrying
many types of traffic.
© Copyright 1997, The University of New Mexico
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Backbone
The University of New Mexico
• The part of the network that acts as the primary
path for traffic that is most often sourced from, and
destined for, other networks.
© Copyright 1997, The University of New Mexico
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Telecommunication
The University of New Mexico
• Term referring to communication, usually
involving computer systems, over the telephone
network.
© Copyright 1997, The University of New Mexico
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Transmission
The University of New Mexico
• Transmission is the movement of data along a
communication link.
• Examples
– telephone system transmits your voice along a complex
set of communication lines and exchanges.
– automated teller machine transmits to your bank’s
computer your request to withdraw cash from your
checking account.
– A radio station transmits its programs which are
received by your radio receiver.
© Copyright 1997, The University of New Mexico
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Network Electronics Terms
The University of New Mexico
•
•
•
•
•
•
•
Switches
Bridges
Routers
Modems
Hubs
Gateways
Terminal Servers
© Copyright 1997, The University of New Mexico
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Network Technology Terms
The University of New Mexico
• Ethernet - Baseband (one frequency) LAN
specification first invented by Xerox Corporation.
• Token Ring - Token passing LAN specification
developed and supported by IBM.
• FDDI - Fiber Distributed Data Interface. LAN
standard specifying a 100 Mbps token passing
network using fiber-optic cable.
© Copyright 1997, The University of New Mexico
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Network Technology Terms (Cont.)
The University of New Mexico
• ATM - Asynchronous Transfer Mode.
International Standard for cell relay in which voice,
video, and data can be transmitted in fixed length
53 byte cells.
• Circuits, Channels, Trunks - Communication paths
between two or more points.
• Frame Relay - Industry standard for handling
multiple switched virtual circuits between
connected devices.
© Copyright 1997, The University of New Mexico
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Network Technology Terms (Cont.)
The University of New Mexico
• Packet Switching - Communication method in
which nodes share bandwidth with each other by
sending packets of data with source and destination
addresses for proper routing
• Connectionless - Term used to describe data
transfer without the existence of a virtual circuit
• Connection Oriented - Term used to describe data
transfer that requires the establishment of a virtual
circuit.
© Copyright 1997, The University of New Mexico
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Computing Terms
The University of New Mexico
• Host - Computer (usually large system) connected
to a network.
• End Systems - End-user workstations on a
network.
• Workstation - A computing device used by a user to
perform his / her work. Some people use the word
to imply a device more powerful than a
conventional personal computer.
© Copyright 1997, The University of New Mexico
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Computing Terms (Cont.)
The University of New Mexico
• Personal Computer - Self explanatory
• Mainframe - An older term used to describe a
large, reliable (and usually expensive) computer for
enterprise-wide computing.
© Copyright 1997, The University of New Mexico
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Services and Application Terms
The University of New Mexico
• Client / Server - Distributed networked systems in
which application responsibilities are divided into 2
parts - the client (front end) and the server (backend).
• Distributed Sytems - Distributed and networked
systems
• Rlogin - Remote login
• FTP - File Transfer Protocol
• Email - Electronic mail
• News - News service
© Copyright 1997, The University of New Mexico
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Standards Organizations
The University of New Mexico
• ITU - International Telecommunication Union which
develops worldwide standards for telecommunication
technologies.
• CCITT - Consultative Committee for International
Telegraph and Telephone. Responsible for development
of Communication standards.
• IEEE - Institute of Electrical and Electronic Engineers.
• ISO - International Standardization Organization.
Responsible for a wide range of standards including
networking standards.
© Copyright 1997, The University of New Mexico
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Standards Organizations (Cont.)
The University of New Mexico
• ANSI - American National Standards Institute.
Approves U.S. standards and develops U.S.
positions in international standards organizations.
• IAB - Internet Architecture Board. Internetwork
researchers who discuss issues pertinent to Internet
architecture.
• IETF - Internet Engineering Task Force. Consists
of over 80 working groups responsible for
developing Internet standards.
© Copyright 1997, The University of New Mexico
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Popular Protocols
The University of New Mexico
• TCP/IP - Transmission Control Protocol/Internet
Protocol. Name of suite of protocols to support the
implementation of worldwide internet works.
• X.25 - ITU’s standard that defines how connections
between terminal equipment and computers are
maintained.
• SMDS - Switched Multi-megabit Data Service.
High speed packet switched WAN networking
technology offered by phone companies.
© Copyright 1997, The University of New Mexico
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Popular Protocols (Cont.)
The University of New Mexico
• ISDN - Integrated Services Digital Network.
Communication protocol offered by phone companies
which allows phone networks to carry voice, video, and
data.
• CDPD - Cellular Digital Packet Data. Standard for 2way wireless data communication over high frequency
cellular phone channels.
• DQDB - Distributed Queue Dual Bus. Data link layer
protocol designed for metropolitan area networks.
• CDMA - Code Division Multiple Access.
© Copyright 1997, The University of New Mexico
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Operating Systems
The University of New Mexico
• UNIX - Operating System developed by Bell
Laboratories in 1969. Most popular operating
system for scientific workstations and computers.
• WINDOWS NT - Emerging network operating
system.
• NOVELL - Name of Company that developed
Netware, an older network operating system.
© Copyright 1997, The University of New Mexico
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Operating Systems (Cont.)
The University of New Mexico
• BANYAN VINES - Network operating system
developed for Banyan networks.
• APPLETALK - Protocol used by personal
computers made by APPLE.
© Copyright 1997, The University of New Mexico
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Network Design Process
The University of New Mexico
• Client Activity
• Designer Activity
• Implementor Activity
© Copyright 1997, The University of New Mexico
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Client Activity
The University of New Mexico
• Client: Manager of group of people that has a
business need which can be met through
networking.
• Client states his needs and any constraints and
passes the buck to the designer.
© Copyright 1997, The University of New Mexico
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Designer Activity
The University of New Mexico
• Designer translates the needs statement and
constraints into a technical blue print or design and
passes the buck to the implementor.
© Copyright 1997, The University of New Mexico
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Implementor Activity
The University of New Mexico
• Implementor uses the designer's blue print to build
and operate a network that meets the needs and
constraints of the client.
© Copyright 1997, The University of New Mexico
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Types of Networks
The University of New Mexico
• Private - Networks for the private use of an
enterprise and its authorized users and no one else.
• Public - Networks that can be used by anyone. The
telephone network is a public network.
• Local Area Networks. - Networks confined to users
in a small geographical area. (eg., a building or a
campus).
© Copyright 1997, The University of New Mexico
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Types of Networks (Cont.)
The University of New Mexico
• Wide Area Networks - Networks that serve users
across a wide geographical area often using
transmission lines provided by common carriers.
• Metropolitan Area Networks - Networks that serve
users across a metropolitan area.
• High Speed Networks - Today, that is about 100
Mbps or higher for LANs and 10 Mbps or higher
for WANs
© Copyright 1997, The University of New Mexico
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