Course Objectives

Course Objectives • 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.

Course Format • 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.

Course Overview and Outline • Introductory material • Network architectures • Protocols, transmission media, and network electronics • Internet / Intranet services • Network security and management • Network applications

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

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).

Building Blocks of a Network • 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)

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)

Terminals and Workstations • 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

Transmission Media • These transmit electronic or light signals and consist of different media. Transmission media may be bounded or unbounded.

Transmission Media (Cont.) • Bounded Media • Unbounded Media (air or a vacuum) - Twisted pair wire - AM and FM radio - Co-axial cable - TV broadcasting - Fiber optic cables - Satellite communication - Wave guides - Microwave radio - Infrared signals

Network Electronics • 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.

Network Electronics (Cont.) • Examples - Bridges - Concentrators - Routers - Front End Processors - Private Branch - Switches Exchange (PBX) - Hubs - Multiplexers - Gateways

Software • 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).

Network Architecture Standards • 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.

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.

Networks for Companies Provide: • 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.

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.

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).

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

Networks for People Provide: • 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.

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.

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

Why Networking Is Important • 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.

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.

Driving Forces • Technological • Social • Economical

Technological Driving Forces • 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.

Social Driving Forces • 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.

Economical Driving Forces • 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)

Network Evolution • 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).

Network Evolution (Cont.) • 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.

Network Evolution (Cont.) • 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.

Differences In CharacteristicsBetween 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

Differences In CharacteristicsBetween Data And Telephone (Voice) Communication (Cont.) Data Communication Voice Communication • Little or no redundancy in • Much inherent redundant information information • Transmission usually in • Transmit or receive bursts continuously until call is disconnected • Data can be stored and • Not tolerant of transmission transmitted when convenient delays

Differences In CharacteristicsBetween 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

Differences In CharacteristicsBetween 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.

Network Evolution (Pre-Internet) • 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).

Network Evolution (Early Internet) • 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).

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.

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.

Network Evolution (Internet 2) • The increasing network congestion reduced the value of the Internet for new applications such as web-based 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.

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.

Functions of Data Networks • 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.

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)

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.

Network Challenges • 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.

Network Challenges (Cont.) • 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).

Network Challenges (Cont.) • 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.

Network Challenges (Cont.) • 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.

Network Terminology • General High Usage Terms • Network Electronics Terms • Network Technology Terms • Computing Terms • Services and Application Terms • Standards Organizations • Popular Protocols • Operating Systems

General High Usage Terms • 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

Course Objectives