1. Telecommunications Chapter 5 Chapter 5 Telecommunications
Information Systems Foundation, Jessup/Valavich

2. Chapter 5
Telecommunications
Chapter Objectives
Understand the role of telecommunications in organizations
Describe the evolution and types of computer networks
Understand networking fundamentals
Explain the role of the Open System Interconnect (OSI) model and network operating systems
The goal of this chapter is to provide an understanding of data communication fundamentals. Communication requires senders and receivers, a pathway for sending messages, and rules or protocols to manage the communication. Three types of networks are described using these concepts – private branch exchanges, local area networks, and wide area networks – and the hardware, software, and protocols used to make these networks operate. What should be clear from this discussion is that there are numerous types of networks, and literally unlimited ways in which they can be configured. The manner in which networks are constructed and configured influence the speed of the network and the type of information that can be effectively transmitted.
Other current applications such as electronic mail and video conferencing are also rapidly changing the way business is conducted. Global networks allow organizations to streamline business operations in ways never before possible. Additionally, many new data communication technologies are being developed which focus on increasing bandwidths and network speeds. Data communication is fundamental to not only supporting day-to-day activities within most organizations, but is also playing an increasingly larger role in the competitive strategy of more and more organizations. More than ever before, managers must understand these technologies in order to ride the data communication wave and to apply the right solutions to the right problems.
Information Systems Foundation, Jessup/Valavich

3. The Components of an Information System
Chapter 5
Telecommunications
The Components of an Information System
An information system consist of hardware, software, and telecommunications that are used to process data by people.
Information Systems Foundation, Jessup/Valavich

4. Importance of Telecommunications
Chapter 5
Telecommunications
Importance of Telecommunications
Work Group Communication
Video conferencing
Emerging Business Applications
Electronic Commerce
Electronic Data Interchange (EDI)
Rapid rate of change in technology
provides the ability to store and deliver information which reduces the constraints of real-time communication.
Video conferencing provides audio and video communication among locations. CU-SeeMe is an example of an Internet-based video conferencing tool that supports multiparty video conferencing.
Electronic commerce includes order taking, order verification, invoicing, and electronic funds payments.
Using EDI, trading partners (suppliers, manufacturers, customers, etc.) can exchange data electronically.
BRIEF CASE: EDI at Walgreens
Walgreens uses EDI to save time and money. The easily combine invoices from all their stores into a single statement for one supplier. Verification of the statement and payment can be accomplished in a matter of minutes. Walgreens uses a proprietary EDI network to which its suppliers must also subscribe.
Information Systems Foundation, Jessup/Valavich

5. Data Communication All communications require three things:
Chapter 5
Telecommunications
Data Communication
All communications require three things:
Senders and receivers that have something to share
Coded by sender
Decoded by receiver
A pathway or transmission media to send the message
Rules or protocols of communication
Coding a message is formatting according to some predetermined symbol set. Decoding is converting a message into some format you understand. In human communication, we use languages for coding and decoding.
Having a pathway does not ensure that communication will occur--the message must be understood for communication to really take place.
A protocol is an established set of rules governing communication.
Information Systems Foundation, Jessup/Valavich

6. Human vs Computer Communication

7. Chapter 5
Telecommunications
Computer Networks
Computers and other devices connected by a communications channel
Share files and other resources between users
Channel: the transmission media
Bandwidth: carrying capacity of the media
Protocols: the physical and logical rules for transmission
Computer communication consists of transmitting bits over telecommunication lines.
Digitizing is the conversion of any format to electronic bits.
Telecommunications is the electronic transmission of all forms of information from one location to another over some type of network
Networks make many things possible, such as distance learning, telemedicine, and telecommuting.
BRIEF CASE: Florida School for the deaf and blind
Telecommunications technologies open doors for many students at this school. Blind students learn to communicate via a network as early as first grade. Deaf students use technology to learn and develop language skills.
Information Systems Foundation, Jessup/Valavich

8. Modems

9. Remaining Topics Computing Network Models Classes of Computer Networks
Building Blocks of Computer Networks

10. Computing Network Models
Chapter 5
Telecommunications
Computing Network Models
Centralized computing
Uses mainframes and “dumb” terminals
Distributed computing
Uses separate computers
Collaborative computing
Uses two or more networked computers
Networks today include all three models
The centralized computing model is not really a network because there is no sharing of information and capabilities. It just uses central processing.
The introduction of personal computers allows organizations to let separate computers work on subsets of tasks rather than using one mainframe to perform all the processing.
Collaborative computing allows workers to use computers separately but on common tasks.
Information Systems Foundation, Jessup/Valavich

11. Centralized Computing Model

12. Distributed Computing Model

13. Collaborative Computing Model

14. Computing Network Models Classes of Computer Networks
Centralized, distributed, collaborative
Classes of Computer Networks
Building Blocks of Computer Networks

15. Classes of Computer Networks
Chapter 5
Telecommunications
Classes of Computer Networks
Private Branch Exchange (PBX)
A privately owned telephone switch
Local Area Network (LAN)
Usually confined to a single building or site
Wide Area Network (WAN)
Enterprise network - one organization
Global network
PBX can be used to connect computers and phone systems within an organization. The main disadvantage to PBX networks are their limited bandwidth.
LANs share data, software applications, or other resources among several users.
WANs connects users across much larger distances than a LAN. They can be used to interconnect two or more LANs.
Enterprise networks connect all the LANs of a organization.
Global networks span multiple countries.
An emerging trend is the use of Value Added Networks. VAN’s are private, third-party managed WANs used by many organizations simultaneously. They provide economies because they are shared by multiple organizations.
BRIEF CASE: Pepsi’s Enterprise Network
Pepsi connects nearly 330 sites on one enterprise network. This network allows decision makers to make better, faster decisions.
Information Systems Foundation, Jessup/Valavich

16. Private Branch Exchange

17. Local Area Network

18. Enterprise Network

20. Computing Network Models Classes of Computer Networks
Centralized, distributed, collaborative
Classes of Computer Networks
PBX, LAN, WAN (enterprise & global)
Building Blocks of Computer Networks

21. Building Blocks of Computer Networks
Chapter 5
Telecommunications
Building Blocks of Computer Networks
Servers, Clients, and Peers
Network Services
Transmission Media
Network Topologies
Network Access Control Methods
Major Standards
The following slides discuss various aspects of network fundamentals.
Information Systems Foundation, Jessup/Valavich

22. Servers, Clients, and Peers
Chapter 5
Telecommunications
Servers, Clients, and Peers
Server-centric networks
Server
A network computer that makes services available to users
Client
Uses services provided by a server
Peer-to-peer networks
Allow any computer or device to provide and request services
A server is any computer on the network that makes access to files, printing, communications, and other services available to users of the network. It typically has a more advanced microprocessor, more memory, a larger cache, and more disk storage.
Clients only request services. A client usually has only one user, whereas many different users share the server.
Peer-to-peer networks are typically found in small offices or even homes.
Information Systems Foundation, Jessup/Valavich

23. Servers, Clients, and Peers

24. Computing Network Models Classes of Computer Networks
Centralized, distributed, collaborative
Classes of Computer Networks
PBX, LAN, WAN (enterprise & global)
Building Blocks of Computer Networks
Server-centric/peer-to-peer
Network Services
Transmission Media
Network Topologies
Network Access Control Methods
Major Standards

25. Network Services Offered by the network operating system File services
Chapter 5
Telecommunications
Network Services
Offered by the network operating system
File services
Store, retrieve, and move data
Print services
Control access to printers and fax machines
Message services
Deal with communication between network users
Application services
Run software for network clients
Network services are the capabilities that networked computers share through combinations of hardware and software.
Organizations must decide whether these services will be centralized (server-client) or distributed (peer-to-peer). This decision will affect the choice of the network operating system.
Novell NetWare is an example of a common server-client network operating system.
Information Systems Foundation, Jessup/Valavich

26. Computing Network Models Classes of Computer Networks
Centralized, distributed, collaborative
Classes of Computer Networks
PBX, LAN, WAN (enterprise & global)
Building Blocks of Computer Networks
Server-centric/peer-to-peer
Network Services
Transmission Media
Network Topologies
Network Access Control Methods
Major Standards

27. Transmission Media The physical pathway that carries signals
Chapter 5
Transmission Media
Telecommunications
The physical pathway that carries signals
Media characteristics
Bandwidth - transmission capacity stated in megabits per second (Mbps)
Attenuation - weakening of signal over distance
EMI - electromagnetic interference
Two forms
Cable media
Wireless media
Bandwidth represents how much binary data can be reliably transmitted over the medium in one second.
Other media characteristics to consider are ease of eavesdropping, cost of the cable, and ease of installation.
Cable and wireless media are discussed on the following slides.
Information Systems Foundation, Jessup/Valavich

28. Cable Media Twisted Pair Coaxial Fiber Optic
Chapter 5
Telecommunications
Cable Media
Twisted Pair
Two or more pairs of insulated copper wires
Coaxial
Inner copper conductor surrounded by plastic insulation with outer braided foil shield
Fiber Optic
Uses pulses of light to send data
Glass or plastic core surrounded by cladding with a tough outer sheath
Twisted pair may be unshielded (UTP) or shielded (STP). Telephone wire installations use UTP. It is rated according to capacity: Category 3 (10 Mbps), Category 5 (100 Mbps). STP improves the sensitivity to EMI and eavesdropping, but it still has high attenuation rates.
Coax comes in sizes based on thickness. Thinnet coax is less costly than STP or CAT 5 UTP. Thicknet coax is more expensive than STP or CAT 3 UTP. Coax is commonly used for cable television and networks operating at 10 Mbps.
Optical interfaces must be installed at both the input and output ends in order to convert the signals to light pulses and back again. Fiber optic cables are often used for high-speed backbones--the central networks to which many smaller networks are connected.
Information Systems Foundation, Jessup/Valavich

29. Wireless Media Infrared Line of Sight High-Frequency Radio
Chapter 5
Telecommunications
Wireless Media
Infrared Line of Sight
Light waves transmit data on unobstructed path
High-Frequency Radio
Radio signals up to 39.6 meters
Microwave Line of Sight
Terrestrial uses earth-based antennas
Satellite sends signals between antennas on earth and orbiting satellites
Wireless media is more common in WANs.
Infrared can support up to 16 Mbps at 1 km. Its attenuation and susceptibility to eavesdropping are problematic.
The flexibility of the signal path makes high-frequency radio ideal for mobile transmissions. Two common applications of high-frequency radio communication are pagers and cellular phones.
Terrestrial stations are often used to cross inaccessible terrain or to connect buildings.
Access to microwave systems are typically leased. Satellite transmission can be extremely costly.
Satellite transmissions are subject to relatively long delays.
Information Systems Foundation, Jessup/Valavich

30. Computing Network Models Classes of Computer Networks
Centralized, distributed, collaborative
Classes of Computer Networks
PBX, LAN, WAN (enterprise & global)
Building Blocks of Computer Networks
Server-centric/peer-to-peer
Network Services
Transmission Media (Cable, Wireless)
Network Topologies
Network Access Control Methods
Major Standards

31. Network Topologies Star Network Ring Network Bus Network
Chapter 5
Telecommunications
Network Topologies
Star Network
All nodes attached to center a hub
Messages must pass through the hub
Ring Network
A closed loop
Messages move in one direction
Bus Network
An open-ended line
Nodes receive message at the same time
Network topology refers to the shape of the network, how the wiring is laid out, and the relationship of nodes on the network.
A node is a computer or device on a network.
Star - The center of the star is a wiring hub or concentrator to which all the nodes or workstations are attached and through which all messages pass. Star networks are susceptible to a single point of failure at the hub.
Ring - As a message moves around the circle, each workstation examines it to see whether the message is for that workstation. If not, the message is passed on to the next node. A failure of any node on the network can cause complete network failure.
Bus - A bus network is the easiest to extend and has the simplest wiring layout. It is difficult to diagnose and isolate network faults.
Information Systems Foundation, Jessup/Valavich

32. Star Network

33. Ring Network

34. Bus Network

35. Computing Network Models Classes of Computer Networks
Centralized, distributed, collaborative
Classes of Computer Networks
PBX, LAN, WAN (enterprise & global)
Building Blocks of Computer Networks
Server-centric/peer-to-peer
Network Services
Transmission Media (Cable, Wireless)
Network Topologies (Star, Ring, Bus)
Network Access Control Methods
Major Standards

36. Network Access Control Methods
Chapter 5
Telecommunications
Network Access Control Methods
Distributed Access Control
Token passing
Circulating electronic token prevents collisions
Must possess the token to transmit a message
Random Access Control
CSMA/CD
“Listen” for quiet line; then send message
Collision occurs with simultaneous messages
Must wait and resend
Access control methods are rules on how a node gains access to the network in order to send or receive.
A workstation that receives the token and wants to send a message marks the token as busy, appends a message to it, and transmits both. Each station copies the message and retransmits the token/message combination. When it is received at the originating station, the message is removed and the token is marked as free and sent on.
Random Access - A message is sent to all workstations on the network, however, only the destination with the proper address is able to open the message. This method allows good media access when traffic is light, but performance deteriorates rapidly under heavy traffic conditions.
Information Systems Foundation, Jessup/Valavich

37. Token Ring Operation

38. Computing Network Models Classes of Computer Networks
Centralized, distributed, collaborative
Classes of Computer Networks
PBX, LAN, WAN (enterprise & global)
Building Blocks of Computer Networks
Server-centric/peer-to-peer
Network Services
Transmission Media (Cable, Wireless)
Network Topologies (Star, Ring, Bus)
Network Access Control Methods (Distributed—Token passing, Random)
Major Standards

39. Chapter 5
Telecommunications
Major Standards
To ensure the interoperability and compatibility of networks
Three major standards for LAN
Ethernet
Token-Ring
ARCnet
The Institute of Electrical and Electronic Engineers (IEEE) act as a coordinating body and establish telecommunications standards.
The three major standards combine physical and logical topologies and media access control techniques in different ways.
Information Systems Foundation, Jessup/Valavich

40. Connectivity Hardware
Chapter 5
Telecommunications
Connectivity Hardware
Computers can be physically connected in many ways
Each device must be connected to the medium
After individual devices are connected to the network, multiple segments of transmission media can be connected to form one large network.
Information Systems Foundation, Jessup/Valavich

41. Key Components of a Local Network
Chapter 5
Telecommunications
Key Components of a Local Network
Transmission Media Connectors
Network Interface Cards (NIC)
Modems (MOdulator/DEModulator)
Repeaters
Hubs
Bridges
Mutiplexers (MUX)
Transmission media connectors - Common connectors are “T” (coax ) and RJ-45 (twisted pair). They connect the medium to nodes or other pieces of medium.
Network Interface Card (NIC) is a PC expansion board that connects to the medium. Each NIC has a unique identifier for addressing.
Modems (MOdulator/DEModulator) transmit information over telephone lines by converting digital signals of a computer to analog signals used in telephone systems and then converting it back to digital at the other end.
Repeaters are used to amplify or regenerate the electronic signal.
Hubs are used as a central point of connection between media segments and enable the network to be extended to accommodate additional workstations.
Bridges forward traffic between network segments to specific addresses. They can connect network segments that use different wiring or network protocols
Mutiplexers (MUX) are used to share communications circuits among a number of users when the medium provides more capacity than a single signal can occupy. They can transmit several signals over a single channel.
Information Systems Foundation, Jessup/Valavich

42. Key Components for Internetworking
Chapter 5
Telecommunications
Key Components for Internetworking
Routers
Brouters
Channel Service Units (CSU)
Gateways
Distributed LANs interconnected by WANs use internetwork hardware.
Routers - Intelligent devices used to connect two or more individual networks. When a router receives a signal, it looks at the network address and passes the signal on to the appropriate network.
Brouters - Devices that combine both routing and bridging functions.
Channel Service Units (CSU) - Devices that act as a “buffer” between a LAN and public carrier’s WAN. They ensure that all signals placed on the public line are appropriately timed and formed. They must be certified by the FCC.
Gateways - A shared connection between a LAN and a larger system. They perform protocol conversions so that different networks can communicate even though they use different protocols.
Information Systems Foundation, Jessup/Valavich

43. Connectivity Software
Chapter 5
Telecommunications
Connectivity Software
The OSI Model
Network Operating Systems
The following slides discuss the OSI model and network operating systems.
Information Systems Foundation, Jessup/Valavich

44. Chapter 5
Telecommunications
The OSI Model
Protocol representing a group of specific tasks that allow data communication between two computers
Each higher layer builds on the functions of the layers below
Novell NetWare's IPX/SPX protocol is a LAN protocol.
TCP/IP is the Internet protocol used to connect networks.
Information Systems Foundation, Jessup/Valavich

45. The OSI Model

46. The OSI Model and Message Passing

47. Network Operating Systems
Chapter 5
Telecommunications
Network Operating Systems
Client/server architecture LANs
The system software runs on the file server
Part of the NOS runs on each workstation
Peer-to-peer networks
NOS is installed on each attached workstation
Runs on top of the local operating system
The NOS coordinates functions such as user accounts, access information, security, and resource sharing.
A recent trend is integrating the NOS into the workstation operating system. Windows NT is an example of this integration.
BRIEF CASE: Remotely Managing AFS’ Network
AFS manages an international exchange program for high school students. They use Novell Netware for their LAN needs. The network is managed by a separate company from a remote location because AFS did not have an information system staff and could not afford to hire network professionals. Outsourcing their networking allows them to focus on their primary mission and not on the network.
Information Systems Foundation, Jessup/Valavich

48. Computing Network Models Classes of Computer Networks
Centralized, distributed, collaborative
Classes of Computer Networks
PBX, LAN, WAN (enterprise & global)
Building Blocks of Computer Networks
Server-centric/peer-to-peer
Network Services (File, print, message, application)
Transmission Media (Cable, Wireless)
Network Topologies (Star, Ring, Bus)
Network Access Control Methods (Distributed -Token passing, Random)
Major Standards (The OSI Model)