Chapter 1 Introduction to Communications

Always been communication
    - Cavemen drew pictures on caves
    - Indians sent smoke signals
    - Early Americans used the Pony Express to deliver mail

Two common components :
 1. each one used some physical means of delivering a message
 2. the means by which the messages were sent represented the most recent advance in communication for that time
 

Industrial age occurred, more efficient ways of communicating were needed : railroad system needed a fast communication system that would deliver messages quickly and accurately.   Telegraph in 1840 ushered in the age of electronic
communication.   If we look at the history and timelines on pages 1-22 and  1-24 we can see that the development of data communications to its modern stage has happened quickly.
 

Modern electronic communication systems have made the world a smaller place.   Can learn about stuff as it happens, reading live news feeds over the Internet or watching TV.  The transmission of voice, video, and data signals - whether phone calls, faxes, or e-mail - has become the number one priority of the corporate world.
 

What is Data Communications?

Data Communications - the transmission of data (raw facts such as numbers or characters) from point A to point B over some type of medium such as a telephone line.  Data communications is a subset of telecommunications, which is concerned with the transmission of audio, video, and graphical data from one point to another over some medium.  Data communications and telecommunications are NOT the same.  Data communications specifically refers to the transmission of information converted into a computer-readable form over a communication network;  it is much more limited in the type of data that is transmitted than telecommunications.   Examples of telecommunication systems that are not considered data communication systems - building security systems, local and long-distance telephone services, and facsimile services
 

Networks

Data communications sometimes is referred to as data comm or networking because it involves the transmission of data over a network.  Uses networks such as the telephone system to send data.  One or more computers or computer-related devices will be part of  a data communication system - mainframe computers, personal or network computers, laptop computers, terminals, printers

People now have PCs at home, desk  Compare old PC with new PC p. 1-4  Number of computers have increased so has the number of networks - office (computers may be linked into a LAN or connected to a mainframe) and home ("dials in" to the office network or the the Internet)

Data communication network - made up of the computers and computer-related devices that need to communicate with each other,  as well as the devices and lines that connect the computers together.

Why we network - p 1-5

Basic Components of a Communication Network

All components must be present for communication to take place:

1. source (sender)  - the device that is sending the message (can be a terminal, PC ,telephone, or any other device that can be
    connected to a network)
2. medium   - physical path that connects the source and the receiver and is used to transmit the data (can be a copper cable,
    fiber-optic cable, airwaves)
3. receiver  - the device that accepts the message (can be a terminal, PC, telephone, or another computer-related device)
   - must be able to accept the information that has been sent

example of communication process - bank teller and drive-thru p 1-6

circuit - the actual connection between the sending and receiving device
 

The Telephone System and Common Carriers

Intro of phone in 1876
Telephone was a monopoly held by American Telephone and Telegraph (AT&T) until deregulation in 1984.  Recognized standards for placing a telephone call - area code,  seven digit number, busy or ringing signal.  Increased competition and providing consumers with more choices of phone companies but consumer must be aware of their provider.

Internationally telephone systems vary - European countries are not standardized.  In most of these countries, the government owns the telephone.  U.S. signed an agreement in 1997 that would provide lower rates for international calls, provide better service for worldwide customers, and create jobs for telecommunication workers in many countries.  Prior to this US telephone carries could not compete in foreign markets because the telephone service in those countries were government-owned monopolies.

Because telephone system was standardized it was logical that early data communication systems would use the telephone system as a way to send data.  System was easy to use and much of the wiring - telephone lines - was already in place.  A simple computer-to-computer connection over the telephone system created a network.  Today more specialized hardware is required that is not always available from the phone system.  Demand for higher transmission rates have forced the telephone companies to upgrade the capacity of their communication lines.

Common carriers - profit-oriented companies regulated by the government that provide telephone services.  Originally,  common carriers were classified by whether they carried local or long-distance service.  Now they are able to provide both local and long-distance service.  - also sell or lease telephone products to the general public - deregulation made is possible for telephone companies to sell computer-related products as well as communication-related  products.  Gov. regulated the prices that can be charged for communication services, but not for any computers or software that is sold.  Carriers - p 8

When the divestiture took place in 1984 it now mattered if a call was local or long distance.  Deregulation increased competition among the various long distance companies.  Now added to the list of telephone companies are those that sell cellular service (car phones and portable phones). 1996 - companies were allowed to offer both local and long-distance service.  Today many companies also offer Internet services to their customers.

Local Phone Calls - Each of the regional Bell operating companies has a service area for local phone calls.  These service areas are broken into  Local Access Transport Areas (LATAS)  p1-9

long-distance Calls - placed between customers in different service areas may be turned over to a different company.  1+area code+number,  3 largest carriers - AT&T, MCI, Sprint  slamming - consumers switched to another long-distance carrier without their consent
 

Regulatory Agencies
 -established to ensure that the public is protected form unfair practices and pricing by the telephone companies.  Area of jurisdiction is determined by whether the telephone service occurs between states(interstate) or within a state(intrastate)

1. Federal Communications Commission (FCC)
     - regulate interstate telecommunications and the use of airwaves by radio station
     - technical criteria for telecommunication equipment and rates for the common carriers are defined
     - rates set by common carriers must be filed in what are called tariff schedules with the FCC.  The tariffs describe the
            charges common carriers will charge the public for services, along with the classifications of telephone service provided.
     - works with the State Dept. and Commerce Dept. on international matters and negotiations with foreign governments,
            giving the FCC jurisdiction over interstate and foreign telecommunications.

2. Public Utility Commission (PUC)
    - intrastate communication is regulated by state PUC
    - sets rates and policies within their own states, therefore price and types of services offered can vary widely between states
    - approves services offered by communication common carriers
    - PUC is involved in negotiations as long as the dispute is within a single state when disputes arise between companies or
        customers have complaints about communication companies.
 

Standards Organizations

open systems - network hardware or software components can be integrated into any system

1. American National Standards Institute(ANSI)
    - designed to work with various organizations that develop voluntary standards in the US
    - standards for programming languages COBOL and C
    - currently developing a standard for Fiber Distributed Data Interface (FDDI) which will provide guidelines for using
        fiber-optic in a LAN

2. International Standards Organization(ISO)
    - like the ANSI except international
    - Seven-layer model called the Open System Interconnection (OSI) model that defines the various software procedures
        that allow data to be successfully sent to another computer on a communication network

3. Consultative Committee on International Telegraph and Telephone (CCITT)
    - makes technical recommendations concerning telephone, telegraph, and data communication equipment worldwide.
    - ultimate purpose is to ensure that end-to-end communication can be achieved between international connections,
        regardless of the source or destination of the message.

4. Institute of Electrical and Electronics Engineers(IEEE)
    - sets LAN standards
    - IEEE 802.3(Ethernet standard), IEEE 802.4(token bus standard), IEEE 802.5(token ring standard),
        IEEE 1003.1(portable operating system standard)

5. Electronics Industries Association(EIA)
    - sets electrical standards
    - standards set for connectors, RS-232(25-pin) and RS-449(9-pin)

6. Corporation for Open Systems(COS)
    - promotes the use of equipment that meets the ISO standards

7. Communications Satellite Corporation(COMSAT)
    - works to reach agreements with other countries concerning satellite communications

8. International Telecommunications Satellite Organization(INTELSAT)
    - performs many of the same functions as COMSAT but on an international level
 

Why Study Data Communications?

Remote batch system - A centralized computer was used to process data that was collected at a remote site and brought into the computer room for processing.  The data was entered into the centralized computer, and the printed results then were carried by hand back to the remote sites.  Very inefficient and time consuming.

Online processing - computers attached by means of a network, which meant that users at remote sites should input data directly into a central computer and that the central computer should send output directly to remote printers or display screens.  Quicker and also reduces the possibility of lost data and errors

Examples of Everyday Data Communications

1. Banking Apps
    - tellers use terminals that are connected to a central computer through a network to view your account
    - Electronic funds transfer(EFT) - transfer of $ between bank computers, direct deposit
    - Automated Teller machines (ATM) - basically a computer terminal connected by a network to a main computer that
        stores info on bank accounts.

2. Government Apps
    - Census
    - IRS - gather taxpayer info, collect taxes, and issue refunds
    - NASA - calculations needed to launch a space vehicle, keep it in orbit, and return it to Earth
    - military - deployment of troops, launching missiles

3. Libraries
    - online catalogs
    - information at other libraries
    - interlibrary loans, extend a loan
    - Internet
    - databases

4. Retail Stores
    - inventory control, sales, and billing
    - credit card validity

5. Catalog Sales
    - use the telephone or WWW

Review Question Answers