Local Area Networks and E-Mail

Instructor’s Notes

Chapter Overview

In this chapter you will learn about networks; hardware, software, and processing capabilities. You will also learn how to use networks by selecting a secure password and logging into a network. Further, you will learn how to share files, about groupware, and about using e-mail.
 

Lecture Notes

Key Terms

Local Area Networks

The chapter begins with the information about networks that is most immediately of interest to a computer user— how to use a network. If you have been using a network in the computer lab at school or at work, many of the concepts presented in this section should be familiar to you, though you may not have previously learned the appropriate terminology.

Use Figure 7-6 to see how a file can be accessed by more than one user at a time. You might note that this figure applies to all types of servers, except a non-dedicated server. If you store a file on a non-dedicated server that also happens to be your own workstation, other network users can access that file if they have rights to do so.

Review Figure 7-7 to understand why it is important to lock data files so two people cannot use them at the same time. Use Figure 7-9 to see how a workstation accesses a network printer.

Network Hardware

In this section the discussion touches briefly on network cards and cables, then focuses on network server architecture.

In this section of the chapter, students are presented with a number of different server types: dedicated and non-dedicated file servers, print servers, and application servers.

A dedicated file server (Figure 7-13) is devoted to the task of delivering programs and data files to workstations. If your school has a "Novell network" it has one or more file servers which act as a central repository for programs and data files. These servers are not used as workstations for everyday computing tasks such as word processing.

A non-dedicated server (Figure 7-14) is a workstation that can also act as a server—it can be accessed from other workstations on the network. Windows for Workgroups or Windows 95, 98, or 2000 network services connect non-dedicated servers in what is often called a peer-to-peer network.

A print server forwards files from workstations to a network printer. While waiting to be printed, the print server stores the files in a print queue. Files are forwarded to the network printer from the print queue in the order in which they are received.

An application server (Figure 7-15) is a cross between a dedicated server and a host. Like a host, it stores data and programs that can be accessed by workstations. Like a host, it performs some processing activities. Like a dedicated server, it sends actual data to workstations (unlike a host that only sends a screen image of the data.) Networks with application servers are sometimes called client/server networks.

A host computer provides connectivity to terminals, in which the host provides not only the programs and data files, but also performs all the processing tasks. This system of using a host computer to process the work of terminals is called a timesharing system. As the text points out, timesharing systems are usually distinguished from networks, although they are similar to networks in their function.
 

Software for Networks

Network operating systems include Novell NetWare, Banyan Vines, and LANtastic. Windows 95, 98, or 2000, Windows NT, Windows for Workgroups, UNIX, and OS/2 also offer networking capabilities.

Make sure you understand the relationship between server software and client software. Server software is installed on a server and functions to oversee operations. For example, mail server software manages mailboxes, maintains the master list of user IDs and passwords, and monitors usage. Client software is installed on workstations and provides the functions necessary for that workstation to participate in the activities supervised by the server. For example, a mail client provides a workstation with the means to access and log on to the mail program.  Groupware and workflow software are both examples of applications developing to meet the needs of users.

Issue: How Private Is E-Mail?

Read this section of your text and think about the security issues relating to email, at home or at work.

Email lab

Overview
Email is considered a basic communication medium today.  It is not hard to learn and learning some basic information can make your use of email more efficient and
productive.  This module presents information about the following areas related to email:
· Reading
· Composing
· Forwarding
· Replying
· Filtering
· Mailing lists
· Risks

Lecture Notes
Email Fundamentals
Email Servers and Clients
The basic client/server concept was explained in the "Networks" module.  This application may make the concept clearer.

Email Addresses
There is no standard format for the user name, other than it must be alphanumeric, and certain symbols and punctuation marks cannot be used.

Domain names may have more than three parts, but the names are limited to alphanumeric characters and periods cannot be used.

Upper- and lowercase letters don't matter generally in electronic mail addresses but can be used for readability.

Email Protocols
If you are using an email account set up for you by your employer or college, you will not be able to choose whether you use the POP3 or IMPA protocol.  If you
are choosing an ISP yourself, you may want to check on which protocol it uses.

Introducing Email Clients
Getting an Account
Many people have several email accounts, such as one for private, home use and one for business use.  There are several advantages to this, including
· being able to send mail even if one account is down.
· providing a way to separate business and personal mail.
· having greater privacy.
· maintaining a permanent personal address, even if you change jobs or leave school.

Setting Up Your Email Client
Of course, you must supply your password when you want to access your email account, but you can do this in two ways:  (1) by storing your password
permanently in memory, or (2) by typing it in each time you access email.  The first option is more convenient because when you access your email you will not be
asked to enter your password each time, but if you share a computer with anyone else, they can also access your email without a password.

The permanent storage option is available when you set up your email.  If you want to change that option, check the "options" menu in your email client program.

Exploring Your Email Client's Window
If you have trouble finding any of the features mentioned on your program, check the Help function.

Composing, Receiving, and Forwarding Mail
If an incorrect address is used, the message will bounce back to the sender in a message sent by the system's software. Reasons for returned mail include no such
user, unable to connect to remote system, and several problems due to either the local or remote system's mail software being configured incorrectly.  If you believe
you have sent your message correctly, try again, perhaps after a brief wait.

Sending mail to the user named "postmaster" at a particular domain name should forward the message to the human user responsible for the mail software on that
computer. Contacting the postmaster at a site can be useful if you have are having trouble with an electronic mail address at that site.

Some programs permit only one attachment per message, which can be inconvenient.

Managing Email
Because other people use filters, too, it is polite to use a descriptive subject line that will help your receivers sort your mail appropriately.

Also remember to delete email you have already read.  If you need a hard copy, print it out and then delete it.  This keeps your email account space on the server or
on your own machine from becoming clogged.

Mailing Lists
If email can be compared to a letter which goes to a specific recipient, mailing lists can be compared to a mass mailing sent to many recipients whose names are on a
mailing list.  An advantage of mailing lists is the ability to contact many people with similar interests at once.  This can be useful if you have a question about a
particular topic but don't know exactly whom to ask; you can ask a large number of people at once!

Information on many mailing lists can be found at various Web sites, including http://www.reference.com and http://www.liszt.com, as well as many others.

Using Email Responsibly
Using Email at Work
Many employers now have user agreements that employees sign which state what rights employees have and do not have with regard to the use of Internet services
at work.  Almost all of these agreements state that email is not private.  Even if your employer does not provide you with a user agreement, you must assume that
email is not private.

Backup Tapes
In addition to backup tapes, some email systems are set up so that email is deleted in two steps.  In the first step, email disappears from your mail received list, but is
still kept in a "recycle" area, like the recycle area on the Windows desktop.  Email in this area can be undeleted by the user, but it will still be available on backup
tapes.

Additional Risks
You can check out email hoaxes on the web, where a search for "email hoax" or "Internet hoax" will provide many sites. Of course, this will not cover all hoaxes but
will warn you of many, and also give you an idea of the type of messages to beware of.

How to Stay Out of Trouble
The most important principle is:  Be aware that email is not anonymous.

Overview
Computer networks, which link computer to exchange data or share research, achieve a synergy that gives the two computers working together the ability to do
more than the sum of what each of the two computers acting alone can do.  Networks achieve this extra productivity by reducing hardware costs, sharing data and
applications, and facilitating new kinds of collaborations between workers.

Computer networks may be LANs, MANs, or WANs.  Any of these require both physical connections and protocols that regulate the messages sent between each
machine.  Protocols are organized as a stack:  a series of hierarchical layers which pass messages down for processing before they are sent out over the network,
then back up in the receiving machine.  Ethernet is the mostly widely used LAN protocol, usually implemented in star topology using twisted-pair wiring and hubs.

Two kinds of transmission can occur over a network:
· circuit switching-messages are sent over a permanent, continuous, and therefore fast, pathway
· packet switching.-messages follow any of a variety of links to reach their destination

Types of LANs include:
· Peer-to-peer, in which no machine directs the total network
· Client/server, in which a server machine holds shared applications and data

WANs connect LANs, and can be used for transaction acquisition or to implement electronic data interchange (EDI).

Lecture Notes
Introducing Computer Networks:  Synergy at Work
What Is a Computer Network?
Networks are similar to mainframe systems with multiple user terminals in that many people can be working simultaneously.  However, the processing power of a
network is "distributed" among various computers, instead of being located in a single machine.

Hooking separate computers up through networks is also similar to hooking them up through data communications telephone lines; however, networks are usually
connected with greater bandwidth than regular telephone lines can provide.

Types of Computer Networks:  LANs and WANs
The distinction between these various types of networks is not clear-cut; the definitions may fade into each other.

Corporate networks may involve a number of LANs connected together into a WAN. LANs can also be connected directly to the Internet via a server or a
corporate Intranet, thus turning the Internet into the WAN.

Networking Synergies in a Nutshell
The first two advantages mentioned result in savings of money or time or both.  The last two have to do with providing greater access to resources of information or
people.

Network Fundamentals
Physical Media
A communications channel is a physical means of connecting the communicating computers so they can exchange the programs or data.  This means of connection,
or transmission, is commonly wires of one sort or another but may also take just about any form, from satellite and radio signals to infrared beams.

Switching and Routing Techniques
As packet-switched networks use new technologies to increase their speed, they may supplant circuit-switched networks.  One of these techniques, Asynchronous
Transfer Mode, or ATM, may become the next IP network standard carrier. ATM uses a network of links instead of a single end-to-end circuit, but within the
network it establishes a fixed route that reduces latency.  It is fast enough to support data, voice, and video traffic-such as multimedia-at extremely high transfer
rates.

Protocols
Protocols include baud rate and other important details which permit the two computers to exchange data. Most communications software programs have a feature
called a script file that allows you to create and store the settings for each individual system you communicate with, as well as each computer's telephone number and
the information you need to connect on-line.  In most cases where one computer is directly connected to another, their communications protocols must be set to
match.

Synchronizing two communicating computers is called handshaking.  Some communications applications are designed to work on many different brands of
computers to overcome hardware incompatibility and expand communications capabilities.

The concept of open vs. proprietary standards emerges here again, and can be compared to its appearance in earlier topics such as hardware connections and data
storage.

Network Layers
The logic behind dividing the job of preparing and sending messages between various protocol layers is that each layer can focus on one aspect of a complex job.
This makes the software of the layers easier to write, debug, and maintain.  In addition, it means that changes can be made to one layer of the protocol without
affecting the other layers, as long as the interface between them remains the same.

Local Area Networks (LANs):  Limited Reach, Fast Connections
Networking Hardware:  Network Interface Cards (NICs)
Some computers, such as Macintosh, are pre-wired to be able to hook up to a LAN.  If not, a NIC provides the additional circuitry needed.

Networking Software
In a peer-to-peer network, all computers run the same network software.  In a client/server network, all clients run the same network software, but the server runs a
different program because it has additional network responsibilities and capabilities.

Media
The choice of physical media depends on the distance between machines, the budget for the network, the transmission speed required, and other performance
needs.

LAN Topologies
Because only the machine with the token can send a message, and there is only one token in a network, two computers can never attempt to transmit messages at
the same time.  Therefore, no contention access is needed.

Ring topologies are also called "token ring" networks.  When capitalized, Token Ring refers to the specific ring network protocol developed by IBM.

Note that in the topology diagrams, any of the workstations depicted could also be another machine, such as a printer.

LAN Technologies
Lower layer protocols refer to those that actually transmit the message across the network, including verifying the connection between machines and actually sending
the data.  Ethernet is the most popular physical layer because it is relatively easy and inexpensive to implement, but it is still reasonably fast.

LAN Protocols
The TCP/IP protocol, most commonly associated with the Internet, is increasingly being used for other LANs.  This is especially convenient when the LAN will also
be connected to the Internet, as many LANs are.

Wide Area Networks (WANs):  Long-Haul Carriers
How WANs Work
When a business wants to use a WAN, it generally selects a service provider who sells it the right to hook up through a POP to its backbone.  Just as with telephone
service, companies can often choose among a variety of providers who compete for business.  The organization itself provides the physical connection to the POP,
and the quality and speed of that connection often determine the overall quality and speed of the organization's WAN access, since the backbone lines are always
very high speed.

How WANs Are Organized
The physical connections for a WAN (the PDNs) are owned by private, profit-making companies.  Two of the largest are owned by MCI (Tymnet) and Sprint
(Telenet), which use them for their voice telephone long-distance service as well as for WAN connections.

WAN Protocols
The advantage of point-to-point connection over packet switching is speed.

WAN Applications
Companies which use WANs for transaction acquisition can respond more quickly to sales trends by re-ordering inventory or moving it from one location to another
to meet demand.  Analysis of transactions can also be used to identify over- or under-performing stores and to predict income and cash flow.

An open standard for EDI called the X12 makes it easier for companies to ensure that their systems will be compatible.  As more and more large companies ask the
smaller companies that supply them to adopt EDI, the small companies will benefit, too, since it ensures that they will receive payment quickly and automatically.
These financial benefits may outweigh the startup costs associated with EDI.

EDI is being used by healthcare providers and insurers to transmit treatment and payment information, for travel companies and customers to arrange and pay for
bookings, and for automated tax reporting.

As you read messages you will probably be puzzled by the abbreviations or
acronyms you'll see.  The following lists some of the more frequently used
acronyms.

FB         Files Busy
Sysop      System Operator; people who manage the forum
BRB        Be right back
BTW        By the way
CP         Copy protection
FUBAR      "Fouled" up beyond all recognition
FWIW       For what it's worth
FYI        For your information
gr&d       Grinning, running, and ducking
IAE        In any event
IMO        In my opinion
IMHO       In my humble opinion
IOW        In other words
OIC        Oh, I see
OTOH       On the other hand
PITA       Pain in the ...
ROTFL      Rolling on the floor, laughing
RSN        Real soon now
RTFM       Read the [fine] manual (or message)
SNAFU      Situation normal, all "fixed" up
TIA        Thanks in advance
WYSIWYG    What you see is what you get
 

Occasionally you'll see little cryptic codes in messages.  There are called
'emoticons', and are used to express the emotions of normal voice
communication -- for example, to indicate that the "snide" comment you just
read was really a joke.  The following list has been compiled from ten
years of reading messages on bulletin boards and CompuServe forums.

     emoticon (noun).  A figure created with the symbols on the keyboard.
Read with the head tilted to the left (the : represents the the eyes and
the - the nose.  Used to convey the spirit in which a line of text is
typed.

Emoticon     Meaning
--------     -------
:-i          Semi-Smiley
:-t          User is cross
:-           User is male
:-?          User is smoking a pipe
:-=)         Older user with mustache ['calendarly advantaged'
- please]
:-\         Undecided user
:-p          User is sticking their tongue out (at you!)
:-D          User talks too much
:-#          User's lips are sealed.
:-s          User after a BIZARRE comment
:-o          User is surprised
:-{         User has a large mustache
:-|          No expression face, 'that comment doesn't phase
me'
:-&          User is tongue-tied
:-(          Sad
:->          Hey hey
:-7          User after a wry statement
:-@          User face screaming
:-)          Humor (or smiley)
:-c          Bummed out Smiley
:-x          "my lips are sealed" Smiley
:-e          Disappointed Smiley
:-<          Real sad Smiley
:-I          Hmm
:-O          Uh oh
::-)         User wears glasses
:<|          User attends an Ivy League school
:>           Midget Smiley
;-)          Winking Smiley
(-:          User is left-handed
(:-)         Smiley big-face
(:-(         unSmiley frowning
,-}         Wry and winking
<:I          Dunce
>-           Female
>:-<         Mad
#-)          User partied all night
|-O          Birth
|-)          Hee hee
|-D          Ho ho
|-)          User is asleep (boredom)
|-P          Yuk
8-|          Suspense
P-)          User is getting fresh
[:-)         User is listening to Walkman radio
[:|]         User is a robot

Also
<g>          Grin
<<g>>        Big grin

Have fun with these and use them regularly.  You will be understood much easier by your fellow classmates and instructors.