datapro :: Datapro Managing LANs Volume 2 1992

598 Pages·1992·81.2 MB·English

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Managing
LANs
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LANs
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Contents Volume 2
February 1992
· Managing LANs
~t
(Formerly Datapro Management of Microcomputer Systems
Report
Number Report
Selection & Acquisition
5010 Criteria for LAN Selection
5020 Choosing a NOS: Banyan, Microsoft, and Novell
5034 Selecting a 486
5036 Selecting Mass Storage Devices
5050 Contracting Fundamentals
5054 Evaluating Potential Consultants
5058 Buying Third-Party Network Support
Installation & Maintenance
5410 Installing a LAN
5412 Your First LAN: Do It Yourself?
5413 Ethernet Wiring Made Simple
5415 A Guide to Installing Windows on a NetWare LAN
5420 Installing Modems and Software
5445 Turning an Older PC into a 386 CPU-Based Machine
5450 PC Maintenance Guidelines
Operations Management
5610 A Guide to Keeping LANs Running Smoothly
5611 Control Change From the Ground Up
5612 LAN Administration: A New Job Function
5613 LANs by the Book
5615 Training Network Users
5618 LAN Training Sources
5620 LAN Management Issues
5622 Establishing a LAN Dossier
5625 Network Analysis: Ten Steps to Fine-Tuning Network Performance
5630 Fault-Tolerant LANs
5640 The LAN Diagnostic Process
5650 Managing LAN-Based Services
5660 Server Backup
Security
5810 Planning for Microcomputer Security
5820 Developing Microcomputer Security Awareness
5822 A Sample Microcomputer Security Policy
5830 Microcomputer Data Security Solutions
5835 Security and Integrity in Micro-Mainframe Networks
5840 Protecting Against Computer Viruses
5842 LAN Security
5845 Developing a LAN Virus Protection Strategy
5850 Application Layer Network Security
5860 Microcomputer Encryption and Access Control
Technology Overviews
Local Area Networks
7210 An Overview of Local Area Networks
7220 An Overview of Bridges, Routers, and Gateways
7230 An Overview of Communications Servers
7240 An Overview of Network Management
Computer Systems
7410 An Overview of Microcomputers
7420 An Overview of Portable Microcomputers
7422 Notebook Computers
7430 An Overview of UNIX Microprocessors
7440 An Overview of Superservers
7450 An Overview of Database Servers
7460 An Overview of Technical Workstations
Software
7610 The Evolution of LAN Operating Systems
7620 An Overview of PC-to-Host Communications Products
7625 An Overview of Asychronous Communications Software
7627 Document Management Software for Networks
© 1992 McGraw-Hill, Incorporated DATAPRO
Datapro Information Services Group
Delran NJ 08075 USA Reproduction Prohibited FEBRUARY 1992
2 Volume2 Contents
Report
Number Report
7640 An Overview of Microcomputer Operating Systems
7645 Multiprocessing Network Operating Systems
7646 An Overview of Multiuser DOS Systems
7648 An Overview of Object-Oriented Programming
7658 An Introduction to Windows
7660 An Overview of Environments and GUls
7662 An Overview of Utility Software
7668 An Overview of Language Compilers and Interpreters
7680 An Overview of Electronic Mail
Peripherals
7810 An Overview of Mass Storage
7812 An Overview of Optical Storage
7820 An Overview of Displays
7825 An Overview of Scanners
7830 An Overview of Expansion Cards
7832 An Overview of Modems
7835 An Overview of PC-to-Fax Boards
7840 Microcomputer Sound Capabilities
7842 PC Mice
7850 An Overview of Laser Printers
7852 An Overview of Dot Matrix and Ink Jet Printers
Architectures & Standards
Architectures
8210 Microcomputer Bus Architecture
8215 Extended Industry Standard Architecture (EISA)
Standards
8410 Overview of Data Communications Standards
8420 IEEE 802 Standards for Local Area Networking
8430 ANSI Fiber Distributed Data Interface (FDDI) Standards
8432 Introduction to FDDl-11
8440 Simple Network Management Protocol (SNMP)
8442 Dueling Protocols: SNMP vs. CMIP
8460 Modem Standards
© 1992 McGraw-Hill. Incorporated
Datapro Information Services Group
FEBRUARY 1992 Delran NJ 08075 USA Reproduction Prohibited
DATAPRO Managing LANs 5010 1
Selection & Acquisition
Criteria for LAN
Selection
In this report: Datapro Summary
All LAN vendors claim to offer the perfect solution for your networking needs. The
General Selection
range of hardware and software offered is nearly mind-boggling. However, by fol
Criteria ................................ 4
lowing a structured set of LAN guidelines, the processes of planning a LAN instal
lation and selecting the proper equipment become somewhat clearer.
Specific LAN
Requirements ..................... 5
Type of Vendor ................... 8
Planning a System several ways to improve the productivity of
your information workers. But first, you
In this section, 1 we look at the process of must be more specific. You must be able to
translating the information needs of your answer in quantitative terms the question:
organization into an overall plan for an of What is the information movement and
fice automation system. The process has processing system supposed to do?
three steps: (1) Define objectives, (2) De It is best to begin by defining some pro
scribe the system, and (3) Determine com ductivity goals. The goals must be quantita
munications needs. tive and must relate to information cre
As we proceed, you will see that the dis ation, storage, transfer, and reporting.
cussion is based on determining your data General categories include timeliness, re
processing equipment needs. The focus of sponsiveness, convenience, and workload.
this report is on local area networks The goals you set must be based on the sit
purchasing and incorporating them in your uation you have today and where you think
organization. Because the principles are improvements are needed. For example,
general, however, they are also useful in the suppose it is important to get reports or
broader context that includes devices that documents quickly; also suppose that these
hook into the network. documents are usually revised because of
an internal review cycle. A productivity
Define Objectives
goal would be to reduce revision typing
The objectives for the installation or modi time. Another example: Only certain key
fication of an office automation system professionals can produce briefing materi
must relate to the information products of
als or reports, and this is draining too much
the organization. These products are the of their time. A corresponding productivity
items used to gather, store, present, and an
goal would be to reduce the effort required
alyze information needed for the operation of the professional staff during the informa
of the organization. Table 1 provides a rep tion creation phase.
resentative list of such products. These goals should be as quantitative as
By considering how these products are possible. Think in terms of how many doc
produced and used, you can probably see uments need to be produced by how many
people, the time it should take to prepare
charts, and so forth.
At this stage, don't limit the number of
This Datapro report is a reprint of Chapter 9,
things you look at. Consider all your infor
"LAN Selection," pp. 291-309, from The Busi
mation products. Table 1 can be used as a
ness Guide to Local Area Networks by William
Stallings, Ph.D. Copyright© 1990 by Howard checklist. Consider the feasibility and sig
W. Sams & Company. Reprinted with permis nificance of your goals. Propose goals in
sion.
© 1992 McGraw-Hiii. Incorporated. Reproduction Prohibited. JANUARY 1992
Datapro Information Services Group. Delran NJ 08075 USA
2 5010 Criteria for LAN Managing LANs
Selection
Selection & Acquisition
Forms Data item description
Table 1. Typical List of Information
Inspection and acceptance document
Products Military order
Personnel action request
Position description
Printing request
Correspondence Letter Purchase request
Memorandum Report of survey
Message Security classification guide
Time card
Reports Budget initiatives Travel request
Case study Work order request
Fiscal
Management Services Electronic bulletin board
Material deficiency Information tracking
Personnel Response to inquiry
Project status Technical assistance
Technical Reviews and Business strategy panel meeting
Trip Briefings Command or senior officer briefing
Weekly activities Division advisory group (DAG) review
Documents A76 cost comparison EEO review
Action item list Executive management review (EMA)
Administrative notice Financial management board review
Change order Internal management review
Configuration change status report Periodic program review
Contract funds status report (CFSR) Program management review (PMR)
Contract management systems checklist Quarterly financial review
Cost estimate Scientific advisory board (SAB) meeting
Data management report Audiovisual Aids Briefing board
Delivery order Briefing text
Engineering change proposal (ECP) Graphic aid
Environmental assessment Vugraph
Independent cost analysis (ICA) 35mm slide
Invitation for bid
Integrated logistics support plan (ILSP)
From these product goals, it is possible to derive more
Life-cycle cost study
Military construction program reporting specific system requirements that will guide product selec
Procurement directive tion. Table 3 lists examples of system requirements for the
Procurement plan product goals cited in Table 2.
Program management directive
Program management plan Describe the System
Quarterly resources report Now you have some specific goals. The next thing to do is
Request for proposal (RFP) to list some options for moving closer to achieving those
Sole source justification
goals. As a manager, you know that not all improvements
Staff meeting agenda (and report)
come from buying equipment. Consider three interrelated
Statement of work (SOW)
System safety program plan methods of achieving improvement: organizational, pro
Technical evaluation and report cedural, and technological. Perhaps things are being done
Training plan by the wrong group (organizational), or in the wrong way
(procedural), or with inadequate equipment (technologi
cal). Table 4 gives some idea of how these three factors can
be used to improve productivity.
practical areas where there is room for significant im These factors affect each other. A technological change
provement. If certain activities are already accomplished may dictate an organizational change. For example, if it
efficiently, leave them be. becomes quick and easy to produce charts using presenta
One particularly effective way of formulating goals is to tion software on a personal computer, perhaps the charts
survey the concerns of senior management. This has the should be produced by the professional staff rather than a
added benefit of creating a climate in which reasonable support group.
and effective improvements will more readily receive Our focus is technological. We need to determine what
management approval. For certain key information prod additional equipment can be beneficial. We can group our
ucts, determine the concerns that management considers options into four categories: input, production, output,
important. Table 2 presents a list of possible management and distribution. Table 5 lists representative equipment in
concerns and goals. For example, if timeliness was identi each category, together with a description of benefits and
fied as a primary concern for a key product, the suggested drawbacks and an estimate of productivity improvement.
product goal may be to reduce delays in the preparation This will allow you to assess the impact of various pieces of
and distribution of information. If responsiveness was equipment.
cited as a primary concern, the suggested product goal may
be to reduce the amount of "telephone tag" among profes Determine Communications Needs
sionals. You know what information equipment your organization
has. You have tentatively decided what the creation, pro
cessing, and storage equipment should achieve in terms of
JANUARY 1992 © 1992 McGraw-Hill, Incorporated. Reproduction Prohibited.
Datapro Information Services Group. Delran NJ 08075 USA
Managing LANs Criteria for LAN 5010 3
Selection
Selection & Acquisition
( kind of workload generated by various devices on a local
Figure 1.
area network. These estimates were prepared by the IEEE
Types ofI nformation Exchange
802 standards committee.
It is useful at this point to know the nature of the infor
mation exchanges that will take place. We can group these
File Transfer
exchanges into two broad categories: file transfer and
transaction (Figure l ). A file transfer is primarily a one
' way movement of data, such as the transfer of a word pro
cessing file to a printer or an image to a facsimile machine.
Transmission of record Transmission of Transactions are typically responses to inquiries or re
or print line acknowledgment quests for data. In the first case, you are more concerned
with throughput: the amount of data to be transferred in a
given time. In the second case, you are more concerned
Throughput = Total records, print lines, etc.
Total transmission time with response time: how long it takes to get an item after it
is requested.
Next, you need to look at the total capacity demand. On
Transadion average, how many information exchanges will take place
EJ
at a time? What is the peak? For file transfers, you can now
~EJIR2
add up the individual loads to get an idea of the overall
throughput demand on the network. For transactions, it is
~
Response Time better to express your needs in terms of a performance
goal. For example, for a certain type of transaction, you
might specify that you want 90 percent of the transaction
to have a response within three seconds.
Finally, you need to look at future growth. If your orga
productivity. The last element is the information move nization is growing, someday you will want to buy more
ment equipment-the local area network. To be truly ef equipment. Your total file size will grow. You may add
fective and efficient, your collection of equipment must new functions to the network. The network should be de
become a system capable of moving information as well as signed to accommodate growth. Given the capabilities of
creating, processing, and storing it. The process of select today's LANs, you should be able to install a network now
ing a LAN or a set of LANs begins with a specification of that will not need to be replaced in the near future. Fur
requirements. These boil down to two considerations: thermore, with tiered LANs, any future growth can be ab
compatibility and capacity. sorbed partly by an additional load on existing LANs and
Compatibility is the easier of the two to specify, but the partly by the addition of new LANs.
harder to achieve. You simply need to determine which
devices need to exchange data. For example, if you intend
to combine data from an accounting system with text from
a word processor, there must be an electrical path from the
accounting system to the word processor, and the word
processor must be able to accept and process the received Table 2. Key Product Goals
data.
The second part, capacity, is more difficult to pin down
but, paradoxically, easier to satisfy. In fact, you don't need
to be very accurate in estimating capacity. LANs have tre Management Desired Goals
mendous capacity; this is one of their chief advantages. Concern
For example, the National Institute of Standards and Timeliness Reduce preparation delays
Technology has a LAN that uses a baseband cable, with a Reduce distribution delays
I-Mbps data rate and CSMA/CD protocol. By today's Responsiveness Reduce "telephone tag"
standards, this is a system with modest capacity and per Improve query response time
formance characteristics. Over 200 devices in twenty Reduce float
buildings are connected, with an overall extent of 1.5 kilo
Convenience Improve information input/output
meters. This is not a prototype or experimental system; it
methods
is in daily use by a staff with data processing needs as least
as great as those of the average office. Yet, the utilization Efficient use of Increase office automation system usage
resources Improve training
of the network's information movement capacity is under
Reduce user resistance
2 percent!
So, for this part, don't worry about making precise esti Organizational Reduce need for reprocessing
mates. To determine the required LAN capacity, all that a effectiveness Reduce duplication of effort
Provide access to organizational
network designer needs is a general idea of the workload
database
and performance demands of the network. Table 6 sum
marizes the information needed to design a network. Managerial Improve decision-making process
Again, you do not need exact numbers for this checklist; effectiveness Improve quality of presentation
rough estimates will be sufficient.
Cost of labor and Reduce costs, waste, and overtime
First, estimate the workload that the various devices on overhead
the LAN will generate. Table 7 will give you an idea of the
© 1992 McGraw-Hill, Incorporated. Reproduction Prohibited. JANUARY 1992
Datapro Information Services Group. Delran NJ 08075 USA
4 5010 Criteria for LAN Managing LANs
Selection
Selection & Acquisition
Table 3. Examples of System General Selection Criteria
Requirements Having gone through the process of planning a system, you
can translate your needs into a statement of network re
quirements. The preceding section developed your re
quirements from a user or application point of view. That
Produce documents locally should help you answer the question: What is the system
Access or download data from organizational databases supposed to do? The next step is to answer the question:
What features must the local area network have to meet
Edit and revise documents easily
my system requirements?
Transfer documents among offices within and outside the Keep in mind two points as you go through the rest of
organization this report. First, we are not trying to teach you how to
Perform interactive file queries by office users design your own network; we just want you to be able to
hold your own in dealing with experts and would-be ex
Send and receive messages electronically
perts. Second, the emphasis is still on what the network
Produce compound documents (text, spreadsheets, and will do, not how the network will do it. The what is the
graphics) customer's responsibility; the how is the vendor's respon
sibility. Don't make the mistake of precluding a cost
Perform "what if" scenarios quickly
effective solution by telling the vendor how to do his or her
Conferencing (by computer and telephone) job. In this section, we give you some general selection cri
Output presentation and letter quality documents teria to keep in mind as you consider various vendors (Ta
ble 8). These are the features you should look for and com
Transfer word processing skills across offices
pare.
Send and receive documents by facsimile The first criterion is cost. If the cost exceeds what you
perceive as the expected savings in increased productivity,
Use electronic calendars and scheduling tools
the system isn't worth the price.
Integrated, easy-to-use office automation systems
Second, the system has to meet the requirements you
Train users to realize full capabilities of systems have established. Although there are always compromises,
the system must match the basic requirements. Related to
Develop policies and procedures for system usage,
this is the concept that the network should be expandable
information storage and disposition, security, and system
with only incremental cost. That is, expanding the system
operations
later should not be overly expensive or complicated. This
Streamline paper handling allows you to start small, at low risk, and gradually expand
Enable the staff to be responsible for administrative and the network to meet more of your requirements.
operational needs of office information resources Along with expandability, your system needs reliability.
The system should be designed to prevent total network
Table 4. System Design Model
Organizational Procedural Technological
Work group A will be responsible for All budget computations will be Personal computers
initial compilation of budget data performed using spreadsheet
software Software applications including: word
Work group B will be responsible for processing, spreadsheet, communications,
researching program data All intraoffice memos will be sent and database management systems
by electronic mail
Work group C will replace work group Laser printers and letter quality printers
A in the review of key products relating Key products will be developed on
to grant applications personal computers and electronically Electronic typewriter with OCR fonts
transferred to support personnel for
Professional staff in work group C who final processing Minicomputer
are responsible for budget compilation
will be reassigned to work group A Support staff will be designated as Microfilm reader-printer
product distributors
Modems
Final drafts will be microfilmed rather
than filed Electronic messaging system
Training classes will be available to Local area network and software support
all personnel
Policies on usage, information
management (including storage and
disposition), operation of systems, and
security will be updated semiannually
JANUARY 1992 © 1992 McGraw-Hill, Incorporated. Reproduction Prohibited.
Datapro Information Services Group. Delran NJ 08075 USA
Managing LANs Criteria for LAN 5010 5
Selection
Selection & Acquisition
failure. In addition, the network should be capable of in software needed for full compatibility. Issues of communi
(
terfacing with equipment supplied by more than one ven cations architecture and server software need to be ad
dor. We explore this issue at the end of this report. dressed.
You want a network that is easy to install, maintain, Security and privacy are a concern. When multiple user
and occasionally reconfigure. Flexibility is important. You groups have access to the network, the network must pro
want to be able to connect your equipment to the network vide means for isolating information and restricting access
easily, with no impact on hardware or software. to it. Similarly, unauthorized users should be kept off the
Finally, there are software issues, such as the need for network altogether.
servers, security, and network management. These can be Another concern is remote communications. You may
supplied in an integrated fashion with the LAN or pur want to link two installations by a satellite data channel
chased separately. The former solution may mean that you and routers or bridges. Or you may want to augment your
have fewer vendors to deal with and simpler training. The in-house processing capability with outside services, avail
latter solution may give you more flexibility in your able over a packet-switching network such as Telenet or
choices. Tymenet. You may also want to provide dial-in ports on a
modem server so that personnel who are traveling can en
ter the network from anywhere in the country.
Specific LAN Requirements
Finally, one service is absolutely essential to the suc
Let us consider specifically what you will require of a net cessful operation of a network: network management.
work. Much of the information was discussed in the begin Some level of monitoring and control is needed.
ning of the report, and a knowledgeable consultant or ven
dor can work with that sort of information. This section Traffic
will give you a better idea of what to ask for, a checklist of The network must have the capability to meet the expected
what has to be provided. traffic load. This was explored previously in this report.
Throughput and response-time requirements must be
We can group our concerns into five areas: specified. Especially important are peak-load require
ments.
• Services
How does this translate to a specific LAN capacity? A
• Traffic good guideline is to estimate the total load and then pur
chase a LAN with at least 10 times that capacity. That fig
• Reliability
ure may seem excessive, but it is not. First, you are more
•Growth likely to underestimate than overestimate your capacity
• Installation, maintenance, and training needs. Second, demand will grow.
Services Reliability
The functions performed by the network that are most vis The network must be available to its users a very high per
ible to users and management are referred to as network centage of the time: there must be a long period between
services.2 A primary consideration in developing network component or network failure, and a minimal period be
services is the physical network environment. Is the net fore repairs are completed. A useful measure of reliability
work all in one building or spread over several? If the lat is mean time between failure (MTBF). For the transmis
ter, must the buildings be linked together? Where is the sion medium, which includes the cable, amplifiers, taps,
equipment located? What space is available for network and so on, an MTBF of 175,000 hours is reasonable. For
components? What false ceilings, conduits, and buried ca intelligent network devices, such as bridges or network in
ble runs exist for wiring? Are there any special environ terface units (NIUs), an MTBF of 30,000 hours is a good
mental problems? goal.
Next, what type of equipment will be supported? This Another aspect of reliability is the error rate of trans
consideration leads to the question of interfaces. Some de mitted information. This is usually expressed as the rate of
vices, such as terminals, may require a standardized com bit errors. There are two types of error rates to be con
munications interface, such as RS-232C. Others, such as cerned about: undetected and detected. An undetected er
personal computers and workstations, may interface to the ror is discovered the hard way: The numbers didn't bal
network through a communications board mounted in the ance, or someone didn't get a paycheck. Detected errors
chassis of the computer. Only resources that need to be are those discovered by the communications logic and au
shared should be on the network. For example, ify ou have tomatically corrected, usually through a retransmission.
a special plotter that must be driven by the software in one Undetected errors are obviously unacceptable, and the
and only one computer, hook the plotter to that communications software used across a LAN should be
computer-don't make them communicate over the net able to prevent these, or at least reduce them to an accept
work. able minimum. Detected errors are not as bad, but they do
There is also the software interface to consider. For ex cause unnecessary network overhead.
ample, what protocols are provided to allow terminals to Good reliability values are a detected-error rate of l bit
communicate with a variety of computers? in 109 and an undetected-error rate of l bit in 1012•
Next, consider the type of information to be transmit Detected-error rates are easily monitored. Undetected
ted over the network. This is the whole point of having a error rates must be estimated from off-line tests using arti
network. For data, your primary concern is compatibility. ficial traffic.
Given the types of equipment you will have and the types
of data to be transmitted, the network and the software in
the attached devices must provide the communications
© 1992 McGraw-Hill, Incorporated. Reproduction Prohibited. JANUARY 1992
Datapro Information Services Group. Delran NJ 08075 USA
6 5010 Criteria for LAN Managing LANs
Selection
Selection & Acquisition
Table 5. Productivity Citings for Representative Equipment Types
Input Phase
Equipment Benefits Drawbacks Cltings
Dictation Input is four times faster than Clarity of thought and expression 6.25-12% time savings/day
longhand is required Herbert M. Kaplan, Words,
International Word Processing
Transcription is twice as fast as Pre-organization of material by Association, June-July 1980, pp.
reading longhand or shorthand dictator is necessary 40-43
Any secretary can transcribe Many originators resist dictation
Priority work can be handled
24-hour Input is allowed
Electronic typewriter with OCR Correction time is reduced No text editing is possible See optical character recognition
font citing
Input by OCR reader into No storage capacity is available
production equipment is
possible Input into production equipment
is off-line
Optical character recognition Every typewriter with an OCR Generally only a limited number 600% increase in throughput,
font can be a low-level Input of fonts can be read Compuscan sales literature,
device for text editing and data AW-58-018.0
manipulation Scanning errors are possible
Re-keyboarding of input text and Specific input formats may be
data Is eliminated required
Production equipment is freed Accuracy depends upon ribbon,
for word or data processing strike, paper, and other variables
Work distribution is enhanced
Personal (professional) terminal Data entry, access, and retrieval Training is required 50% productivity rise, Emerick G.
time can be reduced Zouks, Business Week, Aprll 7,
CPU downtime can affect the 1980, pp. 81-82
Paper and supplies can be saved use of the terminal
through electronic capture of
keystrokes Response degradation may occur
during peak periods
Can be expanded, reconfigured,
or networked as applications
expand and new requirements
evolve
Growth placement of all cable (including taps, splitters, and ampli
No matter how good your analysis of current require fiers) and wiring and the location of all network compo
ments, you cannot expect to satisfy all your local area net nents. The vendor must assure that the layout meets all fire
work needs once and for all. For example, you may antici and building codes.
pate that your word processing staff will double in the next Following installation, maintenance of the network is
three years. You should be able to attach these additional an ongoing responsibility, divided between you and the
stations to the network easily, with no disruption of net vendor. How that responsibility is divided varies; the next
work operations. Also, the network must have the capabil few paragraphs present an example.
ity to handle the increased traffic generated by the new The customer has the following responsibilities for the
stations. network hardware:
New types of applications or devices might be added to • Maintain a permanent survey of the network through the
the network (for example, a facsimile machine). This will use of logging files and traffic statistics.
require new protocols. If such growth is to be possible, the
• When a problem occurs, perform diagnostics to attempt
network hardware and software must be capable of easily
to localize the fault, using vendor-supplied test equip
accommodating new protocols. This is most easily done
ment and diagnostic software.
with an OSI-based architecture because virtually all work
on new protocols is in that framework. • When the fault is localized, reconfigure the network, if
possible, to provide continued service.
Installation, Maintenance, and Training
• When the vendor has corrected a failure, assist the ven
The preceding criteria had to do with the capability and
dor in checking the network.
capacity of the network. This subsection speaks to an
equally important consideration: the service provided by
Customer personnel will require training from the vendor
the vendor. First, the vendor must plan, with your cooper
to perform these tasks.
ation, the layout of the network. This includes the physical
JANUARY 1992 © 1992 McGraw-Hill, Incorporated. Reproduc.1kln Prohib1ted.
Datapro Information Services Group. Delran NJ 08075 USA