This document discusses factors to consider when designing a local area network (LAN), including network scale, networking technologies, and physical cables. It provides guidelines for determining the appropriate network scale based on the number of users, physical layout, software needs, and budget. Network scales discussed include peer networks for 2-10 users, single-server networks for 10-50 users, multiserver networks for 50-250 users, high-speed backbone networks for 250-1000 users, and enterprise networks for 1000+ users. Various networking technologies are also outlined such as Ethernet, Fast Ethernet, Token Ring, FDDI, Fiber Channel, ATM, and wireless options. Finally, physical cable types like twisted pair, coax, fiber,

1. Designing Local Area
Network
Network Scale/Networking Technologies/
Physical Cables

2. Network Scale
• Do you need:
– Large or Complex Network?
– No server, One server, or many servers?
– Special networking equipments, such as
bridges, routers, and backbones?
– Do the users of your network require high
bandwidth and therefore a fast (and
expensive) network?

3. Network Scale
• You need answer of these questions:
– How many client computers do you
have?
– How far apart are the computers?
– What software are you using?
– What software will you use?
– What special requirements do you have?
– How much you can spend?

4. How Many Client Computers?
Peer Network (2 – 10 Users)
Peer networks are
good for:
– File Sharing
– Printer Sharing
– E-Mail
– Tight budgets
– Easy installation
They are not good
for:
– Security
– Backup
– Organization of data
– Database
applications
– Large networks
– Simple
administration
– Internet/WAN access

5. Peer network (2 – 10 Users)
This network requires Operating system such
as Windows for workgroups, Windows 95,
Macintosh, OS/2 and Novell DOS

6. Single-Server Netwrok(10 – 50 Users)
Single-Server networks
are good for:
– Centralized File Services
– Network Printing
– E-Mail
– Workflow and groupware
– Easy installation
– Login security
– Archiving
– Organizing data
– Simple administration
– Internet/WAN access
They are not good for:
– Application serving
– Distributed organizations
– Large organization

7. Single-Server Network (10 – 50 Users)
This network requires network operating
systems such as Windows NT, Netware, or
OS/2 Server

8. Multiserver Networks(50 – 250 Users)
Multiserver networks
are good for:
– Centralized File
Services
– Network Printing
– E-Mail
– Workflow and
groupware
– Login security
– Application services
– Large databases
– Internet/WAN access
They are not good
for:
– Tight budgets
– Easy installation
– Organizing data
– Simple
administration

9. Multiserver Networks (50 – 250 Users)
This network requires network operating
systems such as Windows NT, Netware, or
OS/2 Server

10. Multiserver High-Speed Backbone
Network (250 – 1000 Users)
High speed backbone
networks are good for:
– Centralized File
Services
– Network Printing
– E-Mail
– Workflow and
groupware
– Login security
– Application services
– Client-server
database
– Internet/WAN access
They are not good for:
– Tight budgets
– Easy installation
– Organizing data
– Speed

11. Enterprise Network (1000 + Users)
Enterprise networks are
good for:
– Network Printing
– E-Mail
– Workflow and
groupware
– Login security
– Application services
– Client-server
database
– Internet access
They are not good for:
– Tight budgets
– Easy installation
– Centralized file
services
– Organizing data
– Speed

12. Enterprise network
FDDI ring FDDI ring
Engineering
Operation
Development
Research
Finance
Marketing
Sales
Administration
F & A Building R & D Building

13. Network Scale
• How Far Apart Are the Computers?
• What Software Are You Using?
– Word Processing and Spreadsheet
– Graphics and CAD
– Database Software
• What Software will You Use?
– E-Mail
– Internet Service
– Groupware
– Video Teleconferencing

14. Network Scale
• What Special Requirements Do You
Have?
– Do you have some special need of
security on your network? Are any of
your computers more than 100 meters
from where you will locate your Hub?
Have there been any problems with
electrical interferences? Etc.
• How Much Can You Spend?

15. Networking Technologies
• Ethernet
– There is no guarantee that a computer will
ever be able to transmit data in a heavily
loaded network
– A computer only has to wait for silence before
transmitting.
– Keeps about 30 clients per network segment
• Fast Ethernet
– Fast Ethernet is more expensive than Ethernet
and 10 times faster than Ethernet.

16. Networking Technologies
• Token Ring
– All computers will eventually get to transmit
data, no matter how loaded the network is.
– All computers will suffer some delay before
being able to transmit white they wait for the
token.
– Token Ring is a contemporary of Ethernet, but
because the electronics required to control
the network process are inherently more
costly, it never caught on as well as Ethernet.

17. Networking Technologies
• FDDI (Fiber Distribution Data
Interface)
– FDDI is a token-passing ring network
that operates at 100 Mbps over two-
counter-rotating fiber optic cable rings.
– FDDI is a fast fiber version of Token Ring
and has been the choice for high speed
backbones.
– FDDI rings can be quite large, up to
about 13 Kilometers between devices
with single mode fiber.

18. Networking Technologies
• Fiber Channel
– Fiber Channel is a large high-speed
backbone network technology that
connects all the terminals,
microcomputers, mainframes, local
area networks, and other
communications equipment.
– It currently operates at very high speeds
and will eventually make a good choice
for backbone connectivity in very large
networks.

19. Networking Technologies
• ATM
– Asynchronous Transfer Mode (ATM) (a.k.a. cell
relay) is a technology originally designed for use
in wide area networks that is now often used in
backbone networks.
– ATM backbone switches typically provide point-
to-point full duplex circuits at 155 Mbps (total of
310 Mbps).
– ATM uses a very different type of protocol than
traditional LANs. It has a small 53-byte fixed
length packet and is connection-oriented.
Ethernet and token ring use larger variable
length packets and are typically connectionless.

20. Physical Cables
• Twisted Pair (UTP, STP)
– COST PER LOCATION: Cat 5 UTP Moderate Cat 5
STP Expensive
– DISTANCE LIMITATION: Cat 5 100 meters No
more than 80 meters should be permanently
installed between wall outlet and the patch
panel in the computer room.
– OTHER LIMITATIONS: Cat 5 UTP is susceptible to
interference from sources that generate EMI
such as Motors HVAC unit, fluorescent lights etc.
– BANDWIDTH: Cat 5 100Mbps

21. Physical Cables
• Coax
– COST PER LOCATION: Thinnet coaxial cable-
lowest cost, Thicknet coaxial cable cost is
double than Thinnet.
– DISTANCE LIMITATION: Thinnet – 185 meters,
Thicknet - 500 meters per segment.
– OTHER LIMITATIONS: Because they are bus
networks, the path of the installed cable must
match the locations of the existing computers.
– BANDWIDTH: The useful bandwidth of coaxial
cabling is 10Mbps.

22. Physical Cables
• Fiber
– Although many types of optical fibers are available, but most
network devices using only two types multi-mode with a core
diameter 62.5 micron and single-mode with a core diameter
8.3 micron.
– COST PER LOCATION: Very Expensive.
– DISTANCE LIMITATION: Multi-mode fiber – 2000 meters when
using 10BaseFL and 400 meters when using Fast Ethernet
100BaseF. Modern cable bandwidth 622Mbps at 1000 meters.
That bandwidth can be doubled each time the cable distance
is halved.
– OTHER LIMITATIONS: Since fiber is immune to EMI, and
because it is nearly impossible to tap. It should be handled
with care during installation.
– BANDWIDTH: The useful bandwidth of optical fiber depends
on the network standard. Single-mode FO can carry any
network signal at any speed, and multi-mode FO can carry all
current network signals within building.

23. Physical Cables
• Wireless Radio
– Wireless Radio is very expensive, but it
can be extremely useful in situations
where running cable is prohibitively
expensive or not possible. The different
types of wireless radio solutions in
existence all serve different needs and
different ranges. The frequency ranging
from 900MHz spread spectrum to 23GHz
microwave.

24. Physical Cables
• Wireless IR
– Wireless Infrared is broken down into local area and point-
to-point solutions. All infrared solutions require a clear line
of sight and are greatly impacted by weather, such as rain or
fog, unless they are indoor-only solutions.
– Following is description of three types Infrared solutions:
– Short-distance infra-building LED: These devices are
generally aimed at central Infrared Hub that can be
mounted on a ceiling for total room coverage.
– Medium-distance infra-building LED: These devices must be
aimed in each others general direction because they are
highly focused and are limited to fewer than 500 meters.
– Long-distance point-to-point LD: It is laser diode solutions
can operate at full network speed for a verity of protocols
up to 155Mbps – 500 meters and at 20Mbps or less up to 1200
meters.