1. Wireless network Usually use Radio Frequency (RF) technology Adv :
transmit and receive data over the air
Adv :
providing all the features of wired LAN
without the limitations of a cable
Disadv :
lower transmission speed
higher cost (when c.f. wired network)

2. Wireless LAN usually used in complement with a wired LAN
becoming an alternative for wired LAN
by means of an access point (AP)
a device that transports data between a wireless LAN and a wired LAN
with wireless LAN Card
wireless network interface card
wireless node
with area of coverage

4. One of the advantage of Wireless LAN
provide mobility
suitable for
school campus
taking inventory in a warehouse
making order for a restaurant
hospitals
construction site
temporarily office
health care ; retail ; manufacturing ; warehousing ; education

5. Network Topology
Network Topology = logical layout or the way in which the computers and other network devices are connected
Each computer / device = node
Common Topologies
Bus topology
Star topology
Ring topology

6. Bus Topology
all computers and other network devices are connect to a single central cable

7. Adv : Disadv : Easy to set up
failure of one device does not affect the rest of the bus network
Disadv :
failure of any point on the central bus may lead to the failure of the whole network
only one PC can send data on a bus network
therefore number of computer attached to the bus will affect the performance of network
more PC, more waiting, slower the network

8. 3 concepts about Bus Topology
sending the signal
signal bounce (CSMA / CD)
terminator

9. Sending the signal in form of electronic signals
sent to all computers on the network
only the computer whose address matches the address encoded in the original signal accepts the information
all other PC reject the data

10. Signal Bounce as data is sent to the entire network
travels from one end of the cable to the other
if signal is allowed to continue uninterrupted
signal will keep bouncing back and forth
other PC cannot send signals
therefore signal must be stopped after it has a chance to reach the proper destination address

11. Terminator to stop the signal from bouncing
a component called a terminator
placed at each end of the cable
to absorb free signals
to clear the cable so that other PCs can send data
both end should plug with terminator

12. Star Topology all the devices on the network
connect to a central device (hub / switch / router)
thus forming a star
if one device / computer fail
not affecting the others.
If the connecting cable between an device and the central device fail / has problem
not affecting the others

13. If the central device fails
power / networking problem
the entire network is not working
Star topology is the most common type of network topology

15. Advantage : Disadvantage : centralized resources
centralized management
Disadvantage :
great deal of cable in a large network installation
if central point fail, the entire network goes down

16. no bouncing and terminator
One PC fail
if one PC, or one of the cable that connects it to the hub fails (on a star network)
only the failed computer will not be able the
send, or
receive network data
no bouncing and terminator

17. Ring Topology all the devices are connected on a circular path
data flows in only one direction
For sending data
data travels to each computer on the ring until it reaches its destination
control data transmission by using
token-passing scheme

18. Token Disadv : control signal passes from one device to the next
indicating which device is allow (has the right) to transmit signal
thus ensure the only one computer at a time can transmit data
therefore, no data collision
Disadv :
if a device on a ring network fail / cable fail
whole network fail

19. Topologies : usually more than 1 topology is used in a network
For example : school network
bus + star

20. Network Operating System
Desktop Operating System
e.g. Windows 98 / ME
good to use
with necessary software for establishing communication with a network server
But if want to
manage network resources
control the flow of data
maintain security …………….. !!!!!!!!

21. Thus need a Network Operating System (NOS) NOS :
has 2 components :
Network Server Software
Network Client Software

22. Network Server Software
e.g. Mac OS X Server / Windows .NET Server
control file access from the server’s hard disk
manage print queue
tracks user data such as user Ids and passwords
Network Client Software
Mac OS X, Windows XP Professional
gather login information
handles drive mapping
directs printouts to the network printers