Download What is wireless networking?

ITNW 1380 COOPERATIVE EDUCATION –
NETWORKING
Seminar # 5
VOIP and Wireless Networking Solutions
Unified Communications and
Collaboration Solution
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Unified Communications
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IP Convergence: Voice, data & video on the same
network.
Voice: Voice over IP - VOIP.
Collaboration Solution
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IM: Yahoo, MSN, Novell, Skype...
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3G Wireless: CDMA, UMTS.
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4G Wireless: Wireless LAN.
Today's Collaboration Solution
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VOIP
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Wireless LAN
PART I
VOIP
Presenter: Nguyen Chi Thanh
VOIP
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VOIP Definition
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VOIP Service Providers
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VOIP Benefits
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VOIP Protocols
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VOIP Networks
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VOIP Open Source Software
VoIP Definition
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VoIP (Voice Over Internet Protocol).
Voice transmission over packet based network
such as Internet, corporate intranet, LAN, WAN.
VoIP known as Internet telephony.
Integrate VoIP enabled voice signals with faxes &
data into a unified network.
Telephone conversation over Internet.
VOIP
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VOIP Definition
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VOIP Service Providers
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VOIP Benefits
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VOIP Protocols
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VOIP Networks
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VOIP Open Source Software
VoIP Service providers
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With VoIP you can call PC to PC, PC to VoIP
phone, or VoIP phone to ordinary phone over
Internet.
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VoIP is popular international calling.
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VoIP enables you to call from virtually anywhere.
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VoIP provider offer low rates or free service deals
– Free World Dial & Skype...
VOIP
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VOIP Definition
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VOIP Service Providers
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VOIP Benefits
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VOIP Protocols
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VOIP Networks
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VOIP Open Source Software
VOIP Benefits
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Lower long distance rates: requires only Internet
connection.
Simplicity: VoIP transmission combines voice &
data.
Capacity: VoIP better uses you network for less.
Global outsourcing: International call centers rely
on VoIP.
Automatic routing: Receive calls automatically to
your VoIP phone.
Portability: Travel with your VoIP phones.
VOIP
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VOIP Definition
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VOIP Service Providers
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VOIP Benefits
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VOIP Protocols
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VOIP Networks
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VOIP Open Source Software
VoIP Protocols
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H.323
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Session Initiation Protocol (SIP)
H.323
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Published by Telecommunication Standardization
Sector (ITU-T) in November 1996.
ITU-T defines H.323 protocols to provide audiovisual communication sessions on any packet
network.
Widely implemented by voice and
videoconferencing equipment manufacturers.
Widely deployed worldwide by service providers
and enterprises for both voice and video services
over Internet Protocol (IP) networks.
H.323 (Cont.)
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Suited for transmitting calls across networks
using a mixture of IP, PSTN, ISDN, and QSIG
over ISDN.
Within the context of H.323, an IP-based PBX
might be an H.323 Gatekeeper.
Codecs:
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Video codec: H.261, H.263, H.264
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Audio codec: G.711, G.729 (including G.729a),
G.723.1, G.726
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Text codecs: T.140
H.323 (Cont.)
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H.323 Architecture:
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The H.323 system defines several network elements
that work together in order to deliver rich multimedia
communication capabilities
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Terminals, Multi-point Control Units (MCUs),
Gateways, Gatekeepers, and Border Elements.
A complete, sophisticated H.323 protocol stack
VoIP Protocols (Cont.)
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H.323
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Session Initiation Protocol (SIP)
Session Initiation Protocol (SIP)
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Purpose of SIP
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SIP URI
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SIP Network Elements
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SIP Messages
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Transactions
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Dialogs
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Typical SIP Scenarios
Purpose of SIP
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Application-layer control protocol which has
been developed and designed within the IETF.
The most important one is RFC3261 which
contains the core protocol specification.
The protocol is used for creating, modifying, and
terminating sessions with one or more
participants. By sessions we understand a set of
senders and receivers that communicate and state
kept those senders and receivers during the
communication.
Purpose of SIP (Cont.)
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Purpose of SIP is just to make the communication
possible, the communication itself must be
achieved by another means. Two protocols that
are most often used along with SIP are RTP and
SDP.
RTP – Real Time Protocol is used to carry the
real-time multimedia data (including audio,
video, and text), the protocol makes it possible to
encode and split the data into packets and
transport such packets over the Internet.
Purpose of SIP (Cont.)
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SDP – Session Description Protocol, which is
used to describe and encode capabilities of
session participants. Such a description is then
used to negotiate the characteristics of the session
so that all the devices can participate (negotiation
of codecs used to encode media so all participants
will be able to decode it).
SIP is based on HTTP protocol.
SIP is used to carry the description of session
parameters, the description is encoded into a
document using SDP.
SIP URI
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SIP entities are identified using SIP URI
(Uniform Resource Identifier).
A SIP URI has form of sip:username@domain,
for instance, sip:[email protected].
As we can see, SIP URIs are similar to e-mail
addresses, it is, for instance, possible to use the
same URI for e-mail and SIP communication,
such URIs are easy to remember.
SIP Network Elements
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Basic SIP elements are:
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User Agents:
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Internet end points that use SIP to find each other and
to negotiate a session characteristics are called user
agents (cellular phones, PSTN gateways, PDAs)
Proxy Servers:
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In addition to that SIP allows creation of an
infrastructure of network hosts called proxy servers.
User agents can send messages to a proxy server.
They perform routing of a session invitations
according to invitee's current location, authentication,
accounting and many other important functions
SIP Network Elements (Cont.)
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Registrar:
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The registrar is a special SIP entity that receives
registrations from users, extracts information about
their current location (IP address, port and username
in this case) and stores the information into location
database.
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Purpose of the location database is to map
sip:[email protected] to
sip:[email protected]:5060.
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The location database is then used by thanhnc's proxy
server. When the proxy receives an invitation for
sip:[email protected], it will search the
location database.
SIP Network Elements (Cont.)
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Redirect Server:
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The entity that receives a request and sends back a
reply containing a list of the current location of a
particular user is called redirect server.
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A redirect server receives requests and looks up the
intended recipient of the request in the location
database created by a registra.
SIP Messages
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SIP Requests:
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ACK This message acknowledges receipt of a final
response to INVITE.
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BYE Bye messages are used to tear down multimedia
sessions.
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CANCEL Cancel is used to cancel not yet fully
established session.
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REGISTER Purpose of REGISTER request is to let
registrar know of current user's location.
SIP Messages (Cont.)
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SIP Responses;
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The reply code is an integer number from 100 to 699
and indicates type of the response.
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1xx are provisional responses. A provisional response
is response that tells to its recipient is received but
result of the processing is not known yet.
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2xx responses are positive final responses.
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3xx responses are used to redirect a caller.
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4xx are negative final responses.
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5xx means that the problem is on server's side.
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6xx reply code means that the request cannot be
Transactions
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SIP is transactional protocol.
A transaction is a sequence of SIP messages
exchanged between SIP network elements.
SIP messages:
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SIP user#1
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INVITE ---------->
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SIP user#2
<---------- 200 OK
ACK
---------->
SIP Messages
Dialogs
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A dialog represents a peer-to-peer SIP
relationship between two user agents.
For instance, INVITE message establishes a
dialog, because it will be later followed by BYE
request which will tear down the session
established by the INVITE. This BYE is sent
within the dialog established by the INVITE.
SIP Dialogs
Typical SIP Scenarios
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Registration
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Session Invitation
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Session Termination
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Record Routing
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Event Subscription and Notification
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Instant Messages
VOIP
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VOIP Definition
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VOIP Service Providers
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VOIP Benefits

VOIP Protocols
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VOIP Networks
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VOIP Open Source Software
VoIP Network
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Solution for Enterprise from AudioCodes Ltd.:
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IP-PBX
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IP Telephony Survivable Network
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PBX VoIP Networking
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Contact Center for Enterprises
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Unified Messaging for Enterprises
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Conferencing for Enterprises
IP-PBX
IP Telephony Survivable Network
PBX VoIP Networking
Contact Center for Enterprises
Unified Messaging for Enterprises
Conferencing for Enterprises
VOIP
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VOIP Definition
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VOIP Service Providers

VOIP Benefits
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VOIP Protocols
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VOIP Networks
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VOIP Open Source Software
VOIP Open Source Software
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IPTEL SIP Server:
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SER – SIP Express Router (Registrar/Proxy/Redirect
server)
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Support database backends: MySQL, Oracle,
Postgres.
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RTP Proxy, NAT traversal
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Interoperability with Cisco, Microsoft. PingTel,
Siemens, Xten and many others.

http://www.iptel.org/ser
VOIP Open Source Software (Cont.)
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Asterisk:
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Most popular open source VOIP software.
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IP PBX which connect users over IP to PSTN, T1/E1.
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Media gateway, bridge the legacy PSTN to IP
telephony.
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Media server with IVR, voice mail, automated
attendant, unified messaging.
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Call Center, ACD, advance skills-based routing.

http://www/asterisk.org
References
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SIP: http://www.sip.org/
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IPTEL: http://www.iptel.org
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IPTel: http://www.iptel.org/sip/intro
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AudiCodes:
http://www.audiocodes.com/Content.aspx?voip=2
421
Asterisk: http://www.asterisk.org
The End of PART I
Questions
PART II
WIRELESS NETWORKING
WIRELESS NETWORKING
Presenter: Nhan Nguyên Phương
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Section One - Wireless Networking
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Section Two - Wireless Networking and the Internet
Section One - Wireless Networking
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1.
What is wireless networking?
Wireless network components?
What is IEEE 802.11?
Wireless equipment from different vendors?
Communications between computers from WLAN and LAN
Wireless network range?
How many wireless networked computers can use a single access point?
Can I have more than one access point?
What is Roaming?
How can I use a wireless network to interconnect two LANs?
Is it true that wireless networking is only good for laptop computers?
Wireless Network Security?
1. What is wireless networking?
Wireless networking: two or more computers to communicate using
standard network protocols without network cabling.
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IEEE 802.11 (WiFi)
IEEE 802.16 (WiMax - Worldwide Interoperability for Microwave Access,
operates < 66 GHz)
IEEE 802.20 (MBWA - Mobile Broadband Wireless Access)
IEEE 802.22 (WRAN – Wireless Regional Area Network)
HomeLAN
Bluetooth
….
2. Wireless network components
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Two kinds of wireless networks:
a. Ad-hoc / peer-to-peer wireless network consists of
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A number of computers each equipped with a wireless networking interface
card.
Each computer can communicate directly with all of the other wireless
enabled computers.
They can share files and printers, but may not be able to access wired LAN
resources, unless one of the computers acts as a bridge to the wired LAN
using special software. (This is called "bridging")
•
Figure 1: Ad-Hoc or Peer-to Peer Networking.
Each computer with a wireless interface can communicate directly with
all of the others.
b. Infrastructure Wireless Network: A wireless network can also use
an access point, or base station.
It can connect (or "bridge") the wireless LAN to a wired LAN,
allowing wireless computer access to LAN resources.
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There are two types of access points:
 Hardware access points offer comprehensive support of most wireless
features
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Figure 2: Hardware Access Point.
Wireless connected computers using a Hardware Access Point.
 Software Access Points which run on a computer equipped with a
wireless network interface card as used in an ad-hoc or peer-to-peer
wireless network. (See Figure 3)
Figure 3: Software Access Point.
Wireless connected computers using a Software Access Point.
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3. What is IEEE 802.11?
The most widely used standard is IEEE802.11 produced by the Institute
of Electrical and Electronic Engineers (IEEE). This is a standard
defining all aspects of Radio Frequency Wireless networking.
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802.11b
802.11g
802.11a
802.11n
802.11b: slowest and least expensive. IEEE802.11b transmits in the 2.4
GHz frequency band of the radio spectrum. It can handle up to 11
megabits of data per second, and it uses complimentary code keying
(CCK) coding.
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802.11g
 transmits at 2.4 GHz like 802.11b, but much faster
 it can handle up to 54 megabits of data per second. (Mbps)
 It also uses orthogonal frequency-division multiplexing (OFDM),
a more efficient coding technique that splits that radio signal into
several sub-signals before they reach a receiver
802.11a transmits at 5GHz and can move up to 54 megabits of data per
second. It is also much faster because it uses the same OFDM coding as
802.11g..
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802.11n : newest. This standard significantly improves speed and
range. IEEE802.11n can achieve speeds as high as 140 megabits per
second.
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4. Wireless equipment from different vendors
Yes and No: Frequency Hopping (FH) and Direct Sequence Spread
Spectrum (DSSS or DS) are not interoperable.
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Be sure to obtain guarantees from the vendors that the hardware will
interoperate and follows the standards.
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5. Communications between computers from WLAN
and LAN
Bridge between the wireless and wired network is needed  either with
a hardware access point or a software access point.
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If more features required on wired network, a software access point
may be the best solution.
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6. Wireless Network Range?
The actual distance varies depending upon the environment; indoor and
outdoor ranges
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Typical indoor ranges are 150-300 feet, but can be shorter if the building
construction interferes with radio transmissions. Longer ranges are possible,
but performance will degrade with distance.
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Outdoor ranges are quoted up to 1000 feet, but again this depends upon the
environment.
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To extend the range, by using more than a single access
point or using a wireless relay /extension point
7. How many wireless networked computers can use a
single access point?
This depends upon the manufacturer. Some limit of 10, more expensive
units support up to 100 wireless connections.
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Using more computers than recommended will cause performance and
reliability to suffer.
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Software access points has user limitations, but this depends upon the
specific software, and the host computer's ability
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8. Can I have more than one access point?
Yes, multiple access points can be connected to a wired LAN, or
sometimes even to a second wireless LAN if the access point supports
this.
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In most cases, separate access points are interconnected via a wired
LAN, providing wireless connectivity in specific areas such as offices or
classrooms, but connected to a main wired LAN for access to network
resources, such as file servers. (See Figure 4)
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Figure 4: Multiple Access Points.
Wireless connected computers using Multiple Access Points.
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If a single area is too large to be covered by a single access
point, then multiple access points or extension points can be
used. – (Note that an "extension point" is not defined in the
wireless standard, but have been developed by some
manufacturers).
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Some manufacturers produce extension points, which act as
wireless relays, extending the range of a single access point.
Multiple extension points can be strung together to provide
wireless access to far away locations from the central access
point. (See Figure 5)

Figure 5: Extension Point.
Wireless connected computers using an Access Point with an Extension Point.
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9. What is Roaming?
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A wireless computer can "roam" from one access point to another,
Usually this is completely transparent to the user. Some access point
configurations require security authentication when swapping access
points, usually in the form of a password dialog box.
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Access points are required to have overlapping wireless areas to achieve this
as can be seen in the following diagram:

Figure 6: Roaming.
A user can move from Area 1 to Area 2 transparently. The Wireless networking hardware automatically swaps to the
Access Point with the best signal.
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Not all access points are capable of being configured to support roaming. Any
access points for a single vendor should be used when implementing roaming,
as there is no official standard for this feature.
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10. Connecting 2 LANS using Wireless Network
Wireless networking offers a cost-effective solution to users with
difficult physical installations such as campuses, hospitals or businesses
with more than one location in immediate proximity but separated by
public thoroughfare.
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This type of installation requires two access points. Each access point
acts as a bridge or router connecting its own LAN to the wireless
connection.
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The wireless connection allows the two access points to communicate
with each other, and therefore interconnect the two LAN's.
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Figure 7: LAN to LAN Wireless Communications
A Hardware Access Point providing wireless connectivity to local computers and a software access point.
The software access point provides Wired Ethernet network 2 computers access to Wired Network 1.
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Note that not all hardware access points have the ability to directly interconnect to another hardware access
point, and that the subject of interconnecting LAN's over wireless connections is a large and complex one,
and is beyond the scope of this introduction

11. Is it true that wireless networking is only good for
laptop computers?
Wireless networking has benefits for mobile laptop. There are
benefits for users of fixed position computers as well.
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It is also beneficial to many schools and businesses with
unsuitable building layouts or walls that cannot be wired 
making it difficult or impossible to build a wired network.
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computers are separated from a main network a wireless link may
be more cost effective than network cabling although the latter is
perfectly feasible.
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Temporary wireless LANs can easily be created for exhibitions,
school or business projects, all without any trailing cabling.
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12. Wireless Network Security
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Wireless communications is easy to get intruded.
IEEE 802.11 wireless communications have a function called WEP
(Wired Equivalent Privacy), a form of encryption which provides
privacy comparable to that of a traditional wired network

Traditional Virtual Private Networking (VPN) techniques will work
over wireless networks in the same way as traditional wired networks.

Section Two - Wireless Networking and the
Internet
 How can I use a wireless network to share an Internet connection?
1. If I have more than one hardware access point, how can I share a
single Internet connection?
13. Internet Share Connection over Wireless Network?
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To share an Internet connection across a LAN you need two things:
 an Internet sharing hardware device or software program
 a LAN
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Requires: Hardware or software access point and a wireless LAN.
Figure 8: Software Access Point.
Wireless connected computers using a Software Access Point for shared Internet access.
A hardware access point may provide Internet Sharing capabilities to Wired
LAN computers, but does not usually provide much flexibility beyond very
simple configurations. (See Figure 9)
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Figure 9: Hardware Access Point.
Wireless connected computers using a Hardware Access Point for shared Internet access
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14. If I have more than one hardware access point, how can I share a single
Internet connection?
If an existing wired LAN already has an Internet connection, then the hardware access
points simply connect to your LAN and allow wireless computers to access the existing
Internet connection in the same way as wired LAN computers.
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Figure 10: Multiple Access Points.
Wireless connected computers using Multiple Access Points
.
The End of Part II
Thank you for your attention