W-LAN (Wireless Local Area Network),

1. “Wireless local area Network
(WLANS)”
IPT201_14_ODD_34

2. Wireless LAN?
 A wireless LAN or WLAN is a wireless local area network that uses radio
waves as its carrier.
 The last link with the users is wireless, to give a network connection to all
users in a building or campus.
 The backbone network usually uses cables

3. Common Topologies
The wireless LAN connects to a wired LAN
 There is a need of an access point that bridges
wireless LAN traffic into the wiredLAN.
 The access point (AP) can also act as a repeaterfor
wireless nodes, effectively doubling the maximum
possible distance betweennodes.

4. Common Topologies
Complete Wireless Networks
 The physical size of the network is determinedby the maximum reliable
propagation range of the radio signals.
 Referred to as ad hoc networks
 Suited for temporary situations such as meetings and conferences.

5. How do wireless LANs work?
Wireless LANs operate in almost the same way as wired LANs, using the same
networking protocols and supporting the most of the same applications.

6. How are WLANs Different?
 They integrate into existing networks through access points which provide a
bridging function.
 They let you stay connected as you roam from one coverage area to another.
 They have unique security considerations (WEP,WPA,WPA-2).
 They have specificinteroperability requirements.
 They require different hardware Ex-Wireless Routers.
 They offer performance that differs from wired LANs.

7. Some Devices that use W-LAN
Tablets

8. Wireless v/s Wired networks

9. Wireless v/s Wired networks(continue..)
 Regulations of frequencies
 Limited availability, coordination is required.
 useful frequencies are almost all occupied.
 Bandwidth and delays(Disadvantage)
 Low transmission rates
 few Kbits/s to some Mbit/s.
 Higher delays
 several hundred milliseconds
 Higher loss rates
 susceptible to interference, e.g., engines, lightning

10. Wireless v/s Wired networks(continue..)
 Always shared medium
 Lower security, simpler activeattacking
 SSID accessible for everyone

11. Wireless v/s Wired networks(continue..)
$ For Wireless (WLAN) you need wireless $ You Require RJ45 jack network
network interface card. interface card for wired(LAN)

12. OSI- Open System Interconnection Reference
Model
OSI was developed in 1984 by the International Standard
Organization. This model was developed to subdivide a communication
system into small parts, called layers
The OSI model defines the
functionality of network
communication.
Dividing the
communication
into 7 layer
7. Application
6. Presentation
5. Session
4. Transport
3. Network
2. Data Binding
1.Physical Layer

14. Wireless LANs
 Infrared (IrDA) or radio links (Wavelan)
 Advantages
– very flexible within the reception area
– Ad-hoc networks possible
– (almost) no wiring difficulties
 Disadvantages
– low bandwidth compared to wired networks
– many proprietary solutions
 Infrastructure v/s ad-hoc networks (802.11)

15. Router
 Router is a device which connects different networks-frequently over
a large distances.
 A router is a device that forwards data packets between computer
networks, creating an overlay internetwork.

16.  A router is connected to two or more data lines from different networks.
When a data packet comes in on one of the lines, the router reads the
address informationin the packet to determineits ultimate destination.
 A data packet is typically forwarded from one router to another through
the networks that constitute the internetwork until it gets to its destination
node.
 It contains a routing table in which all information about the address of
connected networks.
Router (continue..)

17. Router operates in network layer of OSI
Model

18. Packets routed by routers to their
destinations

19. Bridges
 A bridge is a connecting device which has it’s own processor, memory
and two NIC cards, to connect two portions of a network
 Facilitates host to host communication
 Operates at the physical as well as data link layer

20. Importance of a Bridge
 Bridge is to divide a big network in to smaller sub-networks
 A bridge connects two LAN’s
5
4
3
2
1
4
3
2
1
5

21. Functions of a bridge
 As a physical layer device it generates the signal it receives.
 As a data link layer device it checks the source and destination addresses in the frame.
 It send data frames only to the concerned destination.
 It minimizes unwanted traffic
 It minimizes network congestion
 Error links can be identified and then isolated
 Security features or access control can be added
 It acts as a filter

22. Gateway
 To connect two networks that use different protocols
 It works at all seven layers of OSI model
 Unlike a router a gateway can forward packets across different networks that may
also use different protocols
 Ex. If network A is token ring network using TCP / IP and network B is a novell-
netware network, a gateway can relay frames between the two.

23. Application layer
Presentation layer
Session layer
Transport layer
Network layer
Data link layer
Physical layer
G
A
T
E
W
A
Y
A
Physical layer
Data link layer
Network layer
Transport layer
Session layer
Presentation layer
Application layer
B
Gateway at all OSI layers

24. Functions of Gateways
 It has abilities to translate between different frame formats and also between
different protocols
 It is a very powerful computer system compared to a bridge
 It is used to connect huge and incompatible networks

25. Routing protocols
 Routing protocols Routing protocols are the set of rules used by the routers to communicate
between source & destination.
 Each protocol has its own algorithm to choose the best path.
 The metrics by routing protocols ,
*Number of network layer devices along with the path (hop count)
*Bandwidth
*Delay
*Load
*MTU
*Cost Routing protocols store the result of these metrics in routing table.

26. Types of Routing Protocols
 AODV
Ad hoc On-Demand Distance Vector (AODV) Routing is a routing protocol
for mobile ad hoc networks (MANETs) and other wireless ad hoc networks.
In AODV, the network is silent until a connectionis needed.

27. Routing Protocols (continue..)
 DSR
Dynamic Source Routing (DSR) is a routing protocol for wireless mesh networks.
It is similar to AODV in that it forms a route on-demand when a transmitting
node requests one.
However, it uses source routing instead of relying on the routing table at each
intermediate device.

28. Routing Protocols (continue..)
DYMO
The DYMO routing protocol is successor to the popular Ad hoc On-Demand
Distance Vector (AODV) routing protocol and shares many of its benefits.
It is, however, slightly easier to implement and designed with future
enhancements in mind.