w-lan (wireless local area network)
TRANSCRIPT
“Wireless local area Network (WLANS)”
IPT201_14_ODD_34
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
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 wired LAN.
The access point (AP) can also act as a repeater for wireless nodes, effectively doubling the maximum possible distance between nodes.
Common Topologies
Complete Wireless Networks
The physical size of the network is determined by the maximum reliable propagation range of the radio signals.
Referred to as ad hoc networks
Suited for temporary situations such as meetings and conferences.
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.
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 specific interoperability requirements.
They require different hardware Ex-Wireless Routers.
They offer performance that differs from wired LANs.
Some Devices that use W-LAN
Tablets
Wireless v/s Wired networks
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
Wireless v/s Wired networks(continue..)
Always shared medium
Lower security, simpler active attacking
SSID accessible for everyone
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)
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. Network2. Data Binding
1.Physical Layer
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)
Router
Router is a device which connects different networks-frequently over
a large distances.
A router is a device that forwards data packets between computernetworks, creating an overlay internetwork.
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 information in the packet to determine its 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..)
Router operates in network layer of OSI Model
Packets routed by routers to their destinations
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
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
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
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.
Application layer
Presentation layer
Session layer
Transport layer
Network layer
Data link layer
Physical layer
GA
T
E
W
AY
A
Physical layer
Data link layer
Network layer
Transport layer
Session layer
Presentation layer
Application layer
B
Gateway at all OSI layers
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
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.
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 connection is needed.
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 transmittingnode requests one.
However, it uses source routing instead of relying on the routing table at eachintermediate device.
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.