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COMPUTER NETWORKS
- CHANDRA PRAKASH GUPTA (130301CSR027)
- PARMANAND KUMAR (130301CSR028)
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Content:
 Wireless LAN 3 -- 21
 Introduction 4 -- 5
 Application 6
 IEEE 802.11 7 -- 13
 Bluetooth 14 -- 21
 Virtual N/W 22 -- 39
 Introduction 23
 X.25 24
 Frame Relay 25 -- 32
 ATM 33 -- 39
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Chandra Prakash Gupta & Parmanand Kumar

Wireless LAN
IEEE 802.11
BLUETOOTH
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Wireless LAN
 A wireless LAN is a flexible data communications
system implemented as an extension to or as an
alternative for a wired LAN.
 Using radio frequency (RF) technology wireless LANs
transmit and receive data over the air minimizing the
need for wired connections.
 Thus, combining data connectivity with user mobility.
4

LAN/WLAN World
 LANs provide connectivity for interconnecting computing
resources at the local levels of an organization
 Wired LANs
Limitations because of physical, hard-wired infrastructure
 Wireless LANs provide
Flexibility
Portability
Mobility
Ease of Installation
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 Medical Professionals
 Education
 Temporary Situations
 Airlines
 Security Staff
 Emergency Centers
Wireless LAN Applications
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 In response to lacking standards, IEEE developed the
first internationally recognized wireless LAN standard –
IEEE 802.11
 IEEE published 802.11 in 1997, after seven years of work
 Most prominent specification for WLANs
 Scope of IEEE 802.11 is limited to Physical and Data Link
Layers.
IEEE 802.11 Wireless LAN Standard
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 Fast Product Development
 Stable Future Migration
 Price Reductions
 The 802.11 standard takes into account the following
significant differences between wireless and wired LANs:
Power Management
Security
Bandwidth
Benefits of 802.11 Standard
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IEEE 802 LAN Standards Family
IEEE 802.3
Carrier
Sense
IEEE 802.4
Token
Bus
IEEE 802.5
Token
Ring
IEEE 802.11
Wireless
IEEE 802.2
Logical Link Control (LLC)
PHY
OSI Layer 1
(Physical)
MAC
OSI Layer 2
(Data Link)
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Access point (AP): A station that provides access to the DS.
Basic service set (BSS): A set of stations controlled by a
single AP.
Distribution system (DS): A system used to interconnect a
set of BSSs to create an ESS.
DS is implementation-independent. It can be a wired 802.3 Ethernet
LAN, 802.4 token bus, 802.5 token ring or another 802.11 medium.
Extended service set (ESS):Two or more BSS interconnected
by DS
IEEE 802.11 Terminology
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A BSS without an AP is called an ad hoc network;
a BSS with an AP is called an infrastructure network.
Note:
11

Basic service sets (BSSs): 12

Extended service sets (ESSs): 13

Bluetooth:
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 Designed to be used to connect both mobile devices and
peripherals that currently require a wire.
 Simplifying communications between:
 - Devices and the internet
 - Data synchronization
 Short range wireless radio technology
 Range: 10 meters
 “USB without wires”

Advantages:
 Wireless (No Cables)
 No Setup Needed
 Low Power Consumption (1 Milliwatt)
 Industry Wide Support
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Disadvantages:
 Short range (10 meters)
 Small throughput rates
 Data Rate 1.0 Mbps
 Mostly for personal use (PANs)
 Fairly Expensive
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Working:
 Bluetooth is a standard for tiny,
radio frequency chips that can
be plugged into your devices
 These chips were designed to
take all of the information that
your wires normally send, and
transmit it at a special
frequency to something called a
receiver Bluetooth chip.
 The information is then
transmitted to your device
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Piconet and Scatternet
 Piconet
 Basic unit of Bluetooth networking
 Master and one to seven slave devices
 Master determines channel and phase
 Scatternet
 Device in one piconet may exist as master or slave in another
piconet
 Allows many devices to share same area
 Makes efficient use of bandwidth
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Piconet:
19

Scatternet:
20

Layers of Bluetooth:
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 BT Radio (2.4 GHZ Freq. Band):
 Baseband: FH-SS (79 carriers),
CDMA (hopping sequence from
the node MAC address)
 Audio: Interfaces directly with
the baseband. Each voice
connection is over a 64Kbps SCO
link.
 Logical Link Control and
Adaptation Layer (L2CAP)

Virtual N/W
FRAME RELAY
ATM
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Introduction:
 In virtual circuit network different design issues are
discussed during the development of virtual network
 Some of are:
 Bandwidth
 Speed of the network
 Frame size of the network
 Control mechanism
 In early 90’s the wireless n/w for virtual circuit designed, know
as X.25.
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X.25:
 The X.25 is a virtual n/w which can operate at a speed of a 1.544
Mbps.
 The limitation of this n/w is that it doesn’t allow burst data.
 It operate on the,
 Physical layer
 Datalink layer
 N/W layer
 It is having low BW (Bandwidth).
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25
Frame Relay (FR):
 FR is a high-performance WAN protocol.
 It operates at the,
 Physical Layer
 Datalink Layer
 FR originally was designed for use across Integrated Service Digital
Network (ISDN) interfaces.
 Today, it is used over a variety of other network interfaces as well.
 FR is an example of a packet-switched technology.
 Packet-switched networks enable end stations to dynamically share
the network medium and the available bandwidth.Chandra Prakash Gupta & Parmanand Kumar

Frame Relay (FR) Characteristics:
 Backbone of N/W.
 Allow Burst data.
 Speed: 45 Mbps.
 Frame Size: 9000 Bytes
 No flow and error control mechanism.
 Only error detection process.
 Doesn’t support retransmission of frames
 It can be used with the protocols of higher layer proving error and
flow control mechanism.
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Architecture of Frame Relay:
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Frame Relay Frame Structure:
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Frame Relay Frame Structure:
 FR define its own 4 Bytes frame format.
 The address area (2 bytes)
 10 bits represents the actual circuit identifier
 6 bits of fields related to congestion management
 Flags indicate the beginning and end of the frame
 Three primary components make up the Frame Relay frame
 The header and address area
 The user-data portion
 The frame-check sequence (FCS)
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VOFR:
 It stands for Voice Over Frame Relay.
 High speed internet connectivity required.
 It is also know as bursty data.
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FRAD:
 It stands for Frame Relay Assembler and Disassembler.
 Support lower version of n/w.
 Assembler is used at the sender end where signals of lower
version are converted to FR n/w.
 Disassembler is used at receiver end to convert the FR n/w
into other version of the n/w.
 Speed of n/w depends on,
 FR
 BW of the n/w
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FRAD:
32

ATM:
 It stands for Asynchronous Transmission Mode.
 It was designed in the 1980’s.
 Designed to increase the connectivity speed between the n/w.
 It is the wireless mode of communication.
 It enables virtual path between sender and receiver by creating
virtual n/w.
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ATM:
 Challenge faced,
 To increase the speed of n/w by fibre optics to maximize the size
of BW.
 Should support lower version of n/w.
 Cost factor.
 Telecommunication hierarchies should not changed (Ex. Telephone
n/w).
 Connection orientation.
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Architecture of ATM:
 To connect different n/w it uses,
 LAN
 Switches
 N/w connected by interfaces.
 Speed of the n/w is more than the FR due to optical fibre.
 It provides larger BW for more no. of connection in the n/w.
 It allow voice over the n/w by using technique of modulation which
digitize the voice over the n/w.
 Compatible with the lower version n/w by the help of interfaces.
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 Users or LAN connected to n/w by User N/w Interface (UNI).
 Switches are connected by N/w N/w Interface (NNI).
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 It provides connection in 2 phase,
 PVC: Permanent Virtual Circuit
 SVC: Switch Virtual Circuit
 It has own frame format, know as ATM Cell
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ATM Cell:
 VPI: Virtual Path Identifier
 VCI: Virtual Circuit Identifier
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ATM Application:
 ATM is the Backbone Network for many broadband applications
including Information Superhighway.
 Some of the key applications can be mentioned as follows,
 Video Conferencing
 Desktop Conferencing
 Multimedia Communications
 ATM Over Satellite Communications
 Mobile Computing over ATM for Wireless n/w
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THANK YOU
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