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Dear sir,
         Am doing MBA from 3rd semester ANNA University and i need some questions brief Explanations please give the answers below the question  sir,

1.what is the meaning of IEEE WLAN based ADHOC networks?
2.whats is peer to peer networks?
3.why all network using using in 802.11 a/b/an?

Thanks and regards,

Question:   Dear sir,
        Am doing MBA from 3rd semester ANNA University and i need some questions brief Explanations please give the answers below the question  sir,

1.what is the meaning of IEEE WLAN based ADHOC networks?
what is the meaning of IEEE WLAN based ADHOC networks
Types of Wireless Networks: infrastructure vs. adhoc
• Infrastructure
• Fixed, wired backbone
• Mobile communicates
directly with access
• Suitable for locations
where access points can
be placed
• Cellular networks
Why Ad Hoc Networks ?
❒ Ease of deployment
❒ Speed of deployment
❒ Decreased dependence on infrastructure
What is an Ad hoc Network?
❒ A network without any base
stations “infrastructure-less”
or multi-hop
❒ A collection of two or more
devices equipped with wireless
communications and networking
❒ Supports anytime and
anywhere computing
❒ Two topologies:
❍ Heterogeneous (left)
• Differences in capabilities
❍ Homogeneous or fully
symmetric (Right)
• all nodes have identical
capabilities and
Mobile Ad Hoc Networks?
❒ Mobility causes route changes
What is an Ad hoc Network?
❒ Self-organizing and adaptive –
Allows spontaneous formation
and deformation of mobile
❒ Each mobile host acts as a
❒ Supports peer-to-peer
❒ Supports peer-to-remote
❒ Reduced administrative cost
❒ Ease of deployment
Ad Hoc Networks – Operating
❒ Fig. depicts a peer-to-peer multihop ad hoc network
❒ Mobile node A communicates directly with B (single hop) when a channel is available
❒ If Channel is not available, then multi-hop communication is necessary e.g. A->D->B
❒ For multi-hop communication to work, the intermediate nodes should route the packet i.e. they should act as a router
❒ Example: For communication between A-C, B, or D & E, should act as routers
Bringing up an Ad hoc Network
1. Ad hoc network begins with at least two nodes broadcasting
their presence (beaconing) with their respective address
2. They may also include their location info if GPS equipped
3. Beaconing messages are control messages. If node A is able
to establish a direct communication with node B verified by
appropriate control messages between them, they both
update their routing tables
D E1-13
Bringing up an Ad hoc Network
4. Third node C joins the network
with its beacon
signal. Two scenarios are possible:
(i) A & B both try to determine if single hop
communication is feasible
(ii) Only one of the nodes e.g. B tries to
determine if single hop communication is feasible
and establishes a connection
5. The distinct topology updates consisting of both
address and the route updates are made in three
nodes immediately.
5. In first scenario, all routes are direct i.e. A->B,
B->C, and A->C (Lets assume bi-directional links)
Bringing up an Ad hoc Network
❒ In the second
scenario, the routes
are updated
1. First between B & C,
2. then between B & A,
3. Then between B & C
again confirming that
A and C both can
reach each other via
Topology Update Due to a Link
❒ Mobility of nodes may cause link breakage requiring route updates
❒ Assume link between B & C breaks because of some reason
❒ Nodes A & C are still reachable via D and E
❒ So old route between A &C was A->B->C is to be replaced by A->D->E->C
❒ All five nodes are required to incorporate this change in their routing table
❍ This change will happen first in nodes B & C
❍ Then A & E
❍ Then D
D E1-17
❒ What is an ad hoc network?
❒ Challenges facing ad hoc networks
❒ History of Ad hoc Networks
❒ General Concepts
❒ Introduction to IEEE 802.11
❒ Physical Layers of 802.11
Traffic Characteristics
❒ Traffic characteristics may differ in
different ad hoc networks
❍ bit rate
❍ timeliness constraints
❍ reliability requirements
❍ unicast / multicast / geocast
❍ host-based addressing / content-based
addressing / capability-based addressing
❒ May co-exist (and co-operate) with an
infrastructure-based network1-19
Traffic Profiles
❒ Three distinct types of
traffic patterns observed
in ad hoc networks
❒ Peer-to-peer between two
entities (Fig. a) – Bursty
❒ Two or more devices in a
group communication while
moving as a group
(correlated traffic) ->
remote to remote
❒ Hybrid non-coherent
communication among nodes
-> uncorrelated traffic1-20
Challenges in Ad hoc Mobile Networks (1)
❒ Host is no longer an end system - can also
be an acting intermediate system
❒ Changing the network topology over time
❒ Potentially frequent network partitions
❒ Every node can be mobile
❒ Limited power capacity
❒ Limited wireless bandwidth
❒ Presence of varying channel quality1-21
Challenges in Ad hoc Mobile Networks (2)
❒ No centralized entity – distributed
❒ How to support routing
❒ How to support channel access?
❒ How to deal with mobility?
❒ How to conserve power?
❒ How to use bandwidth efficiently?1-22
Problems Facing Routing in Ad hoc
❒ Routers are now moving
❒ Link changes are happening quite often
❍ Packet losses due to transmission errors
❒ Event updates are sent often – a lot of
control traffic
❒ Routing table may not be able to, converge
❒ Routing loop may exist
❒ Current wired routing uses shortest path
Problems facing channel access in Ad
hoc Networks
❒ Distributed channel access, i.e. no fixed
base station concept
❒ Very hard to avoid packet collisions
❒ Very hard to support QoS
❒ Early work on packet radio is based on
Problems of Mobility in Ad hoc
❒ Mobility affects signal transmission ->
Affects communication
❒ Mobility affects channel access
❒ Mobility affects routing
❍ Mobility-induced route changes
❍ Mobility-induced packet losses
❒ Mobility affects multicasting
❒ Mobility affects applications1-25
Mobility in Ad hoc Networks
❒ Mobility patterns may be different
❍ people sitting at an airport lounge
❍ New York taxi cabs
❍ kids playing
❍ military movements
❍ personal area network
❒ Mobility characteristics
❍ speed
❍ predictability
• direction of movement
• pattern of movement
❍ uniformity (or lack thereof) of mobility characteristics
among different nodes
Problems of Power in Ad hoc
❒ Ad hoc devices come in many different
❒ Most of them battery powered
❒ Battery technology is not progressing as
fast as memory or CPU technologies
❒ Wireless transmission, reception,
retransmission, beaconing, consume power!
❒ Quest for power-efficient protocols
❒ Quest for better power management
Research on Mobile Ad Hoc
❒ Variations in capabilities & responsibilities
❒ Variations in traffic characteristics, mobility
models, etc.
❒ Performance criteria (e.g., optimize throughput,
reduce energy consumption)
❒ Increased research funding -> Significant
research activity1-28
❒ What is an ad hoc network?
❒ Ad hoc Network Applications
❒ Challenges facing ad hoc networks
❒ History of Ad hoc Networks
❒ General Concepts
❒ Introduction to IEEE 802.11
❒ Physical Layers of 802.111-29
Packet Radio – First Ad hoc
❒ Packet switching was demonstrated by the
ARPANet in the 1960
❍ Key Advantage - Dynamic sharing of bandwidth
among multiple users
❒ DARPA initiated a packet radio network
(PRNet) research in 1972 recognizing
packet switching
❒ PRNet was to provide an efficient means of
sharing broadcast radio channel among
many radios1-30
Architecture of PRNETs
The network architecture of PRNETs, which comprises mobile
devices/terminals, packet radios, and repeaters. The static station is
Early Packet Radio Networks -
❒ Presence of mobile
❒ Mobile terminals
❒ Static station for
❒ Technology ahead of
❒ Not entirely
❒ Mobile repeater relays packet
from one repeater to other until
the packet makes it to destination
❒ Bellman Ford (Distance-Vector)
type of routing algorithm running
in a static station
❒ Static station has complete
❒ Routing table broadcasted to each
❒ Shortest delay path for every
destination in the network
available to every terminal1-33
❒ Periodic update for route
❒ ACK based flow control and
recovery from errors
❒ CSMA based MAC
❒ Low mobility
❒ Low throughput (2 kbps per
The interface of a data terminal to
a packet radio
❒ The user computer interfaced to radio via terminal network
controller (TNC)
❒ LSI based therefore bulky architecture
❒ TNC and Radio constitute packet radio that handles layer 1
to layer 3 functionalities
❒ Now a laptop integrates packet radio within itself due to
❒ What is an ad hoc network?
❒ Ad hoc Network Applications
❒ Challenges facing ad hoc networks
❒ History of Ad hoc Networks
❒ General Concepts
❒ Introduction to IEEE 802.11
❒ Physical Layers of 802.111-36
General Concepts (1) – Duplexing
❒ The duplexing mechanism refers to how the data transmission and the reception channels are multiplexed:
❍ Can be multiplexed in different time slots
❍ Can be multiplexed in different frequency bands
❒ Time Division Duplex (TDD) refers to multiplexing of transmission and reception in different time periods in the same frequency band
❒ Frequency Division Duplex (FDD) refers to using different frequency bands for uplink and downlink transmissions
❒ FDD – Its possible to send and receive data simultaneously
❒ TDD – Its not possible to send and receive data simultaneously
General Concepts (3) – Network
❒ Distributed Wireless Networks
❍ Ad hoc networks fall in this category
❍ Wireless nodes communicating with each other
without any fixed infrastructure
❍ Terminals have an RF or infrared interface
❍ All data transmission and reception in the same
frequency band (there is no special node to do
the frequency translation)
❍ All ad hoc networks operate in TDD mode
❍ No centralized control for managing the
network e.g. node failures etc.1-38
General Concepts (4) – Network
❒ Centralized Wireless Networks
❍ Cellular networks fall in this category
❍ Also called last-hop networks
❍ Wireless nodes communicating with each other
using fixed infrastructure (Base Station)
❍ Base station acts as an interface to the wireline
❍ Downlink transmission is broadcast – all nodes in
the BS coverage can hear the transmission 1-39
General Concepts (5) – Network
❒ Centralized Wireless Networks
❍ Uplink transmission is shared among nodes so
its multiple access
❍ Can operate in both the TDD or FDD mode
❍ Centralized control for managing the network
❍ BS provides flexibility in MAC design
(admission control, scheduling, QoS provisioning
General Concepts (6) – Slotted
❒ A wireless channel is said to be slotted if
transmission attempts can take place at
discrete instants in time
❒ A slot is the basic time unit – large enough
to carry the smallest packet with overhead
(header + guard band)
❒ A slotted system requires network wide
synchronization – Base station facilitates it
by acting as a time reference
❒ Synchronization is difficult in Ad hoc
❒ What is an ad hoc network?
❒ Ad hoc Network Applications
❒ Challenges facing ad hoc networks
❒ History of Ad hoc Networks
❒ General Concepts
❒ Introduction to IEEE 802.11
❒ Physical Layers of 802.111-42
IEEE 802.11 - Introduction
❒ Well known and adopted standard for wireless LANs
❒ Operates in the unlicensed 2.4 GHZ ISM (Industrial & Scientific & Medical) Band
❒ 802.11 MAC works with different physical layers (infra red as well as spread spectrum)
❒ Compatible with other 802.x standards, e.g. 802.3 (Ethernet), 802.5 (Token ring)
❒ Data rates 1 Mbps (mandatory), 2 Mbps (optional)
❒ Supports real time as well as non-real time applications
❒ Has features for power management to save battery 1-43
Distribution System
802.x LAN
802.11 LAN
802.11 LAN
802.11 - Architecture of an infrastructure
❒Station (STA): terminal with
access mechanisms to the wireless
medium and radio contact to the
access point
❒Basic Service Set (BSS)
❍ group of stations using the
same radio frequency
❒Access Point
❍ station integrated into the
wireless LAN and the
distribution system
❒Portal: bridge to other
(wired) networks
❒Distribution System
❍ interconnection network to
form one logical network (EES:
Extended Service Set) based
on several BSS
IEEE standard 802.11
mobile terminal
access point
fixed terminal
802.11 PHY
802.11 MAC
802.3 MAC
802.3 PHY
802.3 PHY
802.3 MAC
802.11 MAC
802.11 PHY
infrastructure network
802.11 - Layers and functions ❒ PLCP Physical Layer
Convergence Protocol
❍ clear channel
assessment signal
(carrier sense)
❒ PMD Physical Medium
❍ modulation, coding
❒ PHY Management
❍ channel selection, MIB
❒ Station Management
❍ coordination of all
management functions
802.11 Physical Layers
Upper Layers
Logical Link Control
MAC Sublayer
802.11 Physical Layer
❒ Physical layer corresponds to OSI stack
❒ Five different physical layers are proposed
❒ Data link layer split in two or more
sublayers e.g. MAC and Logical link control
❍ MAC allocates the channel
❍ LLC hides differences between different
physical layers to network layer 1-48
802.11 Physical Layer - History
❒ In 1997, only three physical layer technologies
1. Infrared - Uses diffused light (not line of sight). Two speeds: 1 Mbps and 2 Mbps
2. FHSS (Frequency Hopping Spread Spectrum) – Uses part of 2.4 GHz ISM band. Speed 1 – 2 Mbps
3. DSSS (Direct Sequence Spread Spectrum)
- Uses part of 2.4 GHz ISM band. Speed 1 – 2 Mbps
‰ In 1999, two new techniques were introduced to support higher data rates
‰ OFDM (Orthogonal frequency division multiplexing). Speed 54 Mbps
‰ HR – DSSS (High Rate Direct Sequence Spread Spectrum) – 11 Mbps
‰ In 2001, a second OFDM modulation in a
different frequency band from the first one1-49
IEEE 802.11a
❒ OFDM Based
❒ Can deliver up to 54 Mbps in the wider 5
GHz ISM band
❒ 52 Frequency bands (48 for data, 4 for
❒ A form of spread spectrum yet different
from CDMA and FHSS
❒ OFDM is compatible with the HiperLAN/2
❒ Good spectrum efficiency bits/Hz, and
good immunity to multi-path fading1-50
IEEE 802.11b
❒ HR-DSSS Based spread spectrum
❒ Achieves 11 Mbps in the 2.4 GHz band
(Data rates are 1, 2, 5.5, 11 Mbps)
❒ Its not a follow up to 802.11a. It was
approved earlier than 802.11a and came to
market first
❒ Its slower than 802.11a but Its range is 7
times greater than 802.11 a 1-51
IEEE 802.11g
❒ Enhanced version of 802.11a
❒ Approved in Nov. 2001
❒ OFDM based but operates in 2.4 GHz band
❒ In theory can operate at 54 Mbps but lot
slower in practice
❒ 802.11a, 802.11b and 802.11g are called
high speed LANs (Broadband Wireless
FHSS PHY Packet Format
synchronization SFD PLW PSF HEC payload
PLCP preamble PLCP header
80 16 12 4 16 variable bits
❒ Synchronization
❍ synch with 010101... pattern
❒ SFD (Start Frame Delimiter)
❍ 0000110010111101 start pattern
❒ PLW (PLCP_PDU Length Word)
❍ length of payload incl. 32 bit CRC of payload, PLW < 4096
❒ PSF (PLCP Signaling Field)
❍ data of payload (1 or 2 Mbit/s)
❒ HEC (Header Error Check)
❍ CRC with x16+x12+x
DSSS PHY packet format
synchronization SFD signal service HEC payload
PLCP preamble PLCP header
128 16 8 8 16 variable bits
❒ Synchronization
❍ synch., gain setting, energy detection, frequency offset
❒ SFD (Start Frame Delimiter)
❍ 1111001110100000
❒ Signal
❍ data rate of the payload (0A: 1 Mbit/s DBPSK; 14: 2 Mbit/s DQPSK)
❒ Service Length
❍ future use, 00: 802.11 compliant
‰ length of the payload
❒ HEC (Header Error Check)
❍ protection of signal, service and length, x16+x12+x

2.whats is peer to peer networks?

in its simplest form, a peer-to-peer (P2P)network is created when two or more PCs are connected and share resources without going through a separate server computer. A P2P network can be an ad hoc connection—a couple of computers connected via a Universal Serial Bus to transfer files.
In its simplest form, a peer-to-peer (P2P) network is created when two or more PCs are connected and share resources without going through a separate server computer. A P2P network can be an ad hoc connection—a couple of computers connected via a Universal Serial Bus to transfer files. A P2P network also can be a permanent infrastructure that links a half-dozen computers in a small office over copper wires. Or a P2P network can be a network on a much grander scale in which special protocols and applications set up direct relationships among users over the Internet.

10 Best Practices for Cloud Business Intelligence: Enabling the Business
Business driven Business Intelligence (BI) and analytics represent a shift in the enterprise that is
The initial use of P2P networks in business followed the deployment in the early 1980s of free-standing PCs. In contrast to the minimainframes of the day, such as the VS system from Wang Laboratories Inc., which served up word processing and other applications to dumb terminals from a central computer and stored files on a central hard drive, the then-new PCs had self-contained hard drives and built-in CPUs. The smart boxes also had onboard applications, which meant they could be deployed to desktops and be useful without an umbilical cord linking them to a mainframe.
Many workers felt liberated by having dedicated PCs on their desktops. But soon they needed a way to share files and printers. The obvious solution was to save files to a floppy disk and carry the disk to the intended recipient or send it by interoffice mail.
Sneaker Nets
That practice resulted in the term "sneaker net." The most frequent endpoint of a typical sneaker net was the worker who had a printer connected to his machine.
While sneaker nets seemed an odd mix of the newest technology and the oldest form of transportation, the model is really the basis for today's small P2P workgroups.
Whereas earlier centralized computing models and today's client/server systems are generally considered controlled environments in which individuals use their PCs in ways determined by a higher authority, a classic P2P workgroup network is all about openly sharing files and devices.
In general, office and home P2P networks operate over Ethernet (10M bit/sec.) or Fast Ethernet (100M bit/sec.) and employ a hub-and-spoke topology. Category 5 (twisted-pair) copper wire runs among the PCs and an Ethernet hub or switch, enabling users of those networked PCs access to one another's hard drives, printers or perhaps a shared Internet connection.
Both Client and Server
In effect, every connected PC is at once a server and a client. There's no special network operating system residing on a robust machine that supports special server-side applications like directory services (specialized databases that control who has access to what).
In a P2P environment, access rights are governed by setting sharing permissions on individual machines.
For example, if User A's PC is connected to a printer that User B wants to access, User A must set his machine to allow (share) access to the printer. Similarly, if User B wants to have access to a folder or file, or even a complete hard drive, on User A's PC, User A must enable file sharing on his PC. Access to folders and printers on an office P2P network can be further controlled by assigning passwords to those resources
Peer to peer is an approach to computer networking where all computers share equivalent responsibility for processing data. Peer-to-peer networking (also known simply as peer networking ) differs from client-server networking, where certain devices have responsibility for providing or "serving" data and other devices consume or otherwise act as "clients" of those servers.
Characteristics of a Peer Network
Peer to peer networking is common on small local area networks (LANs) , particularly home networks. Both wired and wireless

Computers in a peer to peer network run the same networking protocols and software.Peer networks are also often situated physically near to each other, typically in homes, small businesses or schools. Some peer networks, however, utilize the Internet and are geographically dispersed worldwide.
Home networks that utilize broadband routers are hybrid peer to peer and client-server environments. The router provides centralized Internet connection sharing, but file, printer and other resource sharing is managed directly between the local computers involved.
Peer to Peer and P2P Networks
Internet-based peer to peer networks emerged in the 1990s due to the development of P2P file sharing networks like Napster. Technically, many P2P networks (including the original Napster ) are not pure peer networks but rather hybrid designs as they utilize central servers for some functions such as search.
Peer to Peer and Ad Hoc Wi-Fi Networks

Data explosion throttles the RAN and customer experience
wireless networks support so-called ad hoc connections between devices. Ad hoc Wi-Fi networks are pure peer to peercompared to those utilizing wireless routers as an intermediate device.
Benefits of a Peer to Peer Network
You can configure computers in peer to peerworkgroups to allow sharing of files , printers and other resources across all of the devices. Peer networks allow data to be shared easily in both directions, whether for downloads to your computer or uploads from your computer.
On the Internet, peer to peer networks handle a very high volume of file sharing traffic by distributing the load across many computers. Because they do not rely exclusively on central servers, P2P networks both scale better and are more resilient than client-server networks in case of failures or traffic bottlenecks.

3.why all network using using in 802.11 a/b/an?
BECAUSE  OF  THE  Features
Quality of Service (QoS)
IEEE 802.1p prioritization: delivers data to devices based on the priority and type of traffic
SpectraLink voice priority (SVP) support: prioritizes SpectraLink voice IP packets sent from a SpectraLink NetLink SVP server to SpectraLink wireless voice handsets to help ensure excellent voice quality
Wireless: - L2/L3/L4 classification: IEEE 802.1p VLAN priority, SpectraLink SVP and DiffServ. - Wi-Fi MultiMedia (WMM), IEEE 802.11e EDCF, and Service-Aware priority assigned by VSC. - Maximum VoIP call capacity: 12 active calls on IEEE 802.11a/b/g/n.
Network management: - Fully manageable using HP PCM 3.0 AU1 and HP Mobility Manager 3.0 AU2. - SNMP v2c, SNMP v3, MIB-II with Traps, and RADIUS Authentication Client MIB (RFC 2618). - Embedded HTML management tool with secure access (SSL and VPN). - Scheduled configuration and firmware upgrades from central server.
Diagnostic: - Client event log records association, authentication, and DHCP events. - Packet capture tool for Ethernet and IEEE 802.11 interfaces (PCAP format). - Data rate matrix.
Auto-MDIX: automatically adjusts for straight-through or crossover cables on all 10/100 ports
IEEE 802.3af Power over Ethernet (PoE) support: simplifies deployment and dramatically reduces installation costs by helping to eliminate the time and cost involved in supplying local power at each access point location
Anywhere, anytime wireless coverage: - Single, dual, and tri-radio IEEE 802.11a/b/g access points. - Per-radio software-selectable configuration of frequency bands. - Self-healing, self-optimizing local mesh extends network availability . - Wi-Fi Alliance certified for interoperability with all 802.11a/b/g client devices . - IEEE 802.3af PoE or external power cord on selected models .
Interoperability: Wi-Fi Alliance certifications, including IEEE 802.11g Wi-Fi and WPA2 to help ensure multivendor interoperability
Virtual Service Communities (VSCs): - Up to 16 SSIDs, each with unique MAC address, configurable SSID broadcasts. - Individual security and QoS profiles per VSC. - Configurable DTIM and minimum data rate per VSC. - Each VSC can be mapped to separate IEEE 802.1Q VLANs. - WMM and/or WMM-PS. - Security filter. - IP filter.
AP client access control functions: - IEEE 802.1X authentication using EAP-SIM, EAP-FAST, EAP-TLS, EAP-TTLS, and PEAP. - MAC address authentication using local or RADIUS access lists. - RADIUS AAA using EAP-MD5, PAP, CHAP, and MS-CHAPv2. - RADIUS Client (RFC 2865 and 2866) with location-aware support. - Layer 2 wireless client isolation.
Auto Channel Select (ACS): helps reduce radio co-channel interference by automatically selecting the radio channel with the least interference
Choice of IEEE 802.11i, WPA2, or WPA: locks out unauthorized wireless access by authenticating users prior to granting network access; robust Advanced Encryption Standard (AES) or Temporal Key Integrity Protocol (TKIP) encryption secures the data integrity of wireless traffic
Local wireless bridge client traffic filtering: when enabled, prevents communication between wireless devices associated with the same access point
IEEE 802.1X: provides port-based user authentication with support for Extensible Authentication Protocol (EAP) MD5, TLS, TTLS, and PEAP with choice of AES, TKIP, and static or dynamic WEP encryption for protecting wireless traffic between authenticated clients and the access point  


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