802.1 internetworking

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• 802.1 internetworking
• 802.2 LLC
• 802.3 Ethernet/CSMA/CD
• 802.4 token bus
• 802.5 token ring
• 802.6 DQDB used in SMDS for MAN
• 802.7 Broadband LAN
• 802.8 technical advisory group on fiber
  optics/FDDI
• 802.9 Integrated services Local Area Network
• 802.10 Interoperable LAN/MAN security (SILS)

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• WIRELESS LAN WLAN
• 802.11

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INTRO

• Wireless LAN tech is rapidly becoming crucial
  component of computer networks and is growing by
  leaps and bound. Thanks to the finalization of
  the IEEE 802.11 wireless LAN standard, wireless
  technology has emerged from the world of
  proprietary implementations to become an open
  solution for providing mobility as well as
  essential network services where wire line
  installations proved impractical. The inclusion
  of the newer IEEE 802.1la and 802.11b versions of
  the standard offers a firm basis for
  high-performance wireless LANs. Now companies and
  organizations are investing in wireless networks
  at a higher rate to take advantage of mobile,
  real-time access to information.

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• Most wireless LAN suppliers now have 802.11
  compliant products, allowing companies to
  realize wireless network applications based on
  open systems. The move toward 802.11
  standardization is lowering prices and enabling
  multi-vendor wireless LANs to interoperate. This
  is making the implementation of wireless networks
  more feasible than before, creating vast business
  oppurtinities for system implementation companies
  and consultants. However, many end user companies
  and system integrators have limited knowledge and
  experience in developing and implementing
  wireless network systems. In many cases, there is
  also confusion over the capability and
  effectiveness of the 802.11 standard.

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• The implementation of wireless networks is much
  different than that of traditional wired
  networks. In contrast to Ethernet, a wireless LAN
  has a large number of setup parameters that
  affect the performance and interoperability of
  the network. An engineer designing the network
  and the person installing the network must
  understand these parameters and how they affect
  the network.

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WLANs benefit what? Why?

• Mobility
• Installation in difficult-to-wire areas
• Increased reliability
• Reduced installation time
• Long term cost savings

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WLANs benefit mobility

• Easy to move physically while using an appliance,
  such as a handheld PC or data collector pda.
• Many jobs require workers to be mobile, such as
  inventory clerks, healthcare workers, policemen,
  and emergency care specialist.
• Mobility result to mobile application
• Mobile applications requiring wireless networking
  include those that depend on real-time access to
  data usually stored in centralized databases

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• Mobility result to mobile application
• Mobile applications requiring wireless networking
  include those that depend on real-time access to
  data usually stored in centralized databases
• E.g. in retail store for accurate and efficient
  price markdowns, ppl use wireless networks to
  interconnect handheld bar code scanners and
  printers to data bases having current price
  information.
• Another e.g. formula 1 and indy race cars have
  sophisticated data acquisition sytems that
  monitor the various onboard system in the car.
  When the cars come around the track and pass
  their respective teams in the pit, this
  information is downloaded to a central computer,
  thereby enabling real-time analysis of the
  performance of the racecar.

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WLAN benefit Installation in difficult-to-wire
areas

• The implementation of wireless networks offers
  many tangible cost savings when performing
  installations in difficult to wire areas.
• E.g. two building that separate by
  river/road/railroad track (fig 1.2). A wireless
  soln may be much more economical than installing
  physical cable or leasing communications
  circuits, such as T1 service or 56kbps lines.
• To apply wireless connection in this situation
  may be cost a lot of money. But it will benefit
  in the long run. (long term investment)

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Building A
Building B
River, road or Railroad tracks
Wireless link
Fig. 1.2 wireless networks make it cost effective
to provide network Connectivity in situations
that are difficult to wire
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• Another good reason to apply wireless soln is due
  to health risk when the workers try to install
  network cabling in some building area which
  contain asbestos particles.
• Some org remove the asbestos first, making it
  safe to install cabling. This process is very
  expensive. It is better to spend money on setting
  up wireless networking rather than wasting money
  to remove the asbestos.
• Wireless n/w to preserve historical sites
• In some cases, it might be impossible to install
  cabling. Some municipalities, for e.g. may
  restrict us from permanently modifying older
  facilities with historical value. This could
  limit the drilling of holes in walls during the
  installation of n/w cabling and outlets. In that
  situation, a wireless network might be the only
  soln.

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WLAN benefit Increased Reliability

• A problem inherent to wired network is downtime
  due to cable faults. E.g. moisture erodes
  metallic conductors via water intrusion during
  storms and accidental spillage or leakage of
  liquids.
• With wired networks, a user might accidentally
  break his network connector when trying to
  disconnect his PC from the network to move it to
  a different location.
• Imperfect cable join can cause signal reflections
  that result in unexplainable errors. The
  accidental cutting of cables can bring down a
  network immediately.
• An advantage of wireless networking, therefore,
  results from the use of less cable. This reduces
  the downtime of the network and the costs related
  with replacing cables.

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WLAN benefit reduced installation time

• The deployment of wireless network greatly
  reduces the need for cable installation, making
  the network available for use much sooner.
• But the isntallation of cabling is often a
  time-consuming activity. For LAN, installer must
  pull twisted-pair wires or optical fiber above
  the ceiling and drop cables through walls to
  network outlets that they must affix to the wall.
  These task can take days or weeks depending on
  the size of the installation.
• What about to install optical fiber which involve
  digging trenches it is messy task task that
  could take weeks or possibly months to finish it.

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WLAN applications

• Retail
• Warehousing
• Healthcare
• Hospitality
• Home and small office
• General enterprise systems
• Wireless services

All student pls visit this site
www.wireless-nets.com/cases.htm
This site includes a collection of wireless
network paper, case studies And breaking news
about wireless network mostly about WLAN.
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Wireless LAN technology

• There are Several WLAN specifications and
  standards that we can choose from when developing
  WLAN products or integrating WLAN solutions into
  corporate systems. For e.g. HiperLAN, HomeRF
  SWAP, and Bluetooth,
• The emphasis of this lecture is on IEEE 802.11
  compliant wireless LANs because 802.11 is
  expected to continue being the preferred standard
  for supporting WLANs applications.
• Other technologies may become stronger
  competitors to 802.11 in the future.

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HiperLAN

• Began in Europe somewhere in 1996 by European
  Telecommuniations Standards Institute (ETSI)
• Began with hiperLAN/1, old version, operates in
  the 5GHz radio band at up to 24MBps.
• Similar to ethernet, HiperLAN/1 shares access to
  the WLAN among end user devices via a
  connectionless protocol. HiperLAN/1 also provides
  quality of services (QoS) support for various
  needs of data, video, voice and images.
• ETSI is currently improving HiperLAN/2 under an
  organization called the HiperLAN/2 Global Forum
  (H2GF).
• HiperLAN/2 will operate in the 5GHz band at up to
  54Mbps using a connection-oriented protocol for
  sharing access among end user devices.

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• HiperLAN/2 will include QoS support and be
  capable of carrying ethernet frames, ATM cells
  and IP packet.
• Refer to HiperLAN/2 Global forum web site at
• http//www.hiperlan2.com
• For additional details on the HiperLAN/2
  Specification.
• Compare to japanese version hiperLAN/2 called
  HisWANa.

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HomeRF SWAP

• In march 1998, the homeRF Working Group (HRFWG)
  announced its existence and set out to provide an
  open industry specifiaction, Shared wireless
  access protocol (SWAP), for wireless digital
  communication between PCs and consumer electronic
  devices within the home.
• The SWAP specification defines a common wireless
  interface supporting voice and data at 1MBps and
  2MBps data rates using frequency hopping spread
  spectrum modulation in the 2.4Ghz frequency band.

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• HRFWG is currently developing a 10Mbps version of
  SWAP based on recent Federal Communication
  Commision (FCC) approval for wider bandwidth for
  frequency hopping systems.
• Refer HomeRF website for more details
• http//www.homerf.org

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Bluetooth

• Bluetooth is a specification published by the
  bluetooth special interest group (SIG), with some
  big promoters including 3COM, ericsson, IBM,
  Intel, Lucent, Microsoft, Motorola and etc.
• Bluetooth isnt wireless a WLAN. Instead, it is a
  wireless personal area network (PAN), which is a
  subset of a WLAN.
• Bluetooth operates at 1Mbps, with relatively low
  power over short ranges using frequency hopping
  spread spectrum in the 2.4Ghz frequency band.
  Refer to bluetooth.com for more details.

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IEEE 802.11

• Somewhere in 1997, IEEE finalized the initial
  standard for wireless LANs IEEE 802.11. This
  standard specifies a 2.4Ghz operating frequency
  with data rates of 1 and 2 Mbps. The initial
  802.11 standard defines two forms of spread
  spectrum modulation frequency hopping (802.11
  FHSS) and direct sequence (802.11 DSSS).
• In late 1999, the IEEE published two supplements
  to the 802.11 standard. 802.11a and 802.11b.

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802.11a

• The 802.11a standard defines operation at up to
  54Mbps using orthogonal frequency division
  multiplexing (OFDM) modulation in the roomy 5Ghz
  frequency band.
• The 802.11a standard has a wide variety of
  high-speed data rates available 6, 9, 12, 18,
  24, 36, 48 and 54Mbps.
• It is mandatory for all products to have 6Mbps,
  12Mbps, and 24Mbps rates. Products implementing
  the 802.11a standard should begin appearing on
  the market in the late 2001.

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802.11b

• (commonly known as Wi-Fi) describes the
  wireless networking standard for WLANs that
  operate in the 2.4 GHz radio band (ISM frequency
  band). 902Mz-5.85Ghz
• 802.11b-based WLANs are far more common than
  802.11a or 802.11g networks and can achieve a
  maximum data rate of 11 Mbps per second at
  distances up to approximately 300 feet.
• 802.11 b was the first WLAN technology offered to
  consumers and enabled the creation of instant
  wireless networks in offices and homes.
• Devices certified by Wi-Fi Alliance bear the
  official Wi-Fi logo. Most wireless LANs
  implemented today comply with the 802.11b version
  of the standard.

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802.11g

• IEEE 802.11g is a new standard, describing a
  wireless networking method for WLANs that
  operates in the 2.4 radio band (ISM frequency
  band). Industrial-Scientific-Medical
• using OFDM (Orthogonal Frequency Division
  Multiplexing) technology 802.11g-based WLANs can
  achieve a maximum speed of 54 Mbps.
• 802.11g-compliant equipment, such as wireless
  access points, can provide simultaneous WLAN
  connectivity for both 802.11g and 802.11b
  equipment.

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Terms widely used in WLAN

• Spread spectrum
• Frequency Hopping Spread Spectrum (FHSS)
• Direct Sequence Spread Spectrum (DSSS)
• Orthogonal Frequency Division Multiplexing (OFDM)

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Spread Spectrum Technology

• Most wireless LAN systems use spread-spectrum
  technology, a wideband radio frequency technique
  developed by the military for use in reliable,
  secure, mission-critical communications systems.
• Spread-spectrum is designed to trade off
  bandwidth efficiency for reliability, integrity,
  and security.
• In other words, more bandwidth is consumed than
  in the case of narrowband transmission, but the
  tradeoff produces a signal that is, in effect,
  louder and thus easier detect, provided that the
  receiver knows the parameters the spread-spectrum
  signal being broadcast.
• If a receiver not tuned to the right frequency, a
  spread-spectrum signal looks like background
  noise. There are two types of spread spectrum
  radio
• frequency hopping and direct sequence.

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Frequency-hopping Spread-Spectrum (FHSS)

• Frequency-hopping spread-spectrum (FHSS) uses a
  narrowband carrier that changes frequency in a
  pattern known to both transmitter and receiver.
• Properly synchronized, the net effect is to
  maintain a single logical channel.
• To an unintended receiver, FHSS appears to be
  short-duration impulse noise.

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Direct Sequence Spread Spectrum (DSSS)

• Direct-sequence spread-spectrum (DSSS) generates
  a redundant bit pattern for each bit to be
  transmitted. This bit pattern is called a chip
  (or chipping code).
• The longer the chip, the greater the probability
  that the original data can be recovered (and, of
  course, the more bandwidth required).
• Even if one or more bits in the chip are damaged
  during transmission statistical techniques
  embedded in the radio can recover the original
  data without the need for retransmission.
• To an unintended receiver, DSSS appears as
  low-power wideband noise and is rejected
  (ignored) by most narrowband receivers.

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Orthogonal Frequency Division Multiplexing (OFDM)

• Orthogonal Frequency Division Multiplexing (OFDM)
  is a method that allows to transmit high data
  rates over extremely hostile channels at a
  comparable low complexity.
• OFDM has been chosen as the transmission method
  for the European radio (DAB) and TV (DVB-T)
  standard. Due to its numerous advantages it is
  under Discussion for future broadband application
  such as wireless ATM as well.

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• Orthogonal FDM's (OFDM) spread spectrum technique
  distributes the data over a large number of
  carriers that are spaced apart at precise
  frequencies. This spacing provides the
  "orthogonality" in this technique which prevents
  the demodulators from seeing frequencies other
  than their own. The benefits of OFDM are high
  spectral efficiency, resiliency to RF
  interference, and lower multi-path distortion.
  This is useful because in a typical terrestrial
  broadcasting scenario there are
  multipath-channels (i.e. the transmitted signal
  arrives at the receiver using various paths of
  different length). Since multiple versions of the
  signal interfere with each other (inter symbol
  interference (ISI)) it becomes very hard to
  extract the original information.
• OFDM in detail you can get at
• www.iss.rwth-aachen.de/Projekte/Theo/OFDM/www_ofdm
  .html
• http//www.wave-report.com/tutorials/OFDM.htm

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Other technology Infrared Technology

• Commonly used but still not popular. I dont know
  why.
• Maybe because little used in commercial wireless
  LANs,
• Infrared (IR) systems use very high frequencies,
  just below visible light in the electromagnetic
  spectrum, to carry data.
• Like light, IR cannot penetrate opaque objects
• is either directed (line-of-sight) or diffuse
  technology.
• Inexpensive directed systems provide very limited
  range (3
• ft) and typically are used for personal area
  networks but occasionally are used in specific
  wireless LAN applications.
• High performance directed IR is impractical for
  mobile
• users and is therefore used only to implement
  fixed subnetworks.
• Diffuse (or reflective) IR wireless LAN systems
  do
• not require line-of-sight, but cells are limited
  to individual
• rooms. Developed by http//www.irda.org/

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Wireless LAN implications

• Project managers and design engineer should be
  aware, the following potential problems from the
  implementation and use of wireless networking
• Multipath propagation
• Path loss
• Radio signal interference
• Battery longevity
• System interoperability
• Network security
• Connection problems
• Installation issues
• Health risk

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Multipath propagation

• As fig 1.3 illustrates, transmitted signals can
  combine with reflected ones to corrupt the signal
  detected by the receiver.
• This is known as multipath propagation. Delay
  spread is the amount of delay experienced by the
  reflected signals compared to the primary signal.
  As delay spread increases, the signal at the
  receiver becomes more distorted and possibly
  undetectable even when the transmitter and
  receiver are within close range.

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Fig 1.3 multipath propagation decreases the
quality of the signal at the receiver
Office furniter
Wlan receiver
WLAN transmitter
Office wall
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• Multipath propagation can be a significant
  problem, especially with indoor applications.
• Often furniture, walls, and machinery are
  obstacles that can redirect parts of the
  transmitted signal.
• WLAN manufacturers compensate for the effects of
  multipath propagation by using special processing
  techniques.
• As e.g., equalization and antenna diversity are
  methods for reducing the number of problems
  arising from multipath propagation.

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Path loss

• Path loss between the transmitter and receiver is
  a key consideration when designing a wireless LAN
  soln.
• Expected levels of path loss, based on the range
  between the transmitter and receiver, provide
  valuable info when determining requirements for
  transmit power levels, receiver sensitivity, and
  signal-to-noise ratio (SNR).
• Actual path loss depends on the transmit
  frequency, and it grows exponentially as the
  distance increases between the transmitter and
  receiver.
• With typical indoor applications, the path loss
  increases approx 20dB every receiver.

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Radio Signal Interference

• The process of transmitting and receiving radio
  and laser signals through the air makes wireless
  systems vulnerable to atmospheric noise and
  transmission from other systems.
• In addition, wireless networks can interfere with
  other nearby wireless networks and radio wave
  equipment.
• Radio-based LAN can experience inward
  interference from the harmonics of transmission
  systems or other products using similar radio
  frequencies in the LAN.
• E.g. microwave ovens operate in the S band
  (2.4GHz) that many WLAN use to transmit and
  receive. These signals result in delays to the
  user by either blocking transmission from
  stations on the LAN or causing bit errors to
  occur in data being sent. These types of
  interference can limit the areas in which you can
  deploy a wireless network.

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Techniques for reducing interference

• When dealing with interference, we should
  coordinate the operation of radio-based wireless
  network products with our companys frequency mgt
  organization, if one exists.
• Govt org and most hospitals generally have ppl
  who manage the use of transmitting devices. This
  coordination will avoid potential interference
  problems.
• For. E.g. the military does not follow the same
  frequency allocations is issued by the FCC. (FCC
  deals with commercial sector and the military has
  its own frequency mgt process.)

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Network Security

• The functionality of a wireless network
  corresponds to the lowest levels of the network
  architecture and does not include other
  functions, such as end-to-end connection
  establishment or login services that higher
  layers satisfy.
• Therefore, the only security issues relevant to
  wireless networks are those dealing with these
  lower architectural layers, such as data
  encryption.

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Security threats

• The main security issue with wireless networks,
  is that they intentionally propagate data over an
  area that may exceed the limits of the area the
  organization physically controls.
• For instance, radio waves easily penetrate
  building walls and are receivable from the
  facilitys parking lot and possibly a few blocks
  away. Someone can passively retrieve your
  companys sensitive info by using the same
  wireless NIC from this distance without being
  noticed by network security personnel (see fig
  1.5).
• This requires, though, that the intruder obtain
  the network access code necessary to join the
  network.

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Fig 1.5 the passive reception of wireless
network data is much easier than with wired
network
Passive reception by another business
Building B
Building A
Public road
Passive reception on public access
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How to overcome it? security safeguard

• Wirelessnetwork vendors solve most security
  problems by restricting access to the data .
• Most products require us to establish a network
  access code and set the code within each
  workstation. A wireless station will not process
  the data unless its code is set to the same
  number as the network.
• Some vendors also offer encryption as an option.

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Application connectivity problems

• The use of traditional wire-base protocols over
  wireless networks introduces problems with
  maintaining connections between the users
  appliance and the application residing on a
  server.
• TCP/IP for e.g. provides very reliable
  connections over wired networks such as ethernet
  and token ring. Over wireless network, however,
  TCP/IP is susceptible to losing connection,
  especially when the appliance is operating in an
  area with marginal wireless network coverage.
• A solution to this problem is to use wireless
  middleware software, which provides intermediate
  communications between the end user devices and
  the application software located on a host or
  server. The middleware enables highly efficient
  and reliable communications over the wireless
  network, while maintaining appropriate
  connections to application software and database
  on the server/host via the more reliable wired
  LAN.

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• The mobile nature of wireless networks can offer
  addressing problems as well. Most networks
  require the IP address loaded in the users
  appliance to be within a specific address range
  to maintain proper connections with applications.
• When a user roams from one IP subnet to another
  with a wireless appliance, the appliance and the
  application may lose the capability to connect
  with each others.
• As a result, implementers should consider the use
  of MobileIP as a means of maintaining
  connectivity while traversing different IP
  domains.

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Installation issues

• With wired networks, planning the installation of
  cabling is fairly straightforward. When it is
  properly connected, the transmission is always
  there. (functioning at its best)
• A radio-based wireless LAN installation is not as
  predictable. It is difficult if not impossible to
  design the wireless system by merely inspecting
  the facility.
• Predicting the way in which the contour of the
  building will affect the propagation of radio
  waves is difficult.

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• Omni-directional antennas propagate radio radio
  waves in all direction if nothing gets in the
  way.
• Walls, ceilings, and other obstacle attenuate the
  signals more in one direction than the other and
  even cause some waves to change their paths of
  transmission. Even the opening of a bathroom door
  can change the propagation pattern. These event
  cause the actual radiation pattern to distort,
  taking on a jagged appearance.
• To avoid installation problems, an organization
  should perform propagation tests to assess the
  coverage of the network. Neglecting to do so may
  leave some users outside of the propagation area
  of wireless servers and access point.
• Propagation tests give us the info necessary to
  plan wired connections between access points
  allowing coverage over applicable areas.