Introduction Wireless Networking Wireless Networking Topologies Module-05B

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Introduction Wireless Networking Wireless
Networking TopologiesModule-05B

• Jerry Bernardini
• Community College of Rhode Island

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Presentation Reference Material

• CWNA Certified Wireless Network Administration
  Official Study Guide
• (PWO-104), David Coleman, David Westcott,
  2009, Chapter-7
• The California Regional Consortium for
  Engineering Advances in Technological Education
  (CREATE) project

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Network Topologies

• Topologies are physical or logical layouts of
  nodes
• Topology-How things are interconnected
• Basic Networking Topologies - Bus Ring Star
  Mesh
• Wireless Topologies are based upon coverage area
• Wireless wide area networks (WWAN)
• Wireless metropolitan area networks(WMAN)
• Wireless personal area networks (WPAM)
• Wireless local area networks (WLAN)

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Wireless Wide Area Networks (WWAN)

• Networks with tens of miles of coverage
• Wireline WANs
• T1, Frame Relay, ATM, MPLS
• WLANs
• Cellular, T-Mobile, Verizon
• GPRS, CDMA, TDMA, GSM technologies
• Wireless point-to-point networks
• IEEE 802.11 was not designed for WWAN

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Wireless Metropolitan Area Network (WMAN)

• Networks with miles of coverage
• Networks for metropolitan areas
• Around Washington DC
• Around Boston
• DC government network
• WMAN technologies
• IEEE 802.16
• WiMAX
• Can provide the last mile coverage

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Wireless Personal Area Network (WPAN)

• Networks with feet (meters) of coverage
• Between Laptops
• Between PDAs
• Between wireless phones
• Headsets
• Technologies used
• Bluetooth
• Infrared
• ZigBee
• Radio
• FHSS

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Wireless Local Area Network (WLAN)

• Networks with hundreds of feet of coverage
• Provides end user access to LANs
• Coverage for buildings and campuses
• Great fit for 802.11 technology
• 802.11 WLAN provides balance of
• Performance
• Cost
• Availability
• Technology evolution

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IEEE 802.11 Topologies

• The purpose of 802.11 is to interconnect radio
  cards
• Every wireless device has a radio card
• All wireless devices are referred to as Stations
  (STA)
• Three topologies defined by 802.11 Service Sets
• Basic Service Set (BSS)
• Extended Service Set (ESS)
• Independent Basic Service Set (IBSS)
• Nonstandard Topologies
• Bridging, Repeating, Workgroup bridging
• Mesh networking (growing in importance)

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Network Communication Modes

• Modes or how STAs can communicate
• Simplex Communications
• One STA transmits, one STA receives
• One way communications
• Half-Duplex Communications
• Both STAs can transmit and receive but not at the
  same time must take turns
• Walkie-talkies
• 802.11 networks
• Full-Duplex Communications
• Both STAs can transmit and receive at the same
  time
• Requires two radio channels
• 802.11 does not support full-duplex

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Basic 802.11 Components

• Wireless Client stations or Wireless devices
  STAs
• Wireless Access Points - APs
• Wireless Bridges
• Wireless Repeaters
• Wireless Controllers

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Access Points

• The Access Point (AP) is the device that
  provides access to the WLAN
• Each BSS has one AP and multiple Aps make an ESS
• Two categories of APs are Fat and Thin Access
  Points
• Thin APs are paired with a wireless LAN switch
  or controller to offer additional functionality
  and centralization over Fat APs.
• Fat (Thick or Smart) APs are "fat" because they
  operate autonomously as members of a
  decentralized WLAN.

3Com Wireless LAN Switch WX1200
3Com AP3750 MAP
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Access Points Market
Belkin APs
Buffalo APs
Linksys APs
Cisco APs
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Autonomous or FAT Access Points

• Traditional wireless LANs use decentralized Fat
  access points
• Manual configuration required to set the power
  level, channel, security and other configurable
  parameters.
• Each access point is individually configured
• Third party software solutions are often needed
  for additional security and management
  capabilities
• For large networks which quickly add to the
  total cost of ownership.

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Autonomous AP Implementation
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Lightweight or Thin Access Points

• Centralized WLANs use a wireless controller to
  manage, process, and configure the RF environment
  
• Centralized WLANs use called thin or lightweight
  APs
• APs communicate directly with the central
  controller with the wired network
• All the functionality and intelligence is
  offloaded to the controller
• This provides a single point of administration
  for various policies relating to security,
  intrusion detection, user roles, and software
  upgrades..

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Thin Access Points Implementation
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Access Point Modes

• APs are small computers with one or more radios
• The AP operating systems are Linux or propriety
• IEEE 802.11 defines three Operational Modes
• Root Mode
• The default mode for most APs
• Provides wireless clients access to the WLAN
• Bridge Mode
• Used to create a link between two or more APs
• Repeater Mode
• Used to extend the range of a WLAN beyond normal
  boundaries

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Access Point Features

• Support of various IEEE 802.11 standards
• FHSS, DSSS, OFDM, 802.11a,b, g, n
• Support for various security standards
• IEEE 802.11i, WEP, WPA, WPA2, PSK, RADIUS
• Support for QoS extensions
• Wireless Multimedia (WMM), VoWLAN
• Fixed or Detachable Antenna
• Omni-directional, Directional
• Filtering
• MAC, Protocol
• Variable Power
• Percent of Max or Actual Levels

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Power Over Ethernet (PoE) Support

• Found on Enterprise and not on SOHO APs
• Primary benefit is ability to install APs where
  no AC power is present
• IEEE 802.3af standard for PoE
• PoE is supply by injectors or switches

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PoE Options and Power Source Equipment(PSE)
Active/PSE Switch
PD Access Point
Pins 4-5 Power(48v) Pins 7-8 Power
1
DC Power
CAT-5e Ethernet
PD Access Point
2
Switch
AC Power
DC Power
CAT-5e Ethernet
PSE Injector
Access Point
DCPower
3
Switch
AC Power
DC Power
CAT-5e Ethernet
PSE Injector
Tap/Splitter
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Wireless Bridges

• Provides a link between two WLAN segments
• Not full described by IEEE 802.11
• Vendor dependent
• Two Modes Root and Non-root

Point-to-Point
Root
Non-Root
Non-Root
Root
Non-Root
Point-to-Mulitpoint
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WLAN Bridge Modes and Components

• Root Mode A bridge that acts as the hub to a
  group of bridges.
• Only One Root-Bridge for PtP or PtMP links
  (important for tests)
• For PtP link one Root-Bridge and one Non-Root
  Bridge
• Non-Root Mode A member bridge of a group that
  is not the Root Bridge.
• Can also function as a standard AP
• Can function as a repeater

3Com WLAN Bridge
Proxim Quick Bridge 11
Cisco Aironet 1400
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Bridge Application School District
Bode Elementary Yagi
Lincoln Elementary Yagi
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Residential WLAN Gateways

• Same as SOHO wireless routers
• Support of various IEEE 802.11 standards
• FHSS, DSSS, OFDM, 802.11a,b, g, n
• Support for various security standards
• IEEE 802.11i, WEP, WPA, WPA2, PSK, RADIUS
• Built in firewall features
• Packet and MAC Filtering
• Switched Ethernet ports
• DHCP
• NAT and PAT

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Enterprise WLAN
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Enterprise Wireless Gateways

• Enterprise Wireless Gateway is a powerful
  device that interfaces between the enterprise
  network and the corporate firewall.
• HTML ? WML
• Authentication, Filtering, and Security
• Traffic Management, QoS
• Mobile Addressing

Vernier IS 6500p
BlueSecure ControllerBSC 2100
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Enterprise Wireless Gateways
Enterprise Server
Enterprise Gateway
Router
Switch
Access Points
Wireless Clients
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Voice Over IP WLAN (VoWLAN)

• Telephone communication using a WLAN requires
  latency and QoS considerations
• Special equipment is required
• VoWLAN phone (phones that will connect to WLAN)
• WLAN infrastructure with QoS (low latency and
  Protocol management)
• Call management (PBX for IP phones)
• Voice gateway for outside calls
• IP phones associate with APs rather than cellular
  towers

Linksys
Siemens
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Client Stations and Adapters
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Service Set Identifiers - SSID and BSSID

• SSID -Service Set Identifier is a 1-32 byte
  alphanumeric sequence that uniquely names an ESS
  (the network name).
• Any SSID or Null SSID is a blank SSID used to
  associate with anyone.
• BSSID- Basic Service Set Identifier is a 48-bits
  that uniquely identifies a BSS

AP
Wired LAN
BSA Basic service Area Physical Coverage Area
ESS Id SSID
BSS Id BSSID
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Basic Service Set (BSS)
BSS - The Basic Service Set is a term used to
describe the collection of Stations which may
communicate together within an 802.11 WLAN.

• Basic Service Set (BSS) Group of wireless
  devices served by single AP
• infrastructure mode
• BSS must be assigned unique identifier
• Service Set Identifier (SSID)
• Serves as network name for BSS
• Basic Service Area (BSA) Geographical area of a
  BSS
• Max BSA for a WLAN depends on many factors
• Dynamic rate shifting As mobile devices move
  away from AP, transmission speed decreases

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Basic Independent Basic Service Set (BSSID)

• Independent Basic Service Set (IBSS) Wireless
  network that does not use an AP
• Wireless devices communicate between themselves
• Peer-to-peer or ad hoc mode
• BSS more flexible than IBSS in being able to
  connect to other wired or wireless networks
• IBSS useful for quickly and easily setting up
  wireless network
• When no connection to Internet or external
  network needed

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Extended Service Set (ESS)

• ESS - is comprised of a number BSSs
• ESS stations must have the same SSID
• The BSSID is the name of the BSS (not same as
  SSID)
• APs can be positioned so that cells overlap to
  facilitate roaming
• Wireless devices choose AP based on signal
  strength
• Stations going from one BSS to another will deal
  with Handoff

ESS SSID
Wired LAN
BSS2 (BSSID2)
BSS3 (BSSID3)
BSS1 (BSSID1)
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Wireless Mesh Access Points

• Mesh APs associate with multiple APs
• Association between APs is limited by vendor
  (3-5)
• Currently vendor dependent
• Clients can reach destinations thru multiple APs
• APs route packets to ovoid failures and optimal
  paths
• Mesh Networks are more resilient
• Not every AP has to be connected to a wired
  network
• Self-Healing, Self-Configuring using Layer-2
  Protocol
• New standard IEEE 802.11s will allow
  interoperability between vendors

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Wireless Mesh Network Implementation
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Reassociation
Wired LAN
Access Points
1
2
Reassociation Request
1
Link Fading
Wireless Clients
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Load Balancing or Sharing
Wired LAN
Access Points
1
2
2
2
1
1
Wireless Clients
1
2
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WLAN IP Addressing

• In standard networking, IP protocol responsible
  for moving frames between computers
• Network layer protocol
• TCP/IP works on principle that each network host
  has unique IP address
• Used to locate path to specific host
• Routers use IP address to forward packets
• Prohibits mobile users from switching to another
  network and using same IP number
• Users who want to roam need new IP address on
  every network

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Infrastructure Mode
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Channel reuse
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Flip flop between access points
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WLAN Design Models

• Point-to-Point (PtP)
• Point-to-Multipoint (PtMP)

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WLAN Modes

• Single MAC Model
• Edge, Autonomous, Stand-Alone, Fat-AP
• Split MAC Model
• Centralized, Thin-AP
• Mesh Network
• Distributed, Multipath, IEEE 802.11s

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Single MAC Model
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Split MAC Model
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WLAN Model Evolution

• Intelligent Edge(Distribution)
• Quick to setup but for small-medium networks
• Difficult to mage for large networks
• WLAN Network Management Systems
• Centralized Management Distribution Processing
• For large networks
• Centralized WLAN Architecture (Split MAC)
• For large networks with centralized controller
• Large amount of wiring needed
• Distributed Data Forwarding (DDF) WLAN
• Similar to Split MAC but uses Fat-AP
• Unified WLAN Architecture
• Wireless built in to every thing including
  switches

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WLAN Power Management Features

• Active Mode
• No power saving but improved station and AP
  performance
• For desktops and line powered laptops
• Power Save Mode
• Dozing and Wake modes
• Switches to wake to check for frames
• WMM Power Save
• U-APSD Unscheduled Automatic Power-Save Delivery
• This is an industry certification
• IEEE 802.11e-2005

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Power Management

• A WLAN laptop must remain awake in order to
  receive network transmissions
• Original IEEE 802 standard assumes stations
  always ready to receive network messages
• Power management Allows mobile devices to
  conserve battery life without missing
  transmissions
• Transparent to all protocols
• Differs based on WLAN configuration
• AP records which stations awake and sleeping
• Buffering If sleeping, AP temporarily stores
  frames

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Power Management

• At set times AP send out beacon to all stations
• Contains traffic indication map (TIM)
• At same time, all sleeping stations switch into
  active listening mode
• Power management in ad hoc mode
• Ad hoc traffic indication message (ATIM) window
  Time at which all stations must be awake
• Wireless device sends beacon to all other devices
• Devices that previously attempted to send a frame
  to a sleeping device will send ATIM frame
  indicating that receiving device has data to
  receive and must remain awake

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Continuous Aware Mode

• Constantly Awake Mode provides the best
  performance allowing the client a strong
  connection between the wireless card and the AP
  however, it also rapidly drains the clients
  battery, resulting in shorter battery life.

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Power Management with TIM/DTIM/ATIM

• Traffic Indication Map (TIM)
• A table stored on the AP of all STAs in Power
  Save mode
• TIM is used to determine which STAs require
  frame buffering
• Every Beacon contains a TIM
• Delivery Traffic Indication Message (DTIM)
• Used to manage STAs and to program wakeup
• Sent on every few (third or some interval)Beacon
• Ad Hoc Traffic Indication Message (ATIM)
• Use to power manage IBSS