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Introduction Wireless Networking Wireless Networking Topologies Module-05B

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Introduction Wireless Networking Wireless Networking Topologies Module-05B Jerry Bernardini Community College of Rhode Island * Wireless Networking J. Bernardini * – PowerPoint PPT presentation

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Title: Introduction Wireless Networking Wireless Networking Topologies Module-05B


1
Introduction Wireless Networking Wireless
Networking TopologiesModule-05B
  • Jerry Bernardini
  • Community College of Rhode Island

2
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

3
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)

4
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

5
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

6
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

7
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

8
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)

9
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

10
Basic 802.11 Components
  • Wireless Client stations or Wireless devices
    STAs
  • Wireless Access Points - APs
  • Wireless Bridges
  • Wireless Repeaters
  • Wireless Controllers

11
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
12
Access Points Market
Belkin APs
Buffalo APs
Linksys APs
Cisco APs
13
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.

14
Autonomous AP Implementation
15
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..

16
Thin Access Points Implementation
17
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

18
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

19
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

20
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
21
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
22
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
23
Bridge Application School District
Bode Elementary Yagi
Lincoln Elementary Yagi
24
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

25
Enterprise WLAN
26
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
27
Enterprise Wireless Gateways
Enterprise Server
Enterprise Gateway
Router
Switch
Access Points
Wireless Clients
28
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
29
Client Stations and Adapters
30
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
31
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

32
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

33
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)
34
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

35
Wireless Mesh Network Implementation
36
Reassociation
Wired LAN
Access Points
1
2
Reassociation Request
1
Link Fading
Wireless Clients
37
Load Balancing or Sharing
Wired LAN
Access Points
1
2
2
2
1
1
Wireless Clients
1
2
38
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

39
Infrastructure Mode
40
Channel reuse
41
Flip flop between access points
42
WLAN Design Models
  • Point-to-Point (PtP)
  • Point-to-Multipoint (PtMP)

43
WLAN Modes
  • Single MAC Model
  • Edge, Autonomous, Stand-Alone, Fat-AP
  • Split MAC Model
  • Centralized, Thin-AP
  • Mesh Network
  • Distributed, Multipath, IEEE 802.11s

44
Single MAC Model
45
Split MAC Model
46
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

47
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

48
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

49
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

50
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.

51
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
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