Introduction Wireless Networking Wireless Networking Topologies Module-05B Jerry Bernardini Community College of Rhode Island 6/19/2015Wireless Networking J. Bernardini1

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 6/19/2015Wireless Networking J. Bernardini2

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) 6/19/2015Wireless Networking J. Bernardini3

Wireless Wide Area Networks (WWAN) Networks with ten’s 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 was not designed for WWAN 6/19/2015Wireless Networking J. Bernardini4

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 – WiMAX Can provide “the last mile” coverage 6/19/2015Wireless Networking J. Bernardini5

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 6/19/2015Wireless Networking J. Bernardini6

Wireless Local Area Network (WLAN) Networks with hundred’s of feet of coverage Provides end user access to LANs Coverage for buildings and campuses Great fit for technology WLAN provides balance of: – Performance – Cost – Availability – Technology evolution 6/19/2015Wireless Networking J. Bernardini7

IEEE Topologies The purpose of 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 – 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) 6/19/2015Wireless Networking J. Bernardini8

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 – networks Full-Duplex Communications – Both STAs can transmit and receive at the same time – Requires two radio channels – does not support full-duplex 6/19/2015Wireless Networking J. Bernardini9

Basic Components Wireless Client stations or Wireless devices –STAs Wireless Access Points - APs Wireless Bridges Wireless Repeaters Wireless Controllers 6/19/2015Wireless Networking J. Bernardini10

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 AP’s are paired with a wireless LAN switch or controller to offer additional functionality and centralization over Fat AP’s. Fat (Thick or Smart) AP’s are "fat" because they operate autonomously as members of a decentralized WLAN. 3Com Wireless LAN Switch WX1200 3Com AP3750 MAP

Access Points Market 6/19/2015Wireless Networking J. Bernardini12 Cisco APs Linksys APs Buffalo APs Belkin APs

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. 6/19/2015Wireless Networking J. Bernardini13

Autonomous AP Implementation 6/19/2015Wireless Networking J. Bernardini14

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.. 6/19/2015Wireless Networking J. Bernardini15

Thin Access Points Implementation 6/19/2015Wireless Networking J. Bernardini16

Access Point Modes APs are small computers with one or more radios The AP operating systems are Linux or propriety IEEE 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 6/19/2015Wireless Networking J. Bernardini17

Access Point Features Support of various IEEE standards – FHSS, DSSS, OFDM, a,b, g, n Support for various security standards – IEEE i, 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 6/19/2015Wireless Networking J. Bernardini18

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 6/19/2015Wireless Networking J. Bernardini19

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 Wired LAN AP ESS Id = SSID BSS Id = BSSID BSA Basic service Area –Physical Coverage Area

Basic Service Set (BSS) 21 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 BSS - The Basic Service Set is a term used to describe the collection of Stations which may communicate together within an WLAN.

Basic Independent Basic Service Set (BSSID) 22 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

Extended Service Set (ESS) ESS - is comprised of a number BSS’s 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 Wired LAN BSS1 (BSSID1) ESS SSID BSS2 (BSSID2) BSS3 (BSSID3)

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 s will allow interoperability between vendors 6/19/2015Wireless Networking J. Bernardini24

Wireless Mesh Network Implementation 6/19/2015Wireless Networking J. Bernardini25

Reassociation Wireless Clients Access Points Wired LAN 1 12 Link Fading Reassociation Request

Load Balancing or Sharing Wireless Clients Access Points Wired LAN

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 28

CWNA Guide to Wireless LANs, Second Edition 29 Infrastructure Mode

CWNA Guide to Wireless LANs, Second Edition 30 Channel reuse

CWNA Guide to Wireless LANs, Second Edition 31 Flip flop between access points

WLAN Design Models 6/19/2015Wireless Networking J. Bernardini32 Point-to-Point (PtP) Point-to-Multipoint (PtMP)

WLAN Modes Single MAC Model – Edge, Autonomous, Stand-Alone, Fat-AP Split MAC Model – Centralized, Thin-AP Mesh Network – Distributed, Multipath, IEEE s 6/19/2015Wireless Networking J. Bernardini33

Single MAC Model 6/19/2015Wireless Networking J. Bernardini34

Split MAC Model 6/19/2015Wireless Networking J. Bernardini35

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 6/19/2015Wireless Networking J. Bernardini36

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 e /19/2015Wireless Networking J. Bernardini37

Power Management 38 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

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 39

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 client’s battery, resulting in shorter battery life.

Power Management with TIM/DTIM/ATIM Traffic Indication Map (TIM) – A table stored on the AP of all STA’s in Power Save mode – TIM is used to determine which STA’s 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 6/19/2015Wireless Networking J. Bernardini41