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REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE 802.11 standards  The 802 wireless.

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Presentation on theme: "REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE 802.11 standards  The 802 wireless."— Presentation transcript:

1 REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE standards  The 802 wireless family  IEEE The physical layer The MAC layer Quality of service: e MIMO: n Management tools

2 REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE standards  The 802 wireless family  IEEE The physical layer The MAC layer Quality of service: e MIMO: n Management tools

3 REDES INALÁMBRICAS MIC 2009/2010 IEEE 802 Active Working Groups and Study Groups  Higher Layer LAN Protocols Working Group  Link Security Executive Committee Study Group is now part of  Ethernet Working Group  Wireless LAN Working Group  Wireless Personal Area Network (WPAN) Working Group  Broadband Wireless Access Working Group  Resilient Packet Ring Working Group  Radio Regulatory TAG  Coexistence TAG  Mobile Broadband Wireless Access (MBWA) Working Group  Media Independent Handoff Working Group  Wireless Regional Area Networks 3

4 REDES INALÁMBRICAS MIC 2009/2010 Historical notes  The IEEE Working Group for WLAN Standards was created in 1997:   Defines the MAC and 3 different physical layers that work at 1Mbps and 2Mbps:  Infrared (IR) in base band  Frequency hopping spread spectrum (FHSS), band de 2,4 GHz  Direct sequence spread spectrum (DSSS), band de 2,4 GHz  IEEE Std b (September 1999):  Extension of DSSS; Up to 11 Mbps  IEEE Std a (December 1999):  A different physical layer (OFDM): Orthogonal frequency domain multiplexing  Up to 54 Mbps  IEEE Std g (June 2003) ... 4

5 REDES INALÁMBRICAS MIC 2009/2010 Evolution of the IEEE standard  OFFICIAL IEEE WORKING GROUP PROJECT TIMELINES  IN PROCESS - Standards, Amendments, and Recommended Practices   p: Inter car communications  Communication between cars/road side and cars/cars  Planned for relative speeds of min. 200km/h and ranges over 1000m  Usage of GHz band in North America  s: Mesh Networking  Design of a self-configuring Wireless Distribution System (WDS) based on  Support of point-to-point and broadcast communication across several hops  r: Faster Handover between BSS  Secure, fast handover of a station from one AP to another within an ESS  Current mechanisms (even newer standards like i) plus incompatible devices from different vendors are massive problems for the use of, e.g., VoIP in WLANs  Handover should be feasible within 50ms in order to support multimedia applications efficiently 5

6 REDES INALÁMBRICAS MIC 2009/2010 Evolution of the IEEE standard  Other interesting groups  t: Performance evaluation of networks Standardization of performance measurement schemes  v: Network management Extensions of current management functions, channel measurements Definition of a unified interface  w: Securing of network control Classical standards like , but also i protect only data frames, not the control frames. Thus, this standard should extend i in a way that, e.g., no control frames can be forged.  Note: Not all “standards” will end in products, many ideas get stuck at working group  Standards are available here: 6

7 REDES INALÁMBRICAS MIC 2009/2010 IEEE and WiFi  Wi-Fi is a set of standards for wireless networks based on IEEE specifications.  Wi-Fi is a trademark of the Wi-Fi Alliance (formerly the Wireless Ethernet Compatibility Alliance), the trade organization that tests and certifies that equipments meet the IEEE x standards.  The main problem which is intended to solve through normalization is compatibility. This means that the user is assured that all devices having the seal Wi-Fi can work together regardless of the manufacturer of each.  A complete list of devices that have the certification Wi-Fi:  7

8 REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE standards  The 802 wireless family  IEEE The physical layer The MAC layer Quality of service: e MIMO: n Management tools

9 REDES INALÁMBRICAS MIC 2009/2010 Spread Spectrum Transmission 9

10 REDES INALÁMBRICAS MIC 2009/2010 Comparison of Wireless Modulation Schemes  FHSS transmissions less prone to interference from outside signals than DSSS  WLAN systems that use FHSS have potential for higher number of co- location units than DSSS  DSSS has potential for greater transmission speeds over FHSS  Throughput much greater for DSSS than FHSS  Amount of data a channel can send and receive 10

11 REDES INALÁMBRICAS MIC 2009/2010 Orthogonal Frequency Division Multiplexing (OFDM)  With multipath distortion, receiving device must wait until all reflections received before transmitting  Puts ceiling limit on overall speed of WLAN  OFDM: Send multiple signals at same time  High number of low BW ‘modems’ are used, each on a different sub channel  The ‘slow’ sub channels are multiplexed into a ‘fast’ combined channel  Error correction is done with FEC and bit stripping  Avoids problems caused by multipath distortion  Used in a networks 11

12 REDES INALÁMBRICAS MIC 2009/2010 Notion of a channel Wireless communication is carried over a set of frequencies called a channel 12 Signal Power Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

13 REDES INALÁMBRICAS MIC 2009/2010 Channels in Wireless Available spectrum is typically divided into disjoint channels 13 Fixed Block of Radio Frequency Spectrum Channel AChannel BChannel CChannel D Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

14 REDES INALÁMBRICAS MIC 2009/2010 Ideal Spectrum Usage  Use entire range of frequencies spanning a channel  Usage drops down to zero right outside a channel 14 Channel AChannel B Frequency Power Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

15 REDES INALÁMBRICAS MIC 2009/2010 Realistic Spectrum Usage  In reality, this is what communication circuits can achieve  Results in inefficient usage of spectrum 15 Channel AChannel B Real Usage Wastage of spectrum Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

16 REDES INALÁMBRICAS MIC 2009/2010 Realistic Spectrum Usage 16 Channel AChannel B Real Usage Wastage of spectrum Is it possible to eliminate such inefficiencies ? Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

17 REDES INALÁMBRICAS MIC 2009/2010 Define a new channel  Define a new channel as shown  Overlaps with neighboring two channels  Called a `partially overlapped’ channel 17 Channel AChannel B Channel A’ Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

18 REDES INALÁMBRICAS MIC 2009/2010 Define a new channel  Channel A’ would interfere with both A and B  Is it possible to get any gains from using A, A’ and B ? 18 Channel AChannel B Channel A’ Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

19 REDES INALÁMBRICAS MIC 2009/ b Channels 19  In the UK and most of EU: 13 channels, 5MHz apart, – GHz  Each channel is 22MHz  Significant overlap  Best channels are 1, 6 and 11

20 REDES INALÁMBRICAS MIC 2009/2010 An Experiment  Can we use channels 1, 3 and 6 without interference ? 20 Ch 1Ch 6Ch 3 Amount of Interference Link A Ch 1 Link C Ch 6 Link B Ch 3 Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

21 REDES INALÁMBRICAS MIC 2009/2010 An Experiment 21 Link A Ch 1 Link B Ch X 35 meters 60 meters Thanks to: Mishra, Shrivastava, Banerjee, and Arbaugh, The University of Wisconsin, Madison

22 REDES INALÁMBRICAS MIC 2009/2010 IEEE b  Data rate  1, 2, 5.5, 11 Mbit/s, depending on SNR  User data rate max. approx. 6 Mbit/s  Transmission range  300m outdoor, 30m indoor  Max. data rate ~10m indoor  Frequency  Free 2.4 GHz ISM-band  Security  Limited, WEP insecure, SSID  Availability  Many products and vendors  Connection set-up time  Connectionless/always on  Quality of Service  Best effort, no guarantees (unless polling is used, limited support in products)  Manageability  Limited (no automated key distribution, sym. Encryption)  Pros  Many installed systems and vendors  Available worldwide  Free ISM-band  Cons  Heavy interference on ISM-band  No service guarantees  Relatively low data rate 22

23 REDES INALÁMBRICAS MIC 2009/2010 IEEE a  Data rate  6, 9, 12, 18, 24, 36, 48, 54 Mbit/s, depending on SNR  User throughput (1500 byte packets): 5.3 (6), 18 (24), 24 (36), 32 (54)  6, 12, 24 Mbit/s mandatory  Transmission range  100m outdoor, 10m indoor E.g., 54 Mbit/s up to 5 m, 48 up to 12 m, 36 up to 25 m, 24 up to 30m, 18 up to 40 m, 12 up to 60 m  Frequency  Free , , GHz ISM-band  Security  Limited, WEP insecure, SSID  Availability  Some products, some vendors  Connection set-up time  Connectionless/always on  Quality of Service  Best effort, no guarantees (same as all products)  Manageability  Limited (no automated key distribution, sym. Encryption)  Pros  Fits into 802.x standards  Free ISM-band  Available, simple system  Uses less crowded 5 GHz band  Higher data rates  Cons  Shorter range 23

24 REDES INALÁMBRICAS MIC 2009/2010 IEEE g  Ratified in June 2003 by the IEEE Standards Board  standard preliminary draft submitted in December 2001;  Uses the 2.4 GHz band  OFDM and codification PBCC  Backward compatibility IEEE b  They can co-exist in the same WLAN  New transmission speeds: 6, 9, 12, 18, 24, 36, 48 & 54 Mbps 24

25 REDES INALÁMBRICAS MIC 2009/2010 Examples of the physical parameters of a real deviceal  DATA SHEET of a Cisco Aironet a/b/g CardBus Wireless LAN Client Adapter DATA SHEET 25

26 REDES INALÁMBRICAS MIC 2009/2010 WiFi and health RFR's biological effects are measured in terms of specific absorption rate (SAR) -- how much energy is absorbed into human tissue -- which is expressed in Watts per kilogram (W/kg). A dangerous level (by U.S. standards) is considered to be anything above 0.08 W/kg. Thus far, RFR measurements for Wi-Fi, both at home and abroad, are a minute fraction of emissions that could amount to this level. Wi-Fi, in fact, emits less than other common sources of RFR like microwaves and mobile phones. Since mobile phones were recently cleared as a potential carcinogen by a comprehensive, long-term study conducted by the Danish Institute of Cancer Epidemiology in Copenhagen, it seems very unlikely that devices emitting a lower (and less frequent) level could be more dangerous.  By Naomi Graychase, January 12, 2007   More information:  26

27 REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE standards  The 802 wireless family  IEEE The physical layer The MAC layer Quality of service: e MIMO: n Management tools

28 REDES INALÁMBRICAS MIC 2009/2010 Available architectures  Independent Basic Service Set (IBSS)  is the simplest of all IEEE networks in that no network infrastructure is required. As such, an IBSS is simply comprised of one or more Stations which communicate directly with each other.  Do not confuse it with ad hoc!!  infrastructure Basic Service Set (BSS)  Components: Station (STA) Access Point (AP) or Point Coordinator (PC)  Basic Service Set (BSS)  Extended Service Set (ESS) 28

29 REDES INALÁMBRICAS MIC 2009/2010 The MAC basics 29  CSMA/CA with binary exponential backoff  The protocol, at its minimum, consists of two frames: data and ack Point Coordination Function (PCF) Distributed Coordination Function (DCF) MAC Services without contention Services with contention DIFS PIFS SIFS Contention window defer access busy medium slot The 5 timing values: Slot time SIFS: short interframe space (< slot time) PIFS: PCF interframe space (=SIFS+1slot) DIFS: DCF interframe space (=SIFS+2slots) EIFS: extended interframe space The 5 timing values: Slot time SIFS: short interframe space (< slot time) PIFS: PCF interframe space (=SIFS+1slot) DIFS: DCF interframe space (=SIFS+2slots) EIFS: extended interframe space

30 REDES INALÁMBRICAS MIC 2009/2010 DCF example  The backoff intervals are chosen within the contention window. That is in the interval [0, CW]  The CW can vary between 31 slots (CWmin) and 1023 slots (CWmax)  CW increases after a failed transmission and re-initialized after a successful transmission 30 data wait B1 = 5 B2 = 15 data wait B1 = 25 B2 = 20 B1 and B2 are the backoff intervals in STA 1 and 2 CW = 31 B2 = 10

31 REDES INALÁMBRICAS MIC 2009/2010 A couple of problematic configurations 31 Exposed nodeHidden node A B C A B C D

32 REDES INALÁMBRICAS MIC 2009/2010 Hidden nodes situations 32 The obstacle prevents MU1 and MU2 from hearing one another MU3 cannot hear MU1 or MU2 because of the distance

33 REDES INALÁMBRICAS MIC 2009/2010 RTS/CTS mechanism  Based on the network allocation vector (NAV) 33 RTS DIFS+contention CTS SIFS data ACK SIFS DIFS NAV (RTS) NAV (CTS) source destination Other STA defer access Contention window

34 REDES INALÁMBRICAS MIC 2009/2010 PCF: Point Coordination Function The beacons are used to maintain synchronization of the timers in the stations and to send control information The AP generates the beacons at regular intervals The stations know when the next beacon will arrive the target beacon transmission time (TBTT) are announced in the previous beacon 34 Data+Poll DATA+ACK Beacon Data+Poll ACK Station 2 sets NAV(Network Allocation Vector) CF-End PIFSSIFS (no response) PIFS CP PC STA1 Contention Free PeriodCP Data+Poll SIFS STA2 NAV Reset Time STA3 Station 3 is hidden to the PC, it does not set the NAV. It continues to operate in DCF.

35 REDES INALÁMBRICAS MIC 2009/2010 Frames structure 35 management (00) control (01), data (10), reserved (11) Types of addresses: Source address (SA) Destination Address (DA) Transmitter Address (TA) Receiver Address (RA) BSS identifier (BSSID) Types of addresses: Source address (SA) Destination Address (DA) Transmitter Address (TA) Receiver Address (RA) BSS identifier (BSSID) SADATARA11Wireless DS -DASARA = BSSID01To the AP -SABSSIDRA = DA10From the AP -BSSIDSARA = DA00IBSS Addr. 4Addr. 3Addr. 2Addr. 1From DS To DS Función

36 REDES INALÁMBRICAS MIC 2009/2010 Addressing and DS bits 36 SADATARA11Wireless DS -DASARA = BSSID01To the AP -SABSSIDRA = DA10From the AP -BSSIDSARA = DA00IBSS Addr. 4Addr. 3Addr. 2Addr. 1From DSTo DS Función Server DA DS RA (BSSID) SA/TA Client AP Server SA AP TA Client RA DA

37 REDES INALÁMBRICAS MIC 2009/2010 Services 37  The IEEE architecture defines 9 services  Station services:  Authentication  Deauthentication  Privacy  WEP  Data delivery  Distribution services:  Association  generate a connection between a STA and a PC  Disassociation  Reassociation  like association but informing the previous PC  Distribution  integration Similar to plugging in and out in a regular network

38 REDES INALÁMBRICAS MIC 2009/2010 State variables and services 38 State 1: unauthenticated, unassociated State 1: unauthenticated, unassociated State 2: authenticated, unassociated State 2: authenticated, unassociated State 3: authenticated, associated State 3: authenticated, associated Disassociation notification Successful authenticationDeauthentication notification Successful authentication or reassociation Class 1, 2 & 3 frames Class 1 & 2 frames Class 1 frames Deauthentication notification In a IBSS there is no auth. nor ass. Data service is allowed A STA can be authenticated by several AP but associated only with one AP

39 REDES INALÁMBRICAS MIC 2009/2010 BSSID y SSID  BSSID (Basic Service Set Identity)  BSS: MAC address of the AP  Ad-Hoc: 46 bits random number  SSID (Service Set ID)  Known as the Network Name because it is basically the name that identifies the WLAN  Lenght: 0~32 octets 0: it is the broadcast SSID  Used to distinguish WLAN among them  The access points and stations who want to connect to a single WLAN must use the same SSID 39

40 REDES INALÁMBRICAS MIC 2009/2010 The Extended Service Set (ESS) 40 BSS AP WLAN LAN Inter-acces point protocol (IAPP) Distribution System (DS)

41 REDES INALÁMBRICAS MIC 2009/2010 IAPP and the Task Group f  Scope of Project: to develop recommended practices for an Inter-Access Point Protocol (IAPP) which provides the necessary capabilities to achieve multi-vendor Access Point interoperability across a Distribution System supporting IEEE P Wireless LAN Links.  Purpose of Project:... including the concepts of Access Points and Distribution Systems. Implementation of these concepts where purposely not defined by P As based systems have grown in popularity, this limitation has become an impediment to WLAN market growth. This project proposes to specify the necessary information that needs to be exchanged between Access Points to support the P DS functions. The information exchanges required will be specified for, one or more Distribution Systems; in a manner sufficient to enable the implementation of Distribution Systems containing Access Points from different vendors which adhere to the recommended practices  Status  The F Recommendation has been ratified and published in  IEEE F was a Trial Use Recommended Practice. The IEEE 802 Executive Committee approved its withdrawal on February 03,

42 REDES INALÁMBRICAS MIC 2009/2010 Wireless Distribution System  IEEE , WDS means  Multiple wireless “ports” inside the access-point, to wirelessly interconnect cells (access-points connecting to other access-points)  pre-IEEE , did not support WDS:  Three ports exist in one access-point (one Ethernet, and two wireless cells)  One wireless backbone extension can be made (using two radio modules in the access-point)  WDS allows:  Extending the existing infrastructure with wireless backbone links  Totally wireless system without any wired backbones, needed in locations where large areas are to be covered and wiring is not possible 42

43 REDES INALÁMBRICAS MIC 2009/2010 WDS examples 43  Bridging two wired networks  As a repeater to extend a network

44 REDES INALÁMBRICAS MIC 2009/2010 Operational processes Traffic flow - WDS operation 44 STA-1 STA-2 BSS-A BSS-B Packet for STA-2 ACK Packet for STA-2 ACK AP-1000 or AP-500 Avaya Wireless PC-Card Association table Bridge learn table AP-1000 or AP-500 Avaya Wireless PC-Card Association table Bridge learn table STA-1 STA-2 2 STA-1 STA-2 STA-1 2 STA Wireless Backbone WDS Relay WDS Relay Packet for STA-2 ACK

45 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 45

46 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 46

47 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 47

48 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 48

49 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 49

50 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 50

51 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 51

52 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 52

53 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 53

54 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 54

55 REDES INALÁMBRICAS MIC 2009/2010 Linksys Wireless-G Access Point 55

56 REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE standards  The 802 wireless family  IEEE The physical layer The MAC layer Quality of service: e MIMO: n Management tools

57 REDES INALÁMBRICAS MIC 2009/2010 Limitations of the MAC standard for QoS  DCF (Distributed Coordination Function)  Only support best-effort services  No guarantee in bandwidth, packet delay and jitter  Throughput degradation in the heavy load  PCF (Point Coordination Function)  Inefficient and complex central polling scheme  Unpredictable beacon frame delay due to incompatible cooperation between CP and CFP modes  Transmission time of the polled stations is unknown 57

58 REDES INALÁMBRICAS MIC 2009/2010 Overview of e  Task group e formed in Sep and Approved in July 2005  Current version: IEEE P802.11e/D13.0  Backwardly compatible with the DCF and PCF  New QoS mechanism: HCF (Hybrid Coordination Function)  Contention-based channel access EDCA (Enhanced Distributed Channel Access)  was Enhanced Distributed Coordination Function (EDCF)  Controlled channel access (includes polling) HCCA (HCF controlled channel access)  The station that operates as the central coordinator for all other stations within the same QoS supporting BSS (QBSS) is called the hybrid coordinator (HC).  The HC reside inside an AP  A BSS that includes an e-compliant HC is referred to as a QBSS. 58

59 REDES INALÁMBRICAS MIC 2009/2010 EDCA parameters for AC  4 access categories (AC),  AIFS[AC] = SIFS + AIFSN[AC] * aSlotTime, AIFSN[AC]  2. 59

60 REDES INALÁMBRICAS MIC 2009/2010 EDCA and AC Mapping 60

61 REDES INALÁMBRICAS MIC 2009/2010 HCF: Hybrid Coordination Function  During CFP  Poll STAs and give a station the permission to access channel  Starting time and maximum duration of each TXOP are specified by the HC  During CP  Can use the EDCA rules  HC can issue polled TXOPs in the CP by sending CF-Poll after a PIFS idle period  Controlled Contention Allows STAs to request the allocation of polled TXOPs STAs send resource request frames with the requested TC and TXOP duration HC sends an ACK for resource request to the STA 61

62 REDES INALÁMBRICAS MIC 2009/2010 HCF superframes 62

63 REDES INALÁMBRICAS MIC 2009/2010 Performance 63

64 REDES INALÁMBRICAS MIC 2009/2010 QoS: e and WMM™  WMM (Wi-Fi Multimedia)  Prioritized QoS subset of e draft  Widely accepted by e members  Added to Wi-Fi certification in September

65 REDES INALÁMBRICAS MIC 2009/2010 WMM™ for Video 65 Source: Wi-Fi Alliance

66 REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE standards  The 802 wireless family  IEEE The physical layer The MAC layer Quality of service: e MIMO: n Management tools Thanks to: Paul Young / Bernie Rasenberger

67 REDES INALÁMBRICAS MIC 2009/2010 What is “Wireless N”?  n is the long anticipated update to Wi-Fi standards.  Ratified by IEEE in September  “Pre-N” wireless devices were available prior to ratification (Draft N) with speeds of up to 300Mb/s and range of up to 300 metres (300x300).  Increases channel utilisation through MAC aggregation (40MHz) and increased range & throughput through the use of MIMO (Multiple Input/Multiple Output) technology of 2+ antennas.  Will co-exist with b/g networks, but can degrade them because of channel overlap caused by MAC aggregation.  Same performance hit if you mix n clients with b clients, as you get with mixing g & b clients (OFDM). 67

68 REDES INALÁMBRICAS MIC 2009/2010 What is “Wireless N”? n Release DateNovember 2009 Speed300 Mbps Throughput74 Mbps Frequency2.4GHz &/or 5.0GHz Range (outdoor)250 meters 68

69 REDES INALÁMBRICAS MIC 2009/2010 Why is it so fast?  Spatial multiplexing  With spatial multiplexing, the stream of data is split between 2 antennae and reassembled at the receiver. More data goes through in the same amount of time than when using a single antenna. 69

70 REDES INALÁMBRICAS MIC 2009/2010 Why is it so fast?  Support for 40Mhz Channels  So far each b/g channel only used 20MHz of the spectrum. With more spectrum available, more data can go through. 70

71 REDES INALÁMBRICAS MIC 2009/2010 Wireless N is also more reliable  Through the use of Multipath we can achieve a more robust signal  Antennas cleverly combine the same signal which has travelled through different paths. Even if the environment changes and some of the signal is obstructed, enough can still go through.  This is how Wireless N achieves A ROBUST SIGNAL, less prone to interference and environmental changes. 71 Transmitter Receiver Multiple copies of signal received Adjusted and combined signals Resulting signal

72 REDES INALÁMBRICAS MIC 2009/2010 Deployment Considerations  n can operate on 2.4 GHz or/and 5 GHz and is backward compatible with a/b/g. Access Points can be set to support 11n only.  AP’s can be:  single radio (2.4GHz only or 5GHz only)  switchable dual radio (switchable between 2.4GHz and 5GHz)  concurrent dual radio (operates 2.4GHz and 5GHz at the same time) 72

73 REDES INALÁMBRICAS MIC 2009/2010 Deployment Considerations  When introducing n into existing a/b/g WLANs both bands (2.4GHZ and 5GHz) can have n enabled.  In case of dense AP architecture channel bonding for 2.4GHz should be disabled (set to 20MHz).  Or if there are other 2.4GHz networks in the area – disable channel bonding for 2.4GHz.  n can be offered to throughput-critical clients only which support 11n: 5GHz band can be set as “11n only”. Leaving 2.4GHz for the rest of the clients which will not interfere with the critical data (802.11b/g/n). 73 dual-radio n AP 2.4GHz b/g/n 5GHz n only High Speed Wi-Fi n client Legacy mixed Wi-Fi

74 REDES INALÁMBRICAS MIC 2009/2010 The ‘Sting’  Increased channel spectrum from 22Mhz to 40Mhz, using MAC aggregation techniques;  Consumes 2 of 3 non overlapping 2.4Ghz channels;  Not an issue in “pure N” networks, but will cause issues in hybrid networks;  Uses OFDM, so if b clients on network performance degrades for all users. 74

75 REDES INALÁMBRICAS Máster de Ingeniería de Computadores-DISCA Redes Inalámbricas – Tema 2.C Wireless LANs: the IEEE standards  The 802 wireless family  IEEE The physical layer The MAC layer Quality of service: e MIMO: n Management tools

76 REDES INALÁMBRICAS MIC 2009/2010 Wireshark / Ethereal  Wireshark is the world's foremost network protocol analyzer, and is the de facto (and often de jure) standard across many industries and educational institutions.  Wireshark development thrives thanks to the contributions of networking experts across the globe. It is the continuation of a project that started in

77 REDES INALÁMBRICAS MIC 2009/2010 Wireshark Features  Deep inspection of hundreds of protocols, with more being added all the time  Live capture and offline analysis  Standard three-pane packet browser  Multi-platform: Runs on Windows, Linux, OS X, Solaris, FreeBSD, NetBSD, and many others  Captured network data can be browsed via a GUI, or via the TTY-mode TShark utility  Rich VoIP analysis  Read/write many different capture file formats:  Capture files compressed with gzip can be decompressed on the fly  Live data can be read from Ethernet, IEEE , PPP/HDLC, ATM, Bluetooth, USB, Token Ring, Frame Relay, FDDI, and others  Decryption support for many protocols, including IPsec, ISAKMP, Kerberos, SNMPv3, SSL/TLS, WEP, and WPA/WPA2  Output can be exported to XML, PostScript®, CSV, or plain text 77

78 REDES INALÁMBRICAS MIC 2009/2010 Wireshark / Ethereal 78

79 REDES INALÁMBRICAS MIC 2009/2010 Kismet  Kismet is an layer2 wireless network detector, sniffer, and intrusion detection system. Kismet will work with any wireless card which supports raw monitoring (rfmon) mode, and can sniff b, a, and g traffic.  Kismet identifies networks by passively collecting packets and detecting standard named networks, detecting (and given time, decloaking) hidden networks, and infering the presence of nonbeaconing networks via data traffic.  Some of the features  Ethereal/Tcpdump compatible data logging  Built-in channel hopping and multicard split channel hopping  Hidden network SSID decloaking  Graphical mapping of networks  Manufacturer and model identification of access points and clients  Detection of known default access point configurations  Runtime decoding of WEP packets for known networks  Over 20 supported card types 79

80 REDES INALÁMBRICAS MIC 2009/2010 gKismet 80

81 REDES INALÁMBRICAS MIC 2009/2010 Network Stumbler  Allows to save and export data in several different formats  Supports GPS and the ability to store GPS information in conjunction with other data 81

82 REDES INALÁMBRICAS MIC 2009/2010  The graphical interface used is very intuitive and allows various types of analysis in a simple and direct form 82 Network Stumbler

83 REDES INALÁMBRICAS MIC 2009/ Network Stumbler


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