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1 Wireless LAN CO72047 Unit 2: Wireless Fundamentals Prof. Bill Buchanan Contact: Room: C.63 Telephone: X2759 MSN Messenger: WWW:

2 Module Descriptor

3 Week Date Academic Cisco Lab/Tutorial 1 1 Oct 1: Radio Wave Fundamentals 2 8 Oct 2: Wireless Fundamentals Intro to Wireless LANs Lab 1/2: Access Point Tutorial 1 (T) 3 15 Oct 3: Ad-hoc and Infrastructure Networks IEEE and NICs Lab 3: Ad-hoc Networks 4 22 Oct 4: Encryption Wireless Radio Technology Lab 4: Infrastructure Networks 5 29 Oct 5: Authentication Wireless Topologies Lab 5: Remote Connections 6 5 Nov 6: Antennas Access Points Lab 6: Encryption/Authen 7 12 Nov 7: Filtering/8. VLANs Bridges Lab 7: Filter 8 19 Nov Napier Test (40%) Antennas Lab 8: VLAN 9 26 Nov Security Lab 9: VLAN/802.1Q 10 3 Dec Cisco Academy/Additional Material Applications Lab 10: IP Routing Dec Cisco Academy /Additional Material Site Survey Lab 11: RADIUS Dec Cisco Academy /Additional Material Troubleshooting Lab 12: SNMP Holidays 13 7 Jan Revision/Cram (Cisco Exam) Emerging Technologies Coursework/Practical (50%) Jan Revision/Cram (Cisco Exam) Cisco Exam (10%) Jan

5 Wireless connections which technology? Areas covered: Basic radio parameters. This area covers the main type of wireless communications. IEEE b issues. This area covers some of the fundamentals of radio waves.

6 Wireless Access point Wireless Client Wireless Bridge

8 Broadcast span Defined by broadcast domain

9 IEEE b networks

10 IEEE Wireless IEEE a a deals with communications available in the 5GHz frequency, and has a maximum data rate of 54 Mbps. IEEE b b, or Wi-Fi, is the standard that is most commonly used in wireless LAN communications. It has a maximum bandwidth of 11Mbps, at a frequency of 2.4GHz. IEEE g g is a proposed standard that hopes to provide 54Mbps maximum bandwidth over a 2.4GHz connection, the same frequency as the popular b standard. IEEE c c is a group set up to deal with bridging operations when developing access points. IEEE f f is concerned with standardising access point roaming which is involved in making sure that interoperability between access points is guaranteed

11 IEEE b Operating Channels: 11 for N. America, 14 Japan, 13 Europe (ETSI), 2 Spain, 4 France Operating Frequency: GHz (North America), GHz (Japan), GHz (Europe ETSI), GHz (Spain), GHz (France) Data Rate: 1, 2, 5.5 or 11Mbps Media Access Protocol: CSMA/CA, Compliant Range: 11Mbps: 140m (460 feet) 5.5Mbps: 200m (656 feet) 2Mbps: 270m (885 feet) 1Mbps: 400m (1311 feet) RF Technology: Direct Sequence Spread Spectrum Modulation: CCK (11Mps, 5.5Mbps), DQPSK (2Mbps), DBPSK (1Mbps)

12 Maximum bandwidth (IEEE b) Available bandwidth CCK 11Mbps CCK Max bandwidth 5.5Mbps CCK - Complementary Code Keying DQPSK - differential quadrature phase shift keying BPSK - biphase shift keying DQPSK 2Mbps DBPSK 1Mbps 100m 200m 300m Distance 400m

13 Maximum bandwidth (IEEE b) 11Mbps Max bandwidth 5.5Mbps Actual maximum bandwidth 2Mbps 1Mbps 100m 200m 300m 400m

14 Maximum bandwidth (IEEE b) 8Mbps Available throughput Too many errors causes the TCP window to close, and reduce throughput. 6Mbps 2Mbps Linear increase in actual throughput against required throughput More collisions and errors are occurring, thus data frames are being deleted, causing wasted bandwidth. 2Mbps 4Mbps Required data throughput 8Mbps 10Mbps

15 IEEE g networks

16 Maximum bandwidth (IEEE g) 64-QAM 54Mbps QAM Quadrature Amplitude Modulation CCK - Complementary Code Keying DQPSK - differential quadrature phase shift keying BPSK - biphase shift keying Available bandwidth 100m 16-QAM 200m 24Mbps QPSK 300m Distance g Mbps Modulation 6 BPSK 9 BPSK 12 QPSK 1Mbps 18 QPSK 2Mbps DBPSK QAM m 16-QAM QAM QAM

17 Netperf on a 11g link

18 Windows IP Configuration Ethernet adapter Wireless Network Connection 3: Connection-specific DNS Suffix. : IP Address : Subnet Mask : Default Gateway : C:\>netperf -H p 1001 TCP STREAM TEST to Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec C:\>netperf -H p 1001 TCP STREAM TEST to Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec c:\>netperf -H p 1001 TCP STREAM TEST to Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec

19 IEEE g example

20 IEEE g example

21 IEEE n

22 802.11n n Frequency: Max: Range: 2.4 GHz or 5 GHz 540 Mbit/s Same as 11b MIMO (Multiple-in, multiple-out) Sends information on two or more antennas. These signals then reflect off objects, creating multiple paths creating multiple paths. Normally these cause interference and fading, but with MIMO they carry different information, which are recombined on the receiving side.

23 802.11n

24 MIMO

25 IEEE networks

26 CSMA/CA and PCF IEEE can use two mechanisms for shared access: CSMA/CA. CSMA/CA is, like standard Ethernet (IEEE 802.3) a contention-based protocol, but uses collision avoidance rather than collision detection. It would be impossible to use collision detection as a radio wave is always either sending or receiving and can never do both at the same time. The nodes will thus not be able to listen on the channel while they are transmitting. Point Coordination Function (PCF). This is an optional priority-based protocol, which provides contention-free frame transfer for transmission of time-critical data, such as realtime video or audio. With this, the point coordinator (PC) operates in the wireless access point and identifies the devices which are allowed to transmit at any given time. Each PC then, with the contention-free (CF) period, the PC polls each of the enabled PCF to determine if they wish to transmit data frames. No other device is allowed to transmit while a another node is being polled. Thus, PCF will be contention-free and enables devices to transmit data frames synchronously, with defined time delays between data frame transmissions.

27 CSMA/CD Listen for no activity 1 ACK ACK time-out 2 2 Node has gone. Data frame has collided with another Data frame corrupted with noise.

28 IEEE data frame Frame control Duration/ ID Address 1 Address 2 Address 3 Sequence control Address 4 Frame body FCS 2 Bytes Frame control. This contains control information. Duration/ID. This contains information on how long the data frame will last. Address fields. This contains different types of address, such as an individual address of group addresses. The two main types of group addresses are broadcast and multicast. Sequence control. This identifies the sequence number of the data frames, and allows the recipient to check for missing or duplicate data frames. Frame body. This part contains the actual data. The maximum amount is 2312 bytes, but most implementations use up to 1500 bytes. FCS (Frame Check Sequence). This is a strong error detection code.

29 Frame control Duration/ ID Address 1 Address 2 Address 3 Sequence control Address 4 Frame body FCS 2 Bytes

30 IEEE networks

31 dot11radio0 (or d0) con bvi 1 port is used to configure both ports with the same address e0 (or fa0) # config t (config)# int int bvi1 bvi1 (config-if)# ip ip address (config-if)# exit exit Antenna connector

32 Fixed network Root # config t (config)# int int dot11radio0 (config-if)# station role role root root (config-if)# station role role repeater (config-if)# end end Repeater

33 Fixed network Root # config t (config)# ip ip? (config)# ip ip default-gateway? (config)# ip ip default-gateway (config)# exit exit Repeater

34 Channel Frequency Channel. If If an an ad-hoc network is is used, then then the the nodes which communicate must use use the the same channel channel channel channel channel channel channel channel channel channel channel channel channel channel channel

35 Channel Frequency Channel. If If an an ad-hoc network is is used, then then the the nodes which communicate must use use the the same channel channel channel channel channel channel channel channel channel channel channel channel channel channel channel (config)# int int dot11radio0 (config-if)# channel 7 (config-if)# no no shutdown (config)# int int fa0 fa0 (config-if)# no no shutdown

36 Fragmentation threshold Fragmentation threshold. This This can can be be used to to split split large data data frames into into smaller fragments. The The value can can range from from to to 1500 bytes. This This is is used to to improve the the efficiency when there is is a high high amount of of traffic on on the the wireless network, as as smaller frames make more efficient usage of of the the network. Data packets are split into 1500 byte data frames (MTU) The large data frames may allow nodes to hog the airwave

37 Fragmentation threshold Fragmentation threshold. This This can can be be used to to split split large data data frames into into smaller fragments. The The value can can range from from to to 1500 bytes. This This is is used to to improve the the efficiency when there is is a high high amount of of traffic on on the the wireless network, as as smaller frames make more efficient usage of of the the network. Data frames are fragmented into smaller frames Possibly allows for a smoother and fairer transmission.

38 Network settings Fragmentation threshold. This This can can be be used to to split split large data data frames into into smaller fragments. The The value can can range from from to to 1500 bytes. This This is is used to to improve the the efficiency when there is is a high high amount of of traffic on on the the wireless network, as as smaller frames make more efficient usage of of the the network. Data frames are fragmented into smaller frames # config t (config)# int int dot11radio0 (config-if)# fragment-threshold? < > (config-if)# fragment-threshold (config-if)# end end Possibly allows for a smoother and fairer transmission.

39 Infrastructure or ad-hoc Network type. This can either be set to an infrastructure network (which use access points, or wireless hubs) or Ad-hoc, which allows nodes to interconnect without the need for an access point. Ad-hoc Infrastructure

40 Infrastructure or ad-hoc Infrastructure SSID defines the connected nodes SSID defines the connected nodes Ad-hoc

41 Infrastructure or ad-hoc Infrastructure SSID defines the connected nodes SSID defines the connected nodes # config t (config)# int int dot11radio0 (config-if)# ssid ssid fred fred (config-if-ssid)# guest-mode? (config-if-ssid)# guest-mode (config-if-ssid)# end end Ad-hoc

42 Span of network L L L

43 Network settings Authentication algorithm. This sets whether the adapter to use an open system (where other nodes can listen to the communications), or uses encryption (using either a WEP key, or a shared key). # config config t (config-if)# (config-if)# ssid ssid fred fred (config-if-ssid)#? (config-if-ssid)# authentication authentication? client client LEAP LEAP client client information information key-management key-management key key management management network-eap network-eap leap leap method method open open open open method method shared shared shared shared method method (config-if)# (config-if)# exit exit (config)# (config)# exit exit (config-if-ssid)# authentication authentication open open (config-if-ssid)# exit exit (config-if)# (config-if)# exit exit (config)# (config)# exit exit Authentication is a key issue, and will be covered later in the module. At present the authentication is open, so that any user and device can connect without authenticating itself.

44 Other Factors

45 Network settings Preamble mode. This This can can either be be set set to to Long (which is is the the default) or or short. A long long preamble allows for for interoperatively with with 1Mbps and and 2Mbps DSSS specifications. The The shorter allows for for faster operations (as (as the the preamble is is kept kept to to a minimum) and and can can be be used where the the transmission parameters must be be maximized, and and that that there are are no no interoperatablity problems. Preamble this is sent before the start of the data transmission so that nodes can detect that it is about to transmit.

46 Network settings Preamble mode. This This can can either be be set set to to Long (which is is the the default) or or short. A long long preamble allows for for interoperatively with with 1Mbps and and 2Mbps DSSS specifications. The The shorter allows for for faster operations (as (as the the preamble is is kept kept to to a minimum) and and can can be be used where the the transmission parameters must be be maximized, and and that that there are are no no interoperatablity problems. # config t (config)# int int dot11radio0 (config-if)# preamble-short (config-if)# end end Preamble this is sent before the start of the data transmission so that nodes can detect that it is about to transmit.

47 Hidden node problem These nodes cannot hear each other. The hidden node problem occurs when two nodes transmit to an access point, but they are not in communication range, thus their signals can collide, and cause errors.

48 Network settings (cont.) RTS/CTS threshold. The RTS Threshold prevents the Hidden Node problem, where two wireless nodes are within range of the same access point, but are not within range of each other. As they do not know that they both exist on the network, they may try to communicate with the access point at the same time. When they do, their data frames may collide when arriving simultaneously at the Access Point, which causes a loss of data frames from the nodes. The RTS threshold tries to overcome this by enabling the handshaking signals of Ready To Send (RTS) and Clear To Send (CTS). When a node wishes to communicate with the access point it sends a RTS signal to the access point. Once the access point defines that it can then communicate, the access point sends a CTS message. The node can then send its data.

49 Hidden node problem RTS (Ready To Send) RTS (Ready To Send) CTS (Clear To Send) Data transmitted

50 RTS RTS CTS CTS Data Data

51 Hidden node problem RTS RTS threshold RTS RTS threshold determines the the data data frame frame size size that that is is required, in in order order for for it it send send an an RTS RTS to to the the WAP. WAP. The The default default value value is is RTS (Ready To # Send) config t (config)# int int dot11radio0 (config-if)# rts rts? (config-if)# rts rts threshold (config-if)# end end CTS (Clear To Send) RTS (Ready To Send) Data transmitted

52 Hidden node problem RTS RTS retries retries RTS RTS Retries Retries defines defines the the number of of times times that that an an access access point point will will transmit an an RTS RTS before before it it stops stops sending the the data data frame. frame. Values Values range range from from1 to to RTS (Ready To RTS (Ready To # config t Send) Send) (config)# int int dot11radio0 (config-if)# rts rts? (config-if)# rts rts retries (config-if)# end end CTS (Clear To Send) Data transmitted

53 Power management The higher the transmitting power, the wider the coverage. The The power power of of the the access access point point and and also also of of the the client client are are important as as they they will will define define the the coverage of of the the signal, signal, and and must must also also be be within within the the required safety safety limits. limits.

54 Power management # config t (config)# int int dot11radio0 (config-if)# power power? (config-if)# power power local local? (config-if)# power power local local 30 The higher 30 the (config-if)# power power client 10 transmitting 10 power, (config-if)# speed speed? the wider the coverage. (config-if)# speed speed (config-if)# exit exit (config)# exit exit The The power power of of the the access access point point and and also also of of the the client client are are important as as they they will will define define the the coverage of of the the signal, signal, and and must must also also be be within within the the required safety safety limits. limits. [1.0] [11.0] [2.0] [5.5] [basic-1.0] [basic-11.0] [basic-2.0] [basic-5.5] range throughput

Power management Power Power saving saving modes: modes: CAM CAM (Constant awake awake mode). mode). Used Used when when power power usage usage is is not not a problem.

55 Power management Power Power saving saving modes: modes: CAM CAM (Constant awake awake mode). mode). Used Used when when power power usage usage is is not not a problem. PSP PSP (Power (Power save save mode). mode). Power Power is is conserved as as much much as as possible. The The card card will will typically go go to to sleep, sleep, and and will will only only be be awoken by by the the access access point, point, or or if if there there is is activity. activity. FastPSP (Fast (Fast power power save save mode). mode). This This uses uses both both CAM CAM and and PSP, PSP, and and is is a compromise between the the two. two.

56 Maximum bandwidth (IEEE b) CCK 11Mbps Max bandwidth (config)# int int dot11radio0 (config-if)# speed speed? 5.5Mbps (config-if)# speed speed (config-if)# exit exit (config)# exit exit DQPSK 2Mbps DBPSK 1Mbps 100m 200m 300m 400m

57 Maximum associations A particular problem in in wireless networks is is that that the the access access point point may may become overburdened with with connected clients this this could could be be due due to to an an attack, attack, such such as as DoS DoS (Denial (Denial of of Service), or or due due to to poor poor planning.

58 Maximum associations For For example: Max Max bandwidth = 25Mbps Av Avrate = 0.5Mbps Max. Max. associations = 50 50

59 Maximum associations # config t (config)# int int dot11radio0 (config-if)# ssid ssid fred fred (config-if-ssid)# max max? <1-255> association limit limit (config-if-ssid)# max max (config)# exit exit # show show dot11 dot11? # A particular problem in in wireless networks show show dot11 dot11 association # that that the the access access point point may may become show show dot11 dot11 statistics client-traffic overburdened with with connected clients... # show show dot11 dot11 adjacent-ap this this could could be be due due to to an an attack, attack, such such as as DoS DoS (Denial (Denial of of Service), or or due due to to poor poor planning.

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