Wireless networking Roger Treweek Oxford University Computing Services.
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Transcript of Wireless networking Roger Treweek Oxford University Computing Services.
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Wireless networking
Roger TreweekOxford University Computing Services
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Why Wireless?
• Being sold as– Any time, any place, any how– Even on a mountain side?
• However– You do need an access point nearby– And, potentially, lots of them
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Why Wireless?
• There are some obvious locations– Lecture rooms– Libraries– Hard-to-wire areas
• Or for specific reasons– Conferences– Meetings– Mobility
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Wireless Problems
• Security – out of the box product is insecure
• Privacy – snooping – passwords, data
• ‘Hub’ style operation – anyone can see all traffic
• Hacker tools readily available
• Performance
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Wireless Technology
• 802.11b- 2.4Ghz, 11 Mbps
• 802.11g- 2.4 Ghz, 54 Mbps
• 802.11a- 5 Ghz, 54 Mbps
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802.11b
• Wi-Fi standard
• Most common
• 2.4 Ghz spectrum is crowded
• 3 non-overlapping channels
• Limited users per access-point
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802.11g
• Uses same 2.4Ghz spectrum as 802.11b
• 3 non-overlapping channels
• 802.11b card usage reduces throughput
• Same coverage
• More users per access-point
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802.11a
• Uncrowded spectrum – for now!
• 8 non-overlapping channels
• Reduced coverage area
• More users per access-point
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Data Rates
Data rate
(Mbps)
Throughput
(Mbps)
Throughput
(%802.11b)
802.11b 11 6 100%
802.11g
(+ 802.11b)
54 7 117%
802.11g 54 22 367%
802.11a 54 25 417%
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Ranges
Data rate 802.11a 802.11g 802.11b
54 45ft - 13m 90ft - 27m
36 65ft- 19m 100ft - 30m
18 110ft - 33m 180ft-54m
12 130ft - 39m 210ft-64m
11 160ft-48m 160ft-48m
6 165ft- 50m 300ft - 91m
2 270ft-82m 270ft-82m
1 410ft-124m 410ft-124m
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Site Survey
• Site survey is recommended• Use same make/model as it is intended
to employ• Consider main coverage areas• Number of access-points & location• Interference issues
– Channel allocation– Power settings
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Security
• Wireless access is insecure
• It is ‘in the air’
• No respecter of boundaries
• Hacker tools freely available
• Clear text transmission
• Anyone can use
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Security
Three areas to consider
• Authorized users only
• Encrypted transmissions
• Accountability of usage
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Authorized Users
• Username/password required– 802.1x
• IEEE standard• Uses EAP to provide variety of authentication methods
eg RADIUS
– WPA• Wi-Fi Protected Access• May be a container to 802.1x• Changes due this summer
– 802.11i• Due to address further issues
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Authorized Users
• MAC address– Scaling / management issues
• Gateway– VPN– Captive portal
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Secure Transmission
• WEP – Wired Equivalent Privacy
• WPA uses rotating keys
• VPN
• Secure protocols only – ssh, ssl etc
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Accountability
• Important to be able to track usage– Harder to trace than for wired connections– Identification of compromised machines– Cease-and-desist notices– ‘Illegal’ or harmful activity
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Connection Options
• Three main options used– VPN– 802.11x, WPA– Gateway
• Use may be determined by type of user
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VPN
• Users connect to private network
• Only allowed access to VPN server
• User authorisation by server
• Encrypted connection
• Logging by server
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802.1x, WPA
• 802.1x– User authorisation before any access– Choice of authorisation method– No encryption
• WPA– Uses 802.1x– Key changes for encryption– Changes due
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Gateway
• Usually web page for authorisation
• Bluesocket– Commercial but popular in uk academia– Lots of features
• NoCat– open source
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Types of Users
• Staff
• Students
• Visitors– Meetings– Conferences
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Staff
• Members of the University, long term use
• VPN possible
• WPA possible
• MAC & WEP– If small group– Secure protocols used
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Students
• Like staff, university members, long term
• VPN
• WPA
• Gateway?
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Visitors
• Hardest group to handle!– One day only– Conference attendees– Limited periods eg week, month etc– Not university members– May be at short notice
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Visitors
• Cannot use VPN– May need VPN to access home site
• Gateway is most common method– Especially if very short term– Pre-created accounts
• 802.1x, WPA– For longer term visitors?
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Rules and Recommendations
• OUCS have published current thinking• Approved by ICTC• Typically used at other sites
• Rules / Requirements• Recommendations / Guidance
• http://www.oucs.ox.ac.uk/network/wireless
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Rules
• Only authorised networks allowed
• Must be registered with OUCS
• Must be separate from any other network
• User authorisation required
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Rules
• Strong data encryption must be used
• Clients must not offer services that compromise security
• All associations must be recorded
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Recommendations
• 802.11b standard supported
• Wi-Fi approved equipment should be used
• Only IP should be used
• Use minimum necessary power levels
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Recommendations
• Pick your channel allocations
• High bandwidth applications should not be used
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OUCS Pilot
• Early days
• Testing various options
• Aim to produce standards
• Central vs Unit based schemes
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Conclusions
• Not a substitute for wired connections
• Security is paramount
• Changing marketplace
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Any Questions?