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Transcript
Wireless Networks: Personal, Local, Metropolitan Speedups, Security, Power John Schafer University of Michigan Ann Arbor CSG 10 May 2000 [email protected] www.itcom.itd.umich.edu/wireless/ Overview • • • • • • Current choices Speedups coming Power over Ethernet Authenticated Wireless Wireless Personal Area Network: Bluetooth Point-to-point Wireless Metropolitan Area Networking Terminology • Access point (AP), station adapter • WEP (Wired Equivalent Privacy) – Encryption of data packets, 40 or 128 bit • Access control table - list of MAC addresses • Speeds are nominal, throughput is about one half Standard Speed Power* Range (Mbps) (mA) (feet) 1.6 5/300 150 Current Choices OpenAir (Proxim) HomeRF Cost $250 1.6 5/300 150 $150 IEEE 802.11 Frequency Hopping 2 10/300 150 $150 IEEE 802.11b Direct Sequence 11 10/300 150 $100 Bluetooth (802.15) 1 .03/30 30 $30 *sleep/transmit Speedups Coming High Speed WLANs Band, GHz Channels Data Rates, Mbps Modulation Standard ratified Products available IEEE IEEE HIPERLAN HIPERLAN 802.11b 802.11a Type 1 Type 2 2.4 5 5 5 3 5 7 1, 2, 6, 9, 12, 6, 12, 24 20-54 5.5, 11 18, 24,54 CCK OFDM GMSK OFDM 4Q99 Due 4Q00 Sep-96 Due 4Q99 4Q99 2001 4Q00 2002 Speedups of questionable value • HiperLAN1 – Only one vendor with plans, wait for HiperLAN2 or 802.11a • 22 Mbps 802.11b – First meeting May 8-12, 2000 – Skip it and wait for 802.11a, 54 Mbps • 10 Mbps Frequency Hopper (IEEE 802.11) – Needs FCC rule change, seems unlikely Power over Ethernet • Conduit to power AP: $800, Enet: $300 • Several methods being discussed (IEEE) – Use spare wire pairs on CAT5 cable – Couple DC power on signal pairs • • • • Smart - only turn on power to responsive device Applications - VoIP phones, Security, AP’s Built into future switches/hubs Standard due 3Q2001 Problems with current security • • • • Encryption keys set the same for all users Password for network given to all users Access control table updated manually Access control based on MAC address - spoofable Authenticated Wireless • Radius client in access point • IEEE 802.1x is working on a standard • Lucent first to market ahead of standard Lucent Access Server AS-1000 • Diffie-Hellman key exchange – Per user, per session key used for WEP encryption • Setup PPP link • RADIUS client in AP - RADIUS servers Kerberos • Limitations: – First version - No Roaming – User must exist in authentication system before first connection Merit RADIUS system, ABS, PTS • State-wide: 800 modem pools, 160 RADIUS servers • Accounting and Billing System (ABS) • Protection Server (PTS) • AS-1000 looks like a modem pool • Auto-subscribe, monthly billing, usage charges, grant access based on PTS groups Adapting IEEE 802.1x to 802.11 • Based on existing standards – Extensible Authentication Protocol (EAP) – RADIUS • Dynamic key management • Roaming - handoff of keys to AP • Unauthenticated VLAN support - access to registration/enrollment server (optional) • Expected Summer 2001 • http://grouper.ieee.org/groups/802/1/index.html Bluetooth • • • • Wireless Personal Area Network (PAN) IEEE 802.15 Asynch data and up to 3 voice channels Data: asymmetric 721 Kbps/57 Kbps, symmetric 432.6 Kbps • Uses same 2.4 GHz band as 802.11 • Fast Frequency Hopper, 1600 hops/sec. • Interferes with 802.11 WLANs Ericsson Bluetooth Module Bluetooth - Applications • • • • • • • Replace infrared and custom cables Computers, PDAs, Palmtops, Mobile phones Headsets, Digital cameras, Automobiles Bluetooth SIG has 1400 member companies Plan to migrate your WLANs to 5 GHz band http://www.bluetooth.com/ http://www.bluetooth.net/ Wireless Metropolitan Area Nets • Point-to-point and point-to-multipoint • Unlicensed (2.4 GHz ISM band) – WLAN hardware plus external antennas – Speed: 1-5 Mbps, Distance: <20 miles • Licensed spectrum – Local Multi-point Distribution Service (LMDS) • FCC auction in spring of 1998, 38 GHz band • Line-of-site, up to 5 miles, up to 45 Mbps • Laser