Transcript Wireless Networks

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
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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
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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
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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
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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
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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