Date post: | 18-Dec-2015 |
Category: |
Documents |
Upload: | justin-mckinney |
View: | 213 times |
Download: | 0 times |
But how do people use it?How to design Wi-Fi networks?How to deploy Wi-Fi networks?
Wi-Fi is becoming pervasive
• Complete Wi-Fi coverage• 200 acre campus• 161 buildings
– 82 Residential
– 32 Academic
– 22 Administrative
– 6 Library
– 19 Social
Dartmouth campus
The largest Wi-Fi study
• Fall 2001• Wi-Fi at Dartmouth• 11 weeks• Over 1700 users• Diverse population• 161 buildings• 476 access points• Campus-wide coverage
[Hutchins and Zegura]• Wi-Fi at GA Tech• 20 or 7 weeks• 444 users• Diverse population• 18 buildings• 109 access points• Partial coverage
[Balachandran 2002]• Wi-Fi at SIGCOMM• 2.5 days• 195 users• Computer scientists• One room• 4 access points• Small sample
[Tang and Baker 2000]• Wi-Fi at Stanford• 12 weeks• 74 users• Computer scientists• 1 building• 12 access points• Small sample
1: Syslog data collection
• AP reports interesting events– Authenticate– Associate– Deauthenticate– Disassociate
• Record date, time, MAC, AP name
• Sent by access point to syslog recorder
2: SNMP data collection
• Every 5 minutes, poll each AP
• Record:– MAC of associated clients– Counter: inbound bytes– Counter: outbound bytes
Inbound
Outbound
Max: 19,902Median: 2
Roams per sessionRoams per sessionPlot of the 18% of sessions that involve at least one roam
Maximum: 77 days, 64 buildings, 161 APsMedian: 28 days, 5 buildings, 9 APs
Activity per card (distribution)Activity per card (distribution)
Common IP protocolsCommon IP protocols
Protocol GB Percent
PIM ~ 0 0.0%
NARP ~ 0 0.0%
RSVP ~ 0 0.0%
IGMP ~ 0 0.0%
ICMP ~ 0 0.0%
UDP 5.7 2.5%
TCP 221.9 97.5%
Total 227.595 100.0%
99.7% of all wireless frames contained IP packets
TCP and UDP traffic (GB)TCP and UDP traffic (GB)(by building)(by building)
These top ten account for 85% of traffic
Correction: Figures 27-28Correction: Figures 27-28
Dartmouth College Computer Science
Technical Report TR2002-432
http://www.cs.dartmouth.edu/~campus/
Summary
• Largest trace-based study of a WLAN
• Large, diverse population– Residential university campus– Mixture of academic and residential patterns– Results may be different for other populations
ConclusionsConclusions
• High variance in traffic and activity– From day to day, hour to hour– From place to place, user to user
• No clear dominance of inbound or outbound – Varies by protocol and user
• Dormitories dominated traffic– Especially the Tuck School of Business
• We need:– Cards that avoid roaming across subnet boundary– Support for roaming across subnets (Mobile IP, etc)– Symmetric bandwidth– Full-campus coverage: critical to acceptance