SCinet2000 The Networks at the SC2000 Conference Dallas, Texas 610 November 2000 Wireless Network Sl

1
SCinet2000The Networks at the SC2000
ConferenceDallas, Texas 6-10 November
2000Wireless Network Slides

• 29 November 2000
• David Koester, Ph.D.
• dkoester_at_mitre.org

2
Outline

• The Networks of SC2000
• SCinet2000
• XNet
• commodity network
• wireless network
• Photos
• The SC2000 Networking Challenge
• Network monitoring
• tools
• statistics
• Details on wireless
• SCinet2001

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Commodity Network
4
Wireless Network OverviewUpper Level
5
Wireless Frequency AssignmentsUpper Level
6
Wireless Frequency AssignmentsGround Floor
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Network Access Point (NAP) Ceiling Mount
8
Outline

• The Networks of SC2000
• SCinet2000
• XNet
• commodity network
• wireless network
• Photos
• The SC2000 Networking Challenge
• Network monitoring
• tools
• statistics
• Details on wireless
• SCinet2001

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Wireless Networking Details Hardware and
Configuration

• Network hardware
• A total of 38 network access points (NAPs)
• As many as 360 simultaneous wireless clients
• Configured NAPs via DHCP
• Installation process
• modify DHCP scripts
• install on the network while watching boot over
  console port
• check parameters via web server in NAP
• Modify setup
• manually using web server interface
• using a script and http push

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Wireless Networking DetailsNetwork Performance

• 100 coverage in required areas
• Able to communicate on the move and reassociate
  to other NAPs automatically
• Supported 220 Kbps RealVideo download stream when
  stationary
• Could not support similar RealVideo uploads
• Supported only 34 Kbps RealVideo download stream
  when moving
• Load balancing during associations appeared
  problematic
• Limited WAN TCP/IP throughput performance over
  wireless
• as great as 3 Mbps throughput to ORNL over wired
  meanwhile less than 100 Kbps throughput to ORNL
  over wireless
• problems caused by additional errors encountered
  over shared media same route could not
  maintain large widow

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Wireless Networking DetailsFrequency Assignment

• Want to optimize spatial separation
• Use a Greedy Algorithm with Rollback
• Examine closest three
• Results are not always ideal
• Be sure NAPs are setup correctly!

START
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Wireless Networking PerformanceTotal NIC
Associations
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Wireless Networking PerformanceNIC Associations
at the Education Meeting
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Wireless Networking PerformanceNAP Throughput
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Wireless Networking Performance100 Wireless
Users in a Room

• Had the opportunity to examine wireless network
  performance
• 2 NAPs
• 100 wireless users
• Users were K-12 educators with Compaq laptops and
  Cisco NICs
• Observations
• 90 NICs associated with the NAP at the back of
  the room
• over time 70 NICs associated with the NAP at the
  front of the room
• teachers were asked to download images from a
  server
• aggregate load peaked at about 1 Mbps
• server was on a T1 line!
• users experienced significant delays
• was able to download a video stream from MITRE
  over wireless, through VPN at 200kbps without
  loss at the same time as image downloads
• hoped for more stress on the link!

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Wireless Networking ObservationsReal-time Mobile
Connectivity Wednesday

• Watched Webcast at 220Kbps in Ballroom
  C-Four
• Walked back to the SCinet NOC
• Webcast dropped to 34 Kbps
• Automatically reassociated
• Stopped in D320
• No audio dropouts

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Wireless Networking ObservationsReal-time Mobile
Connectivity Thursday

• Watched Webcast at 220Kbps in Ballroom
  C-Four
• Walked back to the SCinet NOC
• Webcast dropped to 34 Kbps
• Automatically reassociated
• Stopped in D320
• No audio dropouts

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Wireless Networking DetailsNAP Coverage
Experiments

• Reduced power from 30 to 15 mw
• performance improved on floor
• performance degraded between rooms
• Hypothesized that there were too many NAPs
• shut down three NAPs
• examined coverage
• performance degraded
• turned NAPs back on

Channel 1
86
82
Channel 6
81
83
Channel 11
85
84
72
30
76
73
D322
71
74
D321
75
D324
D320
D327
35
B4
B3
B2
B1
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Wireless NetworkingElectromagnetic Interference
(EMI)

• EMI seen as very large numbers of CRC errors
• 802.11b wireless Ethernet operates in the 2.4 GHz
  non-licenced frequency band along with
• telephones
• wireless television cameras
• wireless closed captioning devices
• other 802.11 networking hardware
• microwave ovens
• EMI was a significant problem on the conference
  showfloor
• booths wanted their own wireless networks
• the company doing attendee registration brought
  wireless
• numerous wireless appliances
• EMI was not a problem downstairs in another part
  of the building

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Wireless Network Monitoring Lessons Learned

• Be prepared to bring your own server
• preinstall any software
• test the application before deployment
• A good network monitoring package will assist
  during network deployment
• autodiscovery tie it to the DHCP server
• monitor actual system parameters
• Virtual topology is not enoughespecially for
  wireless need spatial location information
• Require other information in readily available
  format to monitor wireless
• transmitter setup frequency and power setting
• trap on several errors radio statistics and CRC
  errors
• links to web server in each NAP
• Need to fix network configuration when fully
  deployed to test for
• unexpected additions
• hardware failures

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Wireless NetworkingLessons Learned

• SCinet2000 offered a unique testbed to examine
  wireless
• large numbers of NAPs (38) and users (360) (100
  in a room)
• able to learn from staff that have deployed
  wireless networks
• 802.11b wireless Ethernet is nearly ubiquitous
• more than 250 attendees brought their own NICs
• should have even greater exposure in the future
• EMI is a serious problem
• will need exclusive control of the 2.4 GHz
  frequency band
• need gear to be able to search out noise sources
• Throughput performance had potentially
  significant problems
• acceptable performance for reading email, some
  multimedia applications, and light web browsing
• unacceptable for large file transfers over WANs
  and some multimedia applications serious work
  required a switched, wired connection