Collaboration network testbed

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While the OLPC Mesh Testbed is conveniently located in the same space used by OLPC for development and business activities, it suffers from an excess of unrelated wireless traffic. In order to allow repeatable testing of larger numbers of laptops, a larger testbed has been set up at another location in the Boston area, where the 802.11b spectrum is relatively unused.

Test Setup

At this location, we currently have a hundred laptops and a school server, along with a separate packet recording machine. Ten laptops are grouped together on each 1.5 m by 0.7 m table. We hope to grow to at least a hundred and fifty laptops over time.

Image:PeabodyAnnex.png

While we will eventually provide remote automated control of large portions of the testing, we are currently performing tests manually.

The laptop developer keying, upgrading, and application installation is done using USB keys.

Tests and Results

The tests are grouped according to the type of network used when they were performed: simple mesh, simple collaboration over managed WiFi, a mesh with a school server, or access points with a school server.

All packet traces are in wireshark format, and contain beacon and link layer management frames as well as IP packets. They were obtained using tcpdump -i rtapX -w filename.

More specifically, interfaces are configured to the appropriate channels at boot time via ifcfg_ethX files in /etc/sysconfig/network-scripts/ (eth1 to channel 1, eth2 to channel 11, and eth3 to channel 6). There is a script, setup_snoop, for setting up the interfaces which is run once after boot. Another, do_snoop, is used to start logging. Logging is stopped with sudo killall tcpdump

Simple Mesh

In these tests, the laptops are connected solely to one another, through the wireless mesh. All presence and collaboration is Peer-to-Peer.

Startup

Write sharing

  • test 0331A, 28 laptops, 5 of 7 succeed at joining Write
  • test 0321B, 10 laptops, 9 of 9 succeed at joining Write
  • test 0317B, 25 laptops, 7 of 10 succeed at joining Write

Read sharing

  • test 0331C, 28 laptops, 0 of 5 succeed at joining Read
  • test 0321A, 10 laptops, 0 of 2 succeed at joining Read

Chat

School Server Mesh

In these tests, a School server equipped with one to three Active Antenna provides the interconnection for the laptops. In general, the laptops are registered with the school server and using the school's presence service.

Startup & Registration

Presence

Chat

Write sharing

Read sharing

Startup Problems (#5963)

This table summarizes the tests done in search of information on Trac ticket 4153 (Trac ticket 5963 is a duplicate), an inability to reliably DHCP upon startup that impacts other use of the mesh as well. The information listed after each test is the number of laptops involved in the test, how they were started up (simultaneously or staggered in some way), and the number that successfully managed to find a school portal.

TestNum. LaptopsTimingSpacingSuccessComments
test 0323G10staged 5 sec1 table90%
test 0323H20staged 7.5 sec2 tables90%groups of 2, 15 sec apart
test 0323E15staged 10 secspaced, 20 cm87%
test 0323B10simul.spaced80%
test 0323F10simul.1 table80%
test 0317D29grouped3 tables76%3 groups of 10, 5 min. apart
test 0323C15simul.spaced, 30 cm.73%
test 0317E29simul.3 tables72%
test 0323D10simul.spaced, 60 cm.60%
test 0321D38simul.4 tables60%
test 0323A10simul.1 table60%

School Server WiFi

In these tests, the laptops are connected to the School server through normal 802.11b/g access points. In general, the laptops are registered with the school server and using the school's presence service.

Presence

  • test 0410A, 76 laptops startup, 13 failed to associate, another 17 had problems
  • test 0410B, 50 laptops startup, all associated, 8 had presence problems, others missing neighbors
  • test 0410C, 50 laptops startup, 2 failed to associate, 6 had presence problems, others missing neighbors
  • test 0410D, 49 laptops startup + BW hog, 5 failed to associate, 6 had presence problems
  • test 0408B, 38 laptops staged startup, no problems
  • test 0408F, 77 laptops startup, 6 didn't associate
  • test 0331G, poor AP, 28 laptops startup, pure chaos
  • test 0323J, poor AP
  • test 0323K, poor AP

Write sharing

  • test 0410F, 50 laptops + BW hog, 40 successfully sharing Write and Chat
  • test 0331H, poor AP, 24 laptops, no collaboration

Read sharing

Chat

  • test 0410E, 50 laptops + BW hog, 49 successfully sharing Chat
  • test 0408C, 78 laptops, 75 successfully sharing Chat

Simple WiFi

In these tests, the laptops are connected to one another and the Internet, through a normal 802.11b/g access point. All presence and collaboration is Peer-to-Peer.

Chat

Write sharing

Measure

Read sharing

  • Test 0331F, 28 laptops, 440 KB file, 1.5 of 4 successful
  • Test 0330E, Six laptops, 2.2 MB file, 0 of 6 successful
  • Test 0330F, Six laptops, 40 KB file, 5 of 6 successful
  • Test 0330G, Six laptops, 440 KB file, 6 of 6 successful
  • Test 0330H, Six laptops, 440 KB file, 6 of 6 successful

Jabber Scaling

In these tests, the laptops are connected to one school server via the Internet. There is no local RF contention. This isolates the Jabber server and can be performed by many isolated individuals.

Server health

Presence

Chat sharing

Write sharing

Read sharing

Record sharing

Browse sharing

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