Collaboration network testbed

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.

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.

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  The two rooms

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  Server/Monitoring Room

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  View into Front Room

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  Active Antennas

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

• test 0317A, 23 of 25 laptops join Simple Mesh
• test 0331A, 27 of 28 laptops join Simple Mesh
• test 0321C, 20 of 21 laptops join Simple Mesh
• test 0331B, test 0331C, 28 of 28 laptops join Simple Mesh
• test 0321A, 10 of 10 laptops join Simple Mesh

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

• test 0331B, 28 laptops, 6 of 11 succeed at Chat
• test 0321C, 21 laptops, 21 of 21 succeed at 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

• test 0414A 28 laptops
• test 0414B 28 laptops
• test 0414D 28 laptops
• test 0323A 10 laptops
• test 0323B 10 laptops
• test 0323C 15 laptops
• test 0323D 10 laptops
• test 0323H 20 laptops
• test 0317D 29 laptops
• test 0317C

Presence

• test 0321D 38 laptops
• test 0317E 29 laptops

Chat

• test 0323E 15 laptops

Write sharing

• test 0414C 20 laptops
• test 0414E 8 invites to another
• test 0321E

Read sharing

• test 0323F 10 laptops
• test 0323G 10 laptops

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.

Test	Num. Laptops	Timing	Spacing	Success	Comments
test 0323G	10	staged 5 sec	1 table	90%
test 0323H	20	staged 7.5 sec	2 tables	90%	groups of 2, 15 sec apart
test 0323E	15	staged 10 sec	spaced, 20 cm	87%
test 0323B	10	simul.	spaced	80%
test 0323F	10	simul.	1 table	80%
test 0317D	29	grouped	3 tables	76%	3 groups of 10, 5 min. apart
test 0323C	15	simul.	spaced, 30 cm.	73%
test 0317E	29	simul.	3 tables	72%
test 0323D	10	simul.	spaced, 60 cm.	60%
test 0321D	38	simul.	4 tables	60%
test 0323A	10	simul.	1 table	60%

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

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

• Test 0331D, 28 laptops, 9 of 10 successful

Write sharing

• Test 0331E, 28 laptops, 5 of 10 successful
• Test 0330A, Two laptops, 2 of 2 successful
• Test 0330C, Three laptops, 3 of 3 successful
• Test 0330D, Six laptops, 6 of 6 successful

Measure

• Test 0330B, Two laptops, successful

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.