Simple bandwidth scanner (sbws)

• by Matt Traudt and juga

• 2018

• use threads

• use [StemCode], Python 3

[sbwsCode], [sbwsDoc]

Initial sbws design

exit relays were helper relays: relays with high bandwidth that would allow to exit only to the Web server

• who should own these exits?

• extra infrastructure

Which relays are measured first

• sbws prioritizes relays to be measured - new relays - relays not measured recently

How sbws perform measurements

• build two hop circuits with the relay to measure and a random exit that has similar advertised bandwidth as the relay to measure

• download a file from a Web server

• the file size is adjusted depending on whether it takes more or less time to download the file

• measure how long it takes

• store the results

sbws raw measurements compared to torflow measurements

How sbws aggregate the results

• scaling

• imitate torflow scaling

sbws linear scaling

Multiply each relay bandwidth by 7500/median

sbws scaling as torflow

Multiply each relay observed bandwidth by a ratio calculated from the measured bandwdiths

Example sbws’s bandwidth list file

aka v1.1.0 bandwidth list file [BandwidthFileSpec]

1523911758
version=1.1.0
software=sbws
software_version=0.1.0
latest_bandwidth=2018-04-16T20:49:18
file_created=2018-04-16T21:49:18
generator_started=2018-04-16T15:13:25
earliest_bandwidth=2018-04-16T15:13:26
====
bw=380 error_circ=0 error_misc=0 error_stream=1 master_key_ed25519=YaqV4vbvPYKucElk297eVdNArDz9HtIwUoIeo0+cVIpQ nick=Test node_id=$68A483E05A2ABDCA6DA5A3EF8DB5177638A27F80 rtt=380 success=1 time=2018-05-08T16:13:26
bw=189 error_circ=0 error_misc=0 error_stream=0 master_key_ed25519=a6a+dZadrQBtfSbmQkP7j2ardCmLnm5NJ4ZzkvDxbo0I nick=Test2 node_id=$96C15995F30895689291F455587BD94CA427B6FC rtt=378 success=1 time=2018-05-08T16:13:36

Dirauths’ operating system distributions

sbws system packages

• Debian package [sbwsDeb] - waiting Debian ftp master to approve it - waiting for new stem release and package update

• OpenBSD Makefile [sbwsBSD]

sbws code_design

sbwsdoc:code_design

[sbwsDia]