[tor-relays] Improving Node Connection Testing

12xBTM 12xbtm at gmail.com
Tue Jun 2 16:45:59 UTC 2015

I once ran a node on a college network for just a few weeks. Then I 
found out at peak hours, packet loss was >90%. My measured bandwidth 
never reflected that. Now, scale that up. An enemy makes a ton of nodes 
like that, and now has a large portion of circuit going through them. 
That will cripple the usability of those circuits and their users. 
Likewise with latency.

On 2.6.15 12:26, teor wrote:
>> Date: Tue, 02 Jun 2015 11:58:25 -0400
>> From: 12xBTM <12xbtm at gmail.com>
>> This is a little write-up on the quality of data connections involving
>> nodes, and some thoughts on that. So, as of today, the quality of nodes
>> is determined by their bandwidth, uptime, and not being malicious. There
>> are two major missing factors from this, and I wanted to bounce some
>> ideas around: Latency and Packet Loss. These are fairly simple tests
>> that can be performed on nodes, albeit, it would increase the resource
>> load on the bwauths. However, nodes with high latency or packet loss
>> should be identified, and nodes should be measured with these two
>> important factors.
>> High latency will increase the delay of the circuit, but will not appear
>> in the consesus at all. A node can have enormous latency and hamper that
>> circuit without anyone knowing. The same could be said for a node that
>> drops a lot of packets, or drops a lot of packets at a certain time of
>> day (peak usage).
> Do the bwauths only measure the time to transmit the data, or do they include the time to connect as well?
> Including the time to connect would be a measure of latency, particularly for smaller file transfers.
> Are the bwauths only using one size of file transfer to measure bandwidth?
> Using a small and large size would allow measurement of mostly-latency and mostly-throughput with the current infrastructure.
> Since, as far as I know, Tor connections are in-order delivery, dropping packets will cause retransmits, and back up (parts of) the transmission. This will reduce the bandwidth as a side-effect. This reduction in bandwidth is currently measured by the bwauths - but, as you say, it isn't a direct measurement.
> In future, it would be great to have separate statistics for latency and packet loss - but this is perhaps a job for something more like Ooniprobe?
> teor
> teor2345 at gmail dot com
> pgp 0xABFED1AC
> https://gist.github.com/teor2345/d033b8ce0a99adbc89c5
> teor at blah dot im
> OTR D5BE4EC2 255D7585 F3874930 DB130265 7C9EBBC7
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