[tor-relays] Improving Node Connection Testing

12xBTM 12xbtm at gmail.com
Tue Jun 2 15:58:25 UTC 2015

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).

Mostly, latency and packet loss in nodes will negatively impact Tor's 
usability, but not it's security. However, bwauth testing of node 
latency can create a foundation of data in which we can disrupt Timing 
Attacks on the network. Also, as of the moment, node operators should 
just briefly look into these numbers for their nodes. Ensuring their 
nodes don't have a high latency or packet loss problem when connecting 
to, for example, google.com.

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