[tor-relays] total relay bandwidth

[grarpamp]

On Fri, Sep 2, 2016 at 7:30 AM, Michael Armbruster <tor at armbrust.me> wrote:
> On 2016-09-02 at 13:18, jensm1 wrote:
>> which shows that the advertised relay bandwidth in the whole network is
>> more than double the actually used bandwidth. While it's certainly nice
>> to have a bit of breathing space to absorb load spikes, I'm wondering,

> it's always good to have even more relays or exit nodes, as more "hop
> points" for connections means more diversity throughout the network

Once a net reaches adequate bandwidth capacity, adding more
nodes can do a few things among others...
Good:
- Gives operators deployment experience till their bw is needed, at $cost.
- More non-evil relays gives better odds of building a non-evil path, but tor
weight's things so not exactly.
- May add some capacity for directory operations etc
Bad:
- Yields rather unused nodes making it easier for passive
observer to see you tack up and use a path through them,
especially if you're crafting paths.

One key here is probably that we don't have a good idea as to the
quantity of evil nodes, or the hard interest and real capabilities of PA's.

To make the call you'd need that, and perf metrics of your net under
different ratios of advertised:consumed:nodecount, and min/avg/max/stddev
of idle/random/full paths, to find any sweet spots / ranges.

Also considerations of impact adding nodes of less bandwidth or
more latency than average, versus a campaign to fund replace them.

At 42% util by one metric, it may be money and time better spent
elsewhere, even on better qualifying the default 'more nodes good' idea.