Rusty Russell [ARCHIVE] on Nostr: 📅 Original date posted:2022-05-26 📝 Original message: Matt Corallo <lf-lists at ...

📅 Original date posted:2022-05-26
📝 Original message:
Matt Corallo <lf-lists at mattcorallo.com> writes:
>>> I agree there should be *some* rough consensus, but rate-limits are a locally-enforced thing, not a
>>> global one. There will always be races and updates you reject that your peers dont, no matter the
>>> rate-limit, and while I agree we should have guidelines, we can't "just make them the same" - it
>>> both doesn't solve the problem and means we can't change them in the future.
>>
>> Sure it does! It severly limits the set divergence to race conditions
>> (down to block height divergence, in practice).
>
> Huh? There's always some line you draw, if an update happens right on the line (which they almost
> certainly often will because people want to update, and they'll update every X hours to whatever the
> rate limit is), then ~half the network will accept the update and half won't. I don't see how you
> solve this problem.

The update contains a block number. Let's say we allow an update every
100 blocks. This must be <= current block height (and presumably, newer
than height - 2016).

If you send an update number 600000, and then 600100, it will propagate.
600099 will not.

If some nodes have 600000 and others have 600099 (because you broke the
ratelimiting recommendation, *and* propagated both approx the same
time), then the network will split, sure.

We could be fascist and penalize nodes which do this, but that's
overkill unless it actually happens a lot.

Nodes which want to keep an potential update "up their sleeve" will
backdate updates by 101 blocks (everyone should do this, in fact).

As I said, this has a problem with block height differences, but that's
explicitly included in the messages so you can ignore and wait if you
want. Again, may not be a problem in practice.

>> Maybe. What's a "non-update" based sketch? Some huge percentage of
>> gossip is channel_update, so it's kind of the thing we want?
>
> Oops, maybe we're on *very* different pages, here - I mean doing sketches based on "the things that
> I received since the last sync, ie all the gossip updates from the last hour" vs doing sketches
> based on "the things I have, ie my full gossip store".

But that requires state. Full store requires none, keeping it
super-simple

Though Alex has a idea for a "include even the expired entries" then
"regenerate every N blocks" which avoids the problem that each change is
two deltas (one remove, one add), at cost of some complexity.

Cheers,
Rusty.