As Tier says, the current network message limit is 2MB (reduced from 32MB
in the... uhh, 0.10? release).

I think keeping the consensus rules distinct from limitations of the p2p
network makes sense-- we are already seeing different protocols for
announcing transactions and blocks (Matt's relay network is, essentially, a
separate protocol). I could write a separate BIP describing the change to
the p2p network protocol, but that feels like busy-work to me.

RE: setting the DoS size check farther than 2 hours into the future: the
block, itself, will be rejected if it has a timestamp more than 2 hours in
the future. That is already a consensus rule.

RE: what happens if block timestamps are not in chronological order:
Nothing.

The activation counting happens in block-height-order, so timestamps on all
but the "activating" block are all that matters.

Code that looks for the activation condition must properly handle re-orgs
around the activation block, of course.


RE: testnet parameters:  big blocks can be tested in -regtest mode with
arbitrary timestamps in the past or future. Testing maximum-8MB-blocks
mined "in the past" on testnet will just result in a testnet that is even
more useless for ordinary testing of products or services being developed
-- part of what makes testnet useful for things like testing transaction
creation code is it syncs quickly.

That said, I have thought for a while now somebody should take a fresh look
at the testnet, talk to people who might be customers for a reset testnet
or testnets (we probably want separate testnets for people testing mining
and people testing transaction creation, for example), and implement
testnets designed to make it easy to test what people need testing.

RE: scraping together money to run a few hundred full-load full-nodes:
 hardware is cheap, people are expensive. You seem to expect that companies
will be willing to invest the time of their people testing something that
may never happen (8MB of transactions every ten minutes). Maybe they would,
but most companies are very busy trying to stay in business by attracting
customers to their products or services. Scaling up is a good problem to
have, and, in my experience, the way to be successful scaling up is to
tackle problems as they occur.

Because there's no use spending a bunch of person-hours hyper-optimizing
for 8MB blocks stored in MySQL if a year from now you find out your
customers don't actually want your product or MySQL 5.11 comes out and is
100 times faster....

-- 
--
Gavin Andresen