Hal Finney wrote:
> I think it is necessary that nodes keep a separate 
> pending-transaction list associated with each candidate chain. 
> ... One might also ask ... how many candidate chains must 
> a given node keep track of at one time, on average?

Fortunately, it's only necessary to keep a pending-transaction pool for the current \
best branch.  When a new block arrives for the best branch, ConnectBlock removes the \
block's transactions from the pending-tx pool.  If a different branch becomes longer, \
it calls DisconnectBlock on the main branch down to the fork, returning the block \
transactions to the pending-tx pool, and calls ConnectBlock on the new branch, \
sopping back up any transactions that were in both branches.  It's expected that \
reorgs like this would be rare and shallow.

With this optimisation, candidate branches are not really any burden.  They just sit \
on the disk and don't require attention unless they ever become the main chain.


> Or as James raised earlier, if the network broadcast 
> is reliable but depends on a potentially slow flooding 
> algorithm, how does that impact performance?

Broadcasts will probably be almost completely reliable.  TCP transmissions are rarely \
ever dropped these days, and the broadcast protocol has a retry mechanism to get the \
data from other nodes after a while.  If broadcasts turn out to be slower in practice \
than expected, the target time between blocks may have to be increased to avoid \
wasting resources.  We want blocks to usually propagate in much less time than it \
takes to generate them, otherwise nodes would spend too much time working on obsolete \
blocks.

I'm planning to run an automated test with computers randomly sending payments to \
each other and randomly dropping packets.


> 3. The bitcoin system turns out to be socially useful and valuable, so
> that node operators feel that they are making a beneficial contribution
> to the world by their efforts (similar to the various "@Home" compute
> projects where people volunteer their compute resources for good causes).
> 
> In this case it seems to me that simple altruism can suffice to keep the
> network running properly.

It's very attractive to the libertarian viewpoint if we can explain it properly.  I'm \
better with code than with words though.

Satoshi Nakamoto