From: Luke Dashjr <luke@dashjr.org>
To: Alex Morcos <morcos@gmail.com>
Date: Wed, 17 Feb 2016 02:36:09 +0000
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Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] [BIP Proposal] New "feefilter" p2p message
Precedence: list

On Wednesday, February 17, 2016 2:28:31 AM Alex Morcos wrote:
> On Tue, Feb 16, 2016 at 6:46 PM, Luke Dashjr <luke@dashjr.org> wrote:
> > On Tuesday, February 16, 2016 8:20:26 PM Alex Morcos via bitcoin-dev 
wrote:
> > > # The feefilter message is defined as a message containing an int64_t
> > 
> > where
> > 
> > > pchCommand == "feefilter"
> > 
> > What happened to extensibility? And why waste 64 bits for what is almost
> > certainly a small number?
> 
> I thought that extensibility was already sufficient with the command string
> system.  If we come up with a better version of the feefilter later we can
> just give it a different command name.

We shouldn't need a new protocol [extension] for every new policy. Obviously 
this can't be perfectly flexible, but supporting different feerate definition 
versions is trivial and obvious.

> > > # The fee filter is additive with a bloom filter for transactions so if
> > an
> > > SPV client were to load a bloom filter and send a feefilter message,
> > > transactions would only be relayed if they passed both filters.
> > 
> > This seems to make feefilter entirely useless for wallets?
> 
> I don't follow this comment?  Transactions aren't synced with the wallet
> unless they are accepted into the mempool.  Sending feefilter messages
> should not reduce the number of transactions that are accepted to the
> mempool.

In Core, they aren't (but Core never uses bloom filters anyway) - because 
otherwise it would leak privacy. But light clients (particularly overlapping 
with those that use bloom filters!) have no privacy in the first place, so 
they have no reason to use this rule.

Luke