[Bitcoin-development] Segmented Block Relaying BIP draft.

[Matt Corallo]

It seems to me the whole idea of segmenting blocks would add very little
(to nothing) with any sane block size.  Sure, if a block were to be
10GB, it may make sense.  However, even in that case, it would be easier
to relay a list of tx hashes (which may be a bit expensive) and txes
separately instead of using a notion of block segments.  That said, I
don't see blocks ever being that large and if they do become that large,
as only a few full nodes will remain, upgrading their protocol would be
(relatively) easy.  I would instead encourage focus on decreasing block
relay times for the current network and as blocks approach 10MB (so that
they can approach 10MB).

Matt

On Mon, 2012-09-10 at 20:34 +0100, Matthew Mitchell wrote:
> Do you mean getdata? Here is the reason for the 6 new messages:
> 
> 
> getseginv,seginv - These are for learning about what segments of a
> block a node has. Else you could remove these messages and simply have
> nodes advertise blocks via inventory messages. In this case nodes
> would have to wait until they had fully received a block before
> relaying anything. No longer is there a benefit with nodes being able
> to relay segments of blocks before they have received the entire
> block.
> 
> 
> gettreelevel,treelevel - These are to received a level of
> the merle tree. Instead you might use get data but gettreelevel is
> more compact than get data and is clearly differentiates itself as
> part of the new protocol. Perhaps these messages could include the
> block headers alongside the hashes and you could request many at once
> like with the getheaders message? If you skip these messages, then you
> could verify the transactions at the end but there would be problems
> when peers give bad segments where data would need to be downloaded
> again.
> 
> 
> getsegment,segment - These are clearly important to request and
> receive segments for the blocks. These allows for nodes
> to download arbitrary segments of blocks. The optimum number of
> segments could be calculated by node software using measurements of
> download speeds and latency times, the number of connections and how
> likely redundancy is to occur. If a node is up-to-date and likely has
> many of the transactions in blocks, it can start asking for the
> deepest merle level (tx hashes) and ask nodes for segments, avoiding
> transactions it already has.
> 
> 
> I'll get around to doing measurements myself sometime to estimate the
> benefit of this proposal. It will certainly be beneficial when block
> sizes reach some size but not much is really known except what can be
> assumed/guessed.
> 
> 
> I should also mention the bitcointalk topic
> here: https://bitcointalk.org/index.php?topic=103295.0
> 
> On 10 Sep 2012, at 19:59, "Luke-Jr" <luke at dashjr.org> wrote:
> > 
> > Most of the problem with block propagation lies in implementation,
> > not 
> > protocol... Distributing missing transaction on an as-needed basis
> > is a 
> > possible improvement at the protocol level, but there hasn't (AFAIK)
> > been any 
> > research into whether the little benefit outweighs the cost yet. In
> > any case, 
> > I don't see why 6 new messages are needed instead of simply adding a
> > single 
> > new type to getinv?