The network protocol is not quite consensus critical, but it is important.

Two implementations of the decompressor might not be bug for bug
compatible.  This (potentially) means that a block could be designed that
won't decode properly for some version of the client but would work for
another.  This would fork the network.

A "raw" network library is unlikely to have the same problem.

Rather than just compress the stream, you could compress only block
messages only.  A new "cblock" message could be created that is a
compressed block.  This shouldn't reduce efficiency by much.

If a client fails to decode a cblock, then it can ask for the block to be
re-sent as a standard "block" message.

This means that it is a pure performance improvement.  If problems occur,
then the client can just switch back to uncompressed mode for that block.

You should look into the block relay system.  This gives a larger
improvement than simply compressing the stream.  The main benefit is
latency but it means that actual blocks don't have to be sent, so gives a
potential 50% compression ratio.  Normally, a node receives all the
transactions and then those transactions are included later in the block.



On Tue, Nov 10, 2015 at 5:40 AM, Johnathan Corgan via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> On Mon, Nov 9, 2015 at 5:58 PM, gladoscc via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
>
>> I think 25% bandwidth savings is certainly considerable, especially for
>> people running full nodes in countries like Australia where internet
>> bandwidth is lower and there are data caps.
>>
>
> ​This reinforces the idea that such trade-off decisions should be be local
> and negotiated between peers, not a required feature of the network P2P.​
>
>
> --
> Johnathan Corgan
> Corgan Labs - SDR Training and Development Services
> http://corganlabs.com
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>