You can't eliminate the complexity (yet), otherwise you wouldn't be able to talk to old nodes. You'll have to wait until versions prior to a particular version are hard-forked off and can be safely dropped at connect time.

That said the reason I'm being so grumpy about this is that compared to the complexity in the rest of the system, this is such a trivial and minor detail. It's hardly even worth thinking about. I mean, we have a scripting language full of opcodes nobody ever figured out how to use and the protocol uses a mixture of byte orders, so an optional field in the version message is really not such a big deal :)


On Thu, Jun 20, 2013 at 10:17 AM, Tamas Blummer <tamas@bitsofproof.com> wrote:
I agree that this can be deferred until there is an actual new field without any harm. But then remember to update the BIP37 too saying that it is optional only if flag added in BIPXX is not present.

Your argument is that this complexity is already there so why not preserve it. I think eliminating complexity (that has no benefit) strengthens the system.

Tamás Blummer

On 20.06.2013, at 09:36, Mike Hearn <mike@plan99.net> wrote:

Sure but why not do that when there's an actual new field to add? Does anyone have a proposal for a feature that needs a new version field at the moment? There's no point changing the protocol now unless there's actually a new field to add.

Anyway I still don't see why anyone cares about this issue. The Bitcoin protocol does not and never has required that all messages have a fixed number of fields per version. Any parser written on the assumption it did was just buggy. Look at how tx messages are relayed for the most obvious example of that pattern in action - it's actually the raw byte stream that's stored and relayed to ensure that fields added in new versions aren't dropped during round-tripping. Old versions are supposed to preserve fields from the future.



On Thu, Jun 20, 2013 at 9:30 AM, Tamas Blummer <tamas@bitsofproof.com> wrote:
Hi Mike,

The issue with the current parser is that those fields are conditionally optional on that there will be no subsequent fields added.
If there will be further fields they will become manadory. 
 
Why not bump the version and parse the fields as mandatory from then on? This would be backward compatible and cleaner
going forward.

Tamas Blummer


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