> I very much want us *not* to fall into the RPC trap yet again.  Severely
> limiting the number of message types a la HTTP or 9P makes a huge
> difference in interop.

What is the RPC trap?

> As for complexity vs. arbitrary limits, for integers as for anything
> else it is a tradeoff.  The simplest approach is always to set an
> arbitrary limit.

Varints :-p It may make sense to use something else for things like
Protocol Buffers where performance is a more important design criterion
than extensibility.