How do I find out what version Protocol specification is describing?
There's now a good overview at https://bitcoin.org/en/developer-reference#protocol-versions. The latest as of March 2014 is 70002.
The latest protocol version can be found by looking at the latest canonical Bitcoin client implementation source code currently v0.8.5 at https://github.com/bitcoin/bitcoin/blob/v0.8.5/src/version.h#L28. This should tally with what is described at https://en.bitcoin.it/wiki/Protocol_specification.