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I am just wondering if the devp2p protocol, which is used for node to node communication, has support for data compression?
I am asking this, because it could be useful for faster block propagation within the network. Especially, when the tx count / block increases in the future.
So far, I haven't found a hint for it in:
Yes - this came with snappy compression via EIP 706 (https://github.com/ethereum/EIPs/pull/706) - implementation in go-ethereum via https://github.com/ethereum/go-ethereum/pull/15106
I had to dig around to find the hint that I was pretty sure existed :-)
It's in the Design Rationale document, under Compression algorithm.
The wire protocol and the database both use a custom compression algorithm to store data. The algorithm can best be described as run-length-encoding zeroes and leaving other values as they are, with the exception of a few special cases for common values like sha3('').
The relevant code is in the go-ethereum/p2p directory on GitHub.
I can't immediately see how the Wire Protocol code calls into where I assume the custom compression is implemented (which is either common/bitutil/compress.go or compression/rle/read_write.go?), and there are actually some calls in the RLP code to Snappy (Google's compression library).
Perhaps further investigation is required to be sure...
