tendermint/p2p

Channels

Each peer connection is multiplexed into channels.

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PEX channel

The PEX channel is used to exchange peer addresses.

Channel	"PEX"
Messages	pexRequestMsg pexResponseMsg

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Block channel

The block channel is used to propagate block or header information to new peers or peers catching up with the blockchain.

Channel	"block"
Messages	RequestMsg BlockMsg HeaderMsg
Notes	Nodes should only advertise having a header or block at height 'h' if it also has all the headers or blocks less than 'h'. Thus for each peer we need only keep track of two integers -- one for the most recent header height 'h_h' and one for the most recent block height 'h_b', where 'h_b' <= 'h_h'.

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Mempool channel

The mempool channel is used for broadcasting new transactions that haven't yet entered the blockchain. It uses a lossy bloom filter on either end, but with sufficient fanout and filter nonce updates every new block, all transactions will eventually reach every node.

Channel	"mempool"
Messages	MempoolTxMsg
Notes	Instead of keeping a perfect inventory of what peers have, we use a lossy filter. Bloom filter (n:10k, p:0.02 -> k:6, m:10KB) Each peer's filter has a random nonce that scrambles the message hashes. The filter & nonce refreshes every new block.

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Consensus channel

The consensus channel broadcasts all information used in the rounds of the Tendermint consensus mechanism.

Channel	"consensus"
Messages	ProposalMsg VoteMsg NewBlockMsg
Notes	How do optimize/balance propagation speed & bandwidth utilization?

Resources

• http://www.upnp-hacks.org/upnp.html