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tendermint/peer/README.md
2014-06-27 17:03:13 -07:00

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## Channels
Each peer connection is multiplexed into channels.
<hr />
### Default channel
The default channel is used to communicate state changes, pings, peer exchange, and other automatic internal messages that all P2P protocols would want implemented.
<table>
<tr>
<td><b>Channel</b></td>
<td>""</td>
</tr>
<tr>
<td><b>Messages</b></td>
<td>
<ul>
<li>PingMsg/PongMsg</li>
<li>PeerExchangeMsg</li>
<li>RefreshFilterMsg</li>
</ul>
</td>
</tr>
</table>
<hr />
### Block channel
The block channel is used to propagate block or header information to new peers or peers catching up with the blockchain.
<table>
<tr>
<td><b>Channel</b></td>
<td>"block"</td>
</tr>
<tr>
<td><b>Messages</b></td>
<td>
<ul>
<li>RequestMsg</li>
<li>BlockMsg</li>
<li>HeaderMsg</li>
</ul>
</td>
</tr>
<tr>
<td><b>Notes</b></td>
<td>
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' &lt;= 'h_h'.
</td>
</tr>
</table>
<hr />
### 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.
<table>
<tr>
<td><b>Channel</b></td>
<td>"mempool"</td>
</tr>
<tr>
<td><b>Messages</b></td>
<td>
<ul>
<li>MempoolTxMsg</li>
</ul>
</td>
</tr>
<tr>
<td><b>Notes</b></td>
<td>
Instead of keeping a perfect inventory of what peers have, we use a lossy filter.<br/>
Bloom filter (n:10k, p:0.02 -> k:6, m:10KB)<br/>
Each peer's filter has a random nonce that scrambles the message hashes.<br/>
The filter & nonce refreshes every new block.<br/>
</td>
</tr>
</table>
<hr />
### Consensus channel
The consensus channel broadcasts all information used in the rounds of the Tendermint consensus mechanism.
<table>
<tr>
<td><b>Channel</b></td>
<td>"consensus"</td>
</tr>
<tr>
<td><b>Messages</b></td>
<td>
<ul>
<li>ProposalMsg</li>
<li>VoteMsg</li>
<li>NewBlockMsg</li>
</ul>
</td>
</tr>
<tr>
<td><b>Notes</b></td>
<td>
How do optimize/balance propagation speed & bandwidth utilization?
</td>
</tr>
</table>
## Resources
* http://www.upnp-hacks.org/upnp.html