Node Handshake Content

Collected data from bitcoin.it, bitcoin.org, and bitcoinbook.git.

protocol/network/messages/version.md

@@ -19,8 +19,12 @@ The node connection is not considered established until both nodes have sent and
 | block height | 4 bytes | unsigned integer<sup>[(LE)](/protocol/misc/endian/little)</sup> | The height of the block with the highest height known to the sending node. |
 | relay flag | 1 byte | boolean | Indicates whether the sending node would like all broadcasted transactions relayed to it.  See [BIP-37](/protocol/forks/bip-0037).  This flag is sometimes referred to as "fRelay". |
 
-Note: appending extra data after the `relay flag` is ignored.
+Note: Protocol version `70001` introduced the optional `relay flag`.
-Historically, extra data after the `relay flag` would sometimes result in the connection being banned, although this is no longer standard behavior.
+Transmitting the `relay flag` byte to Nodes with a version less than `70001` may result in incompatibility with versions that validate the Version message for a specific byte count.
+
+Note: Historically, transmitting extra data after the `relay flag` would result in the connection being banned by some Nodes.
+Modern Nodes ignore extra data after the `relay flag`.
+
 
 ## Version Number
 

protocol/network/node-handshake.md

@@ -1 +1,33 @@
-# Node Handshake
+# Node Handshake
+
+When nodes connect the issue a connection handshake in order to ensure compatibility between the two nodes.
+The handshake informs the peer of its:
+
+- Network Protocol Version
+- Block Height
+- Supported [Network Services](/protocol/network/messages/version#services-bitmask)
+
+Either Node may then decide to disconnect from the peer.
+
+Neither Node should send any data other than a [Version](/protocol/network/messages/version) message to the peer until it has also received a Version message.
+Once a node has received (and sent) a Version message, it may send a [Verack](/protocol/network/messages/verack) message.
+Once each Node has sent and received a Verack message, normal node operation may begin.
+
+## Sequence Diagram
+
+When a local Node initiates a connection to a remote Node, the remote Node will remain silent it receives a version message.
+
+```
+# SequenceDiagram
+
+title Node Handshake
+
+Local->>Remote: Sends Version Message
+note right of Remote: Version Message contains Local's Version Number.
+Remote->>Local: Sends Version Message
+note left of Local: Version Message contains Remote's Version Number.
+Remote->>Local: Sends Verack Message
+note left of Local: Local uses the lower of the two Version Numbers, if compatible.
+Local->>Remote: Sends Verack Message
+note right of Remote: Remote uses the lower of the two Version Numbers, if compatible.
+```