Developers.Gnutella.Extending

Extending the Protocol

Servents MAY extend the protocol or even change parts of it

When two Gnutella computers connect, they exchange handshake headers. These headers advertise the advanced features that they support. If both computers support a feature, they can use it.

This protocol also allows for extensions inside many messages. Such extensions can pass through servents that do not know about the extension to reach servents that do.

I think this is the GGEP blocks.