channel_announcementmessages containing information regarding new channels between the two nodes. They can also exchange
channel_updatemessages, which update information about a channel. There can only be one valid
channel_announcementfor any channel, but at least two
channel_updatemessages are expected.
node_announcementmessages, which supply additional information about the nodes. There may be multiple
node_announcementmessages, in order to update the node information.