The messageType field indicates what type of message is being relayed, and
must conform to the following enumeration
.TS
allbox tab(:);
cb cb cb cb cb
c l l l c.
messageType:Name:On Bootstrap:On Realtime:Version
0x00:Invalid:Yes:Yes:0+
0x01:Not_A_Type:?:?:0+
0x02:Keepalive:No:Yes:0+
0x03:Publish:No:Yes:0+
0x04:Confirm_Req:No:Yes:0+
0x05:Confirm_Ack:No:Yes:0+
0x06:Bulk_Pull:Yes:No:?
0x07:Bulk_Push:Yes:No:?
0x08:Frontier_Req:Yes:No:?
0x09:Bulk_Pull_Blocks:Yes:No:11+
0x00:Invalid:Yes:Yes:1+
0x01:Not_A_Type:Yes:Yes:1+
0x02:Keepalive:No:Yes:1+
0x03:Publish:No:Yes:1+
0x04:Confirm_Req:No:Yes:1+
0x05:Confirm_Ack:No:Yes:1+
0x06:Bulk_Pull:Yes:No:1+
0x07:Bulk_Push:Yes:No:1+
0x08:Frontier_Req:Yes:No:1+
0x09:Bulk_Pull_Blocks:Yes:No:Deprecated
0x0A:Node_ID_Handshake:Yes:No:12+
0x0B:Bulk_Pull_Account:Yes:No:12+
.TE

.TP
.B "TODO: Extensions"
.B Extensions
The following message types have extension bits used as flags:
.IR Node_ID_Handshake ", " Bulk_Pull .

The following message types encode a block type in the extension bits:
.IR Publish ", " Confirm_Req ", and " Confirm_Ack .
The block type is encoded in the lower 4 bits of the first byte of the
extensions field (i.e., (extensions & 0x0f00 >> 8)).

.SS Payload
Following the message header comes the payload for the particular message
type.

.TP
.B Invalid
TODOC

.TP
.B Not_A_Type
TODOC

.TP
.B Keepalive
The
.I Keepalive
The Keepalive message serves as an introduction and beaconing mechanism for
message serves as an introduction and beaconing mechanism for
the Nano real-time network.
The Keepalive message requires exactly 8 IPv6 address and port number
tuples to be sent as its payload.  The IPv6 addresses are each 128-bits
(16-bytes) long and the port numbers are 16-bit integers sent in little endian
byte order.  The payload for the Keepalive message type is 144 bytes in size.

.TP
.B Publish
TODOC
The
.I Publish
message serves as a mechanism to introduce new blocks into the
Nano real-time network.  The block type is encoded in the
.I Extensions
field as described above.  The payload is the contents of the block.

.TP
.B Confirm_Req
TODOC
The
.I Confirm_Req
message requests that all online representatives "vote" on a block.
The block type is encoded in the
.I Extensions
field as described above.  The payload is the contents of the block
to be voted on.

.TP
.B Confirm_Ack
TODOC
The
.I Confirm_Ack
message is sent in response to either a new block being observed
by a representative or in response to an explicit
.IR Confirm_Req .
The block type is encoded in the
.I Extensions
field as described above.
If the block type is specified as
.I Not_A_Block
then the payload is a sequence of hashes.  Due to IPv4 fragment
size limits this typically does not exceed 12 hashes.  If the
block type is something other than
.I Not_A_Block
then the payload is the contents of the block that is being
voted on.

.TP
.B Bulk_Pull
The Bulk_Pull message is used to pull the entire chain for an account, down to
its beginning or to a given block.  It takes 2 arguments, both of them 256-bit.
The first argument is the account, so its 256-bit public key should be encoded
as binary in big-endian notation.  The second argument is the block hash to