A DOoM 2 message consists of a source address, a destination address, a message type, and type-specific data.
In the initial release in order to facilitate manual testing of messaging, each of these four fields should consist solely of printable ISO 8859-1 characters, each field should be terminated by a octet of decimal value 10 (a newline), and the entire message should be terminated by an additional such octet.
In subsequent releases, routers may be required to negotiate a more efficient binary format. The negotiation will take the form of DOoM 2 messages exchanged between peer routers.
A DOoM Message Router may reject messages greater than 65,535 octets in length, unless a longer maximum length is negotiated for a connection.