2.2 Message Syntax

DRT messages are designed for future extensibility such that each message element (for example, a field or set of fields) of each message is self-describing. As a result, the messages defined in this section have a number of FieldID and Length pairs that occur throughout the messages. Although each field is specified in the individual messages, it is helpful to explain the convention used.

The pattern used looks similar to the following.

0	1	2	3	4	5	6	7	8	9	1 0	1	2	3	4	5	6	7	8	9	2 0	1	2	3	4	5	6	7	8	9	3 0	1
FieldID																Length
Field Data (variable)
...

FieldID (2 bytes): Constant indicating the kind of field.

Value	Meaning
DRT_HEADER 0x0010	Part of a DRT Header.
DRT_HEADER_ACKED 0x0018	An Acked MessageID follows.
DRT_ID 0x0030	A DRT ID follows.
TARGET_DRT_ID 0x0038	A Target DRT ID follows.
VALIDATE_DRT_ID 0x0039	A Validate DRT ID follows.
FLAGS_FIELD 0x0040	A flags field follows. The meaning of the individual flags is message-specific.
FLOOD_CONTROLS 0x0043	Flood criteria follows.
SOLICIT_CONTROLS 0x0044	Solicit criteria follows.
LOOKUP_CONTROLS 0x0045	Lookup criteria follows.
EXTENDED_PAYLOAD 0x005A	Extended payload follows.
DRT_ID_ARRAY 0x0060	An array of DRT IDs follows.
CREDENTIAL 0x0080	A Credential follows.
WCHAR 0x0084	A Unicode character follows.
CLASSIFIER 0x0085	A classifier string follows.
HASHED_NONCE 0x0092	A hashed nonce follows.
NONCE 0x0093	A nonce follows.
SPLIT_CONTROLS 0x0098	Buffer fragmentation information follows.
ROUTING_ENTRY 0x009A	A ROUTE_ENTRY follows.
VALIDATE_CPA 0x009B	An Encoded CPA structure follows, containing a CPA to validate.
REVOKE_CPA 0x009C	An Encoded CPA structure follows, containing a CPA to revoke.
IPV6_ENDPOINT 0x009D	An IPV6_ENDPOINT structure follows.
IPV6_ENDPOINT_ARRAY 0x009E	An array of IPV6_ENDPOINT structures follows.
KEYTOKEN 0x009F	A Keytoken structure follows.
ENCRYPTED_ENDPOINT_ARRAY 0x00A0	An encrypted IPV6_ENDPOINT_ARRAY field.
ENCRYPTED_ROUTING_ENTRY 0x00A1	An encrypted ROUTE_ENTRY field.
ENCRYPTED_CPA 0x00A2	An encrypted VALIDATE_CPA field.
ENCRYPTED_CLASSIFIER 0x00A3	An encrypted CLASSIFIER field.
ENCRYPTED_PAYLOAD 0x00A4	An encrypted EXTENDED_PAYLOAD field.
SIGNATURE 0x00A5	A signature.
KEY_IDENTIFIER 0x00A6	Used to identify which key is used to generate the KEYTOKEN.

Length (2 bytes): The length, in bytes, of the Field Data field.

Field Data (variable): Data comprising the body of this field. This data MUST be present if Length is set to a number greater than zero.

The FieldID fields in each message defined by DRT always start on a 4-byte boundary from the beginning of the DRT message. Padding fields will be included in a message to ensure this.

Unless otherwise specified, all 2-byte and 4-byte integer fields are defined in network byte order.