10. IANA Considerations
10.1. DSO OPCODE Registration
The IANA has assigned the value 6 for DNS Stateful Operations (DSO) in the "DNS OpCodes" registry.
10.2. DSO RCODE Registration
IANA has assigned the value 11 for the DSOTYPENI error code in the "DNS RCODEs" registry. The DSOTYPENI error code ("DSO-TYPE Not Implemented") indicates that the receiver does implement DNS Stateful Operations, but does not implement the specific DSO-TYPE of the Primary TLV in the DSO request message.
10.3. DSO Type Code Registry
The IANA has created the 16-bit "DSO Type Codes" registry, with initial (hexadecimal) values as shown below:
| Type | Name | Early Data | Status | Reference |
|---|---|---|---|---|
| 0000 | Reserved | NO | Standards Track | RFC 8490 |
| 0001 | KeepAlive | OK | Standards Track | RFC 8490 |
| 0002 | RetryDelay | NO | Standards Track | RFC 8490 |
| 0003 | EncryptionPadding | NA | Standards Track | RFC 8490 |
| 0004-003F | Unassigned, reserved for DSO session-management TLVs | NO | ||
| 0040-F7FF | Unassigned | NO | ||
| F800-FBFF | Experimental/local use | NO | ||
| FC00-FFFF | Reserved for future expansion | NO |
The meanings of the fields are as follows:
Type: The 16-bit DSO type code.
Name: The human-readable name of the TLV.
Early Data: If OK, this TLV may be sent as early data in a TLS zero round-trip (Section 2.3 of the TLS 1.3 specification [RFC8446]) initial handshake. If NA, the TLV may appear as an Additional TLV in a DSO message that is sent as early data.
Status: RFC status (e.g., "Standards Track") or "External" if not documented in an RFC.
Reference: A stable reference to the document in which this TLV is defined.
Note: DSO Type Code zero is reserved and is not currently intended for allocation.
Registrations of new DSO Type Codes in the "Reserved for DSO session-management" range 0004-003F and the "Reserved for future expansion" range FC00-FFFF require publication of an IETF Standards Action document [RFC8126].
Requests to register additional new DSO Type Codes in the "Unassigned" range 0040-F7FF are to be recorded by IANA after Expert Review [RFC8126]. The expert review should validate that the requested type code is specified in a way that conforms to this specification, and that the intended use for the code would not be addressed with an experimental/local assignment.
DSO Type Codes in the "experimental/local" range F800-FBFF may be used as Experimental Use or Private Use values [RFC8126] and may be used freely for development purposes or for other purposes within a single site. No attempt is made to prevent multiple sites from using the same value in different (and incompatible) ways. There is no need for IANA to review such assignments (since IANA does not record them) and assignments are not generally useful for broad interoperability. It is the responsibility of the sites making use of "experimental/local" values to ensure that no conflicts occur within the intended scope of use.
Any document defining a new TLV that lists a value of "OK" in the Early Data column must include a threat analysis for the use of the TLV in the case of TLS zero round-trip. See Section 11.1 for details.