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12. IANA Considerations

This document uses several value spaces maintained in IANA registries. This section documents the impact and requirements of RFC 5246 on these registries.

12.1. TLS Content Type Registry​

The TLS record layer uses the ContentType field to indicate the content of the record. IANA maintains the TLS Content Type Registry, with defined values including:

  • change_cipher_spec(20)
  • alert(21)
  • handshake(22)
  • application_data(23)

New content type values are assigned by IETF Consensus, as defined in RFC 5226.

12.2. TLS Alert Registry​

TLS uses the AlertDescription field to indicate the nature of an alert. IANA maintains the TLS Alert Registry. Alerts defined by RFC 5246 include:

  • close_notify(0)
  • unexpected_message(10)
  • bad_record_mac(20)
  • decryption_failed_RESERVED(21)
  • record_overflow(22)
  • decompression_failure(30)
  • handshake_failure(40)
  • bad_certificate(42)
  • unsupported_certificate(43)
  • certificate_revoked(44)
  • certificate_expired(45)
  • certificate_unknown(46)
  • illegal_parameter(47)
  • unknown_ca(48)
  • access_denied(49)
  • decode_error(50)
  • decrypt_error(51)
  • protocol_version(70)
  • insufficient_security(71)
  • internal_error(80)
  • user_canceled(90)
  • no_renegotiation(100)
  • unsupported_extension(110)

New alert values are assigned by IETF Consensus.

12.3. TLS Handshake Type Registry​

The TLS handshake protocol uses the HandshakeType field to identify handshake message types. IANA maintains the TLS Handshake Type Registry. Defined types include:

  • hello_request(0)
  • client_hello(1)
  • server_hello(2)
  • certificate(11)
  • server_key_exchange(12)
  • certificate_request(13)
  • server_hello_done(14)
  • certificate_verify(15)
  • client_key_exchange(16)
  • finished(20)

New handshake type values are assigned by IETF Consensus.

12.4. TLS Cipher Suite Registry​

TLS uses cipher suite identifiers to specify the combination of cryptographic algorithms to be used. IANA maintains the TLS Cipher Suite Registry. RFC 5246 defines multiple cipher suites, including:

  • TLS_RSA_WITH_AES_128_CBC_SHA
  • TLS_RSA_WITH_AES_256_CBC_SHA
  • TLS_RSA_WITH_AES_128_CBC_SHA256
  • TLS_RSA_WITH_AES_256_CBC_SHA256
  • (and several other suites, see Appendix A.5 for details)

New cipher suite values can be assigned through one of the following methods:

  • IETF Consensus: For cipher suites in standards track or BCP RFCs
  • Specification Required: For other cases, requiring a publicly available specification

12.5. TLS Extension Type Registry​

TLS Hello messages may contain extensions. IANA maintains the TLS Extension Type Registry. RFC 5246 defines the signature_algorithms(13) extension.

New extension type values are assigned by IETF Review or IESG Approval according to RFC 5226.

12.6. Other Registries​

TLS also uses the following IANA-maintained registries:

  • TLS Compression Method Registry: For specifying compression algorithms
  • TLS EC Curve Type Registry: For elliptic curve cryptography
  • TLS EC Point Format Registry: For representation of EC points
  • TLS Signature Algorithm Registry: For digital signature algorithms

Note: For complete IANA registration requirements and procedures, please refer to the full text of Section 12 of RFC 5246.

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