Transport Layer Security (TLS) 2005-11-15 2026-04-01 Transport Layer Security (TLS) Parameters Transport Layer Security (TLS) Yoav Nir, Rich Salz, Nick Sullivan "Recommended" set to/transitioning from "Y" or "D" Either Standards Action With Expert Review or IESG Approval "Recommended" set to "N," not transitioning from another value Specification Required If the "Specification Required" procedure applies, registration requests can be sent to iana@iana.org or submitted via IANA's application form, per . IANA will forward the submission to the expert mailing list described in RFC 8447, Section 17 and track its progress. See the registration procedure table below for more information. The role of the designated expert is described in . The designated expert ensures that the specification is publicly available. It is sufficient to have an Internet-Draft (that is posted and never published as an RFC) or a document from another standards body, industry consortium, university site, etc. The expert may provide more in-depth reviews, but their approval should not be taken as an endorsement of the extension. As specified in , assignments made in the Private Use space are not generally useful for broad interoperability. It is the responsibility of those making use of the Private Use range to ensure that no conflicts occur (within the intended scope of use). For widespread experiments, temporary reservations are available. If the "Recommended" column is set to "N", it does not necessarily mean that it is flawed; rather, it indicates that the item either has not been through the IETF consensus process, has limited applicability, or is intended only for specific use cases. If the "Recommended" column is set to "D," the item is discouraged and SHOULD NOT or MUST NOT be used, depending upon the situation; consult the item's references for clarity. Abbreviations that may appear in the "TLS 1.3" field include "CH" (ClientHello), "SH" (ServerHello), "EE" (EncryptedExtensions), "CT" (Certificate), "CR" (CertificateRequest), "NST" (NewSessionTicket), and "HRR" (HelloRetryRequest). The addition of the "CR" to the "TLS 1.3" column for the server_name(0) extension only marks the extension as valid in a ClientCertificateRequest created as part of client-generated authenticator requests. Any TLS entry added after the IESG approves publication of is intended for TLS 1.3 or later, and makes no similar requirement on DTLS. Such entries should have an informal indication like "For TLS 1.3 or later" in that entry, such as the "Comment" column. 0 server_name CH, EE, CR N Y 1 max_fragment_length CH, EE N N 2 client_certificate_url - N Y 3 trusted_ca_keys - N Y 4 truncated_hmac - N D IESG Action 2018-08-16 Tag Size Does Matter: Attacks and Proofs for the TLS Record Protocol 5 status_request CH, CR, CT N Y 6 user_mapping - N Y 7 client_authz - N N 8 server_authz - N N 9 cert_type - N N 10 supported_groups (renamed from "elliptic_curves") CH, EE N Y 11 ec_point_formats - N Y 12 srp - N N 13 signature_algorithms CH, CR N Y 14 use_srtp CH, EE N Y 15 heartbeat CH, EE N Y 16 application_layer_protocol_negotiation CH, EE N Y 17 status_request_v2 - N Y 18 signed_certificate_timestamp CH, CR, CT N N 19 client_certificate_type CH, EE N Y 20 server_certificate_type CH, EE N Y 21 padding CH N Y 22 encrypt_then_mac - N Y 23 extended_main_secret - N Y 24 token_binding - N Y 25 cached_info - N Y 26 tls_lts - N N 27 compress_certificate CH, CR N Y 28 record_size_limit CH, EE N Y 29 pwd_protect CH N N 30 pwd_clear CH N N 31 password_salt CH, SH, HRR N N 32 ticket_pinning CH, EE N N 33 tls_cert_with_extern_psk CH, SH N N 34 delegated_credential CH, CR, CT N Y 35 session_ticket (renamed from "SessionTicket TLS") - N Y 36 TLMSP - N N ETSI TS 103 523-2 37 TLMSP_proxying - N N ETSI TS 103 523-2 38 TLMSP_delegate - N N ETSI TS 103 523-2 39 supported_ekt_ciphers CH, EE N Y 40 Reserved D tls-reg-review mailing list 41 pre_shared_key CH, SH N Y 42 early_data CH, EE, NST N Y 43 supported_versions CH, SH, HRR N Y 44 cookie CH, HRR N Y 45 psk_key_exchange_modes CH N Y 46 Reserved D tls-reg-review mailing list 47 certificate_authorities CH, CR N Y 48 oid_filters CR N Y 49 post_handshake_auth CH N Y 50 signature_algorithms_cert CH, CR N Y 51 key_share CH, SH, HRR N Y 52 transparency_info CH, CR, CT N Y 53 connection_id (deprecated) - Y D 54 connection_id CH, SH Y N 55 external_id_hash CH, EE N Y 56 external_session_id CH, EE N Y 57 quic_transport_parameters CH, EE N Y 58 ticket_request CH, EE N Y 59 dnssec_chain CH, CT N N 60 sequence_number_encryption_algorithms CH, HRR, SH Y N 61 rrc CH, SH Y N 62 tls_flags CH,SH,HRR,EE,CR,CT,NST N N 63-2569 Unassigned 2570 Reserved CH, CR, NST N N 2571-6681 Unassigned 6682 Reserved CH, CR, NST N N 6683-10793 Unassigned 10794 Reserved CH, CR, NST N N 10795-14905 Unassigned 14906 Reserved CH, CR, NST N N 14907-19017 Unassigned 19018 Reserved CH, CR, NST N N 19019-23129 Unassigned 23130 Reserved CH, CR, NST N N 23131-27241 Unassigned 27242 Reserved CH, CR, NST N N 27243-31353 Unassigned 31354 Reserved CH, CR, NST N N 31355-35465 Unassigned 35466 Reserved CH, CR, NST N N 35467-39577 Unassigned 39578 Reserved CH, CR, NST N N 39579-43689 Unassigned 43690 Reserved CH, CR, NST N N 43691-47801 Unassigned 47802 Reserved CH, CR, NST N N 47803-51913 Unassigned 51914 Reserved CH, CR, NST N N 51915-56025 Unassigned 56026 Reserved CH, CR, NST N N 56027-60137 Unassigned 60138 Reserved CH, CR, NST N N 60139-64249 Unassigned 64250 Reserved CH, CR, NST N N 64251-64767 Unassigned 64768 ech_outer_extensions CH N Y Only appears in inner CH. 64769-65036 Unassigned 65037 encrypted_client_hello CH, HRR, EE N Y 65038-65279 Unassigned 65280 Reserved for Private Use 65281 renegotiation_info - N Y 65282-65535 Reserved for Private Use Transport Layer Security (TLS) "Recommended" set to/transitioning from "Y" or "D" Either Standards Action With Expert Review or IESG Approval "Recommended" set to "N," not transitioning from another value Specification Required Yoav Nir, Rich Salz, Nick Sullivan If the "Specification Required" procedure applies, registration requests can be sent to iana@iana.org or submitted via IANA's application form, per . IANA will forward the submission to the expert mailing list described in RFC 8447, Section 17 and track its progress. See the registration procedure table below for more information. The role of the designated expert is described in . The designated expert ensures that the specification is publicly available. It is sufficient to have an Internet-Draft (that is posted and never published as an RFC) or a document from another standards body, industry consortium, university site, etc. The expert may provide more in-depth reviews, but their approval should not be taken as an endorsement of the certificate type. If the "Recommended" column is set to "N", it does not necessarily mean that it is flawed; rather, it indicates that the item either has not been through the IETF consensus process, has limited applicability, or is intended only for specific use cases. If the "Recommended" column is set to "D," the item is discouraged and SHOULD NOT or MUST NOT be used, depending upon the situation; consult the item's references for clarity. Any TLS entry added after the IESG approves publication of is intended for TLS 1.3 or later, and makes no similar requirement on DTLS. Such entries should have an informal indication like "For TLS 1.3 or later" in that entry, such as the "Comment" column. 0 X509 Y Was X.509 before TLS 1.3. 1 OpenPGP_RESERVED N Used in TLS versions prior to 1.3. 2 Raw Public Key Y 3 1609Dot2 N 4-223 Unassigned 224-255 Reserved for Private Use IETF Review Any TLS entry added after the IESG approves publication of is intended for TLS 1.3 or later, and makes no similar requirement on DTLS. Such entries should have an informal indication like "For TLS 1.3 or later" in that entry, such as the "Comment" column. 0 Reserved 1 ocsp 2 ocsp_multi_RESERVED Used in TLS versions prior to 1.3. 3-255 Unassigned Expert Review Yoav Nir, Rich Salz, Nick Sullivan Registration requests should be sent to iana@iana.org or submitted via IANA's application form, per . IANA will forward the request to the expert mailing list described in RFC 8447, Section 17 and track its progress. When this registry has an HTTP-specific version added or modified, the YANG module iana-http-versions must be updated as defined in . Reserved 0x0A 0x0A Reserved 0x1A 0x1A Reserved 0x2A 0x2A Reserved 0x3A 0x3A Reserved 0x4A 0x4A Reserved 0x5A 0x5A Reserved 0x6A 0x6A Reserved 0x7A 0x7A Reserved 0x8A 0x8A Reserved 0x9A 0x9A Reserved 0xAA 0xAA Reserved 0xBA 0xBA Reserved 0xCA 0xCA Reserved 0xDA 0xDA Reserved 0xEA 0xEA Reserved 0xFA 0xFA HTTP/0.9 0x68 0x74 0x74 0x70 0x2f 0x30 0x2e 0x39 ("http/0.9") HTTP/1.0 0x68 0x74 0x74 0x70 0x2f 0x31 0x2e 0x30 ("http/1.0") HTTP/1.1 0x68 0x74 0x74 0x70 0x2f 0x31 0x2e 0x31 ("http/1.1") SPDY/1 0x73 0x70 0x64 0x79 0x2f 0x31 ("spdy/1") SPDY/2 0x73 0x70 0x64 0x79 0x2f 0x32 ("spdy/2") SPDY/3 0x73 0x70 0x64 0x79 0x2f 0x33 ("spdy/3") Traversal Using Relays around NAT (TURN) 0x73 0x74 0x75 0x6E 0x2E 0x74 0x75 0x72 0x6E ("stun.turn") NAT discovery using Session Traversal Utilities for NAT (STUN) 0x73 0x74 0x75 0x6E 0x2E 0x6e 0x61 0x74 0x2d 0x64 0x69 0x73 0x63 0x6f 0x76 0x65 0x72 0x79 ("stun.nat-discovery") HTTP/2 over TLS 0x68 0x32 ("h2") HTTP/2 over TCP 0x68 0x32 0x63 ("h2c") This entry reserves an identifier for use within a cleartext version of a protocol and is not allowed to appear in a TLS ALPN negotiation. WebRTC Media and Data 0x77 0x65 0x62 0x72 0x74 0x63 ("webrtc") Confidential WebRTC Media and Data 0x63 0x2d 0x77 0x65 0x62 0x72 0x74 0x63 ("c-webrtc") FTP 0x66 0x74 0x70 ("ftp") IMAP 0x69 0x6d 0x61 0x70 ("imap") POP3 0x70 0x6f 0x70 0x33 ("pop3") ManageSieve 0x6d 0x61 0x6e 0x61 0x67 0x65 0x73 0x69 0x65 0x76 0x65 ("managesieve") CoAP (over TLS) 0x63 0x6f 0x61 0x70 ("coap") CoAP (over DTLS) 0x63 0x6f ("co") XMPP jabber:client namespace 0x78 0x6d 0x70 0x70 0x2d 0x63 0x6c 0x69 0x65 0x6e 0x74 ("xmpp-client") XMPP jabber:server namespace 0x78 0x6d 0x70 0x70 0x2d 0x73 0x65 0x72 0x76 0x65 0x72 ("xmpp-server") acme-tls/1 0x61 0x63 0x6d 0x65 0x2d 0x74 0x6c 0x73 0x2f 0x31 ("acme-tls/1") OASIS Message Queuing Telemetry Transport (MQTT) 0x6d 0x71 0x74 0x74 ("mqtt") DNS-over-TLS 0x64 0x6F 0x74 ("dot") Network Time Security Key Establishment, version 1 0x6E 0x74 0x73 0x6B 0x65 0x2F 0x31 ("ntske/1") RFC8915, Section 4 SunRPC 0x73 0x75 0x6e 0x72 0x70 0x63 ("sunrpc") HTTP/3 0x68 0x33 ("h3") SMB2 0x73 0x6D 0x62 ("smb") IRC 0x69 0x72 0x63 ("irc") NNTP (reading) 0x6E 0x6E 0x74 0x70 ("nntp") NNTP (transit) 0x6E 0x6E 0x73 0x70 ("nnsp") DoQ 0x64 0x6F 0x71 ("doq") SIP 0x73 0x69 0x70 0x2f 0x32 ("sip/2") TDS/8.0 0x74 0x64 0x73 0x2f 0x38 0x2e 0x30 ("tds/8.0") [MS-TDS]: Tabular Data Stream Protocol DICOM 0x64 0x69 0x63 0x6f 0x6d ("dicom") PostgreSQL 0x70 0x6F 0x73 0x74 0x67 0x72 0x65 0x73 0x71 0x6C ("postgresql") RADIUS/1.0 0x72 0x61 0x64 0x69 0x75 0x73 0x2f 0x31 0x2e 0x30 ("radius/1.0") RADIUS/1.1 0x72 0x61 0x64 0x69 0x75 0x73 0x2f 0x31 0x2e 0x31 ("radius/1.1") NetPerfMeter Protocol Control Channel (NPMP-CONTROL) 0x6e 0x65 0x74 0x70 0x65 0x72 0x66 0x6d 0x65 0x74 0x65 0x72 0x2f 0x63 0x6f 0x6e 0x74 0x72 0x6f 0x6c 0x0a ("netperfmeter/control") NetPerfMeter Protocol Data Channel (NPMP-DATA) 0x6e 0x65 0x74 0x70 0x65 0x72 0x66 0x6d 0x65 0x74 0x65 0x72 0x2f 0x64 0x61 0x74 0x61 0x0a ("netperfmeter/data") 0-63 Standards Action 64-223 Specification Required Yoav Nir, Rich Salz, Nick Sullivan Requests for registration in the "Specification Required" range should be sent to iana@iana.org or submitted via IANA's application form, per . IANA will forward the request to the expert mailing list described in RFC 8447, Section 17 and track its progress. See the registration procedure table below for more information. Any TLS entry added after the IESG approves publication of is intended for TLS 1.3 or later, and makes no similar requirement on DTLS. Such entries should have an informal indication like "For TLS 1.3 or later" in that entry, such as the "Comment" column. 0 Reserved 1 cert 2 cert_req 3-223 Unassigned 224-255 Reserved for Private Use 1-255 IETF Review 256-16383 Specification Required 16384-65535 Experimental Use Yoav Nir, Rich Salz, Nick Sullivan Requests for registration in the "Specification Required" range should be sent to iana@iana.org or submitted via IANA's application form, per . IANA will forward the request to the expert mailing list described in RFC 8447, Section 17 and track its progress. See the registration procedure table below for more information. Any TLS entry added after the IESG approves publication of is intended for TLS 1.3 or later, and makes no similar requirement on DTLS. Such entries should have an informal indication like "For TLS 1.3 or later" in that entry, such as the "Comment" column. 0 Reserved 1 zlib 2 brotli 3 zstd 4-16383 Unassigned 16384-65535 Reserved for Experimental Use