Service Name and Transport Protocol Port Number Registry

Last Updated
2025-09-29
Expert(s)
TCP/UDP: Joe Touch; Eliot Lear, Kumiko Ono, Wes Eddy, Brian Trammell, 
Jana Iyengar, and Michael Scharf
SCTP: Michael Tuexen
DCCP: Eddie Kohler and Yoshifumi Nishida
Reference
[RFC6335]
Note
Service names and port numbers are used to distinguish between different
services that run over transport protocols such as TCP, UDP, DCCP, and
SCTP.

Service names are assigned on a first-come, first-served process, as
documented in [RFC6335].

Port numbers are assigned in various ways, based on three ranges: System
Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private
Ports (49152-65535); the different uses of these ranges are described in
[RFC6335]. According to Section 8.1.2 of [RFC6335], System Ports are 
assigned by the "IETF Review" or "IESG Approval" procedures described in 
[RFC8126]. User Ports are assigned by IANA using the "IETF Review" process, 
the "IESG Approval" process, or the "Expert Review" process, as per 
[RFC6335]. Dynamic Ports are not assigned.

The registration procedures for service names and port numbers are
described in [RFC6335].

Assigned ports both System and User ports SHOULD NOT be used without
or prior to IANA registration.

************************************************************************
* PLEASE NOTE THE FOLLOWING:                                           *
*                                                                      *
* ASSIGNMENT OF A PORT NUMBER DOES NOT IN ANY WAY IMPLY AN             *
* ENDORSEMENT OF AN APPLICATION OR PRODUCT, AND THE FACT THAT NETWORK  *
* TRAFFIC IS FLOWING TO OR FROM A REGISTERED PORT DOES NOT MEAN THAT   *
* IT IS "GOOD" TRAFFIC, NOR THAT IT NECESSARILY CORRESPONDS TO THE     *
* ASSIGNED SERVICE. FIREWALL AND SYSTEM ADMINISTRATORS SHOULD          *
* CHOOSE HOW TO CONFIGURE THEIR SYSTEMS BASED ON THEIR KNOWLEDGE OF    *
* THE TRAFFIC IN QUESTION, NOT WHETHER THERE IS A PORT NUMBER          *
* REGISTERED OR NOT.                                                   *
************************************************************************

Request an Assignment
  [https://www.iana.org/protocols/apply]

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Service Name Port Number Transport Protocol Description Assignee Contact Registration Date Modification Date Reference Service Code Unauthorized Use Reported Assignment Notes
dns-push-tls tcp DNS Push Notification Service Type [IESG] [IETF_Chair] 2019-11-25 [RFC8765, Section 6.1] Defined TXT Keys: None
dns-update-tls tcp DNS Dynamic Update Service over TLS [Stuart_Cheshire] [Stuart_Cheshire] 2019-05-04 [RFC6281] DNS Dynamic Update Service for a given domain may not necessarily be provided by the principal name servers as advertised by the domain's "NS" records, and may not necessarily always be provided on port 53. The "_dns-update._udp.<domain>." SRV record gives the target host and port where DNS Dynamic Update Service is provided for the named domain.
dots-call-home tcp DOTS Signal Channel Call Home Protocol. The service name is used to construct the SRV service names "_dots-call-home._udp" and "_dots-call-home._tcp" for discovering Call Home DOTS clients used to establish DOTS signal channel call home. [IESG] [IETF_Chair] 2020-11-19 [RFC8973] Defined TXT keys: None
dots-call-home udp DOTS Signal Channel Call Home Protocol. The service name is used to construct the SRV service names "_dots-call-home._udp" and "_dots-call-home._tcp" for discovering Call Home DOTS clients used to establish DOTS signal channel call home. [IESG] [IETF_Chair] 2020-11-19 [RFC8973] Defined TXT keys: None
dots-data tcp DOTS Data Channel Protocol. The service name is used to construct the SRV service name "_dots-data._tcp" for discovering DOTS servers used to establish DOTS data channel. [IESG] [IETF_Chair] 2020-11-19 [RFC8973] Defined TXT keys: None
est-coaps udp EST over secure CoAP (EST-coaps) [Toerless_Eckert_3] [Toerless_Eckert_3] 2022-05-03 2022-05-04 [RFC9148]. Defined TXT keys: None
help HELP command [RFC1078] TCP Port Service Multiplexer (TCPMUX)
im tcp Instant Messaging [RFC3861]
im udp Instant Messaging [RFC3861]
jmap tcp JSON Meta Application Protocol [IESG] [IETF_Chair] 2016-01-22 2019-07-16 [RFC8620] This service name was previously assigned under the name "JSON Mail Access Protocol". This has been de-assigned and re-assigned with the approval of the previous assignee.
jnx-kcsync tcp jollys keychain cloud sync protocol [Patrick_Stein] [Patrick_Stein] 2011-10-24 Defined TXT keys: hash=<40hex characters> salt=<40hex characters> uuid=<40hex characters> Example: hash=5e7580598c0d7064d4fc79faaeb42585e1a675f8 salt=f0164cb3a0c3d7efe75abea8fda86d2d56c8dda9 uuid=db61dc092922252e45bbb264f59147138c7fd5fa
lontalk LonTalk over IP (ANSI 852) [Michael_Tennefoss] [Michael_Tennefoss] Defined TXT keys: None
lxi LXI [Nick_Barendt_2] [Nick_Barendt_2] Defined TXT keys: txtvers, *IDN?=<response defined by IEEE 488; e.g., manufacturer, model, serial number, version>
meshcop udp Thread Mesh Commissioning [Thread_Group_Inc] [Esko_Dijk] 2020-11-20 Defined TXT keys: Thread 1.1 Specification, Section 8.4.1.1.2. https://www.threadgroup.org/ThreadSpec
meshcop-e udp Thread Mesh Commissioning Ephemeral-key [Thread_Group_Inc] [Esko_Dijk] 2024-01-22 Defined TXT keys: TXT records keys, if any, will be defined in Section 8.12 of the Thread Specification. https://www.threadgroup.org/ThreadSpec
pkixrep Public Key Infrastructure Repository Locator Service [RFC4386]
pres tcp Presence [RFC3861]
pres udp Presence [RFC3861]
radiusdtls udp Authentication, Accounting, and Dynamic Authorization via the RADIUS protocol. This service name is used to construct the SRV service label "_radiusdtls" for discovery of RADIUS/DTLS servers. [IESG] [IETF_Chair] 2015-03-23 2015-10-06 [RFC7585] Defined TXT keys: None
radiustls tcp Authentication, Accounting, and Dynamic Authorization via the RADIUS protocol. This service name is used to construct the SRV service label "_radiustls" for discovery of RADIUS/TLS servers. [IESG] [IETF_Chair] 2015-03-23 2015-10-06 [RFC7585] Defined TXT keys: None
scpi-raw IEEE 488.2 (SCPI) Socket [Nick_Barendt_3] [Nick_Barendt_3] Defined TXT keys: None
scpi-telnet IEEE 488.2 (SCPI) Telnet [Nick_Barendt_3] [Nick_Barendt_3] Defined TXT keys: None
slpda tcp Remote Service Discovery in the Service Location [RFC3832]
slpda udp Remote Service Discovery in the Service Location [RFC3832]
spx-hmp tcp SpinetiX HMP [SpinetiX_S_A] [Diego_Santa_Cruz] 2011-10-18 Defined TXT keys: txtvers=1 cport= the port for the content HTTP server (secondary HTTP server used for content publishing) mode= the mode in which the HMP device is currently operating, one of "normal", "safe" or "recovery" serial= serial number of the HMP device firmware= firmware version string (e.g., 2.1.0-0.1.7844) model= model string (e.g., HMP100)
sztp tcp This service name is used to construct the SRV service label "_sztp" for discovering SZTP bootstrap servers. [IESG] [IETF_Chair] 2019-01-17 [RFC8572] This protocol uses HTTPS as a substrate.
timezone tcp Time Zone Data Distribution Service - non-TLS [IESG] [IETF_Chair] 2015-08-03 [RFC7808] This is an extension of the http service. Defined TXT keys: path=<context path> (as per Section 6 of [RFC6763]).
timezones tcp Time Zone Data Distribution Service - over TLS [IESG] [IETF_Chair] 2015-08-03 [RFC7808] This is an extension of the https service. Defined TXT keys: path=<context path> (as per Section 6 of [RFC6763]).

Contact Information

ID Name Organization Contact URI Last Updated
[Diego_Santa_Cruz] Diego Santa Cruz SpinetiX S.A. mailto:Diego.SantaCruz&spinetix.com 2011-10-18
[Esko_Dijk] Esko Dijk Thread Group, Inc. mailto:esko.dijk&iotconsultancy.nl 2024-01-22
[IESG] IESG mailto:iesg&ietf.org
[IETF_Chair] IETF Chair IETF mailto:chair&ietf.org
[Michael_Tennefoss] Michael Tennefoss mailto:mtennefoss&echelon.com
[Nick_Barendt_2] Nick Barendt mailto:nbarendt&vxitech.com
[Nick_Barendt_3] Nick Barendt mailto:nbarendt&vxitech.com
[Patrick_Stein] Patrick Stein mailto:Patrick.Stein&jinx.eu 2011-10-24
[SpinetiX_S_A] SpinetiX S.A. mailto:Diego.SantaCruz&spinetix.com 2011-10-18
[Stuart_Cheshire] Stuart Cheshire mailto:cheshire&apple.com 2022-07-11
[Thread_Group_Inc] Thread Group, Inc. mailto:help&threadgroup.org 2024-01-22
[Toerless_Eckert_3] Toerless Eckert mailto:tte&cs.fau.de 2022-05-03