2000-10 2026-02-20 IETF Review A Chunk Flags sub-registry will be created for each new Chunk Type. The registration procedure for those sub-registries is RFC Required . For more information, see Section 15.2 of RFC9260. 0 Payload Data (DATA) 1 Initiation (INIT) 2 Initiation Acknowledgement (INIT ACK) 3 Selective Acknowledgement (SACK) 4 Heartbeat Request (HEARTBEAT) 5 Heartbeat Acknowledgement (HEARTBEAT ACK) 6 Abort (ABORT) 7 Shutdown (SHUTDOWN) 8 Shutdown Acknowledgement (SHUTDOWN ACK) 9 Operation Error (ERROR) 10 State Cookie (COOKIE ECHO) 11 Cookie Acknowledgement (COOKIE ACK) 12 Reserved for Explicit Congestion Notification Echo (ECNE) 13 Reserved for Congestion Window Reduced (CWR) 14 Shutdown Complete (SHUTDOWN COMPLETE) 15 Authentication Chunk (AUTH) 16-62 Unassigned 63 Reserved for IETF-defined Chunk Extensions 64 Payload Data supporting Interleaving (I-DATA) 65 DTLS (TEMPORARY - registered 2026-02-20, expires 2027-02-20) 66-126 Unassigned 127 Reserved for IETF-defined Chunk Extensions 128 Address Configuration Acknowledgment (ASCONF-ACK) 129 Unassigned 130 Re-configuration Chunk (RE-CONFIG) 131 Unassigned 132 Padding Chunk (PAD) 133-190 Unassigned 191 Reserved for IETF-defined Chunk Extensions 192 Forward TSN 193 Address Configuration Change Chunk (ASCONF) 194 I-FORWARD-TSN 195-254 Unassigned 255 Reserved for IETF-defined Chunk Extensions IETF Review 1 Heartbeat Info 2-4 Unassigned 5 IPv4 Address 6 IPv6 Address 7 State Cookie 8 Unrecognized Parameter 9 Cookie Preservative 10 Unassigned 11 Host Name Address 12 Supported Address Types 13 Outgoing SSN Reset Request Parameter 14 Incoming SSN Reset Request Parameter 15 SSN/TSN Reset Request Parameter 16 Re-configuration Response Parameter 17 Add Outgoing Streams Request Parameter 18 Add Incoming Streams Request Parameter 19-32767 Unassigned 32768 Reserved for ECN Capable (0x8000) 32769 Zero Checksum Acceptable (0x8001) 32770 Random (0x8002) 32771 Chunk List (0x8003) 32772 Requested HMAC Algorithm Parameter (0x8004) 32773 Padding (0x8005) 32774 DTLS Key Management (0x8006) (TEMPORARY - registered 2026-02-20, expires 2027-02-20) 32775 Unassigned 32776 Supported Extensions (0x8008) 32777-49151 Unassigned 49152 Forward TSN supported (0xC000) 49153 Add IP Address (0xC001) 49154 Delete IP Address (0xC002) 49155 Error Cause Indication (0xC003) 49156 Set Primary Address (0xC004) 49157 Success Indication (0xC005) 49158 Adaptation Layer Indication (0xC006) 49159-65534 Unassigned 65535 Reserved for IETF-defined Chunk Extensions RFC Required 0x01 E bit 0x02 B bit 0x04 U bit 0x08 I bit 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 T bit 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 T bit 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 E bit 0x02 B bit 0x04 U bit 0x08 I bit 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned 0x01 Unassigned 0x02 Unassigned 0x04 Unassigned 0x08 Unassigned 0x10 Unassigned 0x20 Unassigned 0x40 Unassigned 0x80 Unassigned Specification Required Michael Tuexen, Randall Stewart 1 Invalid Stream Identifier 2 Missing Mandatory Parameter 3 Stale Cookie 4 Out of Resource 5 Unresolvable Address 6 Unrecognized Chunk Type 7 Invalid Mandatory Parameter 8 Unrecognized Parameters 9 No User Data 10 Cookie Received While Shutting Down 11 Restart of an Association with New Addresses 12 User-Initiated Abort 13 Protocol Violation 14-159 Unassigned 160 Request to Delete Last Remaining IP Address 161 Operation Refused Due to Resource Shortage 162 Request to Delete Source IP Address 163 Association Aborted due to illegal ASCONF-ACK 164 Request refused - no authorization 165-260 Unassigned 261 Unsupported HMAC Identifier 262-65535 Unassigned First Come First Served 0 Reserved by SCTP 1 IUA 2 M2UA 3 M3UA 4 SUA 5 M2PA 6 V5UA 7 H.248 ITU-T Recommendation H.248 Annex H, "Transport over SCTP", November 2000. 8 BICC/Q.2150.3 ITU-T Recommendation Q.1902.1, "Bearer Independent Call Control protocol (Capability Set 2): Functional description", July 2001. ITU-T Recommendation Q.2150.3, "Signalling Transport Converter On SCTP", to be published. 9 TALI 10 DUA 11 ASAP 12 ENRP 13 H.323 H.323 over SCTP October 2002. 14 Q.IPC/Q.2150.3 ITU-T Recommendation Q.2631.1 "IP Connection Control Signaling Protocol - Capability Set 1", to be published. ITU-T Recommendation Q.2150.3, "Signalling Transport Converter On SCTP", to be published. 15 SIMCO <draft-kiesel-midcom-simco-sctp-00.txt> 16 DDP Segment Chunk 17 DDP Stream Session Control 18 S1 Application Protocol (S1AP) 3GPP TS 23.401 3GPP TS 36.413 19 RUA 3GPP TS 25.467 3GPP TS 25.468 20 HNBAP 3GPP TS 25.467 3GPP TS 25.469 21 ForCES-HP 22 ForCES-MP 23 ForCES-LP 24 SBc-AP 3GPP TS 29.168 25 NBAP 3GPP TS 25.433 26 Unassigned 27 X2AP 3GPP TS 36.423 28 IRCP - Inter Router Capability Protocol 29 LCS-AP 3GPP TS 29.271 30 MPICH2 31 Service Area Broadcast Protocol (SABP) 3GPP TS 25.467 3GPP TS 25.419 32 Fractal Generator Protocol (FGP) 33 Ping Pong Protocol (PPP) 34 CalcApp Protocol (CALCAPP) 35 Scripting Service Protocol (SSP) 36 NetPerfMeter Protocol Control Channel (NPMP-CONTROL) 37 NetPerfMeter Protocol Data Channel (NPMP-DATA) 38 Echo (ECHO) 39 Discard (DISCARD) 40 Daytime (DAYTIME) 41 Character Generator (CHARGEN) 42 3GPP RNA Tonesi 3GPP TS 25.471 43 3GPP M2AP Tonesi 3GPP TS 36.442 3GPP TS 36.443 44 3GPP M3AP Tonesi 3GPP TS 36.442 3GPP TS 36.444 45 SSH over SCTP 46 Diameter in a SCTP DATA chunk 47 Diameter in a DTLS/SCTP DATA chunk 48 R14P. BER Encoded ASN.1 over SCTP 49 Generic Data Transfer (GDT) Protocol 50 WebRTC DCEP 51 WebRTC String 52 WebRTC Binary Partial (deprecated) 53 WebRTC Binary 54 WebRTC String Partial (deprecated) 55 3GPP PUA 3GPP TS 25.470 3GPP TS 25.467 56 WebRTC String Empty 57 WebRTC Binary Empty 58 3GPP XwAP 3GPP TS 36.462 59 3GPP Xw-Control Plane 3GPP TS 36.462 60 3GPP NG Application Protocol (NGAP) 3GPP TS 38.413 61 3GPP Xn Application Protocol (XnAP) 3GPP TS 38.423 62 3GPP F1 Application Protocol (F1 AP) 3GPP TS 38.473 63 HTTP/SCTP 64 3GPP E1 Application Protocol (E1AP) 3GPP TS 38.463 65 ELE2 Lawful Interception 66 3GPP NGAP over DTLS over SCTP 3GPP TS 38.413 67 3GPP XnAP over DTLS over SCTP 3GPP TS 38.423 68 3GPP F1AP over DTLS over SCTP 3GPP TS 38.473 69 3GPP E1AP over DTLS over SCTP 3GPP TS 38.463 70 E2-CP 71 O-RAN D2 72 E2-DU 73 3GPP W1AP 3GPP TS 37.473 74-4241 Unassigned 4242 DTLS Chunk Key-Management Messages 4243-4294967295 Unassigned Specification Required Unassigned 0 Reserved 1 SHA-1 2 Reserved 3 SHA-256 4-65535 Unassigned IETF Review 0 Unassigned 0x00000001 DDP 0x00000002-0xffffffff Unassigned Specification Required Michael Tuexen, Magnus Westerlund 0 Reserved 1 SCTP over DTLS 2-4294967295 Unassigned Damir Franusic mailto:damir.franusic&gmail.com 2021-08-13 Dario S Tonesi mailto:dario.tonesi&nsn.com 2014-01-03 Dongwook Kim mailto:dongwook.kim&etsi.org 2026-01-15 Josip Djuricic mailto:jd&release14.org 2012-06-08 Jun Hyuk Song mailto:junhyuk.song&samsung.com 2019-07-16 KIMBA DIT ADAMOU, Boubacar mailto:jinba&chinamobile.com 2015-11-17 Kimmo Kymalainen mailto:kimmo.kymalainen&etsi.org 2010-06-03 Lionel Morand mailto:lionel.morand&orange.com 2020-06-26 Luis Lopes mailto:llopes&qti.qualcomm.com 2017-04-20 Michael Tuexen mailto:tuexen&fh-muenster.de 2018-03-20 O-RAN Alliance https://www.o-ran.org 2019-07-16 Rajeev Koodli mailto:rkoodli&starentnetworks.com 2008-12-19 Randall Stewart mailto:rrs&lakerest.net 2010-04-13 Sebastian Kiesel mailto:kiesel&ikr.uni-stuttgart.de 2006-03-22 Thomas Dreibholz mailto:dreibh&simula.no 2025-10-07 Yang Xudong mailto:yangxudong&huawei.com 2019-05-24