Transmission Control Protocol (TCP) Parameters Last Updated 2013-06-14 This registry is also available in plain text. Registries included below * TCP Option Kind Numbers * TCP Alternate Checksum Numbers * Cryptographic Algorithms for TCP-AO Registration * MPTCP Option Subtypes * MPTCP Handshake Algorithms * TCP Experimental Option Experiment Identifiers (ExIDs) TCP Option Kind Numbers Registration Procedure(s) IESG Approval or Standards Action Reference [RFC2780] Note The Transmission Control Protocol (TCP) has provision for optional header fields identified by an option kind field. Options 0 and 1 are exactly one octet which is their kind field. All other options have their one octet kind field, followed by a one octet length field, followed by length-2 octets of option data. [*] It is only appropriate to use these values in explicitly- configured experiments; they MUST NOT be shipped as defaults in implementations. See [RFC3692] for details. [**] These values have been deployed in the Internet without proper IANA assignment. At some point, these numbers may be officially allocated for some new purpose. It is therefore strongly recommended that implementers migrate to mechanisms with IANA-assigned values to avoid potential issues with their systems or products at a later point. [***] This value has been deployed on the Internet in ways that are not compatible with the documented use in this IANA allocation. Kind Length Meaning Reference 0 - End of Option List [RFC793] 1 - No-Operation [RFC793] 2 4 Maximum Segment Size [RFC793] 3 3 WSOPT - Window Scale [RFC1323] 4 2 SACK Permitted [RFC2018] 5 N SACK [RFC2018] 6 6 Echo (obsoleted by option 8) [RFC1072][RFC6247] 7 6 Echo Reply (obsoleted by option 8) [RFC1072][RFC6247] 8 10 TSOPT - Time Stamp Option [RFC1323] 9 2 Partial Order Connection Permitted (obsolete) [RFC1693][RFC6247] 10 3 Partial Order Service Profile (obsolete) [RFC1693][RFC6247] 11 CC (obsolete) [RFC1644][RFC6247] 12 CC.NEW (obsolete) [RFC1644][RFC6247] 13 CC.ECHO (obsolete) [RFC1644][RFC6247] 14 3 TCP Alternate Checksum Request (obsolete) [RFC1146][RFC6247] 15 N TCP Alternate Checksum Data (obsolete) [RFC1146][RFC6247] 16 Skeeter [Stev_Knowles] 17 Bubba [Stev_Knowles] 18 3 Trailer Checksum Option [Subbu_Subramaniam][Monroe_Bridges] 19 18 MD5 Signature Option (obsoleted by option 29) [RFC2385] 20 SCPS Capabilities [Keith_Scott] 21 Selective Negative Acknowledgements [Keith_Scott] 22 Record Boundaries [Keith_Scott] 23 Corruption experienced [Keith_Scott] 24 SNAP [Vladimir_Sukonnik] 25 Unassigned (released 2000-12-18) 26 TCP Compression Filter [Steve_Bellovin] 27 8 Quick-Start Response [RFC4782] 28 4 User Timeout Option (also, other known unauthorized use) [***][1] [RFC5482] 29 TCP Authentication Option (TCP-AO) [RFC5925] 30 N Multipath TCP (MPTCP) [RFC6824] 31 Reserved (known unauthorized use without proper IANA assignment) [**] 32 Reserved (known unauthorized use without proper IANA assignment) [**] 33 Reserved (known unauthorized use without proper IANA assignment) [**] 34-75 Reserved 69 Reserved (known unauthorized use without proper IANA assignment) [**] 70 Reserved (known unauthorized use without proper IANA assignment) [**] 71-75 Reserved 76 Reserved (known unauthorized use without proper IANA assignment) [**] 77 Reserved (known unauthorized use without proper IANA assignment) [**] 78 Reserved (known unauthorized use without proper IANA assignment) [**] 79-252 Reserved 253 N RFC3692-style Experiment 1 (also improperly used for shipping products) [*] [RFC4727] 254 N RFC3692-style Experiment 2 (also improperly used for shipping products) [*] [RFC4727] TCP Alternate Checksum Numbers Registration Procedure(s) Not defined Reference [RFC1146] Number Description Reference 0 TCP Checksum [RFC1146] 1 8-bit Fletchers's algorithm [RFC1146] 2 16-bit Fletchers's algorithm [RFC1146] 3 Redundant Checksum Avoidance [J_Kay] Cryptographic Algorithms for TCP-AO Registration Registration Procedure(s) RFC Publication After Expert Review Reference [RFC5926] Algorithm Reference SHA1 [RFC5926] AES128 [RFC5926] MPTCP Option Subtypes Registration Procedure(s) Standards Action Reference [RFC6824] Value Symbol Name Reference 0x0 MP_CAPABLE Multipath Capable [RFC6824], Section 3.1 0x1 MP_JOIN Join Connection [RFC6824], Section 3.2 0x2 DSS Data Sequence Signal (Data ACK and Data Sequence Mapping) [RFC6824], Section 3.3 0x3 ADD_ADDR Add Address [RFC6824], Section 3.4.1 0x4 REMOVE_ADDR Remove Address [RFC6824], Section 3.4.2 0x5 MP_PRIO Change Subflow Priority [RFC6824], Section 3.3.8 0x6 MP_FAIL Fallback [RFC6824], Section 3.6 0x7 MP_FASTCLOSE Fast Close [RFC6824], Section 3.5 0x8-0xe Unassigned 0xf Reserved for Private Use [RFC6824] MPTCP Handshake Algorithms Registration Procedure(s) Standards Action Reference [RFC6824] Flag Bit Meaning Reference A Checksum required [RFC6824], Section 3.1 B Extensibility [RFC6824], Section 3.2 C-G Unassigned H HMAC-SHA1 [RFC6824], Section 3.2 TCP Experimental Option Experiment Identifiers (ExIDs) Registration Procedure(s) First Come First Served Reference [RFC-ietf-tcpm-experimental-options-06] Note IANA will record known duplicate uses. Registry is empty. People ID Name Contact URI Last Updated [J_Kay] J. Kay mailto:jkay&ucsd.edu 1994-09 [Keith_Scott] Keith Scott mailto:kscott&mitre.org 1999-02 [Monroe_Bridges] Monroe Bridges mailto:monroe&cup.hp.com 1994-09 [Stev_Knowles] Stev Knowles mailto:stev&ftp.com 1995-03 [Steve_Bellovin] Steve Bellovin mailto:smb&research.att.com 2000-03 [Subbu_Subramaniam] Subbu Subramaniam mailto:subbu&cup.hp.com 1994-09 [Vladimir_Sukonnik] Vladimir Sukonnik mailto:vladimir&sitaranetworks.com 1999-02 Footnote [1] [https://devcentral.f5.com/tech-tips/articles/accessing-tcp-options-from-irules]