                                                  Transmission Control Protocol (TCP) Option Numbers

   Last Updated
           2009-03-17

   This registry is also available in XML and plain text formats.

   Registries included below

     * TCP Option Kind Numbers
     * TCP Alternate Checksum Numbers

TCP Option Kind Numbers

   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.

   Registration Procedures
           IESG Approval or Standards Action

    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]
     7      6    Echo Reply (obsoleted by option 8)  [RFC1072]
     8      10   TSOPT - Time Stamp Option           [RFC1323]
     9      2    Partial Order Connection Permitted  [RFC1693]
     10     3    Partial Order Service Profile       [RFC1693]
     11          CC                                  [RFC1644]
     12          CC.NEW                              [RFC1644]
     13          CC.ECHO                             [RFC1644]
     14     3    TCP Alternate Checksum Request      [RFC1146]
     15     N    TCP Alternate Checksum Data         [RFC1146]
     16          Skeeter                             [Stev_Knowles]
     17          Bubba                               [Stev_Knowles]
     18     3    Trailer Checksum Option             [Subbu_Subramaniam][Monroe_Bridges]
     19     18   MD5 Signature Option                [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                 [RFC5482]
   29-252        Unassigned
    253     N    RFC3692-style Experiment 1 (*)      [RFC4727]
    254     N    RFC3692-style Experiment 2 (*)      [RFC4727]

TCP Alternate Checksum Numbers

   Reference
           [RFC1146]

   Registration Procedures
           Not defined

   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]

                                                                        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
