Network Working Group                                   Jon Postel
RFC # 604                                               MITRE
NIC # 21186                                             26 December 1973
                         Assigned Link Numbers
This announcement modifies the official host-to-host protocol, and
updates the defining documents [NIC 8246, NIC 9347].  Please note that
the information on page 28 of "Host/Host Protocol for the ARPA Network"
about link number assignments is updated by this note, and that a
previous update [RFC 317, NIC 9347] is completely replaced.  The
modification is minor and should have no effect on existing network
programs or usage.  Four of the reserved link numbers are hereby
assigned for experimental use in the testing of an internetworking
protocol defined by Kahn and Cerf.
Description:
    Control Link
        Link 0 is assigned for use as the host-to-host protocol control
        link.
    Data Links
        Links 2-71 are available for use in connections as provided by
        the host-to-host protocol.
    Internetworking Protocol
        Links 155-158 are to be used for experiments with the
        Internetworking Protocol.
    Measurements
        Links 159-191 are assigned for use in measurements under the
        direction of the Network Measurement Center at UCLA.
    Message Switching
        Links 192-195 are to be used for experiments with the Message
        Switching Protocol.
    Private Experiments
        Links 196-255 are available for private experimental use.
Postel                                                          [Page 1]

RFC 604                  Assigned Link Numbers             December 1973
    Reserved
        Link 1, and links 72-154 are reserved for future developments
        and experiments and currently are not to be used.
Table:
        Link Number              Assignment
            0                    Control Link
            1                    Reserved
           2-71                  Connections
          72-154                 Reserved
         155-158                 Internetworking Protocol
         159-191                 Measurements
         192-195                 Message Switching Protocol
         196-255                 Experimental
References:
        Host-to-host Protocol           NIC 8246
        Internetworking Protocol        NIC 18764
        Message Switching Protocol      NIC 9926
       [ This RFC was put into machine readable form for entry ]
       [ into the online RFC archives by Alex McKenzie with    ]
       [ support from GTE, formerly BBN Corp.            10/99 ]
Postel                                                          [Page 2]