Network Working Group
RFC # 604
NIC # 21186
Jon Postel
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.


    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.


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.


Link 1, and links 72-154 are reserved for future developments and experiments and currently are not to be used.


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


        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 ]