Assigned link numbers
The assigned link numbers for traffic on the ARPANET host-to-host protocol
Postel, J., "Assigned link numbers", RFC 604, DOI 10.17487/RFC0604, December 1973, <https://www.rfc-editor.org/info/rfc604>.
@misc{rfc604,
series = {Request for Comments},
number = 604,
howpublished = {RFC 604},
publisher = {RFC Editor},
doi = {10.17487/RFC0604},
url = {https://www.rfc-editor.org/info/rfc604},
author = {J. Postel},
title = {{Assigned link numbers}},
pagetotal = 2,
year = 1973,
month = dec,
} RFC text
Contents
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.
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 ]
ISO Plain Language
On this page
§1Purpose of Link Assignments
This announcement updates link-number information in the official host-to-host protocol. It replaces the earlier update in RFC 317 and assigns four previously reserved link numbers for experiments with an internetworking protocol.
The RFC says this is a minor modification that should not affect existing network programs or usage.
The document updates which link numbers are set aside for different purposes. It says the changes should not affect existing network programs or use.
§2Link Number Ranges
Link 0 is for host-to-host protocol control. Links 2–71 are available for connections. Links 155–158 are for internetworking experiments, 159–191 for measurements under the direction of UCLA's Network Measurement Center, and 192–195 for Message Switching Protocol experiments.
Links 196–255 are available for private experiments. Link 1 and links 72–154 are reserved for future developments and experiments and are not to be used at this time.
Each range has a stated purpose: control, regular connections, measurement, or experiments. Link 1 and links 72–154 are reserved rather than available for use.
§3Replacement of the Registry
The table in the RFC summarizes each link number range and its assignment. The listed ranges specify how the host-to-host protocol distinguishes control traffic and several kinds of data or experimental use.
RFC 604 is later obsoleted by RFC 739, according to the unit metadata.
This RFC records the assignments for its time. A later registry, RFC 739, replaced it.