Official Host-Host Protocol Modification: Assigned Link Numbers
Assignments of link numbers for Message Switching Protocol and network measurement.
Postel, J., "Official Host-Host Protocol Modification: Assigned Link Numbers", RFC 317, DOI 10.17487/RFC0317, March 1972, <https://www.rfc-editor.org/info/rfc317>.
@misc{rfc317,
series = {Request for Comments},
number = 317,
howpublished = {RFC 317},
publisher = {RFC Editor},
doi = {10.17487/RFC0317},
url = {https://www.rfc-editor.org/info/rfc317},
author = {J. Postel},
title = {{Official Host-Host Protocol Modification: Assigned Link Numbers}},
pagetotal = 1,
year = 1972,
month = mar,
} RFC text
Network Working Group Jon Postel
Request for Comments: 317 UCLA-NMC
NIC: 9347 March 20, 1972
Official Host-Host Protocol Modification: Assigned Link Numbers
I. Links 192,193,194 and 195 (decimal) are assigned for use by the
Message Switching Protocol (MSP) experiment.
II. Links 159 through 190 (decimal) are assigned for network
measurement purposes. These links are to be used only under
the direction of the Network Measurement Center (NMC). Contact
Vint Cerf, (213) 825-2368 for additional information.
III. On page 28 of NIC 8246 the link assignment table should read:
LINK NUMBER ASSIGNMENT
0 Control Link
2-71 Available for Connection
1, 72-158 Reserved--not for current use
159-191 To be used only for measurement work
under the direction of the Network
Measurement Center at UCLA
192-195 To be used for the Message Switching
Protocol experiment
196-255 Available for private experimental use
[This RFC was put into machine readable form for entry]
[into the online RFC archives by H�l�ne Morin, Viag�nie 10/99]
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On this page
§1Link Number Allocation
Jon Postel at UCLA-NMC assigns link numbers in the Host-Host Protocol to support experimental work and network measurement. Link numbers are one way the protocol identifies different communication streams between hosts. The ARPANET's protocol design allocated 256 link numbers (0-255), and this RFC defines how they are to be used.
Three new assignments are made: links for the Message Switching Protocol experiment, links for network measurement under the UCLA Network Measurement Center, and corrected allocations for regular use.
Different experiments on the network need different numbered channels to talk on so they don't interfere with each other. Postel decides which numbers go to which projects.
§2Link Range Assignments
Link 0 is reserved as the control link. Links 2-71 are available for regular connections. Links 1 and 72-158 are reserved for future use. Links 159-191 are assigned for network measurement work directed by the UCLA Network Measurement Center. Links 192-195 are assigned for the Message Switching Protocol (MSP) experiment. Links 196-255 are available for private experimental use.
This allocation balances the needs of operational network communication with the requirements for measurement and experimental protocols being tested on the ARPANET.
Link 0 is for control, 2-71 for normal talking, 159-191 for measuring how the network works, 192-195 for a special experiment, and 196-255 for other experiments.
§3Purpose and Impact
By allocating specific ranges for measurement and experiments, this RFC allows the ARPANET team to study network performance and test new protocols without disrupting operational traffic. The 32-link range for measurement (159-191) was particularly important, as understanding network behavior required substantial instrumentation.
The assignment also corrects an earlier document (NIC 8246) that had listed the allocations incorrectly, ensuring all sites use the same definitions.
The measurement team could look at what was happening on the network using their assigned links. The Message Switching experiment had its own links too. Everyone using the same plan meant nothing got confused.