Initial Connection Protocol Control Commands
A corrected listing of NCP commands for the Initial Connection Protocol.
Postel, J., "Initial Connection Protocol Control Commands", RFC 145, DOI 10.17487/RFC0145, May 1971, <https://www.rfc-editor.org/info/rfc145>.
@misc{rfc145,
series = {Request for Comments},
number = 145,
howpublished = {RFC 145},
publisher = {RFC Editor},
doi = {10.17487/RFC0145},
url = {https://www.rfc-editor.org/info/rfc145},
author = {J. Postel},
title = {{Initial Connection Protocol Control Commands}},
pagetotal = 2,
year = 1971,
month = may,
} RFC text
Network Working Group J. Postel
Request for Comments: 145 UCLA - NMC
NIC: 6739 4 May 1971
Updates: 123
Obsoletes: 127
Initial Connection Protocol Control Commands
The following is my interpretation of the exchange between NCP's
which would be necessary to carry out the Initial Connection Protocol
of RFC #123. (This note corrects an error pointed out by Eric
Harslem of RAND).
Server NCP User NCP
__________ ________
Listen for Connection L RTS, U, L, l
A
STR, L, U, 32 ALL, l , 1, 32
A
Send 32 bits of data
in 1 message on link l
A
(value is S) Receive 32 bits of data
from link l (value is S)
A
CLS, L, U CLS, U, L
STR, S+1, U+1, B STR, U+1, S, B
s u
RTS, S, U+1, l RTS, U, S+1, l
B C
wait for connection wait for connection
ALL, l , m , b ALL, l , m , b
B B B C C C
data sent to link l data sent on link l
C B
data received on link data received on link l
B C
l , l , and l , are links, m and m are messages allocations, b
A B C B C B
and b are bit allocations, and all other symbols are defined in
C
RFC #123.
[This RFC is also available in .PS and. PDF format.]
[ This RFC was put into machine readable form for entry ]
[ into the online RFC archives by Lorrie Shiota]
ISO Plain Language
On this page
§1A Corrected Initial-Connection Exchange
Jon Postel presents an interpretation of the Network Control Program (NCP) exchange needed to carry out the Initial Connection Protocol in RFC 123. He says this note corrects an error pointed out by Eric Harslem of RAND.
RFC 145's header says it obsoletes RFC 127.
This note corrects an earlier table of the NCP messages used to establish an initial connection.
§2The Command Sequence
The server listens on link L while the user sends RTS, U, L, l_A. The server replies with STR, L, U, 32; the user sends ALL, l_A, 1, 32. The server sends 32 bits in one message, and the user receives the value S.
Both NCPs then send CLS. They establish further links using STR and RTS commands that include the value S, wait for the connections, and send ALL commands for message and bit allocations. The table then shows data flowing on the new links.
The peers first establish a link to exchange 32 bits, then close it. They use the received value to establish further links for data.
§3Link and Allocation Notation
The symbols l_A, l_B, and l_C represent links; m_B and m_C represent message allocations; and b_B and b_C represent bit allocations. The remaining symbols are defined in RFC 123.
The small-letter symbols label links and their message or bit allocations. RFC 123 defines the other symbols.