Address tables
A prospective directory of ARPANET host and IMP addresses.
McKenzie, A.M., "Address tables", RFC 208, DOI 10.17487/RFC0208, August 1971, <https://www.rfc-editor.org/info/rfc208>.
@misc{rfc208,
series = {Request for Comments},
number = 208,
howpublished = {RFC 208},
publisher = {RFC Editor},
doi = {10.17487/RFC0208},
url = {https://www.rfc-editor.org/info/rfc208},
author = {A.M. McKenzie},
title = {{Address tables}},
pagetotal = 3,
year = 1971,
month = aug,
} RFC text
Contents
Network Working Group A. McKenzie
Request for Comments: 208 Bolt Beranek and Newman
NIC: 7181 9 August 1971
Categories: B.l, C.2
Updates: none
Obsoletes: none
ADDRESS TABLES
Attached is a copy of a revision to Appendix A of BBN Report No.
1822; the revised version of the Appendix is our first attempt to
make the list of sites attached to the ARPA Network prospective
rather than retrospective. We are adopting this approach because of
the large number of sites scheduled for attachment in the near
future, and because many Hosts apparently require a site's address to
be in some local table before their NCPs will permit communication
with the site. Therefore, we urge such Hosts to add the new sites to
their lists of addresses as soon as possible. Also, please note the
address change which will be made at BBN on exactly September first.
Incidentally, it seems to us that it is irrational for an NCP to
discard otherwise valid messages, simply because the sender's address
doesn't appear in a local table. Similarly, it seems almost as
irrational for an NCP to prevent a local user from trying to
communicate with a remote site, the address of which is known to the
user but not stored in the NCP's tables.
Report No. 1822 Bolt Beranek and Newman Inc.
APPENDIX A
IMP AND HOST SITE IDENTIFICATION
Bit 9-16 of the leader of most Host-to-IMP or IMP-to-Host messages
define a network address related to the message (these bits are not
meaningful for message types 1, 2, and 4). In a Host-to-IMP message
the network address identifies a particular Host to which the message
should be delivered. In an IMP-to-Host message the network address
identifies the Host from which the message originated.
A network address consists of six bits (bits 11-16 of the leader)
which specify an IMP number, preceded by two bits (bits 9-10 of the
leader) which specify the Host number of a particular Host connected
to that IMP. The table below gives the decimal values of IMP number,
Host number, and network address for each Host currently connected to
the ARPA Network or scheduled for connection in the near future.
Scheduled installation dates are also shown for Hosts not currently
connected; these dates, however, are subject to change without
notice.
IMP SITE HOST NETWORK SCHEDULED
NUMBER NAME NUMBER HOST ADDRESS INSTALLATION
------ ---- ------ ---- ------- ------------
1 UCLA 0 SIGMA-7 1
1 IBM 360/91 65
2 SRI 0 PDP-10 (NIC) 2
1 PDP-10 (Al) 66
3 UCSB 0 IBM 360/75 3
4 UTAH 0 PDP-lO 4
5 BBN 0 DDP-516 5 ) See Note 1
1 PDP-10 (A) 69 )
2 PDP-1O (B) 133
Note 1: Prior to September 1, 1971 the BBN PDP-1O (A) will be Host
number 0 (network address 5) and the BBN DDP-516 will be Host number
1 (network address 69). The address change is to be made during the
day on 9/1/71.
IMP SITE HOST NETWORK SCHEDULE
NUMBER NAME NUMBER HOST ADDRESS INSTALLATION
------ ---- ------ ---- ------- ------------
6 MIT 0 Honeywell 645 6
1 PDP-10 70
7 RAND O 360/65 7
1 PDP-1O 71
8 SDC O IBM 360/75 8
9 HARVARD O PDP-1O 9
1 PDP-1 73
2 PDP-11 137
10 LINCOLN O IBM 360/67 10
1 TX2 74
11 STANFORD O PDP-1O 11
12 ILLINOIS O PDP-11 12
13 CASE O PDP-1O 13
14 CARNEGIE O PDP-1O 14
15 PAOLI O B6500 15
16 NASA/AMES O IBM 360/67 16 8/3/71
2 TIP 144
17 MITRE 2 TIP 145 8/31/71
18 RADC O H 635/645 18 10/5/71
2 TIP 146
19 NBS O PDP-11 19 11/2/71
20 ETAC 2 TIP 148 11/30/71
21 TINKER O 418 III 21 1/4/71
22 McCLELLAN O 418 III 22 2/1/72
23 USC 0 IBM 360/44 23 2/29/72
2 TIP 151
24 GWC 2 TIP 152 3/14/72
25 NCAR O CDC 7600 25 3/28/72
2 TIP 153
30 BBN/TIP 2 TIP 158
ISO Plain Language
On this page
§1Why Publish a Prospective List
The document attaches a revised Appendix A of BBN Report 1822. It is the first attempt described in the RFC to make the site list prospective, including sites scheduled to connect in the near future.
The reason is that many hosts apparently require a site's address in a local table before their NCPs permit communication. The note urges those hosts to add new sites as soon as possible and announces a planned BBN address change on September 1.
The list includes sites expected to join, not only sites already connected. Hosts that need local address entries are asked to add the new ones early.
§2How the Address Is Formed
For most Host-to-IMP and IMP-to-Host messages, bits 9 through 16 of the message leader carry a network address. In a Host-to-IMP message, it identifies the destination host; in an IMP-to-Host message, it identifies the originating host.
The address combines two bits for a host number attached to an IMP with six bits for the IMP number. The table gives decimal IMP numbers, host numbers and network addresses, along with planned installation dates for hosts not yet connected.
A network address combines a host number with the number of the IMP it connects through. The table lists those numbers for current and planned hosts.
§3Address Tables and Message Handling
The note argues that an NCP should not discard an otherwise valid message only because the sender's address is absent from a local table. It makes a similar point about preventing a user from trying to contact a remote site whose address the user knows.
The RFC states this as the author's view; the address appendix itself provides the listed assignments and scheduled installations.
The author questions blocking a valid message just because a local address list does not contain its sender. The note also questions stopping users from trying an address they know.