IMP/Host and Host/IMP Protocol changes (RFC0687)
Original Publication Date: 1975-Jun-02
Included in the Prior Art Database: 2000-Sep-13
Publishing Venue
Internet Society Requests For Comment (RFCs)
Related People
Abstract
This note sketches the design of an expansion to the IMP/host and host/IMP protocol which will include among other things the possibility of addressing hosts on more than 63 IMPs. Our intention in this expansion is to correct certain existing limits without fundamental changes in the philosophy of the IMP/host protocol; i.e., while many issues which would represent fundamental changes to the IMP/host protocol are presently under discussion in the world-wide packet-switching com unity, we are not able to undertake massive fundamental changes on a time scale compatible with the short term needs for network improvement (e.g., already there are almost 60 IMPs).
Network Working Group David C. Walden (WALDEN@BBN)
Request for Comments: 687 Jun 1975
NIC #32654
IMP/Host and Host/IMP Protocol Change
This note sketches the design of an expansion to the
IMP/host and host/IMP protocol which will include among other
things the possibility of addressing hosts on more than 63 IMPs.
Our intention in this expansion is to correct certain existing
limits without fundamental changes in the philosophy of the
IMP/host protocol; i.e., while many issues which would represent
fundamental changes to the IMP/host protocol are presently under
discussion in the world-wide packet-switching com unity, we are
not able to undertake massive fundamental changes on a time scale
compatible with the short term needs for network improvement
(e.g., already there are almost 60 IMPs).
The following paragraphs cover each of the major
characteristics of the expanded protocol. A knowledge of Section
3 of BBN Report 1822 is assumed. As is discussed below, the
expanded protocol is backwards compatible.
1. Expanded Leader Size. The leader will be expanded from two
to five 16-bit words. This will provide space for necessary
field expansions and additions.
2. Expanded Address Field. The address field will be expanded
to 24 bits, 16 bits of IMP address and 8 bits of host address.
This expansion is more than adequate for any foreseeable ARPA
Network growth.
3. New Message Length Field. A new field will be added which
will allow the source host to optionally specify the message
length (in bits) to the IMP subnetwork. The IMP subnetwork may
be able to use this information (when available) to better
utilize network buffer storage. The destination host may also be
able to use this information to better utilize its buffer
storage. This field will be 13 bits wide.
4. Expanded Handling Type Field. The handling type field which
now is used to distinguish between priority and non-priority
message streams, etc., will be expanded to eight bits. This
expanded field will provide for the possibility of a number of
parallel message streams having different handling
characteristics between pairs of hosts; e.g., priority,
non-priority, varying numbers of packets per message (see below),
unordered messages (i.e., the present type-3 messages), a message
stream requiring guaranteed capacity, etc. Note that only some
of these facilities will be available in the near term.
5. Source Host Control of Packets per Message. The possibility
will exist for the source host to specify a message stream which
-1-
will use a given number of packets per multi-pa...