IMP/Host and Host/IMP Protocol changes (RFC0687)

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D.C. Walden: AUTHOR

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...