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Comments on the proposed Host/IMP Protocol changes (RFC0690)

IP.com Disclosure Number: IPCOM000003738D
Original Publication Date: 1975-Jun-06
Included in the Prior Art Database: 2000-Sep-13
Document File: 3 page(s) / 7K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Postel: AUTHOR

Abstract

This is a set of comments on Dave Walden's RFC 687 suggesting a set of changes to the host--imp protocol. Dave's points are reproduced here with my comments underneath.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 40% of the total text.

Network Working Group Jon Postel

RFC # 690 USC-ISI

NIC # 32699 June 6, 1975

Comments on the proposed Host/IMP Protocol Change

This is a set of comments on Dave Walden's RFC 687 suggesting a set of

changes to the host--imp protocol. Dave's points are reproduced here

with my comments underneath.

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.

The existing protocols set the host header at 40 bits so that taken

together with the leader the length was 72 bits; a nice boundary for

both 8 bit and 36 bit machines. This suggestion would result in a

prefix of 80 + 40 = 120 bits, not so nice (unless the host header is

extended to 64 bits for a total prefix of 144 bits).

2. Expanded Address Field. The address field will be expanded to 24

bit, 16 bits of IMP address and 8 bits of host address. This expansion

is more than adequate for any foreseeable ARPA Network growth.

Just a few years ago 256 seemed like a lot of hosts, perhaps, a

extensible scheme might be more appropriate. (I concede 16,777,216,

is big)

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.

This sound very useful, but if we every want to have longer messages

than now the field should be wider, say 16 bits.

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.

This sounds like a good extension.

5. Source Host Control of Packets per Message. The possibility will

exist for the source host to specify a message stream which will use a

given number of packets per multi-packet message (e.g. two packets per

message or fi...