RFC 91 (rfc91) - Page 2 of 12
Proposed User-User Protocol
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RFC 91 A Proposed User-User Protocol December 1970 1. The notion of a (logical) _record_ should be present, and the notion of a _message_ should be suppressed. (To a FORTRAN pro- grammer, that which is written using one WRITE statement with no accompanying FORMAT is a record; to an OS/360 machine language programmer, PUT writes a record). 2. It should be possible to so implement the protocol in HOST sys- tems and/or library routines that now existing user programs can access files anywhere in the Network without program modifica- tion. (Initially, at least, this ability must be restricted to HOST systems of the same type). 3. The protocol should be implementable (not necessarily imple- mented) in any HOST system at the SVC or UUO level. Specific knowledge of the characteristics of the other HOST involved should be unnecessary. It should be noted that the above imply that some user programs must be aware of the nature of the other HOST -- at least in each case where the second criterion fails. As we make progress in (or give up on) the cases where the failure now occurs, the burden of accommodat- ing system differences will shift toward implementation in protocols (i.e., the HOST systems) or, by default, in user programs. Quite clearly, any proposal initiated today should be suspect as to the extent to which it "solves" ultimate problems. How ambitious to be is strictly a matter of taste. At this stage, I prefer to try something which I believe can be used by all of us (and, hence, is worth doing), goes a reasonable distance towards solving our short- range problems, is easy to do, and offers hope of viability in the long range view. In the following, I intend to describe the proposal itself with, I hope, proper motivational arguments for its pieces. I will then sketch the specific implementation we at Harvard are making for the PDP-10 and describe how we intend to apply it in the specific case of storage of files on other PDP-10's in the Network. USER-USER PROTOCOL (PROPOSAL) The following protocol is intended to apply to the data bits in mes- sages between the end of the marking bits and the beginning of the padding bits. _The present IMP-IMP and HOST-HOST protocols are unaf- fected by this proposal_. The general principle is that each segment (this is not a technical term) of data is preceded by control information specifying its nature and extent. The basic scheme has been evolved from that used in the SOS buffering system (see the papers in JACM, April 1959 and especially that by O.R. Mock). Mealy
