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BBN's Comments on NWG/RFC #33 (RFC0047)

IP.com Disclosure Number: IPCOM000003616D
Original Publication Date: 1970-Apr-01
Included in the Prior Art Database: 2019-Feb-11
Document File: 4 page(s) / 5K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Postel: AUTHOR [+1]

Related Documents

10.17487/RFC0047: DOI

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 60% of the total text.

Network Working Group Request for Comments #47 J. Postel S. Crocker UCLA 20 April 70

BBN’s Comments on NWG/RFC #33

BBN has given us the attached comments on NWG/RFC 33, but wouldn’t publish them being relectant to embarrass us. Embarrassment notwith- standing, we found the comments particularly useful and decided to share them with our friends. Bill Crowther is the author.

[Page 1]

RFC 47 BBN’s Comments on NWG/RFC #33 April 1970

I found two substantial errors in the Host Protocol Paper, which was otherwise an excellent paper. Both concern a misunderstanding of the nature of the IMP as a communications device, and in particular the nature of buffering an IMP must do. The authors consider the network as a device into which one pushes a message which travels around some, waits in buffers for substantial lengths of times, and then emerges at the destination. In fact a better model would be that the message pops out again an instant after it is inserted. While it is true there is a delay, it is imposed by phone line hardware for the most part. The IMP buffering is minimal, and devoted to error control and momentary traffic surges.

Since we cannot force a Host to take a message, we have built an elab- orate RFNM mechanism to suspend new input until he does. This mech- anism is an imperfect attempt to solve a very hard communications problem. The desire is to regulate traffic in such a way that as the Host takes its message from the IMP the next message is arriving on the phone line, and no buffering occurs at all.

In fact we cannot achieve this, and therefore have included buffering to handle traffic surges. These buffers are useless for their intended purpose unless they are empty. Only empty buffers are available to soak up a traffic surge.

The two specific errors occur on pages 5 and 23. On page 5 the authors say "Implicit in this purpose is the assumption that a user does not use multiple links to achieve a wide band." In fact one of the primary purposes of links is to achieve a wider band.

[Page 2]

RFC 47 BBN’s Comments on NWG/RFC #33 April 1970

We wish to allow as much band width as possible. Our troubles occur not with wide band but with an imbalance of input and output. The authors have rightly noticed that multiple links subvert the RFNM mechanism, making our job harder, but have wrongly labeled the nature of the problem.

Again on page 5 "An even more basic assumption, of course, is that the network’s load comes from some users transmitting sequences of messages rather than many users transmitting single messages coincidentally." We are in great shape against single message users when their messages are randomly relate...

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