RFC1からTCPが生まれるまでのBob Kahnの思考を辿る(3)

BBNを離れ、TCP/IPの元となる論文「A Protocol for Packet Network Intercommunication」を書き上げたBob Kahnだが、この当時の状況を、このように話している。

Oral-History:Robert Kahn - Engineering and Technology History Wiki

Actually, there was some real conflict inside of BBN before I left. That’s part of the reason that I chose to go to DARPA. It had to do, I think, with the way things were developing with Frank and his group. He was very interested in controlling everything that had to do with networking and kind of left me at loose ends.

KahnがBBNを去る頃、BBNの中でも衝突があったようだ。

We knew we needed a better protocol, something that involved some kind of an error detection and retransmission or correction scheme. We knew we needed to have a more robust—or at least I did, at that point—addressing mechanism. I had a pretty good idea of what we needed to do, but I didn’t know how to take that and actually figure out how to get it in the first machine. That’s why I asked Vint to work with me on this whole mission.

よりよいプロトコルが必要だということはわかっていたが、最初の装置に、そのプロトコルをどうやって入れるかわからなかったので、ARPAでホストコンピュータ側を見ていたVint Cerfに一緒に考えるよう頼んだ。

そのVint CerfもOral Historyで、当時を振り返っている。

Oral-History:Vinton Cerf - Engineering and Technology History Wiki

Well, I was on my way up to Stanford University, having finished my Ph.D. in March of ’72, and starting at Stanford in the fall. And so somehow or another I wound up being asked to lead this international network working group. I guess they assumed that assistant professors had an infinite amount of time to do these things. So I went to Stanford at the same time that Bob Kahn left BB&N and went to ARPA to run packet programs.

当時、UCLAのSteve CrockerがARPAでリーダーを務めていたが、卒業のためUCLAを離れてしまった。その頃、Vint CerfはPh.Dを終えていたが、Crockerが抜けた後の重責を担わされたくないのでBob KahnがBBNを去るタイミングでスタンフォードに戻ることにしたらしい。

それにしても、キーとなる人物が２人揃って立場を変えるのは大変そうだが、このことがARPAのプロトコルを見直すターニングポイントとなったのだろう。

What was of course ironic is that in this 1973 time period, Bob Metcalfe was busy inventing Ethernet over at Xerox PARC, and that was about two miles away from my office. People from Xerox PARC would come to the seminar and we would have debates and discussions.

さて、Vint Cerfの近所ではXeroxでBob Metcalfeがイーサネットを開発していた。

In the long run, however, they chose to keep their Xerox protocol proprietary, whereas Bob Kahn and I felt that we really needed TCP to be a very easily accessible design so that anyone could build an instance of TCP. We went through some four iterations of the TCP design, and in the last iterations, we split IP out from the TCP protocol.

Xeroxはイーサネットをプロプライエタリにしようと考えていたが、Bob KahnとVint CerfはTCPを誰でも使えるものにしようと考えていた。４度の繰り返しを経て、最終的にはTCPとIPを分離した。

TCP/IPが長寿のプロトコルとなっている理由のひとつがTCPとIPの分離だと思うが、Vint CerfのいたStanfordとBob MetcalfeがいたXerox PARCが近所だったことが影響しているというのもなんとも興味深い。