I love the way that geeky guy smugly rubs his hands together, leans back and chuckles when he say “We have our very own IMP. (Huh, huh huh, sigh.)” I would totally chuckle that way if I had my own IMP. -Don

On 16 Oct 2017, at 18:09, Clem Cole &lt;clemc(a)ccc.com&gt; wrote: Don't forget the cost of the IMP itself was just the beginning. The fees to 'TPC' for the 1/2 duplex 9600 serial lines in those days were very, very expensive. DARPA paid for them for each site in a large deal it had with AT&T. I don't remember where I saw it, but what sticks out in my mind for those days was that cost of a site (host) on the ARPAnet was approx $125K / year per host in an ARPA grant. Which really explains 'security.' In practice nobody was going to risk letting just anyone hack their system so much that it put the site at risk. Truth is we did not try to break in because we all had access, but if it you needed a $.5-2M PDP-10 to connect to the internet, a free IMP slot (each IMP supplied 4) and the leases on the wires. So it was just not practical to think like we do today, much less act that way. It was not so much security by obscurity, as security by practical economics. Moore's law, Ethernet and cheap processing power is what blow that up. On Mon, Oct 16, 2017 at 11:38 AM, Don Hopkins &lt;don(a)donhopkins.com <mailto:don@donhopkins.com>> wrote: I love the way that geeky guy smugly rubs his hands together, leans back and chuckles when he say “We have our very own IMP. (Huh, huh huh, sigh.)” I would totally chuckle that way if I had my own IMP. -Don My uncle worked at the German Space Operations Center, which had DATEX-P, so I asked a mailing list about how to connect with him, and got some interesting replies that give a glimpse of the topologies and costs of the time: -Don Date: 31-Oct-1986 0451 From: covert%covert.DEC(a)decwrl.dec.com (John R. Covert) To: don(a)brillig.umd.edu Subject: Re: datex-p Datex-P costs money to use. Go to any VMS system on Telenet running PSI, and send mail to PSI%26245815390037::USERNAME You'll have to find someone willing to spend a buck or two for every message you send. You had the breakdown of the address wrong: 2624 is for Germany (Germany leaves the 262 off within the country) 581 is for the town (the same as the telephone code for the major nearby town) 53900 is the site 37 is the subaddress No free service to X.25 networks, sorry. /john Date: Fri, 31 Oct 86 14:13:22 EST From: rick(a)seismo.css.gov (Rick Adams) To: don(a)brillig.umd.edu Subject: Re: datex-p There is nothing magic about datex-p. Its not a network anymore than C&P telephone is a network. You keep trying to make something special out of it. Think of datex-p as MCI or ATT or SPRINT. Its just a common carrier. For about $1500/month you could arrange a tymnet/telenet link at maryland for them to call up. It would them cost the orignator of the transmission $12/hour and about $.70 per kilocharacters to connect to you. —rick Date: Fri, 31 Oct 86 10:03 EST From: John C Klensin &lt;Klensin(a)mit-multics.arpa&gt; Subject: Re: datex-p To: Don Hopkins &lt;don(a)brillig.umd.edu&gt; This is going to get pretty complicated, and I'm at a disadvantage in not knowing what you know already. So, I apologize if some of the following is obvious. I'm going to try to anticipate questions and answer then as a possibly-efficient way of doing this. "... telnet to the states": Strictly speaking, no. X.25 protocols, not TCP/IP, and I think the Bundespost would have fits if someone started passing TCP/IP traffic over their network. Moreover, if anyone has a VMS VAX in the entire world that is capable of accepting an incoming X.25/X.29 call and then handling TCP/IP traffic over it, we'd love to know about it, and how they are doing it. But, I doubt it: VAX PSI could not be a more hostile environment to this sort of thing if they had designed it with that in mind, and one cannot just write and install X.29 software -- it has to be certified by the network vendors. GTE Telenet might do so, Tymnet might, but I haven't heard of either of them being asked. And you would also need to certify the outgoing TCP/IP over X.25 package at the far end, and the Deutschebundespost? Well, "never" somewhat understates the situation. How about using a datex-p connection to connect to a machine in the US as a remote user? Certainly feasible. This is what is called in the trade an X.3 -> X.25 -> X.3 or X.29 connection, should you need to know. All you need is a) a machine at this end with incoming Tymnet or Telenet access (or maybe a few other things, but I don't know). Some universities have them, some don't, some commercial firms have them, some don't, etc. The minimum charge for those connections is circa $10K per month, $5K to some educational sites, so they are not real common in places that have not discovered a large need. b) an account at that end, with Datex-P, that has international access authorization. That costs extra, incidentally. c) The machine address here (a long string of numbers, the first four of which identify the network). d) And, of course, an account on the machine here, since one will be logging into it. What can you do once you get here? Anything that the local user can do, no more, no less. Can files be transferred over the VAX/PSI (X.3) ->X.25->X.29 link? Yep. Either things like "go into an editor at the remote and pretend someone is typing very fast" or things like kermit work. The latter very slowly because of the long packet-acknowledgement delays. How about mail over that connection? Not unless you invent some protocols such as the ones MAILNET uses (this relies that you have a daemon at the far end that you can take over and that the remote system knows about) or cook something up yourself. You are basically logged into the remote machine and using yours transparently, or you are logged into you machine and not the remote. And how are these things tariffed? Ignoring the fact that the charges are for kilopackets and connect time, rather than connect time and distance, just like long-distance voice phone: Either originator pays or remote machine pays ("collect call") service is possible. Sites that are willing to accept collect calls essentially sign up in advance, making it more like an in-WATS service - metered, but invisible to the caller. The norm in the US is collect call service, although the major packet switched networks all support login and password services for users who need to have accounts and pay the charges themselves (presumably because they are dealing with remote sites who refuse "collect" incoming calls). Internationally, there are three separate sets of charges, each of which can be charged to either the originator or the receiver (at least in principle). Assuming that a call originates in Germany and is bound for Maryland... a) Kilopacket and connect time charges for connecting to Datex-P. This is the same charge that would be incurred if you were making a local connection in Germany. For moderate use, it averages about $3/connect hour, last I checked. Datex-P does not accept any "collect" traffic at all, so you have to pay then. b) Kilopacket and connect time charges for crossing from Datex-P into a network that serves the US (the "X.75 gateway"). Here, they get you through the nose. Again, since Datex-P does not accept "collect" traffic and the originating network has to be responsible for these charges, they get passed to the Datex-P account holder. c) Kilopacket and connect time charges for connecting to the remote machine in Maryland. These charges correspond to domestic rates (typically $5 - $9 per connect hour), and are typically charged to the Maryland site (Telenet or Tymnet send them a bill at the end of the month). If the Maryland site declines to accept the collect charge, they can be charged to the Datex-P account also, just like the voice phone. The other way works the same way except that, since Datex-P refuses any collect traffic, ALL charges are assessed to the account at the US end. It tends to be a bit cheaper to call from Europe to the US than vice versa (backwards from voice), but I have not reviewed the numbers since the dollar collapsed. If you can find a local GTE Telenet access number (don't know where you are, or I could look it up), dial them up, type MAIL when you see @, type INTL/ASSOCIATES when it asks for a user name, and give INTL as a password. Then track through their little menus until you find the Federal Republic of Germany -- it should give you information on tariffs, etc. (in case you wonder, those accessing instructions are public information and appear on the second page of GTE Telenet's give-away "US Access telephone numbers" brochure). that is probably about the end of my knowledge. good luck john

I love the knobs and intercom panels on the front of the IMP. I actually had my own IMP. BRL bought four IMPs and four TACs and set them up as our campus network early on. I think we were the largest single purchaser of the ACC LH/DH-11 interfaces. I had set up all the modems for the IMPs and as soon as the BBN guy would uncrate them and power them up I’d run around shoving the trunks and host connectors into them. By the end of the day I wrote my contact at BBN telling him our network was all up and running. I got a letter back explaining that it would not be possible for me to do that. This led to my new motto that I kept for a long time: I didn’t know it was impossible when I did it.