TUHS June 2022

tuhs@tuhs.org

69 participants
32 discussions

by Warner Losh

Greetings, What's the canonical source for patches to 2.9BSD and 2.11BSD? I see we have 2.11BSD patch 469 dated last month in the archive. Where does it come from? Has anybody climbed the hill to import all the patches into a git repo? I've found some mirrors, but moe.2bsd.org has been down for me for ages... How does Warren keep things up to date? I also have a (maybe faulty) memory of a similar series of patches to 2.9BSD because it was the last BSD to support non-split I&D space machines. yet a quick google search turns up nothing other than a set of patches dated August 1985 (also in our archive) and some changes for variants of hardware (pro, mscp). Is that it? Warner

2 years

"9 skills our grandkids won't have" - Is this a TUHS topic?

by steve jenkin

What are the 1970’s & 1980’s Computing / IT skills “our grandkids won’t have”? Whistling into a telephone while the modem is attached, because your keyboard has a stuck key - something I absolutely don’t miss. Having a computer in a grimy wharehouse with 400 days of uptime & wondering how a reboot might go? steve j ========= 9 Skills Our Grandkids Will Never Have <https://blog.myheritage.com/2022/06/9-skills-our-grandkids-will-never-have/> 1: Using record players, audio cassettes, and VCRs 2: Using analog phones [ or an Analog Clock ] 3. Writing letters by hand and mailing them 4. Reading and writing in cursive 5. Using manual research methods [ this is a Genealogy site ] 6. Preparing food the old-fashioned way 7. Creating and mending clothing 8. Building furniture from scratch 9. Speaking the languages of their ancestors -- Steve Jenkin, IT Systems and Design 0412 786 915 (+61 412 786 915) PO Box 38, Kippax ACT 2615, AUSTRALIA mailto:sjenkin@canb.auug.org.au http://members.tip.net.au/~sjenkin

2 years, 10 months

Research Datakit notes

by Paul Ruizendaal

Wanted to post my notes as plain text, but the bullets / sub-bullets get lost. Here is a 2 page PDF with my notes on Research Datakit: https://www.jslite.net/notes/rdk.pdf The main takeaway is that connection build-up and tear-down is considerably more expensive than with TCP. The first cost is in the network, which builds up a dedicated path for each connection. Bandwidth is not allocated/reserved, but a path is and routing information is set up at each hop. The other cost is in the relatively verbose switch-host communication in this phase. This compares to the 3 packets exchanged at the hosts’ driver level to set up a TCP connection, with no permanent resources consumed in the network. In compensation, the cost to use a connection is considerably lower: the routing is known and the host-host link protocol (“URP") can be light-weight, as the network guarantees in-order delivery without duplicates but packets may be corrupted or lost (i.e. as if the connection is a phone line with a modem). No need to deal with packet fragmentation, stream reassembly and congestion storms as in the TCP of the early 80’s. Doing UDP traffic to a fixed remote host is easily mapped to using URP with no error correction and no flow control. Doing UDP where the remote host is different all the time is not practical on a Datakit network (i.e. a virtual circuit would be set up anyway). A secondary takeaway is that Research Datakit eventually settled on a three-level ascii namespace: “area/trunk/switch”. On each switch, the hosts would be known by name, and each connection request had a service name as parameter. In an alternate reality we would maybe have used “ca/stclara/mtnview!google!www” to do a search.

2 years, 10 months

Re: Research Datakit notes

by jnc＠mercury.lcs.mit.edu

> From: Rob Pike > having the switch do some of the call validation and even maybe > authentication (I'm not sure...) sounds like it takes load off the host. I don't have enough information to express a judgement in this particular case, but I can say a few things about how one would go about analyzing questions of 'where should I put function [X]; in the host, or in the 'network' (which almost inevitably means 'in the switches')'. It seems to me that one has to examine three points: - What is the 'cost' to actually _do_ the thing (which might be in transmission usage, or computing power, or memory, or delay), in each alternative; these costs obviously generally cannot be amortized across multiple similar transactions. - What is the 'cost' of providing the _mechanism_ to do the thing, in each alternative. This comes in three parts. The first is the engineering cost of _designing_ the thing, in detail; this obviously is amortized across muiple instances. The second is _producing_ the mechanism, in the places where it is needed (for mechanisms in software, this cost is essentially zero, unless it needs a lot of memory/computes/etc); this is not amortized across many. The third is harder to measure: it's complexity. This is probably a book by itself, but it has costs that are hard to quantify, and are also very disparate: e.g. more complex designs are more likely to have unforseen bugs, which is very different from the 'cost' that more complex designs are probaly harder to evolve for new uses. So far I haven't said anything that isn't applicable across a broad range of information sytems. The last influence on where one puts functions is much more common in communication systems: the Saltzer/Clark/Reed 'End-to-end Arguments in System Design' questions. If one _has_ to put a function in the host to get 'acceptable' performace of that function, the operation/implementation/design cost implications are irrelevant: one has to grit one's teeth and bear them. This may then feed back to design questions in the other areas. E.g. the Version 2 ring at MIT deliberately left out hardware packet checksums - because it was mostly intended for use with TCP/IP traffic, which provided a pseudo-End-to-End checksum, so the per-unit hardware costs didn't buy enough to be worth the costs of a hardware CRC. (Which was the right call; I don't recall the lack of a hardware checksum ever causing a problem.) And then there's the 'techology is a moving target' point: something that might be unacceptably expensive (in computing cost) in year X might be fine in year X+10, when we're lighting our cigars with unneeded computing power. So when one is designing a communication system with a likely lifetime in many decades, one tends to bias one's judgement toward things like End-to-End analysis - because those factors will be forever. Sorry if I haven't offered any answer to your initial query: "having the switch do some of the call validation ... sounds like it takes load off the host", but as I have tried to explain, these 'where should one do [X]' questions are very complicated, and one would need a lot more detail before one could give a good answer. But, in general, "tak[ing] load off the host" doesn't seem to rate highly as a goal these days... :-) :-( Noel

2 years, 10 months

Re: Research Datakit notes

by jnc＠mercury.lcs.mit.edu

> From: Paul Ruizendaal > Will read those RFC's, though -- thank you for pointing them out. Oh, I wouldn't bother - unless you are really into routing (i.e. path selection). RFC-1992 in particular; it's got my name on it, but it was mostly written by Martha and Isidro, and I'm not entirely happy with it. E.g. CSC mode and CSS mode (roughly, strict source route and loose source route); I wasn't really sold on them, but I was too tired to argue about it. Nimrod was complicated enough without adding extra bells and whistles - and indeed, LSR and SSR are basically unused to this day in the Internet (at least, at the internet layer; MPLS does provide the ability to specify paths, which I gather is used to some degree). I guess it's an OK overview of the architecture, though. RFC-1753 is not the best overview, but it has interesting bits. E.g. 2.2 Packet Format Fields, Option 2: "The packet contains a stack of flow-ids, with the current one on the top." If this reminds you of MPLS, it should! (One can think of MPLS as Nimrod's packet-carrying subsystem, in some ways.) I guess I should mention that Nimrod covers more stuff - a lot more - than just path selection. That's because I felt that the architecture embodied in IPv4 was missing lots of things which one would need to do the internet layer 'right' in a global-scale Internet (e.g. variable length 'addresses' - for which we were forced to invent the term 'locator' because many nitwits in the IETF couldn't wrap their minds around 'addresses' which weren't in every packet header). And separation of location and identity; and the introduction of traffic aggregates as first-class objects at the internet layer. Etc, etc, etc. Nimrod's main focus was really on i) providing a path-selection system which allowed things like letting users have more input to selecting the path their traffic took (just as when one gets into a car, one gets to pick the path one's going to use), and ii) controlling the overhead of the routing. Of course, on the latter point, in the real world, people just threw resources (memory, computing power, bandwidth) at the problem. I'm kind of blown away< that there are almost 1 million routes in the DFZ these days. Boiling frogs... Noel

2 years, 10 months

Clem's Law.

by steve jenkin

I thought this comment was very good. I went looking for “Clem’s Law” (presume Clem Cole) and struck out. Any hints anyone can suggest or history on the comment? steve j ========== Larry McVoy wrote Fri Sep 17 10:44:25 AEST 2021 <https://minnie.tuhs.org/pipermail/tuhs/2021-September/024424.html> Plan 9 is very cool but I am channeling my inner Clem, Plan 9 didn't meet Clem's law. It was never compelling enough to make the masses love it. Linux was good enough. ========== -- Steve Jenkin, IT Systems and Design 0412 786 915 (+61 412 786 915) PO Box 38, Kippax ACT 2615, AUSTRALIA mailto:sjenkin@canb.auug.org.au http://members.tip.net.au/~sjenkin

2 years, 10 months

Re: Research Datakit notes

by jnc＠mercury.lcs.mit.edu

Just as the topic of TUHS isn't 'how _I_ could/would build a _better_ OS', but 'history of the OS that was _actually built_' (something that many posters here seem to lose track of, to the my great irritation), so too the topic isn't 'how to build a better network' - or actually, anything network-centric. I'll make a few comments on a couple of things, though. > From: steve jenkin > packet switching won over Virtual Circuits in the now distant past but > in small, local and un-congested networks without reliability > constraints, any solution can look good. ... Packet switching > hasn't scaled well to Global size, at least IMHO. The internetworking architecture, circa 1978, has not scaled as well as would have been optimal, for a number of reasons, among them: - pure scaling effects (e.g. algorithms won't scale up; subsystems which handle several different needs will often need to be separated out at a larger scale; etc) - inherent lack of hindsight (unknown unknowns, to use Rumsfeld's phrase; some things you only learn in hindsight) - insufficiently detailed knowledge of complete requirements for a global-scale network (including O+M, eventual business model, etc) - limited personnel resources at the time (some things we _knew_ were going to be a problem we had to ignore because we didn't have people to throw at the problem, then and there) - rapid technological innovation (and nobody's crystal ball is 100% perfect) It has been possible to fix some aspects of the ca. 1978 system - e.g. the addition of DNS, which I think has worked _reasonably_ well - but in other areas, changes weren't really adequate, often because they were constrained by things like upward compatibility requirements (e.g. BGP, which, among numerous other issues, had to live with existing IP addressing). Having said all that, I think your assertion that virtual circuits would have worked better in a global-scale network is questionable. The whole point of networks which use unreliable datagrams as a fundamental building block is that by moving a lot of functionality into the edge nodes, it makes the switches a lot simpler. Contemporary core routers may be complex - but they would be much worse if the network used virtual circuits. Something I suspect you may be unaware of is that most of the people who devised the unreliable datagram approach of the internetworking architecture _had experience with an actual moderately-sized, operational virtual circuit network_ - the ARPANET. (Yes, it was basically a VC network. Look at things like RFNMs, links {the specific ARPANET mechanism referred to by this term, not the general concept}, etc.) So they _knew_ what a VC network would involve. So, think about the 'core routers' in a network which used VC's. I guess a typical core router tese days uses a couple of OC768 links. Assume an average packet size of 100 bytes (probably roughly accurate, with the bimodal distribution between data and acks). With 4 OC768's, that's 4*38.5G/800 = ~155M packets/second. I'm not sure of the average TCP connection length in packets these days, but assume it's 100 packets or so (that's a 100KB Web object). That's still roughly _1 million cicuit setups per second_. If the answer is 'oh, we'll use aggregation so core routers don't see individual connections - or their setup/tear-down' - well, the same can be done with a datagram system; that's what MPLS does. Work through the details - VCs were not preferred, for good reasons. > Ethernet only became a viable LAN technology with advent of Twisted > pair: point to point + Switches. It's really irritating that a lot of things labelled 'Ethernet' these days _aren't_ _real_ Ethernet (i.e. a common broadcast bus allocated via CSMA-CD). They use the same _packet format_ as Ethernet (especially the 48-bit globally-unique address, which can usefully be blown into things at manufacture time), but it's not Ethernet. In some cases, they also retain the host interface<->network physical interface - but the thing on the other side of the interface is totally different (such as the hub-based systems commmon now - as you indicate, it's a bunch of small datagram packet switches plugged together with point-point links). Interfaces are forever; like the screw in light-bulb. These days, it's likely an LED bulb on one side, powered by a reactor on the other - two technologies which were unforseen (and unforseeable) when the interface was defined, well over 100 years ago. Noel

2 years, 10 months

Re: forgotten versions

by Paul Ruizendaal

On Tue, Jun 21, 2022 at 05:56:02PM -0600, Jacob Moody wrote: > I recently stumbled across the existence of datakit > when going through the plan9foundation source archives. > Would be curious to hear more about its involvement > with plan9. There are at least 2 versions of Datakit. I my current understanding there are “Datakit” which is the research version, and “Datakit II” which seems to be the version that was broadly deployed into the AT&T network in the late 80’s -- but very likely the story is more complicated than that. Plan9 is contemporaneous with Datakit II. In short, Sandy Fraser developed the “Spider” network in 1970-1974 and this was actively used with early Unix (at least V4, maybe earlier). Sandy was dissatisfied with Spider and used its learnings to start again. The key ideas seem to have gelled together around 1977 with the first switches being available in 1979 or so. The first deployment into the Bell system was around 1982 (initially connecting a handful of Bell sites). In 1979/1980 there were two Datakit switches, one in the office of Greg Chesson who was writing the first iteration of its control software, and one in the office/lab of Gottfried Luderer et al., who used it to develop a distributed Unix. Datakit at this time is well described in two papers that the ACM recently moved from behind its paywall: https://dl.acm.org/doi/pdf/10.1145/1013879.802670 (mostly about 1980 Datakit) https://dl.acm.org/doi/pdf/10.1145/800216.806604 (mostly about distributed Unix) The Chesson control software was replaced by new code written by Lee McMahon around 1981 (note: this is still Datakit 1). The Datakit driver code in V8 is designed to work with this revised Datakit. Three aspects of Datakit show through in the design the V8-V10 networking code: - a separation in control words and data words (this e.g. comes back in ‘streams') - it works with virtual circuits; a connection is expensive to set up (‘dial’), but cheap to use - it does not guarantee reliable packet delivery, but it does guarantee in-order delivery Probably you will see echoes of this in early Plan9 network code, but I have not studied that.

2 years, 10 months

Re: Research Datakit notes

by jnc＠mercury.lcs.mit.edu

> From: Paul Ruizendaal > it would seem to me that Sandy had figured out a core problem some 30 > years before the TCP/IP world would come up with a similar solution. I > would not even be surprised if I learned that modern telco routers > transparantly set up virtual circuits for tcp traffic. To fully explore this topic would take a book, which I don't have the energy to write, and nobody would bother to read, but... Anyway, I'm not upon the latest and greatest high-speed routers: I saw some stuff from one major vendor under NDA about a decade ago, but that's my most recent - but at that point there was nothing that looked even _vaguely_ like virtual circuits. (The stuff Craig was alluding to was just about connectivity for getting bitts from _interface_ to _interface_ - if you don't have a giant crossbar - which is going to require buffering on each input anyway - how exactly do you get bits from board A to board Q - a single shared bus isn't going to do it...) A problem with anything like VC's in core switches is the growth of per-VC state - a major high-speed node will have packets from _millions_ of TCP connections flowing through it at any time. In the late-80's/early-90's - well over 30 years ago - I came up with an advanced routing architecture called Nimrod (see RFC-1992, "The Nimrod Routing Architecture"; RFC-1753 may be of interest too); it had things called 'flows' which were half way between pure datagrams (i.e. no setup - you just stick the right destination address in the header and send it off) and VCs (read the RFCs if you want to kow why), and it went to a lot of trouble to allow flow aggregation in traffic going to core switches _precisely_ to limit the growth of state in core switches, which would have traffic from millions of connections going through them. I have barely begun to even scratch the surface, here. Noel

2 years, 10 months

Early Unix Growth: Number of “Installations” or Licences?

by steve jenkin

I’ve been wondering about the growth of Unix and if there’s any good data available. There’s the Early Unix Epoch, which probably ends with the Unix Support Group assuming the distribution role, plus providing / distributing their version of the code. Later there’s commercial Unix: System III and System V, I guess. BSD, until the lawsuit was resolved, required a Source code license, but their installation count is important in pre-Commercial Unix. Large licensees like SUN, HP & IBM (AIX) may not have published license counts for their versions - but then, were their derivatives “Unix” or something else? Warner Loch’s paper has data to around 1978 [below]. I’ve no idea where to find data for USG issued licences, or if the number of binary & source licences were ever reported in the Commercial Era by AT&T. I’ll not be the first person who’s gone down this road, but my Search Fu isn’t good enough to find them. Wondering if anyone on the list can point me at resources, even a bunch of annual reports. I don’t mind manually pulling out the data I’m interested in. But why reinvent the wheel if the work is already done? steve =============== numbers extracted from Warner Loch’s paper. <https://papers.freebsd.org/2020/FOSDEM/losh-Hidden_early_history_of_Unix.fi…> 2nd Edn June 1972 10 installations 3rd Edn February 1973 16 4th Edn November 1973 >20, or 25 July 74 CACM paper "Unix Time Sharing System” after which external interest exploded 6th Edn 1975 ??? 7th Edn March 1978 600+, >300 inside Bell System, "even more have been licensed to outside users” =============== -- Steve Jenkin, 0412 786 915 (+61 412 786 915) PO Box 38, Kippax ACT 2615, AUSTRALIA mailto:sjenkin@canb.auug.org.au http://members.tip.net.au/~sjenkin

2 years, 10 months

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TUHS June 2022