Fedora and fallback DNS servers [LWN.net]

Fedora and fallback DNS servers

Posted Feb 26, 2021 9:07 UTC (Fri) by intelfx (subscriber, #130118)
In reply to: Fedora and fallback DNS servers by pmb00cs
Parent article: Fedora and fallback DNS servers

> I find it very hard to believe there are swathes of users computer literate enough to either change the default OS on their machine, dual boot with linux, or buy/build a computer with no OS and install Linux, who are also completely incapable of troubleshooting non working DNS

There are lots of them.

People who find themselves using Linux for application-level reasons (computer scientists and CS students, for example) are literate enough to install and use Linux with varied degrees of success, but are not nearly as literate (or interested) in network administration or troubleshooting. Most of those probably never heard the term "DNS" (and do not wish to hear it, either).

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Fedora and fallback DNS servers

Posted Feb 26, 2021 9:31 UTC (Fri) by pmb00cs (subscriber, #135480) [Link] (14 responses)

And if the computer scientists and students are on a campus network they can report network problems to their university networking team.

I do contend however that they are not "non-technical" users. Computer Scientists, by the nature of their job are working on the bounds of what computers can do, and Computer Science Students are studying that subject. How does that put them in the "non-technical" group? They may not have heard of DNS (really? in the CS field there are academics who don't know how networking works to the point they've never heard of DNS? Because modern Computer Science has nothing at all to do with networking does it?) but they will be technical enough to find roughly where the problem is, and report it to the responsible party if that is not them.

It's been mentioned elsewhere in the comments, but I'll bring it up here as well. What about the OS's that are installed by default? Where there is a regulatory burden for the OEM to provide support to the users, and therefore an actual financial incentive to make their use as easy as possible for non-technical users. How many of thos have a fall back for broken DNS?
Windows: Nope
Android: Nope
MacOS: Nope
IOS: (I don't actually know, but I suspect not)
These Operating systems in use on BILLIONS of devices don't have DNS fall back, why? Because it simply isn't the genius idea it is being sold as. It either doesn't add value, or where it does add value it masks an issue, which is far more damaging than the value it offers in masking that issue.

Lets face it the only reason systemd-resolved has fall back DNS settings is because Lennart Poettering has probably had a DNS issue on a network that wasn't his own, and he is arrogant enough to believe that the rest of us are too stupid to fix that issue without his help, and he can't see how masking a DNS issue could come back to bite him. The rest of us however can extrapolate from our experiences, when we've had an issue masked from us it has come back to bite us, therefore masking a DNS issue will come back to bite us.

Lets not defend a poor decision by using arrogance to invoke "what about the people not as bright as us?" when those people either don't exist, or aren't as stupid as we want to think they are. We were all non-technical once, but we became technical by learning. I'm not suggesting that all Linux users are as technical as I, or that I am the most technical Linux user. What I am contending is that the least technical Linux user is at least partly technical, and must have reached a level of technical ability that would allow them to do basic diagnostics BEFORE they became a Linux user, because in this day and age that is what you need to do before you would recognise that Linux is even an option.

Fedora and fallback DNS servers

Posted Feb 26, 2021 11:28 UTC (Fri) by intelfx (subscriber, #130118) [Link] (1 responses)

> really? in the CS field there are academics who don't know how networking works to the point they've never heard of DNS? Because modern Computer Science has nothing at all to do with networking does it?

You probably intended a sarcastic meaning, but you are absolutely correct from first word to last.

(Source: first-hand experience.)

Fedora and fallback DNS servers

Posted Feb 26, 2021 11:35 UTC (Fri) by peniblec (subscriber, #111147) [Link]

Because modern Computer Science has nothing at all to do with networking does it?
You probably intended a sarcastic meaning, but you are absolutely correct from first word to last.

I'd say "modern" is superfluous; the "computer science is no more about computers than astronomy is about telescopes" aphorism is at least 30 years old.

Fedora and fallback DNS servers

Posted Feb 28, 2021 8:35 UTC (Sun) by jond (subscriber, #37669) [Link]

You were doing very well presenting your case right up to the ad-hominem attack on Poettering which undermines the whole thing.

Fedora and fallback DNS servers

Posted Mar 5, 2021 13:15 UTC (Fri) by jschrod (subscriber, #1646) [Link] (10 responses)

> in the CS field there are academics who don't know how networking works to the point they've never heard of DNS?

I hope that DNS is *not* taught in a CS course at any self-respecting university. There are more important things to teach, principles instead of specific technics.

> Because modern Computer Science has nothing at all to do with networking does it?

Yes. (I studied CS, and made my PhD in this field.) CS is about structures and how we manipulate them. Similar to mathematics, which, in academia, isn't about math (as you know it from school) either. Or, as an other poster wrote, astronomy is not the science of telescopes.

Fedora and fallback DNS servers

Posted Mar 8, 2021 13:54 UTC (Mon) by LtWorf (subscriber, #124958) [Link] (9 responses)

> I hope that DNS is *not* taught in a CS course at any self-respecting university.

Yes in network courses the teacher just goes "it's all magic. Never use tcpdump and never try to understand anything. Also never learn about flow control, error correction, 3 way ack."

Sounds me more like what would happen in the most terrible university.

Fedora and fallback DNS servers

Posted Mar 8, 2021 14:10 UTC (Mon) by farnz (subscriber, #17727) [Link] (1 responses)

Indeed; a Computer Science course (not Computer Engineering) wouldn't bother with tcpdump. Flow control, error correction and 3 way ack algorithms would probably be described and discussed, but not in terms of the details of how they're applied in the TCP/IP stack - you're looking at them as abstract theory.

Computer Engineering probably would cover tcpdump, the TCP handshake (actually a 4 way handshake, with two steps combined into one packet), flow control in TCP and on network links, ECC as used in real networks etc.

Fedora and fallback DNS servers

Posted Mar 9, 2021 3:56 UTC (Tue) by deater (subscriber, #11746) [Link]

as someone currently teaching a Computer Engineering "Network Engineering" course, you are right on all counts on what we cover. Also the time the Computer Science students took the class (due to a prof on sabbattical in their department) they struggled a bit because their classes tend not to cover low-level real world topics.

As an aside, the networking class is getting hard to teach. With DNS moving to be tunneled over https, with https being encrypted (instead of plaintext), and with HTTP3 being QUIC which is custom-protocol-tunnelled through UDP, the analyzing-tcpdump exercises are becoming more or less useless.

Fedora and fallback DNS servers

Posted Mar 9, 2021 19:25 UTC (Tue) by jschrod (subscriber, #1646) [Link] (6 responses)

> > I hope that DNS is *not* taught in a CS course at any self-respecting university.

Excuse me, but we seem to have *very* different opinions what a university course is.

> Yes in network courses the teacher just goes "it's all magic. Never use tcpdump and never try to understand anything. Also never learn about flow control, error correction, 3 way ack."

Yes, that's all important -- but for a high-school course. More specific, in my country (Germany) these topics are part of the computer science (Informatik) curriculum at high-school level. For advanced courses, which are preparations for studying a topic at college level, these topics are mandatory for the syllabus the teachers have to create.

I know that other countries distribute the curriculum differently. E.g., the US places these topics probably at the college level -- which starts earlier there and which often introduces topics like 2nd (or even 1st) foreign language that are considered high-school topics in my country. Even other countries teach such topics in special engineering schools that are decidedly not geared towards an academic education.

This is the heart of my argument about *university courses*.

The goal of a university course in *computer science* is an *academic education* in that field. I take technical knowledge about specific protocols, as cited by you, as a sensible precondition. At my university, people had the opportunity to take "tutorial classes" (without credit points) in advance of a university course to fill up or refill their knowledge holes on the high-school/college level.

To repeat that high-school education cannot be the task of a course that shall teach you about theory, research, and practice of networking at an academic level -- similar to an analysis course at university level which won't repeat the "curve discussion" that we did on high-school. (Well, at least my math courses at my university didn't do so. They did expect us to know this.)

To be more specific: I would demand for a network course at university level to give the students the ability to read and understand current research articles in reviewed academic journals like ACM TOIN (or the network specific ones in ACM TOCS), and to follow research papers in respective ACM and IEEE proceedings. It would expect them to give graduates enough knowledge to start their own research in that area if they do their master's or Ph.D. thesis there.
Afterwards, I would expect them to have a grasp of queing theory, know about some important concepts like "time in a network" coined by Leslie Lamport, maybe reason about issues like buffer bloat in a scientific instead of an empiric way.
Where else should the graduates get that level of education from?

So, no: I stand by my opinion that it is not the task of a university to teach *high-school topics* like DNS or TCP-as-a-protocol. This is the task of a school, maybe of a college, but not of a university.

(As the other persons who answered you before me have noted: for Computer Engineering that's a bit different. I specifially mentioned *computer science* courses in my post.)

Fedora and fallback DNS servers

Posted Mar 9, 2021 19:53 UTC (Tue) by Wol (subscriber, #4433) [Link]

> Even other countries teach such topics in special engineering schools that are decidedly not geared towards an academic education.

Unfortunately, here (in the UK) we've pretty much abolished all "schools that are decidedly not geared towards an academic education." They were called Polytechnics.

30 years on, I think we're finally realising that was a big, BIG, mistake. (And now we're making another - we're turning Universities into Polytechnics, and wondering why nobody has academic *skills* any more.)

Cheers,
Wol

Fedora and fallback DNS servers

Posted Mar 11, 2021 6:29 UTC (Thu) by LtWorf (subscriber, #124958) [Link] (4 responses)

> Yes, that's all important -- but for a high-school course

In italy you can sign up to any university course having done any high school. In fact most people signing up for computer science, typically will have gone to a "liceo scientifico" rather than a "tecnico industriale informatico" and will have a focus more on mathematics than network protocols.

No credit mathematics courses are offered to bring people up to speed on mathematics, but you are absolutely not expected to now the entire content of "Computer Networks by Andrew S. Tanenbaum" before you can even apply.

I can't really understand how learning about networks or computer architecture or operating systems makes it impossible to understand scientific papers. Does it make sense to talk about distributed algorithms without knowing how it all works and why a certain set of assumptions is made for the proof?

I also have no idea what you mean college vs university.

Is image manipulation computer science? Can it be mentioned that jpg saves more green information because camera sensors are built this way, because we see green better? Or is that out of topic and forbidden?

I guess you are limiting "computer science" to what you learnt in your university and are excluding anything else as not relevant.

Fedora and fallback DNS servers

Posted Mar 11, 2021 14:02 UTC (Thu) by farnz (subscriber, #17727) [Link] (3 responses)

The distinction between Computer Engineering (which is the application of Computer Science to real world problems) and Computer Science (which is all about the theory) is common in many countries. Some places do mix the two together, and call the resulting mixture Computer Science, but that is by no means the common outcome.

In Computer Engineering, you will absolutely have to deal with practical things like tcpdump, TCP handshake, DNS, Ethernet frame structure and more

In Computer Science, you're looking at algorithms and how computation can be done usefully with them. So, for example, you will make certain assumptions about a distributed world, and those assumptions will be backed either by some handwaving about how a Computer Engineer can build a real system that meets those assumptions or by referencing some work by a Computer Engineer that shows that these assumptions are valid given a system that has been built.

To give an example of how this separates out; a Computer Scientist will make some assumptions about how routers in a network could be made to work (messages passed to neighbouring routers, neighbours forward packets towards their destination, there is a time delay between sending a packet and its reception), and look at how you could guarantee that packets go through the network to their destination efficiently. If they pull in Dijkstra's SPF algorithm, they'll describe something that works a lot like OSPF, but without all the little practicalities that make OSPF work in real networks.

In contrast, a computer engineer will look at things like the reliability of multicast, practical packet formats, MTU limitations, and build you something that works like OSPF.

It sounds to me like you have been through a system that blends Computer Engineering with Computer Science, and calls it Computer Science; this does happen in many institutions, but is not the most common case.

Fedora and fallback DNS servers

Posted Mar 11, 2021 15:21 UTC (Thu) by pizza (subscriber, #46) [Link]

> In Computer Engineering, you will absolutely have to deal with practical things like tcpdump, TCP handshake, DNS, Ethernet frame structure and more

Where I went to college [1], CompE was a specialized form of Electrical Engineering, focusing more on digital circuits and the logical building blocks that go into computer hardware. In other words, the physical layer.

Their Computer Science program was originally an offshoot of Mathematics, focused on computational theory and algorithms, although you could get quite a lot of real-world practicalities in the various specializations and electives -- and I recall one course that specifically covered the design principles behind TCP/IP, DNS, and so forth.

> It sounds to me like you have been through a system that blends Computer Engineering with Computer Science, and calls it Computer Science; this does happen in many institutions, but is not the most common case.

"The common case" is clearly not as common as one would think...

[1] Georgia Institute of Technology, widely considered to be a tier-1 STEM school in the US

Fedora and fallback DNS servers

Posted Mar 11, 2021 16:47 UTC (Thu) by excors (subscriber, #95769) [Link] (1 responses)

> If they [a computer scientist] pull in Dijkstra's SPF algorithm, they'll describe something that works a lot like OSPF, but without all the little practicalities that make OSPF work in real networks.
>
> In contrast, a computer engineer will look at things like the reliability of multicast, practical packet formats, MTU limitations, and build you something that works like OSPF.

But also the computer engineer might not realise that some of the implementation details violate the assumptions made in the mathematical proofs of Dijkstra's algorithm, so in rare edge cases their implementation fails to find a correct routing solution, and they can't understand the research paper that explains the problem precisely with six pages of algebra.

I think that's a significant challenge for Computer Science as a field - there's often a lack of connection between theory and practice. CS isn't like pure maths which can often be considered valuable in its own right; it's more like theoretical physics in that it's only successful when it gets applied to the real world. It's fine if it takes decades of speculative theoretical work before finding an application, but there should be a reasonable expectation that it will eventually find one. An unimplementable computer science concept is like an untestable physics theory - it's not really CS/physics any more, it's just an inefficient way to do maths.

But a lot of CS in academia doesn't really understand real-world computer engineering, because it's had no exposure to environments outside a university, so it fails to identify real problems that need solving; and a lot of computer engineering doesn't understand or care much about academic CS, so it keeps discovering and inventing bad fixes for problems that *have* been solved properly.

It's good for people to specialise but I think it's important to have at least some people who are comfortable with both sides, to keep them connected and working productively on the same problems. There are many cases where that is happening - see e.g. decades of programming language research which was only implemented in niche languages, while real software was written in C, but that research is now being adopted by mainstream production-quality languages thanks to people working to bridge the gap - but I suspect it's far less common than it should be.

Fedora and fallback DNS servers

Posted Mar 11, 2021 21:03 UTC (Thu) by LtWorf (subscriber, #124958) [Link]

Where I did my master, they had different research groups for more applied and more theoretical stuff.

Anyway, turned out I knew 2 people doing their thesis in 2 different research groups and it was basically the same topic. Low power algorithms, if I remember. It was years ago.

Anyway, the 2 had not met each other and had no idea that in the same building there was another person working on the same project from a different angle.