@SystemsAppr@discuss.systems

Systems Approach @SystemsAppr@discuss.systems

· 2d ago

On Friday, we finished up the manuscript for the 7th edition of Computer Networks: a Systems Approach and sent it to the publisher. While sending the files to the publisher is something of a milestone, the work is never finished, because we continue to collect improvements and bugfixes from the community as we run this book as an open source project. The latest edition is the biggest refactoring of the book that we have done since our first edition came out in 1996, reflecting the changes in our field and in the way students and educators are approaching it. In this week's newsletter, Larry has written about some of the changes in how we present material, particularly in how have tried to teach students about the interconnectedness of topics that don't sit neatly in the old layered model. https://systemsapproach.org/2026/10/05/everything-is-connected/ 🧵 1/n

Systems Approach

Everything is Connected - Systems Approach

We use extensive cross-references between chapters to help students build a mental model of networking. This contrasts with layering

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Systems Approach @SystemsAppr@discuss.systems

· 2w ago

Replying to

First up, the Navier-Stokes equation controversy. Terrence Tao has written extensively and eloquently on this, and we're not going to improve on the statement he co-authored with 25 Fields Medal winners: https://terrytao.wordpress.com/2026/09/11/a-severe-misalignment-of-ai-in-mathematics/ Just as using an LLM to do homework doesn’t help a student learn the topic at hand, nor is the solution of maths problems using LLMs necessarily a useful endeavor. To quote the joint statement: "In recent months, the success of AI in solving major mathematical problems has made headlines even outside mathematical circles. But solving problems is only a tool and proxy for achieving the primary goal of conceptual understanding and insight. Forgetting this in the world of AI may turn the tool against the primary goal." 2/n

What's new

A Severe Misalignment of AI in Mathematics

I am proud to be among the list of 25 initial signatories — all Fields Medallists — to the declaration below, which grew out of discussions between ourselves over the last week. We have…

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Systems Approach @SystemsAppr@discuss.systems

· 2mo ago

A few weeks ago we published the draft of Computer Networks: A Systems Approach (7th edition) and asked for feedback. One of the most helpful responses was from a networking practitioner who commented on our treatment of network operations. His point was that we had focused too much on the perspective of large cloud operators and not enough on the "real world" of traditional network operators. In this week's newsletter we wrote about the difference, which has a lot to do with how much you can make the network conform to a "clean" model versus needing to deal with the messiness of heterogeneous systems in the real world. https://systemsapproach.org/2026/07/27/reality-based-network-operations/ 🧵 1/n

Systems Approach

Reality-based Network Operations - Systems Approach

A challenge in covering network operations is the tension between covering the way we want the world to be versus the way it is.

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Systems Approach @SystemsAppr@discuss.systems

· 4mo ago

We occasionally hear that writing textbooks is no longer worthwhile when everyone can get their information from large language models (LLMs). We engage with this viewpoint rather than just writing books as we have for the last 30 years. In this post we lay out what we think our value proposition is: a big-picture view and systems thinking. https://systemsapproach.org/2026/06/01/textbooks-in-tokenland/

Systems Approach

Textbooks in Tokenland - Systems Approach

Teaching judgement and providing guidance on how to think about complex systems are areas where we think we still have the edge over LLMs.

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Our latest piece on QUIC has appeared in The Register:
https://www.theregister.com/2026/04/16/quic_explained/?td=rt-3a

theregister.com

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Seems like a good day to revisit our "DNSSEC is a failed experiment" post: https://systemsapproach.org/2025/07/14/does-dns-security-matter/

Systems Approach

Does DNS Security Matter? - Systems Approach

DNSSEC assures a client that it is talking to the IP address corresponding to the domain name that it requested

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Replying to

Here are two images by the two authors representing different views of the naming issues: 2/n

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Replying to

This exposed two issues: first, is there a difference between an L3 switch and a router? And second, when modern switches can be configured to forward on either the Ethernet header or the IP header, how do we best talk about them? On the first question, we ultimately decided to let context be the determining factor. Even while there is no technical difference between an L3 switch and a router, the most common usage in the datacenter context favors "switch". For ISPs, router is still the preferred term. The configurability of modern devices, especially those based on programmable forwarding silicon, means we have to be clear in our discussions to separate what a device is capable of doing versus what it is configured to do. 3/n

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Last week I was working on yet another chapter for our new edition, on the topic of Virtual Networks. Having spent much of my career focused on various flavors of virtualization, I decided to pick up that topic and run with it. Virtual networking has at least one thing in common with our last post: debate about terminology.

https://systemsapproach.org/2026/05/04/literally-virtualized/

Systems Approach

Literally Virtualized - Systems Approach

Virtual networks provide a range of different abstractions, from VLANs through VPNs to fully-fledged virtual networks

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Replying to

@fivetonsflax@tilde.zone @ricci@discuss.systems We gave some thought to this approach but found it gets very hard to explain something like ARP or selecting the next hop in IP forwarding if you have reduced every forwarding device to a switch. It really matters whether it has an awareness of IP once you get into the details. When we call something a switch, we have left a lot of its behavior unspecified. Note that both Venn diagrams agree that the overall class of devices is "switch" - it's just that we can't leave it at that for the whole book.

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Replying to

The more important issue here is that the Internet has changed a lot since our first edition. While the Internet Protocol was invented to allow interconnection of different network technologies and the networks of different organizations, its success has meant that IP is often just used to forward packets among homogeneous links inside a single organization. That doesn't change the meaning of "router", it just illustrates one of many ways the Internet has changed. The adoption of BGP for routing inside datacenters is another example of how different the Internet and its protocols are today. This is the challenge we face in writing this new edition: to be correct and precise in our descriptions of technology while admitting that the Internet of today is different than the one we described in our first edition. And to do that in a way that leaves the reader understanding the technology without being overwhelmed by the complexity of today's networks. More in the newsletter: https://systemsapproach.org/2026/04/20/not-your-fathers-internet/ 4/4

Systems Approach

Not Your Father’s Internet - Systems Approach

A debate about the difference between a switch and a router highlights the significant changes that have happened to the Internet

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Replying to

@adamshostack@infosec.exchange You get a DRM-free ebook in epub format if you click the "buy ebook" link If you want to preview the book, you can visit the web version or the github repo first

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

RE: @Drbruced@aus.social

Here's a funny story about creating the images for this week's newsletter. How generative AI fails to understand what "transparent background" means.

aus.social

Bruce Davie: "Generative "AI" has no idea what it is doing, a s…" - Aus.Social

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Systems Approach @SystemsAppr@discuss.systems

· 5mo ago

Replying to

@huitema@social.secret-wg.org Fair point. I guess you can add that to the long list of things that DNSSEC doesn't solve. Our intent was to show why securing DNS might be worthwhile, not to suggest that DNSSEC was a good solution (hence the "failed experiment" comment)

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