Comment by 9x39 | Hacker News Reader

Comment by 9x39 | Hacker News Reader

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The 'why' behind all of these protocols and decisions is left out in favor of the cert exams. Being able to implement is usually what gets you paid.

>mere fact that Layer 2 and Layer 3 addresses are distinct concepts.

The logical separation between the ideas allows for a lot of flexibility, and there were some wrong answers on how scalable vs flexible things should be.

Ethernet and IP beat the shit out of everything else: https://en.wikipedia.org/wiki/Protocol_Wars

They emerged with a decent answer: L2 crosses intranetwork, L3 crosses internetwork. Their separation allows L3 addressing to be completely unaware of multiple changing L2 (lower level) intranetwork switches, which is immensely useful.

Trying to solve everything with One Master Protocol to solve it all turned out like this: https://xkcd.com/927/

this works nicely in IPV6, where true seperation of layer 2 and layer 3 exist. This does not exist in practice in ethernet, because ARP is required as a mechanism to learn MAC IP bindings and is dependant on IP AND Ethernet.

IPv6 solves this by doing neighbour discovery on link local addresses and multicast addresses.

I am doing a little facepalm over the L2-L3 distinction, thanks for being gentle and thoughtful. Sometimes I interrogate how things are, imagine what another paradigm would look like, but always end up where I started... I see that and think, hm, maybe the design of networks as we know them are expressing some sort of structure in the Platonic space.

I took a course called “Introduction to Internet Architecture” back in 2017 with a wonderful professor. The course opened with a prompt, “What is communication?” We started with smoke signals and worked our way up the OSI layers (including voltage-level encodings on the wire). I remember drawing those layers and asking, “What problem is each layer trying to solve?”

Also that XKCD comic is a classic. Love it. I don’t see any value in overhauling the protocols of today. It seems like the future (or present) of networking is overlays. When this recent cert covered SDN, it really abstracted away everything I had just learned and I felt a little sad about it honestly - as if switch/router configuration would some day be ubiquitously software-defined, getting totally buried by the application layer and becoming almost apocryphal like assembly or machine code… something we know exists but rarely touch.

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