Comment by msla | Hacker News Reader

Comment by msla | Hacker News Reader

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It's important to keep layering in mind when talking to people outside the IETF, but the IETF itself is not impressed:

https://en.wikipedia.org/wiki/Internet_protocol_suite#Compar...

> The IETF protocol development effort is not concerned with strict layering. Some of its protocols may not fit cleanly into the OSI model, although RFCs sometimes refer to it and often use the old OSI layer numbers. The IETF has repeatedly stated that Internet protocol and architecture development is not intended to be OSI-compliant. RFC 3439, referring to the Internet architecture, contains a section entitled: "Layering Considered Harmful".

Anyway: People sometimes like to pretend that OSI is a model and TCP/IP implements the model, forgetting that OSI is/was a protocol stack and TCP/IP has no interest in being "compliant" with any other protocol stack to the extent it mimics its layering architecture.

This is one of those cases where both sides have some insight depending on viewpoint. The OSI model is like every other model. It isn't reality (at least in TCP/IP) but instead is a helpful abstraction esp. around troubleshooting and understanding networking concepts. There comes a point where the model breaks down but that doesn't mean it's an unhelpful model just that it isn't a complete picture. I try and work networking problems through the OSI layer model but am aware when things don't really fit well into it (MPLS, MSS, ARP, Layer 5-7).

I agree with you, except that the use of the OSI model seems to be distorting history: TCP/IP went up against OSI and won, even though OSI was favored, because TCP/IP could get working systems faster. That's a lesson which should be learned, but it gets obscured if you think that TCP/IP implemented OSI and there never was a competition.

Plus, the OSI model is rather complicated; there's a "TCP/IP Model" with four layers which is a lot simpler:

https://www.geeksforgeeks.org/tcp-ip-model/

> Process/Application Layer

> Host-to-Host/Transport Layer

> Internet Layer

> Network Access/Link Layer

(This seems to be the RFC 1122 model, BTW.)

RFC 1122 and RFC 871 each have models, too.

RFC 871 has:

> Application/Process

> Host-to-host

> Network interface

https://en.wikipedia.org/wiki/Internet_protocol_suite

It's just part of the lingo, a tool to communicate. The TCP/IP model ignores the physical layer making it a less useful tool.

For me the OSI tends to come up at work to talk about scope or areas of control. People will say "that happens in layer 3" (for instance) as shorthand, not as a referent that corresponds to any actual thing.

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