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Pedantically: TCP has segments, IP has packets, and Ethernet has frames. They are one-to-one in simple cases, but not always. https://networkengineering.stacke
by ooterness 2y ago
Pedantically: TCP has segments, IP has packets, and Ethernet has frames. They are one-to-one in simple cases, but not always.
https://networkengineering.stackexchange.com/questions/50083/ https://networkengineering.stackexchange.com/questions/50083...
In particular, fragmentation by intermediate routers means that the server and receiver may disagree about the frame and packet boundaries. TCP is expected to make a "reliable" pipe-like service out of whatever happens, and the application layer doesn't have (shouldn't need?) visibility into that process.
- LudwigNagasena 2y agoFalsehoods programmers believe: TCP/IP can be coherently mapped to the OSI model.
- Rauchg 2y agoFalsehoods programmers believe: the OSI model
- fanf2 2y agoYep. https://dotat.at/@/2024-03-26-iso-osi-usw.html https://dotat.at/@/2024-03-26-iso-osi-usw.html
- devman0 2y agoFalsehoods programmers believe: the OSI model is useless
- akira2501 2y agoIt's useful. It's not controlling.
- jerf 2y agoSure, it's misleading, needs a lot of "interpretation" doing a non-trivial amount of the lifting to make it map to anything in the real world, mismatches things that happen in the real world while leaving no room for other things that happen in the real world a lot, and will lead anyone who tries to use it to understand the real world deeply astray, but it isn't always wrong about absolutely everything so it has some non-zero "utility". Fine. It's not wrong about absolutely everything all the time. It isn't bereft of all truth. It's just something that is of net negative value. I see no value in insisting on trying to "rescue" a net-negative value model of the world. I suppose you could say ultimately I agree with you though. The OSI model isn't useless. It's worse than useless. You're better off trying to understand networking from basic first principles than through the lens it provides.
- devman0 2y agoAnalogies are rarely perfect, that's why they are analogies. The OSI model isn't intended to be perfect and yeah there are a lot of details that leak between layers, but is also expected, any non-trivial abstraction is always going to be leaky. That doesn't mean it useless or absent of value in discussion at appropriate levels.
- dathinab 2y agoIt's not useless, just bad at it's job. I mean in practice it's so broken, imprecise and messy to a point it's often more misleading then helpful and IMHO should have been replaced in teaching with something better well over a decade ago. And to be clear I'm not saying it's bad because some small implementation details don't fit, it's bad in it's job of being a high level abstraction where you ignore many implementation details.
- deleted 2y ago[deleted]
- ameliaquining 2y agoI think I've heard the term "packet" used to refer to the general category of thing that Ethernet frames, IP packets, and TCP segments are all examples of.
- ooterness 2y agoColloquially, yes, they're all just packets unless I'm writing an RFC for the IETF. If I recall correctly, the formal term for the all-encompassing category is the "datagram". It's like who-vs-whom. Prescriptivists will try to tilt that windmill forever, descriptivists observe that most people just don't care.
- paulddraper 2y agoThose are all packets.