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I saw it stated in an answer to this other question What transmission service gurantees does Ethernet give? that every layer of the OSI model provides both "hard" and "soft" guarantees to the layer above it (integrity, sequentiality, non-duplication, etc.)

What are those guarantees for every layer?

Stack Tracer
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  • Sounds like homework... – Zac67 Jan 16 '20 at 07:33
  • Not homework. I just realized I knew what was typical, but I was completely unfamiliar with what was acutally _guaranteed_, vs _just kinda works_. – Stack Tracer Jan 16 '20 at 07:36
  • @Zac67 as an example, apparently UDP doesn't guarantee delivery in order. That might be 1 in a million, but is something I feel like should probably still be handled. Who's screwing up guaranteed delivery order between Layer 1 (pretty sure maxwell's equations guarantee all the bits go the same speed) and Layer 4, where UDP lives. – Stack Tracer Jan 16 '20 at 07:42
  • @StackTracer, UDP and other such protocols were not developed with OSI in mind. It is the IP Services model that is closest to reality. No OS has implemented OSI. – Ron Maupin Jan 16 '20 at 10:55
  • @StackTracer Apparently, you're not interested in *what guarantees each OSI **layer** provides* (which is a bland "none actually") but *what guarantees each different transport/network/link layer **protocol** provides*. That's a really long list and you need to ask more specifically, we cannot write a book for you. – Zac67 Jan 16 '20 at 13:32
  • @Zac67 so the answer from the other guy in the linked question is complete BS and there are no guarantees provided by the OSI model? – Stack Tracer Jan 16 '20 at 14:03
  • @StackTracer No *layer* in the OSI model guarantees anything. A specific *protocol* might (and often does). The difference is that if a layer was supposed to guarantee anything, each and every protocol within that layer would be required to comply. – Zac67 Jan 16 '20 at 15:28
  • @Zac67 That's kind of the point of the layers in the OSI model, isn't it? If the layers don't provide any guarantees at all, what is the point of the model? – Stack Tracer Jan 18 '20 at 01:17
  • Sadly, once again, the question pointed to for this one doesn't address the question. The answer is that some services provide contracts. The OSI general layer model doesn't actually define any specific services. However, the ITU does define OSI services that provide guarantees. For example, the OSI CONS (Connection Oriented Network Service) and COTS (Connection Oriented Transport Service) offer a "reliable" service, meaning that if the message might not have made it, you will be told. – Jeff Learman Dec 18 '20 at 18:04

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