Vasilenko Eduard wrote:
Then why Address Resolution Protocol was needed in principle? (ND or whatever) If the L3 address always had an L2 address inside?
There is no such specification in rfc1526 to mandate "L3 address always had an L2 address inside", which means ARP is necessary for other address formats, which means optional specification of "L3 address always had an L2 address inside" was purposelessly specified.
The OSI was calling for layers isolation. It was a big deal for OSI.
According to wikipedia https://en.wikipedia.org/wiki/Abstraction_layer In computing, an abstraction layer or abstraction level is a way of hiding the working details of a subsystem, allowing the separation of concerns to facilitate interoperability and platform independence. that is, isolation/separation should be a property of layering in general not specific to OSI.
It is not the isolation when addresses from different layers are inserted into each other.
See above that layering is merely "allowing the separation", not forcing the separation. As such, even with a properly layered protocol, you can have implementations actively destroying the separation, though, I think them purposelessly complicated. Masataka Ohta PS Existence of running code for some specification means not that the specification is good but that we can operate and evaluate the specification to judge whether it is good or not. Masataka Ohta
