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I was reading CCNA R&S book by Todd Lammle, I saw this in the chapter TCP/IP Basics under Network Access/Link Layer

Advantage of this layer over Layer 1 and Layer 2 of OSI model is that there were no set physical layer specifications, so it could run on any existing or future network

what does this mean? I am not getting any idea it. Somebody please explain!

  • That is something you may need to ask the author directly. – Ron Maupin Mar 24 '18 at 15:55
  • This is what he is (poorly) trying to explain: the layers are independent. Layer 3 performs its role despite what is going in at layer 1. IP addresses work the same way regardless of whether the physical medium is twisted pair or fiber or wireless. More information about the roles of each individual layers here. – Eddie Mar 24 '18 at 17:51
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Apr 1 '18 at 23:15
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Advantage of this layer over Layer 1 and Layer 2 of OSI model is that there were no set physical layer specifications, so it could run on any existing or future network

This is nonsense. Whether you call it link layer or make a distinction between data link layer and physical layer, the functionalities are exactly the same.

The OSI model doesn't define a specific physical layer it just defines its functionality. ARPA/DoD/IETF just don't care about the hardware side and throw everything together.

The OSI approach is very helpful for providing a good structure for the lower four layers (which actually need some sublayers as well). The upper layers are pretty much mashed together in practice, so the OSI model can't be easily applied - however, it may still be helpful for modelling a new protocol or application.

A good layer structure opens to door to flexible enhancements and replacements in an isolated layer while preserving all the other layers.

As with any model, you have to keep in mind that it's a model and you don't have to stick to the letter at all times.

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