should phy layer and mac layer be designed together?

Question

I have a question about the independence of the layers. I know that the layers in protocol stack are designed in a way to be independent from each other. I want to know does it mean also that we can use different combinations for the layers.

The reason I am asking this is that I notice that in network simulator 3 (ns-3), wifi module has its own mac layer and phy layer. I was wondering whether it is possible to use a phy layer module of a technology and use mac layer module of another technology, when specifying the layers of a node; or are they designed depending on each other? Could you please help me?

Answer 1

That's more a philosophical question...

Most often, the physical and the data link layer are designed together, even if many data link layer implementations are very similar. The point is that you can optimize and hone the data link layer for what the physical layer doesn't cover very well.

Take 802.11 and 802.3 for example - 802.3 L1 is highly reliable, very fast (10M-400G) and point-to-point. Popular L2 features are link aggregation, redundant meshing and virtualization.

802.11 L1 is wireless radio, so there are inherent problems like bandwidth sharing, noise, reach and eavesdropping. It's L2 focuses on media access, reliability, encryption and authentication.

Answer 2

I do not clearly understand your question,

But, think about these layers as an information package, that can be understood only by the same type of equipment but on the other side of the communication.

WiFi is a L2 technology, that (not necessarily) carries another L2 information. (There are other technologies using this approach i.e.: QinQ) Actually L3 packets can also carry L2 information, but that is a different story.

So, you have a WiFi layer, which is processed by the other wireless device you talking to, but that conversation is not happening on the WiFi device itself so it needs to "forward" the traffic for example a server which is communication through Ethernet, so the WiFi frame contains information about the server's L2 information.