Question 8 part (c)
Layer1, that is, physical layer and layer 2, that is, data link layer are common to USB2 and USB 3.
Layer 1 is the Physical Layer. This Layer includes Fiber, Twisted Pair (copper), Serial, USB, coaxial and others. In other words, interface connections and cabling. Some of those physical connections will be defined by the color of the cable: for fiber, Single Mode cable will be typically yellow and Multi Mode cable typically Orange. The fiber transceivers themselves are available in different kinds of connectors: SC, ST, LC. Serial interfaces are defined by cable types—two wire, four wire; USB interfaces fall into 3 categories of support and thus, identified as 1.1, 2.0 or 3.0; each having a different capability. Twisted pair cabling is available in CAT3 all the way up to CAT7, available in cross over or straight through, as well as whether it is shielded or unshielded.
Layer 2 is the Data Link Layer. The Data Link Layer covers how the data is transmitted over the Physical Layer 1. It packages raw bits from the physical layer into frames (logical, structured packets for data). It is protocol layer responsible for transferring frames from one node to another in a LAN or between network nodes in a WAN. Simply put, Layer 2 provides data transfer across the physical link. But the data link layer is also divided into two sub-layers: the MAC (Media Access Control) layer and the LLC (Logical Link Control) layer. The former controls how computers on the network gain access to the data and obtain permission to transmit it; the latter controls packet synchronization, flow control and error checking.