Figure 25-2 on page 603 illustrates the Link Layer state machine. It should be noted that the Physical Layer signals its current state (up or down) to the Link Layer. The actual signal name is immaterial, but the specification uses the name PhyLink. At a given moment in time, the Link Layer is in one of the following states:
LinkDown state. While in the LinkDown state, the Link Layer has the following operational characteristics:
- The Link Layer's ability to transmit and receive data packets is disabled. Data packets are defined as all packet types other than SMPs or link-level Flow Control Packets (FCPs). See “Link-Level Flow Control” on page 637.
- The Link Layer's ability to receive and send SMPs is disabled. ...