This part of ISO/IEC 9314 defines a conformance test of the PHY functions in a path through an FDDI node. Figure 1 is a functional block diagram of an FDDI path. The path contains the necessary functions to repeat (that is decode and retransmit) frames through an FDDI node The PHY Repeat Filter is optional when there is a MAC in the repeat path. If there is no MAC in the repeat path, then the function is implemented in PHY. This test standard makes no assumption about the presence or absence of MAC on the path and is intended to operate with or without a MAC. It tests the repeat filter function wherever it is located. However, the results of some tests may be slightly different if a MAC is present.