ISO/IEC 9314-9:2000 pdf download-Information technology – Fibre Distributed Data Interface (FDDI) − Part 9: Low-cost fibre physical layer medium dependent (LCF-PMD).
The basic building block of an FDDI ring is a physical connection as shown in Figure 1 . A physical connection consists of the Physical Layers (each composed of a PMD and a PHY entity) of two stations that are connected over the transmission medium by a Primary Link and a Secondary Link. A Primary Link consists of an output, called Primary Out, of a Physical Layer, communicating over a Primary medium to the input, called Primary In, of a second Physical Layer. The Secondary Link consists of the output, called Secondary Out, of the second Physical Layer communicating over a Secondary medium to the input, called Secondary In, of the first Physical Layer. Physical connections may be subsequently logically connected within stations, via attached MACs or other means, to create the network. As such, the function of each station is implementer-defined and is determined by the specific application or site requirements. Two classes of stations are defined: dual (attachment) and single (attachment). FDDI trunk rings may be composed only of dual attachment stations which have two PMD entities (and associated PHY entities) to accommodate the dual ring. Concentrators provide additional PMD entities beyond those required for their own attachment to the FDDI network, for the attachment of single attachment stations which have only one PMD and thus should not directly attach to the FDDI trunk ring.
The example of Figure 2 shows the concept of multiple physical connections used to create logical rings. As shown, the logical sequence of MAC connections is stations 1 , 3, 5, 8, 9, 1 0, and 1 1 . Stations 2, 3, 4, and 6 form an FDDI trunk ring. Stations 1 , 5, 7, 1 0, and 1 1 are attached to this ring by lobes branching out from the stations that form it. Stations 8 and 9 are in turn attached by lobes branching out from station 7. Stations 2, 4, 6, and 7 are concentrators, serving as the means for attaching multiple stations to the FDDI ring. Concentrators may or may not have MAC entities and station functionality. The concentrator examples of Figure 2 do not show any MACs although their presence is implied by the designation of these concentrators as stations. Connection to the physical medium as established by PMD is controlled by the station insertion and removal algorithms of Station Management (SMT) which are beyond the scope of this standard.