Wiring concentrator for data networks

#The present invention is directed to data networks and in particular to wiring concentrators employed in them.

#FIG. 1 depicts a local-area network 10 of a type that can implement the Fiber Distributed Data Interface ("FDDI") standard developed by Committee X3T9.5 of the American National Standards Institute ("ANSI"). The network comprises a plurality of network stations 12, 14, 16, and 18 connected by fiber-optic cables. (Actually, networks that implement all aspects of the FDDI specification except for those dealing with the lowest, physical-medium-dependent sublayer have been implemented without fiber-optic cables or optical signals, and those skilled in the art will recognize that such networks can be considered FDDI networks for the purposes of the present invention. To make the description concrete, however, we will refer to the signal medium as optic fibers.)

#In accordance with one topology that the standard specifies, two rings interconnect the stations. A primary ring includes fiber-optic cables 20, 22, 24, and 26, and a secondary ring comprises fiber-optic cables 28, 30, 32, and 34. The signals propagating over the rings convey data organized into "packets," which include information concerning, among other things, the source of the packet and its intended destination. In ordinary operation, a station such as station 12 receives packets from the primary ring by means of a primary input port 36, and a primary output port 38 forwards each packet thus received unless station 12 was itself the source of the packet, in which case station 12 "removes" the packet by not forwarding it. If the packet lists station 12 as its destination, on the other hand, that station still forwards the packet, but it also copies it for use by whatever higher-level entity that station includes.

#These and further features and advantages of the present invention are described below in connection with the accompanying drawings, in which:

#FIG. 1, previously described, is a block diagram of a typical FDDI network;

#FIG. 2, previously described, is a block diagram of the same network illustrating the results of a break in one of the optical links;

#FIG. 7 depicts a concentrator 160 that embodies the present invention. For communication with an external dual ring, not shown, it includes PMD modules 161 and 162 and PHY modules 163 and 164, which perform functions identical to those of the corresponding elements in FIG. 6. A MAC module 165 also performs identically. Like the corresponding elements in FIG. 6, these are typical, but not necessary, elements of a concentrator; as was described in connection with FIG. 5, a concentrator will not necessarily be part of a dual ring. Even if it is part of a dual ring, moreover, it does not in principle need to remove or add packets from the ring, so the MAC module 165 is not always required even if the PHY and PMD modules are.

#The concentrator 160 of the present invention does include the usual PMD modules 166, 168, 170, and 172 for coupling to attached stations 174, 176, 178, and 180, respectively. Instead of having one PHY module for each attached station, however, it has only two altogether, namely, an initialization PHY module 182 and a concentrator PHY module 184. The PHY-level input and output ports 186 and 188 of the initialization PHY module 182 are interposed in an initialization ring 190, over which PHY signals propagate. To perform various functions described below, a supplementary control circuit 191 monitors the operation of an SMT module 192 and supplements its operation so that together they act as a control circuit for controlling the other elements.

#The concentrator PHY 184 has its PHY-level ports 194 and 196 similarly interposed in a concentrator ring 198. FIG. 7 depicts the concentrator PHY module's MAC-level ports 200 and 202 as communicating with the primary ring of the dual-ring network, as it would in a concentrator that is installed as a station on such a network. This is not necessary to the present invention, however; if concentrator 160 were employed in the topology of FIG. 5, for instance, the concentrator PHY's MAC-level ports 200 and 202 would simply be tied together, or some equivalent internal forwarding would occur.