Abstract: The present invention allows preloading of channel context in advance of actual channel change in a digital communication system. The system uses a channel identification signal to identify the present channel number of data on a data bus. Before the actual change in channel, a future channel number is inserted into the channel identification signal. Another signal is used to indicate the location of the future channel number in the channel identification signal. As a result, the system is able to know in advance the new channel number. The corresponding context can be loaded before the arrival of the new channel data.

Abstract: A network switch forwards data packets between network stations connected to its input and output ports. Each data packet includes the network address of a destination station. The receiving input port consults an address translation system including a local address translation cache within each input port for caching recently used address-to-port translation information, a set of secondary address translation units each serving a separate cluster of input ports for caching a larger amount of recently used address translation information, and a main address translation unit storing address-to-port translation information for all network stations. An input port not having appropriate translation information in its local cache sends an address translation request to a secondary address translation unit. A secondary address translation unit not having appropriate address translation information to respond to the request, forwards the request to the main address translation unit.

Abstract: A local area network switch includes input and output ports for receiving and transmitting broadcast and unicast data transmissions from and to corresponding network stations and a crosspoint switch for selectively routing data transmissions between the ports. All input ports have one connection to the crosspoint switch for forwarding incoming broadcast and unicast data transmissions to the crosspoint switch. Each output port has a unique unicast link to the crosspoint switch for receiving unicast transmissions directed solely to its corresponding network station. All output ports also share a second broadcast link to the crosspoint switch for receiving broadcast transmissions directed to all network stations. The crosspoint switch routes each unicast transmission from an input port only to the appropriate output port via the output port's unicast link and routes broadcast transmission from an input port to all output ports via the common broadcast link.

Abstract: A network switch routes data transmissions between uniquely addressed network stations connected to input and output ports of the switch. The switch includes a hierarchical address translation system for relating network addresses of stations to receive incoming transmission to the switch ports to which they are connected. The translation system includes a central translation unit having a memory for storing a mapping entry for each network station, the entry mapping the station's network address to its switch port. The system also includes a local translation unit in each input port. Each local translation unit contains a local cache memory for storing a smaller subset of the mapping entries stored by the central translation unit. When a data transmission arrives at an input port directed to a network address, the input port looks for an entry in its cache memory mapping that network address to an output port.

Abstract: A local area network switch includes a set of input ports each receiving and storing incoming packets from a corresponding network station, a set of output ports each forwarding packets to a corresponding network station, and a switching system for routing packets from the input ports to the output ports. The output ports are interconnected to form an output token passing ring and the input ports are interconnected to form an input token passing ring. Whenever an idle output port receives the output token, it holds the output token and signals the input ports to start an input token passing cycle. During an input token passing cycle, an input port storing a packet destined for an output token holder terminates the input token passing cycle when it receives the input token and signals the switching system to establish a connection to the output token holder. To fairly distribute arbitration priority, input and output ports starting positions are rotated for successive input and output token passing cycles.