Network switch with high-speed serializing/deserializing hazard-free double data rate switch
A network switch for switching packets from a source to a destination includes a source port for receiving an incoming packet from a source, a destination port which contains a path to a destination for the packet, and a filter unit for constructing and applying a filter to selected fields of the incoming packet. The filter unit further includes filtering logic for selecting desired fields of the incoming packet and copying selected field information therefrom. The filtering logic also constructs a field value based upon the selected fields, and applies a plurality stored field masks on the field value. The switch additionally includes a rules table which contains a plurality of rules therein. The filtering logic is configured to perform lookups of the rules table in order to determine actions which must be taken based upon the result of a comparison between the field value and the stored filter masks and the rules table lookup.
1. A network device comprising:
a memory; and
a high performance interface for communicating with network elements through transfer of data contained in said memory;
wherein said high performance interface comprises a data connection bus, where data is transferred on both a rising edge and a falling edge of a clock signal, the data connection bus comprising output drivers and a multiplexing circuit connected to the output drivers;
wherein said multiplexing circuit has two levels of glitchless multiplexors to serialize said data transmitted over said high performance interface.
2. A network switch as recited in claim 1 , wherein a first level of glitchless multiplexors comprises two glitchless multiplexors, each having a first input, a second input, an output and control, and a second level of glitchless multiplexors comprises a single glitchless multiplexor, having two input points, an output point and a control point;
wherein said first level of glitchless multiplexors receives data from said data contained in said memory and the output of each of said two glitchless multiplexors is connected to one of the two input points of said single glitchless multiplexor.
3. A network switch as recited in claim 2 , wherein said multiplexing circuit further comprises two additional multiplexors, each having two input connections, an output connection and a control connection, wherein said data received from said data is input into said input connections of said additional multiplexors and said output connection of each of said additional multiplexors is connected to the first and second inputs of said first level of glitchless multiplexors.
4. A network switch as recited in claim 3 , wherein the multiplexing circuit additionally comprises a plurality of flip flop circuits, each having an input port, and output port and clock input connected to said clock signal, to control the flow of data to said first level of glitchless multiplexors and said additional multiplexors.
5. A method of processing data through a high performance interface of a network device, said method comprising the steps of:
receiving parallel data to be sent over a high performance interface;
storing portions of said parallel data alternatively in a first register clocked on a positive edge of a clock signal or a second register clocked on a negative edge of said clock signal;
inputting said portions into first level glitchless multiplexors;
multiplexing said portions using said first level glitchless multiplexors and outputting outputs of said first level glitchless multiplexors to a second level glitchless multiplexor;
multiplexing said data by selecting alternating inputs to be multiplexed onto outputs of said second level glitchless multiplexor into said second level glitchless multiplexor;
wherein said first level glitchless multiplexors produce a function hazard when more than one input to said first level glitchless multiplexors changes simultaneously;
wherein said step of multiplexing said data by selecting alternating inputs is timed such that said second level glitchless multiplexor only selects input from a particular one of said first level multiplexors that is not producing said function hazard.
6. A method of processing data according to claim 5 , wherein the step of receiving parallel data comprises receiving parallel data derived from packet data received by the network device.
7. A method of processing data according to claim 5 , further comprising:
receiving data on a port of the network device;
determining a destination for that data by the network device; and
sending that data to the high performance interface.
8. A method of processing data according to claim 5 , wherein, after said step of multiplexing said data, the method further comprises forwarding the multiplexed data to a linked network device through the high performance interface.