Timestamp metering and rollover protection in a network device

A method for processing data in a network device, the method comprising the steps of:

• receiving data at one port of a plurality of ports of a network device;
• storing the received data by a memory management unit in a memory external to the network device;
• determining attributes of the received data and an egress port for the received data;
• retrieving the received data from the memory and modifying the received data, if needed, based on the determined attributes to produce processed data;
• and
• updating a metering unit based on the processed data;
• forwarding the processed data through the egress port when indicated by the metering unit;
• wherein the updating step comprises accessing a particular leaky bucket unit of a series of leaky bucket units, decrementing the particular leaky bucket unit when processed data is sent and incrementing the particular leaky bucket unit through a background timestamp method, where tokens are added to each leaky bucket unit only when that particular leaky bucket unit is accessed;
• and
• wherein the step of incrementing the particular leaky bucket unit comprises adding the tokens based on a prior timestamp value, a current timing value and an established rate and a multiplication to establish the tokens is accomplished by shifting a register of the established rate.

A network device for processing data, the network device comprising:

• port means for receiving data and forwarding processed data through an egress port;
• parsing means for parsing the data received from the port means to determine attributes of the data;
• memory means for storing the data received from the parsing means by the memory management unit in a memory external to the network device and retrieving the stored data;
• modifying means for modifying retrieved, stored data, based on the determined attributes to produce processed data;
• metering means for metering a flow of the processed data through the network device;
• and
• forwarding means for forwarding processed data to the egress port when indicated by the metering means;
• wherein metering means comprises accessing means for accessing a particular leaky bucket unit of a series of leaky bucket units, decrementing means for decrementing the particular leaky bucket unit when processed data is sent and incrementing means for incrementing the particular leaky bucket unit through a background timestamp method, where tokens are added to each leaky bucket unit only when that particular leaky bucket unit is accessed;
• and
• wherein the incrementing means comprises adding means for adding the tokens based on a prior timestamp value, a current timing value and an established rate and a multiplication to establish the tokens is accomplished by shifting a register of the established rate.