network assessment report

Network assessment report and shapers are modeled after token bucket algorithms. Essentially, token bucket algorithms are metering engines that keep track of how much traffic can be sent to conform to the specified traffic rates. A token permits the algorithm to send a single bit (or, in some cases, a byte) of traffic. These tokens are granted at the beginning of some time increment, typically every second, according to the specified rate referred to as the committed information rate (CIR). The CIR is the access bit rate contracted with a service provider or the service level to be maintained

For example, if the CIR is set to 8000 bps, then 8000 tokens are placed in a "bucket" at the beginning of the time period. (Note that this description represents a simplified view of the algorithm and might not be strictly true in all cases, but it illustrates the general operation of the policing mechanism.) Each time a bit of traffic is offered to the policer, the bucket is checked for tokens. If there are tokens in the bucket, the traffic is passed. One token is removed from the bucket for each bit of traffic that is passed. Therefore, traffic is viewed to conform the rate, and the specified action for conforming traffic is taken. (Typically, the conforming traffic is transmitted.) When the bucket runs out of tokens, any additional offered traffic is viewed to exceed the rate, and the exceed action is taken. (The exceeding network assessment report typically either is re-marked or is dropped.)