flushtable

A flushtable is a data structure used in computer networking and telecommunications, particularly in high-speed packet processing. It is a type of lookup table designed to efficiently determine whether a particular packet should be forwarded or dropped based on a set of rules. The "flush" aspect refers to the ability to quickly clear or reset the entire table, which is crucial for adapting to rapidly changing network conditions or security policies.

The primary function of a flushtable is to perform packet filtering and forwarding decisions. Network devices like routers and switches utilize flushtables to make rapid decisions about where to send incoming data packets. These decisions are based on criteria such as source and destination IP addresses, port numbers, and protocol types. When a packet arrives, its header information is compared against the entries in the flushtable. If a match is found, the corresponding action, such as forwarding the packet to a specific output port or discarding it, is executed.

The efficiency of a flushtable lies in its optimized design for fast lookups and modifications. In scenarios where network traffic patterns change dynamically, or when security threats require immediate action, the ability to instantly clear and repopulate the flushtable is paramount. This rapid update capability allows network infrastructure to adapt quickly to new rules, blocking malicious traffic or rerouting legitimate traffic around congestion points without significant performance degradation. Flushtables are a key component in achieving line-rate packet processing in modern high-performance networking devices.