Packet processing using non-sequential encapsulation and decapsulation chains

Abstract

A method for processing packets in a router includes specifying operations on packets as chains of processing elements. Each chain is uniquely associated with one interface/protocol pair, and each processing element performs at least one function on a packet. An incoming packet is received, and processed, first by a demultiplexor element which determines the protocol of the next higher level used by the packet. Then, the packet is processed by the elements of a decapsulation chain associated with the interface on which the packet was received, and by the elements of an encapsulation chain associated with the interface on which the packet is to be transmitted. The demultiplexor element or operation passes the packet on to a decapsulation chain associated with the protocol and with the incoming interface, depending on protocol information contained in the incoming packet. Decapsulation and encapsulation chains can be built dynamically, by inserting new and removing old elements as necessary as new protocols are developed and new features added. A chain walker walks through the chains, passing the processed packet to each element in a chain, until either the end of the chain is reached and processing is complete, or until the packet is dropped because no function can process it, or because a packet is processed by an outside process or by hardware, which may optionally stop the chain walk. A chain walk may be temporarily halted, or may be terminated. If temporarily halted, the chain walk can be resumed at any element in the chain, depending on the packet's requirements. A chain walk can also begin at any element in a chain. Alternate branches within the chain can be provided, where each branch can comprise zero or more elements. A classifier determines which branch to take, based on at least one characteristic of the packet being processed, and executes the elements of the selected branch.