Method and apparatus for controlling packet header buffer wrap around in a forwarding engine of an intermediate network node

Abstract

A method and apparatus manages packet header buffers of a forwarding engine contained within an intermediate node, such as an aggregation router, of a computer network. Processors of the forwarding engine add and remove headers from packets using a packet header buffer, i.e., context memory, associated with each processor. Addition and removal of the headers occurs while preserving a portion of the 'on-chip' context memory for passing state information to and between processors of a pipeline, and also for passing move commands to direct memory access (DMA) logic external to the forwarding engine. A wrap control function capability within the move command works in conjunction with the ability of the DMA logic to detect the end of the context and wrap to a specified offset within the context. That is, rather than wrapping to the beginning of a context, the wrap control capability specifies a predetermined offset within the context at which the wrap point occurs.