Packet router buffer management

Abstract

A router that requests a reservation for an egress port prior to dequeuing a received packet. A reservation is granted only if there is space on the egress port for at least a maximum size packet. An ingress processor requests allocation of a packet buffer. An allocator grants the packet buffer, but if there are fewer than a threshold number of buffers available, the ingress processor will not accept the grant unless the received packet is to be routed to a port inside the device comprising the router. This conserves the packet buffer(s) for packets destined for locations within the device. After a reservation is obtained and a packet buffer has been accepted, the ingress processor begins dequeuing a received packet from an ingress port queue to the buffer, and provides an identifier of the buffer to an egress processor. The identifier is enqueued by the egress processor. After the identifier is dequeued, the egress processor copies the packet from the buffer to an egress queue and releases the buffer. The buffer can be released prior to completion of the data being copied.