Packet buffer spill-over in network devices

A method for processing packets in a network device, the method comprising:

• receiving, at a packet processor of the network device, packets ingressing from a plurality of network links via a plurality of network ports of the network device;
• buffering, with the packet processor, the packets in an internal packet memory in a plurality of queues, including buffering packets in a first queue, among the plurality of queues;
• and
• in response to the packet processor detecting congestion in the internal packet memory, selectively forwarding, by the packet processor, a group of multiple packets in the first queue from the internal packet memory to a first port, among one or more ports coupled to one or more external memories, to transfer the group of multiple packets to a first external memory that is coupled to the first port so that the first queue is extended by storing the first queue across the internal packet memory and the first external packet memory;
• maintaining, by the packet processor, a data structure that indicates an ordering of packets in the first queue across the internal packet memory and the first external packet memory;
• and
• using, by the packet processor, the data structure to determine an order of processing of packets in the first queue, including packets in the first queue that are transferred between the internal packet memory and the first external packet memory.