Packet processing graphs

A packet processing system in which packet classifier nodes are arranged in a packet processing graph, the system comprising:

• a packet processing graph comprising a plurality of classifier nodes including a root classifier node and a plurality of leaf classifier nodes defining a plurality of packet processing paths through the graph, the root classifier node being connected to each of the plurality of leaf classifier nodes through a respective packet processing path in the graph,
• wherein each of said classifier nodes is configured to store node match data indicative of at least one match to be applied by the respective classifier node,
• wherein said classifier nodes comprise at least a first classifier node and a second classifier node, the first and second classifier nodes being arranged in a first packet processing path of said plurality of packet processing paths, and wherein:
• the first classifier node is configured to store node match data indicative of a match corresponding to content from a plurality of packet header field types, including at least an Ethertype field in an Ethernet header;
• the first classifier node is configured to store a plurality of node match data entries, each corresponding to a separate tunnel endpoint;
• the second classifier node is connected to a no-match output of the first classifier node;
• and
• the second classifier node is configured to store node match data indicative of a match corresponding to one or more packet header fields, including at least the Ethertype field in the Ethernet header.