Efficient parsing of extended packet headers

Abstract

Communication apparatus includes multiple interfaces configured to be connected to a network so as to receive and transmit data packets having respective packet headers, which can include sub-headers of different, respective types. A memory stores instructions for parsing each type of sub-headers and a transition table, which indicates, for each of the types, a location of the instructions for parsing a subsequent sub-header depending upon the type of the subsequent sub-header. A plurality of predefined types are represented in the transition table by a common alias. Routing logic parses the first sub-header in a packet, reads the type of the second sub-header from the first sub-header, and accesses the transition table using the common alias in place of the type of the first sub-header so as to locate and read the instructions for parsing the second sub-header.