Method of using bit vectors to allow expansion and collapse of header layers within packets for enabling flexible modifications and an apparatus thereof

摘要

Embodiments of the apparatus for modifying packet headers relate to a use of bit vectors to allow expansion and collapse of protocol headers within packets for enabling flexible modification. A rewrite engine expands each protocol header into a generic format and applies various commands to modify the generalized protocol header. The rewrite engine maintains a bit vector for the generalized protocol header with each bit in the bit vector representing a byte of the generalized protocol header. A bit marked as 0 in the bit vector corresponds to an invalid byte, while a bit marked as 1 in the bit vector corresponds to a valid byte. The rewrite engine uses the bit vector to remove all the invalid bytes after all commands have been operated on the generalized protocol header to thereby form a new protocol header.