[ih] Fwd: early networking: "the solution" (Dave Crocker)

[Larry Stewart]

One of the nicest coding ideas in coding is to never recalculate a checksum, but only to compute a delta to the existing checksum.  This eliminates a substantial number of blind-spots in multihop paths.  This works for IP checksums and for CRCs as well because the algorithms are linear.  It is really part of the end-to-end design principle.

IP has separate IP and TCP checksums, which is good for router performance, but a different design could save 16 bits per packet or use a 32 bit checksum.
-Larry