Re: Protocols at the Point of a Gun

["Perry E. Metzger" <perry@piermont.com>]

Scott Brickner writes:
> Anyway, you computer creates the IP packet, but then sends it to your
> ISP's router.  That router *always* makes changes to the packet header
> because it must decrement the time-to-live field and recompute the
> header checksum.

There is a trivial trick for making the decrement TTL/change checksum
operation very fast, based on noting how a decrement would change the
checksum. Most very high speed routers attempt to avoid doing ANY
processing of the packets at all beyond this, and IPv6 has no header
checksum partially in order to reduce this overhead further. Forcing
routers to do more work is a Very Very Bad Idea.

Perry