its written that
The link layer checksum protected the packets only while they traveled across the link and not while they were inside the router. Thus, packets were delivered incorrectly even though they were correct according to the checks on every link.
My question is, a link is just a medium for data to travel from one device to other(whether it is from router to router, router to other computer, etc.). so how can a link will check for correctness or incorrectness of data? because, checksum for DLL frame will be checked only at router, not on links.
and what does it mean by "not while they were inside router"? I mean, how can a data get corrupted inside a router(other than the case of crash and vulnerable attacks)?
