From: Terje Mathisen "terje.mathisen at on
Benny Amorsen wrote:
> Terje Mathisen<"terje.mathisen at"> writes:
>> Yes, but if you want to take a chance and skip the trailing checksum
>> test, in order to forward packets as soon as you have the header, then
>> you would have even more severe timing restrictions, right?
> There are several layers of checksums at play here. If we stick to IP,
> only the header has a checksum, and for IPv6 even that has been removed.

Mea culpa, or wishful thinking on my part. :-(

> So there isn't really a chance to take, because you have the checksum
> before you start receiving the payload (and the payload isn't
> protected).
> There is a whole-packet checksum at the ethernet level (if the physical
> layer happens to be ethernet, of course). Switches used to pretty much
> universally do cut-through switching until gigabit switches arrived.
> Almost all gigabit switches are store-and-forward, but somehow latency
> was rediscovered in 10Gbps-switches, so quite a few of those are
> cut-through.

> Unfortunately "cut-through routing" refers to something entirely
> different from "cut-through switching". I haven't been able to find any
> products claiming to do anything but store-and-forward routing.

OK, that was really what I was asking about.


- <Terje.Mathisen at>
"almost all programming can be viewed as an exercise in caching"