At 04:27 AM 7/24/01 -0400, Ignatios Souvatzis wrote:
>On Tue, Jul 24, 2001 at 04:42:37PM +1200, Sean Lin wrote:
>
>> As we all know, there's no ipv6 header checksum field. Therefore,
>> for routers forwarding packets, the checksum of ipv6 packets cannot be
>> calculated? Which means that ipv6 routers will generally have a faster
>> throughput compared to a similar ipv4 router (assuming there's no
>> extension headers and option headers)?
>
>Yes. That's the reason it was designed that way.
For software based forwarding engines, you are correct.
However, most if not all high-speed routers one encounters
today use silicon-based (ASICs and/or FPGAs) forwarders.
The nice thing about silicon is that lots of stuff can be
done in parallel. The IPv4 header checksum can be, and is,
calculated in parallel with the other header checks, etc,
that are going on. Thus, it takes 0.000000.... additional
time. If IPv6 had a header checksum, it too would be
calculated in 0.00000... additional time.
Frank Kastenholz
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