Re: Experiences with IPv6 and Routing Efficiency

[Frank Habicht <geier () geier ne tz>]

Hi Owen,

On 1/21/2014 12:13 PM, Owen DeLong wrote:
> On Jan 18, 2014, at 23:19 , Frank Habicht <geier () geier ne tz> wrote:
> > c) v6 with a few extension headers
> In this case, it will be at 40+o+n octets into the packet where o is the
> number of octets contained in headers prior to the TCP header and n is
> defined as in (b) above.

my point tried to be that it can be hard for an ASIC to know 'o'

> > now program a chip to filter based on this port number...
> I think you might want to be more specific. After all, an ARM 9 is a
> chip which can easily be programmed to do so (in fact, I can point to
> iptables/ip6tables as running code which does this on the ARM 9).

I was thinking about hardware that's forwarding packets "not in software"
some of those boxes probably want to limit tcp ports 179 and 22.

> So... I suppose that whether your complaint has merit depends entirely
> on whether or not extension headers become more common on IPv6 packets
> than options have become on IPv4 packets or not and also on how hard it
> is to build fast-path hardware that bypasses extension headers that it
> does not care about. Since you only need to parse the first two fields
                                 ^^^^ ?
> of each extension header (Next Header Type and Header Length) 
... recursively for all extension headers ...

> to know
> everything you need to bypass the current header, it shouldn't be too
> hard to code that into a chip...
who's done that so far?
Up to what number of EHs or octet-length?

Thanks,
Frank