[ipv6-wg] Re: Andre's guide to fix IPv6
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Kurt Erik Lindqvist
kurtis at kurtis.pp.se
Mon Nov 28 18:21:04 CET 2005
On 28 nov 2005, at 12.25, Florian Weimer wrote: > * Kurt Erik Lindqvist: > >>> Previous router generations couldn't process packets on the fast >>> path >>> as soon as they contained IP options (IPv4) or extension headers >>> (IPv6). Has this really changed? >> >> Not for previous version no... > > What do you mean? That deployed hardware is deployed hardware. It won't get magically upgraded. > Do ASIS exist which can skip over an arbitrary > number of IPv6 extension headers, at line rate? Yes. >>> (The whole issue may not be a real problem, it only shows that the >>> claim that IPv6 has been designed for efficient forwarding is crap.) > >> Well...that argument goes both ways. You could also say that the hw >> vendors didn't follow the development as IPv6 was certainly defined >> when the current hw was designed. > > Are you sure? The extension header concept seems to stem from SIPP > (1994), which predates ASIC forwarding (flow-based forwarding was > state of the art back then) and layer 4 filters: Current hardware was designed in last 1-2 years so given the above my argument still holds. > To locate the transport layer header, you must perform limited > processing for all options. With a chained header (like the one in > SIPP and IPv6) of almost arbitrary length, this task can't really be > parallelized in hardware. > > With IPv4, you can at least skip over all IP options in a single step > (violating tons of RFCs, and perhaps your peering contract). I am certainly not an ASICs designer and will never pretend to be one, but AFAIK we can do deep packet inspection at 40G line rate, at an (extremely) high price. CRS-1 for example seem to claim just this. >> Personally I don't think v6 gives as much increased forwarding >> capacity as MPLS - none. > > But this is a pity because one of the explicit design goals was to use > a simpler header format, permitting more efficient forwarding. 8-( Look, IPv6 is longer (more) addresses. Nothing more nothing less. It' won't give you increased performance over v4, but it won't make it worse either. - kurtis -
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