[ipv6-wg] Re: Andre's guide to fix IPv6

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 -