Re: [Tsv-art] [OPSEC] Tsvart last call review of draft-ietf-opsec-ipv6-eh-filtering-06

[Stewart Bryant <[e-mail]>]

On 26/11/2018 21:59, Joe Touch wrote:
>
>
>
> On 2018-11-26 09:53, Gert Doering wrote:
>
>> Hi,
>>
>> ...
>> As people have explained in great detail, there's work that the routers
>> are built to do, where the number of packets they can handle is nearly
>> arbitrarily high.
>>
>> Then there's packets that are seen as an exception, and handled in a
>> not-as-powerful path.  Back then, when the Internet was new, these
>> exceptional packets were considered "something we'll handle when the
>> need arises", and it mostly worked.
> Translation - "we cheated", and that's not working anymore. Agreed.

Fundamentally it is about economics.

Doing complex processing in the fast path is expensive. It is expensive 
to have the cycles
available. In designs that use fixed logic assistance it is pretty much 
infeasible to cope with
multiple options as the combinatorial complexity explodes on you.

As the packet size increases this is also expensive in terms of the fast 
packet caching memory
needed.

In the days when the fast path/slow path decision was first taken, there 
were also fundamental
limits on what could be implemented at any price thus pushing the cost 
from equipment
to physical infrastructure. There are some use cases that say that we 
need to get 1Tb/s
to the host for some applications, so we cannot be sure that the 
fundamental parsing limit
problem will not re-occur.

In any case, fast feature = silicon = cost and whilst you can or at 
least could ride More's law,
at the end of the day you have to trade features against port density 
against power against
capex against opex. ... and all this is without the issue of the 
internet carbon footprint
coming under scrutiny.

So what this came down to at the time the feature split was taken was a 
decision on economics,
i.e. is the cost of the additional feature worth the price paid? That is 
still true and  I think that
we need to remember that as we add non-optional features into the fast 
path.

- Stewart