Re: [v6ops] new draft: draft-taylor-v6ops-fragdrop

["C. M. Heard" <[e-mail]>]

On Wed, 17 Oct 2012, Warren Kumari wrote:
> On Oct 16, 2012, at 7:19 PM, "Templin, Fred L" <[e-mail]> wrote:
> > I have been informed by individuals working for major network 
> > equipment vendors that their implementations can handle router 
> > reassembly.
> 
> "can handle router reassembly" != "can handle router reassembly at 
> line rate on multiple interfaces".
> 
> You really need this to be line rate on all interfaces, otherwise 
> there is (obviously) a DoS vector here.  Reassembly at 10G (or 
> 100G) is distinctly non-trivial and requires A: large buffers, B: 
> short timeouts, C: gets sad if not all bits go through the same 
> device, D: state and E: hardware designed specifically for this. 
> This is much more than packet comes in, packet goes out...

Excuse me, maybe I'm as dumb as a post, but .... why in the world 
are participants in this thread posing this as problem for the core?

Except for packets specifically destined for core infrastructure 
itself --- and those, surely, are not arriving at line rate -- the 
core has no reason to do anything other than just pass the fragments 
on and let edge devices deal with them.

Indeed, the draft itself states that "IPv6 datagrams with 
fragmentation headers are a non-issue in the core of the internet, 
where fragments are routed just like any other IPv6 datagram.  
However, fragmentation creates operational ssues at the edge of the 
network that may lead to administratively imposed filtering or 
inadvertent failure to deliver the fragment to the application."

//cmh