Re: Unknown header extension or option

[Fernando Gont <[e-mail]>]

Hi, Fred,

On 11/17/2014 04:24 PM, Fred Baker (fred) wrote:
>> 
>> I haven't re-read RFC 2460 but I'm pretty sure that the preamble 
>> "is required to proceed" above is supposed to handle this. A
>> router is only "required to proceed" past the IPv6 header if -
>> the packet is explicitly addressed to (one of) the router's IPv6
>> address(es) (which was the case for routing headers) - the packet
>> has a hop-by-hop options header
>> 
>> But a router must implement HBH. And if the packet has a routing 
>> header then there is not need for the router to look at the
>> header after the RH unless segments left = 0 (i.e., the router is
>> at the final destination of the RH path).
>> 
>> So if the world only has hosts and routers I think the text if 
>> fine.
> 
> Well, I’m not so sure. I’d suggest you re-read 
> https://tools.ietf.org/html/rfc2460#section-4
> 
> It doesn’t refer to a router or a host; it refers to a node. The 
> context is not “going beyond the IPv6 header to TCP-or-whatever”.
> It is “I processed the base IPv6 header or some extension header,
> for whatever reason I need to go to the next extension header, and
> I don’t understand it.”
> 
> Extension headers invariable have as their first two bytes:
> 
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |  Next Header  |  Hdr Ext Len
> | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

They don't. Please check
<http://tools.ietf.org/id/draft-gont-6man-ipv6-universal-extension-header-01.txt>



> Now, everyone gets their own opinion of SRH, and personally I’m
> not sure I see why the considerations of RFC 5095 don’t apply. 
> None-the-less, I’m wondering what happens when we do get a new 
> extension header. I’m not sure it’s good. If we are trying to
> deploy a new extension header and it is presented to an unupdated
> system, we get a parameter problem, not a robust response.

This is also discussed in the aforementioned I-D.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492