Re: [secdir] SECDIR review of draft-ietf-bess-pta-flags-02.txt

["Christian Huitema" <[e-mail]>]

On Monday, April 25, 2016 10:40 AM, Eric C Rosen wrote:
> 
> On 4/24/2016 7:29 PM, Christian Huitema wrote:
> > We have thus two possible issues:
> >
> > 1) A router supports RFC 6514 but does not implement the extension
> > mechanism.
> > 2) A router supports the extension mechanism, but does not support the
> > specific extension.
> 
> With regards to case 1, I don't think there's much to say.  A router that
> supports RFC 6514 but not the pta-flags draft will ignore all the flags
except
> the one that is defined in RFC 6514.
> 
> Similarly, in case 2, a router that doesn't recognize a particular flag
will ignore
> it.  However, I can add some text to the draft saying to ignore any bits
you
> don't recognize.

Yes, please. 

> If there are mechanisms that require the use of a particular extension,
those
> mechanisms won't work properly with routers that don't support the
necessary
> extension.  Applications that require such mechanisms either need to
provide
> signaling to determine whether all involved routers support the necessary
> extension, or else they need to define procedures for interworking with
routers
> that don't support the extension.  I could add some text stating this, but
I don't
> think there's much more that can be said.

Don't routers have to relay these extensions to BGP-adjacent routers? In
that case, are they supposed to blindly relay the extensions that they don't
understand? Are they supposed to reset the corresponding flags to zero, or
just leave them as is? It is probably obvious for you, but these things are
often better said than just implied.

-- Christian Huitema