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

"Christian Huitema" <huitema@huitema.net> Tue, 26 April 2016 17:10 UTC

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From: "Christian Huitema" <huitema@huitema.net>
To: "'Eric C Rosen'" <erosen@juniper.net>, <iesg@ietf.org>, <secdir@ietf.org>, <draft-ietf-bess-pta-flags.all@ietf.org>
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Date: Tue, 26 Apr 2016 10:10:03 -0700
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Subject: Re: [secdir] SECDIR review of draft-ietf-bess-pta-flags-02.txt
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On Monday, April 25, 2016 1:25 PM, Eric C Rosen wrote:
> 
> On 4/25/2016 3:20 PM, Christian Huitema wrote:
> > 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.
> 
> Both the "PMSI Tunnel" attribute and the "Additional PMSI Tunnel Attribute
> Flags" Extended Community are defined to be BGP transitive attributes.
This
> means that any BGP speaker that doesn't understand one of these attributes
> would just pass it along unchanged.
> 
> If a BGP speaker understands the attributes, but does not understand some
of
> the flags, it would not be correct for it to reset the flags.
> The flags might have edge-to-edge (ingress-to-egress or
> egress-to-ingress) significance, and it might not be necessary for
intermediate
> routers to understand them.  I will add a statement saying that, by
default,
> flags that are not understand SHOULD be left unchanged.  (Saying "by
default"
> leaves open the possibility that someone might configure a policy to clear
> certain bits.)
> 
> There are cases (discussed in RFCs 6514 and 7524) where the PMSI Tunnel
> attribute is modified as an UPDATE is propagated.  I'll add some text
pointing
> out that if the original PMSI Tunnel attribute had the extension flag set,
but the
> modified one does not, then the "Additional PMSI Tunnel Attribute Flags"
> Extended Community MUST be removed.

Works for me, thanks.

-- Christian Huitema