Re: [GROW] draft-ietf-grow-bgp-gshut status?

[<[e-mail]>]

Thanks for the useful feedback.

--Bruno

 > -----Original Message-----
 > From: Ben Maddison [mailto:[e-mail]]
 > Sent: Wednesday, March 15, 2017 4:23 PM
 > To: Job Snijders; DECRAENE Bruno IMT/OLN
 > Cc: [e-mail]
 > Subject: RE: [GROW] draft-ietf-grow-bgp-gshut status?
 > 
 > I would be very happy with that outcome.
 > We've been using this for ages, and would like to see it work more widely in our adjacent
 > networks.
 > 
 > Although not truly a fix for the transitivity problem, when we match on gshut from a peer, in
 > addition to setting a lower-than-usual LP, we also append no-export, which prevents gshut-
 > ed prefixes from leaking at all.
 > I've never been hugely worried about the security consequences otherwise.
 > 
 > Cheers,
 > 
 > Ben Maddison
 > 
 > Director
 > Workonline Communications (Pty) Ltd
 > 
 > Office:     [phone]
 > Mobile:   [phone]
 > Email:      [e-mail]
 > SIP:          [e-mail]
 > 
 > 
 > 
 > 
 > -----Original Message-----
 > From: GROW [mailto:[e-mail]] On Behalf Of Job Snijders
 > Sent: Wednesday, March 15, 2017 4:54 PM
 > To: [e-mail]
 > Cc: [e-mail]
 > Subject: Re: [GROW] draft-ietf-grow-bgp-gshut status?
 > 
 > Hi Bruno,
 > 
 > On Wed, Mar 15, 2017 at 02:00:37PM +0000, [e-mail] wrote:
 > > > From: GROW [mailto:[e-mail]] On Behalf Of Job Snijders
 > > > > Sent: Wednesday, March 15, 2017 2:11 PM
 > > >
 > > > I noticed that
 > > > https://tools.ietf.org/html/draft-ietf-grow-bgp-gshut-06
 > > > expired two years ago. Can anyone offer some insight why it lapsed?
 > >
 > > In order to signal the graceful shutdown over the EBGP session, gshut
 > > uses a "well-know" BGP community. Compared to using a protocol
 > > extension, this allows a vanillia sender/receiver to handle the
 > > information using a regular BGP policy.
 > > So far so good. This is specified, implemented both with BGP policy
 > > and automated by some routers, tested (both options).
 > >
 > > Now, for some deployments, the use of a non-transitive community offer
 > > a better assurance that the community has indeed be originated by the
 > > connected eBGP peer. The issue is that currently there is no
 > > implementation of non-transitive well-known communities.
 > > draft-ietf-idr-reserved-extended-communities is a short draft to
 > > define non-transitive well-known communities. It proposed to re-use an
 > > "existing" non-transitive extended community, defined for four-octets
 > > AS: draft-ietf-idr-as4octet-extcomm-generic-subtype. But it turns out
 > > that this latter draft did not progress and has recently been replaced
 > > by BGP large community. The later do no support non-transitive
 > > community.
 > >
 > > So after waiting for some years for
 > > draft-ietf-idr-as4octet-extcomm-generic-subtype, this path has just
 > > been closed. As of today, the possible options seems:
 > >
 > > - forget about non-transitive community. In particular as during the
 > > BGP large community discussions, the requirement for non-transitive
 > > community has been discussed and explicitly called as not needed. So
 > > let's listen to this and do the same.
 > 
 > I'd like to add a small nuance: For the use case of large communities, non-transitivity was
 > considered an undesirable property.
 > 
 > To be honest, if the 'gshut' community 'escapes' the adjacent ASN for which it was intended,
 > what is the worst that can happen? That BGP speakers somewhere in the DFZ consider the
 > path less desirable? This aligns with what is expected to happen in the near future anyway:
 > the bgp session will be torn down and the path will cease to exist.
 > 
 > In the case where no shutdown event follows (the gshut community is used as a traffic
 > engineering trick), it kind of goes in the same category as intermediat networks prepending
 > ASNs to the AS_PATH to make it less desirable, or fiddling with origin. If I were to consider
 > "permanent use" of the gshut community a violation of my agreement with the adjacent
 > network, this would be easy enough to monitor for and subsequently resolve at layer-8.
 > 
 > > - have draft-ietf-idr-reserved-extended-communities use a different
 > > extended community type. This is easy to write, but if this does not
 > > get implemented, the value is limited/null.
 > 
 > I concur. A similar consideration could be made whether gshut deserves its own path
 > attribute or not.  Usually the nice thing about well known rfc 1997 communities is their
 > rapid implementation and deployability.
 > 
 > > > What implementatations exist? A fellow operator told me that IOS,
 > > > IOS XE has support for graceful shutdown, are there others?
 > >
 > > Same information on my side.  With the restriction that those
 > > implementations only implement the transitive community.
 > 
 > ack.
 > 
 > I'm somewhat inclined to proceed with the gshut concept as a well-known transitive rfc
 > 1997 community. What do others think?
 > 
 > Kind regards,
 > 
 > Job
 > 
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 > GROW mailing list
 > [e-mail]
 > https://www.ietf.org/mailman/listinfo/grow

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