Re: [GROW] draft-iops-grow-bgp-session-culling-00

[<[e-mail]>]

> From: Job Snijders [mailto:[e-mail]]
> 
 > On Tue, Mar 14, 2017 at 02:28:56PM +0000, [e-mail] wrote:
 > > > From: GROW [mailto:[e-mail]] On Behalf Of heasley
 > > >
 > >  > Mon, Mar 13, 2017 at 02:07:21AM +0100, Alejandro Acosta:
 > >  > > What do you think in including also some suggestions when bringing up
 > >  > > the BGP sessions?.  Sometimes it´s good idea to bring them up one by one
 > >  > > or something like that, the idea is to make the device to fill out the
 > >  > > forwarding table, create cache, perform ARP lookups, ND, and so on. To
 > >  > > bring up all the session at once many times is not that good.
 > >  >
 > >  > I'd expect this to prolong and exacerbate the 'path hunting', while the
 > >  > min-advert-timer might help to squelch it if all sessions are enabled
 > >  > at the same time - after the IGP settles, which is automatic in some
 > >  > impl..
 > >  >
 > >  > randy, link to path hunting paper?  i can't seem to find it.
 > >
 > > For the BGP shut, in section 2.1. " Voluntary BGP Session Teardown
 > > Recommendations" you could propose or at least reference BGP Graceful
 > > shutdown https://tools.ietf.org/html/draft-ietf-grow-bgp-gshut-06
 > > In very short, it initiates the path hunting for the backup BGP path,
 > > _before_ the withdraw of the nominal path. Tests have shown that 0
 > > packet loss is achievable (assuming that within the AS, tunneling is
 > > used in order to avoid micro-loops during iBGP convergence). But if
 > > one is not targeting 0 packet loss, which is typically the case in the
 > > Internet ecosystem, there is no requirement for tunneling.
 > >
 > > In short, over eBGP, routes to be withdrawned are tagged with a "well
 > > known" community, in order to be de-preferred on the receiving side.
 > >
 > > Some vendors have automated this. But one may also do it manually
 > > using BGP policies.
 > 
 > I appreciate the effort and thought that has gone into gshut, but I am
 > not aware of actual deployments and as scuh certainly cannot vouch for
 > using this method as a 'best current practise'. it may be a 'future best
 > practise' - but that is not now.

Referencing does not necessarily imply recommending as BCP.

On a side note, I'd be interesting to know why reducing the impact of the maintenance using gshut is not considered as worth it, while it is for culling. Especially since the benefit of the latter is 90 second (and configurable)  while the former is minutes (and not configurable).

Kind regards,
--Bruno

 > Kind regards,
 > 
 > Job

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