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

[<[e-mail]>]

> 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.

Regards,
--Bruno
 
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