[j-nsp] Segment Routing Real World Deployment (was: VPC mc-lag)

[adamv0025 at netconsultings.com]

> Of Mark Tinka
> Sent: Sunday, July 08, 2018 9:24 AM
> 
> 
> 
> On 7/Jul/18 23:24, Saku Ytti wrote:
> 
> > All these protocols have hello timers, LDP, ISIS, RSVP, BGP. And each
> > of them you'd like to configure to trigger from events without delay
> > when possible, instead of relying on timers. Indeed you can have BGP
> > next-hop invalidated the moment IGP informs it, allowing rapid
> > convergence.
> 
> For several years now, we've been happy with BFD offering this capability,
> primarily to IS-IS.
> 
> In my experience, as long as IS-IS (or your favorite IGP) is stable, upper
level
> protocols will be just as happy (of course, notwithstanding environmental
> factors such as a slow CPU, exhausted RAM, DoS attacks, link congestion,
> e.t.c.).
> 
Hold on gents, 
You are still talking about multi-hop TCP sessions, right? Sessions that
carry information that is ephemeral to the underlying transport network -why
would you want those session ever go down as a result of anything going on
in the underlying transport network -that's a leaky abstraction , not good
in my opinion.
You just reroute the multi-hop control-plane TCP session around the failed
link and move on, failed/flapping link should remain solely a data-plane
problem right? 
So in this particular case the VC label remains the same no matter that
transport labels change in reaction to failed link.
The PW should go down only in case any of the entities it's bound to goes
down be it a interface or a bridge-domain at either end (or a whole PE for
that matter) -and not because there's a problem somewhere in the core. 

adam

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