[j-nsp] Egress Protection/Service Mirroring

[adamv0025 at netconsultings.com]

> Of Saku Ytti
> Sent: Sunday, July 15, 2018 10:32 AM
> 
> Hey James,
> 
> Thanks, I was not aware of this feature. How does it compare to PIC Edge?
> Aren't both solving issue of ingress node rapidly choosing different
egress
> node from two installed options?
> 
> I think we have two secenarios:
> 
>                P2---PE2--CE2
>                |         |
> CE1 -- PE1 -- P1         |
>                |         |
>               P3---PE3---+
> 
> * CE1 primarily chooses PE2->CE2
> 
> a) If P2->PE2 goes down, we have to wait for PE1 to experience it, after
PE1
> experiences it, it can immediately redirect to PE3
> b) If PE2->CE2 goes down, PE2 should  be able to redirect to PE3
> 
> It wasn't obvious to me can this newer mechanism out-perform PIC Edge?
> 
> In case b) I think they should be equal, in both cases we don't need to
wait
> for network, the PE2 can locally choose to redirect to PE3 until it stops
> receiving packets.
> 
> But I'm not sure if this new mechanism makes a) better, does PE1 still
need
> to know about PE2 failure, or can the network itself move traffic to PE3
> before PE1 knows PE2 has failed? It might, because there is same IP, but
I'm
> not sure.
>

Yes with this one you don't need to tune IGP to propagate the info about
egress node failure all the way to ingress PEs (so the ingress PE can switch
to alternate path e.g. using PIC "core") (where this info propagation might
be slowed down significantly in multi-AS environments with BGP-LS between
AS-es).
This feature allows the P node directly adjacent to the failed egress PE
node to initiate the failover to an alternate PE, which as you can see
significantly reduces the convergence time.

But this feature solves only egress PE node failure protection (no need for
PIC "core" or IGP tuning), that is BGP-PIC Edge is still needed to protect
for egress PE-CE link failures. 
   
@James is on my todo list so maybe we can exchange notes, (I plan on using
it in RSVP-TE environment so the added complexity will be only marginal). 
Yes I've been waiting for this feature for quite some time in cisco (got
promises that maybe on SR) -maybe you can dig some of the old threads I had
with Oliver Boehmer on this
 
adam

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