Robert, Comments inline
Yours Irrespectively, John From: spring [mailto:[email protected]] On Behalf Of Robert Raszuk Sent: Monday, May 23, 2016 4:14 PM To: Adrian Farrel Cc: idr wg; [email protected] Subject: Re: [spring] [Idr] New draft for data center gateways Dear Authors, Question 1: Assume that prefix X has been advertised with tunnel attribute as described in the draft with both GW1 and GW2 entry points to Egress DC site. So remote GW in Ingress DC site receives at least one such advertisement and as each contains both GW1 and GW2 entries it can engineer flows to those. So far so good ... but what happens when link between PE (on left side) and GW1 goes down ? BGP will after some time remove that path via all ASes, but GW2 will keep advertsing prefix X as still reachable via both GW1 and GW2 within tunnel encapsulation attribute as from his perspective nothing will be wrong. How remote GW in Ingress DC site is now supposed to know that GW1 link to PE in AS2 went down and stop pushing traffic towards it ? [JD] We were assuming that a) GW/backbone links would be advertised in BGP LS (optionally w/ EPE) and b) a GW that is disconnected from the backbone does not advertise an auto-discovery route. This will be made explicit in the next revision. - - - Question 2: What happens if all L3 DC CLOS IP Fabrics use eBGP not IGP ? [JD] We make no assumptions about what control plane is used within a DC. After all, the draft is about DC “interconnect”. (Btw, it should be spelled ‘Clos’ since it’s a person’s last name.) - - - Question 3: Is per prefix tunnel attribute where say /32 routes may be exchanges flat (ref calico approach - https://www.projectcalico.org/) really a scalable solution ? [JD] Are you simply repeating the opinion you expressed when the tunnel-encaps draft first came out, or do you have a scalability concern that hasn't already been discussed? Best, Robert. PS. Just purely as information your inter DC traffic steering problem description is easily solved already today with one level of indirection - Example: LISP. Not sure if we need additional flat protocol extensions here.
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