hi aijun,
On Mon, Nov 29, 2021 at 07:16:18PM +0800, Aijun Wang wrote:
| Hi, Hannes:
|
| -----Original Message-----
| From: Hannes Gredler <[email protected]>
| Sent: Monday, November 29, 2021 5:27 PM
| To: Aijun Wang <[email protected]>
| Cc: 'Robert Raszuk' <[email protected]>; 'lsr' <[email protected]>; 'Les Ginsberg
(ginsberg)' <[email protected]>; 'Tony Li' <[email protected]>; 'Shraddha Hegde'
<[email protected]>; 'Peter Psenak' <[email protected]>
| Subject: Re: [Lsr] BGP vs PUA/PULSE
|
| On Mon, Nov 29, 2021 at 09:42:57AM +0800, Aijun Wang wrote:
|
| [ ... ]
|
| | Option 3: The “DOWN” detection on ABR is same as PUA/PULSE, the different
| | is how to propagate such “DOWN” information. Considering we have observed
| | that all P/PE router in other areas may be interested such information,
| | your proposal will require every P/PE router run BGP-LS, which is not the
| | aimed deploy scenarios for BGP-LS.
|
| HG> BGP-LS has been conceived to solve the very problem of providing
| HG> visibility of other
| area's link state. I fail to see what is out of scope here.
| [WAJ] Yes. But it is not for the nodes within IGP itself. It's main aim is to
feed the underlay topology information to the controller.
HG> BGP-LS has been used now beyond 3rd party controllers. I do also see you as
co-author of some drafts in LSVR
Note that a similar protocol machinery like used in LSVR can be made to
work for your use case here.
| | Then, if IGP has such capabilities, why bother BGP? What is the benefit?
|
| HG> simply put: seperation of concerns. Agreed consensus is to mostly
| HG> use the
| IGP for topology discovery and put the bulk of carrying reachability
information into BGP which gives us:
|
| 1) flow-control capabilities (=by virtue of TCP) and
| 2) furthermore operators can scale and isolate the distribution vehicle for a
given AFI/SAFI service
| using a dedicated RR infrastructure which does not mess with your bread
and butter service
| infra.
|
| IMO it is not a good idea to put (negative) reachability information back
into the IGP as you would loose this "seperation of concerns" aspect and
potentially de-stabilize your topology discovery tool and hence *all* your
bread-and-butter services.
| [WAJ] Yes. We are seeking the solution to the potential use of such
unreachable information. Current BGP solutions has not convinced me until now.
perhaps you start elaborating what *exactly* you find not convincing of the
proposed IGP/BGP split.
thanks,
/hannes
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