Subject: [Isis-wg] ISIS in multiarea seamless MPLS

From: Saku Ytti <[email-masked]>
Date: Wed, 20 Aug 2014 23:56:10 +0300

Hi,

http://tools.ietf.org/html/draft-ietf-mpls-seamless-mpls-07
http://www.juniper.net/us/en/local/pdf/design-guides/8020013-en.pdf

URLs provide example how to implement seamless MPLS with using ISIS
between one 'core' and multiple 'aggregation' networks.

Problem is, this concept does not actually work if you connect >1
aggregation network to same border router, because border router
belonging to multiple areas would essentially merge the areas and
flood LSPs between them, reducing your scale benefits.

This is probably not really ISIS standardization issue, rather some
local proprietary hack is needed in border router to isolate the
cross-area LSPs. Or should ISIS on protocol level consider this
use-case?

Thanks,
-- 
  ++ytti

---

From: Saku Ytti <[email-masked]>
Date: Thu, 21 Aug 2014 09:43:00 +0300

RFC6822 appears to be the canonical solution to the problem? Separate
LSDB to the separate aggregation networks.

-- 
  ++ytti

---

From: Hannes Gredler <[email-masked]>
Date: Thu, 21 Aug 2014 09:16:24 +0200

not sure if 6822 is the answer - my read of it is that it primarily a vehicle
to seperate L3 routing instances from L2 (TRILL) routing instances.

as far as exisiting solution goes:

- some vendors support the notion of "several L1 LSDBs"
  in one protocol instance.
- some vendors support the notion of "several protocol instances"
  per routing-table.

both ways solve the "L1 flooding short-circuit' problem that you have
been describing below.

HTH,

/hannes

On Thu, Aug 21, 2014 at 09:43:00AM +0300, Saku Ytti wrote:
| RFC6822 appears to be the canonical solution to the problem? Separate
| LSDB to the separate aggregation networks.
| 
| On 20 August 2014 23:56, Saku Ytti <[email-masked]> wrote:
| > Hi,
| >
| > http://tools.ietf.org/html/draft-ietf-mpls-seamless-mpls-07
| > http://www.juniper.net/us/en/local/pdf/design-guides/8020013-en.pdf
| >
| > URLs provide example how to implement seamless MPLS with using ISIS
| > between one 'core' and multiple 'aggregation' networks.
| >
| > Problem is, this concept does not actually work if you connect >1
| > aggregation network to same border router, because border router
| > belonging to multiple areas would essentially merge the areas and
| > flood LSPs between them, reducing your scale benefits.
| >
| > This is probably not really ISIS standardization issue, rather some
| > local proprietary hack is needed in border router to isolate the
| > cross-area LSPs. Or should ISIS on protocol level consider this
| > use-case?