Re: [Isis-wg] comments on draft-litkowski-isis-yang-isis-cfg-01

<stephane.litkowski@orange.com> Wed, 30 July 2014 13:45 UTC

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From: <stephane.litkowski@orange.com>
To: "Osborne, Eric" <eric.osborne@level3.com>, Chris Bowers <cbowers@juniper.net>, Alia Atlas <akatlas@gmail.com>, "Derek Man-Kit Yeung (myeung) (myeung@cisco.com)" <myeung@cisco.com>, "Jeffrey (Zhaohui) Zhang (zzhang@juniper.net)" <zzhang@juniper.net>
Thread-Topic: [Isis-wg] comments on draft-litkowski-isis-yang-isis-cfg-01
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Date: Wed, 30 Jul 2014 13:45:00 +0000
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Cc: Hannes Gredler <hannes@juniper.net>, "Wunan \(Eric\)" <eric.wu@huawei.com>, "isis-wg@ietf.org" <isis-wg@ietf.org>
Subject: Re: [Isis-wg] comments on draft-litkowski-isis-yang-isis-cfg-01
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“one of the goals of any model is to reuse parts from other models”


Ø  I’m not aware of any sort of design model for the routing part … expect that it must be aligned with the core routing model. Maybe some Yang doctor’s have another view …

Yang model definition is just starting … it’s time to define such constraint if it does not exist



From: Osborne, Eric [mailto:eric.osborne@level3.com]
Sent: Wednesday, July 30, 2014 13:30
To: LITKOWSKI Stephane SCE/IBNF; Chris Bowers; Alia Atlas; Derek Man-Kit Yeung (myeung) (myeung@cisco.com); Jeffrey (Zhaohui) Zhang (zzhang@juniper.net)
Cc: Hannes Gredler; Wunan (Eric); isis-wg@ietf.org
Subject: RE: [Isis-wg] comments on draft-litkowski-isis-yang-isis-cfg-01

I’m jumping into this kinda late, so forgive me.  And of course I missed the conversation in Toronto so I’m not sure what the strong argument was for progressing this as what sounds like three separate implementations.

“Let’s finish this work, and as OSPF and ISIS model are maintained by the same core set of people, alignment will be guaranteed.”

Not to be a naysayer, but I’m skeptical that ‘guarantee’ will actually work without some teeth behind it.  Is there a framework doc or something that says “one of the goals of any model is to reuse parts from other models”, or maybe something scoped to just link-state routing or TE that says “you MUST reuse what is common”?  Without that, I’m afraid ‘guarantee’ will turn into ‘well, we tried but we gave up’.

That said, perhaps a path to homogeny is to work on three separate models in order to see what can be reused; make the three models throwaway work, at least as far as TE goes.  Does that work?



eric

From: Isis-wg [mailto:isis-wg-bounces@ietf.org] On Behalf Of stephane.litkowski@orange.com<mailto:stephane.litkowski@orange.com>
Sent: Wednesday, July 30, 2014 7:15 AM
To: Chris Bowers; Alia Atlas; Derek Man-Kit Yeung (myeung) (myeung@cisco.com<mailto:myeung@cisco.com>); Jeffrey (Zhaohui) Zhang (zzhang@juniper.net<mailto:zzhang@juniper.net>)
Cc: Hannes Gredler; Wunan (Eric); isis-wg@ietf.org<mailto:isis-wg@ietf.org>
Subject: Re: [Isis-wg] comments on draft-litkowski-isis-yang-isis-cfg-01

Hi, (adding Derek & Jeffrey)

I agree that from a theorical point of view that would be great.
By experience, it’s really hard to find the good tradeoff in term of dependencies of components, and define where we should stop in term of trying to aggregate things.
We had this discussion last week with Derek, Jeffrey, Hannes, Les and Lada, and even if there was an interest raised during the discussion for a “superset” IGP LS model (common modeling topology, …), there was also some complexity that might be introduced : so we decided at least for the moment to work on parallel and flat models.

I think at this point of the model definition this is still the good approach. Let’s finish this work, and as OSPF and ISIS model are maintained by the same core set of people, alignment will be guaranteed. When models will be almost finished, we will be able to decide if some superset models or common augmentations can be used to simplify future extensions.

Thoughts ?

From: Chris Bowers [mailto:cbowers@juniper.net]
Sent: Tuesday, July 29, 2014 22:38
To: Alia Atlas; LITKOWSKI Stephane SCE/IBNF
Cc: Hannes Gredler; Wunan (Eric); isis-wg@ietf.org<mailto:isis-wg@ietf.org>
Subject: RE: [Isis-wg] comments on draft-litkowski-isis-yang-isis-cfg-01

Stephane,

I agree with Alia that we should find the common information between ISIS and OSPF were it exists.

As a concrete example, maximum link bandwidth, maximum reservable bandwidth, and unreserved bandwidth refer to the same information independent of whether it is carried via ISIS, OSPF, or BGP-LS.  It doesn’t seem that we should be create three parallel data models to describe the same information three times.

Chris



From: Isis-wg [mailto:isis-wg-bounces@ietf.org] On Behalf Of Alia Atlas
Sent: Tuesday, July 29, 2014 3:42 PM
To: Stephane Litkowski
Cc: Hannes Gredler; Wunan (Eric); isis-wg@ietf.org<mailto:isis-wg@ietf.org>
Subject: Re: [Isis-wg] comments on draft-litkowski-isis-yang-isis-cfg-01

Hi Stephane,
On Tue, Jul 29, 2014 at 4:04 AM, <stephane.litkowski@orange.com<mailto:stephane.litkowski@orange.com>> wrote:
Hi Hannes,

> hmm can we first collect some TE related atrributes that apply both to OSPF and IS_IS before making that call ?
Based on the last discussions we had at IETF, the best solution would be to have TE attributes directly in the ISIS model in a similar way as OSPF rather than trying to define a common augmented model. I think this discussion is similar to the "superset" IGP Link State model where we did not want to go into ...

Is there a reason not to look for common groups of information where we can?  I wouldn't necessarily go for augmenting but for a common group that both ISIS and OSPF could include.

You might also look at draft-clemm-i2rs-yang-network-topo-00 .

Alia


> that one might get hairy pretty soon ... as some vendors define their leak policy as prefix, lists and some others call into execution of a policy language.
Right, the issue with policy is more global rather than just an ISIS issue ... it's not really my priority for now ...


Stephane


-----Original Message-----
From: Hannes Gredler [mailto:hannes@juniper.net<mailto:hannes@juniper.net>]
Sent: Monday, July 28, 2014 17:39
To: Wunan (Eric)
Cc: LITKOWSKI Stephane SCE/IBNF; isis-wg@ietf.org<mailto:isis-wg@ietf.org>
Subject: Re: [Isis-wg] comments on draft-litkowski-isis-yang-isis-cfg-01

hi eric, stephane,

On Wed, Jul 23, 2014 at 06:04:28PM +0000, Wunan (Eric) wrote:
[ ... ]
|    6. Missing traffic engineering ?
|
|
|
|    [SLI] Only wide metrics are there , but not traffic-eng. I was wondering
|    if TE should be part of a separate datamodel (using augmentation) and so
|    can be used for both OSPF and ISIS protocols    point to discuss
|
|    [Eric] Agree to be a separate model. That's will be better.

hmm can we first collect some TE related atrributes that apply both to OSPF and IS_IS before making that call ?


[ ... ]
|    8. Missing redistribution related cfg ?
|
|
|
|    [SLI] Route-filters are part of the core data model. But maybe we need to
|    augment stuffs    I did not look at it yet.

that one might get hairy pretty soon ... as some vendors define their leak policy as prefix, lists and some others call into execution of a policy language.


|    9. Multi-topology should allow to configure more besides ipv4-uni,
|    ipv6-uni, ipv4-multi, ipv6-multi
|
|    These are commonly used configuration which should not be omitted.
|
|
|
|    [SLI] Please provide more details on what you want.
|
|    [Eric] Multi-topology for non-standard ones. This model should allow this.

do you have a use-case for this ? - any document that you can refer to ?


/hannes
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