Re: [yang-doctors] [I2nsf] Need YANG Doctor reviewing the YANG module of draft-ietf-i2nsf-sdn-ipsec-flow-protection which I2NSF is about to call WGLC

Ladislav Lhotka <lhotka@nic.cz> Mon, 08 April 2019 14:55 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: Yoav Nir <ynir.ietf@gmail.com>, Andy Bierman <andy@yumaworks.com>
Cc: "i2nsf\@ietf.org" <i2nsf@ietf.org>, Linda Dunbar <linda.dunbar@huawei.com>, "yang-doctors\@ietf.org" <yang-doctors@ietf.org>
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Date: Mon, 08 Apr 2019 16:55:26 +0200
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Subject: Re: [yang-doctors] [I2nsf] Need YANG Doctor reviewing the YANG module of draft-ietf-i2nsf-sdn-ipsec-flow-protection which I2NSF is about to call WGLC
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Yoav Nir <ynir.ietf@gmail.com>; writes:

> At this point I’m wondering if it would not be a better strategy to
> avoid all enumerations of algorithms, whether they are spelled out or
> imported from draft-ietf-netconf-crypto-types, and instead use the
> numbers from the IANA registry for IPsec.
>
> That does not help us deprecate old algorithms, but it solves the
> other issue, which is what to do when a new algorithm is added to
> IPsec. We don’t want to have to publish a new i2nsf document whenever
> that happens, and if the algorithm identifier is just a number, new
> values can be added by IANA.

IMO the best option is to combine an enumeration and numbers in a union
type. We used this approach in this draft:

https://tools.ietf.org/html/draft-lhotka-dnsop-iana-class-type-yang-01

Lada

>
> Yoav
>
>> On 5 Apr 2019, at 20:42, Andy Bierman <andy@yumaworks.com>; wrote:
>> 
>> Hi,
>> 
>> I think conformance for identities is handled very poorly in YANG.
>> There is an if-feature-stmt allowed inside an identity in YANG 1.1.
>> This implies that any identity without if-feature is mandatory-to-implement.
>> 
>> If the identities are in a separate module, the server can list it as an imported module,
>> which tells the client the server does not implement any of the identities.
>> 
>> There is no standard way for the server to inform the client which identities it supports
>> for a given identityref data node.
>> 
>> The common implementation strategy is to completely ignore YANG conformance for identities
>> (as Mahesh explained). You just try setting the leaf and see if the server accepts it.
>> 
>> Andy
>> 
>> 
>> On Fri, Apr 5, 2019 at 10:33 AM Mahesh Jethanandani <mjethanandani@gmail.com <mailto:mjethanandani@gmail.com>> wrote:
>> Hi Linda,
>> 
>> 
>>> On Apr 5, 2019, at 9:51 AM, Linda Dunbar <linda.dunbar@huawei.com <mailto:linda.dunbar@huawei..com>> wrote:
>>> 
>>> Dear YANG Doctor:
>>>  
>>> We need your help in reviewing the YANG model in draft-ietf-i2nsf-sdn-ipsec-flow-protection which I2NSF WG is about to call WGLC.
>>>  
>>> In particular, we need your advice on the following issue:
>>>  
>>> draft-ietf-i2nsf-sdn-ipsec-flow-protection-04 imports from draft-ietf-netconf-crypto-types, which appears to be a generic list of algorithms.
>>> The problem is that the list in draft-ietf-netconf-crypto-types could contain algorithms that are not suitable for IPsec (such as secp192r1 for key agreement), and right now it seems to lack some older algorithms that have fallen out of fashion (3DES) but is still needed in IPsec.  
>> 
>> All the algorithms in draft-ietf-netconf-crypto-types are defined as identities. If you do not find the algorithm you are looking for in the list of defined algorithms, you can go ahead and define your own in your own draft, using the same base identity from the ietf-crypto-types module.
>> 
>>>  
>>>  
>>> Questions to the YANG Doctor:
>>> 1.       Is it better to list the IPsec specific algorithms in draft-ietf-i2nsf-sdn-ipsec-flow-protection (which is a subset of draft-ietf-netconf-crypto-types? Or to import all crypto algorithms many of which are not relevant to IPsec? What is the common practice? 
>> 
>> Importing ietf-crypto-types does not mean you have to implement every algorithm listed in the module. You can import the module and chose to implement the algorithms you want to implement, including defining any new ones.
>> 
>>> 2.      If we do import from draft-ietf-netconf-crypto-types, does it mean draft-ietf-i2nsf-sdn-ipsec-flow-protection cannot be published until draft-ietf-netconf-crypto-types is published?
>> 
>> Yes. The i2nsf draft will hit the state of MISSREF in the RFC Editor queue. But that should not prevent anyone from starting implementation of the module. As a side note, the NETCONF WG is planning on sending the crypto-types draft to IESG shortly. What you do not want is to duplicate the definition of the algorithms in your own draft.
>> 
>> HTH.
>> 
>>>  
>>>  
>>> Thank you very much, 
>>>  
>>> Linda & Yoav
>>>  
>>> _______________________________________________
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>> Mahesh Jethanandani
>> mjethanandani@gmail.com <mailto:mjethanandani@gmail.com>
>> 
>> 
>> 
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-- 
Ladislav Lhotka
Head, CZ.NIC Labs
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