Re: [I2nsf] [yang-doctors] 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 17:22 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: "Acee Lindem (acee)" <acee@cisco.com>, Yoav Nir <ynir.ietf@gmail.com>, Andy Bierman <andy@yumaworks.com>
Cc: "i2nsf@ietf.org" <i2nsf@ietf.org>, "yang-doctors@ietf.org" <yang-doctors@ietf.org>, Linda Dunbar <linda.dunbar@huawei.com>
Date: Mon, 08 Apr 2019 19:22:35 +0200
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Subject: Re: [I2nsf] [yang-doctors] 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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On Mon, 2019-04-08 at 15:18 +0000, Acee Lindem (acee) wrote:
> 
> On 4/8/19, 10:55 AM, "yang-doctors on behalf of Ladislav Lhotka" <
> yang-doctors-bounces@ietf.org on behalf of lhotka@nic.cz>; wrote:
> 
>     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
> 
> For iana-routing-types (RFC 8294), we just used enums with the IANA assigned
> values. We went back and forth with identities but settled on this when 

If the number is only the "value" parameter of each enum, then one is still
restricted to the assigned values (and mnemonic enum names in JSON and XML
representations). The trick with uint8/16 as the other union member allows for
using the numeric value in the protocol, and for both assigned and unassigned
values.

Lada

> another SDO said they'd only use our model if we have the actual values in an
> enum. For these types, nobody has complained. 
> 
> https://www.rfc-editor.org/rfc/rfc8294.txt
> 
> Thanks,
> Acee
> 
> 
>     
>     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
>     >>>  
>     >>> _______________________________________________
>     >>> yang-doctors mailing list
>     >>> yang-doctors@ietf.org <mailto:yang-doctors@ietf..org>
>     >>> https://www.ietf.org/mailman/listinfo/yang-doctors <
> https://www.ietf.org/mailman/listinfo/yang-doctors>
>     >> Mahesh Jethanandani
>     >> mjethanandani@gmail.com <mailto:mjethanandani@gmail.com>
>     >> 
>     >> 
>     >> 
>     >> _______________________________________________
>     >> yang-doctors mailing list
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>     >> https://www.ietf.org/mailman/listinfo/yang-doctors <
> https://www.ietf.org/mailman/listinfo/yang-doctors>
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>     
>     -- 
>     Ladislav Lhotka
>     Head, CZ.NIC Labs
>     PGP Key ID: 0xB8F92B08A9F76C67
>     
>     _______________________________________________
>     yang-doctors mailing list
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>     https://www.ietf.org/mailman/listinfo/yang-doctors
>     
> 
-- 
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67