Re: [netconf] [netmod] pls clarify get operation

[Juergen Schoenwaelder <[e-mail]>]

Yes, both the NETCONF <get> operation and the RESTCONF GET on the
unified view of the underlying datastores have limitations and a
solution in situations where these limitations hurt is to move towards
NMDA.

/js

On Fri, Jun 28, 2019 at 08:38:38AM +0000, Rob Wilton (rwilton) wrote:
> Hi Frank,
> 
> Pre NMDA:
> 
>   *   You have a the <running> datastore, along with some others like <candidate> and <startup> that you can ignore for the purposes of this discussion.
>   *   The <running> datastore can only contains data for schema nodes that are marked as “config true” in YANG (i.e. “rw” in your tree output below).
>   *   The system may also have some operational state data that is marked as “config false” in YANG (i.e. “ro” in your tree output below).
> 
> The NETCONF <get-config> operation returns the contents of the <running> datastore.
> The NETCONF <get> operation returns the contents of the <running> datastore combined with all the operational state as well.  Filters can be applied to return a subset of the data.
> 
> Regarding your question about user created configuration vs system created configuration, it depends on whether the devices instantiates the configuration in <running> or not.  If it does, then it would be returned in <get> and <get-config> operations.  If it doesn’t then it would not.  Different vendors/devices will likely implement this in different ways.
> 
> Generally, I think that <running> should only contain the configuration explicitly configured by the operator’s systems.  But this means that there isn’t a clean way to represent system created configuration or applied configuration, unless you make a config false copy of every config true node in YANG.  This is approach that was taken by the original IETF YANG models (e.g. RFC 7223) before they were superseded by NMDA, and also the OpenConfig YANG models (but using a different structure – which also struggles to cleanly represent system created configuration data).
> 
> The NMDA architecture was written to solve this problem in a clean way without requiring duplication in the YANG data models.
> 
> Hopefully this helps clarify.
> 
> Thanks,
> Rob
> 
> 
> From: netmod <[e-mail]> On Behalf Of Fengchong (frank)
> Sent: 28 June 2019 04:29
> To: [e-mail]; [e-mail]
> Cc: Zhangwei (SS) <[e-mail]>
> Subject: [netmod] 答复: pls clarify get operation
> 
> Hi all,
> 
>      Pls clarify this question. I have been confused for a long time.
> 
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> 发件人: Fengchong (frank)
> 发送时间: 2019年6月27日 9:59
> 收件人: '[e-mail]' <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
> 抄送: Yangshouchuan <[e-mail]<mailto:[e-mail]>>; Zhangwei (SS) <[e-mail]<mailto:[e-mail]>>
> 主题: pls clarify get operation
> 
> Hi all,
> In RFC6241, get operation is defined as:
> 7.7<https://tools.ietf.org/html/rfc6241#section-7.7>.  <get>
> 
>    Description:  Retrieve running configuration and device state
> 
>       information.
> This description is too simply, so I think it should be clarified.
> 
> The case is: a data node modelled by one yang can be configured by user, but also can be created/modified by system or other protocols. If client issues get operation to retrieve this node,
>           The data is created/modified by system or other protocols SHOULD be returned?
>           For example:
>           Rib can be configured by user and also can be created by routing protocols. In RFC 8349, the rib list is defined as:
> 
> 
> 
>       +--rw ribs
> 
>          +--rw rib* [name]
> 
>             +--rw name              string
> 
>             +--rw address-family?   identityref
> 
>             +--ro default-rib?      boolean {multiple-ribs}?
> 
>             +--ro routes
> 
>             |  +--ro route*
> 
>             |        ...
> 
>             +---x active-route
> 
>             |  +---w input
> 
>             |  |  +---w v4ur:destination-address?   inet:ipv4-address
> 
>             |  |  +---w v6ur:destination-address?   inet:ipv6-address
> 
>             |  +--ro output
> 
>             |        ...
> 
>             +--rw description?      string
> 
> 
> 
>        If client issued get operation to retrieve ribs from non-NMDA device, rib instance created by routing protocols should be returned?
> 
>        Another associated question: If client issued get-config operation from non-NMDA device, only user-controlled rib instance should be returned?
> 



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-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
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