[netmod] Retrieving Information Pointed by leafref

"Xufeng Liu" <xufeng.liu.ietf@gmail.com> Fri, 06 October 2017 21:12 UTC

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From: Xufeng Liu <xufeng.liu.ietf@gmail.com>
To: netconf@ietf.org, 'NetMod WG' <netmod@ietf.org>
Date: Fri, 06 Oct 2017 17:11:52 -0400
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Subject: [netmod] Retrieving Information Pointed by leafref
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During the design team discussion for TE and MPLS YANG modeling, we have
received a request from implementers: How to minimize the number of
NETCONF/RESTCONF RPCs to improve operation efficiency? Especially for the
case when the operator or client software needs to retrieve the object
contents pointed by a leafref.

For example, given the following simplified TE tunnel model,

+--rw te

    +--rw explicit-paths

    |  +--rw explicit-path* [name]

    |     +--rw name                      string

    |        +--rw explicit-route-object* [index]

    |           +--rw index                   uint32

    |           +--rw explicit-route-usage?   identityref

    +--rw tunnels

    |  +--rw tunnel* [name]

    |  |  +--rw name                   string

    |  |  +--rw paths

    |  |  |  +--rw path* [name]

|  |  |     +--rw explicit-path?  ->


when the client tries to retrieve a tunnel's information based on the tunnel
name, the "get" operation returns a list of leafref's pointing to the paths
of the tunnel. The client needs to issue at least one more "get" operation
to retrieve the path information about the given tunnel. The request is to
combine these two operations into one.

In the RDBMS SQL world, "join" can be used when SQL "select" is performed,
but NETCONF/YANG currently does not have this capability.

We'd like to ask whether such a request is considered reasonable.

If the request is reasonable, the next question is how to proceed. This
seems to be a protocol issue rather than YANG modeling issue. Is it
acceptable to add a new operation to achieve such a <get-data> operation
with expanded leafref's?

Comments and suggestions are appreciated.


- Xufeng