Re: [i2rs] Mail regarding draft-ietf-i2rs-yang-l2-network-topology

Qin Wu <> Thu, 09 July 2020 07:05 UTC

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From: Qin Wu <>
To: Stephen Cheng <>, "" <>, "" <>
CC: "Dongjie (Jimmy)" <>
Thread-Topic: Mail regarding draft-ietf-i2rs-yang-l2-network-topology
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Date: Thu, 09 Jul 2020 07:04:49 +0000
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Subject: Re: [i2rs] Mail regarding draft-ietf-i2rs-yang-l2-network-topology
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Hi Stephen:

发件人: Stephen Cheng []
发送时间: 2020年7月9日 12:53
主题: Mail regarding draft-ietf-i2rs-yang-l2-network-topology

Dear authors,

I have a number of questions regarding this L2 topology YANG.

  1.  Does draft-ietf-i2rs-yang-l2-network-topology support the modelling of a termination point that maps to a VLAN sub-interface?
This capability would facilitate the creation of a topology stack for the following use cases:

     *   Mapping a ietf-l3-topology TP over a vlan sub-interface
In this case a TP in ietf-l3-topology instance would be supported by a VLAN sub-interface TP in the l2-topology
     *   Mapping different VLAN IDs in a L2 ports to different services

                                                               i.      For example, on a particular L2 port, VLAN 23 might be an attachment circuit for VPLS #78, where as VLAN 99 might be an attachment circuit for L3VPN #999

If draft-ietf-i2rs-yang-l2-network-topology does not have the capability to model VLAN sub-interface as a TP, is there a different way for draft-ietf-i2rs-yang-l2-network-topology to support the above use cases?

[Qin]: Good question, this could be documented in another new draft.  Also see 4.4.2 (Underlay Hierarchies and Mappings) of RFC8345 for guideline.

  1.  The VLAN sub-interface YANG ( being developed has some overlap with draft-ietf-i2rs-yang-l2-network-topology. It would be good if there would be better alignment between the two:
     *   Use similar definition/fields where possible; even better use shared grouping definition

                                                               i.      For example outer-tag and inner-tag

     *   VLAN sub-interface YANG ( flexible encapsulation supports symmetric and asymmetric rewrites, which does not appear to be supported by draft-ietf-i2rs-yang-l2-network-topology.
            [Qin]: Both drafts import ieee802-dot1q-types, this is how we align with each other. The big difference between the model proposed by both drafts is one is device model, the other is network model.

  1.  Consider the scenario where a domain controller implementing draft-ietf-i2rs-yang-l2-network-topology is also implementing schema mounted ietf-interface to model the interface stacks of the managed devices:
-          Is there a mechanism in draft-ietf-i2rs-yang-l2-network-topology to associate a L2 TP with the corresponding interface entry in the schema mounted ietf-interface?
          [Qin]: This is the base model, if you want to support this complicate case, I think base model extension is needed.

  1.  For a LAG link, would the LAG TP be expected to be also represented by /nw:networks/nw:network/nw:node:termination-point/tp-id/supporting-termination-point to its membership TPs?
It would be useful to clarify for uniform implementation across different vendors.
           [Qin] Lag and member-link-tp under l2-termination-point-type choice can be used to support the case you mentioned below. See the definition of Lag and member-link for more details.
Aslo See section 4.4.6 Multihoming and link aggregation of RFC8345 for guideline.
Thank you.

Warm regards,
Stephen Cheng
Aviat Networks