Re: [Teas] New Version Notification for draft-wd-teas-ietf-network-slice-nbi-yang-03.txt

Tarek Saad <> Wed, 14 July 2021 04:25 UTC

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From: Tarek Saad <>
To: "Ogaki, Kenichi" <>, "" <>
Thread-Topic: New Version Notification for draft-wd-teas-ietf-network-slice-nbi-yang-03.txt
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Subject: Re: [Teas] New Version Notification for draft-wd-teas-ietf-network-slice-nbi-yang-03.txt
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Hi Ogaki,

Thanks for the review. Some possible answers below inline, see [TS]..

On 7/12/21, 3:13 AM, "Teas" <> wrote:

Hi Authors and All,

We have some questions how to proceed this work.

1. How should we create a new solution where the solution is similar to an existing solution?
 As Dhruv, co-author of both drafts, should know well, the many functionalities of this nbi are same as those of actn-vn-yang. As described in B.1, we agree that actn-vn-yang is only focusing on ACTN and this nbi is technology agnostic.
However, draft-ietf-teas-ietf-network-slices definitely addresses the applicability of ACTN. So, this nbi should at least import actn-vn-yang and refer the nodes defined in actn-vn-yang?
I'm not sure how to create a new solution for such a case.

[TS]: ACTN is one toolkit that may be used realize network slices. The main network slice I-D.draft-ietf-teas-ietf-network-slices references it as an option (in section 6.2).

“   While the ACTN framework is a generic VN framework that can be used
   for VN services beyond the IETF network slice, it also a suitable
   basis for delivering and realizing IETF network slices.
This NBI YANG data model is not dependent of the ACTN toolkit an hence does not require import the module actn-vn-yang.

2. Solution comparison is non-sense before the completion of framework.
 Appendix. B compares this nbi with the other existing work. However, the criteria of the comparison is unclear since the framework, requirement/architecture, is not completed.
If we can say anything with no criteria, the current actn-vn-yang defines VN compute functionality and this nbi doesn't have. Although the framework draft may not explicitly require this, the other SDOs developing their own slicing technologies require/define this functionality as the feasibility check, and also expect to the other SDOs, e.g. 3GPP TS 28.531 5.1.6, 5.1.21 and NFV IFA 013 7.3.3.

[TS]: the current version of this I-D attempts to address the NBI requirements already identified in I-D.draft-ietf-teas-ietf-network-slices - although it may not currently have exhaustive coverage in this revision. Indeed, the current data model allows to map VPN traffic (identified using several options) onto the created NS connectivity as means to realize a network slice.

Tarek (as a co-author)

3. Others
sec. 6.3.
We cannot understand NSE examples in 6.3. As discussed on "[Teas] network Slice Endpoint in draft-ietf-teas-ietf-network-slice-definition-00" thread, we wonder if it seems to reach the rough consensus that the demarcation point of a slice between customer and provider is the boundary of CE-PE, i.e. AC.
If correct, why Figure 4's NSE is PE and Figure 5's NSE is CE?
Someone said NSE must be controllable from NSC in the sense of SLO/SLE. So, is this CE controllable from NSC?
3GPP TS 28.541 6.3.17 EP_Transport is referred in 6.3, but our understanding is different. EP_Transport was introduced with the discussion paper, "S5-203253 TD proposal to add transport endpoint in NRM.doc", and this paper describes Cell Site Router and Border Router as the transport network edge, i.e. PE, and, Application endpoint and logical transport interface as the RAN/CN slice subnet endpoint which means CE's interface.
In this case, NSC cannot control this CE in the context of the following description in sec. 6, for example.
 "The "ns-endpoint" is an abstract entity that represents a set of matching rules applied to an IETF network edge device"

When we refer the other SDO's document, the interworking between SDOs may fail if we don't understand correct.

sec. 6.
The usage of "ns-tag" is unclear.

All the best,

-----Original Message-----
From: Teas <> On Behalf Of
Sent: Friday, July 9, 2021 9:06 PM
To: Wubo (lana) <>;
Subject: Re: [Teas] New Version Notification for draft-wd-teas-ietf-network-slice-nbi-yang-03.txt

Hi Bo, all,

Thank you for sharing this updated version.

I'm supportive of this work, but I think we have a fundamental point to clarify: the document is currently missing data nodes that makes a slice, a slice!

If we don't have such data nodes, the current module can be used to provision any form of connectivity. If we omit the "ns-" prefix, the module can be used for provisioning the connectivity of VoIP, multicast, etc. services. That’s actually good (as the applicability scope is wider) but we need also to think about network slice specifics.

I have touched on some of these points in a review I shared with you back in 02/21, but unless I'm mistaken I don't think it was addressed:

Below an extract of my main comments:

(1) A proposal to rationalize the discussion and ease progressing the spec is to clearly call that a network slice can be defined as a collection of at least three components: (1) connectivity component, (2) storage component, and (3) compute component. Having a provision for this since early stages of the model will ease grafting other components of an IETF slice easily, but also allows to avoid having a linear model.

(2) For the connectivity part, the following items are important to cover as well:
* Traffic steering and advanced services: a slice may require the invocation of service functions (firewall, for example) in a given order. These policies have to be captured in the slice request. This is also useful when the customer request that its slice should not cross some networks or not span some regions.
* What to do for out of profile traffic: See the traffic conformance discussion in RFC7297.
* Activation means: may need to be included in a slice definition. Think about a slice that can be implemented as a VPN service. Such service may require the activation of a given routing protocol between a CE and a PE, otherwise the service won’t be offered.
* Invocation means: Think about a multicast service that requires IGMP/MLD and so on.
* Notification means: these are important for service assurance and fulfillment purposes.

(3) The model seems to be inspired from the opsawg vpn I-Ds (network-access structure, for example). That's great and appreciated, but I would formalize that by using I-D.ietf-opsawg-vpn-common for data nodes such as connectivity-type, endpoint-role, status-params, etc.

(4) One last comment, I still don't get what is an "underlay IETF network".

Thank you.


> -----Message d'origine-----
> De : Teas [] De la part de Wubo (lana)
> Envoyé : vendredi 9 juillet 2021 12:18 À : Cc :
> Objet : Re: [Teas] New Version Notification for
> draft-wd-teas-ietf- network-slice-nbi-yang-03.txt
> Dear WG and chairs,
> The draft has been aligned with changes in the IETF Network Slice
> framework WG I-D.
> The Authors believe that it has been maturing with the inputs from the
> WG, and can be evaluated as a candidate for WG adoption.
> Diff:
> slice-nbi-yang-03
> Best regards,
> Bo (on behalf of the co-authors)
> -----邮件原件-----
> 发件人: []
> 发送时间: 2021年7月9日 17:32
> 收件人: Wubo (lana) <>; Dhruv Dhody
> <>; Liuyan Han <>; Reza
> Rokui <>; Tarek Saad <>
> 主题: New Version Notification for draft-wd-teas-ietf-network-slice-
> nbi-yang-03.txt
> A new version of I-D, draft-wd-teas-ietf-network-slice-nbi-yang-
> 03.txt
> has been successfully submitted by Bo Wu and posted to the IETF
> repository.
> Name:         draft-wd-teas-ietf-network-slice-nbi-yang
> Revision:     03
> Title:                A Yang Data Model for IETF Network Slice NBI
> Document date:        2021-07-09
> Group:                Individual Submission
> Pages:                45
> URL:  
> network-slice-nbi-yang-03.txt
> Status:
> network-slice-nbi-yang/
> Htmlized:
> ietf-network-slice-nbi-yang
> Diff: 
> ietf-network-slice-nbi-yang-03
> Abstract:
>    This document provides a YANG data model for the IETF Network Slice
>    Controller (NSC) Northbound Interface (NBI).  The model can be used
>    by a IETF Network Slice customer to request configuration, and
>    management IETF Network Slice services from the IETF NSC.
> The IETF Secretariat
> _______________________________________________
> Teas mailing list


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