Re: [spring] [Detnet] 答复: IETF-111 SPRING presentation on sr-redundancy-protection

Gyan Mishra <hayabusagsm@gmail.com> Tue, 27 July 2021 06:48 UTC

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From: Gyan Mishra <hayabusagsm@gmail.com>
Date: Tue, 27 Jul 2021 02:47:52 -0400
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To: gregory.mirsky@ztetx.com
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Hi Greg

Redundancy Protection positioned for both  SRv6  and SR-MPLS and can
address all use P2P cases extending SR functionality.  That is the new goal
of the draft.

At this time DETNET is out of scope and we will update the draft to reflect.

>From a DETNET perspective my thoughts are that excluding P2MP DETNET
requirements as far as the forwarding and service sub layer it is possible
that redundancy protection could meet the DETNET requirements if you think
of the Replication and Merge SIDs as service SIDs acting at the DETNET
service sub layer with SRH TLV  S label set it is possible.  I think the
lines are more blurred with SRv6 trying to fit into the DETNET service and
forwarding sub layers but I think it’s still possible when you think of the
two new redundancy protection SIDs are treated as service SIDs sitting at
the DETNET service sub layer.

Kind Regards

Gyan


On Tue, Jul 27, 2021 at 12:16 AM <gregory.mirsky@ztetx.com> wrote:

> Hi Fan,
>
> thank you for the detailed explanation of the author's view of the scope
> of the draft. As the proposed mechanism is being positioned as a generic
> for SRv6, it seems logical that it addresses all the use cases. That, in my
> opinion, would include p2p and p2mp SR policies and DetNet in SR with IPv6
> data plane. Would you agree?
>
>
> Regards,
>
> Greg Mirsky
>
>
> Sr. Standardization Expert
> 预研标准部/有线研究院/有线产品经营部 Standard Preresearch Dept./Wireline Product R&D
> Institute/Wireline Product Operation Division
>
>
>
> E: gregory.mirsky@ztetx.com
> www.zte.com.cn
> Original Mail
> *Sender: *Yangfan(IPStandard)
> *To: *Balázs Varga A;draft-geng-spring-sr-redundancy-protection@ietf.org;
> *CC: *spring;detnet@ietf.org;
> *Date: *2021/07/26 14:09
> *Subject: **[Detnet] 答复: IETF-111 SPRING presentation on
> sr-redundancy-protection*
> _______________________________________________
> detnet mailing list
> detnet@ietf.org
> https://www.ietf.org/mailman/listinfo/detnet
>
> Hi Balazs,
>
>
>
> Thank you for your comments.
>
> As what Gyan mentioned during the presentation, this draft redefines
> redundancy protection as a general protection mechanism designed for SR
> network. Firstly, it is a general mechanism can be used in many uses cases,
> not only DetNet use case. Secondly, it applies to SR network, not a general
> IP or MPLS data plane solution which Detnet requires. Since the scope is
> changed, I don’t think redundancy protection is necessary to follow DetNet
> architecture.
>
> If redundancy protection is not a DetNet mechanism, I don’t think it
> should cover both P2P and P2MP services.
>
> We are happy to address the comments that relates to redundancy protection
> in next revision.
>
>
>
> Thanks.
>
> Fan
>
>
>
> *发件人:* Balázs Varga A [mailto:balazs.a.varga@ericsson.com]
> *发送时间:* 2021年7月27日 4:49
> *收件人:* draft-geng-spring-sr-redundancy-protection@ietf.org
> *抄送:* spring <spring@ietf.org>rg>; detnet@ietf.org
> *主题:* IETF-111 SPRING presentation on sr-redundancy-protection
>
>
>
> Hi,
>
>
>
> As time not permitted comments during the SPRING meeting, major comments
> regarding the
>
> redundancy protection presentation:
>
>
> https://datatracker.ietf.org/meeting/111/materials/slides-111-spring-sr-for-redundancy-protection-00
>
>
>
> 1, General: despite the reference to DetNet this draft is not compliant
> with Figure 1 of RFC8655 (DetNet Architecture)
>
> 2, Slide-9: DetNet provides both p2p and p2mp services. This draft only
> p2p, so many DetNet use cases cannot be supported
>
> 3, Slide-9: there were many DetNet related comments on the list. Only some
> were addressed in the latest version of the draft.
>
>
>
> Thanks & Cheers
>
> Bala’zs
>
>
>
>
>
>
>
>
>
>
>
>
>
> *From:* Jeffrey (Zhaohui) Zhang <zzhang@juniper.net>
> *Sent:* Monday, July 19, 2021 11:44 PM
> *To:* Yangfan (IP Standard) <shirley.yangfan@huawei.com>om>; Balázs Varga A <
> balazs.a.varga@ericsson.com>gt;;
> draft-geng-spring-sr-redundancy-protection@ietf.org
> *Cc:* spring <spring@ietf.org>rg>; detnet@ietf.org
> *Subject:* RE: SR and DetNet, draft on sr-redundancy-protection
>
>
>
> Hi Fan,
>
>
>
> Catching up on this late …
>
>
>
> You said:
>
>
>
> Ø  Triggered by the discussions in SPRING, I think we can define
> redundancy segment and merging segment as a functional segment without
> routing and topological semantics, and use different segment for the
> routing purpose. Thus, redundancy segment and merging segment are segments
> with pure service semantics and don’t violate the sub-layers definition in
> DetNet architecture.
>
>
>
> Are you alluding to using replication segment for the routing/forwarding
> purpose? In my late response to an old email of yours that I just sent (
> https://mailarchive.ietf.org/arch/msg/spring/YyEb8kGgtXxITZaIGyxynp9wh9s/),
> I also said “the redundancy/merging functionality can be considered as an
> overlay service that makes use of replication underlay service” – so maybe
> we’re converging?
>
>
>
> Thanks.
> Jeffrey
>
>
>
> *From:* spring <spring-bounces@ietf.org> *On Behalf Of *Yangfan (IP
> Standard)
> *Sent:* Saturday, June 12, 2021 2:07 AM
> *To:* Balázs Varga A <balazs.a.varga@ericsson.com>om>;
> draft-geng-spring-sr-redundancy-protection@ietf.org
> *Cc:* spring <spring@ietf.org>rg>; detnet@ietf.org
> *Subject:* [spring] 答复: SR and DetNet, draft on sr-redundancy-protection
>
>
>
> *[External Email. Be cautious of content]*
>
>
>
> Hi Bala’zs,
>
> Thank you for your comments. Please see my reply inline starts with Fan1>>
>
>
>
> *发件人:* Balázs Varga A [mailto:balazs.a.varga@ericsson.com
> <balazs.a.varga@ericsson.com>]
> *发送时间:* 2021年6月11日 21:12
> *收件人:* draft-geng-spring-sr-redundancy-protection@ietf.org
> *抄送:* detnet@ietf.org; spring <spring@ietf.org>
> *主题:* SR and DetNet, draft on sr-redundancy-protection
>
>
>
> Hi Authors,
>
>
>
> thanks for the update of your draft, to clarify the proposed mechanism of
>
> redundancy protection.
>
>
>
> I have concerns regarding this draft as (1) the SRv6 approach does not
> follow the
>
> DetNet architecture, and (2) repeats functionalities that are provided by
> the DetNet
>
> service sub-layer but with serious limitations.
>
>
>
> (1) DetNet has defined two sub-layers: the service sub-layer and the
> forwarding
>
> sub-layer. The service sub-layer is responsible for service protection and
> the
>
> forwarding sub-layer provides forwarding paths and resource allocation on
> top of
>
> them for the DetNet flows. DetNet specifications allow to use any
> technology in
>
> the forwarding sub-layer, including Segment Routing.
>
>
>
> The SRv6 approach described in
> "draft-geng-spring-sr-redundancy-protection" breaks
>
> the clear concept of the sub-layers by mixing them up. It contradicts to
> several
>
> points at least to RFC8655 (DetNet Architecture), RFC8938 (Data Plane
> Framework)
>
> and RFC8964 (DetNet MPLS Data Plane).
>
>
>
> Fan1>> Segment routing extends IPv6 by introducing SRH extension header
> and SID programming. From the perspective of SID list in SRH, it provides
> the explicit route to IPv6 data plane in forwarding sub-layer. From the
> perspective of SID programming and Endpoint behaviors, it provides the
> packets replication and elimination in service sub-layer. So Redundancy
> segment could include the routing characteristic and service indication at
> the same time. Similar happens to Merging segment. I think this is why you
> called it breaking the concepts of two sub-layers and mixing them up.
>
> Triggered by the discussions in SPRING, I think we can define redundancy
> segment and merging segment as a functional segment without routing and
> topological semantics, and use different segment for the routing purpose.
> Thus, redundancy segment and merging segment are segments with pure service
> semantics and don’t violate the sub-layers definition in DetNet
> architecture.
>
> Besides, in RFC8655 4.1.2 DetNet data-plane overview, it says,
>
> This separation of DetNet sub-layers, while helpful, should not be
> considered a formal requirement. For example, some technologies may violate
> these strict sub-layers and still be able to deliver a DetNet service
>
> I think SRv6 could be acceptable based on this.
>
>
>
> In addition, I guess where to encapsulate meta data could be one concern.
> According to DetNet, they should be identified and encapsulated at SR edge
> node. We plan to include both possibilities in next update. To carry them
> at SR edge node would be recommended as the first choice, and thus does not
> violate DetNet architecture. Right now I still want to keep the possibility
> for redundancy segment to add meta data for some corner case.
>
>
>
> So far, I didn’t realize there are other points contradict to DetNet RFCs.
> We are very happy to discuss them.
>
>
>
> (2) The motivation for "draft-geng-spring-sr-redundancy-protection" is not
> clear especially
>
> as the SRv6 approach seems to be repeating DetNet service sub-layer
> functionalities; however,
>
> with a limited set of functionalities without any clear benefits.
>
> Fan1>> as what I said in previous email to Joel, redundancy protection
> comes from service protection specified in DetNet, but more focus on how to
> do it when Segment Routing is introduced to MPLS and IPv6. Currently,
> DetNet defines IP and MPLS data planes for DetNet in RFC8939 and RFC8964.
> There is segment routing consideration in RFC8964, but not in RFC8939. In
> our draft, we try to focus on definition in SRv6, and for MPLS-SR just
> obeys the specifications in RFC8964. It is clear that we are not repeating
> DetNet service sub-layer functionality, but to fill the gap between RFC8939
> and SRv6. If WG thinks the SR-MPLS sections are redundant, we can take
> reference from RFC8964 for simplicity in next update.
>
> I don’t think there is no clear benefit what segment routing brings to
> IP(v6). By using the redundancy protection mechanism, DetNet services
> running over SRv6 don’t rely on IP+UDP/TCP tuple to provide PREOF. The
> authors believe this draft is meaningful.
>
> Thank you for bring this topic into DetNet and SPRING. I take it as
> whether SRv6 is worth to be specified separately besides the existing
> DetNet data plane RFCs. It is a valid and important question for DetNet, we
> may need some guide from the WG.
>
> My 2 cents.
>
>
>
> Best regards,
>
> Fan
>
>
>
>
>
> Cheers
>
> Bala'zs
>
>
>
> Juniper Business Use Only
>
>
> _______________________________________________
> detnet mailing list
> detnet@ietf.org
> https://www.ietf.org/mailman/listinfo/detnet
>
-- 

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*Gyan Mishra*

*Network Solutions A**rchitect *

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