Re: [Bier] WG adoption call for draft-chen-bier-frr-02

Greg Mirsky <gregimirsky@gmail.com> Wed, 17 March 2021 16:46 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Wed, 17 Mar 2021 09:45:43 -0700
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To: Huaimo Chen <huaimo.chen@futurewei.com>
Cc: "bier@ietf.org" <bier@ietf.org>, BIER WG Chairs <bier-chairs@ietf.org>
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Subject: Re: [Bier] WG adoption call for draft-chen-bier-frr-02
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Hi Huaimo,
it seems that you are suggesting using IP FRR and BIER FRR in the same
domain. Is my understanding correct? Multi-layer protection in a network
may work but, in my opinion, overcomplicated network management and
operation. Would you expect that BIER FRR is more responsive to a network
failure than IP FRR? What benefits could be in such a scenario? Which
parameters, in your opinion, need to be coordinated between IP and BIER
layers? I think that if the document includes the concurrent use of IP FRR
and BIER FRR it should provide more detail on how such a scenario could be
realized.

Regards,
Greg

On Tue, Mar 16, 2021 at 10:27 AM Huaimo Chen <huaimo.chen@futurewei.com>
wrote:

> Hi Tony,
>
>     Even though there is IGP running in the network and the underlay IP
> FRR is provided, the BIER FRR seems still needed. All the BIER packets are
> forwarded using the BIFTs. They are not forwarded using the normal FIBs
> with IP FRR support.  When a failure happens in the network, the BIER
> packets will still be forwarded using the old BIFTs without considering the
> failure until the old BIFT is recomputed and updated based on the new
> network topology after the failure. During this period (from the time of
> the failure to the time at which the BIFTs are updated), the BIER packets
> may be lost.
>
> Best Regards,
> Huaimo
> ------------------------------
> *From:* Tony Przygienda <tonysietf@gmail.com>
> *Sent:* Tuesday, March 16, 2021 12:58 PM
> *To:* Huaimo Chen <huaimo.chen@futurewei.com>
> *Cc:* Michael Menth <menth@uni-tuebingen.de>de>; bier@ietf.org <bier@ietf.org
> >
> *Subject:* Re: [Bier] WG adoption call for draft-chen-bier-frr-02
>
> we need a framework here ;-)
>
> when IGP calculates the underlying FRR it's always a better solution.
> Nothing is faster than IGP and anything calculated as "better FRR" or
> "backup FRR" will not have the topology to do a better job/faster than IGP
> can. So AFAIS the only real use case here is BIER without IGP signalling
> but correct me if I'm wrong
>
> -- tony
>
>
> On Tue, Mar 16, 2021 at 5:02 PM Huaimo Chen <huaimo.chen@futurewei.com>
> wrote:
>
> Hi Michael,
>
>     Thanks much for your valuable comments.
>     My responses are inline below with prefix [HC].
>
> Best Regards,
> Huaimo
> ------------------------------
> *From:* BIER <bier-bounces@ietf.org> on behalf of Michael Menth <
> menth@uni-tuebingen.de>
> *Sent:* Tuesday, March 16, 2021 7:11 AM
> *To:* bier@ietf.org <bier@ietf.org>
> *Subject:* Re: [Bier] WG adoption call for draft-chen-bier-frr-02
>
> Hi Tony, all,
>
> Am 16.03.2021 um 11:08 schrieb Tony Przygienda:
>
> > I think it's a good addition within the architecture for the case IGP is
> > not used for signalling, e.g. when controller or static programming.
>
> Right. The solution may make sense if the routing underlay does not
> offer FRR capabilities.
>
> [HC]: When the routing underlay supports IP FRR, the BIER should also
> provide BIER FRR since the BIER packets are forwarded using the BIFTs.
> When failures happen in the network, the BIER packets are still forwarded
> using the old BIFTs until the old BIFTs are updated according to the
> updated network topology after the failures.
>
> >
> > The draft must however explain in what scenarios it is used and quote
> > the according IGP drafts to guarantee loop-free behavior (well, BIER
> > will tie-break loops but we'll have 1x microloop & possibly not deliver
> > payload if BIER FRR is not properly computed/intsalled). With that the
> > draft should also pay attention to how the function is deployed/updated
> > network-wide if IGP is not present
>
> I agree. in the absence of an IGP, the "native BIER-FRR on bier layer"
> must be set by a controller.
>
> [HC]: I agree too.
>
> So, below the line, an applicability statement would be helpful. What
> are those cases?
> - IGP running but without FRR on the routing underlay?
> - No IGP and no FRR on the routing underlay?
>
> [HC]: When IGP is running in the network, each BFR in the network
> calculates,
> installs and/or updates its BIER FRR BIFTs. The BIER FRR in the draft is
> independent of the underlay IP FRR.
> When no IGP is running in the network, the BIER controller for the network
> calculates, installs and/or updates the BIER FRR BIFTs into BFRs in the
> network,
> regardless of whether the routing underlay FRR is provided.
>
>
> However, if the controller takes care of BIER-FRR, what could be reasons
> for missing FRR on the routing underlay? If there is a FRR on the
> routing underlay (also provided through a controller), tunnel-based
> bier-frr solves the problem in a transparent way.
>
> [HC]: The BIER FRR in the draft is independent of the underlay IP FRR.
> Regardless of whether the routing underlay FRR is provided, the
> BIER FRR BIFTs are computed in the same way.
>
> BTW, we studied protection variants for controller-based infrastructures
> (for routing underlays, not for BIER). Challenge is to keep state low.
> LFA-based solutions help a lot and outperform others. 100% protection is
> possible with only little additions. Results are available:
>
> https://nam11.safelinks.protection.outlook.com/?url=https:%2F%2Fatlas.informatik.uni-tuebingen.de%2F~menth%2Fpapers%2FMenth20-Sub-6.pdf&amp;data=04%7C01%7Chuaimo.chen%40futurewei.com%7C5d3cb8163c7f4a1557e608d8e86c408f%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C1%7C637514898966623524%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=03cc%2BIvdV%2BCg%2F0PCFulWzuCa0h4I5sBqn8K5QPT5BR8%3D&amp;reserved=0
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> (under
> revision)
>
> [HC]: Thanks much for your information.
>
>
> Regards,
>
> Michael
>
> >
> > thanks
> >
> > -- tony
> >
> > On Tue, Mar 16, 2021 at 7:41 AM <zhang.zheng@zte.com.cn
> > <mailto:zhang.zheng@zte.com.cn <zhang.zheng@zte.com.cn>>> wrote:
> >
> >     A 2-week WG adoption call begins for the following draft:
> >
> >
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> >
> >
> >     Please indicate your support or objection by March 30th, 2021.
> >
> >     Authors, please respond to the list indicating whether you are aware
> >     of any IPR that applies to this draft.
> >
> >     Thanks,
> >
> >     Sandy (As WG secretary, on behalf of Greg/Tony)
> >
> >
> >
> > _______________________________________________
> > BIER mailing list
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> >
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> >
>
> --
> Prof. Dr. habil. Michael Menth
> University of Tuebingen
> Faculty of Science
> Department of Computer Science
> Chair of Communication Networks
> Sand 13, 72076 Tuebingen, Germany
> phone: (+49)-7071/29-70505
> fax: (+49)-7071/29-5220
> mailto:menth@uni-tuebingen.de <menth@uni-tuebingen.de>
>
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