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

Michael Menth <menth@uni-tuebingen.de> Tue, 16 March 2021 22:57 UTC

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To: "Jeffrey (Zhaohui) Zhang" <zzhang@juniper.net>, Huaimo Chen <huaimo.chen@futurewei.com>, Tony Przygienda <tonysietf@gmail.com>
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From: Michael Menth <menth@uni-tuebingen.de>
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Date: Tue, 16 Mar 2021 23:57:18 +0100
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Subject: Re: [Bier] WG adoption call for draft-chen-bier-frr-02
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Hi Jeffrey,

I understand that informational is the right classification of such
documents. I see two options.
- A single document covering the entire topic.
- Two bier-frr docs (tunnel-based and lfa-based), preferentially using
similar laguage. Then one can talk about RFC 123 or RFC XYZ protection.
If the mechanisms are described within a single document, there is some
potential for confusion. Not sure if an overarching framework for
bier-frr is then still needed.

Regards,

Michael


Am 16.03.2021 um 23:16 schrieb Jeffrey (Zhaohui) Zhang:
> Hi Michael,
> 
> We are on the same page. Progressing an informational draft on this topic is fine and seems to be even more necessary now. In fact, when draft-chen was presented last time I had suggested for some joint work.
> 
> Thanks.
> Jeffrey
> 
> -----Original Message-----
> From: Michael Menth <menth@uni-tuebingen.de>
> Sent: Tuesday, March 16, 2021 3:03 PM
> To: Jeffrey (Zhaohui) Zhang <zzhang@juniper.net>et>; Huaimo Chen <huaimo.chen@futurewei.com>om>; Tony Przygienda <tonysietf@gmail.com>
> Cc: bier@ietf.org
> Subject: Re: [Bier] WG adoption call for draft-chen-bier-frr-02
> 
> [External Email. Be cautious of content]
> 
> 
> Hi Jeffrey, all,
> 
> your proposal was also the conclusion two years ago when I brought up
> the topic in the working group:
> 
> "The BIER FRR mechanism - be it tunnel-based or re-implementing LFAs on
> the BIER layer - is a local mechanism and does not require cooperation
> from other nodes. Probably both mechanisms can be even mixed within the
> same network. Therefore, there is not need for standardization."
> 
> I think this is not documented in any IETF drafts or even meeting
> minutes, it was just a conclusion from some side meetings. That was also
> the reason why we did not progress the draft on tunnel-based bier-frr.
> 
> Nevertheless, it may be helpful to at least document both existing
> bier-frr approaches as an informational draft so that manufacturers can
> easily point to an implemented solution. This is helpful as both
> solutions have pros and cons. A lot of contents is already in that paper
> in which we summarized our understanding of the discussions two years ago:
> https://urldefense.com/v3/__https://atlas.informatik.uni-tuebingen.de/*menth/papers/Menth20c.pdf__;fg!!NEt6yMaO-gk!XVo5XuifwFLLaWFLD2OZmJq1fws1WhcSKnUU3bjUch1IhPPKhQgxjetcUsxoFVJv$
> Some of its content may be useful for an overview draft of bier-frr methods.
> 
> Regards
> 
> Michael
> 
> Am 16.03.2021 um 19:23 schrieb Jeffrey (Zhaohui) Zhang:
>> If you consider BIFT and unicast FIB, they are actually very similar
>> (ignoring the SI/sub-domain and bier label aspects). The only
>> differences are:
>>
>>
>>
>>  1. (bfr-id % bitstringLength) or prefix as key
>>  2. F-BM associated with a BFR-nbr in BIFT
>>
>>
>>
>> Each BIFT entry is built according how to reach a corresponding BFER,
>> and the F-BM is obtained by setting the bits for all the BFERs that are
>> reached by the BFR nbr.
>>
>>
>>
>> So, however you do FRR for unicast (LFA or tunnel based link/node
>> protection or whatever) and whether it is IGP or BGP or whatever, you
>> can just build the BIER FRR forwarding state the same way, and update
>> the F-BM for the backup nbr accordingly.
>>
>>
>>
>> That's why I keep saying that there is not much to standardize on BIER
>> FRR. It seems that this topic keeps coming up, so perhaps I should write
>> an information draft to elaborate the above principle and how it works
>> with various protection mechanisms.
>>
>>
>>
>> Jeffrey
>>
>>
>>
>> *From:* BIER <bier-bounces@ietf.org> *On Behalf Of * Huaimo Chen
>> *Sent:* Tuesday, March 16, 2021 1:28 PM
>> *To:* Tony Przygienda <tonysietf@gmail.com>
>> *Cc:* bier@ietf.org; Michael Menth <menth@uni-tuebingen.de>
>> *Subject:* Re: [Bier] WG adoption call for draft-chen-bier-frr-02
>>
>>
>>
>> *[External Email. Be cautious of content]*
>>
>>
>>
>> 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 <mailto:tonysietf@gmail.com>>
>> *Sent:* Tuesday, March 16, 2021 12:58 PM
>> *To:* Huaimo Chen <huaimo.chen@futurewei.com
>> <mailto:huaimo.chen@futurewei.com>>
>> *Cc:* Michael Menth <menth@uni-tuebingen.de
>> <mailto:menth@uni-tuebingen.de>>; bier@ietf.org <mailto:bier@ietf.org>
>> <bier@ietf.org <mailto: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
>> <mailto: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 <mailto:bier-bounces@ietf.org>>
>>     on behalf of Michael Menth <menth@uni-tuebingen.de
>>     <mailto:menth@uni-tuebingen.de>>
>>     *Sent:* Tuesday, March 16, 2021 7:11 AM
>>     *To:* bier@ietf.org <mailto:bier@ietf.org> <bier@ietf.org
>>     <mailto: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://urldefense.com/v3/__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__;JSUlfiUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!XVo5XuifwFLLaWFLD2OZmJq1fws1WhcSKnUU3bjUch1IhPPKhQgxjetcUh_8_hxk$
>>     <https://urldefense.com/v3/__https:/nam11.safelinks.protection.outlook.com/?url=https:*2F*2Fatlas.informatik.uni-tuebingen.de*2F*menth*2Fpapers*2FMenth20-Sub-6.pdf&data=04*7C01*7Chuaimo.chen*40futurewei.com*7C2b86f5e805f04cf24c1008d8e89cdcd4*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C1*7C637515107733090092*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C1000&sdata=CNKcultin43VrTAvr*2BFH7V1FrMALSvaSpfmEiHcKm*2Fg*3D&reserved=0__;JSUlfiUlJSUlJSUlJSUlJSUlJSUl!!NEt6yMaO-gk!SBpWq7LIP13dlIX5P6U98cqIp8gTMP5_gelzA7rNyBrhf7h6mMn6N6YLFKhaK3F2$>
>>     (under
>>     revision)
>>
>>
>>
>>     [HC]: Thanks much for your information.
>>
>>
>>
>>     Regards,
>>
>>     Michael
>>
>>     >
>>     > thanks
>>     >
>>     > -- tony
>>     >
>>     > On Tue, Mar 16, 2021 at 7:41 AM <zhang.zheng@zte.com.cn
>>     <mailto:zhang.zheng@zte.com.cn>
>>     > <mailto:zhang.zheng@zte.com.cn <mailto:zhang.zheng@zte.com.cn>>>
>>     wrote:
>>     >
>>     >     A 2-week WG adoption call begins for the following draft:
>>     >
>>     >
>>     https://urldefense.com/v3/__https://nam11.safelinks.protection.outlook.com/?url=https*3A*2F*2Fdatatracker.ietf.org*2Fdoc*2Fdraft-chen-bier-frr*2F&amp;data=04*7C01*7Chuaimo.chen*40futurewei.com*7C5d3cb8163c7f4a1557e608d8e86c408f*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C1*7C637514898966623524*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C3000&amp;sdata=797z0ndM2IahVL2y9xPoY*2BOU5x4*2F3w1FaSWfoF*2BC6pQ*3D&amp;reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!XVo5XuifwFLLaWFLD2OZmJq1fws1WhcSKnUU3bjUch1IhPPKhQgxjetcUjt7UD4f$
>>     <https://urldefense.com/v3/__https:/nam11.safelinks.protection.outlook.com/?url=https*3A*2F*2Fdatatracker.ietf.org*2Fdoc*2Fdraft-chen-bier-frr*2F&data=04*7C01*7Chuaimo.chen*40futurewei.com*7C2b86f5e805f04cf24c1008d8e89cdcd4*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C1*7C637515107733090092*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C1000&sdata=4v2q4ToPT83pQYu5Fdwpc04pIcWrlihqy5m8YjgkVMA*3D&reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!SBpWq7LIP13dlIX5P6U98cqIp8gTMP5_gelzA7rNyBrhf7h6mMn6N6YLFNWNaFXu$>
>>     >
>>     <https://urldefense.com/v3/__https://nam11.safelinks.protection.outlook.com/?url=https*3A*2F*2Fdatatracker.ietf.org*2Fdoc*2Fdraft-chen-bier-frr*2F&amp;data=04*7C01*7Chuaimo.chen*40futurewei.com*7C5d3cb8163c7f4a1557e608d8e86c408f*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C1*7C637514898966623524*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C3000&amp;sdata=797z0ndM2IahVL2y9xPoY*2BOU5x4*2F3w1FaSWfoF*2BC6pQ*3D&amp;reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!XVo5XuifwFLLaWFLD2OZmJq1fws1WhcSKnUU3bjUch1IhPPKhQgxjetcUjt7UD4f$
>>     <https://urldefense.com/v3/__https:/nam11.safelinks.protection.outlook.com/?url=https*3A*2F*2Fdatatracker.ietf.org*2Fdoc*2Fdraft-chen-bier-frr*2F&data=04*7C01*7Chuaimo.chen*40futurewei.com*7C2b86f5e805f04cf24c1008d8e89cdcd4*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C1*7C637515107733100045*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C1000&sdata=koqOJ4RFqPhBPl81t259PjxeQ6TxmcdtMMqgC0XXDzQ*3D&reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!SBpWq7LIP13dlIX5P6U98cqIp8gTMP5_gelzA7rNyBrhf7h6mMn6N6YLFF8NiiJX$>>
>>     >
>>     >     Please indicate your support or objection by March 30th, 2021.
>>     >
>>     >     Authors, please respond to the list indicating whether you are
>>     aware
>>     >     of any IPR that applies to this draft.
>>     >
>>     >     Thanks,
>>     >
>>     >     Sandy (As WG secretary, on behalf of Greg/Tony)
>>     >
>>     >
>>     >
>>     > _______________________________________________
>>     > BIER mailing list
>>     > BIER@ietf.org <mailto:BIER@ietf.org>
>>     >
>>     https://urldefense.com/v3/__https://nam11.safelinks.protection.outlook.com/?url=https*3A*2F*2Fwww.ietf.org*2Fmailman*2Flistinfo*2Fbier&amp;data=04*7C01*7Chuaimo.chen*40futurewei.com*7C5d3cb8163c7f4a1557e608d8e86c408f*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C1*7C637514898966623524*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C3000&amp;sdata=aZ6*2BjQBpo7k81fqf*2FnYdfer7mS45RlhB0lPT7*2B*2BVm6I*3D&amp;reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJSUlJSU!!NEt6yMaO-gk!XVo5XuifwFLLaWFLD2OZmJq1fws1WhcSKnUU3bjUch1IhPPKhQgxjetcUnaUrsWg$
>>     <https://urldefense.com/v3/__https:/nam11.safelinks.protection.outlook.com/?url=https*3A*2F*2Fwww.ietf.org*2Fmailman*2Flistinfo*2Fbier&data=04*7C01*7Chuaimo.chen*40futurewei.com*7C2b86f5e805f04cf24c1008d8e89cdcd4*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C1*7C637515107733110014*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C1000&sdata=54DHmen2Kbqxu0LRWeuGlVBQbIepvbs1MqJHtfd6Wh8*3D&reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!SBpWq7LIP13dlIX5P6U98cqIp8gTMP5_gelzA7rNyBrhf7h6mMn6N6YLFMxV4XUQ$>
>>     >
>>
>>     --
>>     Prof. Dr. habil. Michael Menth
>>     University of Tuebingen
>>     Faculty of Science
>>     Department of Computer Science
>>     Chair of Communication Networks
>>     Sand 13, 72076 Tuebingen, Germany
>>     phone: (+49)-7071/29-70505
>>     fax: (+49)-7071/29-5220
>>     mailto:menth@uni-tuebingen.de <mailto:menth@uni-tuebingen.de>
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> 
> --
> Prof. Dr. habil. Michael Menth
> University of Tuebingen
> Faculty of Science
> Department of Computer Science
> Chair of Communication Networks
> Sand 13, 72076 Tuebingen, Germany
> phone: (+49)-7071/29-70505
> fax: (+49)-7071/29-5220
> mailto:menth@uni-tuebingen.de
> https://urldefense.com/v3/__http://kn.inf.uni-tuebingen.de__;!!NEt6yMaO-gk!XVo5XuifwFLLaWFLD2OZmJq1fws1WhcSKnUU3bjUch1IhPPKhQgxjetcUk6GcMm1$
> 
> Juniper Business Use Only
> 

-- 
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
http://kn.inf.uni-tuebingen.de