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

[[e-mail]]

Hi Michael,






You capture a point that can be optimized. Great.


I agree with you that there are various implementation ways. For example, one way is that the first outgoing packet is sent til the received bitstring is walked completely, that is, before sending the first copy, we can combine multiple outgong bitstrings (steering to the same link) to a single outgoing bitstring. 


Look forward to the merged draft and discuss it further.






Regards,


PSF










原始邮件



发件人：MichaelMenth
收件人：彭少富10053815;zzhang=[e-mail];
抄送人：[e-mail];[e-mail];张征00007940;[e-mail];[e-mail];[e-mail];
日 期 ：2021年03月31日 15:01
主 题 ：Re: [Bier] WG adoption call for draft-chen-bier-frr-02


Dear Peng, all,
 
the merged draft will have an implementation-neutral specification as
you describe. A shortcoming of this approach is that it may result in
redundant packets if a packet has been sent over a specific link and
then another packet must be sent over that link for protection purposes.
But that can be fixed with prioritization of backup entries. There are
various ways to achieve that, but that is an optimization issue and a
matter of implementation. This issue will be well documented with
examples, then it's easy to understand.
 
Implementation options may be mentioned as examples, but they are
platform-specific and the behaviour of bier-frr should be documented in
a similar, neutral style as normal BIER. That's what I understood from
the WG.
 
Kind regards,
 
Michael
 
Am 31.03.2021 um 03:29 schrieb [e-mail]:
> Hi Jeffrey, Chairs, All
>  
>  
> Hope that the following single-BIFT based method can be adopted in the
> merged draft (I posted this idea a few days ago):
>  
>     we can let BIFT entry contain both primary NBR and backup path (note
> that the backup path may be direct NBR, or remote NBR, or segment-list,
> according to IGP TI-LFA result).
>  
>     There are primary FBM and backup FBM. The primary FBM contains the
> Bit-Positions of those BFERs that has the same primary NBR, the backup
> FBM contains the Bit-Positions of those BFERs that has the same backup
> path. In this implementation, when a BFR received a BIER packet, and if
> the primary NBR fails, a copy will be sent to backup path, and *the
> bitstring contained in the copy is the result of "original bitstring of
> the received packet" & "primary FBM" & "backup FBM".*
>  
>  
> And, the following is a further explanation of the comparison between
> the single-BIFT based and FRR-BIFT based, they want to solve the same
> problem as example shows.
>  
>     When primary NBR has failed, the following two schemes have the same
> logic, both of them limit the processing socpe to the failure of
> specific primary NBR.
>  
>     1) Within the scope of specific FRR-BIFT for the primary NBR, when
> packet is steered to an FRR-BIFT entry, the bitstring contained in the
> outgoing copy is the result of "original bitstring of the received
> packet" & "FBM".
>  
>     2) A single BIFT entry with primary NBR and backup path, when packet
> is steered to backup path, the bitstring contained in the outgoing copy
> is the result of "original bitstring of the received packet" & "primary
> FBM" & "backup FBM".
>  
>     For example, BIFT entry 1 has primary NBR X, BIFT entry 2 has
> primary NBR Y, but they have the same backup path. When NBR X has
> failed, BIFT entry 1 need switch to backup path, but BIFT entry 2 need not.
>  
>  
> If we are not clear about the above single-BIFT based idea, maybe we can
> also write a separate informaitonal draft to describe it.
>  
>  
> Regards,
>  
> PSF
>  
>  
>  
> 原始邮件
> *发件人：*Jeffrey(Zhaohui)Zhang
> *收件人：*Michael McBride;[e-mail];
> *抄送人：*张征00007940;BIER WG;Huaimo Chen;BIER WG Chairs;
> *日 期 ：*2021年03月31日 01:43
> *主 题 ：**Re: [Bier] WG adoption call for draft-chen-bier-frr-02*
> _______________________________________________
> BIER mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/bier
>  
> Hi,
>  
>  
>  
> At the risk of being viewed as trying to steal the work or trying to
> squeeze in as a co-author, let me review some history and my position here.
>  
>  
>  
> Two years ago after draft-merling was first published, there were quite
> some discussions involving the Michael/Daniel and some vendors/operator,
> and both tunnel-to-neighbor and alternative-to-BFERs options were
> discussed. We concluded that we would not need to standardize it, and
> Michael/Daniel did not progress the work in BIER WG afterwards.
>  
>  
>  
> If I just wanted to squeeze in as co-author of another BIER draft, I
> assume I could have done that two years ago.
>  
>  
>  
> If we were not calling for adoption draft-chen-bier-frr, there would be
> no controversy.
>  
>  
>  
> Now that we’re here, given my strong objection to have per-nbr FRR BIFTs
> in a WG document, I do want to speak up and I appreciate Greg’s
> suggestion of me as editor, and I am confident that I would be the best
> person for it given the history and my insights on this matter.
>  
>  
>  
> As for whether I am eligible for the role process wise – I suppose I
> could also write a draft-zzhang on this topic and join the merge? In
> fact, that may be the best way to fully describe my view on BIER FRR.
>  
>  
>  
> In fact - process wise – if we talk about merging wouldn’t it be merging
> into draft-merling given it’s the earliest and it is more close to the
> unicast FRR model (not using separate FRR BIFTs)?
>  
>  
>  
> And finally, yes if this remains as an individual informational draft, I
> would not care so much.
>  
>  
>  
> Thanks.
> Jeffrey
>  
>  
>  
> *From:* Michael McBride <[e-mail]> 
> *Sent:* Tuesday, March 30, 2021 1:05 PM
> *To:* [e-mail]
> *Cc:* Jeffrey (Zhaohui) Zhang <[e-mail]>; BIER WG
> <[e-mail]>; BIER WG Chairs <[e-mail]>;
> [e-mail] <[e-mail]>; Huaimo Chen
> <[e-mail]> 
> *Subject:* RE: [Bier] WG adoption call for draft-chen-bier-frr-02
>  
>  
>  
> *[External Email. Be cautious of content]*
>  
>  
>  
> I’m honestly at a loss here. An assigned editor to take over our work?
> Is this even a thing in the ietf?
>  
>  
>  
> If this is the case we will continue working on this draft and keep it
> individual for now.
>  
>  
>  
> mike
>  
>  
>  
> *From:* Greg Shepherd <[e-mail] <mailto:[e-mail]>> 
> *Sent:* Tuesday, March 30, 2021 9:48 AM
> *To:* Michael McBride <[e-mail]
> <mailto:[e-mail]>> 
> *Cc:* Jeffrey (Zhaohui) Zhang <[e-mail]
> <mailto:[e-mail]>>; BIER WG <[e-mail]
> <mailto:[e-mail]>>; BIER WG Chairs <[e-mail]
> <mailto:[e-mail]>>; [e-mail]
> <mailto:[e-mail]> <[e-mail]
> <mailto:[e-mail]>>; Huaimo Chen <[e-mail]
> <mailto:[e-mail]>> 
> *Subject:* Re: [Bier] WG adoption call for draft-chen-bier-frr-02
>  
>  
>  
>  
>  
>  
>  
> On Tue, Mar 30, 2021 at 9:28 AM Michael McBride
> <[e-mail] <mailto:[e-mail]>> 
> wrote:
>  
>     > .contribute two authors to the merged doc effort, and have Jeffrey
>     hold the pen as editor/author. 
>  
>      
>  
>     Huh? All authors from both drafts will remain on the merged draft
>  
>  
>  
> Pick them now or pick them later. 
>  
>  
>  
>     and, as much as we respect Jeffrey, he’s not an author and certainly
>     doesn’t hold the pen.
>  
>  
>  
> As the assigned Editor to work with the author of both drafts, yes he
> will hold the pen. If you have another 3rd party Editor to suggest,
> please do so. But from the current discussion on the list, I find no one
> more qualified to work with the authors of both contributing drafts.
>  
>  
>  
> Thanks,
>  
> Greg
>  
>  
>  
>     Mike
>  
>      
>  
>      
>  
>     All agreed?
>  
>      
>  
>     Thanks,
>  
>     Greg
>  
>     (Chairs)
>  
>      
>  
>     On Mon, Mar 29, 2021 at 7:26 PM Jeffrey (Zhaohui) Zhang
>     <[e-mail] <mailto:[e-mail]>> wrote:
>  
>         Shouldn’t it be the other way around – expand/merge first and
>         then adopt?
>  
>          
>  
>         In fact, the essence of draft-chen is the multiple per-nbr FRR
>         BIFTs, which I don’t think should be included in the merged
>         draft at all, for the following problems:
>  
>          
>  
>          1.
>  
>             Scaling – we need one extra BIFT for each <neighbor, BIFT>.
>             This not only means extra memory, but also additional
>             processing overhead including downloading the tables to the
>             forwarding plane.
>  
>          2.
>  
>             If two neighbors fail simultaneously yet both can be
>             protected by a 3^rd neighbor, per-nbr FRR BIFTs can only
>             give protection for one of the first two neighbors. This is
>             not an unusual situation – you could have two neighbors
>             reached by the same link or the same line card, and the
>             link/card fails.
>  
>          3.
>  
>             Exactly when to switch back from a per-nbr FRR BIFT to the
>             regular BIFT?
>  
>          
>  
>         The draft says the following about #3:
>  
>          
>  
>            In general, when the routing protocol has re-converged on the new
>  
>            topology taking into account the failure of X, the BIRT is re-
>  
>            computed using the updated LSDB and the BIFT is re-derived
>         from the
>  
>            BIRT.  Once the BIFT is installed ready for activation, it is
>  
>            activated to forward packets with BIER headers and the
>         FRR-BIFT for X
>  
>            is de-activated.
>  
>          
>  
>         Does that mean for each computation, you need to know and mark
>         which failed neighbor that it takes care of, so that when the
>         BIFT is sent down to forwarding plane you can decide if
>         currently used FRR-BIFT can be switched back to the main BIFT?
>  
>          
>  
>         Also consider the following:
>  
>          
>  
>          1.
>  
>             At moment T you switch to FRR BIFT for nbr X
>  
>          2.
>  
>             At moment T+1ms a new BIFT is calculated, which takes care
>             of a remote failure but not nbr X (nbr X is still considered
>             up in this calculation) – would you switch FRR BIFT to the
>             newly calculated main BIFT? If you don’t, the remote failure
>             could lead to packet losses until the new main BIFT is used.
>             If you do, you only get FRR protection for nbr X for 1ms.
>  
>          
>  
>         Jeffrey
>  
>          
>  
>         *From:* BIER <[e-mail]
>         <mailto:[e-mail]>> *On Behalf Of *Huaimo Chen
>         *Sent:* Thursday, March 25, 2021 5:06 PM
>         *To:* Tony Przygienda <[e-mail]
>         <mailto:[e-mail]>>; [e-mail]
>         <mailto:[e-mail]> <[e-mail]
>         <mailto:[e-mail]>> 
>         *Cc:* BIER WG <[e-mail] <mailto:[e-mail]>>; BIER WG
>         Chairs <[e-mail] <mailto:[e-mail]>> 
>         *Subject:* Re: [Bier] WG adoption call for draft-chen-bier-frr-02
>  
>          
>  
>         *[External Email. Be cautious of content]*
>  
>          
>  
>         Hi Everyone,
>  
>          
>  
>             Michael, Steffan, Huaimo and Mike met to discuss the merge
>         and we are in agreement that if draft-chen-bier-frr is adopted
>         we will expand it to include a framework along with the tunnel
>         and LFA based solutions.
>  
>          
>  
>         Best Regards,
>  
>         Huaimo
>  
>         ------------------------------------------------------------------------
>  
>         *From:*BIER <[e-mail]
>         <mailto:[e-mail]>> on behalf of Tony Przygienda
>         <[e-mail] <mailto:[e-mail]>> 
>         *Sent:* Tuesday, March 16, 2021 6:08 AM
>         *To:* zhang.zheng <[e-mail]
>         <mailto:[e-mail]>> 
>         *Cc:* BIER WG <[e-mail] <mailto:[e-mail]>>; BIER WG
>         Chairs <[e-mail] <mailto:[e-mail]>> 
>         *Subject:* Re: [Bier] WG adoption call for draft-chen-bier-frr-02
>  
>          
>  
>         +1
>  
>          
>  
>         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.
>  
>          
>  
>         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
>  
>          
>  
>         thanks
>  
>          
>  
>         -- tony
>  
>          
>  
>         On Tue, Mar 16, 2021 at 7:41 AM <[e-mail]
>         <mailto:[e-mail]>> wrote:
>  
>             A 2-week WG adoption call begins for the following draft:
>  
>             https://datatracker.ietf.org/doc/draft-chen-bier-frr/
>             <https://urldefense.com/v3/__https:/nam11.safelinks.protection.outlook.com/?url=https*3A*2F*2Furldefense.com*2Fv3*2F__https*3A*2Fnam11.safelinks.protection.outlook.com*2F*3Furl*3Dhttps*3A*2F*2Fdatatracker.ietf.org*2Fdoc*2Fdraft-chen-bier-frr*2F*26data*3D04*7C01*7Chuaimo.chen*40futurewei.com*7C79ac63710b47427a558d08d8e8638df2*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C1*7C637514861570555970*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C1000*26sdata*3DDiHvux0ZUYEJru10lVQ4mXvpYx3l8ujGInm7uEjjxTw*3D*26reserved*3D0__*3BJSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!TtAnkZJhg9BEJjANzO6CusX7i7eQqvTJHdhaH0qrrPdtcykRPrUybhZeavPA3X4F*24&data=04*7C01*7Cmichael.mcbride*40futurewei.com*7C1c5fd4db18e2431f463f08d8f39b6caf*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C0*7C637527196165767516*7CUnknown*7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0*3D*7C1000&sdata=rJEgGwKe3zvhltMwI7v12duGQm*2Bg08Kml*2Bum1SzOUAo*3D&reserved=0__;JSUlJSUlJSUlJSoqKioqKiUlKioqKioqKioqKioqJSUqJSUlJSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!TgjeaofJrDC7_PaFdp5121nhpqbYPTuvoqq2taHHIFDUiNUmO2r2LHrrnuo6K9DY$> 
>  
>             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)
>  
>              
>  
>          
>  
>         Juniper Business Use Only
>  
>  
> Juniper Business Use Only
>  
>  
>  
> _______________________________________________
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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: [phone]
fax: [phone]
mailto:[e-mail]
http://kn.inf.uni-tuebingen.de
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