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

[[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


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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]> 
 Sent: Tuesday, March 30, 2021 9:48 AM
 To: Michael McBride <[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



 


 


 


On Tue, Mar 30, 2021 at 9:28 AM Michael McBride <[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]> 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:


 

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.

If two neighbors fail simultaneously yet both can be protected by a 3rd 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.

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:


 

At moment T you switch to FRR BIFT for nbr X

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]> On Behalf Of Huaimo Chen
 Sent: Thursday, March 25, 2021 5:06 PM
 To: Tony Przygienda <[e-mail]>; [e-mail] <[e-mail]>
 Cc: BIER WG <[e-mail]>; BIER WG Chairs <[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]> on behalf of Tony Przygienda <[e-mail]>
 Sent: Tuesday, March 16, 2021 6:08 AM
 To: zhang.zheng <[e-mail]>
 Cc: BIER WG <[e-mail]>; BIER WG Chairs <[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]> wrote:


A 2-week WG adoption call begins for the following draft:

https://datatracker.ietf.org/doc/draft-chen-bier-frr/

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)

 








 


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