Re: [Lsr] New Version Notification for draft-bonica-lsr-ip-flexalgo-00.txt

["Joel M. Halpern" <[e-mail]>]

I am missing something in this discussion of multiple algorithms.

My understanding of flex-algo whether for MPLS, SRv6, SRH, or IPv6, is 
that you need to associated a forwarding label (e.g. MPLS label or IPv6 
address) with a specific algorithm so that you can compute the next hope 
for the forwarding label using the proper algorithm.  Then when a packet 
arrives, it is simply forwarded according to the forwarding table (e.g. 
FIB, LIB, ..)

If that is so, then I do not understand how a given prefix can be safely 
associated with more than one algorithm.  I could imagine doing several 
calculations according to different algorithms.  But how do you decide 
which one applies to the packet?  As far as I know, flex-algo does not 
look at the QoS/CoS/ToS bits.

Yours,
Joel

PS: I will admit that it took until  an operator described some 
"interesting" constraints before I understood why one would even do this.

On 9/29/2020 11:50 PM, Huzhibo wrote:
> Hi.
> 
> Associating multiple algorithms with a given prefix is an interesting topic, and I think this can simplify the complexity of FlexAlgo. I wonder if the author would consider using cases with multiple algorithms with a given prefix.
> 
> Thanks
> 
> ZHibo
> 
> -----Original Message-----
> From: Lsr [mailto:[e-mail]] On Behalf Of [e-mail]
> Sent: Tuesday, September 29, 2020 10:05 PM
> To: Ron Bonica <rbonica=[e-mail]>
> Cc: [e-mail]
> Subject: Re: [Lsr] New Version Notification for draft-bonica-lsr-ip-flexalgo-00.txt
> 
> 
> Ron,
> 
> This is nice. It makes it clear that constraint based path computation need not have MPLS overhead for those that don’t want it.
> 
> One thing that you don’t talk about is how this gets used, tho that may be blindingly obvious: you’ll need all nodes placing their prefixes in the RIB/FIB, where it will need to be selected over other path computation for the same prefixes.  This somewhat precludes the possibility of a given prefix being useful in multiple flex-algos.
> 
> More text on application would be most welcome, just to ensure that we’re on the same page.
> 
> Tony
> 
> 
>> On Sep 29, 2020, at 6:37 AM, Ron Bonica <rbonica=[e-mail]> wrote:
>>
>>
>> Please review and comment
>>
>>                                        Ron
>>
>>
>>
>> Juniper Business Use Only
>>
>>> -----Original Message-----
>>> From: [e-mail] <[e-mail]>
>>> Sent: Tuesday, September 29, 2020 9:36 AM
>>> To: Parag Kaneriya <[e-mail]>; Shraddha Hegde
>>> <[e-mail]>; Ron Bonica <[e-mail]>; Rajesh M
>>> <[e-mail]>; William Britto A J <[e-mail]>
>>> Subject: New Version Notification for
>>> draft-bonica-lsr-ip-flexalgo-00.txt
>>>
>>> [External Email. Be cautious of content]
>>>
>>>
>>> A new version of I-D, draft-bonica-lsr-ip-flexalgo-00.txt
>>> has been successfully submitted by Ron Bonica and posted to the IETF
>>> repository.
>>>
>>> Name:           draft-bonica-lsr-ip-flexalgo
>>> Revision:       00
>>> Title:          IGP Flexible Algorithms (Flexalgo) In IP Networks
>>> Document date:  2020-09-29
>>> Group:          Individual Submission
>>> Pages:          14
>>> URL:            https://urldefense.com/v3/__https://www.ietf.org/id/draft-bonica-
>>> lsr-ip-flexalgo-00.txt__;!!NEt6yMaO-gk!X7PVDP-
>>> FnUA0oCcZMw3Qde6in0C72hu_9hOZ53kPspIarR8fNDyU9Vck80Zbjoij$
>>> Status:
>>> https://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft-bo
>>> nica-lsr-
>>> ip-flexalgo/__;!!NEt6yMaO-gk!X7PVDP-
>>> FnUA0oCcZMw3Qde6in0C72hu_9hOZ53kPspIarR8fNDyU9Vck8x7e5ZqI$
>>> Htmlized:
>>> https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/dra
>>> ft-
>>> bonica-lsr-ip-flexalgo__;!!NEt6yMaO-gk!X7PVDP-
>>> FnUA0oCcZMw3Qde6in0C72hu_9hOZ53kPspIarR8fNDyU9Vck82w_6CyU$
>>> Htmlized:       https://urldefense.com/v3/__https://tools.ietf.org/html/draft-
>>> bonica-lsr-ip-flexalgo-00__;!!NEt6yMaO-gk!X7PVDP-
>>> FnUA0oCcZMw3Qde6in0C72hu_9hOZ53kPspIarR8fNDyU9Vck81_QrJ_p$
>>>
>>>
>>> Abstract:
>>>    An IGP Flexible Algorithm computes a constraint-based path and maps
>>>    that path to an identifier.  As currently defined, Flexalgo can only
>>>    map the paths that it computes to Segment Routing (SR) identifiers.
>>>    Therefore, Flexalgo cannot be deployed in the absence of SR.
>>>
>>>    This document extends Flexalgo, so that it can map the paths that it
>>>    computes to IP addresses.  This allows Flexalgo to be deployed in any
>>>    IP network, even in the absence of SR.
>>>
>>>
>>>
>>>
>>> Please note that it may take a couple of minutes from the time of
>>> submission until the htmlized version and diff are available at tools.ietf.org.
>>>
>>> The IETF Secretariat
>>>
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