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

["Dongjie (Jimmy)" <[e-mail]>]

Hi Peter, 

> -----Original Message-----
> From: Peter Psenak [mailto:[e-mail]]
> Sent: Tuesday, October 13, 2020 4:53 PM
> To: Dongjie (Jimmy) <[e-mail]>; Ron Bonica
> <[e-mail]>; Yingzhen Qu <[e-mail]>; Gyan
> Mishra <[e-mail]>
> Cc: [e-mail]; Jeff Tantsura <[e-mail]>
> Subject: Re: [Lsr] FW: New Version Notification for
> draft-bonica-lsr-ip-flexalgo-00.txt
> 
> >>> When one node compute an SR path to a destination, can it compute
> >>> the path
> >> to only pass the nodes which bind FA-128 to SR SIDs, and avoid the
> >> nodes >which bind FA-128 to IP address? If so, how could this node
> >> know the binding of FA to different data planes on other nodes?
> >>
> >> again, it is the participation problem.
> >>
> >> Nodes that participate in the SR Flex-algo 128 will advertise the
> >> participation using the SR-Algorithm Sub-TLV. Only these nodes will
> >> be used during the SR flex-algo computation for algo 128.
> >>
> >> Nodes that participate in IP flex-algo 128 will advertise the
> >> participation using the IGP Algorithm Sub-TLV. Only these nodes will
> >> be used during the IP flex-algo computation for algo 128.
> >
> > Agree that if participation to Flex-Algo is advertised in a data plane specific
> manner, then path computation with Flex-Algo constraints could be done only
> using nodes which bind the Flex-Algo to the same data plane.
> 
> it's per app, not per data plane, but yes, that is what the base flex-algo spec
> mandates.
>
> > As Robert asked and you confirmed, this implies each data plane needs to be
> treated as an independent application of Flex-Algo. We have SR-Algorithm
> sub-TLV and IP Algorithm sub-TLV, while there are actually more data planes to
> be considered: SR-MPLS, SRv6, IPv4, IPv6, etc., does this mean that Flex-Algo
> participation needs to be advertised for SR-MPLS, SRv6, IPv4, IPv6, etc.
> separately?
> 
> yes, it needs to be advertised per app. We have SR specific algo participation,
> we need one for IP as proposed in Ron's draft.

OK. While the meaning of "app" here maybe a little vague, are SR-MPLS and SRv6 considered the same or different apps? 

> Regarding IPv4 vs IPv6, it's up to the authors whether they want to make the
> participation for IP flex-algo topology specific or topology independent, both
> could work.

If the participation is topology specific, do you mean IPv4 and IPv6 could be distinguished by advertising Flex-Algo participation with different Topology IDs (MT-ID)? This way, is the topology ID actually used as the address family distinguisher?

Best regards,
Jie

> Here's the text from the base flerx-algo draft:
> 
> 10.2.  Advertisement of Node Participation for Other Applications
> 
>     This section describes considerations related to how other
>     applications can advertise their participation in a specific Flex-
>     Algorithm.
> 
>     Application-specific Flex-Algorithm participation advertisements MAY
>     be topology specific or MAY be topology independent, depending on the
>     application itself.
> 
>     Application-specific advertisement for Flex-Algorithm participation
>     MUST be defined for each application and is outside of the scope of
>     this document.
> 
> thanks,
> Peter
> 
> 
> >
> > Best regards,
> > Jie
> >
> >>
> >> thanks,
> >> Peter
> >>
> >>>
> >>> Best regards,
> >>> Jie
> >>>
> >>>> -----Original Message-----
> >>>> From: Lsr [mailto:[e-mail]] On Behalf Of Peter Psenak
> >>>> Sent: Friday, October 9, 2020 11:58 PM
> >>>> To: Dongjie (Jimmy) <[e-mail]>; Ron Bonica
> >>>> <rbonica=[e-mail]>; Yingzhen Qu
> >>>> <[e-mail]>; Gyan Mishra <[e-mail]>
> >>>> Cc: [e-mail]; Jeff Tantsura <[e-mail]>
> >>>> Subject: Re: [Lsr] FW: New Version Notification for
> >>>> draft-bonica-lsr-ip-flexalgo-00.txt
> >>>>
> >>>> Hi Jimmy,
> >>>>
> >>>>
> >>>>     On 09/10/2020 04:59, Dongjie (Jimmy) wrote:
> >>>>> Hi Ron,
> >>>>>
> >>>>> Thanks for explaining the difference between IP Flex-Algo and SR
> >>>>> Flex-algo. As
> >>>> you said, the major difference is the data plane.
> >>>>>
> >>>>> If my understanding is correct, for one Flex-Algo to be used
> >>>>> correctly, the set
> >>>> of nodes need to apply consistent constraints in computation, and
> >>>> bind the FAD to the same data plane.
> >>>>>
> >>>>> Is it possible that different nodes may use the same Flex-Algo
> >>>>> with different
> >>>> data plane, e.g. some with SR-MPLS, some with SRv6, and some with
> >>>> pure IP etc., or each Flex-Algo is always associated with only one
> >>>> data plane? In the former case, should the flex-algo definition
> >>>> also indicate the data plane(s) to be used with the flex-algo?
> >>>>
> >>>> let me respond to this query, as this is not specific to Ron's draft.
> >>>>
> >>>> FAD is data plane agnostic and is used by all of them.
> >>>>
> >>>> thanks,
> >>>> Peter
> >>>>
> >>>>>
> >>>>> Best regards,
> >>>>> Jie
> >>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: Lsr [mailto:[e-mail]] On Behalf Of Ron Bonica
> >>>>>> Sent: Sunday, October 4, 2020 4:34 AM
> >>>>>> To: Yingzhen Qu <[e-mail]>; Peter Psenak
> >>>>>> <[e-mail]>; Gyan Mishra <[e-mail]>
> >>>>>> Cc: [e-mail]; Jeff Tantsura <[e-mail]>
> >>>>>> Subject: Re: [Lsr] FW: New Version Notification for
> >>>>>> draft-bonica-lsr-ip-flexalgo-00.txt
> >>>>>>
> >>>>>> Hi Yingzhen,
> >>>>>>
> >>>>>> IP Flexible Algorithms are like SR Flexible Algorithms in the
> >>>>>> following
> >>>> respects:
> >>>>>>
> >>>>>> - Links have IGP metrics, TE metrics, delay metrics and
> >>>>>> administrative colors
> >>>>>> - FADs define Flexible Algorithms
> >>>>>>
> >>>>>> More specifically, the FAD:
> >>>>>>
> >>>>>> - Indicates which metric type the Flexible Algorithm uses
> >>>>>> - Specifies constraints in terms of link colors that are included
> >>>>>> or excluded from the Flexible Algorithm.
> >>>>>>
> >>>>>> The significant difference between IP Flexible Algorithms and SR
> >>>>>> Flexible Algorithms is:
> >>>>>>
> >>>>>> - SR Flexible Algorithms bind FADs to prefix SIDs or SRv6
> >>>>>> locators
> >>>>>> - IP Flexible Algorithms bind FADs to IPv4 or IPv6 addresses.
> >>>>>>
> >>>>>> So, IP Flexible Algorithms can be deployed in any IP network,
> >>>>>> even in the absence of SR.
> >>>>>>
> >>>>>>                                            Ron
> >>>>>>
> >>>>>>
> >>>>>> Juniper Business Use Only
> >>>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: Yingzhen Qu <[e-mail]>
> >>>>>> Sent: Saturday, October 3, 2020 2:08 PM
> >>>>>> To: Peter Psenak <[e-mail]>; Gyan Mishra
> >>>>>> <[e-mail]>; Ron Bonica <[e-mail]>
> >>>>>> Cc: [e-mail]; Jeff Tantsura <[e-mail]>
> >>>>>> Subject: Re: [Lsr] FW: New Version Notification for
> >>>>>> draft-bonica-lsr-ip-flexalgo-00.txt
> >>>>>>
> >>>>>> [External Email. Be cautious of content]
> >>>>>>
> >>>>>>
> >>>>>> Hi Peter,
> >>>>>>
> >>>>>> Using flex-algo, a SRv6 locator can be associated with a single
> >>>>>> algo, which means an IPv6 or IPv4 address can also be associated
> >>>>>> with a single algo. So my understanding is Ron's proposal is
> >>>>>> making the
> >>>> configuration of flex-algo easier?
> >>>>>> Instead of using the exclude or include list you can configure a
> >>>>>> loopback address to a flex-algo directly?
> >>>>>>
> >>>>>> Thanks,
> >>>>>> Yingzhen
> >>>>>>
> >>>>>> On 10/3/20, 2:47 AM, "Peter Psenak" <[e-mail]> wrote:
> >>>>>>
> >>>>>>        Hi Yingzhen,
> >>>>>>
> >>>>>>        On 02/10/2020 22:15, Yingzhen Qu wrote:
> >>>>>>        > Hi Peter,
> >>>>>>        >
> >>>>>>        > My understanding of flex-algo is that for traffic
> >>>>>> destined to a prefix on a particular algo, it can only be routed
> >>>>>> on routers belong to that algo, which also means only routers in
> >>>>>> that algo calculates how to reach that prefix and install it into
> >>>>>> the routing table. It seems to me that using flex-algo (section
> >>>>>> 12 of the
> >>>>>> draft) it's possible to have a loopback address associated with
> >>>>>> only one algo, please correct me if I'm missing or misunderstood
> >> something.
> >>>>>>
> >>>>>>        you are right. That is exactly what is being done for flex-algo
> with
> >>>>>>        SRv6 - locator is associated with a single algo only. The
> >>>>>> proposal
> >> uses
> >>>>>>        the same concept.
> >>>>>>
> >>>>>>        thanks,
> >>>>>>        Peter
> >>>>>>
> >>>>>>        >
> >>>>>>        > Thanks,
> >>>>>>        > Yingzhen
> >>>>>>        >
> >>>>>>        > On 10/2/20, 9:43 AM, "Lsr on behalf of Peter Psenak"
> >>>>>> <[e-mail] on behalf of
> >>>>>> ppsenak=[e-mail]>
> >>>>>> wrote:
> >>>>>>        >
> >>>>>>        >      Gyan,
> >>>>>>        >
> >>>>>>        >      On 02/10/2020 18:30, Gyan Mishra wrote:
> >>>>>>        >      > All,
> >>>>>>        >      >
> >>>>>>        >      > With SRv6 and IP based flex algo a generic question
> as it
> >>>> applies
> >>>>>> to
> >>>>>>        >      > both. Is it possible to have within a single IGP
> domain
> >>>> different
> >>>>>> sets
> >>>>>>        >      > of nodes or segments of the network running
> different
> >>>>>> algorithms.
> >>>>>>        >
> >>>>>>        >      absolutely.
> >>>>>>        >
> >>>>>>        >      > From
> >>>>>>        >      > both drafts it sounds like all nodes have to agree on
> >> same
> >>>>>> algorithm
> >>>>>>        >      > similar to concept of metric and reference
> bandwidth
> >> all
> >>>> have to
> >>>>>> have
> >>>>>>        >      > the same style metric and play to the same sheet of
> >> music.
> >>>>>>        >
> >>>>>>        >      all participating nodes need to agree on the definition
> of
> >> the
> >>>>>> flex-algo
> >>>>>>        >      and advertise the participation. That's it.
> >>>>>>        >
> >>>>>>        >      > If there was
> >>>>>>        >      > a way to use multiple algorithms simultaneously
> based
> >> on
> >>>> SFC
> >>>>>> or services
> >>>>>>        >      > and instantiation of specific algorithm based on
> service
> >> to
> >>>> be
> >>>>>>        >      > rendered.  Doing so without causing a routing loop
> or
> >> sub
> >>>>>> optimal
> >>>>>>        >      > routing.
> >>>>>>        >
> >>>>>>        >      you can certainly use multiple algorithms
> simultaneously
> >> and
> >>>> use
> >>>>>> algo
> >>>>>>        >      specific paths to forward specific traffic over it. How
> that
> >> is
> >>>> done
> >>>>>>        >      from the forwarding perspective depends in which
> >>>> forwarding
> >>>>>> plane you
> >>>>>>        >      use. Flex-algo control plane is independent of the
> >> forwarding
> >>>>>> plane.
> >>>>>>        >
> >>>>>>        >
> >>>>>>        >      >I thought with flex algo that there exists a feature
> that
> >> on
> >>>>>>        >      > each hop there is a way to specify which algo to use
> >> hop by
> >>>> hop
> >>>>>> similar
> >>>>>>        >      > to a hop by hop policy based routing.
> >>>>>>        >
> >>>>>>        >      no, there is no hop-by-hop classification, that is
> >> problematic
> >>>> and
> >>>>>> does
> >>>>>>        >      not scale for high speeds. Classification is done at the
> >>>> ingress only.
> >>>>>>        >
> >>>>>>        >      thanks,
> >>>>>>        >      Peter
> >>>>>>        >
> >>>>>>        >      >
> >>>>>>        >
> >>>>>>        >
> >> _______________________________________________
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