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

[Peter Psenak <[e-mail]>]

Robert,


On 13/10/2020 13:38, Robert Raszuk wrote:
> Peter,
> 
> If this is per app how are the constraints shared across apps ?

FAD constraints are only used for calculating the flex-algo path.

> 
> See we have single physical resources (for example links) and single 
> interface outbound queues. If I use per app flex-algo and do not have 
> central controller how is this going to work in practice for any network 
> which attempts to use more then one forwarding schema with dynamic 
> constraints ?

flex-algo defines the way to calculate constraint based paths in a 
distributed manner and guarantees the loop free forwarding over such path.

Possible per app and/or per algo resource allocation at each hop is not 
something that flex-algo spec attempts to solve. That does not mean it 
is not possible. I don't see anything in the flex-algo spec that would 
prevent one to do that.

thanks,
Peter

> 
> Many thx,
> R.
> 
> 
> 
> On Tue, Oct 13, 2020 at 10:52 AM Peter Psenak 
> <ppsenak=[e-mail] <mailto:[e-mail]>> 
> wrote:
> 
>     Hi Jimmy,
> 
>     On 13/10/2020 10:02, Dongjie (Jimmy) wrote:
>      > Hi Peter,
>      >
>      > Thanks for your reply. Please see further inline:
>      >
>      >> -----Original Message-----
>      >> From: Lsr [mailto:[e-mail]
>     <mailto:[e-mail]>] On Behalf Of Peter Psenak
>      >> Sent: Monday, October 12, 2020 4:39 PM
>      >> To: Dongjie (Jimmy) <[e-mail]
>     <mailto:[e-mail]>>; Ron Bonica
>      >> <[e-mail] <mailto:[e-mail]>>; Yingzhen Qu
>     <[e-mail] <mailto:[e-mail]>>; Gyan
>      >> Mishra <[e-mail] <mailto:[e-mail]>>
>      >> Cc: [e-mail] <mailto:[e-mail]>; Jeff Tantsura
>     <[e-mail] <mailto:[e-mail]>>
>      >> Subject: Re: [Lsr] FW: New Version Notification for
>      >> draft-bonica-lsr-ip-flexalgo-00.txt
>      >>
>      >> Hi Jimmy,
>      >>
>      >> On 10/10/2020 05:05, Dongjie (Jimmy) wrote:
>      >>> Hi Peter,
>      >>>
>      >>> Thanks for your reply. It aligns with my understanding of FAD,
>     which is just a
>      >> set of constraints for path computation. Thus one Flex-Algo ID
>     could be used
>      >> with multiple different data planes. Is this understanding correct?
>      >>
>      >> correct.
>      >>
>      >>>
>      >>> If so, my question is about the scenario below:
>      >>>
>      >>> A group of nodes in a network support FA-128, a sub-group of
>     them bind
>      >> FA-128 to SR SIDs, another sub-group of them bind FA-128 to IP
>     address.
>      >>
>      >> just to use the correct terminology, we should use "participate"
>     instead of
>      >> "support".
>      >
>      > Agree.
>      >
>      >>
>      >>> 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.
> 
>     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.
> 
>     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]
>     <mailto:[e-mail]>] On Behalf Of Peter Psenak
>      >>>> Sent: Friday, October 9, 2020 11:58 PM
>      >>>> To: Dongjie (Jimmy) <[e-mail]
>     <mailto:[e-mail]>>; Ron Bonica
>      >>>> <rbonica=[e-mail]
>     <mailto:[e-mail]>>; Yingzhen Qu
>      >>>> <[e-mail]
>     <mailto:[e-mail]>>; Gyan Mishra
>     <[e-mail] <mailto:[e-mail]>>
>      >>>> Cc: [e-mail] <mailto:[e-mail]>; Jeff Tantsura
>     <[e-mail] <mailto:[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]
>     <mailto:[e-mail]>] On Behalf Of Ron Bonica
>      >>>>>> Sent: Sunday, October 4, 2020 4:34 AM
>      >>>>>> To: Yingzhen Qu <[e-mail]
>     <mailto:[e-mail]>>; Peter Psenak
>      >>>>>> <[e-mail] <mailto:[e-mail]>>; Gyan Mishra
>     <[e-mail] <mailto:[e-mail]>>
>      >>>>>> Cc: [e-mail] <mailto:[e-mail]>; Jeff Tantsura
>     <[e-mail] <mailto:[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]
>     <mailto:[e-mail]>>
>      >>>>>> Sent: Saturday, October 3, 2020 2:08 PM
>      >>>>>> To: Peter Psenak <[e-mail]
>     <mailto:[e-mail]>>; Gyan Mishra
>      >>>>>> <[e-mail] <mailto:[e-mail]>>; Ron
>     Bonica <[e-mail] <mailto:[e-mail]>>
>      >>>>>> Cc: [e-mail] <mailto:[e-mail]>; Jeff Tantsura
>     <[e-mail] <mailto:[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]
>     <mailto:[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] <mailto:[e-mail]> on behalf of
>      >>>>>> ppsenak=[e-mail]
>     <mailto:[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
>      >>>>>>        >
>      >>>>>>        >      >
>      >>>>>>        >
>      >>>>>>        >
>      >> _______________________________________________
>      >>>>>>        >      Lsr mailing list
>      >>>>>>        > [e-mail] <mailto:[e-mail]>
>      >>>>>>        >
>      >>>>>>
>     https://urldefense.com/v3/__https://nam11.safelinks.protection.outl
>      >>>>>> oo
>      >>>>>> k.com/ <http://k.com/>
>      >>>>>> ?url=https*3A*2F*2Fwww.ietf.org
>     <http://2Fwww.ietf.org>*2Fmailman*2Flistinfo*2Flsr&amp;data
>      >>>>>> =
>      >>>> 0
>      >>>>>> 2
>      >>>>>>
>      >>>>
>      >> *7C01*7Cyingzhen.qu*40futurewei.com
>     <http://40futurewei.com>*7Cfe03124c6e414e067c2008d86781
>      >>>>>>
>      >>>>
>      >> 6541*7C0fee8ff2a3b240189c753a1d5591fedc*7C1*7C0*7C63737315273986
>      >>>>>>
>      >>>>
>      >> 5126&amp;sdata=WI48cEAan*2FOkDPmVXGurEAjPItNGF9p9PDQIlD1ip0g*3D
>      >>>>>>
>      >>>>
>      >>
>     &amp;reserved=0__;JSUlJSUlJSUlJSUlJSUlJQ!!NEt6yMaO-gk!X1fRln9MjimeJcR
>      >>>>>> EUEIydr-8IIbtNonXMs83eoXvRww6xkaQfVUdNh0kK452GP-G$
>      >>>>>>        >
>      >>>>>>        >
>      >>>>>>        >
>      >>>>>>
>      >>>>>> _______________________________________________
>      >>>>>> Lsr mailing list
>      >>>>>> [e-mail] <mailto:[e-mail]>
>      >>>>>> https://www.ietf.org/mailman/listinfo/lsr
>      >>>>>
>      >>>>>
>      >>>>
>      >>>> _______________________________________________
>      >>>> Lsr mailing list
>      >>>> [e-mail] <mailto:[e-mail]>
>      >>>> https://www.ietf.org/mailman/listinfo/lsr
>      >>>
>      >>>
>      >>
>      >> _______________________________________________
>      >> Lsr mailing list
>      >> [e-mail] <mailto:[e-mail]>
>      >> https://www.ietf.org/mailman/listinfo/lsr
>      >
>      >
> 
>     _______________________________________________
>     Lsr mailing list
>     [e-mail] <mailto:[e-mail]>
>     https://www.ietf.org/mailman/listinfo/lsr
>