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

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:lsr-bounces@ietf.org] On Behalf Of Peter Psenak
>> Sent: Monday, October 12, 2020 4:39 PM
>> To: Dongjie (Jimmy) <jie.dong@huawei.com>; Ron Bonica
>> <rbonica@juniper.net>; Yingzhen Qu <yingzhen.qu@futurewei.com>; Gyan
>> Mishra <hayabusagsm@gmail.com>
>> Cc: lsr@ietf.org; Jeff Tantsura <jefftant.ietf@gmail.com>
>> 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:lsr-bounces@ietf.org] On Behalf Of Peter Psenak
>>>> Sent: Friday, October 9, 2020 11:58 PM
>>>> To: Dongjie (Jimmy) <jie.dong@huawei.com>; Ron Bonica
>>>> <rbonica=40juniper.net@dmarc.ietf.org>; Yingzhen Qu
>>>> <yingzhen.qu@futurewei.com>; Gyan Mishra <hayabusagsm@gmail.com>
>>>> Cc: lsr@ietf.org; Jeff Tantsura <jefftant.ietf@gmail.com>
>>>> 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:lsr-bounces@ietf.org] On Behalf Of Ron Bonica
>>>>>> Sent: Sunday, October 4, 2020 4:34 AM
>>>>>> To: Yingzhen Qu <yingzhen.qu@futurewei.com>; Peter Psenak
>>>>>> <ppsenak@cisco.com>; Gyan Mishra <hayabusagsm@gmail.com>
>>>>>> Cc: lsr@ietf.org; Jeff Tantsura <jefftant.ietf@gmail.com>
>>>>>> 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 <yingzhen.qu@futurewei.com>
>>>>>> Sent: Saturday, October 3, 2020 2:08 PM
>>>>>> To: Peter Psenak <ppsenak@cisco.com>; Gyan Mishra
>>>>>> <hayabusagsm@gmail.com>; Ron Bonica <rbonica@juniper.net>
>>>>>> Cc: lsr@ietf.org; Jeff Tantsura <jefftant.ietf@gmail.com>
>>>>>> 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" <ppsenak@cisco.com> 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"
>>>>>> <lsr-bounces@ietf.org on behalf of
>>>>>> ppsenak=40cisco.com@dmarc.ietf.org>
>>>>>> 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
>>>>>>        >      Lsr@ietf.org
>>>>>>        >
>>>>>> https://urldefense.com/v3/__https://nam11.safelinks.protection.outl
>>>>>> oo
>>>>>> k.com/
>>>>>> ?url=https*3A*2F*2Fwww.ietf.org*2Fmailman*2Flistinfo*2Flsr&amp;data
>>>>>> =
>>>> 0
>>>>>> 2
>>>>>>
>>>>
>> *7C01*7Cyingzhen.qu*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
>>>>>> Lsr@ietf.org
>>>>>> https://www.ietf.org/mailman/listinfo/lsr
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
>>>> Lsr mailing list
>>>> Lsr@ietf.org
>>>> https://www.ietf.org/mailman/listinfo/lsr
>>>
>>>
>>
>> _______________________________________________
>> Lsr mailing list
>> Lsr@ietf.org
>> https://www.ietf.org/mailman/listinfo/lsr
> 
> 