Re: [Lsr] Working Group Last Call for draft-ietf-lsr-ip-flexalgo-04 - "IGP Flexible Algorithms (Flex-Algorithm) In IP Networks"

[Gyan Mishra <[e-mail]>]

Hi Acee

Responses in-line

On Sat, Apr 16, 2022 at 5:53 PM Acee Lindem (acee) <[e-mail]> wrote:

> Again, speaking as WG member:
>
> Hi Gyan, Ketan,
>
> I agree since for the IGPs we’ve traditionally used “application” for
> control plane routing applications (shortest-path, RSVP TE, SR, etc.). I
> know Robert suggested “logical data plane”… What are the thoughts on this?
>
> Gyan> I read through the comments on the thread related to ASLA and
> confusion with the word application defining a data plane which I and I
> think most in the WG agree the term application being applied to a data
> plane is no doubt confusing.
>
    I am good with “logical data plane”.   Data plane instance, identifier,
slice or transport would work as well.

>
>
> Thanks,
> Acee
>
>
>
> *From: *Gyan Mishra <[e-mail]>
> *Date: *Saturday, April 16, 2022 at 11:46 AM
> *To: *Ketan Talaulikar <[e-mail]>
> *Cc: *Acee Lindem <[e-mail]>, "Peter Psenak (ppsenak)" <
> [e-mail]>, "[e-mail]" <
> [e-mail]>, lsr <[e-mail]>
> *Subject: *Re: [Lsr] Working Group Last Call for
> draft-ietf-lsr-ip-flexalgo-04 - "IGP Flexible Algorithms (Flex-Algorithm)
> In IP Networks"
>
>
>
> Thank you Ketan.
>
>
>
> Ack on convergence on new term for application.😃
>
>
>
> Thanks
>
>
>
> Gyan
>
>
>
> On Sat, Apr 16, 2022 at 10:01 AM Ketan Talaulikar <[e-mail]>
> wrote:
>
> Hi Gyan,
>
>
>
> Your proposal looks ok to me. Note though that we seem to be converging
> towards using an alternate term instead of "application" in this context.
>
>
>
> Thanks,
>
> Ketan
>
>
>
>
>
> On Sat, Apr 16, 2022 at 12:50 PM Gyan Mishra <[e-mail]>
> wrote:
>
>
>
> Hi Ketan
>
>
>
> My understanding was that IGP Flex Algo could only be used with SR-MPLS or
> SRv6 data plane using prefix SID or SRv6 locator to steer packets.
>
>
>
> So it was my understanding that the IP Flex Algo draft was providing a
> solution for IP based networks ( Non SR-MPLS or SRv6) networks which was
> valuable gap to be filled.
>
>
>
> However your editorial comments shed some light that IGP Flex Algo may be
> used in  IP based ( Non SR-MPLD or SRv6) based networks.  This is confusing
> to me however below paragraph makes it more clear to me as to why you
> stated IGP Flex Algo is open to beyond SR ( even though not yet developed).
>
>
>
> IGP Flex Algo draft Section 14 describes forwarding plane use cases for
> Flex Algo which are SR-MPLS and SRv6 and 14.3 mentions that any application
> that wants to use Flex Algo can use it but that application needs to be
> developed to install the Flex Algo entires into the forwarding plane such
> as for RSVP-TE or native IPv4 or IPv6 forwarding plane.
>
>
>
> I think if IGP Flex Algo was developed as part of the draft to support
> other applications such as RSVP-TE and native IPv4 or IPv6 forwarding plane
> I think we could say that IGP Flex Algo can be used outside of SR data
> plane but that development has not been done even though it maybe possible
> in the future once developed or it may never be developed based on industry
> demand.  So I think it’s safe to say at this time IGP Flex Algo only
> supports SR-MPLS and SRv6 forwarding planes only.  However now once IP Flex
> Algo is published and implemented we can safely say that it has been
> extended beyond SR data plane.
>
>
>
> I would change the verbiage slightly to make it more clear.  You mention
> that the IGP Flex Algo draft is the base Flex Algo draft but I disagree as
> if it were then the IP Flex Algo draft or any other application of Flex
> Algo with a new data plane would be an update to the base Flex Algo draft
> but here in this case I don’t think so and even for any other application.
> Each data plane instance of Flex Algo starting with the IP Flex Algo draft
> and then maybe future RSVP Flex Algo draft would be their own independent
> “base” Flex Algo draft onto themselves.  That is one option, to keep each
> data plane specification of Flex Algo independent specifications.
>
>
>
>  If we think that IP Flex Algo and future data plane applications such as
> RSVP-TE and beyond will be extensions of the IGP Base specification, so
> then will be updates to the base specification, then I think we can call IP
> Flex Algo an extension to the base specification.
>
>
>
> This is what I think the verbiage should state which is a hybrid of yours
> and Peter’s verbiage.
>
>
>
> This is if each application is standalone per data plane  and is not an
> extension and so IGP Flex Algo would not be a base specification.
>
>
>
> NEW
>
>
>
> >     An IGP Flexible Algorithm (Flex-Algorithm) allows the IGP to compute
> >     constraint-based paths. The  IGP Flex-Algorithm specification
> >     currently only supports the application Segment Routing with (SR)
> data planes - SR MPLS and
> >     SRv6.
> >
> >     This document specifies IGP Flex-Algorithm, so that it can be used
>  in any IP network
> >     for native  IPv4 and IPv6 forwarding in the absence of SR.
>
>
>
>
>
> Verbiage if IGP Flex Algo is a base and this draft is an extension and
> updates the base.  We don’t have to say IGP Flex Algo currently only
> supports dropping the word currently as we are now extending with IP Flex
> Algo.
>
>
>
> > NEW
> >
> >     An IGP Flexible Algorithm (Flex-Algorithm) allows the IGP to compute
> >     constraint-based paths. The base IGP Flex-Algorithm specification
> only supports the application Segment Routing with (SR) data planes - SR
> MPLS and SRv6.
> >
> >     This document extends IGP Flex-Algorithm, so that it can be used
> >     natively with IPv4 and IPv6 forwarding.
>
>
>
>
>
>
>
>
>
> Kind Regards
>
>
>
> Gyan
>
>
>
> Sent from my iPhone
>
>
>
> On Apr 16, 2022, at 12:21 AM, Ketan Talaulikar <[e-mail]>
> wrote:
>
> Hi Gyan,
>
>
>
> I am not sure what the confusion is here. The following is how Peter and I
> concluded this point. My comment was of editorial nature.
>
>
>
> Thanks,
>
> Ketan
>
>
>
> >      > 3) This draft makes assertions that IGP FlexAlgo cannot be
> deployed
> >      > without SR. This is not true since the base IGP FlexAlgo spec
> >     explicitly
> >      > opens it up for usage outside of the SR forwarding plane. We
> already
> >      > have BIER and MLDP forwarding planes as users of the IGP
> >     FlexAlgo. My
> >      > suggestion is to remove such assertions from the document. It is
> >      > sufficient to just say that the document enables the use of IGP
> >     FlexAlgo
> >      > for IP prefixes with native IP forwarding.
> >
> >     ##PP
> >     where do you see such assertion? Each flex-algo data-plane/app can be
> >     deployed independently.
> >
> >
> > KT> Let me clarify what I meant by taking the example of the abstract.
> >
> > OLD
> >
> >     An IGP Flexible Algorithm (Flex-Algorithm) allows IGP to compute
> >     constraint-based paths.  As currently defined, IGP Flex-Algorithm is
> >     used with Segment Routing (SR) data planes - SR MPLS and SRv6.
> >     Therefore, Flex-Algorithm cannot be deployed in the absence of SR.
> >
> >     This document extends IGP Flex-Algorithm, so that it can be used for
> >     regular IPv4 and IPv6 prefixes.  This allows Flex-Algorithm to be
> >     deployed in any IP network, even in the absence of SR.
> >
> >
> > NEW
> >
> >     An IGP Flexible Algorithm (Flex-Algorithm) allows IGP to compute
> >     constraint-based paths. The base IGP Flex-Algorithm document
> >     specified use with Segment Routing (SR) data planes - SR MPLS and
> >     SRv6.
> >
> >     This document extends IGP Flex-Algorithm, so that it can be used with
> >     regular IPv4 and IPv6 forwarding.
>
> ##PP2
> ok
>
>
>
> On Sat, Apr 16, 2022 at 8:07 AM Gyan Mishra <[e-mail]> wrote:
>
>
>
> Hi Acee
>
>
>
> Fixing a typo
>
>
>
> On Fri, Apr 15, 2022 at 10:34 PM Gyan Mishra <[e-mail]>
> wrote:
>
>
>
> Hi Acee
>
>
>
> My question cane up from the list of questions posed by Ketan and Peter’s
> response to question #3.
>
>
>
> See excerpt below.
>
>
>
> I am confused by what Ketan stated in his question below and also Peter’s
> response which is why I am asking the question again.
>
>
>
> I believe the goal of the draft is for Flex Ago to be deployed
> independently of SR filling the gap of IGP Flex Algo providing that
> solution.  So based on what Ketan stated in his question that IGP Flex Algo
> is data plane agnostic and can be used with IP data plane then there is no
> gap to be filled by this draft.
>
>
>
> Maybe I am misreading Ketan’s question.
>
>
>
> So this is a very important point made by Ketan that if IGP Flex Algo is
> open to usage “outside of SR”,  then it is very important to restate the
> goal of this draft, removing assertions in the draft that this draft is for
> non SR IP data planes, as that can be accomplished today by IGP Flex Algo,
> and the gap or new solution being filled by this draft is for IP prefix
> based Flex Algo with Native IP Forwarding.
>
>
>
> This as well is quite confusing to me as if IGP Flex Algo can be used
> outside of SR then can do everything that this draft is supposed to
> accomplish.
>
>
>
> So what then is the purpose of this draft?
>
>
>
> In Peter’s response is stated that each Flex Algo data plane / app can be
> deployed independently meaning this draft and IGP flex Algo can act as 2
> ships in the night.  Also confusing.
>
>
>
> 3) This draft makes assertions that IGP FlexAlgo cannot be deployed
> > without SR. This is not true since the base IGP FlexAlgo spec explicitly
> > opens it up for usage outside of the SR forwarding plane. We already
> > have BIER and MLDP forwarding planes as users of the IGP FlexAlgo. My
> > suggestion is to remove such assertions from the document. It is
> > sufficient to just say that the document enables the use of IGP FlexAlgo
> > for IP prefixes with native IP forwarding.
>
> ##PP
> where do you see such assertion? Each flex-algo data-plane/app can be
> deployed independently.
>
>
>
>
>
>
>
> On Fri, Apr 15, 2022 at 7:51 PM Acee Lindem (acee) <[e-mail]> wrote:
>
> Gyan,
>
>
>
> What is your point here? Is this a trick question?
>
>
>
> Thanks,
>
> Acee
>
>
>
> *From: *Gyan Mishra <[e-mail]>
> *Date: *Friday, April 15, 2022 at 5:31 PM
> *To: *"Peter Psenak (ppsenak)" <[e-mail]>
> *Cc: *Acee Lindem <[e-mail]>, Ketan Talaulikar <
> [e-mail]>, "[e-mail]" <
> [e-mail]>, "[e-mail]" <[e-mail]>
> *Subject: *Re: [Lsr] Working Group Last Call for
> draft-ietf-lsr-ip-flexalgo-04 - "IGP Flexible Algorithms (Flex-Algorithm)
> In IP Networks"
>
>
>
>
>
> Hi Peter
>
>
>
> My understanding is that the main goal of this draft is to be able to use
> flex algo over IPv4 or IPv6 data plane as that is not possible with
> existing Flex Algo which can only be used on SR data plane.
>
>
>
> Is that correct or am I missing something?
>
>
>
> https://datatracker.ietf.org/doc/html/draft-ietf-lsr-ip-flexalgo
>
>
>
>
>
> Abstract
>
>
>
>    An IGP Flexible Algorithm (Flex-Algorithm) allows IGP to compute
>
>    constraint-based paths.  As currently defined, IGP Flex-Algorithm is
>
>    used with Segment Routing (SR) data planes - SR MPLS and SRv6.
>
>    Therefore, Flex-Algorithm cannot be deployed in the absence of SR.
>
>
>
>    This document extends IGP Flex-Algorithm, so that it can be used for
>
>    regular IPv4 and IPv6 prefixes.  This allows Flex-Algorithm to be
>
>    deployed in any IP network, even in the absence of SR.
>
>
>
> https://datatracker.ietf.org/doc/html/draft-ietf-lsr-flex-algo-19
>
>
>
> Abstract
>
>
>
>    IGP protocols traditionally compute best paths over the network based
>
>    on the IGP metric assigned to the links.  Many network deployments
>
>    use RSVP-TE based or Segment Routing based Traffic Engineering to
>
>    steer traffic over a path that is computed using different metrics or
>
>    constraints than the shortest IGP path.  This document proposes a
>
>    solution that allows IGPs themselves to compute constraint-based
>
>    paths over the network.  This document also specifies a way of using
>
>    Segment Routing (SR) Prefix-SIDs and SRv6 locators to steer packets
>
>    along the constraint-based paths.
>
>
>
> Kind Regards
>
>
>
> Gyan
>
>
>
>
>
> --
>
> [image: Image removed by sender.] <http://www.verizon.com/>
>
> *Gyan Mishra*
>
> *Network Solutions Architect *
>
> *Email [e-mail] <[e-mail]>*
>
> *M 301 502-1347*
>
>
>
-- 

<http://www.verizon.com/>

*Gyan Mishra*

*Network Solutions A**rchitect *

*Email [e-mail] <[e-mail]>*



*M 301 502-1347*