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

[Gyan Mishra <[e-mail]>]

Thanks Peter!

On Fri, Oct 2, 2020 at 12:42 PM Peter Psenak <[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.


   Gyan> Great.  As was noted on the thread that with SR-MPLS you can have
multiple labels and each label bound to a different algorithm for a service
prefix, however that is not possible with SRv6 as it’s a 1-1 binding
destination prefix to SRv6 sid.  With SRv6 standard longest prefix matching
 can you  also have different sets of nodes running different algorithms
within the same domain.  SRv6 has the advantage of LPM but SR-MPLS does
seem to have an advantage of being able to have multiple algorithms tied to
a label bound to the same FEC.  That does seem to be an advantageous
feature with SR-MPLS - MPLS data plane use of flex algo as compare to SRv6.

>
>
>
> > 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.
>

    Gyan> Trying to picture how it would work if you had let’s say all
nodes in a single IGP domain or MT instance running let’s say 2 different
algorithms simultaneously.  Would it be like 2 different routing overlay
IGP instances or ISIS MT instance or ospf process.  Also would that work
with just SR-MPLS or would that also work with SRv6?  In the case where you
have groups of nodes running a different algorithm the adjacent border
nodes between the groupings would end up running multiple  algorithms.  So
it can work and not issue with routing loops or sub optimal routing.

>
>
>
> > 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.
>
> Gyan> Is there a flex algo use case draft?
>
>
>
> >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.
>
> Gyan>  Is the classification of interesting traffic base on QOS marking on
> ingress to map to a specific flex algo for a particular service?
>
> thanks,
>
> Peter
>
>
>
> >
>
>
>
> --

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

*Gyan Mishra*

*Network Solutions A**rchitect *



*M 301 502-134713101 Columbia Pike *Silver Spring, MD