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

Gyan Mishra <hayabusagsm@gmail.com> Sat, 03 October 2020 17:45 UTC

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From: Gyan Mishra <hayabusagsm@gmail.com>
Date: Sat, 03 Oct 2020 13:25:51 -0400
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To: Peter Psenak <ppsenak@cisco.com>
Cc: Jeff Tantsura <jefftant.ietf@gmail.com>, Ron Bonica <rbonica@juniper.net>, Yingzhen Qu <yingzhen.qu@futurewei.com>, "lsr@ietf.org" <lsr@ietf.org>
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Subject: Re: [Lsr] FW: New Version Notification for draft-bonica-lsr-ip-flexalgo-00.txt
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I would think Ron’s IP data plane based flex algo would work identical to
SR data plane based flex algo with the base Strict  algo 0 providing top
layer all node reachability and would contain let’s say loopback0.  The
algo would have algo and algo # definition on the loopback so the nodes are
reachability the discrete non zero algo loopback  for the corresponding
loopbacks that correlate with algo xyz for the xyz topology.  In both IP
based algo and the SR based algo would the SR locator or IP based algo be
in the BAU base to layer topology SRv6-BE let’s say and SRv6-TE SLA SRH
steered would map to non zero algorithms per VRF VPN coloring and  would IP
based algo do the same.

The advent of SR came about filling a much needed gap for operators to
provide RSVP TE style per VRF coloring without the added badge of loopback
xyz rewrite for the static route coloring issue that you need a separate
loopback and static route to RSVP tunnel to steer each per VRF per vpn
colored TE tunnel - as you can see with RSVP coloring you have a 1-1
mapping discrete loopback per per VRF steered TE tunnel.

So then along came SR to save the day ..end of story..

Back to flex algo ..so SR has the per VRF coloring capability with SR data
plane to provide the coloring.

I think I maybe confusing to topics as the per VRF TE coloring is using
underlay to steer overlay so flex algo is in the underlay so you could do
the same SR-TE flex algo steering of underlay thereby steering vpn overlay
under pinning of underlay to overlay.

How would that be done with IP based flex algo.

So with IP based flex algo as well you would be global table routing with
no VPN framework.

Thanks

Gyan

On Sat, Oct 3, 2020 at 12:54 PM Gyan Mishra <hayabusagsm@gmail.com> wrote:

>
> Thanks Peter for the responses to help clear up my flex algo
> understanding!!
>
> On Sat, Oct 3, 2020 at 5:45 AM Peter Psenak <ppsenak@cisco.com> wrote:
>
>> Gyan,
>>
>>
>>
>> On 03/10/2020 02:14, Gyan Mishra wrote:
>>
>> >
>>
>> > Hi  Jeff
>>
>> >
>>
>> >  From a domain perspective where you have a group of nodes and
>>
>> > associated IP addressed and SID are part of a discrete underlay
>> instance
>>
>> > flex algo topology.  On those same set of nodes you could have another
>>
>> > topology and associated address and SIDs for a different flex algo.
>>
>>
>>
>> above is right.
>>
>
>    Gyan>  So per my response to Robert, what  I was thinking is that as
> the algo 0 strict spf would be used as the base algo to provide
> reachability to all nodes within the domain and all neighbors are formed
> between all nodes in the domain to populate IGP rib providing base
> connectivity reachability.  So then underneath of that you can have any
> subset of nodes out of the superset all top layer domain nodes level  that
> can run any other algo desired. Basically creating algo layers under the
> top domain wide layer.
>
>>
>>
>>
>> > How
>>
>> > this would work is that the topologies would have to be segregated from
>>
>> > each other as different MT instances or routing process instances.  Is
>>
>> > that correct?
>>
>>
>>
>> no MT at all. You can think of each flex-algo as a set of constraints
>>
>> that is used to calculate the path over the common topology. You can
>>
>> have many such felx-algos running on a common topology.
>>
>>
>     Gyan> Is it safe to say that we can think of it as RSVP TE “like” cSPF
> constraints that we are build via traffic engineering PCALC algorithms to
> run for dynamic LSP dyamic ERO that is built based on IGP constraints from
> TEDs database of TE link attributes and TE or IGP weights metric
> constraints to create the dynamic LSP path.  So we could think of in TE
> framework analogy to flex algo In the per VRF TE next hop vpn coloring use
> case with different loopback next hop rewrite per VRF that normal IGP non
> TE BAU VPNs traffic would be like the flex algo base strict algo 0 and the
> non zero discrete algo would be like the per VRF next hop loopback rewrite
> where each per VRF te loopback rewrite would be a different steering non
> zero discrete flex algo all running in parallel as ships in the night with
> the base algo 0.   Sorry for the complex analogy but I think I am getting
> it!!😃
>
> Does a flex algo use case draft exist and if not I would not mind using
> the analogy I said above and build out a use case draft.  Cheers! 😊
>
>>
>>
>>
>> >
>>
>> > Can two nodes that run two different flex algo become ospf or isis
>>
>> > neighbors?
>>
>>
>>
>> absolutely.
>>
>>
>>
>> Peter
>>
>>
>>
>> >
>>
>> > Kind Regards
>>
>> >
>>
>> > Gyan
>>
>> >
>>
>> > On Fri, Oct 2, 2020 at 6:25 PM Jeff Tantsura <jefftant.ietf@gmail.com
>>
>> > <mailto:jefftant.ietf@gmail.com>> wrote:
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >     Hi Yingzhen,
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >     Yes, that’s the case.  The most important property of an algo
>>
>> >     computed path is that is has to be consecutive, as either SID or IP
>>
>> >     address associated with a particular topology is only known within
>>
>> >     that topology.
>>
>> >
>>
>> >
>>
>> >     Looking specifically at Ron’s draft (MPLS could be more complex due
>>
>> >     to potential hierarchy) - the prefix itself defines the
>>
>> >     context(topology) and must be globally unique, since IPv4 header
>>
>> >     can’t have any additional meta-data attached.
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >     Cheers,
>>
>> >
>>
>> >     Jeff
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >     On Oct 2, 2020, 1:15 PM -0700, Yingzhen Qu
>>
>> >     <yingzhen.qu@futurewei.com <mailto:yingzhen.qu@futurewei.com>>,
>> 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.
>>
>> >>
>>
>> >>
>>
>> >>
>>
>> >>
>>
>> >>
>>
>> >>     Thanks,
>>
>> >>
>>
>> >>
>>
>> >>     Yingzhen
>>
>> >>
>>
>> >>
>>
>> >>
>>
>> >>
>>
>> >>
>>
>> >>     On 10/2/20, 9:43 AM, "Lsr on behalf of Peter Psenak"
>>
>> >>     <lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org> on behalf of
>>
>> >>     ppsenak=40cisco.com@dmarc.ietf.org
>>
>> >>     <mailto: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 <mailto:Lsr@ietf.org>
>>
>> >>
>>
>> >>
>>
>> >>
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ietf.org%2Fmailman%2Flistinfo%2Flsr&amp;data=02%7C01%7Cyingzhen.qu%40futurewei.com%7C51dd940ab25d4ea19b1b08d866f23b6a%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637372537869296887&amp;sdata=R%2FI%2BAUkcw12FmgDtsh%2FBOL7zLjPF%2BwwRpqwnE2Ndv%2Fg%3D&amp;reserved=0
>>
>> >>
>>
>> >>
>>
>> >>
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> >
>>
>> > --
>>
>> >
>>
>> > <http://www.verizon.com/>
>>
>> >
>>
>> > *Gyan Mishra*
>>
>> >
>>
>> > /Network Solutions A//rchitect /
>>
>> >
>>
>> > /M 301 502-1347
>>
>> > 13101 Columbia Pike
>>
>> > /Silver Spring, MD
>>
>> >
>>
>> >
>>
>>
>>
>> --
>
> <http://www.verizon.com/>
>
> *Gyan Mishra*
>
> *Network Solutions A**rchitect *
>
>
>
> *M 301 502-134713101 Columbia Pike *Silver Spring, MD
>
>
>
> --

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

*Gyan Mishra*

*Network Solutions A**rchitect *



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