Re: [Lsr] A new version of I-D, draft-liu-lsr-isis-ifit-node-capability-02

[Robert Raszuk <[e-mail]>]

Hi Tony,

I think there is still some disconnect - so in an attempt to at least make
sure that we have difference of opinions let me try to restate what I was
suggesting.

IGP would only carry indication if tail can do inband telemetry or not - it
would *not* carry any telemetry data. IGP would not be running telemetry -
it will be just consumer of other subsystem product.
https://tools.ietf.org/html/draft-wang-lsr-ifit-node-capability-advertisement-00
just signals capability. It does not even have a trunk for any type of dump
:)

Global optimization makes a lot of sense for traffic spread across given
network - 100%. But it is not the best place to only select if one path is
eligible and the other is not in given topology. That decision should
happen on the headends and should be as much distributed as possible. And
the data here as input to the decision is only valid on specific headend
probes depart from. Besides it has usually a very short life.

Even if we move cspf to historic just very recently flexible algorithm was
proposed and I think is progressing fine. So my examples of use cases to
choose paths with min drops or bound jitter are real.

Hi Jeff,

If I look at one of the in situ data plane proposals it does send the
results to the sender/originator vs some
collector. draft-lapukhov-dataplane-probe-01 This is besides the point of
this discussion as we are not asking for IGP to carry the results. Hint:
Each headend can be a collector or nothing breaks in the design if headend
get's this data out of band from central collector.

Thx,
R.


On Fri, Apr 3, 2020 at 1:43 AM <[e-mail]> wrote:

>
> Sure it is possible to discover if my tailends are capable of handling in
> band telemetry by off line means. But what I am struggling to see why we
> allowed so much TE stuff into IGPs and we do not want to make it easier for
> headends to operate without PCE at all for the purpose of delivering
> such type of services.
>
>
>
> AFAICT, we put a lot of effort into making headend path computation useful
> and, for the most part, it was and is not necessary.
>
> Even with legacy mechanisms, people decided that they need global
> optimization and that head-end path computation was Not That Interesting.
>
> It’s now 20 years later, the network is even more dynamic, the
> expectations about response time are that much higher, and concerns about
> link state database stability and scalability have increased.  Modern
> telemetry is definitely not suitable to be passed in the IGP anymore.
>
> Thus, it seems like the IGP can provide base topology information and
> traffic engineering constructs should leverage that and provide an
> independent telemetry collection plane. Within that plane, telemetry
> capabilities can and should be confined to the telemetry plane.
>
> As we’ve said many times before: BGP is not a dump truck. Analogously, the
> IGP isn’t even an SUV.
>
> ;-)
>
> Regards,
> Tony
>
>