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

[Jeff Tantsura <[e-mail]>]

Hi Aijun,

I understand very well what you are trying to achieve and don’t argue the need for it.  My point however - routing protocols are not the most suitable transport for it.

Regards,
Jeff

> On Apr 2, 2020, at 19:39, Aijun Wang <[e-mail]> wrote:
> 
> Hi, Jeff:
> The draft only propose to transfer the iFIT capability of the Node via the IGP protocol, not the telemetry data.
> As described in the draft, flooding such capability can assist the controller(it collects such information via the BGP-LS) to deploy the iFIT function at the path headend.
> 
> Aijun Wang
> China Telecom
> 
>>> On Apr 3, 2020, at 08:20, Jeff Tantsura <[e-mail]> wrote:
>>> 
>> Robert, 
>> 
>> We are deviating ;-)
>> 
>> There’s no feedback loop from telemetry producers back to the TE headend.
>> The telemetry, either end2end or postcards is sent to a  collector that has the context of the data and normalizes it so it can be consumed by an external system, being centralized or distributed PCE or anything else that could make use of it. Do you see IGP anywhere in between?
>> 
>> 
>> Regards,
>> Jeff
>> 
>>>> On Apr 2, 2020, at 16:03, Robert Raszuk <[e-mail]> wrote:
>>>> 
>>> 
>>> Hi Joel,
>>> 
>>> > Robert, you seem to be asking that we pass full information about the
>>> > dynamic network state to all routers  
>>> 
>>> No not at all. 
>>> 
>>> Only TE headends need this information. 
>>> 
>>> To restate ... I am not asking to have a synchronized input to all routes in the domain such that their computation would be consistent. 
>>> 
>>> I am only asking for TE headends to be able to select end to end paths based on the end to end inband telemetry data. I find this a useful requirement missing from any of today's operational deployments. 
>>> 
>>> Many thx,
>>> R. 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>>> On Fri, Apr 3, 2020 at 12:59 AM Joel M. Halpern <[e-mail]> wrote:
>>>> Robert, you seem to be asking that we pass full information about the 
>>>> dynamic network state to all routers so that they can, if needed, serve 
>>>> as fully intelligent path computation engines.  If you want to do that, 
>>>> you will need more than just the telemetry.  You will need the demands 
>>>> that are coming in to all of those routers, so that you can make global 
>>>> decisions sensibly.
>>>> Which is why we use quasi-centralized path computation engines.
>>>> 
>>>> Yours,
>>>> Joel
>>>> 
>>>> On 4/2/2020 6:16 PM, Robert Raszuk wrote:
>>>> > 
>>>> >      > If you consider such constrains to provide reachability for
>>>> >     applications you will likely see value that in-situ telemetry is
>>>> >     your friend here. Really best friend as without him you can not do
>>>> >     the proper end to end path exclusion for SPT computations..
>>>> > 
>>>> >     [as wg member] Are you thinking that shifting traffic to a router is
>>>> >     not going to affect it's jitter/drop rate?
>>>> > 
>>>> > 
>>>> > Well this is actually the other way around.
>>>> > 
>>>> > First you have your default topology. They you are asked to 
>>>> > construct new one based on applied constrains.
>>>> > 
>>>> > So you create complete TE coverage and start running end to end data 
>>>> > plane probing over all TE paths (say SR-TE for specific example). Once 
>>>> > you start collecting the probe results you can start excluding paths 
>>>> > which do not meet your applied constraints. And that process continues...
>>>> > 
>>>> > To your specific question - It is not that unusual where routers degrade 
>>>> > their performance with time and in many cases the traffic is not the 
>>>> > cause for it but internal bugs and malfunctions.
>>>> > 
>>>> > Best,
>>>> > R.
>>>> > 
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>>>> > https://www.ietf.org/mailman/listinfo/lsr
>>>> > 
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