Re: [Lsr] Generic metric: application-specific vs application-independent

[Shraddha Hegde <[e-mail]>]

Peter,

>no, I don't want to use affinities to do that. That's the whole point.
>ASLA gives you per link per application signaling. No need to use affinities.

The usecase you are describing to exclude links from an application topology is very straight 
forward and how this is done is defined by applications.
TE applications have defined a topology filter data model that uses 
link-affinities to Include/exclude links from topology 
 https://datatracker.ietf.org/doc/html/draft-bestbar-teas-yang-topology-filter-00. 
 In your example if application B is any TE application it would be natural to use link-affinities.

If application B is LFA, RFC 7916 defines link-coloring and include exclude policies to be used (Refer sec 6.2.3).
so it cannot use application bits on metric to exclude links.

If we assume application A and B are both Flex-algos, ASLA  
natively doesn't support Per flex-algo attribute advertisement 
and it is extremely complex to define user-defined bit masks for Each 
flex-algo and assign the bit masks on the metric on every router. 
Operator could use link-affinities to Exclude links 
from flex-algo topology which is much simpler.

Rgds
Shraddha


Juniper Business Use Only

-----Original Message-----
From: Peter Psenak <[e-mail]> 
Sent: Saturday, July 31, 2021 1:07 AM
To: Shraddha Hegde <[e-mail]>; Robert Raszuk <[e-mail]>; Van De Velde, Gunter (Nokia - BE/Antwerp) <[e-mail]>
Cc: Les Ginsberg (ginsberg) <[e-mail]>; Tony Li <[e-mail]>; [e-mail]
Subject: Re: [Lsr] Generic metric: application-specific vs application-independent

[External Email. Be cautious of content]


Shraddha,

On 30/07/2021 18:45, Shraddha Hegde wrote:
> Peter,
>
>> imagine you have an application A and B and a link X. You advertise application independent metric M on that link X >because you want application A to use it.
>
>> Application B is also enabled to use the metric M, but you do not want application B to use metric M on the link X >(because you do not want application B to include the link X in its topology). How do you do that without ASLA? The >answer is you can't.
>
> This is very straight forward to do without ASLA.
>   I would define an admin-group and assign that admin group on link X and
>   exclude that admin-group from Application B.
>   This is much common way how
>   operators exclude links from the topology.

no, I don't want to use affinities to do that. That's the whole point.
ASLA gives you per link per application signaling. No need to use affinities.

>
>   The alternative being proposed with ASLA is much more fragile.
>   An operator would have to set the bits for application A and Application B
>   for metric M on every link that he wants to include and reset the
>   application bit B on links that he wants to exclude for application B.

sorry, but setting affinities is not any easier, so the above argument is not valid.


Peter



>   Imagine what would happen if he missed setting the bit or resetting
>   the bit on some of the links and how difficult it would be to debug.
>
> Rgds
> Shraddha
>
>
> Juniper Business Use Only
>
> -----Original Message-----
> From: Peter Psenak <[e-mail]>
> Sent: Friday, July 30, 2021 7:09 PM
> To: Shraddha Hegde <[e-mail]>; Robert Raszuk 
> <[e-mail]>; Van De Velde, Gunter (Nokia - BE/Antwerp) 
> <[e-mail]>
> Cc: Les Ginsberg (ginsberg) <[e-mail]>; Tony Li 
> <[e-mail]>; [e-mail]
> Subject: Re: [Lsr] Generic metric: application-specific vs 
> application-independent
>
> [External Email. Be cautious of content]
>
>
> Shraddha,
>
>
> On 30/07/2021 15:22, Shraddha Hegde wrote:
>> Robert,
>>
>>   > Can anyone explain how do I map generic metric to selected 
>> network applications I am to run in the network ?
>>
>> Which application uses which metric type is defined by the application.
>
> imagine you have an application A and B and a link X. You advertise application independent metric M on that link X because you want application A to use it.
>
> Application B is also enabled to use the metric M, but you do not want application B to use metric M on the link X (because you do not want application B to include the link X in its topology). How do you do that without ASLA? The answer is you can't.
>
> thanks,
> Peter
>
>>
>> For example in flex-algo FAD defines which metric-type its going to use.
>>
>> In SR-TE, the constraint list specifies which metric-type it is going 
>> to use.
>>
>> Rgds
>>
>> Shraddha
>>
>> Juniper Business Use Only
>>
>> *From:* Robert Raszuk <[e-mail]>
>> *Sent:* Friday, July 30, 2021 6:20 PM
>> *To:* Van De Velde, Gunter (Nokia - BE/Antwerp) 
>> <[e-mail]>
>> *Cc:* Peter Psenak <[e-mail]>; Shraddha Hegde 
>> <[e-mail]>; Les Ginsberg (ginsberg) <[e-mail]>; 
>> Tony Li <[e-mail]>; [e-mail]
>> *Subject:* Re: [Lsr] Generic metric: application-specific vs 
>> application-independent
>>
>> *[External Email. Be cautious of content]*
>>
>> Hey Gunter,
>>
>>   > It doesn’t make sense to have Application specific values if a 
>> particular metric is obtained only dynamically,
>>
>> It sure does.
>>
>> Please notice what ASLA RFCs say up front in the abstract. ASLA is 
>> useful for:
>>
>> A) application- specific values for a given attribute
>>
>> AND
>>
>> B) indication of which applications are using the advertised value 
>> for a given link.
>>
>> It does not matter if the value is same or different ... what matters 
>> is automated and consistent indication which of my applications given 
>> new metric applies to.
>>
>> I already mentioned this to Ron here:
>> https://urldefense.com/v3/__https://mailarchive.ietf.org/arch/msg/lsr
>> / 
>> OgGLI8yezUDWU-EZePoIj6y6ENk/__;!!NEt6yMaO-gk!VVLJCpIMrWixS17PeaBbfOpe
>> b NPO4JUW4jparIn36jHmhv4_-W2_q_Smwo7oIYgk$
>> <https://urldefense.com/v3/__https:/mailarchive.ietf.org/arch/msg/lsr
>> /
>> OgGLI8yezUDWU-EZePoIj6y6ENk/__;!!NEt6yMaO-gk!Tny8sU7cmjqLAbDVnliN7lck
>> 7 J4tCBAHr10i3CW2G9oviUWo8b2RTJxCXc0gvWOz$>
>>
>> Can anyone explain how do I map generic metric to selected network 
>> applications I am to run in the network ?
>>
>> Thx,
>> Robert.
>>
>> On Fri, Jul 30, 2021 at 11:05 AM Van De Velde, Gunter (Nokia -
>> BE/Antwerp) <[e-mail] 
>> <mailto:[e-mail]>> wrote:
>>
>>      A little late in the discussion... (PTO events do happen)
>>
>>      a quick opinion on the below discussion on whether Generic metric
>>      sub-tlv should be encoded on a ASLA or not.
>>      For me, it depends on how the metric for the corresponding
>>      metric-type is obtained and if it can be configured (static).
>>      It doesn’t make sense to have Application specific values if a
>>      particular metric is obtained only dynamically, for eg, dynamically
>>      measured delay is going to be same for all applications.
>>      On the contrary, te-metric can be configured, and we can in
>>      principle configure different values for different applications.
>>
>>      My opinion is that if any of the metric-types in the Generic metric
>>      sub-tlv can be configured, it should be inside the ASLA.
>>
>>      G/
>>
>
>