Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms (Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01

[Peter Psenak <[e-mail]>]

Hi Jimmy,

On 10/12/2020 13:02, Dongjie (Jimmy) wrote:
> In Flex-Algo draft, it says:
> 
> "Application-specific Flex-Algorithm participation advertisements MAY be topology specific or MAY be topology independent, depending on the application itself."
> 
> The preassumption of current IP Flex-Algo participation is that one node always participate in a Flex-Algo for both IPv4 and IPv6, and for all the topologies it joins.
> 
> I'm not saying this does not work, just want to understand the reason of this design, and whether some flexibility (e.g. AF specific or topology specific) would be useful in some cases.
> 

this was the choice of authors, because there does not seem to be a 
string reason to do it per topology.


> BTW, a similar case is about SR-MPLS and SRv6 being treated as a single application. Below is the discussion quoted from a previous mail on this list:
> 
>    [Jie] OK. While the meaning of "app" here maybe a little vague, are SR-MPLS and SRv6 considered the same or different apps?
> 
>    [Peter] These are considered as single app, and share the same participation signaling. Please note that SRv6 support is signaled independently of FA participation.
> 
> Does this imply that for Flex-Algo path computation with SRv6, in addition to the Flex-Algo participation information, the SRv6 support information of nodes also needs to be considered, so that nodes participate in this Flex-Algo but do not support SRv6 will be pruned from the topology?

no.

thanks,
Peter


> If so, IMO this needs to be specified in the Flex-Algo draft. If not, please clarify how to prune the nodes which participate in the same Flex-Algo for SR-MPLS only? Thanks.
> 
> Best regards,
> Jie