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

[Peter Psenak <[e-mail]>]

Hi Yingzhen,

On 02/10/2020 22:15, Yingzhen Qu 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.

you are right. That is exactly what is being done for flex-algo with 
SRv6 - locator is associated with a single algo only. The proposal uses 
the same concept.

thanks,
Peter

> 
> Thanks,
> Yingzhen
> 
> On 10/2/20, 9:43 AM, "Lsr on behalf of Peter Psenak" <[e-mail] on behalf of ppsenak=[e-mail]> 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
> 
>      >
> 
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