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

[Peter Psenak <[e-mail]>]

Gyan,

On 03/10/2020 02:14, Gyan Mishra wrote:
> 
> Hi  Jeff
> 
>  From a domain perspective where you have a group of nodes and 
> associated IP addressed and SID are part of a discrete underlay instance 
> flex algo topology.  On those same set of nodes you could have another 
> topology and associated address and SIDs for a different flex algo.  

above is right.

> How 
> this would work is that the topologies would have to be segregated from 
> each other as different MT instances or routing process instances.  Is 
> that correct?

no MT at all. You can think of each flex-algo as a set of constraints 
that is used to calculate the path over the common topology. You can 
have many such felx-algos running on a common topology.


> 
> Can two nodes that run two different flex algo become ospf or isis 
> neighbors?

absolutely.

Peter

> 
> Kind Regards
> 
> Gyan
> 
> On Fri, Oct 2, 2020 at 6:25 PM Jeff Tantsura <[e-mail] 
> <mailto:[e-mail]>> wrote:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>     Hi Yingzhen,
> 
> 
> 
> 
> 
>     Yes, that’s the case.  The most important property of an algo
>     computed path is that is has to be consecutive, as either SID or IP
>     address associated with a particular topology is only known within
>     that topology.
> 
> 
>     Looking specifically at Ron’s draft (MPLS could be more complex due
>     to potential hierarchy) - the prefix itself defines the
>     context(topology) and must be globally unique, since IPv4 header
>     can’t have any additional meta-data attached.
> 
> 
> 
> 
> 
> 
> 
>     Cheers,
> 
>     Jeff
> 
> 
> 
> 
> 
> 
>     On Oct 2, 2020, 1:15 PM -0700, Yingzhen Qu
>     <[e-mail] <mailto:[e-mail]>>, 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.
>>
>>
>>
>>
>>
>>     Thanks,
>>
>>
>>     Yingzhen
>>
>>
>>
>>
>>
>>     On 10/2/20, 9:43 AM, "Lsr on behalf of Peter Psenak"
>>     <[e-mail] <mailto:[e-mail]> on behalf of
>>     ppsenak=[e-mail]
>>     <mailto:[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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>>
>>
>>     [e-mail] <mailto:[e-mail]>
>>
>>
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>>
>>
>>
> 
> 
> 
> 
> 
> 
> 
> 
> -- 
> 
> <http://www.verizon.com/>
> 
> *Gyan Mishra*
> 
> /Network Solutions A//rchitect /
> 
> /M 301 502-1347
> 13101 Columbia Pike
> /Silver Spring, MD
> 
>