Re: [Lsr] Seeking feedback to the revised draft-dunbar-lsr-5g-edge-compute

Robert

Here are a few examples of UCMP drafts below used in core and data center
use cases.

https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-unequal-lb-15

https://datatracker.ietf.org/doc/html/draft-mohanty-bess-weighted-hrw-02

https://datatracker.ietf.org/doc/html/draft-ietf-idr-link-bandwidth

https://datatracker.ietf.org/doc/html/draft-mohanty-bess-ebgp-dmz

There are many use cases in routing for unequal cost load balancing
capabilities.

Kind Regards

Gyan

On Wed, Jan 12, 2022 at 2:23 PM Robert Raszuk <robert@raszuk.net> wrote:

> Linda,
>
> > IGP has been used for the Multi-path computation for a long time
>
> IGP can and does ECMP well. Moreover, injecting metric of anycast server
> destination plays no role in it as all paths would inherit that external to
> the IGP cost.
>
> Unequal cost load balancing or intelligent traffic spread has always been
> done at the application layer *for example MPLS*
>
> Thx a lot,
> R.
>
> On Wed, Jan 12, 2022 at 8:18 PM Linda Dunbar <linda.dunbar@futurewei.com>
> wrote:
>
>> Robert,
>>
>>
>>
>> Please see inline in green:
>>
>>
>>
>> *From:* Robert Raszuk <robert@raszuk.net>
>> *Sent:* Wednesday, January 12, 2022 1:00 PM
>> *To:* Linda Dunbar <linda.dunbar@futurewei.com>
>> *Cc:* Les Ginsberg (ginsberg) <ginsberg@cisco.com>; lsr@ietf.org
>> *Subject:* Re: [Lsr] Seeking feedback to the revised
>> draft-dunbar-lsr-5g-edge-compute
>>
>>
>>
>> Hi Linda,
>>
>>
>>
>> *[LES:] It is my opinion that what you propose will not achieve your
>> goals – in part because IGPs only influence forwarding on a per packet
>> basis – not a per flow/connection basis.*
>>
>> *[Linda] Most vendors do support flow based ECMP, with Shortest Path
>> computed by attributes advertised by IGP.*
>>
>>
>>
>> I am with Les here. ECMP has nothing to do with his point.
>>
>>
>>
>> [Linda] Les said that “IGP only influence forwarding on a per packet
>> basis”.  I am saying that vendors supporting “forwarding per flow” with
>> equal cost computed by IGP implies  that forwarding on modern routers are
>> no longer purely per packet basis.
>>
>>
>>
>>
>>
>> Draft says:
>>
>>
>>
>> *When those multiple server instances share one IP address (ANYCAST), the
>> transient network and load conditions can be incorporated in selecting an
>> optimal path among server instances for UEs.*
>>
>>
>>
>> So if we apply any new metric to indicate load of a single anycast
>> address how is this going to help anything ?
>>
>>
>>
>> [Linda] The “Load” or “Aggregated Site Cost” is to differentiate multiple
>> paths with the same routing distance.
>>
>>
>>
>>
>>
>> You would need a mechanism where the network is smart and say per src-dst
>> tuple or more spreads the traffic. IGP does not play that game today I am
>> afraid.
>>
>> [Linda] There is one SRC and multiple paths to one DST. IGP has been used
>> for the Multi-path computation for a long time.
>>
>>
>>
>> Thank you, Linda
>>
>>
>>
>> Thx a lot,
>> R.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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