Hi Lorenzo,
On Tue, Aug 11, 2015 at 11:16 PM, Lorenzo Colitti <lore...@google.com>
wrote:
> On Wed, Aug 12, 2015 at 11:54 AM, Alia Atlas <akat...@gmail.com> wrote:
>
>> ECMP is critical in the datacenter and backbone because those networks
>>> are designed to provide the E ("equal") in ECMP. Because the links are
>>> equal, it's easy to load-balance over them without needing to do
>>> complicated stuff like traffic engineering - you just treat an N-way ECMP
>>> bundle as a link N times bigger, and hash across it. That does not happen
>>> in home networks, which are more grown than designed.
>>>
>>
>> ECMP applies beyond link bundles. Of course, equal-cost can be hard to
>> do - and one can safely use downstream paths. The relevant question is
>> whether traffic is expected to be able to take multiple paths to allow
>> load-balancing.
>>
>
> Yes, ECMP applies beyond bundles, but unless your metrics are very
> simplistic, you won't actually encounter equal-cost paths unless you design
> the network with ECMP in mind. So you'd need non-equal cost multipath for
> multipath to be useful in a homenet.
>
Yes - downstream paths, as I already said. That is going to next-hops that
are closer to the destination than the computing router. As long as your
next-hop's distance to the destination is strictly decreasing, it is safe
to use.
There are two questions. First, is the desirable to load-balance among
different paths useful/necessary/unnecessary in homenet? Second, is that
accomplished with metric assignment that encourages equal-cost, are
downstream paths used, and/or is there a way of doing explicit paths?
Regards,
Alia
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