> On Jun 11, 2020, at 2:02 PM, Mark Tinka <[email protected]> wrote:
>
>
>
> On 11/Jun/20 17:32, David Sinn wrote:
>
>> Respectfully, that is deployment dependent. In a traditional SP topology
>> that focuses on large do everything boxes, where the topology is fairly
>> point-to-point and you only have a small handful of nodes at a PoP, labels
>> can be fast, cheap and easy. Given the lack of ECMP/WECMP, they remain
>> fairly efficient within the hardware.
>>
>> However if you move away from large multi-chip systems, which hide internal
>> links which can only be debugged and monitored if you know the the obscure,
>> often different ways in which they are partially exposed to the operator,
>> and to a system of fixed form-factor, single chip systems, labels fall apart
>> at scale with high ECMP.
>
> I'm curious about this statement - have you hit practical ECMP issues
> with label switching at scale?
Yes. Path enumeration when you use mult-tier Clos topologies within a PoP
causes you many, many problem.
> We have ECMP'ed label switch paths with multiple paths for a single FEC
> all over the place, and those work fine both on Cisco and Junos (of all
> sizes), both for IPv4 and IPv6 FEC's. Have done for years.
The protocols will work fine. And if you are still buying SP class chips,
you're fine. But you are paying a lot for those chips in cost and power. If you
look to move to the class of single-chip systems, which gives you lower costs
and higher radix, you have to pay the trade-offs somewhere. MPLS at high-radix
ECMP exposes this.
David
> Unless I misunderstand your concern.
>
> Mark.
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