[j-nsp] Best practice for igp/bgp metrics

[Saku Ytti]

I disagree. Either traffic fits or it does not fit on SPT path,
bandwidth is irrelevant.

For LAG you should set minimum links to a number which allows you to
carry traffic you need.

Ideally you have capacity redundancy on SPT level, if best path goes
down, you know redundant path, and you know it can carry 100% of
demand. If this is something you cannot commercially promise, you need
strategic TE to move traffic on next-best-path when SPT is full.


On 25 October 2017 at 23:25, Pavel Lunin <plunin at gmail.com> wrote:
> Reference bandwidth might however be useful for lags, when you may want to
> lower the cost of a link if some members go down (though I prefer ECMP in
> the core for most cases).
>
> And you can combine the role/latency approach with automatic reference
> bandwidth-based cost, if you configure 'bandwidth' parameter on the
> interfaces instead of IGP cost.
>
> 25 окт. 2017 г. 10:08 ПП пользователь "Saku Ytti" <saku at ytti.fi> написал:
>
>> Hey,
>>
>> This only matters if you are letting system assign metric
>> automatically based on bandwidth. Whole notion of preferring
>> interfaces with most bandwidth is fundamentally broken. If you are
>> using this design, you might as well assign same number to every
>> interface and use strict hop count.
>>
>> On 25 October 2017 at 22:41, Luis Balbinot <luis at luisbalbinot.com> wrote:
>> > Never underestimate your reference-bandwidth!
>> >
>> > We recently set all our routers to 1000g (1 Tbps) and it was not a
>> > trivial task. And now I feel like I'm going to regret that in a couple
>> > years. Even if you work with smaller circuits, having larger numbers
>> > will give you more range to play around.
>> >
>> > Luis
>> >
>> > On Tue, Oct 24, 2017 at 8:50 AM, Alexander Dube <nsp at layerwerks.net>
>> > wrote:
>> >> Hello,
>> >>
>> >> we're redesigning our backbone with multiple datacenters and pops
>> >> currently and looking for a best practice or a recommendation for
>> >> configuring the metrics.
>> >> What we have for now is a full meshed backbone with underlaying isis.
>> >> IBGP exports routes without any metric. LSP are in loose mode and are using
>> >> isis metric for path calculation.
>> >>
>> >> Do you have a recommendation for metrics/te ( isis and bgp ) to have
>> >> some values like path lengh ( kilometers ), bandwidth, maybe latency, etc
>> >> inside of path calculation?
>> >>
>> >> Kind regards
>> >> Alex
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>>
>>
>> --
>>   ++ytti
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  ++ytti