Devil's Advocate - Segment Routing, Why?

Mark Tinka mark.tinka at seacom.mu
Sun Jun 21 15:55:03 UTC 2020


On 21/Jun/20 14:58, Baldur Norddahl wrote:

>
> Not really the same. Lets say the best path is through transit 1 but
> the customer thinks transit 1 sucks balls and wants his egress traffic
> to go through your transit 2. Only the VRF approach lets every BGP
> customer, even single homed ones, make his own choices about upstream
> traffic.
>
> You would be more like a transit broker than a traditional ISP with a
> routing mix. Your service is to buy one place, but get the exact same
> product as you would have if you bought from top X transits in your
> area. Delivered as X distinct BGP sessions to give you total freedom
> to send traffic via any of the transit providers.

We received such requests years ago, and calculated the cost of
complexity vs. BGP communities. In the end, if the customer wants to use
a particular upstream on our side, we'd rather setup an EoMPLS circuit
between them and they can have their own contract.

Practically, 90% of our traffic is peering. We don't that much with
upstreams providers.


>
> This is also the reason you do not actually need any routes in the FIB
> for each of those transit VRFs. Just a default route because all
> traffic will unconditionally go to said transit provider. The customer
> routes would still be there of course.

Glad it works for you. We just found it too complex, not just for the
problems it would solve, but also for the parity issues between VRF's
and the global table.

Mark.
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