Recommended L2 switches for a new IXP

Marian Ďurkovič md at
Mon Jan 19 10:12:28 UTC 2015

On Sat, Jan 17, 2015 at 09:15:04PM +0200, Saku Ytti wrote:
> On (2015-01-17 12:02 +0100), Marian Ďurkovič wrote:
> > Our experience after 100 days of production is only the best -  TRILL setup
> > is pretty straightforward and thanks to IS-IS it provides shortest-path 
> > IP-like "routing" for L2 ethernet packets over any reasonable topology 
> > out of the box (without the burden and cost implications of VPLS).
> I'm not sure what the burden refers to, but cost implications to me seem same,
> trident HW can do VPLS.

Well, it can, but as usual the devil is in the detail.

For example, loadbalancing on outgoing LAGs depends on *inbound* packet 
encapsulation as follows:

- native ethernet, TRILL, L3 MPLS : hash based on L3 and L4 headers
- L2 MPLS, MACinMAC : hash based on L2 headers only.

Thus if you use VPLS or SPB-M on Trident HW, the egress PE doesn't support
per-flow loadbalancing on IXP participants' LAGs.

In any case, we preferred TRILL over SPB-M not just because of that, but 
mainly due to a fact that TRILL provides real routing using IS-IS as we 
know it from IP world, while SPB still builds on top of MST and just cleverly
uses multiple trees. Yes, compatibility with existing ASICs was one of the 
main design goals of SPB, but that's irrelevant once you have Trident HW. 



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