MPLS in the campus Network?

Marian Ďurkovič md at bts.sk
Sat Oct 22 21:59:09 UTC 2016


On Sat, 22 Oct 2016 21:29:22 +0200, Mark Tinka wrote 
> On 21/Oct/16 19:02, Javier Solis wrote:
> > With that said, what are the best options to be able to cost effectively
> > scale without using vlans and maintaining a routed core? What technology 
> > would someone suggest (mpls, vxlan,etc) to be the best possible solution?
  
> IME, MPLS is a good use-case here. If you are going to use the same /24 (or
> whatever prefix applies to you) across multiple locations, you will need some
> kind of overlay. Be it IP-in-IP, GRE, MPLS (l2vpn's or l3vpn's) or plain old >
Ethernet, you will need something.
>
> MPLS makes a lot of sense to me. It's native in hardware, upper-layer
> agnostic, mature, and reasonably affordable even at low scale.

The question here is, whether MPLS is the *optimal* solution for campus needs.

The same functionality could be obviously achived by multiple technologies,
and while MPLS is well supported on high-end SP routers, various limitations
appear when people try to use it on commodity ASICs which typically empower
today's ethernet switches - one of them being e.g. limited ability to
effectively load-balance traffic over multiple parallel links.

Yes, in theory we could build all campus LANs using high-end SP routers, but
when 100GE backbone is desired (which is often the case in EDU/NREN sector), 
the costs of such solution jump to unacceptable heights.

Thus we looked for another technology, which doesn't have the usual L2 problems
and is able to provide services we need (including L2 extensions to remote
campuses) at reasonable costs and with enough simplicity. 

To avoid typical L2 problems, you clearly need a solution based on L3 routing.
And TRILL is exactly that - although it maintains L2 interface to the outside
world, internally it performs dynamic L3 routing by IS-IS protocol with all
safety belts like TTL check, RPF check etc. 

IMHO, TRILL is much better fit for campus needs, since it was specifically
designed for this networking space - and our 6-months production fully confirms
that view (of course, YMMV).


   With kind regards,

       M.



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