Restrictions on Ethernet L2 circuits?

Thu Dec 31 20:06:36 UTC 2009

> -----Original Message-----
> From: Simon Leinen 
> Sent: Thursday, December 31, 2009 8:29 AM
> Subject: Re: Restrictions on Ethernet L2 circuits?

> > Should business customers expect to be able to connect several LANs
> > through an Ethernet L2 ciruit and build a layer 2 network spanning
> > several locations?
> 
> At least for our customers, that is indeed important.  The most
popular
> application here is for a customer to connect a remote location to
> their
> campus network, and that want to (at least be able to) use any of
their
> existing VLANs at the remote site.

That is what I currently expect from a layer 2 solution. One that does
not allow VLAN tagging across the span is of much less utility.  

> > Or should the service provider implement port security and limit the
> > number of MAC addresses on the access ports, forcing the customer to
> > connect a router in both ends and segment their network?
> 
> That would make the service less attractive, and also more complex to
> set up and maintain.  For point-to-point service, there is really no
> reason for the network to care about customers' MAC addresses, VLAN
> tags
> and such.  As you said, EoMPLS doesn't care.  (Ethernet over L2TPv3
> shouldn't care either.  If I had cost-effective edge routers that did
> L2TPv3 encapsulation/decapsulation at line rate, I'd switch off MPLS
in
> our core tomorrow.)

I don't want my provider enforcing such things on me provided it doesn't
blow up their network.  If I break my stuff, I expect to own all the
pieces.  I don't want them to nanny me and enforce policy that they
determine is "for my own good" but are of no consequence in maintaining
their own network.  I want the pipe to be basically a long ethernet
cable.  My traffic should be sufficiently isolated as not to cause a
problem in their network no matter what I do.  

> > Also, do you see a demand for multi-point layer 2 networks
(requiring
> > VPLS), or are point-to-point layer 2 circuits sufficient to meet
> > market demand?
> 
> That's a big question for us right now... we're not sure yet.  I'd
like
> to
> hear others' opinions on this.

I once had such a solution in a network and it worked quite well.  It
was the (now defunct) Yipes! NAN (National Area Network) product.  We
used it for OSPF area 0 between all of our US facilities (several
offices and two production colos).  It worked quite well for the amount
of traffic that went between facilities and it was stable for the
approx. two years we had it deployed.  In that case we had only a single
VLAN that acted as a flat layer2 network that spanned the country with a
pair of layer 2/3 switches at each office acting as routers for each
facility area.  This solution turned out to be cheaper and more
efficient than running dedicated links to each facility and getting
everything meshed over point-to-point circuts.  If someone else already
has a nationwide mesh, it probably makes good sense to lease some of
that capacity than to try and build your own.