1GE L3 aggregation

Thu Jun 16 21:24:15 UTC 2016

On 16 June 2016 at 22:27, Saku Ytti <saku at ytti.fi> wrote:

> On 16 June 2016 at 22:36, Baldur Norddahl <baldur.norddahl at gmail.com>
> wrote:
>
> Hey,
>
> > If I need to speak BGP with a customer that only has 1G I will simply
> make
> > a MPLS L2VPN to one of my edge routers. We use the ZTE 5952E switch with
> > 48x 1G plus 4x 10G for the L2VPN end point. If that is not enough the ZTE
> > 8900 platform will provide a ton of ports that can do MPLS.
>
> I wonder if you'd do this, if you could do L3 to the edge. And why is
> termination technology dependant on termination rate?
>

The ZTE 5952E (routing switch) can do L3VPN including BGP. But it is
limited to about 30k routes. It is usable if the customer wants a default
route solution, but not if he wants the full default free zone.

The ZTE M6000S-2S4 (carrier grade router) will do all you want, however it
is more expensive. We use the MPLS routing switch because it is a $2k
device compared to the router which is more like $15k.

As a small ISP we have two edge routers (the slightly larger M6000-S3 which
is about $20k). Our customers are spread out throughout the city and we
have 26 PoPs, so it is much more cost effective to have the cheaper device
put the traffic in a tunnel and haul it back to the big iron.

> > The tunnel is automatically redundant and will promote link down events,
> so
> > there is not really any downside to doing it this way on low bandwidth
> > peers.
>
> When you say redundant, do you mean that label can take any path
> between access port and termination IRB/BVI? Or do you actually have
> termination redundancy?
>

Our PoPs are connected in a ring topology (actually multiple rings). If a
link goes down somewhere, or an intermediate device crashes, the L2VPN will
reconfigure and find another path.

> If you don't have termination redundancy, you have two SPOF, access
> port and termination.
>

For a BGP customer I could offer two tunnels, one to each of our provider
edge routers. But very few of our customers are BGP customers, they just
want normal internet. For them we do VRRP between the two provider edge
routers and have the one tunnel go to both.

> If you do have termination redundancy, you're spending control-plane
> resource from two devices, doubling your control-plane scale/cost.
>

The M6000 devices can handle 64k tunnels and are generally way overpowered
for our current business. It is true that I might be limited to 1x 64k
customers instead of 2x 64k customers, but with that many customers I would
need to upgrade anyway.

> I'm not saying it's bad solution, I know lot of people do it. But I
> think people only do it, because L3 at port isn't offered by vendors
> at lower rates.
>

We actually moved away from a hybrid solution with L3 termination at the
customer edge to simply backhauling everything in L2VPNs. We did this
because the L2VPN tunnels are needed anyway for other reasons and it is
easier to have one way to do things.

Regards,

Baldur