1GE L3 aggregation

Mon Jun 20 06:59:22 UTC 2016

On 18/Jun/16 21:55, Baldur Norddahl wrote:

> Just want to point out that there is no eBGP multi-hop involved. These are
> L2 tunnels so the devices appear to be directly connected on the layer 3
> level.

Agree, but there is still a disconnect between what the network knows is
the actual physical path vs. what the actual physical path is.

This might not be a big of an issue for most, or in cases where the
l2vpn does not have to travel very far or via several links. But for us,
it adds some complexity we'd rather do without.

>
> The advantage of using L2VPN is that you can connect the customer to
> whatever can handle the requirements. You are not limited to what your
> access edge devices can do. 99% of our customers are not BGP customers, so
> it would be silly to spend cash on equipment that will support full table
> BGP at each PoP.

In the Access, 99% of our customers are Internet Access, i.e., not IP
Transit, so don't need BGP. We have come across Internet Access
customers that need to do BGP for redundancy, which turns into a private
ASN job with them announcing our own routes back to us. But that tends
to be the exception, about 0.2% of our deliveries.

That notwithstanding, touching only one box to deliver an Internet
Access service is a major win for us vs. touching more than one. And we
are only burning one port in lieu of more than one. And there is only
one place for us to look when troubleshooting issues instead of more
than one. It's simple and brain-dead, which is what we like.

>
> The major downside is a) hops are invisible to traceroute, b) some traffic
> might travel longer than necessary.

For us, both of these are major drawbacks, and a huge advantage we gain
by taking IP/MPLS into the Access.

>
> We are a residential ISP and we find that traffic between customers is
> minimal. We choose to accept that traffic between two neighbors might be
> backhauled to a central location and back instead of staying local.

Which I accept in Broadband/BNG scenarios. But outside of that, well,
you know my views by now :-)...

Mark.