[j-nsp] Application of L2 VPN in Real World Scenario

[Simon Chen]

Thanks a lot, guys. I definitely learned a lot from all of you :-)

-Simon

On Wed, Jul 16, 2008 at 10:16 AM,  <sthaug at nethelp.no> wrote:
>> I have to jump in, since I am also interested :-)
>>
>> My question is, what do you think the cost/benefit of L2VPN over VPLS?
>> It seems that L2VPN is restricted to point-to-point and there is a
>> separate vrf (and a routing table) for each link, while VPLS maintains
>> a single vrf and routing table. Have you guys thought about using
>> VPLS? Or is there any problems with it? Maybe scalability?
>
> Can't really comment the (Juniper proprietary) L2VPN. However, we use
> both Martini tunnels (L2circuit in Juniper terminology) and VPLS. The
> two technologies are quite different:
>
> - L2circuit (and L2VPN) give you a point-to-point link. You can think
> about the technology as a pipe where packets are inserted at one end
> and come out at the other end. No MAC address learning is necessary.
> Troubleshooting is fairly simple (no need to go looking for specific MAC
> addresses and where they originate). Scaling is fairly good - we have
> M7i routers with more than 2000 L2circuits.  You need to watch your FEB
> memory utilization, though.
>
> - VPLS give you a layer 2 multipoint network - in effect you are making
> your network look like a large LAN. MAC address learning is necessary,
> and only the MX boxes are able to do this in hardware. Replication of
> broadcast/multicast/unknown unicast traffic is at the *source*, which
> has the potential to melt down your network (e.g. one 100 Mbps stream
> replicated to 20 different PE routers gives you 2 Gbps of traffic from
> your ingress router towards your network core). Both the technology
> and the troubleshooting is significantly more complex than L2circuit/
> L2VPN.
>
> I don't want to give the impression that VPLS is all gloom and doom.
> Juniper has done a reasonable job of making the technology stable,
> especially in later JunOS versions, and P2MP LSPs help significantly
> with the ingress replication problem. However, L2 point-to-point is
> still a significantly simpler technology no matter how you look at it.
>
> Steinar Haug, Nethelp consulting, sthaug at nethelp.no
>