Easier to troubleshoot is the main reason but also, you would not put the MME/S-GW in every segment with the eNodeB anyways, so in the end you'd really want a L3 routed solution between them. One of the things I've seen is the L3 interface for the eNodeB terminates locally on an attached smaller cell-site router via a /30 and is not part of a larger L2 service with many eNodeBs in the same broadcast domain. You can run into scale issues with L3 as well with a router at every cell site and dynamic routing, so usually it's some kind of hybrid solution. Most service providers who provide backhaul services for wireless providers do so over a L2 or PW over MPLS network. Some of the smaller ALU, etc. cell site routers have started to support L3VPN so maybe L3VPN will be a service offering in the future with all-IP EPCs. Phil On 1/30/11 12:02 PM, "Glen Kent" <glen.kent@gmail.com> wrote:
Hi,
I would like to understand why there is a preference for L3 VPNs over L2 VPNs for the EPC backhaul networks? We can use both layer 2 and layer 3 VPNs for communication between the eNodeB and the MME or S-GW, so why is it that most providers prefer L3 over L2.
Glen