Understanding Ethernet-over-MPLS (L2 Circuit)
Ethernet-over-MPLS allows sending Layer 2 (L2) Ethernet frames transparently over MPLS. Ethernet-over-MPLS uses a tunneling mechanism for Ethernet traffic through an MPLS-enabled Layer 3 core. It encapsulates Ethernet protocol data units (PDUs) inside MPLS packets and forwards the packets, using label stacking, across the MPLS network This technology has applications in service provider, enterprise and data center environments. For disaster recovery purposes, data centers are hosted in multiple sites that are geographically distant and interconnected using a WAN network.
A Layer 2 circuit is similar to a circuit cross-connect (CCC), except that multiple Layer 2 circuits can be transported over a single label-switched path (LSP) tunnel between two provider edge (PE) routers. In contrast, each CCC requires a dedicated LSP.
Ethernet-over-MPLS in Data Centers
For disaster recovery purposes, data centers are hosted in multiple sites that are geographically distant and interconnected using a WAN network. These data centers require L2 connectivity between them for the following reasons:
To replicate the storage over Fiber Channel IP (FCIP). FCIP works only on the same broadcast domain.
To run a dynamic routing protocol between the sites.
To support High Availability clusters that interconnect the nodes hosted in the various data centers.