Carrier Ethernet Services and Layer 3 VPNs

Many core networks are built over IP/MPLS both nationally and internationally.

IP/MPLS or L3VPN is a technology where the traffic is carried over pseudowires (PW) over MPLS Label Switch Paths (LSPs) tunnels. The forwarding is L3-based. The infrastructure comprises routers that are MPLS-capable. Such a network can provide connectivity service to subscribers, in a similar manner to the way CEN provides Ethernet services.

These L3 services are non-standard, and there is currently no standards development organization that is attempting to create standards for such services. In contrast to L3VPN, Ethernet services are built on the concept of Ethernet based forwarding, hence can be referred to as L2VPN. When we consider L3VPN Vs. L2VPN the following comparison can be made.

FeatureCarrier EthernetL3VPN
Customer HandoffEthernet UNIEthernet port (or PDH circuit)
Service IdentificationVLAN ID / EVCIP Address
Service RateGranular, up to 10GbpsGranular, up to 10Gbps
Service Level SpecificationDefined the service performance
objectives, controlled by Bandwidth
Class of Service IdentificationPCP, DSCP, Per EVCDSCP/ToS
Packet ForwardingBy MAC Address and/or VLAN IDIP Address
Fault ManagementLink Trace, Continuity Check
Traceroute, ICMP Ping
Performance ManagementFrame Delay, Frame Delay Variation,
Frame Loss Ratio, Service Availability 
Packet Delay, Packet Delay Variation
Packet Loss 


In some cases a global solution may result in a combination of L2VPN and L3VPN services. The main reason is that for long haul, forwarding based on Ethernet addresses sometimes does not scale sufficiently, whereas L3VPNs are available throughout the globe on international links.



Related and Further Reading