Carrier Ethernet E-Line services can be delivered over Wave Division Multiplexed (WDM) networks using Ethernet over WDM technology. Both these physical layer transport technologies carry packetized digital traffic (i.e., Ethernet frames) over photonic channels. DWDM and CWDM technologies can be used to provide very high bandwidth connections in the order of hundreds of Gbps over distances ranging up to 80km (50 miles) without repeaters. However, when WDM is used to deliver Carrier Ethernet services, it supports point-to-point topologies only.
Incoming traffic is mapped by a multiplexer to a specific optical channel. Mapping is agnostic to the content and header of the Ethernet frame and therefore provides a very transparent point-to-point service.
This is illustrated in figure 1 at right.
WDM multiplexers cannot decipher the CoS Identifier and VLAN tag information contained within an Ethernet frame, so all Ethernet frames associated with a particular service are transported by the same photonic channel. Only physical layer failures can be detected and acted upon with this technology, and recovery is performed without intervention from the Ethernet MAC layer.
