When taking advantage of the less expensive Ethernet services, network administrators must consider the service-dependent attributes of the client interfaces. This multiplexed access aspect of the UNI relates to whether a customer-edge node has an individual UNI associated with each of the far-end UNIs to which it's connected, or whether a UNI is shared among the connections to a number of other customers' UNIs.
Ethernet (per IEEE 802.1Q) allows tags to be inserted into Ethernet media-access controller (MAC) frames to create VLANs. When a customer wants to preserve this VLAN segregation of traffic through the WAN, the carrier simply can preserve the entire MAC frame, including the VLAN tag.
The customer and service provider (SP) both may want to use VLAN technology. If so, the SP must do one of two things. Insert a second (?stacked?) VLAN tag into the MAC frame. Or, translate the customer VLAN tag at the ingress to conform to the service provider's VLAN tag assignments, and then restore the customer VLAN value at the egress.
Multiple customer VLAN IDs can be mapped into a single EC at a UNI via the bundling process. The case where all VLAN IDs are mapped to a single EC is called all-to-one bundling. It should be noted that all-to-one bundling and multiplexed access are mutually exclusive. Multiplexed access refers to the multiplexing of multiple ECs into a UNI. Mapping all VLAN IDs into a single EC means that there's a single EC at that UNI rather than multiple ECs.
With Ethernet Services other than EPL, service providers and customers must agree to a bandwidth profile to minimize congestion in the network and avoid the associated packet loss. The bandwidth profile characterizes the traffic that a customer generates to the network at the UNI. It includes parameters such as guaranteed committed information rate (CIR), peak information rate (PIR), burst sizes, and management of excessive traffic.
Converging technology and applications increase the importance and value of wide-area Ethernet data transport services. Service providers should be aware of some of the new technology and standards in development that will enable carriers to provide these services. Implementing Ethernet transport services requires a thorough understanding of Ethernet's connection services, client interfaces, and protection and restoration abilities to maximize the benefits of this new capability.
What makes the development of Ethernet transport service attractive is its evolutionary approach. It builds on the customers' capital investment in Ethernet technology and the transport providers' existing SONET/SDH backbone networks and OAM procedures. All of the pieces are currently in place for offering EPL services. The tools and standards to provide the more complicated ELAN, EVPL, and EVPLAN services are in development now. Ultimately, they will be deployed for more efficient network provisioning and to provide reliability data back to administrators who can use the OAM feedback for traffic management.
While some proprietary data-transport solutions exist, carriers require standards-based solutions (something Ethernet data transport provides) for any significant deployment of new services. Standards guarantee that the solution will be available from multiple vendors, stable, and supported for many years. And ideally, it will be less expensive due to economies of scale. While each carrier probably will want to offer variations on the basic service types to differentiate themselves from their competitors, these services provide the framework from which they can build.