Ethernet has been around for a long time and is understood, easy to use, and trusted. It is a low-cost solution that offers scalability, rapid and easy provisioning, granular bandwidth management, and simplified network management due to its single protocol nature. As its popularity has increased and it has edged into the WAN environment, it now supports such applications as large-scale backup, streaming media server access, Web hosting, application service provider (ASP) connectivity, storage area networks (SANs), video, and disaster recovery.

Another important service is the virtual LAN (VLAN). Often characterized as a virtual private network (VPN) made up of a securely interconnected collection of LANs, a number of vendors now offer VLANs as a service, including Lantern Communications, which claims to be able to support thousands of VLANs on a single metro ring. Similarly, transparent LAN (TLAN) services have gained the attention of the industry; they enable multiple metro LANs to be interconnected in a point-to-point fashion.

Many vendors are now talking about Ethernet private lines (EPLs), an emerging replacement for legacy dedicated private lines. Implemented over Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH), the service combines SONET/SDH s reliability, security, and wide presence with Ethernet s rapid, flexible provisioning capability. One company that sees the value in this combination is Appian Communications, already building Systems Network Architecture (SNA), video, SAN, and Voice over IP (VoIP) application support across its network architectures.

Of course, Ethernet presents some disadvantages. These include...