omers. This means that an installer can make one visit to an enterprise to install gear, and then power up the service remotely through software. Previously, multiple onsite trips were required for setup. Mesh Configuration Backups Mesh backup technology is enabled by signals generated from Control Plane Technol- ogy equipment. The service utilizes a logical rather than a physical design. The physi- cal topology is not designed as an actual mesh, wherein each point on a network is connected to every other node. Rather, as demonstrated in Figure 4-3, traffic is backed up in a logical manner with more than one choice of alternate routes. In this way, each carrier and each route do not require duplicated fiber, multiplexing gear, and transmis- sion equipment. Convergence in Core and Metropolitan Networks Control Plane-Enabled Programmable Mesh Network Traditional rings Primary path Protection path Ring topolgy One primary path One pre-provisioned* protection Wasted capacity Limited protection against multiple failures Multilayer Control Plane-Enabled Optical Resilient Mesh Egress Alternate Ingress Routes with outages Resilient mesh Automated provisioning* Dynamic path choices for multiple failures High network availability Bandwidth optimization *Provisioning refers to the planning, design, and installation of network equipment and routes. Figure 4-3 Comparing ring topology with mesh topology for network failures. (Courtesy Ciena Corporation) Carrier Networks Control Plane Technology mesh configurations for network backups are less costly and often provide more diverse routing options than ring topology, because carriers are able to share resources instead of duplicating fiber routes and equipment. They are also more flexible because mesh backups can be configured with multiple backup routes rather than a single backup path. With mesh backup technology, if a cable is cut or equipment connected to fiber is out of service, traffic is automatically sent to other routes within a single carrier's network or to an entirel