e concerns already mentioned, the model needs more complexity, less isolation, and better security. Work to define an O-NNI is also underway. (See Figure 2-58 for NNI posi- tioning.) Although venture capitalists may be willing to fund this work, his- tory isn't encouraging. Neither Frame Relay intracarrier nor intercarrier Chapter 2 IP/Optical - UNI Interface Figure 2-56 O-UNI/O-NNI in Optical Connection private optical networks. Source: Cisco conn.req conn.req Private conn.setup conn.setup Client Client Client-network signaling and data interface service access boundary between client(s) and OTN handles control and/or data traffic OTN services may be configured to signaled across UNI (analysis to PVC and SVC) IP/Optical - NNI Interface Client I-NNI E-NNI I-NNI I-NNI Private I-NNI I-NNI Client Client E-NNI Node-to-node or network-to-network adjacency, I-NNI w/in a trust domain, E-NNI between trust domains Characterized by equal exchange of topology data between peer entities NNI interfaces ever really developed and took hold. The same is true of ATM intracarrier and intercarrier NNI connections. NNIs are expected to provide connections between different carriers, subnetworks belonging to a single carrier, and the same subnetwork and switches from different vendors. This agenda is ambitious. Although it Optics Primer Figure 2-57 OIF UNI 1.0 service Service provider and user Provider Domain domains. Domain Connection Control Plane Domain (signaling) (signaling) (transport) (transport) Intranet Intranet Optical Transport (West) Network (East) Router Router Location A Location B Figure 2-58 Vendor 1 Vendor 2 NNIs. Mixed Vendor Vendor 4 Carrier A Vendor 3 Metro Metro Vendor 1 Vendor 2 Vendor 2 Vendor 2 Vendor 2 Vendor 1 Vendor 3 Metro Metro Metro Vendor Carrier B Vendor 3 Vendor 2 Vendor 4 Vendor 5 Metro Metro Metro Metro Carrier C would seem similar to the Exterior Gateway Protocol (EGP), Border Gate- way Protocol (BGP), OSPF, and MPLS, in reality those protocols generally run on the same hardware/software implementa