5. Delivered error(ed) frames 6. Delivered duplicated frames 7. Delivered out-of-sequence frames 8. Lost frames 9. Misdelivered frames 10. Switched virtual call establishment delay 11. Switched virtual call clearing delay 12. Switched virtual call establishment failure 13. Premature disconnect 14. Switched virtual call clearing failure 12.5.7.1 Network Responsibilities. Frame relay frames are routed through the net- work on the basis of an attached label (i.e., the DLCI value of the frame). This label is a logical identifier with local significance. In the virtual call case, the value of the logical identifier and other associated parameters such as layer 1 channel delay, and SO on, may be requested and negotiated during call setup. Depending on the value of the parameters, the network may accept or reject the call. In the case of the permanent virtual circuit, the logical identifier and other associated parameters are defined by means of administrative procedures (e.g., at the time of subscription). The -network interface structure allows for the establishment of multiple virtual calls or permanent virtual circuits, or both, to many destinations over a single access channel. Specifically, for each connection, the bearer service: REVIEW EXERCISES 1. Provides bidirectional transfer of frames. 2. Preserves their order as given at one user-network interface if and when they are delivered at the other end. (Note: No sequence numbers are kept by the network. Networks are implemented in such a way that frame order is preserved). 3. Detects transmission, format, and operational errors such as frames with an unknown label. 4. Transports the user data contents of a frame transparently; only the frame's address and FCS fields may be modified by network nodes. 5. Does not acknowledge frames. At the user-network interface, the FRAD (frame relay access device), as a minimum, has the following responsibilities: 1. Frame delimiting, alignment, and transparency provided by the use of HDLC flags and zero bit insertion. 2. Virtual