 the initial setup time, and no additional information is exchanged between GLSR until the GLSP is torn down. No refresh message is needed due to the use of TCP. When a GLSP is no longer needed, decision that can be taken by the client that has deliv- ered the request to the control plane or by the central management system, messages must be exchanged notifying all routers that the GLSP is down and the corresponding allocated resources are now free. 8.3.2.6.2 Surviving Capability in Front of Control Plane Communication Failures RSVP-TE is based on datagram transmission of service packets using UDP; thus it is intrin- sically robust versus failures in the communication capacity available for the control plane. On the other hand, CR-LDP is in principle more vulnerable versus such failure. However, this vulnerability is not always a real weakness of the protocol, since survivability strate- gies are generally adopted in the control plane communication network. 8.3.2.7 Line Management Protocol The last key protocol of the GMPLS suite is the line management protocol; it is a point- to-point protocol that has the role of managing the link between adjacent nodes. As a matter of fact, traditional IP and MPLS protocol suite leverages on the physical layer to Telecommunication Networks manage physical links. On the contrary, GMPLS cannot do that, since it is in charge of the entire network layering, thus a new protocol has been invented for this role. In par- ticular, referring to an optical link, for generality with several WDM channels, LMP is aimed at the following tasks: Control-channel management Link connectivity verification Link property correlation Fault management 8.3.2.7.1 Control Channel Management In order to set up a channel, the control plane must know the IP address on the far end the channel either due to a manual configuration or for automatic discovery. This role, which is a typical point-to-point function relative to a specific link, is performed by the LMP via Config/ Config, Ack messages exchange. Thi