RSVP-TE Extensions For GMPLS

THE OIF UNI 233 Source UNI-N Source UNI-C Label request Label mapping Label request Label mapping Reservation confirm Reservation confirm Destination UNI-C Destination UNI-N Figure 9.32 Successful connection establishment using LDP. mapping message, which at the other end, it is sent from the source UNI-N to the source UNI-C. The destination UNI-C can indicate in its label mapping message that a reserva- tion confirmation is required. In this case, a reservation confirmation is sent by the source UNI-C to the source UNI-N, and from the destination UNI-N to the destination UNI-C, as shown in Figure 9.32. The reservation confirm message is implemented using the LDP notification message with the status code set to “reserve confirm.” A connection create request usually specifies a bidirectional connection. Reception of the label request message by the destination UNI-C signifies that the resources to establish the connection with the specified attributes are available in the network. It does not, however, imply that the connection is available for data transport. Specifically, the configuration of the intermediate cross-connects might not have occurred yet. This process starts when the destination UNI-C sends a label mapping message in response to the label request message. The connection create message might fail for a number of reasons, such as no band- width available, service level agreement SLA violation, and connection rejected by destination UNI-C. In these cases, the failure is indicated to the source UNI-C using the LDP notification message, with the status code set to the reason for the failure. Connection deletion To inform its peer to stop using a particular label, an LSR in LDP can employ one of two different messages: the label withdraw message or the label release message. LSR A sends a label withdraw message to a peer LSR B to indicate that B should stop using a specific label that A had previously advertised. Alternatively, LSR A sends a label release message to a peer LSR B to indicate that it no longer needs a specific label that B had previously advertised. In the UNI LDP extensions, both the label withdraw and the label release messages are used. The choice of which message to use depends on the entity that initiates the deletion. The label withdraw message is used when connection deletion is in the upstream directions, i.e., from the destination UNI-C towards the source UNI-C. The label release message is used in the downstream direction, i.e., from the source UNI-C to the destination UNI-C. 234 WAVELENGTH ROUTING OPTICAL NETWORKS Failure detection and recovery The LDP keepAlive message is used to detect signaling communication failures between a UNI-C and a UNI-N, unless an alternative mechanism is in place to detect signaling failures more efficiently. During a signaling communication failure, all active connections are maintained whereas all connections which are in the process of being established are cleared.

9.6.3 RSVP Extensions For UNI Signaling

The RSVP protocol definitions apply only to the UNI signaling – that is, between the source UNI-C and UNI-N and the destination UNI-N and UNI-C. The network is assumed to provide coordination of the signaling messages between the source and destination side of the connection. Most of the UNI abstract messages are directly supported by re-using existing procedures, messages, and objects defined in RSVP-TE and GMPLS extensions of RSVP- TE. Table 9.1 gives the mapping between the OIF UNI abstract messages and the RSVP messages. Connection establishment To create a connection, the source UNI-C sends a Path message to its source UNI-N. The Path message includes a GENERALIZED LABEL REQUEST object which indi- cates that a label binding is requested for this connection. The traffic parameters of the connection are encoded in a SONETSDH SENDER TSPEC object in the Path message and a SONETSDH FLOWSPEC object in the corresponding Resv message. Figure 9.33 shows the message flow during a successful connection establishment. It is assumed that the source UNI-N sends a Resv message to the source UNI-C after the segment of the connection within the optical network has been established. To request a bidirectional connection, a UNI-C must insert an UPSTREAM LABEL object in the Path message to select the upstream labels for the connection. Connection deletion A connection in RSVP can be deleted by either using a single PathTear message or an ResvTear and PathTear message combination. Upon receipt of the PathTear message, a Table 9.1 Mapping between abstract messages and RSVP messages. Abstract message RSVP message Connection create request Path Connection create response Path, PathErr Connection create confirmation ResvConf Connection delete request Path or Resv Connection delete response PathErr, PathTear Connection status enquiry implicit Connection status response implicit Notification PathErr, ResvErr