CR-LDP Extensions for GMPLS

THE OIF UNI 231 Source UNI-C Source UNI-N Destination UNI-C Destination UNI-N Connection create response Connection create request Connection create request Connection create response Connection create confirm Connection create confirm Figure 9.31 Successful connection establishment. • Service-related attributes : These are: the encoding type; SONETSDH traffic parame- ters; directionality; a generalized payload identifier; and the service level. The encoding type indicates whether the format is SONET or SDH. The SONETSDH traffic param- eters provide information regarding the signal type and the way in which the data has been concatenated. The directionality attribute indicates whether the connection is unidirectional or bidirectional. The generalized payload identifier indicates the payload carried within the established connection. Finally, the service level attribute indicates a class of service. A carrier can specify a range of different classes of service, such as gold, bronze, and silver. Since the optical network is a circuit-switching network, these classes of service are not related to the familiar QoS parameters in packet-switching networks, such as packet loss and end-to-end delay. Rather, they refer to issues such as the required restoration scheme i.e., no restoration, 1 + 1 protection, etc. and the connection setup and hold priorities. • Routing-related attributes : The only attribute defined is diversity. This attribute can be used when a new connection is being created, to indicate the diversity of the new connection with a list of n existing connections that start at the same UNI-C. The attribute contains n items of the form diversity type, local connection ID, where the local connection ID indicates one of the n existing connections that start at the same UNI-C. The following diversity types are possible: ◦ Node diverse: The new connection shall not use any network nodes that are in the path of the connection denoted by the local connection ID. ◦ Link diverse: The new connection shall not use any network links that are in the path of the connection denoted by the local connection ID. ◦ Shared risk link group SRLG diverse: The new connection shall not use any network links that have the same SRLG as those in the path of the connection denoted by the local connection ID. ◦ Shared path: The new connection shall use the same network links as those used by the connection denoted by the local connection ID. • Policy-related attributes : The only attribute defined is the contract ID, which is assigned by the service provider and configured in the clients. 232 WAVELENGTH ROUTING OPTICAL NETWORKS • Miscellaneous-related attributes : These are the connection status and error codes. The connection status indicates whether the connection is: active, does not exist, unavailable, or pending. The error code is used to describe errors resulting from connection actions, such as: unauthorized sender, unauthorized receiver, service level not available, and diversity not available. As an example, the following mandatory M and optional O attributes are used for the connection create request: • Source TNA M • Source logical port identifier M • Source generalized label O • Destination TNA address M • Destination logical port identifier O • Destination generalized label O • Local connection ID M • Contract IDO • Encoding type M • SONETSDH traffic parameters M • Directionality O • Generalized payload identifier O • Service level O • Diversity O The UNI signaling has been implemented by extending the label distribution protocols LDP and RSVP. Below, we describe the LDP and RSVP extensions.

9.6.2 LDP Extensions for UNI Signaling

Two guiding principles were used when extending LDP; limit the introduction of new LDP messages, and LDP extensions should be easily implemented as simple additions to the existing LDP implementation without violating the LDP semantics. As a result, only two new messages a status enquiry message and a status response message were introduced. The general TLV encodings for LDP and CR-LDP are also used in OIF UNI signaling. Additionally, new TLVs were introduced to carry the attributes defined in the UNI. LDP session initialization A single LDP session is established between the UNI-C and the UNI-N, regardless of the number of data links between the client and the TNE. The LDP hello and extended hello are used for neighbor discovery. Connection establishment The connection create request is implemented using the label request message see Section 7.1.4. This message is sent from the source UNI-C to the source UNI-N. At the other end, the label request message is sent from the destination UNI-N to the des- tination UNI-C. The destination UNI-C responds to the destination UNI-N with a label 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.