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LSP enc. type Switching type G-PID
Figure 9.27 The RSVP-TE generalized label request object.
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Figure 9.28 The RSVP-TE generalized label object.
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Figure 9.29 The RSVP-TE label set object.
THE OIF UNI
9.6 THE OIF UNI
The OIF UNI specifies signaling procedures for clients to automatically create a connection, delete a connection, and query the status of a connection over a wavelength routing network. The UNI signaling has been implemented by extending the label distribution protocols LDP and RSVP (see Chapter 7). It also uses extensions of the Link Management Protocol (LMP). The client is a packet-switching equipment, such as an IP router and an ATM switch, or a SONET/SDH cross connect which is connected to the optical network. The client side of the OIF UNI is known as the UNI-C and the optical network side is known as the UNI-N.
A SONET/SDH link is used for the transmission of data between a client and its ingress optical node, known as the Terminal Network Element (TNE). The transmission rate of the SONET/SDH link can be up to STS-768/STM-256.
The UNI signaling messages between the UNI-C and the UNI-N are transported in IP packets, over the IP Control Channel (IPCC). This channel can be in-fiber or out-offiber. The in-fiber IPCC is carried over a channel that is imbedded in the SONET/SDH link used for the transmission of data. This channel is the line and section overhead D bytes (see Section 2.3.2). The out-of-fiber channel is separate from the SONET/SDH data link, and can be an Ethernet link between the UNI-C and UNI-N or an IP network (see Figure 9.30).
As mentioned above in Section 9.4, the UNI isolates the clients from the optical network. In view of this, the topology, resources, and addressing of the optical network is not revealed to the clients. The optical network can use internal addresses for internal routing, provisioning, and network management. These addresses are not revealed to the network clients, and are not within the scope of the OIF standardization process. In addition, the clients can use their own addresses. In view of this two sets of addresses, a Transport Network Administrative (TNA) address is used by the UNI to identify the address of a client. The TNA address is a globally uniquely defined address; it is distinct from the native address space of both the clients and the network. To maintain compatibility with network devices that use different addressing types, the TNA can be in the form of IPv4, IPv6, and NSAP (see Section 5.5). The UNI allows a connection between two different TNA type addresses.
The primary services offered to a client by the UNI is the ability to create and delete connections over the optical network on demand. In addition, neighbor and service discovery can be offered optionally. The neighbor discovery procedures allow a TNE and a directly attached client device to determine and identify each other, thus by-passing the necessary manual configuration of the corresponding UNI-C and UNI-N. Service discovery is a process by which a client device obtains information about available services from the optical network.
Figure 9.30 The out-of-fiber IPCC.
WAVELENGTH ROUTING OPTICAL NETWORKS
9.6.1 The UNI Abstract Messages
OIF has defined a number of abstract messages to be used over the UNI. The actual implementation of these messages depends on whether LDP or RSVP is used. These messages are used to create a connection, delete a connection, and query the status of a connection established over the UNI. Recall that a connection is a lightpath or a subrate channel of a lightpath. From the UNI point of view, a connection is a fixed-size bandwidth circuit between an ingress and an egress optical node with a specified frame. At this moment, only SONET/SDH framing is used. A connection can be unidirectional or bidirectional.
The following abstract messages have been defined:
• Connection create request: Sent by the source UNI-C to its ingress UNI-N to request the establishment of a connection. It is also sent from the destination egress UNI-N to the destination UNI-C to indicate an incoming connection request.
• Connection create response: Used to inform the source UNI-C (i.e. that initiated the connection request) of the establishment of the connection. It is sent from the destination UNI-C to the destination UNI-N, and from the source UNI-N to the source UNI-C, which can then start transmitting data upon receipt of this message.