Configuration Management:

A configuration management function has three parts: managing the equipment in the network, managing the connections in the network, and managing the adaptation of client signals into the optical layer.

1. Equipment Management:

i. In general, the principles of managing optical networking equipment are no different from those of managing other high-speed networking equipment.

ii. We must be able to keep track of the actual equipment in the system (for example, number and location of optical line amplifiers) as well as the equipment in each network element and its capabilities.

iii. For example, in a terminal of a point-to-point WDM system, we may want to keep track of the maximum number of wavelengths and the number of wavelengths currently equipped, whether or not there are optical pre- and power amplifiers, and so forth.

iv. Among the considerations in designing network equipment is that we should be able to add to existing equipment in a modular fashion.

v. For instance, we should be able to add additional wavelengths (up to a designed maximum number) without disrupting the operation of the existing wavelengths.

vi. Also, ideally the failure of one channel should not affect other channels, and the failed channel should be capable of being serviced without affecting the other channels.

vii. Using arrayed components can reduce the cost and footprint of the equipment. However, if one clement in the array fails, the entire array will have to be replaced.

viii. This reduces the system availability, as replacing the array will involve disrupting the operation of multiple channels, and not just a single channel. Using arrays also increases the replacement cost of the module.

ix. Therefore, there is always a trade-off between obtaining reduced cost and footprint on one front against system availability and replacement cost on the other front.

2. Connection Management:

i. In optical networks provides light paths, circuit switched connection to its user.

ii. Connection management deals with setting up connections, keeping track of them, and taking them down when they are not needed anymore.

iii. The process usually involves configuring. Equipment from a variety of vendors each with its own management system, and usually one network element at a time.

iv. Service providers in many cases deploy equipment only when needed.

v. The net result of this process is that it can take months for a service provider to turn up a new connection in response to a user request.

vi. Supporting all this requires carriers to predeploy equipment and bandwidth ahead of rime in the network and having methods in place to be able to turn O. the service rapidly when needed.

vii. Distributed Control: Distributed control protocols have been used IP/MPLS and Ethernet networks. Theses protocol can be used to control and manage optical networks.

viii. GMPLS protocol support optical connections. The Automatic Switched Transport Network (ASTN) is an architecture for managing connections including optical connections.

Distributed connection control has several components:

• Topology Management.

i. Each node in the network maintains a database of the network topology and the current set of resources available, as well as the resources used to support traffic.

ii. In the event of any changes in the network, the updated topology information needs to be propagated to all the network nodes.

iii. Nodes periodically, or in the event of changes, flood the updated information to all the network nodes. We can use an Internet routing and topology management protocol such as OSPF or IS-IS, with suitable modifications to represent optical layer topology information, and update it automatically.

• Link management.

i. The performance of the link can be monitored by keeping statistics on packet losses and bit error rate. If the performance grades below an acceptable threshold, a failure indication signal can be sent to the other end of the link.

ii. A failure indication signal can also he sent when the performance is degrading to indicate imminent failure. Then an early warning can allow a switch to an alternate link before the link fails.

iii. Networks may also allow link bundling, where multiple parallel channels between two nodes Operate as a single logical link.

iv. This will reduce the amount of overhead in the routing protocol and keep track of the network topology.

• Route computation.

i. When a connection is requested from the network, the network needs to find a route and obtain resources along the route to support this connection. This can be done by applying a routing algorithm on the topology database of the network.

ii. The routing algorithm should take into account the various constraints imposed by the network, such as wavelength conversion ability and the available on each link of the network.

• Signaling protocol.

i. Once routes are computed, the connection need to be set up.

ii. This process involves reserving the resources required for the connection and setting the actual switches inside the network to set up the connection.

iii. The process requires nodes to exchange messages with other nodes.

• Signaling Network.

i. Nodes need a signaling channel to exchange control information with other nodes.

3. Adaptation Management:

• Adaptation management is the function of taking the client signals and covering them to a form that can be used inside the optical layer. This function includes the following:

i. Covering the signal to the appropriate wavelength, optical power level, and other optical parameters associated with the optical layer. The WDM is received and converted into standardized signal, such as a short-reach SONET signal.

ii. Adding and removing appropriate overheads to enable signal to be managed inside the optical layer.

iii. Policing the client signal to make sure that the client signal stays within boundaries that have been agreed upon as part of the service agreement.

iv. The WDM network must support different types of interfaces to accommodate a variety of different users requiring different functions. Figure 1 shows the different possible adaptation interfaces.

• Compliant wavelength interface: One interface might be to allow the client to send in light at a wavelength that is supported in the network. These wavelengths may be regarded as compliant wavelengths. In this case, the interface might be a purely optical interface, with no optoelectronic conversions required

• Noncompliant wavelength interface: This is the most common interface and has variety of different types of attached client equipment that use optical transmitter and/or receiver not compatible with the signals used inside the WDM network.

• Substrate multiplexing: Additional adaptation functions include time division multiplexing of lower-speed streams into a higher-speed stream within the WDM equipment prior to transmission.