Multiplex communications – Pathfinding or routing – Through a circuit switch
Reexamination Certificate
1998-08-10
2002-05-14
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Through a circuit switch
C370S458000, C370S459000, C370S222000
Reexamination Certificate
active
06389015
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to communication network management, and more particularly to a method of and a system for reconfiguring a SONET ring to maintain optimally balanced demand loading.
DESCRIPTION OF THE PRIOR ART
Traditionally, network design, network provisioning and management, and network migration are treated as separate tasks that are often done by different organizations within a carrier. The mandate of the network design task is to optimize the routing and resource allocation in order to obtain a minimum cost network. Network design tends to take a long term view by considering the forecast of traffic at the end of a target. The resulting network design has a potential danger of being far from reality or impossible to implement.
The network migration planning task is based upon available yearly or quarterly capital budget and decisions tend to focus only on a short-term effects to the network, without considering the overall consequences and the life cycle of the network.
The network provisioning and management task concentrates on meeting day-to-day circuit provisioning requirements and it tends to use simple rules. More often than not, the decision how circuits are provisioned is based on individual discretion. The effect of a decision to provision circuits and the overall consequences to network utilization are normally not considered or understood in day-to-day operations.
Consequently, there is a gap between an optimized network design and the actual implementation of the network. This gap results largely because optimized network designs are based on global knowledge of traffic demands and specific ways of routing and bundling those demands for minimizing the total cost of the network. In the actual realization of the network, the demands may turn out to be very different from the original forecasts, and the lack of automation and selecting routes for provisioning circuit demands results in inefficient utilization of network capacities. Thus, given the same traffic volume, the actual realized cost of the network is usually significantly higher than the original estimate.
As the network evolves, new capacities and new fiber routes are added to the network. At the same time, new requirements on the transmission network come from traffic volume growth and new types of services that have different bandwidths. Quality of service and routing constraints also change the network dynamics.
Typically, because of difficulties in reconfiguring the network, trunk groups that were misrouted due to lack of capacity at the time of provisioning are not re-routed even when new capacities become available at a later time. Over the course of network evolution, the result is often a disorderly set of traffic routes. Comparing the actual traffic routing pattern against the optimal routing, it is usually found that by reconfiguring the network routing, then plenty of capacity can be squeezed out of the network. By reconfiguring the network, overall utilization will be increased and there may not be a need for adding new capacities to the network. Accordingly, the life cycle cost of the network can be reduced greatly.
Under a mesh architecture, several ways of reconfiguring a network have been proposed. These include AT&T's “Fully Shared Network” concept and TRLab's “Self-Engineered Network” concept. However, when reconfiguring the whole network, the requirement on synchronization and switching time is quite high and current digital cross connect (DXC) and switch technology essentially do not have the capability to support a real time network wide configuration. The estimated risk and cost of reconfiguration of a transmission network under the mesh architecture is prohibitively high for any carrier to consider this option seriously. Another concern that prohibits reconfiguration in a mesh architecture is that when factoring restoration into the overall configuration scheme, complexities make network reconfiguring virtually impossible. Therefore, though transmission network reconfigurations have been proposed by various research organizations in the past, no one has actually implemented a proposed system.
Recently, there has been a move away from mesh topology for telecommunications networks toward a ring topology. In a bidirectional line switched ring, the demands on the ring are allowed to be routed on either side of the ring, and capacity for all spans of the ring is required to be the same. A ring topology offers advantages over a mesh topology, primarily in that a ring is self-healing and therefore may be restored in a matter of milliseconds after a failure. However, rings are still subject to becoming poorly routed over the course of ring evolution. As ring demands are provisioned and de-provisioned, certain spans of the ring become congested while other spans become under utilized. It is therefore an object of the present invention to provide a management system that reconfigures a ring in real time.
SUMMARY OF THE INVENTION
The present invention provides a method of and system for managing a SONET ring. The method of the present invention computes an optimally balanced demand loading for the SONET ring and generates an updated time slot assignment map for each node of the SONET ring based upon the optimally balanced demand loading. The method causes each node of the SONET ring to switch substantially simultaneously to its updated time slot assignment map, thereby reconfiguring the SONET ring.
The method computes an optimally balanced demand loading for the SONET ring by computing a demand loading for the SONET ring such that each link of said SONET ring carries substantially the same demand as every other link of said SONET ring. The method causes each node of the SONET ring to switch substantially simultaneously to its updated time slot assignment map by downloading to each node of said SONET ring its updated time slot assignment map along with a designated time to make the substitution. The method freezes provisioning activity on the SONET ring while reconfiguring the SONET ring.
The present invention also provides a method of reconfiguring inter-ring routing by moving circuits from one inter-ring path to another. The method sets up digital cross connect connection for the new path and then downloads to each ring of the network new time slot assignment maps based upon the new path. The method then causes the rings of the new path to switch to the new time slot assignment maps.
REFERENCES:
patent: 6118792 (2000-09-01), Beshai
patent: 6192049 (2001-02-01), Sohraby
Huang Jennifer
Khalil Anis
Nathan Sridhar
Chin Wellington
MCI Communications Corporation
Pham Brenda H.
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