Centralized restoration of a network using preferred routing...

Details Centralized restoration of a network using preferred routing... Centralized restoration of a network using preferred routing...

1996-12-31

2001-12-04

Trammell, James P. (Department: 2161)

Error detection/correction and fault detection/recovery

Data processing system error or fault handling

Reliability and availability

C709S238000

Reexamination Certificate

active

06327669

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to telecommunications systems and more particularly to centralized restoration of a network using preferred routing tables to dynamically build an available preferred restoral route.
BACKGROUND OF THE INVENTION
Telecommunications networks, such as telephone networks, are subject to failure. Given the volume of traffic and the criticality of some of the traffic on such telecommunications networks, it is desirable to be able to restore from failure as quickly as possible. In general, restoration involves the following steps: (1) detecting the failure; (2) isolating the location of the failure in the network; (3) determining a restoral route for network traffic; and (4) implementing the restoral route.
It is generally desirable to restore a failed network within a few seconds or less. Networks are typically restored by first restoring higher priority network elements and then restoring lower priority elements. Many conventional systems develop a “pre-plan” for restoring networks. These “pre-plans” are developed by simulating possible network failures and determining restoral routes to restore from the simulated failures. The development of these “pre-plans” entails collection of large amounts of data that reflect the logical topologies of the networks. Oftentimes, the data is collected from network engineering databases, which reflect the logical construction of the network by indicating connections and paths of network traffic trunks. A network analyst analyzes the collected data, compares the collected data to the physical topologies and then generates the “pre-plans.” Since these “pre-plans” are developed prior to network failure, one of the “pre-plans” is ensured to be available for restoring traffic when a failure occurs. In general, these “pre-plans” are developed for a given segment of a network that can incur a failure. When the segment fails, the corresponding “pre-plan” is utilized.
Unfortunately, such static “pre-plans” have drawbacks. The topology and configuration of a network are frequently subject to change. The “pre-plans” do not account for such changes; rather, the “pre-plans” are developed for a given snapshot (i.e., a fixed topology and configuration) for the network. In addition, events may occur that make parts of the network unavailable so that the “pre-plans” fail because the “pre-plans” presume that the unavailable portions of the network are available.
Another class of restoration approaches dynamically determines restoral routes at the time of failure. Such “dynamic restoration methods” do not suffer the problems of inflexibility that are encountered with the static restoration methods described above. The dynamic restoration methods formulate a restoral route dynamically during the restoration process to use the most accurate and recent data regarding the network that is available. The drawback of such dynamic restoration approaches is that they require extensive and time-consuming analysis during the restoration process. As a result, the restoration process takes longer than with static restoration methods.
SUMMARY OF THE INVENTION
The present invention addresses the limitations of the conventional methods by providing a solution that incorporates features from both static restoration methods and dynamic restoration methods and adds new features. The present invention, like static restoration methods, creates and stores data regarding restoral routes prior to network failure so that substantial time and computational overhead need not be exhausted at the time of failure. On the other hand the present invention includes a mechanism for determining the availability of portions of the restoral routes at the time of network failure to determine whether the portions can be utilized in the implemented restoral route or not. This provides an added degree of flexibility to the system that accounts for changes in network topology and configuration.
In accordance with a first aspect of the present invention, a method of constructing a segment of a preferred restoral path for restoring a network from a failure is performed by a computer system. The network includes the computer system as well as additional interconnected nodes. Prior to the failure of the network, a preferred routing table is provided for a current node. The preferred routing table specifies choices for a next segment of one or more restoral paths to a target node. At the time of failure of the network, the preferred routing table is accessed to examine the choices for the next segment of the preferred restoral path, and one of the choices is selected.
In accordance with another aspect of the present invention, a method is practiced in a telecommunications network that has nodes, links for carrying network traffic between the nodes, and ports on the nodes for interfacing with the links. The telecommunications network also includes a central restoration system for restoring the network from failures. In accordance with this method, a location of a network failure is identified and at least one pair of end nodes that are affected by the network failure are identified. Preferred routing tables are provided for at least each of the nodes in the identified pair of end nodes. Each preferred routing table specifies a list of one or more ports that interface with links to a restoral path that leads to a target node. The list specifies priority of the ports. The preferred routing tables are used to determine a preferred restoral path for at least one of the identified end node pairs on a port by port basis. One of the preferred restoral paths is selected as the restoral path that is implemented by communicating with the nodes and the selected preferred restoral path.
In accordance with an additional aspect of the present invention, prior to a failure in a telecommunications network, a list of ports for connected nodes in the network is provided. Each list includes an indication of relative optimality of the ports and each port interfaces with a link that leads to another of the nodes that is part of a restoral path to a target node. A preferred restoral path is iteratively built on a link by link basis upon failure of the network. The preferred restoral path is built using the list of ports to identify optimal links in the preferred restoral path.
In accordance with yet another aspect of the present invention, a centralized restoration system is part of a telecommunications system that has nodes that are interconnected to facilitate communication among the nodes. The centralized restoration system restores the network after a failure. The centralized restoration system includes a static component and a dynamic component. The static component provides preferred routing tables that each identify portions of at least one preferred restoral route for restoring a connection between two of the nodes. The dynamic component dynamically determines a restoral route and a time of failure in the network by using the preferred routing tables based on availability of portions of the preferred restoral routes identified in the tables.


REFERENCES:
patent: 4577066 (1986-03-01), Bimonte et al.
patent: 4920529 (1990-04-01), Sasaki et al.
patent: 5187740 (1993-02-01), Swaim et al.
patent: 5335268 (1994-08-01), Kelly, Jr. et al.
patent: 5459716 (1995-10-01), Fahim et al.
patent: 5463615 (1995-10-01), Steinhorn
patent: 5513345 (1996-04-01), Sato et al.
patent: 5623481 (1997-04-01), Russ et al.
patent: 5636203 (1997-06-01), Shah
patent: 5646936 (1997-07-01), Shah et al.
patent: 5657320 (1997-08-01), Russ et al.
patent: 6075766 (2000-06-01), Croslin
patent: 6163525 (2000-12-01), Bentall
patent: 0 494 513 A2 (1991-12-01), None
patent: WO 95/10149 (1995-04-01), None
Herzberg et al. “The Hop-Limit Approach for Spare-Capacity Assignment in Survivable Networks” IEEE Dec. 3, 1995.
Dighe et al. “A Link Based Alternative Routing Scheme for Network Restoration under Failure” IEEE May 1995.
Grover et al. “Near Optimal Spare Capacity Planning in a Mesh Restorable Network” IEEE Jan

Affiliated with

Also associated with

Rating

Centralized restoration of a network using preferred routing... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Centralized restoration of a network using preferred routing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Centralized restoration of a network using preferred routing... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2563439