Method for traffic routing in a communications network

• US 5,699,358 A
• Filed: 09/13/1995
• Issued: 12/16/1997
• Est. Priority Date: 09/13/1994
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Festl, Robert, Nindel, Matthias
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US08/527,709
• Time in Patent Office: 825 Days
• Field of Search: 370/54, 370/16, 370/17, 370/60, 370/60.1, 370/94.1, 370/94.2, 370/94.3, 370/351, 370/217, 370/221, 370/225, 370/222, 370/252, 370/352, 370/422, 370/389, 370/394, 370/406, 455/33.1, 455/33.4, 455/54.1, 455/56.1
• US Class Current: 370/351
• CPC Class Codes: H04Q 3/66 Traffic distributors

Abstract

In order to determine the second path in the case of non-availability of a direct path between neighboring switching nodes, there are held in the individual switching nodes priority lists in which, ordered in terms of the degree of loading, the direct paths to the neighboring nodes and the direct paths from these neighboring nodes to the neighboring nodes thereof are identified by comparing the priority list of the originating node with that of the neighboring destination node, that neighboring node whose direct paths to the originating and destination nodes promise the highest switching probability being selected as an intermediate switching node of a second path.

Claims

1. A method for traffic routing in a communications network having a plurality of switching nodes interconnected such that a connection can be established between two neighboring switching nodes via a plurality of connecting paths so that if a direct path between an originating switching node and a neighboring destination switching node is not available, a second path leading via an intermediate switching node can be determined, comprising the steps of:

providing in the originating switching node data relating to both achievability of direct paths connecting the originating switching node to its neighboring nodes, and achievability of direct paths connecting the neighboring destination switching nodes to their respective neighboring nodes, this being achieved by data periodically updated in the switching nodes and relating to the direct paths connected to these switching nodes being combined in node-specific priority lists which are ordered in terms of degree of achievability, and wherein each switching node sends its own priority list to all of its neighboring nodes so that node-specific priority lists of all the neighboring nodes are available in each switching node;

for identifying a second path which has as high a probability as possible of successful switching, the priority list of the originating node is compared with the priority list of the neighboring destination node, and the neighboring node whose direct paths to the originating and destination nodes promises the highest switching probability is selected as said intermediate switching node for said second path; and

upon successful switching, storing the second path and, as long as the previous priority lists continue to be valid, using the second path directly for a subsequent corresponding call request without a determination procedure.

2. The method according to claim 1 including the steps of recording identifiers of the switching nodes to which a connection exists via the direct paths and a quality factor calculated based on established seizure conditions in the priority lists as data for achievability of the direct paths.

3. The method according to claim 2 including the steps of calculating the quality factor of a direct path as a product of a ratio of a square of an instantaneous number of free connecting channels to a total number of the connecting channels of the direct path, and a ratio, valid in the updating period, of a number of the connections successfully handled via the direct path to a number of call attempts.

4. The method according to claim 3 wherein the switching nodes send to their neighboring nodes only intermediate variables or only original variables for calculating quality factors, and wherein calculation of the corresponding quality factor is performed in a receiving switching node.

5. The method according to claim 1 wherein identifiers of the switching nodes to which a connection exists via the direct paths, and a fictional quality factor corresponding to an arrangement sequence of the identifiers, are recorded in the priority lists as data for the achievability of the direct paths.

6. The method according to claim 2 wherein when comparing the priority lists, one priority list is traversed in an outer loop and another priority list is traversed in an inner loop until a corresponding switching node identifier is found for a first time, and wherein the identifier is stored together with the quality resulting from the quality factors of the links of the corresponding second path, then values are replaced either in each case or only when a minimum value has not been reached for the quality, and when the traversal of the priority lists is conducted further, a further corresponding switching node identifier is found and the corresponding second path has a higher quality than that found so far, and the second path whose values are stored in this way at the end of the traversal of the lists is used as the valid second path for switching.

7. The method according to claim 1 wherein when switching fails via a directly used stored second path, said second path is erased and, depending on which link of the second path is blocked, in a data stock of the originating switching node either in the dedicated priority list or in the priority list relevant to the destination switching node an entry denoting the direct path leading to the intermediate switching node of this second path is set to a last position, a fictional quality factor identifying a lowest possible rank is entered as a quality factor, and the priority list as thus amended is used as a basis for a subsequent determination of the second path.

8. The method according to claim 7 wherein when determining a second path whose link connecting the intermediate switching node to the neighboring destination switching node has a quality below a fixed minimum value, or if the priority list present in the originating switching node of this destination switching node reordering has taken place to a prescribed number, a new priority list is requested by the destination switching node before expiration of a transmission period.