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Method for synchronizing interconnected digital equipment
| Details |
Inventors: Near, Christopher D.; Uyar, M. Umit;
Assignee: AT&T Bell Laboratories (Murray Hill, NJ)
Primary Examiner: Safourek; Benedict V.
Assistant Examiner: Bocure; Tesfaldet
Attorney, Agent or Firm: Ranieri; Gregory C.
Optimized synchronization planning and clock distribution for a network of interconnected digital equipment is achieved by designating a network node at the highest stratum level as the master clock node, forming a group of all unassigned nodes connected to the assigned node or nodes, selecting subgroup of all nodes from the group wherein the subgroup includes all nodes having the highest stratum level of the group, limiting the subgroup to the nodes which have a desired characteristic when such nodes are included in the subgroup, determining the synchronization performance of each node in the subgroup according to a predetermined criterion, assigning one node from the subgroup as a clock timing receiver wherein the one node exhibits the best performance for nodes in the subgroup, and iterating the method at the forming step. In order to obtain an optimum synchronization plan, it is desirable to repeat the entire method described above for the complete set of nodes which are capable of being designated as a master clock node. When more than one node is capable of being considered as a master clock node, the synchronization planning method is then completed by computing the network synchronization performance for each synchronization plan related to a different designated master clock node and choosing the synchronization plan which offers the best network synchronization performance as computed above. |
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DETAILED DESCRIPTION Digital networks are represented as a combination of digital equipment shown as nodes in FIG.
1 interconnected by links shown as lines in FIG.
1.
Sychronization performance of a digital network depends on both link and equipment performance.
Links are required to transmit timing (clock) information accurately throughout the digital network.
Digital equipment is required to receive the timing (clock) information accurately.
In order to ensure that all digital equipment in the network are properly synchronized, preparation of a synchronization plan is almost a necessity.
A synchronization plan describes the flow of timing (clock) information throughout a digital network from one or more master timing sources (master clock nodes) to the remaining equipment in the network.
As the size of a digital network grows, preparation of a synchronization plan becomes increasingly more difficult because all possible master timing sources and all possible information paths emanating from the master timing sources within the network must be considered.
Suboptimal synchronization plans, that is, plans for which synchronization performance is less than optimal such as those developed by prior art adhoc planning methods, are insufficient to ensure maintenance of network synchronization in accordance with the appropriate standard.
In digital telecommunication networks, optimum synchronization plans, such as those realized in accordance with the principles of the present invention, can permit the digital network to achieve synchronization performances which exceed the strict timing requirements required by the standards.
In a network of synchronous digital equipment, the purpose of an optimum synchronization plan is to transmit timing information from a master timing source to all equipment in the network in the best possible way.
For such a plan, it is necessary to choose one or more master timing sources as a common time base of the network.
When properly planned, the network will exhibit a minimum daily time error for all equipment
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I/O Systems 
