AT&T DEFINITY 7200 series Guia do Utilizador descarregar pdf (Página 231)

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SYNCHRONIZATION OF DIGITAL FACILITIES B-23

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Facility rank ordering is generally based on limited technical and operational information. It is

recommended that facility selections be based on local ﬁeld experience where available.

RULE 4:

Where possible, the routes for all primary and secondary synchronization facilities should be diverse.

EXAMPLE FOR RULE 4

Figure B-15, Optimal Diverse Routing, explains the optimal conﬁguration when rule 4 is used. Figure B-

16, Less Than Optimal Diverse Routing, shows a less than optimal application of rule 4.

SECONDARY (BACKUP) FREQUENCY REFERENCE

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PRIMARY FREQUENCY REFERENCE

DIGITAL TRANSMISSION FACILITY

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Figure B-15. Optimal Diverse Routing

Figure B-16, Less Than Optimal Diverse Routing, shows node C deriving both primary and secondary

timing from node D, via the two separate T1 facilities. If node D should fail, node C would no longer

receive timing that is traceable to node A. Here, node C would lose synchronization and begin to introduce

slips into the network.

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