Control, Transmission, and Synchronization Interfaces
5-30 Issue 8.0 July 2002
Synchronous Applications (With a Mixture of Asynchronous
and Synchronous Low-Speed Interfaces) 5
■ One node provisioned externally timed; all other nodes provisioned
through timed, line timed, or externally timed: This configuration
(Figure 5-18, Figure 5-19, Figure 5-20, and Figure 5-21) are used with
asynchronous (DS3) or synchronous (EC-1, OC-3 and/or OC-12) low
speed interfaces, or a mix of synchronous and asynchronous low speed
interfaces. These configurations also prevent the need of having to
reprovision a node when synchronous low speed interfaces are added.
The timing signals used to synchronize the externally timed nodes (phase
locked in releases prior to Release 5) should be traceable to a high quality
source(s). If synchronous low speed interfaces are present, the timing
signals must be traceable to a stratum 1 source. If only asynchronous low
speed interfaces are present, the timing signals must be traceable to a
stratum 3 or better source. The quality and source of the timing signals
must be engineered appropriately. The guidelines for choosing the timing
source(s) and the BITS clock configurations are beyond the scope of this
document.
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