363-206-295
Technical Specifications
Issue 1 December 1997 10-23
The DS1 timing output used for network synchronization (BBF2B only) provides
long-term accuracy traceable to the OC-12 line. SONET synchronization
messaging is used to output DS1 AIS when clock traceability is lost. Jitter on the
DS1 output is less than 0.06 unit interval peak-to-peak.
Synchronous Timing Generator 3 (BBF4)
*
10
The TG3 Stratum 3 circuit pack meets the specifications of GR-253-CORE,
SONET Transport Systems Generic Criteria. The TG3 circuit pack supports three
timing modes:
■ External timing: Locked to external Stratum 3
(±4.6 ppm) or better DS1 reference.
■ Line-timing: Locked to recovered clock from an OC-N signal.
■ Free-running: Timing derived from high-stability temperature-compensated
voltage-controlled crystal oscillator (TCVCXO) with a long-term accuracy of
±4.6 ppm and temperature stability of ±2 ppm.
Holdover mode is entered on failure of external timing or line-timing reference,
providing a temperature stability of ±2 ppm (−40°C to +75°C) or ± .3 ppm
(0°C to +70°C). Holdover capability for 24 hours will be better than ±.37 ppm.
The DS1 timing output used for network synchronization (BBF2B or BBF4)
provides long-term accuracy traceable to the OC-N signal.
Protection Switching 10
Ring Networks 10
Path protection rings feed a SONET payload (STS or virtual tributary [VT]) from
the ring entry point, simultaneously in both rotations of the ring, to the signal's ring
exit point. The node that terminates the signal from the ring monitors both ring
rotations and is responsible for selecting the signal that has the highest quality
based on LOS, path AIS, and path BER performance. On pass-through paths, all
detected hard failures (LOS, LOF, LOP, line AIS, STS path AIS, or STS
unequipped) result in STS AIS insertion in the outgoing signals. This allows the
terminating node to be aware of the failure and to switch to protection. Protection
switching is completed within 50 milliseconds of failure detection.
Under normal conditions, both incoming SONET path signals to the switch
selection point are of high quality, and the signal can be selected from either ring.
A failure or a transmission degradation on one of the rings requires that the other
ring path be selected. Nonrevertive switching minimizes the impact on critical
customer services by giving the service provider control when, and if, the critical
service should revert to a particular ring. A manual path protection switching
command allows switching back to the original path for ease of ring maintenance.
* Available third quarter 1997 for use with Release 7.0 and later.
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