Nortel Networks NTRN10AN, 3500 manual User-specified quality levels for timing sources

2-158Operation, administration, and maintenance (OAM) features

User-specified quality levels for timing sources

A user can specify or override the quality level of an incoming timing source. The user can specify the quality level if the timing source comes from equipment that does not support SSM, such as a BITS or equipment from another vendor. If a user specifies the quality level of a timing source, the user interface appends “-P” to the quality level, for example, ST2-P. Avoid overriding the quality level of an incoming tributary timing source if SSM is supported, to avoid timing loops.

BITS output with VTX-series or STX-192 circuit packs

STX and VTX-series circuit packs provide 1+1 non-revertive timing reference switching for BITS Out. When the BITS Out primary and the secondary references fail, an alarm indication signal (AIS) is sent by the network element as BITS Out. The AIS advises equipment using the BITS Out of the failure so they do not use the BITS Out for synchronization.

When DS1 ESF is provisioned, SSM is supported on BITS Out. The BITS Out SSM is based on the status message from the active timing reference. BITS Out always selects the best quality timing reference based on the SSM of the incoming timing source.

User-initiated synchronization switches

Synchronization switching can take place under the control of the user. With this capability, the user can select the optical interface to which a line-timed network element synchronizes. The line-timed network element accepts the user selected switch as long as the timing reference quality of both optical interface is the same and not equal to DUS, RES, SMC, or ST4.

Synchronization switching in a UPSR, BLSR and 1+1 is non-revertive.

OPTera Metro 3500 supports the following synchronization modes:

•two SF/ESF formatted BITS inputs and outputs

•line timing over DS1, OC-n, and EC-1 facilities

•internal Stratum 3 timing

•synchronization status messaging for BITS input and output, and for SONET facilities (OC-n)

•DS1 ESF BITS synchronization status messaging

Note 1: The DS1 service module (DSM) and the OC-3 interface connected to a DSM cannot be used as a synchronization source.

Note 2: Line timing with the EC-1x12 circuit pack is not supported.

OPTera Metro 3500 Multiservice Platform NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004