Telecom Source Code & Engineering Services

Sync Status Message (SSM) Source Code for WAN Developers

Background

In an environment of a hierarchical network, clock traceability is fairly straightforward, and at least logically manageable with respect to quality and source. In the flat landscape of SONET/SDH networks, this could be much more difficult. And, not only are these newer networks flat, they also will tend to be owned by many different providers.

To address this potential weakness, NComm’s SSM TMS provides a new mechanism to both make it clear of the quality and traceability of the clock source, and to permit the network to intelligently choose the best clock from those available should an issue arise. This new mechanism is the Sync Status Message (SSM) and the rules of use associated with them. The SSM TMS will accomodate T1, E! and E3 provided that the hardware supports the function.

NComm’s SSM TMS will:

Perform the SSM processing according to GR-253, GR-1244, ETSI 300-417-6-1 and G.781. It has the following high level objectives:

• To maintain traceability to a identifiable primary clock reference source.
• To ensure that higher stratum clocks are never slaved to lower stratum clocks.
• To ensure that all Network Elements have both a primary source and a secondary source in case of a primary failure.
• To ensure that timing loops are avoided.

The SSM Module has the following features:

• Determination of the proper source from which to generate timing by processing the TBs (see below for definition)
• Interface to a Timing Device Driver (i.e. DS3100 chip's timing functions).
• The processing of timing input from external Line cards (e.g. S1 byte-sonet/sdh, SSM/TM-e3, BOC-T1, Sa bits-E1) [TERMINOLOGY NOTE: This is called Timing Bits (TB) from now on]
• Provision for Redundant timing card control and switch over between them for support of equipment redundancy requirements.
• Provision of transmit relay of timing control information (i.e. updates Tbs) for the system in the transmit direction
• Algorithms for controlling timing per GR-253 for SONET/T1.
• Algorithms for controlling timing per ETSI 300-417-6-1 and G.781
• Algorithms will default to standard plus be selectable and configurable by the user
• A well defined API consistent with current NComm TMS products

The SSM Module is complete and is designed to come up completely functional with no additional work required to achieve full standard compliant operation.

Device Driver Module

One Device Driver Module (DDM) is included with the base software. The DDM performs the mapping between the NComm trunk management software and the actual hardware.