When equipped with a VLNC2 SYSCTL, a VLNC50/52/55 and/or VLNC64 SONET/SDH Transport circuit pack the Alcatel-Lucent 1850 TSS-5 can operate as an integrated network element within a synchronous SONET/SDH network.
When equipped with a VLNC42/42B, VLNC52/55, and/or VLNC6x circuit pack the Alcatel-Lucent 1850 TSS-5 can operate as an integrated network element within a synchronous Ethernet network.
The information in this section describes synchronization within synchronous SONET/SDH and synchronous Ethernet networks.
For additional information about synchronization, refer to Synchronization features.
With a synchronous network, careful consideration should be given to proper design of the network's synchronization environment. Proper synchronization engineering minimizes timing instabilities, maintains quality transmission network performance, and limits network degradation due to unwanted propagation of synchronization network faults. The synchronization features of the Alcatel-Lucent 1850 TSS-5 are designed to complement the existing and future synchronization network and allow it not only to make use of network timing but also to take on an active role in facilitating network synchronization.
A number of published sources give generic recommendations on setting up a synchronization network. The Alcatel-Lucent 1850 TSS-5 is designed to operate in a network that complies with SONET/SDH recommendations stated in GR-253-CORE and GR-436-CORE.
Synchronous Ethernet network standards are described in ITU-T Recommendation G.8261/Y.1361.
The following are some key recommendations from the documents listed above. For further detailed explanation, the sources should be consulted directly.
A node can only receive the synchronization reference signal from another node that contains a clock of equivalent or better quality (±20 ppm for the VLNC42/42B and VLNC50/52/55 circuit packs, ±4.6 ppm for the VLNC6x circuit packs).
The facilities with the greatest availability (absence of outages) should be selected for synchronization facilities.
Where possible, all primary and secondary synchronization facilities should be diverse, and synchronization facilities with the same cable should be minimized.
The total number of nodes in series from the Stratum 1 source should be minimized. For example, the primary synchronization network would ideally look like a star configuration with the Stratum 1 source at the center. The nodes connected to the star would branch out in decreasing Stratum level from the center.
No timing loops may be formed in any combination of primary and secondary facilities.
Refer to Synchronization features for detailed information about the timing modes.
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