Network Synchronization
Page 166 7210 SAS M, X Basic System Configuration Guide
Clock Source Quality Level Definitions
The following clock source quality levels have been identified for the purpose of tracking network
timing flow. These levels make up all of the defined network deployment options given in
Recommendation G.803 and G.781. The Option I network is a network developed on the original
European SDH model; whereas, the Option II network is a network developed on the North
American SONET model. See Table 19 and Table 20 for descriptions of the synchronization
message coding and source priorities.
In addition to the QL values received over SSM of an interface, the standards also define
additional codes for internal use. These include the following:
• QL INVx is generated internally by the system if and when an unallocated SSM value is
received, where x represents the binary value of this SSM. Within the 7210 SAS, all these
independent values are assigned as the singled value of QL-INVALID.
• QL FAILED is generated internally by the system if and when the terminated network
synchronization distribution trail is in the signal fail state.
Within the 7210 SAS platform, there is also an internal quality level of QL-UNKNOWN. This is
used to differentiate from a received QL-STU code but is equivalent for the purposes of QL
selection.
Table 19: Synchronization Message Coding and Source Priorities (Value Received on a Port)
SSM value received on port
SDH interface
SyncE interafce in SDH mode
SONET Interface
SyncE interface in SONET mode
Internal Relative
Quality Level
0010 (prc) 0001 (prs) 1. Best quality
0000 (stu) 2.
0111 (st2) 3.
0100 (ssua) 0100 (tnc) 4.
1101 (st3e) 5.
1000 (ssub) 6.
1010 (st3/eec2) 7.
1011 (sec/eec1) 8. Lowest quality qualified in
QL-enabled mode
1100 (smc) 9.
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