363-206-295
Administration and Provisioning
Issue 1
December 1997
8-31
Example Cross-Connections
8
The OC-12 (STS level) cross-connections are:
■
At CO: mb-1:a-3
mb-1 is dropped to the third STS in the OC-3 between CO and CO-1.
■
At RT1: mb-1:a-1
mb-1 is dropped to the first STS in the OC-3 between RT1 and RT1-1.
■
At RT2: mb-1:c-2
mb-1 is dropped to the second STS in the OC-3 between RT2 and RT2-2.
■
At RT3: mb-1:b-3
mb-1 is dropped to the third STS in the OC-3 between RT3 and RT3-3.
■
At RT4: mb-1:mb-1
mb-1 is passed through RT4 at the STS level.
These cross-connections can be thought of as establishing one STS of an OC-3
ring embedded in the OC-12 system. This is sometimes referred to as a "ring on
ring." In the example, the OC-3 nodes are CO-1, RT1-1, RT2-2, and RT3-3. The
STS itself traverses all nine nodes. An "ordinary" STS (for example, one that
carries a DS3 from an originating node to a terminating node) can drop at only two
locations (terminate in two-way at the source and destination), and pass-through
cross-connections are needed at the intermediate nodes. There can be multiple
drop (ring 0x1) type cross-connections to optical extensions.
The VT cross-connections that follow drop or pass through individual VTs in the
STSs. This is like an ordinary OC-3 ring, except that, the same OC-12 STS can be
dropped to different STSs in the various OC-3s. In an ordinary ring, the same time
slot (for example m-1-1-1) is used all the way around the ring. In a ring-on-ring
application, the time slot identification can change in each extension. The same
VTG/VT will be used but the STS can change.
