363-206-295
Transmission and Synchronization Interfaces
5-4 Issue 1 December 1997
Dual Ring Interworking (DRI) 5
The DDM-2000 OC-12 Multiplexer STS-1/STS-3c DRI application uses the same
shelf configuration as the DDM-2000 OC-12 Multiplexer path switched ring
(Figure 5-1). In this configuration, the DDM-2000 OC-12 Multiplexer can provide
STS-1 DRI with another DDM-2000 OC-12 ring, a DDM-2000 OC-3 ring, or an
FT-2000 OC-48 Lightwave System ring with redundant signal appearances at the
two central offices via EC-1/OC-3/OC-3c/IS-3/IS-3c and DS3 interfaces (see
Figure 9-8 in Section 9 "Maintenance Description"). STS-1 paths are provisioned
for drop and continue at the interconnecting nodes, and path selection is at the
STS-1 level. When used with the DDM-2000 OC-3 Multiplexer, the DDM-2000
OC-12 Multiplexer STS-1/VT1.5 (0x1) DRI application can be created with the
drop and continue feature implemented in the DDM-2000 OC- 3 Multiplexer shelf.
The DDM-2000 path switched ring architecture allows mixing of drop and continue
circuits with standard path switched circuits.
OC-3/OC-12 Ring (0x1) Low-Speed Interfaces 5
The DDM-2000 OC-12 ring supports (0x1) OC-3/IS-3 interfaces in its function unit
slots. These interfaces must be provisioned as 0x1 and are supported in single
homing and dual homing configurations (see Figure 5-2 and Figure 5-3
respectively). For single homing, signals pass through the DDM-2000 OC-12
transport ring and exit to the DDM-2000 OC-3 ring. OC-12 function unit slot FN(x)-
1 is connected to OC-3 main-1 and OC-12 FN slot FN(x)-2 is connected to OC-3
main-2. Switching is not done on the DDM- 2000 OC-12 Multiplexer on these
lines, or paths on these lines; rather VT1.5 or STS-1 level path switching is done
on the DDM-2000 OC-3 Multiplexer. This allows DDM-2000 OC-3 nodes running
ring software to interface with DDM-2000 nodes of an OC-12 ring in such a way as
to provide ring-on-ring architecture. Each OC-3 ring so supported occupies up to
three STS-1 time slots on the OC-12 ring. Each OC-12 node can provision the
same STS-1 time slots as other OC-12 nodes to drop to the OC-3 shelf (to share
STS-1s among several OC-3 shelves), or the OC-12 node can provision different
STS-1s at different sites. The OC-12 ring passes the contents of these STS-1
time slots between the low-speed OC-3/IS-3 lines and OC-12 high-speed lines
without terminating them or performing any path protection switching on them. Up
to four OC-3 rings can be supported in this fashion by an OC-12 ring to maximize
the OC-12 bandwidth utilization. This allows access to any and all VT1.5 signals
at an OC-12 site.
The OC-3/IS-3 lines between an OC-12 node and an OC-3 node connected in a
ring (0x1) fashion behave like the OC-3 lines between the nodes on an OC-3 ring
and do not perform line level protection switching. Instead, the OC-3 shelves
perform the normal path protection switching functions.
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