363-206-285
Transmission and Synchronization Interfaces
Issue 3 June 2001
5-7
For the DS1 add/drop and ring (Figure 5-4) application, the time slot interchange
(TSI) feature of the 22-type OLIUs provides full flexibility in selecting traffic for
each DS1, DS3, or EC-1 low-speed port from any high-speed time slot. The TSI
function supports cross-connections across the full bandwidth of each OC-3
interface as well as to any low-speed port.
Figure 5-4 is a block diagram of the DDM-2000 OC-3 Multiplexer VT1.5/STS-1
path switched ring application. The DDM-2000 OC-3 Multiplexer interfaces to the
ring through the main slots at the OC-3 rate and uses the programmable VT1.5/
STS-1 TSI capability. Path switching can be done on VT1.5 paths, STS-1 paths,
or a mixture of these. Up to 84 DS1s, 3 DS3s, 3 EC-1s, 1 OC-3/IS-3 1+1 linear
optical extensions, or equivalent combination can be added/dropped from the
DDM-2000 OC-3 Multiplexer self-healing ring at any node. Because of the ring's
path protection scheme, time slots must be reserved all the way around the ring
for all ring traffic, limiting the capacity of the ring to the OC-3 line rate. Like the
add/drop topology, the TSI feature offers full flexibility in assigning signals
between low-speed DS1, DS3, EC-1 or OC-3 ports and the high-speed interface
at each shelf.
The DDM-2000 OC-3 Multiplexer dual ring interworking (DRI) application uses the
same shelf configuration as the OC-3 path switched ring (Figure 5-4). The main
difference is that the VT1.5/STS-1 paths desired for DRI should be provisioned for
drop and continue. As with the VT1.5/STS-1 path switched ring, path selection is
at the VT1.5/STS-1 level. The DDM-2000 OC-3 and OC-12 Multiplexer path
switched ring architecture allows mixing of drop and continue circuits with
standard path switched circuits. TSI flexibility is also maintained in the assignment
of low-speed ports to the high-speed interface.
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