363-206-285
Administration and Provisioning
Issue 3 June 2001
8-23
Cross-Connection Types 8
DDM-2000 OC-3 Multiplexers have time slot interchange (TSI) features. This
offers users flexibility in directing traffic in and out of these systems to support a
wide variety and range of customer applications.
Cross-connections in DDM-2000 OC-3 Multiplexers are made by specifying the
SONET rate (VT1.5 and STS-1), the end point addresses (access identifiers), the
cross-connection type (two-way, drop and continue, etc.), and, in some cases, the
ring direction (ring=m1, ring=m2, etc.). In DDM-2000 OC-3 Multiplexers, each
single cross-connection command establishes a two-way cross-connection.
The basic type of cross-connection allows a low-speed port or channel to be
cross-connected to a channel in the high-speed interface portion of the shelf. This
is used in all linear add/drop applications where DS1, DS3, VT1.5, STS-1, and
EC-1 low-speed signals are cross-connected to VT1.5 and STS-1 channels in the
high-speed linear interfaces.
The next type of cross-connection allows a low-speed port or channel to be cross-
connected to a channel in the high-speed ring interface. This is used in all path
switched ring applications where DS1, DS3, VT1.5, STS-1, and EC-1 low-speed
signals are cross-connected to VT1.5 or STS-1 channels in both rotations of the
rings terminating on the high-speed interfaces. With this cross-connection, all
added signals are bridged on to both rotations of the ring, and the better of the two
signals received from the two rotations of the ring is dropped.
Another type of cross-connection allows a VT1.5 or STS-1 channel to be "passed-
through" between two high-speed ring interfaces or between two OC-1 ring
interfaces supported by 27G2-U OLIUs in function units. This is used in all path
switched ring applications at nodes where traffic is not dropped. In path switched
rings, pass-through grooming (passing a signal on a ring time slot that is different
from the ring time slot on which it was received) is not supported.
End-to-end survivable service facilities need to cross multiple rings
interconnected at multiple wire centers. To support these applications, a drop-and-
continue cross-connection is provided for a signal from a high-speed channel to
be dropped to a specified low-speed port or channel and continued on to the next
node in the same direction while also adding a corresponding signal from the low-
speed port or channel to the high-speed channel in the other rotation of the ring.
A variation of ring cross-connections, the "locked cross-connection," is supported
at the VT1.5 level to lock the path selector to a specified rotation of the ring. With
this cross-connection, a DS1 or VT1.5 signal from the low-speed interface is
cross-connected to the specified VT1.5 channel in the high-speed interface in the
specified direction; and any signal received in the same VT1.5 channel from the
other ring rotation is ignored.
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