363-206-305
Administration and Provisioning
Issue 3 June 2000
8-9
DS-1/T1 Multiplexing and Mapping
8
The DDM-2000 FiberReach Multiplexer uses the floating virtual tributary (VT)
mode, asynchronous mapping for clear channel DS1 transport. Each DS1 signal
is mapped to a VT1.5 signal; four VT1.5s are byte-interleaved to form a VT-G
signal; and seven VT-Gs are multiplexed to a VT-structured STS-1 signal. the STS-
1 signals are byte-interleaved to create STS-3, OC-3/OC-12, and STS-12 signals
respectively. The
ent-crs-vt1
command is used to enter cross-connections
between VT1.5 channels in the OC-1 interface and DS1/T1 ports. There are no
default cross-connections. See Chapter 11, "Commands and Reports," for more
information on this command.
In the opposite direction, a received OC-1 signal is converted back to the electrical
signal, and, for OC-3 and OC-12, demultiplexed to an STS-1 signal. The STS-1 is
demultiplexed to seven VT-Gs; each VT-G is separated into four VT1.5s; and a
DS1 signal is extracted from each VT1.5.
The mapping of a DS-1 to an OC-1 signal requires the port address being
connected with a time slot in the optical line interface unit (OLIU) circuit pack.
Optical time slots are identified in three parts: — STS-1 in the OC-1
*
, VT-G in the
STS-1, and VT1.5 in the VT-G.
Wideband Shelf Provisioning
8
The DDM-2000 FiberReach Multiplexer allows the user to customize many system
characteristics through its provisioning features. Provisioning parameters are set
by a combination of on-board switches and software control.
Only those system parameters fixed at installation time (for example, DS1 line
buildouts) are set with on-board switches. Some parameters needed for typical
installations, such as line coding, that may need to change later are settable by
switches and overridable by software. This allows typical installations to be
performed without a CIT. Other parameters that require a wide range of options or
in-service changes must be set under software control. For example, PM
thresholds and VT1.5 cross-connections can be customized for each installation
using the CIT interface.
Default Provisioning
8
Installation provisioning is minimized with thoughtfully chosen default values set in
the factory. Every parameter has a factory default value. These factory defaults for
* For the OC-1 interface, the STS-1 number is always 1.
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