363-206-285
Administration and Provisioning
Issue 3 June 2001
8-9
Each 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.
Table 8-2 shows the default mapping of DS1s to VT1.5s in the OC-3 signal on the
DDM-2000 OC-3 Multiplexer. In default mapping there is a direct relationship
between physical low-speed slot and port on that slot and the VT1.5 time slot
within the OC-3. For point-to-point networks, this default mapping allows
straightforward network administration because a circuit entering on a slot and
port on one shelf, for example a-1-1, will always exit at the same slot and port
position, a-1-1, at the far-end shelf. Default mapping can be overridden using the
ent-crs-vt1 and ent-crs-sts1 commands. See Section 11, "Commands
and Reports," for more information on these commands.
With this default mapping, each DS-1 port is associated with a specific timeslot —
aVT-GinanSTS-1andaspecificVT1.5inaVT-G.
All "a" location ports are associated with STS-1 number 1, "b" location ports are
associated with STS-1 number 2, and "c" location ports are associated with STS-1
number 3. The mapping of a DS-1 to an OC-3 signal requires the port address
being connected with a time slot in the optical line interface unit (OLIU) circuit
pack. Optical time slots identify the location; STS-1 in the OC-1, OC-3, or OC-12;
VT-G in the STS-1; VT1.5 in the VT-G. Some examples of time slot identifications
are:
m-1-1-1, m-2-1-3
a-1-1-3, b-3-1-4
Some examples of DS1 port to OC-3 timeslot using default VT1.5 cross-
connections are:
a-1-1 to m-1-1-1
b-5-3 to m-2-5-3
c-4-4 to m-3-4-4
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