363-206-285
Administration and Provisioning
Issue 3 June 2001
8-13
OC-1/OC-3/OC-12 to OC-1/OC-3/OC-12 8
From each received OC-3 signal, an STS-3 signal is recovered. The STS-3 is
demultiplexed to three STS-1s, and the STS-1s are routed to other OC-3
interfaces as provisioned. Three STS-1s are multiplexed to an STS-3, converted
to an OC-3, and transmitted over the fiber.
OC-3 to OC-3 cross-connections can be done at the STS-1 level or at the
individual VT-1.5 (DS1 time slots) level. Example STS-1 cross-connections are:
m-1 to c-1
m-2 to c-2
m-3 to c-3
The following are some examples of VT1.5 time slot cross-connections for OC-3
to OC-3. These are representative of "pass-through" traffic in a DS1 hub network:
m-1-1-1 to c-1-1-1
m-3-1-4 to c-3-1-4
m-1-3-2 to b-1-3-2
m-2-1-1 to a-2-1-1
OC-3 to OC-1 8
OC-3 ring traffic is mapped into OC-1 extensions in the same way as any VT is
mapped into an OLIU. The VT tributaries are assigned to one of the two STS-1s
supported by the 27-type OLIUs. Two 27-type OLIUs are installed in the function
unit slots for single homing applications. In dual homing applications, each of the
two OC-3 shelves terminating the OC-1 ring extension is equipped with only one
27-type OLIU in a function unit slot. Each VT is mapped from the OC-3 OLIUs (for
example, m-1-1-1, m-2-1-1, m-3-1-1) into the 27-type OLIUs with two STS-1s
from which to choose (a-1 or a-2).
In the dual homing application, the user must map a VT from the OC-1 ring to the
same VT in the OC-3 ring at each of the two host nodes. For example, if at host
node #1, c-1-1-1 (OC-1 VT) is mapped to m-2-1-1 (OC-3 VT), the X-1-1-1
(X=a,b,c) OC-1 VT must also map to m-2-1-1 (OC-3 VT) at host node #2. Another
consideration in deploying the dual homing configuration is that different function
unit slots on the two host shelves must be used to terminate the OC-1 ring. If
function unit slot X-2 (X=a,b,c) is used on host node #1, function unit slot X-1
(X=a,b,c) must be used on host node #2.
The traffic that can be mapped from all OC-1 rings terminated on 27-type OLIUs in
function unit slots, to the OC-3 ring terminated on OLIUs in the main slots, is
limited by the capacity of the OC-3 ring to 84 VT (DS1s). Use of the hairpin
connections (described in the next section) increases the total traffic handling
capacity of the shelf since the hairpin connections do not consume bandwidth on
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