Applications
Issue 8.0 July 2002
2-11
Dual Ring Interworking (DRI) 2
The DRI application consists of two ring networks that are interconnected by two
nodes in each ring. Figure 2-6 shows an example of the DRI application with Ring
A and Ring B.
■ Ring A is a line-switched ring equipped with FT-2000 OC-48
Add/Drop-Rings Terminals.
■ Ring B may be any of the following:
■ Another line-switched ring equipped with FT-2000 OC-48
Add/Drop-Rings Terminals
■ A path-switched ring equipped with DDM-2000 OC-3 Multiplexers
■ A path-switched ring equipped with DDM-2000 OC-12 Multiplexers
■ A path-switched ring equipped with
SLC
â
-2000 Access System
OC-3 Multiplexers.
The two rings may be electrically connected (DS3 and/or EC-1) and/or optically
connected using OC-3 or OC-12 interfaces.
The DRI application protects a circuit with one termination in one ring and the
other termination in another ring if one of the interconnecting nodes fails or a
connection between two interconnecting nodes fail. For each circuit with a
termination in both rings, one FT-2000 OC-48 Add/Drop-Rings Terminal is
designated as the primary node and one FT-2000 OC-48 Add/Drop-Rings
Terminal is designated as the secondary node.
The primary and secondary nodes may be designated on an STS-3 or STS-1
tributary basis. The primary node for one tributary may be the secondary node for
another tributary. A DRI circuit must be established using STS-3 or STS-1
cross-connections so that traffic is routed from the source node in the ring to the
primary node. From the primary node, the traffic is bridged to the secondary node.
For example, in Figure 2-6, if traffic is routed from Node 0 in Ring A to Node 5 and
bridged to Node 4, Node 5 is the primary node and Node 4 is the secondary node.
Different types of cross-connections are required at the primary and secondary
nodes. (The primary and secondary nodes are not required to be adjacent nodes.)
For more information about the cross-connections required at the primary and
secondary nodes for DRI protection switching, refer to Volume I, Section 9,
“Maintenance Description.”
In a DRI application with two line-switched rings equipped with FT-2000 OC-48
Add/Drop-Rings Terminals, the primary node in one ring may be connected to the
primary node in the other ring. For example, in Figure 2-6, Node 5 is the primary
node in Ring A and Node 1 is the primary node in Ring B.
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