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Table Of Contents
10.1 SONET Rings and TCC+/TCC2 Cards
10.2 Bidirectional Line Switched Rings
10.2.4 BLSR Application Sample
10.2.6 Two-Fiber BLSR to Four-Fiber BLSR Conversion
10.3 Linear ADM Configurations
10.4 Path-Protected Mesh Networks
SONET Topologies
This chapter explains Cisco ONS 15454 SONET topologies. To provision topologies, refer to the Cisco ONS 15454 Procedure Guide.
Chapter topics include:
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SONET Rings and TCC+/TCC2 Cards
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10.1 SONET Rings and TCC+/TCC2 Cards
Table 10-1 shows the SONET rings that can be created on each ONS 15454 node using redundant TCC+ cards.
Table 10-1 ONS 15454 Rings with Redundant TCC+ Cards
BLSRs1
2
2-Fiber BLSR
2
4-Fiber BLSR
1
Path Protection Configuration
52
1 Bidirectional Line Switching Ring
2 Total SDCC usage must be equal to or less than 10 SDCCs
Table 10-2 shows the SONET rings that can be created on each ONS 15454 node using redundant TCC2 cards.
Table 10-2 ONS 15454 Rings with Redundant TCC2 Cards
BLSRs
2
2-Fiber BLSR
2
4-Fiber BLSR
1
Path Protection Configuration
161
1 Total SDCC usage must be equal to or less than 32 SDCCs.
10.2 Bidirectional Line Switched Rings
ONS 15454 can support two concurrent BLSRs in one of the following configurations:
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Each BLSR can have up to 32 ONS 15454s. Because the working and protect bandwidths must be equal, you can create only OC-12 (two-fiber only), OC-48, or OC-192 BLSRs. For information about BLSR protection channels, see the "BLSR Protection Channel Circuits" section.
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10.2.1 Two-Fiber BLSRs
In two-fiber BLSRs, each fiber is divided into working and protect bandwidths. For example, in an OC-48 BLSR (Figure 10-1), STSs 1 - 24 carry the working traffic, and STSs 25 to 48 are reserved for protection. Working traffic (STSs 1 - 24) travels in one direction on one fiber and in the opposite direction on the second fiber. The Cisco Transport Controller (CTC) circuit routing routines calculate the shortest path for circuits based on many factors, including user requirements, traffic patterns, and distance. For example, in Figure 10-1, circuits going from Node 0 to Node 1 will typically travel on Fiber 1, unless that fiber is full, in which case circuits will be routed on Fiber 2 through Node 3 and Node 2. Traffic from Node 0 to Node 2 (or Node 1 to Node 3) can be routed on either fiber, depending on circuit provisioning requirements and traffic loads.
Figure 10-1 Four-Node, Two-Fiber BLSR
The SONET K1, K2, and K3 bytes carry the information that governs BLSR protection switches. Each BLSR node monitors the K bytes to determine when to switch the SONET signal to an alternate physical path. The K bytes communicate failure conditions and actions taken between nodes in the ring.
If a break occurs on one fiber, working traffic targeted for a node beyond the break switches to the protect bandwidth on the second fiber. The traffic travels in a reverse direction on the protect bandwidth until it reaches its destination node. At that point, traffic is switched back to the working bandwidth.
Figure 10-2 shows a traffic pattern sample on a four-node, two-fiber BLSR.
Figure 10-2 Four-Node, Two-Fiber BLSR Traffic Pattern Sample
Figure 10-3 shows how traffic is rerouted following a line break between Node 0 and Node 1.
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Figure 10-3 Four-Node, Two-Fiber BLSR Traffic Pattern Following Line Break
10.2.2 Four-Fiber BLSRs
Four-fiber BLSRs double the bandwidth of two-fiber BLSRs. Because they allow span switching as well as ring switching, four-fiber BLSRs increase the reliability and flexibility of traffic protection. Two fibers are allocated for working traffic and two fibers for protection, as shown in Figure 10-4. To implement a four-fiber BLSR, you must install four OC-48, OC-48AS, or OC-192 cards at each BLSR node.
Figure 10-4 Four-Node, Four-Fiber BLSR
Four-fiber BLSRs provide span and ring switching:
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Figure 10-5 Four-Fiber BLSR Span Switch
Figure 10-6 Four-Fiber BLSR Ring Switch
10.2.3 BLSR Bandwidth
BLSR nodes can terminate traffic coming from either side of the ring. Therefore, BLSRs are suited for distributed node-to-node traffic applications such as interoffice networks and access networks.
BLSRs allow bandwidth to be reused around the ring and can carry more traffic than a network with traffic flowing through one central hub. BLSRs can also carry more traffic than a path protection configuration operating at the same OC-N rate. Table 10-3 shows the bidirectional bandwidth capacities of two-fiber BLSRs. The capacity is the OC-N rate divided by two, multiplied by the number of nodes in the ring minus the number of pass-through STS-1 circuits. Table 10-4 shows the bidirectional bandwidth capacities of four-fiber BLSRs.
Table 10-3 Two-Fiber BLSR Capacity
OC-12
STS1-6
STS 7-12
OC-48
STS 1-24
STS 25-48
24 x N - PT
OC-192
STS 1-96
STS 97-192
96 x N - PT
1 N equals the number of ONS 15454 nodes configured as BLSR nodes.
2 PT equals the number of STS-1 circuits passed through ONS 15454 nodes in the ring (capacity can vary depending on the traffic pattern).
Figure 10-7 shows an example of BLSR bandwidth reuse. The same STS carries three different traffic sets simultaneously on different spans around the ring: one set from Node 3 to Node 1, another set from Node 1 to Node 2, and another set from Node 2 to Node 3.
Figure 10-7 BLSR Bandwidth Reuse
10.2.4 BLSR Application Sample
Figure 10-8 shows a two-fiber BLSR implementation sample. A regional long-distance network connects to other carriers at Node 0. Traffic is delivered to the service provider's major hubs.
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Figure 10-8 Five-Node BLSR
Figure 10-9 shows the shelf assembly layout for Node 0, which has one free slot. Figure 10-10 shows the shelf assembly layout for the remaining sites in the ring. In this BLSR configuration, an additional eight DS-3s at Node IDs 1 and 3 can be activated. An additional four DS-3s can be added at Node 4, and ten DS-3s can be added at Node 2. Each site has free slots for future traffic needs.
Figure 10-9 Shelf Assembly Layout for Node 0 in Figure 10-8
Figure 10-10 Shelf Assembly Layout for Nodes 1 to 4 in Figure 10-8
10.2.5 BLSR Fiber Connections
Plan your fiber connections and use the same plan for all BLSR nodes. For example, make the east port the farthest slot to the right and the west port the farthest slot to the left. Plug fiber connected to an east port at one node into the west port on an adjacent node. Figure 10-11 shows fiber connections for a two-fiber BLSR with trunk cards in Slot 5 (west) and Slot 12 (east). See the Cisco ONS 15454 Procedure Guide for fiber connection procedures.
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For four-fiber BLSRs, use the same east-west connection pattern for the working and protect fibers. Do not mix working and protect card connections. The BLSR will not function if working and protect cards are interconnected. Figure 10-12 shows fiber connections for a four-fiber BLSR. Slot 5 (west) and Slot 12 (east) carry the working traffic. Slot 6 (west) and Slot 13 (east) carry the protect traffic.
Figure 10-11 Connecting Fiber to a Four-Node, Two-Fiber BLSR
Figure 10-12 Connecting Fiber to a Four-Node, Four-Fiber BLSR
10.2.6 Two-Fiber BLSR to Four-Fiber BLSR Conversion
Two-fiber OC-48 or OC-192 BLSRs can be converted to four-fiber BLSRs. To convert the BLSR, install two OC-48 or OC-192 cards at each two-fiber BLSR node, then log into CTC and convert each node from two-fiber to four-fiber. The fibers that were divided into working and protect bandwidths for the two-fiber BLSR are now fully allocated for working BLSR traffic. See the Cisco ONS 15454 Procedure Guide for BLSR conversion procedures.
10.3 Linear ADM Configurations
You can configure ONS 15454s as a line of add/drop multiplexers (ADMs) by configuring one set of OC-N cards as the working path and a second set as the protect path. Unlike rings, linear (point-to-point) ADMs require that the OC-N cards at each node be in 1+1 protection to ensure that a break to the working line is automatically routed to the protect line.
Figure 10-13 shows three ONS 15454s in a linear ADM configuration. Working traffic flows from
Slot 5/Node 1 to Slot 5/Node 2, and from Slot 12/Node 2 to Slot 12/Node 3. You create the protect path by placing Slot 6 in 1+1 protection with Slot 5 at Nodes 1 and 2, and Slot 12 in 1+1 protection with Slot 13 at Nodes 2 and 3.Figure 10-13 Linear (Point-to-Point) ADM Configuration
10.4 Path-Protected Mesh Networks
In addition to single BLSRs, path protection configurations and ADMs, you can extend ONS 15454 traffic protection by creating path-protected mesh networks (PPMNs). PPMNs include multiple ONS 15454 SONET topologies and extend the protection provided by a single path protection configuration to the meshed architecture of several interconnecting rings. In a PPMN, circuits travel diverse paths through a network of single or multiple meshed rings. When you create circuits, you can have CTC automatically route circuits across the PPMN, or you can manually route them. You can also choose levels of circuit protection. For example, if you choose full protection, CTC creates an alternate route for the circuit in addition to the main route. The second route follows a unique path through the network between the source and destination and sets up a second set of cross-connections.
For example, in Figure 10-14 a circuit is created from Node 3 to Node 9. CTC determines that the shortest route between the two nodes passes through Node 8 and Node 7, shown by the dotted line, and automatically creates cross-connections at Nodes, 3, 8, 7, and 9 to provide the primary circuit path.
If full protection is selected, CTC creates a second unique route between Nodes 3 and 9 which, in this example, passes through Nodes 2, 1, and 11. Cross-connections are automatically created at Nodes 3, 2, 1, 11, and 9, shown by the dashed line. If a failure occurs on the primary path, traffic switches to the second circuit path. In this example, Node 9 switches from the traffic coming in from Node 7 to the traffic coming in from Node 11 and service resumes. The switch occurs within 50 ms.
Figure 10-14 Path-Protected Mesh Network
PPMN also allows spans with different SONET speeds to be mixed together in "virtual rings." Figure 10-15 shows Nodes 1, 2, 3, and 4 in a standard OC-48 ring. Nodes 5, 6, 7, and 8 link to the backbone ring through OC-12 fiber. The "virtual ring" formed by Nodes 5, 6, 7, and 8 uses both OC-48 and OC-12 cards.
Figure 10-15 PPMN Virtual Ring
10.5 Four Node Configurations
You can link multiple ONS 15454s using their OC-N cards (that is, create a fiber-optic bus) to accommodate more access traffic than a single ONS 15454 can support. See the Cisco ONS 15454 Procedure Guide for procedures. For example, to drop more than 112 DS-1s or 96 DS-3s (the maximum that can be aggregated in a single node), you can link the nodes but not merge multiple nodes into a single ONS 15454. You can link nodes with OC-12 or OC-48 fiber spans as you would link any other two network nodes. The nodes can be grouped in one facility to aggregate more local traffic.
Figure 10-16 shows a four-shelf node setup. Each shelf assembly is recognized as a separate node in the ONS 15454 software interface and traffic is mapped using CTC cross-connect options. In Figure 10-16, each node uses redundant fiber-optic cards. Node 1 uses redundant OC-N transport and OC-N bus (connecting) cards for a total of four cards, with eight free slots remaining. Nodes 2 and 3 each use two redundant OC-N bus cards for a total of four cards, with eight free slots remaining. Node 4 uses redundant OC-12 bus cards for a total of two cards, with ten free slots remaining. The four-node example presented here is one of many ways to set up a multiple-node configuration.
Figure 10-16 Four-Shelf Node Configuration
10.6 Optical Speed Upgrades
A span is the optical fiber connection between two ONS 15454 nodes. In a span (optical speed) upgrade, the transmission rate of a span is upgraded from a lower to a higher OC-N signal but all other span configuration attributes remain unchanged. With multiple nodes, a span upgrade is a coordinated series of upgrades on all nodes in the ring or protection group. You can perform in-service span upgrades for the following ONS 15454 cards:
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Use the XC10G card, the TCC+ card, Software R3.1 or later, and the 15454-SA-ANSI shelf assembly to enable the OC48AS and the OC192 cards. The TCC2 card also supports OC48AS and OC192 cards, but Software R4.0 must be used.
To perform a span upgrade, the higher-rate optical card must replace the lower-rate card in the same slot. If the upgrade is conducted on spans residing in a BLSR, all spans in the ring must be upgraded. The protection configuration of the original lower-rate optical card (two-fiber BLSR, four-fiber BLSR, path protection configuration, and 1+1) is retained for the higher-rate optical card.
When performing span upgrades on a large number of nodes, Cisco recommends that you upgrade all spans in a ring consecutively and in the same maintenance window. Until all spans are upgraded, mismatched card types will be present.
Cisco recommends using the Span Upgrade Wizard to perform span upgrades. Although you can also use the manual span upgrade procedures, the manual procedures are mainly provided as error recovery for the wizard. The Span Upgrade Wizard and the Manual Span Upgrade procedures require at least two technicians (one at each end of the span) who can communicate with each other during the upgrade. Upgrading a span is non-service affecting and will cause no more than three switches, each of which is less than 50 ms in duration.
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10.6.1 Span Upgrade Wizard
The Span Upgrade Wizard automates all steps in the manual span upgrade procedure (BLSR, Path Protection Configuration, and 1+1). The wizard can upgrade both lines on one side of a four-fiber BLSR or both lines of a 1+1 group; the wizard upgrades path protection configurations and two-fiber BLSRs one line at a time. The Span Upgrade Wizard requires that spans have DCCs enabled.
The Span Upgrade Wizard provides no way to back out of an upgrade. In the case of an error, you must exit the wizard and initiate the manual procedure to either continue with the upgrade or back out of it. To continue with the manual procedure, examine the standing conditions and alarms to identify the stage in which the wizard failure occurred.
10.6.2 Manual Span Upgrades
Manual span upgrades are mainly provided as error recovery for the Span Upgrade Wizard, but they can be used to perform span upgrades. Downgrading can be performed to back out of a span upgrade. The procedure for downgrading is the same as upgrading except that you choose a lower-rate card type. You cannot downgrade if circuits exist on the STSs that will be removed (the higher STSs).
Four manual span upgrade options are available:•
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