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Table Of Contents
6.1.3 Circuit Protection Types
6.3 VT Tunnels and Aggregation Points
6.5 Go-and-Return Path Protection Routing
6.6 BLSR Protection Channel Access Circuits
Circuits and Tunnels
Note
The terms "Unidirectional Path Switched Ring" and "UPSR" may appear in Cisco literature. These terms do not refer to using Cisco ONS 15xxx products in a unidirectional path switched ring configuration. Rather, these terms, as well as "Path Protected Mesh Network" and "PPMN," refer generally to Cisco's path protection feature, which may be used in any topological network configuration. Cisco does not recommend using its path protection feature in any particular topological network configuration.
This chapter explains Cisco ONS 15327 synchronous transport signal (STS) and virtual tributary (VT) circuits and VT and data communications channel (DCC) tunnels. To provision circuits and tunnels, refer to the Cisco ONS 15327 Procedure Guide.
Chapter topics include:
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6.1 Circuit Properties
On the ONS 15327 you can create unidirectional and bidirectional circuits. For path protection circuits, you can create revertive or nonrevertive circuits. Circuits are routed automatically or you can manually route them. With the autorange feature, you do not need to build multiple circuits of the same type individually; the Cisco Transport Controller (CTC) can create additional sequential circuits if you specify the number of circuits you need and build the first circuit.
You can provision circuits either before or after cards are installed if the ONS 15327 slots are provisioned for the card that carries the circuit. However, circuits do not carry traffic until the cards are installed and the ports are In-Service and Normal (IS-NR); Out-of-Service and Autonomous, Automatic In-Service (OOS-AU,AINS); or Out-of-Service and Management, Maintenance (OOS-MA,MT).
The ONS 15327 Circuits window, which appears in network, node, and card view, is where you can view information about circuits. The Circuits window shows the following information:
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6.1.1 Circuit Status
The circuit statuses that appear in the Circuit window Status column are generated by CTC based on conditions along the circuit path. Table 6-1 shows the statuses that can appear in the Status column.
Table 6-1 ONS 15327 Circuit Status
CREATING
CTC is creating a circuit.
DISCOVERED
CTC created a circuit. All components are in place and a complete path exists from circuit source to destination.
DELETING
CTC is deleting a circuit.
PARTIAL
A CTC-created circuit is missing a cross-connect or network span or a complete path from source to destinations does not exist.
In CTC, circuits are represented using cross-connects and network spans. If a network span is missing from a circuit, the circuit status is PARTIAL. However, a PARTIAL status does not necessarily mean a circuit traffic failure has occurred, because traffic may flow on a protect path.
Network spans are in one of two states: up or down. On CTC circuit and network maps, up spans appear as green lines, and down spans appear as gray lines. If a failure occurs on a network span during a CTC session, the span remains on the network map but its color changes to gray to indicate that the span is down. If you restart your CTC session while the failure is active, the new CTC session cannot discover the span and its span line does not appear on the network map.
Subsequently, circuits routed on a network span that goes down appear as DISCOVERED during the current CTC session, but appear as PARTIAL to users who log in after the span failure.
DISCOVERED_TL1
A TL1-created circuit or a TL1-like, CTC-created circuit is complete. A complete path from source to destinations exists.
PARTIAL_TL1
A TL1-created circuit or a TL1-like, CTC-created circuit is missing a cross-connect or circuit span (network link), and a complete path from source to destinations does not exist.
CONVERSION_PENDING
An existing circuit in a topology upgrade is set to this state. The circuit returns to the DISCOVERED status once the topology upgrade is complete. For more information about topology upgrades, see "SONET Topologies and Upgrades."
PENDING_MERGE
Any new circuits created to represent an alternate path in a topology upgrade are set to this status to indicate that it is a temporary circuit. These circuits can be deleted if a topology upgrade fails. For more information about topology upgrades, see "SONET Topologies and Upgrades."
6.1.2 Circuit States
The circuit service state is an aggregate of the cross-connect service states within the circuit.
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You can assign a service state to circuit cross-connects at two points:
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During circuit creation, you can apply a service state to the drop ports in a circuit; however, CTC does not apply a requested state other than IS-NR to drop ports if:
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Circuits do not use the soak timer, but ports do. The soak period is the amount of time that the port remains in the OOS-AU,AINS service state after a signal is continuously received. When the cross-connects in a circuit are in the OOS-AU,AINS service state, the ONS 15327 monitors the cross-connects for an error-free signal. It changes the state of the circuit from OOS to IS or to OOS-PARTIAL as each cross-connect assigned to the circuit path is completed. This allows you to provision a circuit using TL1, verify its path continuity, and prepare the port to go into service when it receives an error-free signal for the time specified in the port soak timer. Two common examples of state changes you see when provisioning circuits using CTC are:
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To find the remaining port soak time, choose the Maintenance > AINS Soak tabs in card view and click the Retrieve button. If the port is in the OOS-AU,AINS service state and has a good signal, the Time Until IS column shows the soak count down status. If the port is OOS-AU,AINS and has a bad signal, the Time Until IS column indicates that the signal is bad. You must click the Retrieve button to obtain the latest time value.
For more information about port and cross-connect service states, see "Administrative and Service States."
6.1.3 Circuit Protection Types
The Protection column on the Circuit window shows the card (line) and SONET topology (path) protection used for the entire circuit path. Table 6-2 shows the protection type indicators that you see in this column.
6.1.4 Edit Circuits Window
Use the Edit Circuits window to view general circuit information, create monitor circuits, change a circuit state, and merge circuits. For path protection circuits, use the Edit Circuits window to change path protection selectors and switch protection paths.
In the UPSR Selectors subtab on the Edit Circuits window, you can:
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In the UPSR Switch Counts subtab, you can:
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Using the Edit Circuits window you can view a detailed circuit map by checking Show Detailed Map. The detailed map allows you to view information about ONS 15327 circuits graphically. Routing information that appears includes:
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For BLSRs, the detailed map shows the number of BLSR fibers and the BLSR ring ID. For path protection configurations, the map shows the active and standby paths from circuit source to destination, and it also shows the working and protect paths.
Alarms and states can also be viewed on the circuit map, including:
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By default, the working path on the detailed circuit map is indicated by a green bidirectional arrow, and the protect path is indicated by a purple bidirectional arrow. Source and destination ports are shown as circles with an S and D. Port states are indicated by colors, shown in Table 6-3.
Table 6-3 Port State Color Indicators
Green
IS-NR
Gray
OOS-MA,DSBLD
Purple
OOS-AU,AINS
Light blue
OOS-MA,MT
Notation within or by the squares on each node indicate switches and other conditions. For example:
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Move the mouse cursor over nodes, ports, and spans to see tooltips with information including the number of alarms on a node (organized by severity), a port's service state, and the protection topology.
Right-click a node, port, or span on the detailed circuit map to initiate certain circuit actions:
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6.2 VT1.5 Bandwidth
The ONS 15327 XTC card performs port-to-port, time-division multiplexing (TDM). Because VT1.5 multiplexing is STS-based, understanding how VT1.5 circuits use the XTC VT matrix resources is necessary to avoid unexpected depletion of the VT matrix capacity. The key VT matrix principles are as follows:
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The XTC card can map up to 24 STSs for VT1.5 traffic. Because one STS can carry 28 VT1.5s, the XTC card can terminate up to 672 VT1.5s or 336 VT1.5 cross-connects. However, to terminate 336 VT1.5 cross-connects:
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6.3 VT Tunnels and Aggregation Points
To maximize XTC VT1.5 cross-connect resources, you can tunnel VT1.5 circuits through ONS 15327 nodes. VT1.5 tunnels do not use VT matrix capacity at ONS 15327 pass-through nodes, thereby freeing the XTC card cross-connect resources for other VT1.5 circuits.
VAPs allow you to provision BLSR circuits from multiple VT1.5 sources to a single STS destination. Like circuits, a VAP has a source and a destination. The source is the STS grooming end, the node where the VT1.5 circuits are aggregated into a single STS. The VAP STS must be a port on an OC-N card. VT matrix resources are not used on the VAP source node, which is the key advantage of VAPs. The VAP destination is the node where the VT1.5 circuits originate. Circuits can originate on any ONS 15327 card.
6.4 DCC Tunnels
SONET provides four DCCs for network element operations, administration, maintenance, and provisioning: one on the SONET Section layer (DCC1) and three on the SONET Line layer (DCC2, DCC3, DCC4). The ONS 15327 uses the section DCC for ONS 15327 management and provisioning. When multiple DCC channels exist between two neighboring nodes, the ONS 15327 balances traffic over the existing DCC channels using a load balancing algorithm. This algorithm chooses a DCC for packet transport by considering packet size and DCC utilization.
You can use the three Line DCCs (LDCCs) and the Section DCC (SDCC), when not used for ONS 15327 DCC terminations, to tunnel third-party SONET equipment across ONS 15327 networks. A DCC tunnel end-point is defined by Slot, Port, and DCC, where DCC can be either the SDCC or one of the LDCCs. You can link an SDCC to an LDCC and an LDCC to an SDCC. You can also link LDCCs to LDCCs and link SDCCs to SDCCs. To create a DCC tunnel, you connect the tunnel endpoints from one ONS 15327 optical port to another.
Table 6-4 shows the DCC tunnels that you can create.
Table 6-4 DCC Tunnels
DCC1
Section
D1 to D3
Yes
DCC2
Line
D4 to D6
Yes
DCC3
Line
D7 to D9
Yes
DCC4
Line
D10 to D12
Yes
When you create DCC tunnels, keep the following guidelines in mind:
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6.5 Go-and-Return Path Protection Routing
The go-and-return path protection routing option allows you to route the path protection working path on one fiber pair and the protect path on a separate fiber pair (Figure 6-1). The working path will always be the shortest path. If a fault occurs, both the working and protection fibers are not affected. This feature only applies to bidirectional path protection circuits. The go-and-return routing option appears on the Circuit Attributes panel of the Circuit Creation wizard.
Figure 6-1 Path Protection Go-and-Return Routing
6.6 BLSR Protection Channel Access Circuits
You can provision circuits to carry traffic on BLSR PCA circuits when conditions are fault-free. Traffic routed on BLSR PCA circuits, called extra traffic, has lower priority than the traffic on the working channels and is unprotected. During ring or span switches, PCA circuits are preempted and squelched. For example, in an OC-48 BLSR, STSs 25-48 can carry extra traffic when no ring switches are active, but PCA circuits on these STSs are preempted when a ring switch occurs. When the conditions that caused the ring switch are remedied and the ring switch is removed, PCA circuits are restored. If the BLSR is provisioned as revertive, this occurs automatically after the fault conditions are cleared and the reversion timer has expired.
Traffic provisioning on BLSR PCA circuits is performed during circuit provisioning. The Protection Channel Access check box appears whenever Fully Protected Path is unchecked on the Circuit Creation wizard. Refer to the Cisco ONS 15327 Procedure Guide for more information.
6.7 Path Trace
The SONET J1 Path Trace is a repeated, fixed-length string comprised of 64 consecutive J1 bytes. You can use the string to monitor interruptions or changes to circuit traffic. Table 6-5 shows the ONS 15327 cards that support path trace.
Table 6-5 ONS 15327 Cards Capable of Path Trace
Transmit and receive
XTC (DS-1)
G1000-2
Receive only
OC3 IR 4 1310
OC12 IR 1310
OC12 LR 1550
OC48-1-IR
OC48 LR 1550
The J1 path trace transmits a repeated, fixed-length string. If the string received at a circuit drop port does not match the string the port expects to receive, an alarm is raised. Two path trace modes are available:
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6.8 Merge Circuits
A circuit merge combines a single selected circuit with one or more circuits. You can merge tunnels, VAP circuits, VLAN-assigned circuits, CTC-created circuits, and TL1-created circuits. To merge circuits, you choose a circuit on the CTC Circuits window and the circuits that you want to merge with the chosen (master) circuit on the Merge tab in the Edit Circuits window. The Merge tab shows only the circuits that are available for merging with the master circuit:
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If all connections from the master circuit and all connections from the merged circuits align to form one complete circuit, the merge is successful. If all connections from the master circuit and some, but not all, connections from the other circuits align to form a single complete circuit, CTC notifies you and gives you the chance to cancel the merge process. If you choose to continue, the aligned connections merge successfully into the master circuit, and un-aligned connections remain in the original circuits.
All connections from the master circuit and at least one connection from the other selected circuits must be used in the resulting circuit for the merge to succeed. If a merge fails, the master circuit and all other circuits remain unchanged. When the circuit merge completes successfully, the resulting circuit retains the name of the master circuit.
6.9 Reconfigure Circuits
You can reconfigure multiple circuits, which is typically necessary when a large number of circuits are in the PARTIAL status. When reconfiguring multiple circuits, the selected circuits can be any combination of DISCOVERED, PARTIAL, DISCOVERED_TL1, or PARTIAL_TL1 circuits. You can reconfigure tunnels, VAP circuits, VLAN-assigned circuits, CTC-created circuits, and TL1-created circuits.
Use the CTC Tools > Circuits > Reconfigure Circuits command to reconfigure selected circuits. During reconfiguration, CTC reassembles all connections of the selected circuits into circuits based on path size, direction, and alignment. Some circuits may merge and others may split into multiple circuits. If the resulting circuit is a valid circuit, it appears as a DISCOVERED circuit. Otherwise, the circuit appears as a PARTIAL or PARTIAL_TL1 circuit.
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