This document describes how you can provision timing on ONS 15454
through Cisco Transport Controller (CTC). CTC provides two methods for you to
provision timing and modify the settings:
At the node level, you can configure timing from the
Provisioning/Timing tab. Here, you can provision different
timing modes and references for the entire node.
At each optical port, you can change the default Synchronous Status
Message (SSM) settings.
Cisco recommends that you have knowledge of these topics:
The information in this document is based on these software and
The information in this document was created from the devices in a
specific lab environment. All of the devices used in this document started with
a cleared (default) configuration. If your network is live, make sure that you
understand the potential impact of any command.
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The node level comprises three configuration sections:
The General Timing section defines:
Some options in other sections depend on the timing mode you select in
this section. Figure 1 shows the default
Figure 1 – Provision General Timing
The Timing Control Card (TCC) always acts as an SSM Generation 2
(Gen2)-capable device for incoming SSM regardless of the settings here. Through
provisioning, TCC can translate Gen2 messages into Generation 1 (Gen1)
messages. TCC or outputs use the translated messages. For example, assume that
SSM Message Set is provisioned to be Gen1, and a Gen2 message comes in. TCC
displays the Gen2 message for the inbound interface in the
Conditions tab. However, TCC translates the message into a
Gen1 equivalent message for the NE-SYNC and outputs. During Gen2 to Gen1
translation, TCC always uses a nearest lower quality message for a higher
quality message. For example, TCC translates ST3E (quality level 5) into ST3
(quality level 4).
Revertive timing means that the TCC reverts to the highest priority
reference with the best SSM quality level. Non-revertive timing means that the
TCC chooses the best quality reference available, and does not change with
regard to priority. You can define Priority in the Reference Lists
Use the BITS Facilities section to provision two BITS In and two BITS
Out ports. In order to enable a BITS port, change the state from OOS (out of
service) to IS (in service). Figure 2 shows the
Figure 2 – Provision BITS Facilities for
Cisco recommends two external timing devices for redundancy. The
incoming BITS signal is a 1.544 MHz DS-1 (for SONET systems) formatted as
Superframe (SF) or Extended Superframe (ESF). SSM requires ESF. BITS coding and
framing are applicable to both In and Out ports in releases earlier than
For SDH systems, BITS Facilities can be E1, 2.048 MHz, or 64 kHz. You
must provision appropriate coding and framing to match the source.
Ensure that the BITS In source is Primary Reference Source (PRS) or
Primary Reference Clock (PRC). Additionally, ensure that a metallic timing
source, for example, a Global Positioning System (GPS) clock or a timing T1,
directly delivers the BITS In source. Cisco does not recommend a regular data
T1 because the 1s density cannot be guaranteed. A timing T1 is a T1 with all
When you check the Enabled check box for Sync.
Messaging, TCC expects to receive SSM from BITS In ports. Here, the BITS source
provides SSM. If a BITS source does not provide SSM capability, do not check
the Enabled check box. When you do not enable SSM, a Sync
Traceability Unknown (STU) message appears for BITS In when the clock signal is
within bounds. Otherwise the Do Not Use (DUS) message appears. In release 5.0
and later, Admin SSM option is available when the clock source does not support
SSM. Instead of the default STU, you can set other messages, for example,
When you do not enable BITS In SSM, the AIS Threshold option is
available to alert external devices timed from BITS Out for timing failures.
When the line clock quality is below the selected threshold, AIS is sent on
BITS Out. The default threshold is SMC (S1 = 1100) for DS1 and G812L (S1 =
1000) for 2 MHz. Cisco recommends Synchronous Equipment Timing Supply (SETS) so
that any signal with quality above or equal to SETS does not result in an
absence of signal. AIS is unframed all 1s signal for DS1 and no signal for 2
BITS Out SSM derives from the SSM of the active line, and always sends
SSM if the facility supports SSM. If the SSM values of the lines are DUS, BITS
Out sends DUS. If you disable SSM for the active line (at the port level), BITS
Out sends STU.
The Reference Lists section enables you to configure timing references
and BITS Out source. You can configure the priority of each reference. The
priority can range from Ref-1, also called Primary Reference, with the highest
priority, to Ref-3, or Third Reference, with the lowest priority (see
Figure 3 – Provision Reference Lists
This table indicates that the available options in the references
depend on the Timing Mode selected earlier:
BITS1, BITS2, Internal clock
Any synchronous IO port(s), Internal clock
BITS1, BITS2, any synchronous IO port(s), Internal
Note: When you provision 1+1 protection between two optical ports, you can
provision only the working port as a timing reference. The protect port is
automatically selected during a switch.
When a port is selected for timing, EnableSyncMsg is checked on that
IO port (see the Configure Timing at the Optical IO
Card Level section). Also note that to delete a card from the chassis,
you cannot provision the ports on that card as a reference.
For BITS Out references, select the synchronous IO ports as the source.
Options for BITS Out are IO ports, NE Reference, or None.
Use the Maintenance/Timing tab to monitor the status
and conditions of references. Figure 4 shows a
Figure 4 – Reference Status Report
The report displays the Timing Mode of Line at the top. The NE clock
section indicates that the current clock status is Holdover. The reference
section contains an X in the Selected column to indicate the current NE
reference. The Condition column displays the current reference quality as OKAY.
If the reference quality is not OKAY, this column displays OOB (Out of Bounds).
The SSM column shows the SSM processing status, and the SSM Quality column
indicates the message type. The internal clock does not process incoming SSM.
Therefore, the SSM column displays the value 'disabled'.
You can also perform manual reference switching in the
Maintenance/Timing tab. User-initiated protection request
commands can be of two types:
Forced Switch—A Forced Switch request against the
active reference switches to a valid reference, even if the new reference has a
worse SSM value.
Manual Switch—A Manual Switch request against the
active (or selected) reference causes a reference switch to the standby
reference. However, the switch occurs only if the standby reference is healthy
and has the same quality level as the active
Each optical IO card has four settings relevant to synchronization for
each port (see Figure 5):
ProvidesSync: The ProvidesSync check box is
automatically checked if you configure that port as one of the line timed
references. If so, you cannot uncheck this option in the Port Provisioning
window (display only).
EnableSyncMsg: The EnableSyncMsg check box is
checked by default. You can uncheck this option to turn off SSM. Incoming SSM
is processed by default. This setting does not affect outgoing SSM (always
Send DoNotUse: The Send DoNotUse check box is not
checked by default. You can check this option to always send
State: The State column indicates whether a port is
IS or OOS. If a port is OOS, the port is not used for line timing
Figure 5 – Provision Port Level Timing
If you uncheck EnableSyncMsg, an SSM-OFF condition occurs for the port.
You can observe the change in the Maintenance/Timing tab. The
SSM-STU condition occurs if the reference is good. DUS occurs if the reference
fails. When you disable SSM, timing loops can occur. If the remote port is to
send DUS, the receiving port continues to consider the remote port as a
potential reference when you disable SSM. Cisco strongly recommends that you
retain the default setting (SSM enabled) unless there are specific reasons that
require SSM to be disabled.
If two optical ports are in a 1+1 protection group, you can change
card-level timing settings only on the working port. The protect port
automatically reflects any changes you make on the working port.
Whenever you select a port as the active timing reference for a node,
reference is always sent back to the upstream node automatically. This is part
of the SSM mechanism, and requires no configuration.
A downstream node can report DUS when Send DoNotUse is enabled on the
sending port of an upstream node, and EnableSyncMsg is enabled on the receiving
port. If you enable Send DoNotUse, the port is never used as a timing source
for the downstream node. Therefore, do not enable Send DoNotUse, unless you use
a lab setup, or some special setup where you need to cross network boundaries.
For example, Cisco recommends that you transmit DUS between two carriers and
from customers to carriers.