System Management
Basic System Configuration Guide 285
Network Timing
In Time Domain Multiplexed (TDM)-based networks (for example, SONET or SDH circuit-
switched networks), the concept of network timing is used to prevent over-run or under-run
issues where circuits are groomed (rebundled) and switched. Hardware exists in each node
that takes a common clock derived from an internal oscillator, a specific receive interface, or
special BITS interface and provides it to each synchronous interface in the system. Usually,
each synchronous interface is allowed to choose between using the chassis-provided clock or
the clocking recovered from the received signal on the interface. The clocking is used to drive
the transmit side of the interface. The appropriate configuration at each node which defines
how interface clocking is handled must be considered when designing a network that has a
centralized timing source so each interface is operating in a synchronous manner.
The effect of timing on a network is dependent on the nature of the type of traffic carried on
the network. With bit-wise synchronous traffic (traditional circuit-based voice or video), non-
synchronous transmissions cause a loss of information in the streams affecting performance.
With packet-based traffic, the applications expect and handle jitter and latency inherent to
packet-based networks. When a packet-based network is used to carry voice or video traffic,
the applications use data compression and elasticity buffering to compensate for jitter and
latency. The network itself relies on appropriate Quality of Service (QoS) definitions and
network provisioning to further minimize the jitter and latency the application may
experience.
Power Supplies
SR OS supports a power-supply command to configure the type and number of power
supplies present in the chassis. The operational status of a power source is always displayed
by the LEDs on the Control Processor/Switch Fabric Module (CP/SFM) front panel, but the
power supply information must be explicitly configured in order for a power supply alarm to
be generated if a power source becomes operationally disabled.
Automatic Synchronization
Use the CLI syntax displayed below to configure synchronization components relating to
active-to-standby CPM switchover. In redundant systems, synchronization ensures that the
active and standby CPMs have identical operational parameters, including the active
configuration, CPM, XCM, and IOM images in the event of a failure or reset of the active
CPM.
The force-switchover command forces a switchover to the standby CPM card.
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