9500 MXC User Manual
3DB 23063 ADAA - Rev 004 July 2007 Vol. II-3-93
Protection Switching Criteria
In this section, switching criteria and service restoration times are provided.
Refer to:
• Switching Guard Times
• Hot-standby and Diversity Switching Criteria
• Dual Protection Switching Criteria on page 3-97
• Ring Protection Switching Criteria on page 3-98
• DAC Protection Switching Criteria on page 3-100
Switching Guard Times
To prevent protection switch oscillation a switch oscillation guard time
mechanism applies to all forms of online
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protection switching. The mechanism
is described below.
• A period of guard time begins immediately after each protection switch occurs.
• No protection switches are permitted during the guard time. Protection
switching may resume once the guard time has elapsed.
• To damp possible oscillations in the system the guard time is regularly adjusted,
using the following rules:
• The guard time doubles after each switch (up to the maximum)
• The guard time halves after each period of guard time during which no
switching occurs (down to the minimum).
• When the guard time decays to its minimum, subsequent switch requests are
actioned immediately.
• There are two independent guard timers for each protection context, one
associated with TX switching and one associated with RX switching.
• The switch guard time has a minimum period of 5 seconds and a maximum
period of 320 seconds (5 x 26 events).
• The guard time mechanism is disabled in protection diagnostic modes.
Hot-standby and Diversity Switching Criteria
The Tx and Rx paths are independently switched. Protection criteria are similar
for all RACs. Refer to:
• Transmitter Switching on page 3-94
• Receiver Switching on page 3-96
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It does not apply to diversity-bus (hitless) Rx path switching.
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