Riverstone Networks WICT1-12 - Manual (Page 163)

Riverstone Networks RS Switch Router User Guide Release 8.0 9-3
Packet-over-SONET Configuration Guide Configuring Automatic Protection Switching
9.3 CONFIGURING AUTOMATIC PROTECTION
SWITCHING
Automatic protection switching (APS) provides a mechanism to support redundant transmission circuits between
SONET devices. The RS supports the following APS features:
• Linear network topology. Ring topologies are not supported.
• 1+1 switching. Each working line is protected by one protecting line and the same signal is
transmitted on both the working and protecting lines. The two transmission copies that arrive at the
receiving end are compared, and the best copy is used. If there is a line failure or line degradation,
the end node switches the connection over to the protecting line.
Note In APS terminology, bridge means to transmit identical traffic on both the working
and protecting lines, while switch means to select traffic from either the protecting
line or the working line.
• Unidirectional switching, where one set of line terminating equipment (LTE) can switch the line
independent of the other LTE. Bidirectional switching (where both sets of LTEs perform a
coordinated switch) is not supported.
• Revertive switching. You can enable automatic switchover from the protecting line to the working
line after the working line becomes available.
If the working circuit is disrupted or the bit error rates on the working circuit exceed the configured thresholds, traffic
is automatically switched over to the protecting circuit. Any physical or logical characteristics configured for the
working port are automatically applied to the protecting port. This includes the IP address and netmask configured for
the interface, spanning tree protocol (STP), per-VLAN spanning tree (PVST), etc. Therefore, there is no need to
configure the protecting port separately. Any command applied to the PoS working port is mirrored onto the protecting
port automatically.
Table 9-1 PoS optional operating parameters
Parameter Default Value Configuration Command
Framing SONET
sonet set
<port>
framing sdh|sonet
Loopback Disabled
sonet set
<port>
loopback
Path tracing (none)
sonet set
<port>
pathtrace
Circuit identifier (none)
sonet set
<port>
circuit-id
Frame Check Sequence 32-bit
sonet set
<port>
fcs-16-bit
Scrambling Enabled
sonet set
<port>
no-scramble