User Manual

Enterasys X-Pedition User Reference Manual 121
Configuring Automatic Protection Switching
Note: The XP will display VLAN and interface names up to 32 characters in length.
3. If you want to increase the MTU size on a port, specify the parameter mtu with the ‘port set’
command and define a value up to 65442 (octets). See Configuring Jumbo Frames on
page 140 for more information.
4. Specify the bit error rate thresholds, if necessary. See Specifying Bit Error Rate Thresholds on
page 123 for more information.
5. Modify any other PoS operating parameters, as needed. The following table lists the operating
parameters that you can modify and the configuration commands that you use.
Configuring Automatic Protection Switching
Automatic protection switching (APS) provides a mechanism to support redundant transmission
circuits between SONET devices. The XP 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 applied to the protecting port. This includes the
Table 7: 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