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Configuring and Monitoring PPP Functions
The following example enables link maintenance on port 1 of a PoS module in slot 8
and sets
to 3 and
to 10.
seconds
consecutive misses
config ppp echo 3 10 ports 8:1
Configuring PPP Link Quality Monitoring
The Link Control Protocol (LCP) establishes a logical connection with the peer LCP
entity through an exchange of configuration packets. Data traffic cannot flow over the
SONET link until LCP has successfully established this connection. LCP also allows the
negotiation of a quality monitoring protocol to monitor the viability of the PPP link on
a continuous basis. This process of determining data loss and link viability is referred to
as Link Quality Monitoring (LQM).
The LQM protocol uses the Link Quality Report (LQR) packet as a mechanism in the
test of the PPP link. The LQM protocol periodically transmits LQR packets containing
counts of packets and octets that have been transmitted and successfully received. This
information enables the LQM protocol to determine the percentage of data that is being
dropped due to poor link quality. If the drop percentage is greater than a configured
threshold, all network-layer protocols are brought down. Bringing a poor-quality link
down may be desirable when an alternate network path exists, or when billing is based
on the amount of data transmitted. By default, LQM is off.
To enable the LQM protocol on a specified PPP port, use the following command:
config ppp quality [off | <required_percent> {<seconds>}] ports <portlist>
The
parameter is an integer in the range from 1 to 99 that is used to
required_percent
determine the drop percentage threshold, where:
drop percentage threshold = (100–<required_percent>).
The optional
parameter is an integer in the range from 1 to 300. This parameter
seconds
value determines how often quality reports should be received from the peer LQR
entity. If you do not specify a value for the
parameter, the command uses the
seconds
default value of 30 seconds.
It can take up to seven reporting intervals for LCP to bring a link down. If the link
quality improves subsequent to being brought down, LCP automatically brings the link
back up. This type of service restoration takes a minimum of seven reporting intervals.
Packet Over SONET Module Installation and User Guide
3-29
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