R3303-HP HSR6800 Routers Layer 2 - WAN Configuration Guide

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LMI protocol
Frame relay uses the LMI protocol to set up virtual circuits and maintain their status between DTE and
DCE.
The system supports the following LMI standards:
• ITU-T Q.933 Annex A
• ANSI T1.617 Annex D
• Nonstandard LMI (compatible with other vendors)
To communicate correctly, the DTE and the DCE must use the same type of LMI.
LMI uses the status inquiry message and the status messages to maintain the link status and PVC status,
for example, to advertise new PVCs, detect deleted PVCs, monitor PVC status changes, and verify link
integrity. For these purposes, the DTE sends status inquiry messages regularly to the DCE to request for
the availability of individual PVCs. On receiving a status inquiry, the DCE responds with a status
message that describes the status of each virtual circuit on the physical link.
For a DTE, the status of a PVC is determined by the DCE; as for DCE, by the frame relay network.
Table 2
lists the major parameters ITU-T Q.933 Annex A uses for message exchange. You can configure
these parameters to optimize device performance.
Table 2 Parameter description for frame relay protocol
Device
role
Timer/counter
Value
ran
g
e
Default
value
Description
DTE
Full status polling
counter (N391)
1 to 255 6
Sets the frequency with which status inquires
expect a full status report.
Suppose the N391 is set to 5. Every fifth status
inquiry sent by the DTE will ask for a full status
report. The intermediate inquiries ask for a
keepalive exchange only.
Error threshold
counter (N392)
1 to 10 3
Sets the number of errors required for LMI to
declare a link dead, within the event count
specified by N393.
Monitored events
counter (N393)
1 to 10 4
Sets the monitored event count. If the number of
errors within the N393 status inquiries reaches
N392, the DTE considers that the error
threshold is reached.
Keepalive (link
integrity verification
polling) timer
(T391)
0 to 32767
0 means
LMI
disabled.
10
Sets the interval (in seconds) at which the DTE
sends a status inquiry message. An error is
recorded if no reply is received before the timer
expires.
DCE
Error threshold
counter (N392)
1 to 10 3
Sets the number of errors required for LMI to
declare a link dead, within the event count
specified by N393.
Monitored events
count (N393)
1 to 10 4 Sets the monitoring interval for error counts.