HP 600 Series, Services And Applications

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There are two types of Status Enquiry/Status messages exchanged by
routers and the Frame Relay network:
Link Integrity Verification (Keep Alive). This message is sent
periodically to maintain link integrity, or in other words, keep the
link alive. Routers and the network exchange their send and receive
sequence numbers to maintain synchronization.
Full Status. This message provides routers with the status of all
available PVCs. Additionally, send and receive sequence numbers are
exchanged as in the case of the keep alive message.
Periodic Polling Routers are required to periodically poll the
network with a Status Enquiry message. This requirement holds whether
data is being exchanged over the interface or not. The default polling
interval is ten seconds. A number of keep alive polls are sent in between
full status polls.
Link Integrity Verification (Keep Alive) Both the router and the
network verify the integrity of the link with every Status Enquiry/Status
exchange. Send and receive sequence numbers are included in each LMI
message exchanged with the network. The network and attached rout-
ers verify that LMI messages are sent and received at the proper
intervals and ensure that sequence numbers increment properly. If an
LMI message is not received within a predetermined time period or the
sequence numbers are not the expected values, an error occurs. Routers
and the network allow a configurable number of errors within a
specified time interval (window). If this value is exceeded, the link is
removed from service.
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Linking Up with Frame Relay
Local Management Interface
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