Frame Relay Protocol Parameters - 3Com MSR 50 Series Configuration Manual

236 C 8: F R
HAPTER RAME ELAY
Frame Relay Protocol
Parameters
C
ONFIGURATION
SVCs, which are automatically created and deleted by frame relay protocol. At
present, the most frequently used in frame relay is the PVC mode, that is.,
manually configured virtual circuit.
In the PVC mode, the availability of the virtual circuit should be checked. Local
management interface (LMI) protocol can implement this function. It is used to
maintain PVC table of frame relay protocol, including advertising added PVC entry,
detecting deleted PVC entry, monitoring PVC status change, and verifying PVC link
integrity. The system supports three LMI protocols: ITU-T Q.933 Appendix A, ANSI
T1.617 Appendix D and nonstandard compatible protocol. Their basic operating
mode is: DTE sends one Status Enquiry message to query the virtual circuit status
at a certain interval. After the DCE receives the message, it will immediately use
the Status message to inform DTE of the status of all the virtual circuits on current
interface.
The PVC status on DTE is completely determined by DCE, and the network
determines the PVC status on DCE. If two network devices are directly connected,
the equipment administrator sets the virtual circuit status of DCE.
Table 1 lists the parameters of frame relay.
Table 1 Parameter description for frame relay protocol
Operating mode
DTE
DCE
These parameters are stipulated by Q.933 Appendix A, and their meanings are
described as follows:
Meanings of parameters related to DTE operating mode:
N391: DTE sends a Status-Enquiry message at a certain interval (determined by
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T391). There are two types of Status-Enquiry messages: link integrity
verification message and link status enquiry message. Parameter N391 defines
the ratio of sending the two types of messages, that is, number of link integrity
verification messages : number of link status enquiry messages = N391-1: 1
N392: it sets the threshold for errors among the observed events.
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N393: it sets the total of observed events.
■
T391: it sets the interval for a DTE to send State-Enquiry messages.
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Parameter description
Request PVC status
counter (N391)
Error threshold (N392)
Event counter (N393)
User side polling timer
(T391), the value 0
indicates that LMI protocol
is disabled
Error threshold (N392)
Event counter (N393)
Network side polling timer
(T392)
Value range Default value
1 to 255 6
1 to 10 3
1 to 10 4
0 to 32767 10
(in seconds) (in seconds)
1 to 10 3
1 to 10 4
5 to 30 15
(in seconds) (in seconds)