# Unit Detail

# Unit Monitoring

# LMI Support

#### LMI Sourcing

#### Net-DDS / T1

#### Net-DTE

#### Pass through

#### User-DDS / TI

#### User-DTE

  Local Management Interface (LMI) operates as a polling protocol between the user DTE and the carrier switch and provides the user with connection information relevant to (PVC) operating over the Frame Relay interface. Periodic polls are conducted between the user and the carrier switch in the form of polling messages; LMI Status Enquiry (status request) and LMI Status (status acknowledgement). And LMI Status (status acknowledgement). These messages are exchanged at regular intervals between the user DTE and the network. Approximately every 4th Status Inquiry, a Full LMI Status message is received from the carrier switch which provides a complete view of the current status of all PVCs (identified by their DLCI numbers).

#### LMI Sourcing

  This feature enables the unit to maintain limited LMI traffic communications during those occasions when the opposite interface port (DTE or network) becomes disabled. Sourcing will be activated on any operational interface (DTE or network) regardless as to whether it is used as the unit's management port since the primary purpose of sourcing is to keep the connected entity appraised of the operational status of each DLCI. Maintaining LMI communications, even of a restrictive nature, provides network managers with very important information concerning the status of the local/remote equipment and signal paths. This information can then be used to minimize the impact of losses on the network by enhancing diagnostic and corrective measures.
  Note: This feature assumes the FRAP or T-FRAP has been configured for Frame Relay, and that its LMI Inactivity Timeout value is greater than 0, meaning MI sourcing is active.
  The unit activates sourcing after it detects that LMI traffic has been exchanged between its DTE and DDS interface ports within the time interval specified by the LMI Inactive Time-out parameter setting. Once activated, the unit must "hunt" to determine which interface port can still support the exchange of LMI traffic. During the hunting phase of LMI sourcing, the unit may momentarily assume several LMI sourcing states. After the port has been identified, the FRAP or T-FRAP mimics the LMI inquiry/ response role of either a DCE device (carrier switch) or a DTE device (Router or FRAD) based on port responses (or lack of) received after issuing Status Inquiry messages.
  The six sourcing states that the FRAP or T-FRAP may activate are:
  • Pass through (green)
  • User-DTE (yellow)
  • Net-DTE (yellow)
  • User-DDS / T1 (yellow)
  • Net-DDS / T1 (yellow)
  • Disabled (blue)

#### Pass through

  This state represents the normal condition for LMI traffic exchange and is represented as green on the graphical display. LMI Sourcing has not be activated since LMI traffic has been detected passing through the unit within its inactive time-out period.
  Note: LMI traffic is subject to spoofing, depending upon the DLCI mode.

#### User-DTE

  The unit acts as a source of LMI Status Inquiry requests. This sourcing state, displayed as yellow, is activated once the unit identifies that: The DDS (Unit) traffic path has been disrupted and will not support LMI traffic exchanges. The equipment attached to its DTE port will respond to Status Inquiries, indicating the equipment off this port is configured as a Frame Relay DCE device. The unit assumes the role of a Frame Relay DTE device (Router or FRAD) by originating Status Inquiry messages. These inquiry messages are sent over the DTE port at the configured keep-alive timer rate. Status messages received in response to these Status Inquires indicate the activity state of each DLCI.

#### Net-DTE

  The unit acts as a source of LMI Status Responses. This sourcing state, displayed as yellow, is activated once the unit identifies that: The DDS (unit) traffic path has been disrupted and will not support LMI traffic exchanges. The equipment attached to its DTE port will not respond to Status Inquiries, indicating the equipment off this port is configured as a Frame Relay DTE device. The unit assumes the role of a Frame Relay DCE device (carrier switch) by responding to Status Inquiries received on the DTE port with Status messages. These messages are sent over the DTE port. If the unit is configured for Local DLCI management, the Status message indicates the inland management DLCI is active, but all other DLCIs are currently inactive.

#### User-DDS / TI

  The unit acts as a source of LMI Status Inquiry requests. This sourcing state, displayed as yellow, activates once the unit identifies that: The DTE traffic path has been disrupted and will not support LMI traffic exchanges. The equipment attached to its DTE port will not respond to Status Inquiries, indicating the equipment off this port is configured as a Frame Relay DTE device. The unit assumes the role of a Frame Relay DCE device (carrier switch ) by responding to Status Inquiries received on the DTE port with Status messages. These messages are sent over the DTE port. If the unit is configured for Local DLCI management, the Status message indicates the inland management DLCI is active, but all other DLCIs are currently inactive. User-DDS / T1 The unit acts as a source of LMI Status Inquiry requests. This sourcing state, displayed as yellow, activates once the unit identifies that: The DTE traffic path has been disrupted and will not support LMI traffic exchanges. The equipment attached to its DDS or T1 port will respond to Status Inquires, indicating the equipment off this port is configures as a Frame Relay DCE device. The unit assumes the role of a Frame Relay DTE device (Router or FRAUD) by originating Status Inquiry messages. These messages are sent over the DDS or T1 port at at the configured keep-alive timer rate. Status messages received in response to these messages indicate the activity state of each DLCI

#### Net-DDS / T1

  The unit acts as a source of LMI Status Responses. This sourcing state, displayed as yellow, is activated once the unit identifies that: The DTE (unit) traffic path has been disrupted and will not support LMI traffic exchanges. The equipment attached to its DDS or T1 port will not respond to Status Inquiries, indicating the equipment off this port is configures as a Frame Relay DTE device. The unit assumes the role of a Frame Relay DCE device (carrier switch) by responding to Status Inquiries received on the DDS OR T1 port with Status messages. These messages are sent over the DDS or T1 port. If the unit is configured for Local DLCI management, the Status message indicates the in-band management DLCI is active, but all other DLCIs are currently inactive.