Browse Prior Art Database

LMI-FAST

IP.com Disclosure Number: IPCOM000009333D
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2002-Aug-16
Document File: 3 page(s) / 143K

Publishing Venue

Motorola

Related People

Enrico Penas: AUTHOR [+3]

Abstract

The iDEN Advanced Packet Duplicator (APD) uses the Local Management Interface (LMI) proto- col for link integrity verification between the APD and the frame relay switch the APD is connected to. Status of the LMI links between the APD and the switch influences the impaired availablility level (IAL) of the APD as reported to the iDEN Dispatch Application Processor (DAP). There are 2 APDs per a given DAP. The DAP chooses the APD which has the highest IAL of the APDs to service a given dispatch call. In the event of both APDs having the same IAL, the load of dispatch calls is shared equal- ly between the two APDs. For this reason, it is imperative that an APD report its IAL to the DAP as quickly as possible so the DAP can use this informa- tion to choose the highest rated APD to serve dis- patch calls.

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Page 1 of 3

Developments Technical 0 M MOTOROLA

LMI-FAST

by Enrico Penas, Karen Upp and Paul Erickson

BACKGROUND

  The iDEN Advanced Packet Duplicator (APD) uses the Local Management Interface (LMI) proto- col for link integrity verification between the APD and the frame relay switch the APD is connected to. Status of the LMI links between the APD and the switch influences the impaired availablility level (IAL) of the APD as reported to the iDEN Dispatch Application Processor (DAP). There are 2 APDs per a given DAP. The DAP chooses the APD which has the highest IAL of the APDs to service a given dispatch call. In the event of both APDs having the same IAL, the load of dispatch calls is shared equal- ly between the two APDs. For this reason, it is imperative that an APD report its IAL to the DAP as quickly as possible so the DAP can use this informa- tion to choose the highest rated APD to serve dis- patch calls.

  The current specifications for LMI (ANSI, ITU, and Frame Relay Consortium) describe a mecha- nism for the user equipment (the APD in this case) to "ping" the network (the frame relay switch) at a periodic polling interval (specified in LMI as T391). The Status Enquiry (SE) message is the "ping" and

the Status (S) response serves as the "ping" response. The user equipment sends SE at the beginning of T391 polling interval. If at the end of the polling interval, the user equipment has received a successful S message, then success is declared for that polling interval, otherwise, error is declared.

  The fully operational state is the state whereby customer frame relay traffic is processed and the user equipment - network link is active. The fully operational state will be refered to as "Fully@". If the user equipment link is not active (i.e. broken), then customer traffic is not processed, only LMI traffic. This state is referred to in LMI as service affecting hereafter referred to as "ServAtY. Given the user equipment is in a FullyGp state, the default requirement to enter ServAff is to have 3 error con- ditions (N392 counter in LMI) out of a sliding win- dow of the 4 most recent polling periods (N393 period in LMI). The default requirement to exit ServAff is to have 4 consecutive (N393) success conditions. The user equipment does not make a determination of whether a given polling interval resulted in error or success until at the end of the polling period.

0 Motomla,Ins. ,999 223 June 1999

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Page 2 of 3

Developments Technical 0 M MO7-OROLA

Entering ServAff

q

l tA T391 T391

Exiting ServAff

4 b ta T391 T391 - mT391

Fig. 1

PROBLEM

  In Figure 1, the error scenarios are indicated by "I?" and the successful scenarios are indicated by "S". If a line failure occured at point A, the APD (user equipment in this example) would not be able to determine a transition to ServAff until a duration: tA + (T391 * 2) has elapsed. Likewise, given the line was repaired at point B, the APD would not exit...