Abstract:
The invention provides a method and system for auto-sensing LMI protocols in frame relay networks. When a router is first coupled to a frame relay network, it automatically configures the local management interface (LMI) to use one of a selected set of possible LMI protocols, by generating a set of protocol requests for a plurality of protocols, and by thereafter simultaneously listening for protocol responses from the configuration server. Multiple valid responses from the configuration server are assigned priority in response to which valid response is last to arrive.

Description:
This application is a continuation, pursuant to 35 U.S.C. Section 120, of prior U.S. Pat. application Ser. No. 09/140,178 entitled “AUTOSENSING LMI PROTOCOLS IN FRAME RELAY NETWORKS,” by Fowler et al., filed on Aug. 25, 1998, now U.S. Pat. No. 6,434,120 which is a continuation of U.S. Pat. Application Ser. No. 08/672,674 entitled “AUTOSENSING LMI PROTOCOLS IN FRAME RELAY NETWORKS,” by Fowler et al., filed on Jun. 28, 1996 now U.S. Pat. No. 5,802,042. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to autosensing LMI protocols in frame relay networks. 
   2. Description of Related Art 
   Frame relay networks include a number of remote stations, each coupled to another; one node may be designated as a server node. When the number of remote stations is large, or if the remote station is geographically remote, it can be difficult to assure that remote stations are properly configured for use with the network, due in part to lack of technical resources. One aspect of properly configuring the remote station is to assure that it uses the correct one of multiple possible protocols for the local management interface (LMI) for the connection between the remote station and an edge of the frame relay network at a frame relay switch; these possible protocols are called LMI protocols. 
   In one system for automated configuration of a remote station, the remote station attempts to communicate with frame relay network equipment using a series of LMI protocols, each tested in sequence. While this technique achieves the goal of sensing LMI protocols, it has the drawbacks of taking more time than necessary, and of predetermining an order for selection of an LMI protocol which may not ultimately be preferred. 
   Accordingly, it would be advantageous to provide an improved technique for autosensing LMI protocols in frame relay networks. 
   SUMMARY OF THE INVENTION 
   The invention provides a method and system for auto-sensing LMI protocols in frame relay networks. When a router (or other client process) is first coupled to a frame relay network, it automatically configures the local management interface (LMI) to use one of a selected set of possible LMI protocols, by generating a set of protocol requests for a plurality of protocols, and by thereafter simultaneously listening for protocol responses from the frame relay network equipment or switch. In a preferred embodiment, multiple valid responses from the frame relay network equipment are assigned priority in response to which valid response is last to arrive. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a method of autosensing LMI protocols in frame relay networks. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In the following description, a preferred embodiment of the invention is described with regard to preferred process steps and data structures. However, those skilled in the art would recognize, after perusal of this application, that embodiments of the invention may be implemented using a computer at each site operating under program control, and that modification of a set of general purpose computers to implement the process steps and data structures described herein would not require undue invention. 
   Autosensing LMI Protocols in Frame Relay Networks 
     FIG. 1  shows a method of autosensing LMI protocols in frame relay networks. 
   A method  100  of autosensing LMI protocols is performed in a frame relay network. 
   At a flow point  110 , a new router has been added to a frame relay network. 
   In a preferred embodiment this method is performed for a new router being added to a frame relay network and downloading configuration information from a configuration server on the frame relay network. However, in alternative embodiments, the method may be performed for any client process which is establishing or re-establishing contact with a server process. 
   At a step  121 , the router is powered up and attempts to contact the frame relay network equipment or switch. 
   At a step  122 , the router transmits a “STATUS ENQUIRY” message using a first LMI (local management interface) protocol. In a preferred embodiment, this first LMI protocol is the “ANSI” protocol, as described in “Integrated Services Digital Network (ISDN)—Signaling Specification for Frame Relay Bearer Service for Digital Subscriber Signaling System Number 1 (DSS 1 )”, ANSI Document T1.617-1991, Annex D, hereby incorporated by reference as if fully set forth herein. 
   At a step  123 , after transmitting the message, the router sets a timeout for a response to that message, and starts a timer interrupt to occur on that timeout. This timeout is preferably set for T391 seconds; the T391 timeout is described on page 75, table D.2, of ANSI Document T1.617-1991, and is preferably between about 5 to about 30 seconds, such as about 10 seconds. The router listens on LMI management channel number zero (0) for a response. 
   At a step  124 , the router transmits a “STATUS ENQUIRY” message using a second LMI (local management interface) protocol. In a preferred embodiment, this second LMI protocol is the “ITU” protocol, as described in “International Telegraph and Telephone Consultative Committee—Digital Subscriber Signaling System No. 1 (DSS1). Signaling Specification for Frame Mode Basic Call Control, CCITT Document Q.933, 1992, hereby incorporated by reference as if fully set forth herein. 
   At a step  125 , after transmitting the message, the router sets a timeout for a response to that message, and starts a timer interrupt to occur on that timeout. This timeout is preferably set for T391 seconds. The router listens on LMI management channel number zero (0) for a response. 
   At a step  126 , the router transmits a “STATUS ENQUIRY” message using a third LMI (local management interface) protocol. In a preferred embodiment, this third LMI protocol is the LMI protocol described in “Frame Relay Specification with Extensions—Based on Proposed T1S1 Standards”, Document Number 001-208966, Revision 1.0 (Sep. 18, 1990), sometimes called the “gang of four” protocol and herein called the “LMI” protocol, hereby incorporated by reference as if fully set forth herein. 
   At a step  127 , after transmitting the message, the router sets a timeout for a response to that message, and starts a timer interrupt to occur on that timeout. This timeout is preferably set for nT1 seconds; the nT1 timeout is described on page 6–12 of Document Number 001-208966, and is preferably between about 5 to about 30 seconds, such as about 10 seconds. The router listens on LMI management channel number  1023  for a response. 
   Although in a preferred embodiment the router transmits the “STATUS ENQUIRY” message using LMI protocols in the order described for the steps  122 ,  124 , and  126 , in alternative embodiments it would be possible to use a different order in which the messages are sent, a different number of LMI protocols to test, or a different set of LMI protocols for test. 
   Although in a preferred embodiment the timeouts are set for the values described for the steps  123 ,  125 , and  127 , in alternative embodiments it would be possible to use a different set of values for the timeouts. Moreover, although in a preferred embodiment the timeouts are set using multiple timer interrupts, in alternative embodiments it would be possible to use other techniques for setting and catching timeouts, such as a single timeout for all three messages, or a non-interrupt-based technique. 
   At a flow point  130 , the frame relay network equipment is ready to receive a “STATUS ENQUIRY” message, and the router is listening for responses to one or more of the “STATUS ENQUIRY” messages. 
   At a step  131 , the frame relay network equipment listens for a “STATUS ENQUIRY” message. The frame relay network equipment sets a timeout for receiving that message, and starts a timer interrupt to occur on that timeout. This timeout is preferably set for nT2 or T392 seconds (from the frame relay network equipment&#39;s perspective), such as about 15 seconds, as described in ANSI Document T1.617-1991 and in Document Number 001-208966. When the timeout occurs, the method continues at the flow point  140 . 
   At a step  132 , the frame relay network equipment receives one of the “STATUS ENQUIRY” messages. 
   At a step  133 , the frame relay network equipment determines if the received “STATUS ENQUIRY” message is for an LMI protocol it recognizes. If not, the frame relay network equipment continues to listen for a “STATUS ENQUIRY” message at the step  131 . In a preferred embodiment, the frame relay network equipment logs an error event if the received “STATUS ENQUIRY” message is for an LMI protocol which it does not recognize. 
   At a step  134 , the frame relay network equipment responds to the “STATUS ENQUIRY” message by transmitting a “STATUS” message on the appropriate LMI management channel. If the “STATUS ENQUIRY” message was for the ANSI protocol, the frame relay network equipment transmits the “STATUS” message on LMI management channel zero; if the “STATUS ENQUIRY” message was for the ITU protocol, the frame relay network equipment transmits the “STATUS” message on LMI management channel zero; if the “STATUS ENQUIRY” message was for the LMI protocol, the frame relay network equipment transmits the “STATUS” message on LMI management channel  1023 . 
   At a step  135 , the frame relay network equipment should further respond to the “STATUS ENQUIRY” message by configuring itself to use the LMI protocol associated with that message. In a preferred embodiment, the frame relay network equipment will so configure itself, but in the event it does not, the process begins again in an attempt to deliver the “STATUS ENQUIRY” message and cause the frame relay network equipment to so configure itself. 
   The frame relay network equipment then continues with the step  131  to receive any further “STATUS ENQUIRY” messages. 
   The steps  131  through  135  are performed in parallel with the steps  141  through  142 . 
   At a step  141 , the router receives a “STATUS” message for one of the LMI protocols. 
   At a step  142 , the router determines which LMI protocol the “STATUS” message is for, and configures itself for that LMI protocol. 
   The router then continues with the step  141  to receive any further “STATUS” messages. The router catches any timeout interrupts for the “STATUS ENQUIRY” messages transmitted in the steps  122 ,  124 , and  126 , until all “STATUS ENQUIRY” messages have been responded to or have timed out. Thereafter, the method proceeds at the flow point  150 . 
   At a flow point  150 , the frame relay network equipment has received at least one “STATUS ENQUIRY” message from the router, and the router has received at least one “STATUS” message in response thereto. 
   If the frame relay network equipment has only recognized one LMI protocol, it has responded to the “STATUS ENQUIRY” message for that LMI protocol only, and the router has therefore received only one “STATUS” message. The router and frame relay network equipment have therefore configured themselves for that one LMI protocol only. 
   If the frame relay network equipment has recognized more than one LMI protocol, it has responded to the “STATUS ENQUIRY” message for each of those LMI protocols, and has configured itself for each such LMI protocol in turn. Similarly, the router has received one “STATUS” message for each such LMI protocol, and has configured itself for each such LMI protocol in turn. The router and frame relay network equipment have therefore configured themselves for each LMI protocol seriatum; at the flow point  150  they are therefore configured for the same LMI protocol. 
   Although in a preferred embodiment, the router and frame relay network equipment mutually configure to the last LMI protocol which is mutually recognized, in alternative embodiments it would be possible for the router and frame relay network equipment to mutually configure to another mutually recognized. For example, the frame relay network equipment could respond to the first “STATUS ENQUIRY” message only, and reject all others; the router would then receive only one “STATUS” message in response, and the router and frame relay network equipment would mutually configure to the LMI protocol for that first “STATUS ENQUIRY” message. 
   The router and frame relay network equipment thereafter communicate using the selected LMI protocol. 
   ALTERNATIVE EMBODIMENTS 
   Although preferred embodiments are disclosed herein, many variations are possible which remain within the concept, scope, and spirit of the invention, and these variations would become clear to those skilled in the art after perusal of this application.