Echelon OpenLDV - Manual (Page 108)

100 Extending xDriver
Extending xDriver
The OpenLDV driver software includes the L ON W ORKS Interfaces application,
which you can use to create entries in the Windows Registry for each of your
RNIs. Each entry stores the lookup information that xDriver requires to connect
to one of your RNIs. The default xDriver lookup extension component supplies a
COM method that xDriver calls to retrieve this information from the Windows
Registry whenever an xDriver connection to an RNI is initiated. The information
is then used by xDriver to fully establish the connection.
If you plan to store information for many different RNIs (for example, more than
50), you can improve performance and scalability by using a database
management system (DBMS) to store this lookup information, rather than using
the Windows Registry. A DBMS provides higher capacity, reliable backup and
recovery, faster and more flexible database querying, and security. In addition, a
database can be shared by several computers, whereas the Windows Registry is
local to a single computer.
If you use a DBMS, you must:
• Replace the default xDriver implementation with a custom lookup
extension component. This custom component retrieves the information
that xDriver needs to initiate connections from the DBMS.
• Create an xDriver profile to use the custom lookup extension component.
An xDriver profile represents a set of configuration parameters that
determines how xDriver manages a given connection.
The following gsections describe how the lookup extension component and the
xDriver Session Control Object (SCO) interact when an xDriver connection is
initiated.
xDriver Sessions
An xDriver session involves a single connection between an RNI and an
OpenLDV application. A session begins when a request for connection from the
OpenLDV application to an RNI is made (a downlink session), or when a request
for connection from an RNI to the OpenLDV application is made (an uplink
session). When either request is made, xDriver creates a dedicated SCO for the
session. The SCO must be filled in by the xDriver lookup extension component
with the information that xDriver needs to establish the connection.
The following sections describe how the SCO is filled in, and how it is used to
initiate a connection.
Downlink Sessions
An xDriver session is considered a downlink session if the connection is initiated
by an OpenLDV application. The OpenLDV application accesses the RNI as
though it were opening any other type of network interface.
For an LNS client, if you use a custom lookup extension component, each RNI
only appears in the NetworkInterfaces collection object during a session that
involves that RNI. The network interface name to use is passed to LNS as part