Browse Prior Art Database

As/400 X.25 Line Selection Algorithm

IP.com Disclosure Number: IPCOM000120062D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 85K

Publishing Venue

IBM

Related People

Carlson, DG: AUTHOR [+4]

Abstract

AS/400* supports multiple X.25 network access points, referred to as lines in the remainder of this article. These lines may be either physically switched, for example, via a PSTN (Public Switched Telephone Network), etc., or leased. The user can construct a configuration which allows connectivity to a remote DTE (Data Terminal Equipment) using a SVC (Switched Virtual Circuit) over any of the multiple X.25 network access points (see the figure).

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This is the abbreviated version, containing approximately 52% of the total text.

As/400 X.25 Line Selection Algorithm

      AS/400* supports multiple X.25 network access points,
referred to as lines in the remainder of this article. These lines
may be either physically switched, for example, via a PSTN (Public
Switched Telephone Network), etc., or leased.  The user can construct
a configuration which allows connectivity to a remote DTE (Data
Terminal Equipment) using a SVC (Switched Virtual Circuit) over any
of the multiple X.25 network access points (see the figure).

      The selection of the line to establish the SVC, to the remote
DTE, can be controlled by user intervention. However, for systems
operating in an unattended environment, this selection proceeds
without user intervention.  The parameters used by the system for the
line selection process include the following:
-    A list of line candidates over which remote DTE connectivity may
be achieved.
-    The operational state of each line, e.g., not operational,
failed, undergoing recovery, etc.
-    The line type, i.e., leased versus switched, and for switched
whether the line is currently connected.
-    The method by which switched line dial failures, e.g., busy,
etc., should be handled, i.e., try next switched line (and number),
etc.
-    The switched line in the list having the most recent
unsuccessful dial operation attempt.

      Using the above parameters, the system chooses a line which can
support the new SVC and one incurring the least possible cost, e.g.,
leased or a connected switched line.

      As stated earlier, the algorithm first eliminates lines for
which there is no hope of connectivity, e.g., modem failure, not
activated, etc.  Then the algorithm performs selection based on the
line type, i.e., leased versus switched.  The cost of a leased line
is normally a fixed monthly charge.  Using additional SVCs on that
line type does not add to direct line costs.  (Additional charges may
be incurred...