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Selection Mechanism for Active Vs. Backup Processor

IP.com Disclosure Number: IPCOM000116975D
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 116K

Publishing Venue

IBM

Related People

Aureglia, JJ: AUTHOR [+5]

Abstract

Consider a System made of several I/O adapter cards which ports connect to workstations; these I/O adapter cards are all attached to a Common Bus to allow communications between all workstations, communications being established via switched connections. To establish these switched connections a microprocessor card and its dedicated software, called the active Control Point (CP) in this document, is also attached to that Common Bus to receive connection requests from the workstations, to set up routing tables in the I/O adapter cards and to manage these connections.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Selection Mechanism for Active Vs.  Backup Processor

      Consider a System made of several I/O adapter cards which ports
connect to workstations; these I/O adapter cards are all attached to
a Common Bus to allow communications between all workstations,
communications being established via switched connections.  To
establish these switched connections a microprocessor card and its
dedicated software, called the active Control Point (CP) in this
document, is also attached to that Common Bus to receive connection
requests from the workstations, to set up routing tables in the I/O
adapter cards and to manage these connections.

      In order to provide continuous operations, a redundant Control
Point card, called the backup CP, may be connected to the Common Bus
to maintain an image of all information regarding the connections
established by the active CP.  This will allow the backup CP to take
over non disruptively in case the active CP fails.

      Fig. 1 is a simplified view of the System described in this
introduction.

At least two problems need to be solved:
  1.  In case a redundant Control Point card is installed, the two
       Control Point cards being strictly identical and full-floating
on
       the Common Bus, i.e., no dedicated position being assigned for
       either card, some mechanism should be implemented to tell the
       Control Point software whether it should initialize itself as
       active or backup CP.
  2.  If the active CP software fails, the backup CP software should
be
       able to detect the failure and to reset and restart the
selection
       mechanism to become active.

Provided that the solution is as follows:

On the Common Bus, there is no dedicated position for any card.
Cards are hot-pluggable and can be plugged or unplugged without
requiring a general reset and a restart of the System.  Once plugged,
cards are only differentiated by their addresses.  Addresses are
assigned by wiring according to the card position on the Common Bus.

      The selection mechanism is implemented on the Control Point
cards and only uses the card address as input to select the active
Control Point card.  This is further described with respect to Fig. 2
and Fig. 3.

      The selection mechanism is capable of handling three different
situation into account the fact that cards are hot-pluggable and can
be plugged or unplugged at any time once the system has already
started.

General Power-On

All cards on the Common Bus are powered-on at the same time,
incl...