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Combined Redundancy and Speed-Expansion Concept

IP.com Disclosure Number: IPCOM000106513D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 103K

Publishing Venue

IBM

Related People

Engbersen, A: AUTHOR [+2]

Abstract

In communication switches, one way of achieving continuous operation is by duplicating switch fabrics. The disadvantage of this is that there are resources provided in the system, e.g., switch cards and chips, which only come to function when another component fails. A significant amount of box cost can be saved when these 'redundant' resources are also used, and in case of failure, a graceful degradation can be achieved. In this invention, the port throughput of a switch fabric will be reduced when a failure occurs. It will be shown that with this method, continuous operation can be achieved at lower cost. Also, a simple way of cell resequencing and reassembly will be proposed.

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Combined Redundancy and Speed-Expansion Concept

      In communication switches, one way of achieving continuous
operation is by duplicating switch fabrics.  The disadvantage of this
is that there are resources provided in the system, e.g., switch
cards and chips, which only come to function when another component
fails.  A significant amount of box cost can be saved when these
'redundant' resources are also used, and in case of failure, a
graceful degradation can be achieved.  In this invention, the port
throughput of a switch fabric will be reduced when a failure occurs.
It will be shown that with this method, continuous operation can be
achieved at lower cost.  Also, a simple way of cell resequencing and
reassembly will be proposed.

      Building blocks for communication switch fabrics are very often
single switch fabric chips, which are then combined in some way to
obtain a higher port speed (speed expansion), a higher switch
performance, (performance-expansion), or a higher number of switch
ports (port- expansion).  These methods have been described e.g., in
[*].  Another requirement for these switch fabrics is
'non-interrupted' operation.  This means, when a single fault occurs,
the system continues operating, but may be at a lower
speed/performance:  graceful degradation.  Simply duplicating systems
is often not economically feasible, and ways to achieve temporary
graceful degradation (until a repair has been carried out) are
important to allow sufficient cost/ performance granularity.  Below,
a system configuration with a graceful degradation of port-speed is
described.

      Port speed expansion is achieved by either multiplexing
multiple bytes of cells over several switch-chips [*], or by
multiplexing cells over several switch chips in parallel (Figure).
In the latter case, due to cross-traffic from other sources, cells
can get out of sequence.

      The figure proposes a very simple scheme to switch cells.  The
switch chip provides each cell which passes with a unique Input Port
Identification (Id.), and the input adapter sequentially numbers
cells 0..255.  In the example configuration of the figure the RT.HDR1
of the cell generated by the input port adapter would have the value
'j' (the output port address), while the switch would replace this
RT.HDR1 with the value 'i', the...