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Improved Congestion Control and Error Recovery on a Communications Bus

IP.com Disclosure Number: IPCOM000121362D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Bailey, WD: AUTHOR [+2]

Abstract

In this article, a single physical port on a communications bus appears as multiple logical ports, where each logical port is assigned to a system resource. This technique minimizes congestion by continuously servicing requests for uncongested resources. It also integrates the error recovery into the normal data flow and maintains proper data sequencing when the system is in error recovery.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 64% of the total text.

Improved Congestion Control and Error Recovery on a Communications Bus

      In this article, a single physical port on a
communications bus appears as multiple logical ports, where each
logical port is assigned to a system resource.  This technique
minimizes congestion by continuously servicing requests for
uncongested resources.  It also integrates the error recovery into
the normal data flow and maintains proper data sequencing when the
system is in error recovery.

      Fig. 1 illustrates the physical port with the resources defined
as the transmit buffer, the receive buffer, and a special events
register.  An interface tag exists for each resource indicating the
availability of the resource. Normal data operations are serviced in
a first-in, first-out queue-like manner.  If a particular resource is
not available, the queue is dynamically reordered so that a request
for the first available resource can be serviced. In this way, the
single physical port can service requests for a resource when one or
more other resources are congested.

      Fig. 2 illustrates a logical implementation of the dynamic
queuing.  The device on the communications bus constantly monitors
the interface tags (transmit buffer available, etc.) to determine the
resource availability.  It then generates a request for a data
operation and raises a signal to identify the type of request
(transmit operation, for example).  The bus request is then sent and
the appropriate resource i...