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Browse Prior Art Database

Recognition/Correction of Endless Frame Repetition on an Enterprise System CONnection Interface

IP.com Disclosure Number: IPCOM000116714D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Hathorn, RG: AUTHOR [+2]

Abstract

Disclosed is a method for recognition and correction of potential endless repetition that may occur when conflicting request frames are encountered on an ESCON (Enterprise System CONnection) interface. A state machine monitors the first occurrence of conflicting request frames and changes it's behavior on the next occurrence.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 56% of the total text.

Recognition/Correction of Endless Frame Repetition on an Enterprise
System CONnection Interface

      Disclosed is a method for recognition and correction of
potential endless repetition that may occur when conflicting request
frames are encountered on an ESCON (Enterprise System CONnection)
interface.  A state machine monitors the first occurrence of
conflicting request frames and changes it's behavior on the next
occurrence.

      Conflicting request frames in a dynamic ESCON configuration can
cause endless repetition to occur at a link-level facility (the
control unit or channel interface to ESCON or an ESCON director
port).  Conflicting request frames means that one link-level facility
is initiating a connection on the interface at the same time as the
link-level facility receiving the request.

      The problem arises when the link-level facilities are connected
through an ESCON director (or dynamic switch).  Refer to the Figure
for the following discussion.  If one link-level facility (A) sends a
frame to another link-level facility (C) and receives an initiation
frame from yet another link-level facility (B), this is called a
three party loop.  When an ESCON director recognizes this condition,
the second connection request received at the switch is responded to
with a Switch Port Busy frame.  In this scenario, facility A will
receive a switch port busy frame.  If the required response to the
received initiation frame at facility A is to send a li...