Browse Prior Art Database

Response Time Oriented Transmission Priority for APPN

IP.com Disclosure Number: IPCOM000121994D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 102K

Publishing Venue

IBM

Related People

Christenson, DA: AUTHOR

Abstract

A method to ensure good response time for high priority interactive jobs which share the same communications line with lower priority batch jobs, is disclosed. The flow of lower priority transmissions is increased and decreased based on the response time of high priority transmissions.

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

Response Time Oriented Transmission Priority for APPN

      A method to ensure good response time for high priority
interactive jobs which share the same communications line with lower
priority batch jobs, is disclosed.  The flow of lower priority
transmissions is increased and decreased based on the response time
of high priority transmissions.

      This invention has been applied to System Network Architecture
(SNA), but is applicable to other architectures, such as Open System
Interconnection (OSI). The SNA Path Control layer passes packets (DLC
frames) to the Data Link Control layer for transmission to the
adjacent system.  This invention deals with the pacing of packets
passed from the Path Control layer to the Data Link Control layer.

      The Path Control layer provides three different transmission
priorities:  high, medium and low.  Interactive jobs are typically
assigned high priority and batch jobs medium or low priority.

      An outstanding packet is defined to be a packet which has been
passed from the Path Control layer to the Data Link Control layer,
but has not been successfully delivered to the adjacent system.  The
medium/low limit (MLL) specifies the maximum number of outstanding
medium and low priority packets.  The overall limit (OL) specifies
the maximum number of outstanding high, medium and low priority
packets. OL is set to some fixed value which allows for efficient
transmission.  MLL is initially set to OL and is varied dynamically
based on the response time of each high priority packet.

      If MLL is reached, no more medium and low priority packets are
passed to the Data Link Control layer (even though OL may not have
been reached) until:
     -  an outstanding medium or low priority packet is successfully
delivered to the adjacent system by Data Link Control layer
     -  or MLL is increased.

      Response time is defined as the interval of time starting when
a high priority packet is passed from the Path Control layer to the
Data Link Control layer, and ending when the packet has been
successfully delivered to the adjacent system.  The response time is
categorized into the following ranges:
     -  VERY POOR - Greater than two seconds....