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Adaptive Polling Algorithm for PCS Connected to AS/400 ASCII Work Station Controller

IP.com Disclosure Number: IPCOM000119830D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 80K

Publishing Venue

IBM

Related People

Markson, KJ: AUTHOR [+3]

Abstract

Personal computers (PCs) that attach to the AS/400* through the ASCII Work Station Controller (WSC) and are using PC Support are using the 'SDLC' Protocol as their Data Link Control. This means that the ASCII Controller 'POLLS' the PCs with a 'Receive Ready' at intervals controlled by a Device Parameter (Normal Response Mode Poll Timer) on the AS/400.

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

Adaptive Polling Algorithm for PCS Connected to AS/400 ASCII Work
Station Controller

      Personal computers (PCs) that attach to the AS/400*
through the ASCII Work Station Controller (WSC) and are using PC
Support are using the 'SDLC' Protocol as their Data Link Control.
This means that the ASCII Controller 'POLLS' the PCs with a 'Receive
Ready' at intervals controlled by a Device Parameter (Normal Response
Mode Poll Timer) on the AS/400.

      This is fine for typical ASYNC Connected PCs (those that
connect either Directly to the ASCII Controller or through Dial Up
Switched Telephone Lines).  But there is a customer set out there
that wishes to use an X.25 Network as an intermediate Network between
the AS/400 and the PC.  In this environment, all those Receive Ready
Polls are going through the Network and costing the customer a lot of
money for unproductive data that is being sent through the Network.

      To solve the problem, we invented what we call Adaptive
Polling.  The ASCII Controller microcode will be changed so that it
can detect periods of multiple Receive Ready Exchanges between the
Controller and the PC.  When the Controller sees a consecutive number
of Non-Productive Polls exchanged between itself and a PC, it will go
into a SLOW POLL Mode.  It will start Polling the PC at time
intervals that are much greater than the Normal Response Mode Poll
Timer.  It will then continue to SLOW POLL the PC in this mode until
it sees useful data (an SDLC Frame carrying User Information).  Once
it sees useful data,...