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Automatic Recovery of IBM Personal Computer Network Session

IP.com Disclosure Number: IPCOM000060298D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Pekowski, RP: AUTHOR

Abstract

A method is described for the IBM Personal Computer (PC) Network to recover when an IBM PC Network session becomes inactive for some reason. IBM PC Network SNA Emulation Program is a program product that provides 3270 emulation for PCs connected together on the IBM PC network. One PC acts as a "Gateway" to the host computer through an SNA/SDLC communications link. Other PCs, called Network Stations, are logically connected to "Gateway" through IBM PC Network sessions. An IBM PC Network session is a logical connection between two stations on the IBM PC Network. Conditions such as power off and ending the 3270 program cause the session to drop not only on the station on which they occur, but on the station that is logically connected to it as well.

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Automatic Recovery of IBM Personal Computer Network Session

A method is described for the IBM Personal Computer (PC) Network to recover when an IBM PC Network session becomes inactive for some reason. IBM PC Network SNA Emulation Program is a program product that provides 3270 emulation for PCs connected together on the IBM PC network. One PC acts as a "Gateway" to the host computer through an SNA/SDLC communications link. Other PCs, called Network Stations, are logically connected to "Gateway" through IBM PC Network sessions. An IBM PC Network session is a logical connection between two stations on the IBM PC Network. Conditions such as power off and ending the 3270 program cause the session to drop not only on the station on which they occur, but on the station that is logically connected to it as well. Furthermore, there is no action that can be taken solely at the station on which the condition occurs that will cause the session to be re-established. Software recovery is required at both stations. An IBM PC Network session is established when one station issues a call command and another station issues a listen command. Inherent in the network interface is that the call command (the command which initiates a session) will eventually time out if a session is not established within a specific period of time. This means that the programmer must decide which station should issue the call and thus time out. Software recovery is required at a station which could potentially time out. This type of error recovery in the network's software interface lends itself to programs with a similar type of operator interface. For example, consider a mail program where two stations are logically connected by an IBM PC Network session. If one station powers off, the station that remains powered on will get an error return code indicating that the session has dropped on the next message that it attempts to send. The easiest action for the program to take given the interface is to display an error message and terminate. The error recovery would be to restart the m...