Browse Prior Art Database

User Header to Pass User-Control Information in RT/PC SNA Communication System

IP.com Disclosure Number: IPCOM000036057D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 4 page(s) / 61K

Publishing Venue

IBM

Related People

Chang, CM: AUTHOR [+4]

Abstract

Problem solved: This new invention allows application programs to send/receive user- control information independent of user-data in RT/PC SNA Communication environment. It reduces the burden of handling control information and user-data for an application program. Description of Invention:

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User Header to Pass User-Control Information in RT/PC SNA Communication System

Problem solved: This new invention allows application programs to send/receive user- control information independent of user-data in RT/PC SNA Communication environment. It reduces the burden of handling control information and user-data for an application program. Description of Invention:

A. Background: The traditional SNA message units consist of LH (Link Header), TH (Transmission Header), RH (Request/Response Header), and RU (Request/Response Unit). The RU was further divided into two parts, the SNA- Defined Data and End-User Data. The structure of this traditional message unit is shown below. The SNA-Defined Data part is used by the SNA system to control the operation of communication. The user does not see this SNA- Defined Data part in his or her application. The End-User Data part is the data sent and received by the application. In this RU format, the application can only use the End-User Data to handle both of its user-control information and user- data. In other words, the control information is treated just like regular data. The application program is required to add intelligence to differentiate its user-control information from user-data.

B. Description of Invention: The RT/PC SNA Communication Services assume the responsibility of handling the user-control information. The application program can concentrate on its user-data alone. In order for SNA Communication Services to handle the user- control information, the RU structure was divided into 3 parts: SNA-Defined Data, End-User Header, and End-User Data. The SNA- Defined Data has its traditional usage mentioned above. The End-User Header was used to pass user-control information, and the End-User Data was used to pass the user-data. By using this new RU format, user-control information can be treated differently from user-data, so SNA Communication Services can handle user-control information independent of user data. (Note: User-control information is the same as user header, and user- data is the same as application data.) The structure of RU format for RT/PC SNA Communication Services is shown below: This invention is realized via the SNA API interface, and the following sections describe how the end-user uses this invention.

When sending the user header, the user performs the following steps:
1. Allocates memory for the extended IO structure and user

header correctly (to use this invention, the extended

IO structure must be used):

ext_io_str is the extended IO structure as defined in

/usr/include luxsna.h

In this example, 64 bytes of user header will be sent.
2. Sets, the number of bytes for the user header; in this

case, 64 bytes are to be sent.

space.ext_io_str.usrhdr_len = 64;
3. Puts 64-byte user header in " space.user_header ".
4. Issues the SNA write command as follows:

writex (fd, buffer, length, &space);

1

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where fd = file descriptor

buffer = string of applicatio...