1993-04-09 16:00:07 +04:00
|
|
|
/* Copyright (c) University of British Columbia, 1984 */
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
*
|
|
|
|
|
* X.25 HDLC DATA LINK LEVEL:
|
|
|
|
|
*
|
|
|
|
|
*
|
|
|
|
|
* This module implements the Link Level of the Open Systems Interconnect
|
|
|
|
|
* Model. The implementation is based on the ISO High-Level Data Link
|
|
|
|
|
* Control (HDLC). These procedures subscribe to the principles of the
|
|
|
|
|
* ISO-Class of Procedures for point-to-point. These procedures implement
|
|
|
|
|
* two-way asynchronous balanced mode (LAPB) as recommented by the CCITT.
|
|
|
|
|
*
|
|
|
|
|
* The HDLC protocol layer interface consists of the following procedures:
|
|
|
|
|
* Hd_init (pr_init)
|
|
|
|
|
* Hd_ouput (pr_output)
|
|
|
|
|
* Hd_input (pr_input)
|
|
|
|
|
* Hd_timer (pr_slowtimo)
|
|
|
|
|
*
|
|
|
|
|
* Note: Supervisory commands RR, RNR and REJ are not transmitted by this
|
|
|
|
|
* station.
|
|
|
|
|
*
|
|
|
|
|
* This station never enters a busy (RNR) condition.
|
|
|
|
|
*
|
|
|
|
|
* The "Generate_rr" variable can be set to FALSE. This means that
|
|
|
|
|
* we NEVER send an RR. This works just fine if the network level
|
|
|
|
|
* is X.25 packet protocol -- which it is.
|
|
|
|
|
*
|
|
|
|
|
* Currently, this is only a DTE implementation.
|
|
|
|
|
*
|
|
|
|
|
* Think about:
|
|
|
|
|
* If the remote is busy, no iframes are sent. The remote sends a RR
|
|
|
|
|
* to clear this condition. However, this RR may be damaged, causing
|
|
|
|
|
* a possible deadlock. A solution is to poll with iframe (P(S)==P(R)
|
|
|
|
|
* of RNR) indefinitly.
|
|
|
|
|
*
|
|
|
|
|
*
|
|
|
|
|
* Date: February 1984
|
|
|
|
|
*
|
|
|
|
|
* Author: Gerald W. Neufeld
|
|
|
|
|
*
|
|
|
|
|
* Installation: Department of Computer Science
|
|
|
|
|
* University of British Columbia
|
|
|
|
|
* Vancouver, BC, CANADA.
|
|
|
|
|
*
|
|
|
|
|
* History:
|
|
|
|
|
*
|
1993-05-20 08:12:01 +04:00
|
|
|
* $Id: README.hdlc,v 1.2 1993/05/20 04:12:01 cgd Exp $
|
1993-04-09 16:00:07 +04:00
|
|
|
*/
|
