projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 15637ed4 RG |
1 | /* Copyright (c) University of British Columbia, 1984 */ |
| 2 | ||
| 3 | /* | |
| 4 | * | |
| 5 | * X.25 HDLC DATA LINK LEVEL: | |
| 6 | * | |
| 7 | * | |
| 8 | * This module implements the Link Level of the Open Systems Interconnect | |
| 9 | * Model. The implementation is based on the ISO High-Level Data Link | |
| 10 | * Control (HDLC). These procedures subscribe to the principles of the | |
| 11 | * ISO-Class of Procedures for point-to-point. These procedures implement | |
| 12 | * two-way asynchronous balanced mode (LAPB) as recommented by the CCITT. | |
| 13 | * | |
| 14 | * The HDLC protocol layer interface consists of the following procedures: | |
| 15 | * Hd_init (pr_init) | |
| 16 | * Hd_ouput (pr_output) | |
| 17 | * Hd_input (pr_input) | |
| 18 | * Hd_timer (pr_slowtimo) | |
| 19 | * | |
| 20 | * Note: Supervisory commands RR, RNR and REJ are not transmitted by this | |
| 21 | * station. | |
| 22 | * | |
| 23 | * This station never enters a busy (RNR) condition. | |
| 24 | * | |
| 25 | * The "Generate_rr" variable can be set to FALSE. This means that | |
| 26 | * we NEVER send an RR. This works just fine if the network level | |
| 27 | * is X.25 packet protocol -- which it is. | |
| 28 | * | |
| 29 | * Currently, this is only a DTE implementation. | |
| 30 | * | |
| 31 | * Think about: | |
| 32 | * If the remote is busy, no iframes are sent. The remote sends a RR | |
| 33 | * to clear this condition. However, this RR may be damaged, causing | |
| 34 | * a possible deadlock. A solution is to poll with iframe (P(S)==P(R) | |
| 35 | * of RNR) indefinitly. | |
| 36 | * | |
| 37 | * | |
| 38 | * Date: February 1984 | |
| 39 | * | |
| 40 | * Author: Gerald W. Neufeld | |
| 41 | * | |
| 42 | * Installation: Department of Computer Science | |
| 43 | * University of British Columbia | |
| 44 | * Vancouver, BC, CANADA. | |
| 45 | * | |
| 46 | * History: | |
| 47 | * | |
| 1cdffd64 | 48 | * $Id$ |
| 15637ed4 | 49 | */ |