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diff --git a/Documentation/networking/6pack.rst b/Documentation/networking/6pack.rst new file mode 100644 index 000000000000..bc5bf1f1a98f --- /dev/null +++ b/Documentation/networking/6pack.rst @@ -0,0 +1,191 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============== +6pack Protocol +============== + +This is the 6pack-mini-HOWTO, written by + +Andreas Könsgen DG3KQ + +:Internet: ajk@comnets.uni-bremen.de +:AMPR-net: dg3kq@db0pra.ampr.org +:AX.25: dg3kq@db0ach.#nrw.deu.eu + +Last update: April 7, 1998 + +1. What is 6pack, and what are the advantages to KISS? +====================================================== + +6pack is a transmission protocol for data exchange between the PC and +the TNC over a serial line. It can be used as an alternative to KISS. + +6pack has two major advantages: + +- The PC is given full control over the radio + channel. Special control data is exchanged between the PC and the TNC so + that the PC knows at any time if the TNC is receiving data, if a TNC + buffer underrun or overrun has occurred, if the PTT is + set and so on. This control data is processed at a higher priority than + normal data, so a data stream can be interrupted at any time to issue an + important event. This helps to improve the channel access and timing + algorithms as everything is computed in the PC. It would even be possible + to experiment with something completely different from the known CSMA and + DAMA channel access methods. + This kind of real-time control is especially important to supply several + TNCs that are connected between each other and the PC by a daisy chain + (however, this feature is not supported yet by the Linux 6pack driver). + +- Each packet transferred over the serial line is supplied with a checksum, + so it is easy to detect errors due to problems on the serial line. + Received packets that are corrupt are not passed on to the AX.25 layer. + Damaged packets that the TNC has received from the PC are not transmitted. + +More details about 6pack are described in the file 6pack.ps that is located +in the doc directory of the AX.25 utilities package. + +2. Who has developed the 6pack protocol? +======================================== + +The 6pack protocol has been developed by Ekki Plicht DF4OR, Henning Rech +DF9IC and Gunter Jost DK7WJ. A driver for 6pack, written by Gunter Jost and +Matthias Welwarsky DG2FEF, comes along with the PC version of FlexNet. +They have also written a firmware for TNCs to perform the 6pack +protocol (see section 4 below). + +3. Where can I get the latest version of 6pack for LinuX? +========================================================= + +At the moment, the 6pack stuff can obtained via anonymous ftp from +db0bm.automation.fh-aachen.de. In the directory /incoming/dg3kq, +there is a file named 6pack.tgz. + +4. Preparing the TNC for 6pack operation +======================================== + +To be able to use 6pack, a special firmware for the TNC is needed. The EPROM +of a newly bought TNC does not contain 6pack, so you will have to +program an EPROM yourself. The image file for 6pack EPROMs should be +available on any packet radio box where PC/FlexNet can be found. The name of +the file is 6pack.bin. This file is copyrighted and maintained by the FlexNet +team. It can be used under the terms of the license that comes along +with PC/FlexNet. Please do not ask me about the internals of this file as I +don't know anything about it. I used a textual description of the 6pack +protocol to program the Linux driver. + +TNCs contain a 64kByte EPROM, the lower half of which is used for +the firmware/KISS. The upper half is either empty or is sometimes +programmed with software called TAPR. In the latter case, the TNC +is supplied with a DIP switch so you can easily change between the +two systems. When programming a new EPROM, one of the systems is replaced +by 6pack. It is useful to replace TAPR, as this software is rarely used +nowadays. If your TNC is not equipped with the switch mentioned above, you +can build in one yourself that switches over the highest address pin +of the EPROM between HIGH and LOW level. After having inserted the new EPROM +and switched to 6pack, apply power to the TNC for a first test. The connect +and the status LED are lit for about a second if the firmware initialises +the TNC correctly. + +5. Building and installing the 6pack driver +=========================================== + +The driver has been tested with kernel version 2.1.90. Use with older +kernels may lead to a compilation error because the interface to a kernel +function has been changed in the 2.1.8x kernels. + +How to turn on 6pack support: +============================= + +- In the linux kernel configuration program, select the code maturity level + options menu and turn on the prompting for development drivers. + +- Select the amateur radio support menu and turn on the serial port 6pack + driver. + +- Compile and install the kernel and the modules. + +To use the driver, the kissattach program delivered with the AX.25 utilities +has to be modified. + +- Do a cd to the directory that holds the kissattach sources. Edit the + kissattach.c file. At the top, insert the following lines:: + + #ifndef N_6PACK + #define N_6PACK (N_AX25+1) + #endif + + Then find the line: + + int disc = N_AX25; + + and replace N_AX25 by N_6PACK. + +- Recompile kissattach. Rename it to spattach to avoid confusions. + +Installing the driver: +---------------------- + +- Do an insmod 6pack. Look at your /var/log/messages file to check if the + module has printed its initialization message. + +- Do a spattach as you would launch kissattach when starting a KISS port. + Check if the kernel prints the message '6pack: TNC found'. + +- From here, everything should work as if you were setting up a KISS port. + The only difference is that the network device that represents + the 6pack port is called sp instead of sl or ax. So, sp0 would be the + first 6pack port. + +Although the driver has been tested on various platforms, I still declare it +ALPHA. BE CAREFUL! Sync your disks before insmoding the 6pack module +and spattaching. Watch out if your computer behaves strangely. Read section +6 of this file about known problems. + +Note that the connect and status LEDs of the TNC are controlled in a +different way than they are when the TNC is used with PC/FlexNet. When using +FlexNet, the connect LED is on if there is a connection; the status LED is +on if there is data in the buffer of the PC's AX.25 engine that has to be +transmitted. Under Linux, the 6pack layer is beyond the AX.25 layer, +so the 6pack driver doesn't know anything about connects or data that +has not yet been transmitted. Therefore the LEDs are controlled +as they are in KISS mode: The connect LED is turned on if data is transferred +from the PC to the TNC over the serial line, the status LED if data is +sent to the PC. + +6. Known problems +================= + +When testing the driver with 2.0.3x kernels and +operating with data rates on the radio channel of 9600 Baud or higher, +the driver may, on certain systems, sometimes print the message '6pack: +bad checksum', which is due to data loss if the other station sends two +or more subsequent packets. I have been told that this is due to a problem +with the serial driver of 2.0.3x kernels. I don't know yet if the problem +still exists with 2.1.x kernels, as I have heard that the serial driver +code has been changed with 2.1.x. + +When shutting down the sp interface with ifconfig, the kernel crashes if +there is still an AX.25 connection left over which an IP connection was +running, even if that IP connection is already closed. The problem does not +occur when there is a bare AX.25 connection still running. I don't know if +this is a problem of the 6pack driver or something else in the kernel. + +The driver has been tested as a module, not yet as a kernel-builtin driver. + +The 6pack protocol supports daisy-chaining of TNCs in a token ring, which is +connected to one serial port of the PC. This feature is not implemented +and at least at the moment I won't be able to do it because I do not have +the opportunity to build a TNC daisy-chain and test it. + +Some of the comments in the source code are inaccurate. They are left from +the SLIP/KISS driver, from which the 6pack driver has been derived. +I haven't modified or removed them yet -- sorry! The code itself needs +some cleaning and optimizing. This will be done in a later release. + +If you encounter a bug or if you have a question or suggestion concerning the +driver, feel free to mail me, using the addresses given at the beginning of +this file. + +Have fun! + +Andreas |