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DG4FDI > BPQ 25.01.99 21:34l 90 Lines 4149 Bytes #-10130 (0) @ WW
BID : F64OENDG4FDI
Read: DL1MGV SP6VXT GUEST SQ9DHS
Subj: Re: Why is KISS obsolete ?
Path: DB0AAB<DB0ZKA<DB0ABH<DB0SRS<DB0ZDF
Sent: 990125/1831z @:DB0ZDF.#RPL.DEU.EU [ZDF Mainz JN49CX OP:DF4WJ] BCM1.40j
X-Info: User S&F received from DG4FDI at DB0ZDF.#RPL.DEU.EU
From: DG4FDI @ DG4FDI.DB0ZDF.#RPL.DEU.EU (Thomas)
To: BPQ @ WW
Hello !
KISS was only implemented as a quick hack get TCP/IP applications working
with the present TNCs and knowledge in 1985.
I know that there are some extensions to the standard KISS mode made since
that time, eg. checksum and polled kiss.
But they still have the basic disadvantages of KISS.
KISS encapsulates AX25 frames with KISS headers to transport them over
a RS-232 interface. There is no realtime data transfer between the radio port
and pc driver. The data flow consists of KISS (Keep It Simple and Stupid)
frames which are sent after corresponding AX25 frame has been completed.
The KISS driver knows nothing about the PTT status of the tnc or DCD of the
radio channel. The DCD/PTT/Channel free status information remains in TNC.
The driver has no influence on the PTT line.
This can be typical scenario when using KISS:
The driver puts three info frames in the transmit queue, each of 200 bytes.
The radio port is quite busy and the tnc has to wait until the frequency is
clear. In the meanwhile the driver's retry timer has reached the limit
and sends a poll frame to the tnc, even though the DCD of the TNC is on.
Unfortunately the DCD is no subject of KISS. The generation of more frames
is not suspended while the channel is busy.
When the channels is free the TNC sends all the accumulated frames such as
the three data frames and the (useless) poll frames in a single packet on the
air.
FRACK or T1 cannot be adjusted that fast as it is required.
Sometimes it is too low and somtimes too high.
BPQ and other KISS drivers base on estimations. The sysop has to estimate how
long your average transmission takes plus the period the receipient takes
for confirmation. This requires understanding the AX.25 protocol to follow
the monitor display and to judge to quality and timing of a connection.
Not a trival problem for the most packet users.
Or see what happens when a station sends seven info frames in a packet
to a recieving station with a kiss tnc.
You will at least see more then one ACK frame from the recipient.
Surely a waste of time.
Not to mention all the problems from the lack of a RS-232 CRC, which are
partly responsible for bulletin ID changes and corrupted messages.
6PACK provides realtime data exchange from the radio port of a tnc to the
driving software.
A CRC is standard in 6PACK.
Up to eight tncs can be connected to a single serial port w/o any multplexer
hardware.
A 6PACK TNC sends the DCD/PTT/Channel free status to the driver.
This enables the driver to have an exact channel access and adequate timing
to gain efficient radio channel use.
Flexnet makes use of the full transparency of 6PACK.
The driver has the full control over the tnc.
This is required for every software which works with adaptive paramters.
I regret that Kantronics do not sell their tncs with a 6pack firmware such
as the manufacturers of the TNC2 clones and the TNC3 do here in Europe.
6PACK takes only 4 kbytes in a TNC2 eprom.
The 6PACK specification is at HB9JNX's home page
http://www.ife.ee.ethz.ch/~sailer/ham/6pack.pdf
Are there any technical specifications of Kantronics TNC besides the
user manuals which are surely not enough to write a hardware depended
firmware ? Are such specifications free of charge ?
I don't think the Flexnet team can be made responsible
because any special hardware is not yet supported.
The TNC support is up to the manufacturer, esp. those making profits from
the sale of hardware.
Flexnet is a project brought to live by experienced enthusiasts
to improve the packet network within the resources a small non-profit
organization has. RMNC/Flexnet in Germany stands for performant Packet RADIO
network. The Authours surely have high demands on hardware and software,
which has to deal with the huge traffic here.
KISS was not chosen as TNC protocole because its disadvantages get the more
evident the more crowded a radio channel is.
Flexnet with a KISS tnc is step back, with a 6PACK tnc it is step forward.
73 de Thomas
DG4FDI@DB0ZDF.#RPL.DEU.EU
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