6pack and EAX25 protocol

Re: 6pack and EAX25
Andreas Koensgen
Thu, 17 Jul 1997 10:59:11 +0200 (MET DST) 
On Wed, 16 Jul 1997, Rick Angell wrote:

> Hello everyone,
> I noticed some 6pack info with the ax25-doc file.
> Are the 6pack eproms compatible with the ax25 utilities?

Using a 6pack or KISS eprom is not a problem of the AX.25
utilities, but of the Linux kernel driver that controls a TNC attached
to a serial port. For KISS, a driver is delivered with the kernel
distribution, it can be selected when configuring the kernel. For 6pack,
I've written a Linux driver that is not yet part of the kernel
distribution (it doesn't run on 2.1.x kernels yet) but can be obtained
as a separate package.

> If they are, are
> they a better choice than a generic KISS chip? I've also seen several
> versions of KISS chips (KISS,JKISS, Acked KISS,etc), can anyone tell
> me which one is best to use?

The main differences between 6pack and generic KISS are:

- 6pack provides a checksum for each packet that is transferred over
the serial line and therefore is able to detect corrupt data.

- 6pack uses status bytes which signal certain conditions of the TNC,
for example, the state of the DCD or an overrun in the TNC's RX buffer.

- 6pack is able to control up to 7 TNCs over a single serial line.
However, this feature is not yet implemented in the Linux driver.

- 6pack starts to transmit data to be sent immediately after it has
received the first byte of the data packet from the PC. KISS starts
to transmit the data to the radio when the whole packet has been
received. This provides a faster response to polls from the digipeater,
which is especially useful in DAMA mode.

> Here is another question for the gurus on the list. I've seen some email
> to this list regarding EAX25. I've noticed that when a nearby BPQ station
> beacons, "listen" shows that its EAX25 instead of standard AX25. Is EAX25
> compatible with standard AX25? Whats the advantage of using it?

I don't know much about EAX25, but as far as I know, EAX25 uses 8-bit-wide
transmit and receive counters instead of 3-bit-wide used with AX.25.
So longer sequences of packets can be transmitted without requesting an
acknowledgement from the other stations.

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