With the version of the AX.25, NET/ROM and Rose protocol stacks provided in
the Linux kernel from 2.1.9 onwards, a change has occurred in the
configuration of the protocols. With previous versions such changes were
made via ioctl calls, but now use is being made of the sysctl interface.

Each AX.25 device will be represented in the directory /proc/sys/net/ax25,
in the form "dev.parms"  where dev is the device name, eg ax0. In it are a
string of numbers that represent different values for the different
parameters, they are: 

No.	Name			Meaning				Default
1	IP Default Mode		0=DG 1=VC			0
2	AX.25 Default Mode	0=Normal 1=Extended		0
3	Allow Vanilla Connects	0=No 1=Yes			1
4	Backoff			0=Linear 1=Exponential		1
5	Connected Mode		0=No 1=Yes			1
6	Standard Window		1  <= N <= 7			2
7	Extended Window		1  <= N <= 63			32
8	T1 Timeout		1s <= N <= 30s			10s
9	T2 Timeout		1s <= N <= 20s			3s
10	T3 Timeout		0s <= N <= 3600s		300s
11	Idle Timeout		0m <= N				20m
12	N2			1  <= N <= 31			10
13	AX.25 MTU		1  <= N <= 512			256
14	Max Queue		1  <= N <= 20			2
15	Digipeater Mode		0=None 1=Inband 2=XBand 3=Both	3

In the above list T1, T2 and T3 are given in seconds, and the Idle Timeout
is given in minutes. But please note that the values used in the sysctl
interface are given in internal units where the time in seconds is
multiplied by 10, this allows resolution down to 1/10 of a second. With
timers that are allowed to be zero, eg T3 and Idle, a zero value indicates
that the timer is disabled. 

With NET/ROM and Rose protocol stacks, the entries in /proc/sys/net/netrom
and /proc/sys/net/rose are more obvious. Each file in these directories has
a name more in keeping with its function, and will not be explained in any
greater depth here. As with the AX.25 sysctl entries, timers operate with a
resolution of 100ms and so values should be written accordingly.

It is possible that the AX.25 sysctl interface will change in the future and
become more user friendly.

For more information about the AX.25 and NET/ROM protocol stacks, see the
AX25-HOWTO written by Terry Dawson <terry@perf.no.itg.telstra.com.au> who is
also the AX.25 Utilities maintainer.

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Jonathan G4KLX

jsn@cs.nott.ac.uk
