Run time configurable parameters
The kernel allows you to change many parameters at run time. If you take a careful look at the /proc/sys/net/ directory structure you will see many files with useful names that describe various parameters for the network configuration. The files in the /proc/sys/net/ax25/ directory each represent one configured AX.25 port. The name of the file relates to the name of the port.
The structure of the files in /proc/sys/net/ax25/portname/ is as follows:
| Filename | Meaning | Values | Default |
|---|---|---|---|
| ip_default_mode | IP Default Mode | 0=DG 1=VC | 0 |
| ax25_default_mode | AX.25 Default Mode | 0=Normal 1=Extended | 0 |
| backoff_type | Backoff | 0=Linear 1=Exponential | 1 |
| connect_mode | Connected Mode | 0=No 1=Yes | 1 |
| standard_window_size | Standard Window | 1 .. 7 | 2 |
| extended_window_size | Extended Window | 1 .. 63 | 32 |
| t1_timeout | T1 Timeout | 1s .. 30s | 10s |
| t2_timeout | T2 Timeout | 1s .. 20s | 3s |
| t3_timeout | T3 Timeout | 0s .. 3600s | 300s |
| idle_timeout | Idle Timeout | 0m or greater | 20m |
| maximum_retry_count | N2 | 1 .. 31 | 10 |
| maximum_packet_length | AX.25 Frame Length | 1 .. 512 | 256 |
In the table 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, e.g. T3 and Idle, a zero value indicates that the timer is disabled.
The structure of the files in /proc/sys/net/netrom/ is as follows:
| Filename | Meaning | Values | Default |
|---|---|---|---|
| default_path_quality | 10 | ||
| link_fails_count | 2 | ||
| network_ttl_initialiser | 16 | ||
| obsolescence_count_initialiser | 6 | ||
| routing_control | 1 | ||
| transport_acknowledge_delay | 50 | ||
| transport_busy_delay | 1800 | ||
| transport_maximum_tries | 3 | ||
| transport_requested_window_size | 4 | ||
| transport_timeout | 1200 |
The structure of the files in /proc/sys/net/rose/ is as follows:
| Filename | Meaning | Values | Default |
|---|---|---|---|
| acknowledge_hold_back_timeout | 50 | ||
| call_request_timeout | 2000 | ||
| clear_request_timeout | 1800 | ||
| link_fail_timeout | 1200 | ||
| maximum_virtual_circuits | 50 | ||
| reset_request_timeout | 1800 | ||
| restart_request_timeout | 1800 | ||
| routing_control | 1 | ||
| window_size | 3 |
To set a parameter all you need to do is write the desired value to the file itself, for example to check and set the ROSE window size you'd use something like:
# cat /proc/sys/net/rose/window_size
3
# echo 4 >/proc/sys/net/rose/window_size
# cat /proc/sys/net/rose/window_size
4
