X.25 Parameters

The following X.25 parameters are related to the IP interface. In most cases you will not need to modify the default values.

Listen Information

Called Address

Specifies the pattern of digits Solstice X.25 uses to match the called address on incoming calls for IP. The options are:

• Starts with: Solstice X.25 accepts calls from callers that have called addresses that have leading digits that match the string of hexadecimal digits you enter here.

• Matches: Solstice X.25 accepts calls from callers that have called addresses that exactly match the string of hexadecimal digits you enter here.

• Don't care: Solstice X.25 accepts calls from any caller, regardless of its called address.

If you choose Starts with or Matches, enter a string of digits to be matched.

Address Mapping

Choose between CCITT, DDN Basic and DDN Standard. These options are alternative ways of mapping between IP and X.25 addresses.

Call User Data

Specifies the pattern of digits Solstice X.25 uses to match the Call User Data on incoming calls for IP. X.25 software uses the first 2 digits of the call user data (CUD) field to distinguish between PAD and IP calls. The CUD field of a PAD call always begins with 01. The CUD field of an IP call always begins CC. If you want to add any further CUD to be used in outgoing PAD calls, make sure you append it to the 01. Do not delete the 01--if you do, the X.25 software receiving the call will not know which application to pass it to and the call will fail.

The options are:

• Starts with: Solstice X.25 accepts calls from callers that have CUD fields that have leading digits that match the string of hexadeciaml digits you enter here. The default of "Starts with" CC is the standard Call User Data value for IP over X.25 as specified in RFC 877.

• Matches: Solstice X.25 accepts calls from callers that have CUD fields that exactly match the string of hexadeciaml digits you enter here.

• Don't care: Solstice X.25 accepts calls from any caller, regardless of its CUD field.

If you choose Starts with or Matches, enter a string of hexadecimal digits to be matched.

Timers

Pre-emption Timer

This is the time in seconds that a connection must have been open before it can be closed (pre-empted). If all X.25 virtual circuits available to IP are in use and an IP packet arrives for transmission to a new destination, Solstice X.25 closes one of the existing connections--the one that has been idle the longest. The pre-emption timer determines the minimum time a connection must be open before it can be pre-empted in this way.

When setting this timer, take into account the amount of traffic on your link and the speed your link runs at. The default is suitable for links running at 9600 bps.

Hold Down Timer

The minimum amount of time, in seconds, to wait before re-trying a call to a host after an unsuccessful call.

Disconnection Timer

This is the time, in tenths of a second, that a connection to a given network can remain idle before being closed. This timer is configurable for each X.25 network to which you connect. When the disconnection timer expires, if there is no data on a connection, the virtual circuit to the X.25 network is closed. If data arrives from IP after this, the circuit is reopened.

When setting this timer, take into account the amount of traffic on your link and the speed your link runs at. The default is suitable for links running at 9600 bps.

Actions

Reset Action

The options are:

• Acknowledge and discard: Acknowledge Reset Request packet and discard it.

• Disconnect: Causes a Clear Request packet to be sent to remote host.

Expedited Data Action

For expedited data, the menu options are defined as follows:

• Acknowledge and discard: Acknowledge expedited data and discard it.

• Disconnect: Disconnect connection in response to expedited data.

• Reset connection: Reset connection in response to expedited data.

Accept Unknown Hosts

To restrict access, adding a measure of security, you can choose not to accept calls from unknown hosts, that is hosts who addresses are not in the Remote Host to X.25 Address Map.