IP over X.25

Solstice X.25 can route IP if you set up a mapping between IP and X.25 (X.121) addresses. In x25tool, the parameters for IP over X.25 configuration are divided into two windows: the IP Interface Configuration window and the Remote IP Host to X.25 Address Map. To access one of these windows, from the Services menu, click on IP and select either IP Interface or IP Mapping.

The parameter values are stored in the configuration files /etc/opt/SUNWconn/x25/ipconf and /etc/opt/SUNWconn/x25/ixemapconf.

IP Interface Configuration

Local IP address

Enter an IP address in either name or numeric form.

Point to

Choose between point-to-multipoint, or point-to-point.

IP Subnet Mask/Remote IP Address

For point to multipoint networks, this is "IP Subnet Mask"; for point-to-point networks, the item is "Remote IP Address".

For IP Subnet Mask: The mask number used in the specified IP network, expressed in IP dot notation. For example: 255.255.255.0, indicates a Class C subnetwork mask. Enter + to use the local default.

For Remote IP Address: The IP address, in name or numeric form, for the host at the remote end of the point-to-point connection.

MTU

This sets the maximum transmission unit size for the network service access point that the IP protocol will use to transmit data over X.25.

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Note -

The MTU value you set here must be smaller than the NSDU value specified under Packet Size in the Throughput window.

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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.

Remote IP Host to X.25 Address Map

Link Number

Enter a link number specifying the link over which you reach the IP network specified in the IP Subnet Mask/Remote IP Address.

Remote IP Address

The IP address of the remote IP host, in either hostname or numeric form.

Circuit is

Set to either SVC (switched virtual circuit) or PVC (permanent virtual circuit). If this parameter is set to SVC, you will need to include the remote X.25 address. If this parameter is set to PVC, you will need to set the PVC number.

Remote X.25 Address

The X.25 (X.121) address of the specified remote host. If you are attached to the DDN, the X.25 address is generated using the IP address. You do not need to enter it here, although if you do other information you enter can be taken into account. If you do want to enter the X.25 address, you need to calculate it in the same way as the DDN software.

Extended Address

If you are using extended addressing, choose either OSI or non-OSI. Otherwise, choose None.

Extension

If you are using extended addressing, enter the OSI NSAP address or non-OSI address extension. An OSI NSAP address is 40 or fewer hexadecimal digits.

X.25 Parameters for IP Mapping

Packet Size

The size of the X.25 packet that will carry IP datagrams. In accordance with RFC 877, when IP datagrams are longer than the X.25 packet size, Solstice X.25 uses the M-bit to transmit the datagrams as complete packet sequences. Fragmentation of IP datagrams occurs only if the size of an IP packet exceeds the maximum transmission unit (MTU) size for a given subnetwork.

Window Size

This parameter applies to calls in both directions and should not be larger than the window size value you specified for X.25.

Reverse Charge

Determines whether the software will request reverse charging when proposing calls to the remote host.

RPOA Numbers

A four-digit number that provides networks between you and the remote host with additional routing information. You can have up to four RPOA numbers. If you have multiple RPOA numbers, enter them together in the same sequence of digits, with no spaces between.

Closed User Group

CUG Type

Possible values are none, multi-user and bilateral CUG.

CUG Number

If your host is a member of a multi-user or bilateral CUG, enter the CUG number.