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5.2 Defining Link Stations

To communicate with other nodes in an SNA network, you must configure the characteristics of a link station (LS) to an adjacent node in the SNA network. Before you can define a link station, you must define a port for the adapter (and link protocol) you are using. Most of the information needed to configure a link station is the same, whatever protocol is being used.

A link station represents the logical path through the SNA network between the SNAP-IX local node and a remote computer. The remote computer can be any of the following:

A link station is associated with a specific port; you can define one or more link stations on each port.

Each link station that supports dependent traffic has an associated PU (physical unit). Because PUs are associated with link stations, SNAP-IX does not treat them as separate resources; they are configured as part of link station configuration, and are started and stopped as part of starting and stopping link stations. Link stations are shown in the connectivity section of the Node window; PUs are not shown in any window.

Note

In most circumstances, you need to add a link station to the port. However, if you want to use a dynamically created link station for downstream PU concentration or for APPC traffic only, for situations in which the link is always activated from the remote node, you do not need to explicitly configure one.

If a remote node attempts to connect to the local node, but no link station is defined that matches the address specified on the incoming call, SNAP-IX can define one implicitly if a suitable port has been defined on the local node. This dynamically created link station appears in the connectivity section of the Node window for the duration of the connection.

To configure a link station, use one of the following methods:

Motif administration program

Select Connectivity and New link station from the Services menu on the Node window.

Command-line administration program

Issue the following command:

define_type_ls

In this command, type indicates the link protocol type (sdlc, tr, ethernet, qllc, channel, ip).

Advanced parameters for link stations provide additional control over transmission characteristics, XID exchange, optional link facilities, and reactivation procedures.

5.2.1 Link Station Configuration Parameters

In Motif, the Link Station Configuration dialog contains the following sections, each containing different categories of configuration parameters:

Link station

Use this area of the dialog to provide information that is required for all link stations, whether they support LU traffic for dependent LUs, independent LUs, or both. For descriptions of the parameters in this section, see Common Link Station Parameters.

Independent LU traffic

Provide this information only if you are using the link station for independent traffic. For descriptions of the parameters in this section, see Parameters for Independent LU Traffic.

Dependent LU traffic

Provide this information only if you are using the link station for dependent traffic. For descriptions of the parameters in this section, see Parameters for Dependent LU Traffic.

Common Link Station Parameters

The following parameters are required for all link stations, whether they support dependent traffic, independent traffic, or both.

For more information about the parameters on this dialog, refer to the online help or to SNAP-IX Administration Command Reference.

Name

A name to identify the link station locally.

SNA port name

The port that is to be used to access the adjacent node.

Activation

Method used to activate the link station. Specify one of the following methods:

By administrator

The link station is activated only on the request of a local System Administrator.

On node startup

The link station is started automatically when the node starts up.

On demand

The link station is started automatically when required to provide connectivity for an application.

Link stations are activated separately from ports, so the link station must be activated even if the port is already active. Activating the port does not itself activate any link stations, and configuring the port to be initially active does not mean that any of its link stations are activated automatically when the node starts up. However, activating a port does make it possible to activate link stations. A link station cannot be activated unless the ports are active on both the local node and the adjacent node.

If the link is one for which you are charged for usage, avoid activating the link unnecessarily, in order to keep the cost down.

If you are not sure how to set this field, consult your SNA network planner.

LU traffic

The type of LU traffic to flow over the link. This choice determines what other parameters are needed for link definition.

This parameter is not used for an Enterprise Extender (HPR/IP) link, because this link type supports only independent traffic.

Any

The link station can be used for both independent and dependent LU traffic. For this option, you must supply values for the fields described in Parameters for Independent LU Traffic and Parameters for Dependent LU Traffic, in addition to those described in this section.

Independent only

The link station can be used only for independent LU traffic. For this option, you must supply values for the fields described in Parameters for Independent LU Traffic, in addition to those described in this section.

Dependent only

The link station can be used only for dependent LU traffic. For this option, you must supply values for the fields described in Parameters for Dependent LU Traffic, in addition to those described in this section.

You also need to provide addressing information for contacting the adjacent node. The type of addressing information needed depends on the DLC type of the port. If you do not supply an address for the remote node, the link station acts as a nonselective listening link station, accepting incoming calls from any remote node.

Additional Link Station Parameters for SDLC

Poll address

The poll address of the remote station. Specify the address as a two-digit (one-byte) hex value, typically starting at C1. A primary link station polls the remote station using this value. A secondary link station responds to polling with this value. The poll address is entered differently depending on the link role:

  • If the link is a point-to-point link (not multi-drop), the address C1 is normally used.

  • If the parent port for this link is switched incoming, the poll address is configured on the port and cannot be configured independently for each link station.

  • If you are configuring a primary switched outgoing link station, and you do not know the poll address of the remote secondary with which you wish to communicate, you can specify a poll address of 0xFF on the primary. This value enables the node to accept responses from a secondary, regardless of the poll address it has configured. 0xFF is not a valid address for a nonprimary link or a link that is not switched outgoing.

  • If you are using a multi-drop configuration, all the secondary link stations that communicate with the same primary must have different poll addresses.

The poll addresses at both ends of the link must match. Contact your SNA network planner if you do not know the address configured at the remote system.

On a VTAM host, the poll address is configured as the ADDR= parameter in the VTAM PU definition.

On an AS/400 system, the poll address is the STNADR parameter of the Line Description.

Line encoding

The line encoding (NRZor NRZI) used on your SDLC line. If you set this incorrectly, you will find that the frames being received are all discarded and do not appear in any trace.

On a switched outgoing port, the line encoding can be set independently for each link station. For other types of ports, the line encoding setting is taken from the port, so this field does not apply.

Duplex setting

Specify Half Duplex or Full Duplex, depending on the capabilities of your SDLC cable and modems.

On a switched outgoing port, the duplex setting can be set independently for each link station. For other port types the duplex setting is configured on the port, so this field does not apply.

Dial string

An ASCII string to be sent to your modem in order to make it initiate the outgoing call. The dial string is required for a switched outgoing port. Refer to the documentation for your modem for more details. (Some modems do not support dial strings; in such cases, this field does not appear.)

For switched incoming ports, the dial string is configured on the port. For leased ports, this field does not apply.

For details of the format of the dial string, refer to your modem's documentation.

Additional Link Station Parameters for Token Ring and Ethernet

MAC address

The MAC address of the remote station, entered as a series of hexadecimal digits. The MAC address uniquely identifies the adapter card on the remote system.

If you do not know what value to use, consult your SNA network planner.

If the remote end of this link is a VTAM host, you can find its MAC address in the MACADDR= parameter of the VTAM Port definition.

If you are configuring a link to an AS/400 system, the MAC address is the ADPTADR parameter in the Line Description.

SAP number

The SAP number of the port on the remote computer. The SAP number distinguishes between different links using the same adapter card. This is a hex number, normally 04. It must be a multiple of 4.

If you do not know what value to use, consult your SNA network planner.

If the remote end of this link is a VTAM host, the SAP number is the SAPADDR= parameter of the VTAM PU definition.

If you are configuring a link to an AS/400 system, the SAP number is the SSAP parameter in the Line Description.

Additional Link Station Parameters for X.25 (QLLC)

Circuit type

Specify either Permanent virtual circuit or Switched virtual circuit to indicate whether the circuit is permanent or switched.

Channel ID

The channel ID that identifies the virtual circuit the link station is to use (only applicable for a permanent virtual circuit). Channel IDs are numbered from 1 up to a maximum of 4096. If you have only one permanent virtual circuit, its channel ID is likely to be 1.

Remote X.25 address

The DTE address of the remote DTE as a series of hexadecimal digits (only applicable if the circuit is a switched virtual circuit).

Link ID

The link identifier to be used by the link station, identifying the physical connection to the X.25 network (this is used to support multiple X.25 ports or multiple X.25 cards). Set this parameter to match the link identifier defined for your X.25 provider software (in the range 0- 255.

To indicate that the X.25 provider software should use its own internal routing information for the destination address to determine the correct physical link, set this field to 255. If no internal routing information is available for the destination address, the X.25 provider software uses the lowest numbered WAN link.

Additional Link Station Parameters for Channel

There are no additional link station parameters for Channel links.

Additional Link Station Parameters for Enterprise Extender (HPR/IP)

Remote IP host name

Remote host name of the destination node for this link. This can be specified as a dotted-decimal IP address (such as 193.1.11.100), as a name (such as newbox.this.co.uk), or as an alias (such as newbox). If you specify a name or alias, the Solaris system must be able to resolve this to a fully qualified name (either using the local TCP/IP configuration or using a Domain Name server).

Parameters for Independent LU Traffic

You need the following information to configure this link station for use by independent LUs (LUs of type 6.2 for use by APPC, 5250, or CPI-C applications):

Remote node name

The fully qualified CP name of the remote node.

If the remote system is a VTAM host, you can find the network name (the first eight characters of the fully qualified name) in the NETID parameter of the VTAM start list. The last eight characters are in the SSCPNAME parameter of the VTAM start list.

Note

If you enter the name of a new remote node, you can add a definition for the remote node to enable you to define partner LUs on the new remote node. If the local node is a LEN node, you do not need to specify the remote node type, and the Remote node type field does not apply.)

To define a new remote node in this way, specify the remote node type as a value other than Discover, as well as specifying the remote node name.

Alternatively, you can specify Discover and leave the remote node name empty. This means that any adjacent node can use the link station. The Discover option is not available if the local node is a LEN node.

Remote node type

The level of APPN support on the remote node that is accessed through this link station (only applicable if the local node is an end node or network node).

If you do not know whether the remote node is a LEN node or end node or whether it is a network node, you can choose Discover. Discovering the level of APPN support on the remote node can delay link activation slightly, so if you do know the type it is better to specify it. This also helps to ensure network configuration consistency.

You cannot choose Discover if the link station is activated on demand.

If the local node is a LEN node, this field does not apply.

Branch link type

The type of link to the remote node that is accessed through this link station (only applicable if the local node is a branch network node).

If the remote node is a network node within the main APPN backbone, choose Uplink (to backbone) . If the remote node is an end node within the branch, choose Downlink (within branch).

If the remote node is configured to be a network node, the branch link type is automatically set to Uplink (to backbone) and you cannot change it.

Parameters for Dependent LU Traffic

These parameters do not apply to an Enterprise Extender (HPR/IP) link, because this link type supports only independent traffic.

Configuring a link station for dependent LU traffic automatically creates an appropriate PU with the same name as the link station.

You need the following information to configure a link station for use by dependent LUs (LUs of type 0-3 for 3270, RJE, LU0, or LUA applications):

Local node ID

A value to identify the local node in the SNA network.

You can usually use the same node ID (the default value) for all the links on the same node. However, if you need more than 255 dependent LUs to access a specific host, you must configure multiple link stations to the host, each with up to 255 dependent LUs, and each with a different local node ID.

To ensure that the remote node is configured to recognize the local node ID, contact your SNA network planner.

In a VTAM configuration, the first three digits should match the IDBLK parameter in the PU definition, and the last five should match the IDNUM parameter.

On an AS/400 system, the node ID is configured in the EXCHID parameter.

Remote node ID

The node ID for the remote link station (optional; only applicable if you need to restrict access to this link station). If you specify the remote node ID, the link is activated only if the node ID of the remote node matches the value specified in this definition. This can be useful if you have several link stations configured on a switched port, because it enables the link stations to be distinguished when they are activated by the remote nodes. Link stations can also be distinguished by the CP name of the remote node, but for remote nodes that do not send their CP name when activating a link, the remote node ID must be used instead.

If you do not specify the remote node ID, the node ID of the remote node is not checked when the link is activated.

Remote node role

The role of the remote (adjacent) node:

Host

The link station supports dependent LUs (such as 3270 LUs) that are used for sessions with a host computer (the most common case). If the link is to a node that provides host connectivity using PU concentration or DLUR, the adjacent node role should still be set to Host, even though the link is not directly to a host computer.

Downstream (PU concentration)

The link station is to a downstream node that will communicate with a host using the PU concentration capabilities of the local node (to the host, the LUs on the downstream node appear to reside on the local node).

Downstream (DLUR)

The link station is to a downstream node that will communicate with a host using the DLUR capabilities of the local node. (To the host, the LUs on the downstream node appear to reside on the local node.)

Such links can be used only if the local node is an APPN network node.

This field is not used for Channel link stations.

Downstream PU name

The PU name associated with the downstream node. This value must match the PU name that is configured for the downstream node on the host computer. If you do not know the value to use for this name, consult your SNA network planner.

This field applies only if you specified that this link station is to a downstream PU that will communicate with a host using the DLUR capabilities of the local node. You can indicate this by specifying Downstream (DLUR) for the Remote node role field.

For more information, see Defining DLUR PUs.

Upstream DLUS name

The fully qualified LU name of the host LU that supports DLUS (the LU server that the downstream PU is to access). If you do not know the value to use for this name, consult your SNA network planner.

This field applies only if you specified that this link station is to a downstream PU that will communicate with a host using the DLUR capabilities of the local node. You can indicate this by specifying Downstream (DLUR) for the Remote node role field.

5.2.2 Additional Configuration

After performing the link station configuration, continue with the following configuration tasks:

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