Defining Ports, DLCs, and Connection Networks

A port represents the local end of a communications link as a unique access point in the network. Each port is associated with a specific link protocol, which can be any of the following:

SDLC
Token ring
Ethernet
FDDI
X.25 or QLLC (qualified logical link control)

You can configure more than one port that uses a particular link protocol. In general, a port corresponds to a single physical access point such as an adapter card, but some link protocols (such as token ring) enable you to define multiple ports for a single adapter. The different ports are distinguished by addresses (such as the SAP number).

When you use the Motif administration program to define a port for a particular link protocol, SNAplus2 automatically defines a DLC for the port if a DLC of that type has not already been defined. For command-line configuration, you must define the port and DLC using different commands.

In an APPN network using token ring, Ethernet, or FDDI link protocols, you can also use the SAP Configuration dialog to indicate that the port is part of a connection network.

If you are using PU concentration, you can define a template that is used to generate definitions for implicit link stations (link stations that are not explicitly configured). Implicit link stations can support downstream LUs. If implicit PU fields are modified while the port is active, the changes affect any implicit link station instances generated after the change.

To configure a port, connection network, and DLC, use one of the following methods:

Motif administration program

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

Command-line administration program

To configure a port:

define_type_port

To configure a DLC:

define_type_dlc

In these commands, type indicates the link protocol type (sdlc, tr, ethernet, fddi, qllc).

To configure a connection network:

define_cn

Advanced port configuration parameters provide control over BTU size, the number of active links permitted, generation of implicit downstream LUs, and settings for dynamic link stations.

Port, Connection Network, and DLC Configuration Parameters

The following parameters are required for port configuration. (When you use the Motif administration program, port configuration also supplies information about the DLC and enables you to assign a port to a connection network.)

SNA port name

The locally known name of the port.

Adapter card number

A number that identifies the adapter card to use, if you have more than one card of the same type in this computer. If you have only one card, leave this as 0.

If you have more than one, the card in the lowest numbered slot is Card 0, the second card of this type is Card 1, the third is Card 2, and so on for any subsequent cards of the same type.

Port number

The number of the port to be used, if the adapter card can support more than one port. The range of valid port numbers is from 0 to the number of ports supported by the adapter card minus one. For the first port on the adapter card, enter 0.

This field applies only if the adapter card can support more than one port.

This field is not used for SDLC or QLLC ports.

Initially active

Whether to activate the port automatically when the node is started. This setting enables link stations that use the port to be activated in response to requests from adjacent nodes or on demand by the local node. (Activating the port does not activate any link stations; link stations are activated separately.)

Additional Port Parameters for SDLC

Line details

The following parameters describe the type of SDLC connection:

Type

Select one of the following values:

Leased Line

A dedicated line is used for the SDLC link between this computer and the remote system.

Switched incoming

The standard telephone network is used for incoming calls.

For a nonprimary port (as indicated by the Link role field), you also need to configure the poll address (for outgoing calls, that address is configured on the link station). The poll address is a one-byte address (C1 by default) that needs to match the poll address configured at the remote link station. When active, the port responds to frames sent with this poll address.

For a primary port, you do not need to configure a poll address; the port uses the poll address specified by the remote link station on the incoming call. For other types of ports, the poll address is configured on each link station.

Switched outgoing

The standard telephone network is used for outgoing calls.

Link role

Select a value that describes the role of the local node for link stations defined on this port. In SDLC communication, one end manages the link and is called the primary link station. The other end is the secondary link station.

Use one of the following values for this field:

Secondary

The other end of the link is to be the controller and the remote system is configured to be primary. This is nearly always the case if you are configuring a link to a host system.

Primary

This port is to act as the SDLC controller of the link, and the remote system is configured to be secondary.

Negotiable

For maximum flexibility, this setting enables the two ends to negotiate which end performs the primary role. Choose this value if you do not know which role is configured for the remote system.

You can use this setting for a peer link, but be aware that negotiating the role causes a short delay when the link is activated.

Primary Multi-drop

The link is leased and this port is to act as controller of a multi-drop link to several secondary nodes.

Use this setting when you want to configure several link stations from the local node to different remote nodes (for example, for links to downstream nodes). Each of these other nodes must be configured as secondary, and you must be using a leased line.

Secondary Multi-PU

The local port is one of the secondary stations on a multi-drop link controlled by the port on the remote system.

If you configure a port for a switched incoming or leased line, you also need to configure the following items:

Encoding

Select NRZ (typically used in the U.S.) or NRZI (typically used in Europe) for the encoding used on your SDLC line.

This value must match the encoding scheme used by the modem at the remote end of the link. If you set this field incorrectly, you will find that the frames being received are all discarded and do not appear in any trace.

On a VTAM host, this is the NRZI= setting in the LINE/GROUP definition.

For switched outgoing ports, you configure the line encoding on each link station (see “Defining Link Stations”) instead of on the port.

On some platforms, if you configure a switched incoming port, you need to configure the following:

Dial string

An ASCII string to be sent to your modem in order to prepare it to accept incoming calls.

By default, the dial string is sent to the modem at the rate of 1200 bits per second (the default baud rate) using asynchronous communications. You can match the baud rate to the modem's baud rate by placing one of the following numbers, enclosed by parentheses, in front of the dial string:

1 (300 baud)
2 (600 baud)
3 (1200 baud)
4 (2400 baud)
5 (4800 baud)
6 (9600 baud)
7 (19200 baud)

For example, you can specify a 9600 baud rate dial string by entering (6), as follows:

(6)AT &&D3 &&Q1 DT7,012345678

For an explanation of the rest of the dial string, refer to your modem's documentation.

For switched outgoing ports, the dial string is configured on each link station. For leased ports, this field does not apply.

Consult your SNA network planner if you do not know how to configure any of these parameters.

Additional Port Parameters for Token Ring, FDDI and Ethernet

Local SAP number

The address of the SAP, usually 04. Use a different value only if you need to use more than one SAP on the card.

The SAP number must be a multiple of 4.

If you do not know what value to enter for this field, contact your SNA network planner.

Define on connection network

Whether the SAP is to access the LAN as a connection network. Defining a connection network enables links between nodes on the connection network to be started dynamically, without prior configuration.

This field applies only if the local node is not a LEN node, because LEN nodes cannot use connection networks.

CN name

The name of the connection network. You do not need to enter the CN name unless you specified the Define on connection network option to define the SAP on a connection network. The CN name is used as the name of a virtual routing node in order to establish links between the nodes on the connection network.

Specify the same CN name on all nodes on the connection network.

Additional Port Parameters for X.25 (QLLC)

Match incoming X.25 address

The link address of the remote station (only needed if you want to restrict incoming data traffic). For a SpiderX25 port, you can configure an incoming match address. If you supply this value, incoming call packets are accepted only if they specify an address that starts with the configured address.




	NOTE: The underlying stack is also configured with an address and accepts only calls that specify an address starting with the configured address. Any address configured on the port must start with the address configured on the stack; otherwise, calls accepted by the stack are subsequently rejected by the port.

Additional Port Parameters for Implicit PU Concentration

Maximum active template instances: Specify the maximum number of link station instances to be generated from the template.
Configure downstream LUs for implicit PU access: Whether to configure downstream LUs that use this PU (see “Configuring PU Concentration”).

Additional Configuration

After performing the port configuration, continue with the following configuration tasks:

To define a link station on a port you have configured, see “Defining Link Stations”.
To define a DLUR PU, see “Defining DLUR PUs”.
To support APPC communication, see Chapter 7 “Configuring APPC Communication”