Additional port parameters for SDLC

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 or NRZI 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.

Duplex Setting

Select Half Duplex or Full Duplex, depending on the capabilities of your SDLC cable and modems. If the modems at both ends are capable, choose Full Duplex for higher throughput.

For switched outgoing ports, you configure the line encoding and duplex settings on each link station (see Defining link stations) instead of on the port.

Physical link type

Indicate the type of modem, which can be one of the following:

• RS232D (EIA-232D, also known as V.24)
• EIA-422A
• V.35
• X.21
• Smartmodem (Hayes EIA-232D autodial protocol)
• V.25bis (V.25bis EIA autodial protocol)

Note: Some adapter cards do not support all the physical link types listed. Consult the documentation for your modem and adapter card for more details.

If you configure a switched incoming port with a physical link type of Smartmodem or V.25bis, 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.

For an explanation of the contents 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, or for ports using other physical link types, this field does not apply.

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