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PLU-SLU Session
This section describes how to initiate and terminate LU-LU sessions.
Initiating an LU-LU Session
Four types of LU-LU sessions are supported by the 3708:
Type 1 (LU type 1 SCS)
The device attached to the 3708 is defined to the 3708 as
a printer and the data stream is controlled by SNA
character string (SCS) characters. The 3708 is operating
in protocol conversion mode.
Type 1 (LU type 1 NTO) The device attached to the 3708 is operating as a TWX
33/35 NTO device and is defined to the 3708 as either a
keyboard/display or a keyboard/printer. The 3708 is
operating in protocol enveloping mode.
Type 2 (LU type 2)
The device attached to the 3708 is defined as a
keyboard/display, and the data stream is 3270. The 3708
is operating in protocol conversion mode.
Type 3 (LU type 3)
The device attached to the 3708 is defined as a printer
and the data stream is controlled by 3270 data stream
compatibility (DSC) mode format. The 3708 is operating
in protocol conversion mode.
The SNA BIND command (byte 14) is used to differentiate between type 1,2, or 3
sessions. If a type I BIND is received, LU type I SCS and LU type I NTO are
differentiated by the device type defined to the 3708. For a display, the mode
selection of Dynamic allows it to operate as LU type 1 NTO or LU type 2
depending on the SNA BIND byte 14.
The manner in which an LU-LV session may be initiated depends on the type of
session being started:
• An LV type 1 SCS or LV type 3 DSC session must be initiated by the PLV.
Both of these session types support printers only. Printers cannot initiate
sessions.
• An LU type 2 session may be initiated by either the PLV or SLU.
The LU type 2 session supports keyboard displays. Sessions can be initiated by
the terminal operator or from simulated logon procedures defined at the host.
• An LU type 1 NTO session may be initiated by either the PLU or SLU.
The LV type 1 NTO session supports both keyboard displays and keyboard
printers. Sessions can be initiated by the terminal operator or from simulated
logon procedures defined at the host.
Chapter 3. SDLC and SNA Communication
3-9
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