Darren,
you are mostly right, but a bit mixed up.
In SNA there are PU types and LU types.
The PU type describes the function/capabilities of the device within the SNA
hierarchy:
PU types:
5 VTAM (SSCP)
4 FEP
3 there is no PU type 3
2 3274/3174 cluster controller, 3777 RJE station, other devices (typically
connected to a FEP by a leased line running SDLC 1974-1980s) . Token ring SNA
gateway (1990s). SNA gateway on a LAN with a CISC router running DLSw to another
Cisco router on a token ring (1990s-). Any SNA gateway product running on a
server will be a PU type 2.
1 I've forgotten what that was.
then when peer to peer networking came into SNA:
2.1 APPN (advanced program to program networking) supports independant LUs.
Includes more recent 3174 etc cluster controllers.
The type of the LU describes what data stream it uses to communicate. ie the
format of the data sent from one LU to another.
LU types
new-fangled ones:
6.1 application to application CICS - not used much
6.2 application to application (APPC)
classic ones:
3 printer attached to a 3174 cluster controller using 3270 data stream
2 3270 display terminal (3278, 3179 etc) your basic "green screen", or
emulation of one on a PC
1 SNA character set - printer or RJE station
0 content of data stream not specified (this was used for program to program
communication before APPC/APPN came in eg Solve:Netmaster INMC, an Aussie
product)
SLU :
in classical SNA a session is between two LUs. One of the LUs is the Primary
(PLU), the other the Secondary (SLU). The primary LU is the application on the
mainframe, such as CICS, TSO etc. The secondary LU is the user's terminal.
Hope this isn't too overwhelming and it helps. Feel free to ask more questions!
Jenny
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Question for all:
In the SNA hierarchy there are defined types 5,4,2 and 1 nodes.
>From what I've read so far I've assembled the following:
Type 5 IBM Mainframe (Runs VTAM) SSCP
& PU5
Type 4 3705/3725/3745/3746 FEP/Communications Controllers PU4
Type 2 3174 Cluster Controller PU2
Type 2 Token Ring SNA Gateway PU2
Type 1 Token Ring Device LU
Type 1 TN3270 Terminals SLU
Type 5 & 2 Cisco Router acting as DSPU Concentrator PU5
& PU2
Is this anywhere near close?
Does an ethernet client running a TN3270 session also appear as an SLU
or LU?
Sorry if this is basic but SNA is the area that I am definately weakest
and while I can configure up basic DLSW+ services I prefer to understand
the underlying principles.
Darren
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