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Is it possible to have a DLU Requester downstrwam of SNASw BrNN ?

Microsoft Host Integration Server 2003 lacks APPN

Virtual Node (aka Connection Network) functionality.

When LPAR1 is the Primary Network Node Server for HIS.

ALL sessions orginating or terminating in the HIS Server

will pass through Intermediate Routing Node LPAR1.

This solution will cause a lot of unnecessary Mainframe I/O

and usage cpu cycles. This APPN Network consist of some 30

APPN nodes as well as some 25000 sessions in prime time.

+------+ +-------+ +-------+

| | | | | |

| HIS | | LPAR1 | | LPAR2 |

| EN | <- EE -> | NN | <- EE -> | NN |

| DLUR | | DLUS | | |

| | | CDS | | |

+------+ +-------+ +-------+

To eliminate this perceived problem we propose to use the

SNASw Virtual Node capability. If this works no sessions

will run through LPAR1 between the HIS and LPAR2.

<------ Downlink ------> <------ Uplink ------>

VN

+------+ +--------------+ +-------+

| | | | | |

| HIS | | SNASw | | LPAR1 |

| EN | <- EE -> |.......+......| <- EE -> | NN |

| DLUR | | BrNN | EN | | DLUS |

| | | | DLUR | <- | CDS |

+------+ +--------------+ \ +-------+

\

EE +-------+

\ | |

\ | LPAR2 |

-> | NN |

| |

| |

+-------+

The above scheme results in the following

- All PU and LU of the HIS Server are registered with the

SNASw directory database.

- A APING from the Mainframe LPAR1/2 to the HIS Control

Point name will show a route containing the SNASw & HIS

nodes. Sometimes however the route will end with the SNASw.

- Session requests for 3270 LU (DLUR) always seem to arrive

at the destination LPAR, but the reversed path runs into

trouble with sense codes like 08060031, 08900037

AIW document :

APPN Branch Extender Archtecture Reference

6.8 Local Independent LUs and DLUR Support on BrNN

explicity states :

Support for DLUR is optional on a BrN, but DLUR is so

important that we can't imagine any Branch Extender product

leaving it out

The footnote on the same page states :

Without option sets 1116, 1122 and 1123, a DLUR downstream of

BrNN would be broken because the BrNN represents itself as the

ENCP owning all domain resources; therefore searches involving

a downlink DLUR with the Owning-CP-Respond indicator set would

not work right.

So does anyone know for sure that this is fully supported in the

SNASw or is it not allowed. SNASw Design and Implementation Guide

states : SNASw does not support DLUR routers cascaded downstream

from another DLUR.

The IBM DLUR/DLUS architecture (supported by SNASw) has a

restriction that if a DLUR is required, it can only be implemented

in the DLUR directly connected to the upstream DLUS NN server host.

THe above architecture reference is in conflicht with the AIW

document content. Please clarify.

1 REPLY
Cisco Employee

Re: Is it possible to have a DLU Requester downstrwam of SNASw B

DLURs cannot be cascaded beneath a Branch

Extender Node (BrNN). The BrNN architecture

reference does indicate that if the BrNN

supports option sets 1116, 1122 and 1123 that

this restriction can be overcome.

However, that is not correct. There are

unresolved problems with this type of

topology. Additional architectural

work would need to done for both the NNS(BrNN)

(aka VTAM) and in the BrNN (in this case

SNASwitch) to make this a reality.

SNASwitch has implemented those 3 APPN

option sets, but they are insufficient to

allow a DLUR to reside below a BrNN.

If there are any other questions please let

me know.

Also, IBM has a forum for APPN. It's on

news.software.ibm.com forum

ibm.networking.appn. That forum could be used

for any questions regarding VTAM's support and

other more general architectural issues such

as I've mentioned.

Thanks,

Ed Mazurek

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