Microsoft KB Archive/107192

= Multiple connections to the same host over 802.2 =

Article ID: 107192

Article Last Modified on 10/6/2004

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APPLIES TO


 * Microsoft SNA Server 2.0
 * Microsoft SNA Server 2.1
 * Microsoft SNA Server 3.0
 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0

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This article was previously published under Q107192



SUMMARY
SNA Server for Windows NT supports up to 250 connections (PUs) over a single SNA Server 802.2 link service, where each connection is communicating to a different IBM host, peer system (such as AS/400) or downstream (DSPU) device. However, to communicate to the same SNA destination, two SNA Server 802.2 link services and connections must be configured when using SNA Server 3.0 SP1 and earlier.



MORE INFORMATION
An SNA Server connection is equivalent to an IBM SNA Physical Unit Type 2.0 or 2.1. When communicating to different destinations (such as multiple 3745 and AS/400 computers), SNA Server supports up to 250 simultaneous connections over one 802.2 link service.

However, when communicating to the same destination (for example, to one 3745), two SNA Server 802.2 link services must be defined (each with it's own SAP address), and a separate 802.2 connection must be defined through the SNA Server Admin/Manager program to use each 802.2 link service. Note that multiple SNA Server 802.2 link services can operate over a single 802.2 adapter, though each link service must be configured with a unique SAP address.

SNA Server 2.x
To define two SNA Server 802.2 link services in the SNA Server Setup program, do the following:


 * 1) From the Setup Option dialog box, Select Configure Link Services.
 * 2) Select Add, then highlight SNA DLC 802.2 Link Service and choose Install.
 * 3) Enter a title describing the link service (or leave the default title), then select the adapter the link service will use.
 * 4) Leave the SAP default to 4
 * 5) Repeat the previous steps to add the second 802.2 Link Service, except in step 4, set the SAP value to 8.

To exit Setup, choose Continue repeatedly until Setup displays an option to exit or start SNA Admin.

SNA Server 3.0 and 3.0 SP1
To define two SNA Server 802.2 link services in the SNA Server Manager, do the following:
 * 1) From the Manager Menu Bar, Select Insert -> Link Service.
 * 2) Highlight DLC 802.2 Link Service and choose Add.
 * 3) Enter a title describing the link service (or leave the default title), then select the adapter the link service will use.
 * 4) Leave the SAP default to 4
 * 5) Repeat Steps 2 through 4 to add the second 802.2 Link Service, except in step 4, set the SAP value to 8.

To exit the Insert Link Service dialog, choose Finish.

SNA Server 3.0 SP2 and Later
SNA Server 3.0 SP2 added a Multi-SAP capability to the DLC 802.2 Link Service. This feature allows a single DLC 802.2 Link Service to use multiple Local SAP addresses. This allows the Local and Remote SAPs to be configured on a per connection basis. To add a DLC 802.2 Link Service using the Multi-SAP feature, do the following:
 * 1) From the Manager Menu Bar, Select Insert -> Link Service.
 * 2) Highlight DLC 802.2 Link Service and choose Add.
 * 3) Enter a title describing the link service (or leave the default title), then select the adapter the link service will use.
 * 4) Uncheck the "Use Fixed SAP" option. Note that the "Local Service Access Point (SAP)" option is now greyed out.

To exit the Insert Link Service dialog, choose Finish. To define an SNA Server 802.2 link service in the SNA Server Admin/Manager program, do the following:


 * 1) From the SNA Server Admin program, configure both connections with the appropriate Remote Network Address (which may be the same for both connections). Note that the Local Node ID will be unique for each connection, since each connection must refer to a unique PU at the host (where the Local Node ID must correspond with the IDBLK + IDNUM parameters on the PU definition in VTAM).

NOTE: If you are using the Multi-SAP feature of SNA Server 3.0 SP2 and later, the SAPs are configured on the same property page as the Remote Network Address. Each connection should be configured with a unique "Local SAP Address."

NOTE: VTAM also supports the configuration of a "CPNAME" (control point name) parameter in the PU definition. This control point name must match the local control point name in the "Server Properties" dialog in the SNA Admin program. SNA Server sends the local network name and control point name to the host in the XID Format 3 message during connection establishment. However, SNA Server 2.x only supports the configuration of a single local network name and control point name. If SNA Server is to support multiple connections (or PUs) to the same host system, and VTAM is configured with unique "CPNAME" parameters on each PU, the SNA Server local network name and control point name values in the server properties dialog must be left blank, and the Local Node ID configured on the connection dialog must be used to distinguish the PU to be used. So, in this configuration, VTAM must be configured with unique IDBLK and IDNUM parameters for each PU that SNA Server is to use.
 * 1) Add the required LUs (and optionally, LU pools) and save the configuration before restarting the SNA Server service.

SNA Server user/group records can be added after the SNA Server service has been started, though the configuration must be saved before these additions are available to the SNA Server client machine(s).

Additional query words: prodsna DLC 802.2 snafaq

Keywords: kbnetwork KB107192

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