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Q160849: INFO: How the SNA Server Client Chooses a "Sponsor" SNA Server

Article: Q160849
Product(s): Microsoft SNA Server
Version(s): 2.11,3.0,4.0
Operating System(s): 
Keyword(s): kbnetwork kbtshoot kbusage
Last Modified: 20-FEB-2002

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The information in this article applies to:

- Microsoft SNA Server, versions 2.11, 3.0, 4.0, on platform(s):
   - the operating system: Microsoft Windows NT 
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SUMMARY
=======

When the SNA Server client software initializes (Wnap.exe for Windows 3.x, or
Snabase.exe for Windows 95, Windows NT and MS-DOS), it opens a "sponsor"
connection to SnaBase running on an SNA Server in the subdomain. This article
describes how the SNA client locates a sponsor server.

NOTE: The order that computers running SNA Servers are tried for 3270, LUA or
LU6.2 sessions is not affected by the sponsor server chosen by the client. For
information about SNA Server load balancing and hot backup, see the following
Microsoft Knowledge Base article:

  Q128244 SNA Server Load Balancing and Hot Backup

MORE INFORMATION
================

The client locates a sponsor server as follows:

- If Named Pipes or TCP/IP is configured on the SNA client, and the client is
  configured as local to the server(s), the client sends a broadcast to the
  subdomain and waits for a response from a server-side SnaBase service. The
  first SnaBase to respond to the client's request will be tried for the
  sponsor connection.

  NOTE: If the server is located on a different TCP/IP subnet than the client,
  this broadcast is normally filtered by any intermediate IP routers separating
  the client and server. In this configuration, the remote connection method
  should be chosen during SNA client setup.

- If the SNA Server 2.11 Service Pack 1 (or later) client software is being
  used on Windows 3.x, Windows 95 or Windows NT, the client will randomly
  choose a server from this list. However, the SNA Windows 3.x and Windows NT
  clients (and the Windows 95 client, with an update to SNA Server 3.0
  post-SP1) can be configured to try servers in the order they're configured,
  by setting the RandomSponsor setting documented below. The MS-DOS client
  doesn't support TCP/IP sockets. When named pipes is chosen, the MS-DOS client
  tries the remote servers in order and never randomly chooses the sponsor
  server.

  NOTE: The SNA client Setup programs only prompt for two remote server names.
  To configure additional remote servers, they can be manually added for the
  Windows 3.x, Windows 95 and Windows NT clients as follows:

- Windows 3.x client: Add server names preceded with \\ on the Remote= line in
  the [WNAP] section of Win.ini, separating the server names with spaces. When
  connecting over TCP/IP, the server's IP address may be specified explicitly.
  For example:

  Remote= \\server1 \\server2 \\124.55.69.45

- Windows 95 client: add server names to the following registry value,
  separated by spaces, but *not* prepended with \\. For example:

  HKEY_LOCAL_MACHINE/Software/Microsoft/SnaBase/Parameters:
        Sponsors: server1 server2 server3

- Windows NT client: add server names to the following registry value (servers
  must be listed on separate lines):

  HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/ 
     SnaBase/Parameters
         Sponsors: REG_MULTI_SZ: server1
                                 server2
                                 server3

- If NetWare IPX/SPX is configured on the SNA client, and the client is
  configured as local to the server(s), the client queries the NetWare bindery
  based on the subdomain name entered during SNA client setup. The server-side
  SnaBase service automatically registers with the NetWare bindery, specifying
  the SNA subdomain name and a SAP service type of 0x444. The client retrieves
  all SNA Server computers from the bindery, and then randomly chooses a
  server.

- If NetWare IPX/SPX is configured on the SNA Windows 95 or Windows NT client,
  and the client is configured as remote to the server(s), the client queries
  the NetWare bindery looking for the specific server names specified during
  SNA client setup. The server names are stored in the registry as described
  earlier. The server-side SnaBase service automatically registers with the
  NetWare bindery and specify their subdomain name and a SAP service type of
  0x444. The client locates the servers in the bindery, and then randomly
  chooses a server.

  NOTE: When connecting over Banyan or NetWare IPX/SPX, the SNA Server Windows
  3.x client only supports local connection mode described earlier.

- If Banyan Vines is configured on the SNA Windows 95 or Windows NT client, the
  client queries the Banyan StreetTalk directory service based on the
  StreetTalk list name (that is, subdomain name) entered during SNA client
  setup. The server-side SnaBase service automatically registers with
  StreetTalk, creating a StreetTalk List based on the subdomain name, and a
  PC-based Service for each SNA Server. The client retrieves all SNA Server
  computers from the StreetTalk List, and then randomly chooses a server.

The sponsor connection must be successfully established before an SNA application
session (that is, 3270, LUA, APPC, CPIC, CSV, and so forth) will connect to an
SNA Server.

Background on the Sponsor Connection
------------------------------------

When the SNA Server client software initializes, it opens a "sponsor" (or
service) connection to the SnaBase service on an SNA Server in the subdomain.
The following functions are performed over this sponsor connection:

- The client is notified of SNA Server computers running in the subdomain.

- The server responds to various client requests, including requests for 3270
  user/group records.

- When connecting over TCP/IP sockets, NetWare IPX/SPX or Banyan Vines, the
  SnaBase service performs a Windows NT domain log on for the client.

- The client notifies the server of any autostarted invokable TPs that are
  registered on the client computer. The server sends dynamic load requests to
  the client when an attach request is received, if the invokable TP is
  configured on the client.

- The client reports errors to the server, to write to the Windows NT
  application event log.

The RandomSponsor Setting
-------------------------

The SNA Server 2.11 Service Pack 1 (or later) client software implements random
selection of a sponsor server if Named Pipes or TCP/IP is configured with the
remote option. The initial release of SNA Server 2.11 and previous versions of
the SNA client software will open remote sponsor servers in the order
configured.

By randomly choosing a sponsor server, the SNA Windows 3.x, Windows 95 and
Windows NT clients will tend to load balance across SNA Servers for their
sponsor connection to help distribute the load across servers.

The RandomSponsor setting can be configured for the Windows 95 client after
applying SNA Server 3.0 Service Pack 2. If this Service Pack is not applied,
remote sponsor servers are always tried in random order.

The RandomSponsor setting is enabled by default for Windows 3.x, Windows NT, and
Windows 95 clients but can be disabled through the following configuration
setting:

SNA Server Windows 95 Client:

If the SNA Server 3.0 Service Pack 2 Windows 95 client is applied, the following
entry may be set:

  HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/SnaBase/Parameters/ 
  RandomSponsor: 0

SNA Server Windows 3.x (or WFW) Client:

In the [WNAP] section of Win.ini:

  RandomSponsor = NO

SNA Server Windows NT Client:

  HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/SnaBase/Parameters/ 
  RandomSponsor: REG_DWORD: 0

The client SnaBase service must be restarted to implement this change.

Disabling the RandomSponsor setting causes the SNA client to try the remote
servers in the order they're configured.

Additional query words: snafaq

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Keywords          : kbnetwork kbtshoot kbusage 
Technology        : kbAudDeveloper kbSNAServSearch
Version           : :2.11,3.0,4.0
Issue type        : kbinfo

=============================================================================

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