SNA Server interoperability with Windows Load Balancing (231865)


The information in this article applies to:

  • Microsoft SNA Server 2.11
  • Microsoft SNA Server 2.11 SP1
  • Microsoft SNA Server 2.11 SP2
  • Microsoft SNA Server 3.0
  • Microsoft SNA Server 3.0 SP1
  • Microsoft SNA Server 3.0 SP2
  • Microsoft SNA Server 3.0 SP3
  • Microsoft SNA Server 4.0
  • Microsoft SNA Server 4.0 SP1
  • Microsoft SNA Server 4.0 SP2
  • Microsoft SNA Server 4.0 SP4
  • Microsoft Host Integration Server 2000
  • Microsoft Host Integration Server 2000 SP1
This article was previously published under Q231865

SUMMARY

Windows Load Balancing Server (WLBS) is a TCP/IP-based load-balancing solution that load balances incoming TCP/IP packets to all nodes in a cluster or a single node in a cluster. WLBS distributes the load across identical servers. All nodes in the cluster must be configured identically to provide the same system services.

You can configure WLBS to load balance on multiple servers filtered to use single affinity, no affinity, or Class C. SNA Servers can function in a WLBS environment configured for single affinity, however, it is not recommended. When configured for single affinity, all incoming packets using the WLBS virtual IP address are locked to a specific node in the WLBS cluster. Every packet that is sent from the client using the cluster IP address connects to that node. WLBS does not make any application routing decisions; all load-balancing rules are based on TCP/IP routing decisions.

MORE INFORMATION

SNA Server exhibits the following limitations:
  • SNA client's request for 3270 or APPC Logical Units (LUs) may not exist on the targeted SNA Server. SNA Server rejects the requested LU and cannot service the client's request.
  • SNA Server may not have any 3270 or APPC LUs available to service the SNA client-requested LU Pool.
  • SNA clients are not able to request a LU from another SNA Server when an SNA connection fails.
For these reasons, SNA clients should not use the Windows Load Balancing Server virtual IP address to connect to an SNA Server installed on a WLBS node configured for multiple hosts. This affects Microsoft SNA Server versions 2.11, 2.11 SP1, 2.11 SP2, 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, 4.0 SP1 and 4.0 SP2. SNA Server can take advantage of the native hot backup and load-balancing features as explained in the following Knowledge Base article:

128244 SNA Server load balancing and hot backup

Modification Type:MajorLast Reviewed:8/17/2004
Keywords:kbinfo KB231865 kbAudDeveloper
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