Microsoft KB Archive/236105

= Maximum BTU limit for Dumb SDLC interface =

Article ID: 236105

Article Last Modified on 12/4/2007

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APPLIES TO


 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0
 * Microsoft SNA Server 3.0 Service Pack 2
 * Microsoft SNA Server 3.0 Service Pack 3
 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0
 * Microsoft SNA Server 4.0 Service Pack 1
 * Microsoft SNA Server 4.0 Service Pack 2
 * Microsoft SNA Server 4.0 Service Pack 3
 * Microsoft Host Integration Server 2000 Standard Edition
 * Microsoft Host Integration Server 2004 Standard Edition

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This article was previously published under Q236105



SUMMARY
When you use the IBM SDLC Dumb interface, the maximum BTU (Basic Transmission Unit) is 521 bytes. The IBM SDLC interface is provided by the Ibmsdlc.dll file. This dynamic link library is provided by Microsoft and only supports up to the 521-byte limit.

However, the maximum BTU length for an SDLC connection is dependent on the interface used by the link service of the SDLC adapter OEM (Original Equipment Manufacturer). Some adapters support up to 2,048 bytes for a BTU length. In these instances, the adapter manufacturer is not using the IBM SDLC Dumb interface (Ibmsdlc.dll) for the link service. The OEM is providing its own link service for this purpose as well as other features.



MORE INFORMATION
Even though the graphical user interface (GUI) allows for an entry above the 521-byte limit, this is not an indication of support beyond this limit. If such a limit were written into the GUI for MAX BTU, third-party developers would have to provide a unique solution to circumvent such a limitation. Therefore, there is no apparent limitation set by the GUI for MAX BTU.

