CSNW Sends Packets Greater Than Negotiated Maximum Packet Size

• Microsoft Windows NT Workstation versions 3.51 and 4.0
• Microsoft Windows NT Server versions 3.51 and 4.0

SYMPTOMS

Client Services for NetWare (CSNW) can send frames to a NetWare server that are bigger than the maximum allowed by the NetWare server. If the NetWare server has network card drivers installed that cannot cope with oversized frames, it can cause the NetWare server to Abend.

CAUSE

When CSNW establishes a session with a NetWare server, it uses the Large Internet Packet (LIP) protocol to negotiate the maximum frame size that can be used between the two computers. However, CSNW assumes that the size negotiated does not include the size of the IPX protocol header (30 bytes). Therefore, CSNW can send frames to the NetWare server that are up to 30 bytes bigger than the negotiated maximum frame size. In extreme cases, this can result in the NetWare server Abending, or in the normal case, it will result in a protracted renegotiation of the actual maximum frame size.

RESOLUTION

A fix has been produced that ensures that CSNW never sends frames greater than the frame size negotiated by the LIP protocol.

STATUS

Microsoft has confirmed this to be a problem in Windows NT versions 3.51 and 4.0. This problem was corrected in the latest Microsoft Windows NT 4.0 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K