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PM58576: TN3270E CLIENTS HANG WHEN VTAM BIND SPLIT OVER TWO MESSAGES

A fix is available

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APAR status

  • Closed as program error.

Error description

  • A Telnet client using TN3270E logs on to a VTAM application.
    The VTAM application sends a BIND to the client which contains a
    x'FF' in the data.  Telnet must add a x'FF' to the data.  Telnet
    will split the bind into two messages.  This can cause the data
    to be sent as two packets to the Telent client.  Some Telnet
    clients can not handle the VTAM bind being split over two
    packets and will hang or present a black screen.
    .
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of the IBM Communications Server   *
    *                 for z/OS Version 1 Release(s) 12 and 13 IP:  *
    *                 Telnet facilities.                           *
    ****************************************************************
    * PROBLEM DESCRIPTION: Client emulation software does not      *
    *                      properly process an application         *
    *                      BIND which is split into multiple       *
    *                      packets.                                *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    The problem may be summarized as follows:
    
    1. A TN3270E client connected to the Telnet server and
       logged on to a target host application.
    
    2. As part of the session establishment process, the host
       application sent a BIND to the Telnet server.  The user
       data portion of the BIND image contained a x'FF' byte.
       Telnet server processing of the BIND image converted
       the x'FF' to a x'FFFF'.  This process is denoted as
       'IAC stuffing' and occurs so the client can distinguish
       a x'FF' in the application data from an IAC.
    
    3. The IAC stuffing caused the BIND image to be sent to
       the client in multiple packets.  The client emulation
       software was unable to correctly process the BIND in
       multiple packets, and the first data panel from the host
       application was not displayed.
    +-------------------------------------------------------------+
    + Please check our Communications Server for OS/390 homepages +
    + for common networking tips and fixes.  The URL for these    +
    + homepages can be found in Informational APAR II11334.       +
    +-------------------------------------------------------------+
    

Problem conclusion

  • The following modules have been amended to perform
    IAC stuffing (converting a x'FF' to a x'FFFF')
    in the same message triple (SKMB) when a BIND
    image is being processed:
    
     - EZBTPSTF
     - EZBTPCCO
     - EZBTPLMO
     - EZBTRTFO
    
    * Cross Reference between External and Internal Names
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM58576

  • Reported component name

    TCP/IP V3 MVS

  • Reported component ID

    5655HAL00

  • Reported release

    1C0

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-02-20

  • Closed date

    2012-03-20

  • Last modified date

    2012-05-02

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

    UK77192 UK77193

Modules/Macros

  • EZBTPCCO EZBTPLMO EZBTPSTF EZBTRTFO
    

Fix information

  • Fixed component name

    TCP/IP V3 MVS

  • Fixed component ID

    5655HAL00

Applicable component levels

  • R1C0 PSY UK77192

       UP12/04/24 P F204

  • R1D0 PSY UK77193

       UP12/04/24 P F204

Fix is available

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Document Information

Modified date:
02 May 2012