LI77276: MAX BTU SIZE ON INCOMING LINK INCORRECT IN XID

Communications Server for Linux, Version 6.2.3 -- Last Fixpack

APAR status

• Closed as program error.

Error description

• Communications Server for AIX and Linux
  ---------------------------------------
  Link failure with the following message in the sna.err log:
  
  2011-09-11 09:13:31 EST 1536-14(2-10) E (snatest)
  GDLC detected LS outage.
  LS     = TESTLS
  Outage = frame overflow (-9999)
  

Local fix

• A workaround is to configure the link BTU size to be equal to or
  larger than the port BTU size.
  

Problem summary

• USERS AFFECTED:
  All using LLC links.
  
  PROBLEM DESCRIPTION:
  When an incoming connection matches a predefined link station
  definition, the BTU size sent on the XID is taken from the port
  definition, but the BTU size sent to the DLC is taken from the
  link definition. If the link setting is smaller than the port
  setting, that could allow a condition where the remote side can
  send a frame larger than the DLC will accept, causing a frame
  overflow condition which causes the link to fail.
  
  LOCAL FIX:
  A workaround is to configure the link BTU size to be equal to
  the port BTU size.
  
  PROBLEM SUMMARY:
  The wrong configuration setting is being used in XID
  negotiation.
  

Problem conclusion

• Code has been modified to correctly set the maximum BTU size on
  the transmitted XIDs.
  
  This problem also exists in CS Linux but does not cause the
  link to fail. The code has also been corrected in CS Linux.
  

Temporary fix

• sna_v5router64
  

Comments

APAR Information

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

  IV08617

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

Fix information

• Fixed component name

  CS LINUX ON ZSE

• Fixed component ID

  5724I3400

Applicable component levels

• R623 PSY