IV32160: NETWORK STORM BETWEEN VIOC AND VIOS WHEN LARGESEND IS TURNED OFF APPLIES TO AIX 5300-12

APAR status

• Closed as program error.

Error description

• Network storm between VIOC and VIOS will happen in the
  following scenario.
  
  1) Customer enables tcp_path_mtu_discovery on VIOC
  2) TCP connection got established
  3) Large send is disabled on SEA (Customer turns off
  large send on SEA )
  

Local fix

• tcp_pmtu_discover=0 in the vio client lpar will avoid the
  PMTU resend storm, but the sea will still fragment the
  largesend packet in software.
  

Problem summary

• When customer enable largesend and path MTU discovery,  the
  network performance is slower.  When they turned off path MTU
  discovery, the network performance is good.
  

Problem conclusion

• When path MTU is enabled, for the tcp connections largesend is
  turned off based on SEA's largesend attribute. This change
  avoids, the network storm between VIOS and VIOC when largesend
  is disabled on SEA
  

Temporary fix

Comments

• 5300-12 - use AIX APAR IV32160
  6100-06 - use AIX APAR IV22069
  6100-07 - use AIX APAR IV28700
  6100-08 - use AIX APAR IV31387
  7100-00 - use AIX APAR IV41892
  7100-01 - use AIX APAR IV23420
  7100-02 - use AIX APAR IV31324
  

APAR Information

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

  IV22069

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

Fix information

• Fixed component name

  AIX 5.3 EXT SUP

• Fixed component ID

  5765G0399

Applicable component levels

• R53E PSY

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