PM90592: HIGH AMOUNT OF OUTBOUND DISCARDS SEEN IN NETSTAT DEV FOR HIPERSOCKET INTERFACE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Outbound packets are being discarded over Hipersocket
  interfaces. This contributes to very poor throughput, as TCP
  retransmission will occur after these packets are discarded.
  The packet loss occurs when more then 8 simultaneous send
  operations are performed over the same Hipersocket interface to
  more than 8 different destinations.
  
  
  
  
  
  
  
  
  Additional Symptom(s) Search Keyword(s): Hipersocket discard
  netstat dev
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communications Server   *
  *                 for z/OS Version 1 Release(s) 13 IP:         *
  *                 Hipersockets                                 *
  ****************************************************************
  * PROBLEM DESCRIPTION: Outbound discards over HiperSockets     *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When a stack is sending a high volume of data over Hipersockects
  to more than 8 next-hop IP addresses, packets may be discarded.
  There is an array of 8 elements to hold the packets, where each
  slot represents a next hop address.  When the array becomes full
  and there are more packets to send with next hop addresses that
  are not already active in the array the packets with different
  next hop addresses may be discarded.
  +-------------------------------------------------------------+
  + 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

• Change HiperSockets outbound processing to increase the size
  of the array to 16 and limit the queueing logic to flush the
  array before the limit is exceeded.
  
  * Cross Reference between External and Internal Names
  

Temporary fix

Comments

APAR Information

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

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

  UK96678 PM95157 PM95163

Modules/Macros

• EZBCTFME
  EZBIFBP1
  EZBIFOUT
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R1D0 PSY UK96678

     UP13/09/07 P F309

Fix is available

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