PM95157: 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 2 Release(s) 1 IP:                          *
  * Hipersockets                                                 *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * (sysroute of PM90592)                                        *
  *                                                              *
  * Outbound discards over HiperSockets                          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * When a stack is sending a high volume of data over           *
  * Hipersockects                                                *
  * to more than 16 next-hop IP addresses, packets may be        *
  * discarded.                                                   *
  * There is an array of 16 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.                         *
  ****************************************************************
  

Problem conclusion

• Change HiperSockets outbound processing to limit the queueing
  logic
  to flush the array before the limit of 16 is exceeded.
  

Temporary fix

Comments

APAR Information

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

  PM90592

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

  UK96771

Modules/Macros

• EZBIFOUT EZBIFBP1
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R210 PSY UK96771

     UP13/08/23 P F308

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.