LI77310: MODIFICATIONS TO RTP_TUNING TO ALLOW SMALLER REFIFO AND SRT CAPS

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • Communications Server for AIX and Linux
    ---------------------------------------
    The define_rtp_tuning has been modified to allow for smaller
    refifo_cap and srt_cap values than documented.
    

Local fix

Problem summary

  • In certain error cases the performance of an HPR/IP link can be
    poor with delays of up to half a second to receive data.
    
    Specifically if multiple frames are being lost when being
    received by Communications Server (possibly dropped by a
    router?) and Communications Server has a high internal refifo
    timer (which it computes from the round trip time or rtt) then
    it may take a long time to request retransmission of the missing
    frames, so delaying throughput. In one system the rtt was seen
    to rise to 250ms which caused the refifo timer to also be raised
    to this value.
    

Problem conclusion

  • This APAR introduces two enhancements to the product:
    (1) The minimum value that the refifo_cap can be set to in
    define_rtp_tuning is reduced from 250ms to 5ms. This allows the
    large rtt values to be ignored in the protocol that requests
    retransmission. In modern fast networks it is VERY unlikely that
    packets can get delayed by more than a few ms.
    (2) Alter the default rtt timers from the architected intial
    values of 1000ms, 500ms, 250ms to 100ms, 50ms, 10ms for the
    different speed ranges. This allows HPR/IP send_rates to ramp up
    much quicker to appropriate rates for modern fast speed
    networks.
    

Temporary fix

Comments

APAR Information

  • APAR number

    LI77310

  • Reported component name

    CS FOR LINUX

  • Reported component ID

    5724I3300

  • Reported release

    623

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-04-26

  • Closed date

    2013-04-26

  • Last modified date

    2013-04-26

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

    LI76929

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

Fix information

  • Fixed component name

    CS FOR LINUX

  • Fixed component ID

    5724I3300

Applicable component levels

  • R623 PSY

       



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Document information


More support for:

Communications Server for Linux

Software version:

623

Reference #:

LI77310

Modified date:

2013-04-26

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