LI77312: MODIFICATIONS TO RTP_TUNING TO ALLOW SMALLER REFIFO AND SRT CAPS
A fix is available
Closed as program error.
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.
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.
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.
Reported component name
CS LINUX ON ZSE
Reported component ID
NoSpecatt / Xsystem
Last modified date
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fixed component name
CS LINUX ON ZSE
Fixed component ID
Applicable component levels