A fix is available
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
JR44767
Reported component name
COMM SERV NT 6.
Reported component ID
5639F2503
Reported release
640
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2012-11-15
Closed date
2012-11-15
Last modified date
2012-11-15
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
COMM SERV NT 6.
Fixed component ID
5639F2503
Applicable component levels
R640 PSY
[{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SSHQNF","label":"Communications Server for Windows"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"640","Line of Business":{"code":"LOB35","label":"Mainframe SW"}}]
Document Information
Modified date:
12 October 2021