TSAPI Link Flooding

Another problem this week which caused an aborted Empirix performance testing cycle. When we added in additional extension DNs we started to see problems with DNs not being registered / monitored correctly. The Avaya TSAPI server logs were full of the following:

CSTAUniversalFailureConfEvent
{
error requestTimeoutRejection
}

CSTAUniversalFailureConfEvent
{
error outstandingRequestLimitExceeded
}

Also, in the Avaya AES logs we saw the following:

16:30:35 ERROR:CRITICAL:TSAPI:TSERVER:../ClnMsg.cpp/417 10 CLNTMSG[1]: Message CSTAMonitorCallsViaDevice for client Genesys avayatsapi_server ac 10.52.151.6, driver AVAYA#SWITCH#CSTA#KFNAY6206P, is being rejected because of driver flow control. The number of messages for this driver exceeds the allowed threshold. Messages Queued to Tserver/Driver: 752 (0x2f0), Priority Messages Queued: 0 (0x0), Messages Allocated: 51 (0x33), Max Flow Allowed: 800 (0x320)

16:30:35 ERROR:FYI:TSAPI:TSERVER:../ClnMsg.cpp/417 10 CLNTMSG[1]: If flow control occurs frequently for driver AVAYA#SWITCH#CSTA#KFNAY6206P, consider distributing traffic for this driver across additional AE Servers. If this problem occurs only intermittently, use CTI OAM Administration (Administration > Security Database > Tlinks) to increase the value of the Max Flow Allowed field.

We are using T-Server for Avaya TSAPI (8.0.006.03) connected to Avaya AES 4.2.1.

After a bit of solution searching we upgraded the Avaya TSAPI client from 4.1 to 5.2.4 without any success. After a bit of playing around we found a temporary workaround by setting various T-Server options:

background-processing = false
use-link-bandwidth = 8 ***
use-link-bandwidth-startup = 8 ***
use-link-bandwidth-backup = 8 ***
max-attempts-to-register = 10
register-attempts = 5
register-tout = 2 sec

However, the above settings limit the CTI link bandwidth to 8 messages/second so it takes a long time to restart T-Server!

Further solution searching came up with the following:

“In most cases Avaya PSN2414r2 is required for TSAPI TServer to function correctly. Avaya PSN2414r2 is a restricted patch that allows TSAPI to pull licenses up front instead of individual SSL sessions each time TServer registers DNs, routes calls, or monitors calls.”

We are running version AES 4.2.1 which does not include the PSN 2414 patch. The next step is to upgrade AES to 4.2.4 (version 5.2 although officially supported by Genesys is a major upgrade and deemed to risky at the moment)

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