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Cisco Bug: CSCvs42803 - Queued call disruptions due to MDS Sync delay on duplex VRU PG across WAN

Last Modified

Jan 06, 2020

Products (1)

  • Cisco Unified Contact Center Enterprise

Known Affected Releases

10.5(1) 11.5(1) 11.6(1) 12.0(1) 12.5(1)

Description (partial)

Symptom:
MDS sync delay messages on duplex VRU PG nodes across WAN is observed with the combination of high CPS/call volume and ECC variables

 
 Following error observed in the PG MDS logs.
 
 10:16:06:941 PG15A-mds MDS message sync delay exceeded 3000 ms (Now: 3401, Avg: 1974, Max: 3401, Min: 0).
10:16:12:334 PG15A-mds MDS message sync delay exceeded 3000 ms (Now: 5382, Avg: 2655, Max: 5382, Min: 0).
10:16:23:895 PG15A-mds MDS message sync delay exceeded 3000 ms (Now: 11559, Avg: 4435, Max: 11559, Min: 0)

All this eventually leads to call failure if waiting CVP does not receive updated instruction within 5 seconds.

Conditions:
VRU PG with 4 PIMs all active on same side, cluster across a WAN sharing private network. 
QoS enabled on the PG but not in the network. 
TCP ack delay generally 70 ms RTT, but frequently 120 ms and sometimes 240 ms RTT.
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