Trafficserver cluster network congestion

[An Dao <da...@yahoo.com>]

 Dear all,
I'm using trafficserver 4.2.3 with cluster 3 node, recently, the cluster is not stable at peak time, at that time, http request rate to each node is about 4k req/s , the load of server (CPU, RAM, Disk) is not the problem, could any one help me about this issue? How can I troubleshoot this? 
When it happen, the cluster loss cache mode, that make my backend servers overload. 

The diags.log show up the message below:
[Jul 19 21:32:12.776] Server {0x2b2bc8706700} NOTE: Network congestion to [10.10.10.7] encountered, reverting to proxy only mode[Jul 19 21:32:13.729] Server {0x2b2bc8807700} NOTE: Network congestion to [10.10.10.7] encountered, reverting to proxy only mode[Jul 19 21:32:14.581] Server {0x2b2bc8908700} NOTongestionE: Network congestion to [10.10.10.7] encountered, reverting to proxy only mode[Jul 19 21:32:14.881] Server {0x2b2bc8a09700} NOTE: Network congestion to [10.10.10.7] encountered, reverting to proxy only mode[Jul 19 21:34:13.421] Server {0x2b2bc8706700} NOTE: Network congestion to [10.10.10.7] cleared, reverting to cache mode[Jul 19 21:34:14.690] Server {0x2b2bc8807700} NOTE: Network congestion to [10.10.10.7] cleared, reverting to cache mode[Jul 19 21:34:15.424] Server {0x2b2bc8908700} NOTE: Network congestion to [10.10.10.7] cleared, reverting to cache mode[Jul 19 21:34:15.820] Server {0x2b2bc8a09700} NOTE: Network congestion to [10.10.10.7] cleared, reverting to cache mode[Jul 19 21:46:57.825] Server {0x2b2bc3f2e700} NOTE: Network congestion to [10.10.10.7] encountered, reverting to proxy only mode[Jul 19 21:48:58.532] Server {0x2b2bc3f2e700} NOTE: Network congestion to [10.10.10.7] cleared, reverting to cache mode
Thanks alot and have a nice day,
An.