- each proxy stores average RTT (round trip time) of last rttCount queries.
   For now, I assigned the value 4 to rttCount
 - the read timeout is calculated as doubled average RTT, but it cannot
   exceed default timeout
 - initial avg RTT is set to a half of default timeout, so initial timeout
   is equal to default timeout
 - the RTT for failed read is considered equal to default timeout, so any
   failed read will lead to increasing average RTT (up to default timeout)
 - dynamic timeouts will let us react faster on lost UDP packets
 - in future, we may develop a low-latency forward policy based on
   collected RTT values of proxies