You can use the TCP Ping utility to determine network latency between two instances. See this for more details
yum install tcptraceroute
cd /home/username
wget http://www.vdberg.org/~richard/tcpping
chmod 755 tcpping
./tcpping 192.25.26.27 4503
To clean up, delete TCP Ping with rm -rf tcpping
and uninstall TCP TraceRoute with yum remove tcptraceroute