For E3 series we use supermicro motherboard that come with Intel NICs. If you had installed CentOS in your server, on heavy load you can experience slow NIC or packets loss. This is a bug in the default CentOS e1000 driver.
If you had CentOS you can easy fix. Enable EPEL repo:
# wget http://elrepo.org/elrepo-release-6-5.el6.elrepo.noarch.rpm
# rpm -Uvh elrepo-release-*
# yum clean all
# yum update -y
# yum install kmod-e1000e -y
System will be rebooted and will start with new update modules