清晰/浅显：
http://www.cnblogs.com/sammyliu/p/4656176.html
IBM：写的一般般，价值不大
https://www.ibm.com/developerworks/cn/cloud/library/1506_xiaohh_openstacklb/index.html
Octavia
https://docs.openstack.org/octavia/latest/
LB Network:
https://docs.openstack.org/octavia/latest/contributor/design/version0.5/component-design.html#lb-network
VIP:
https://en.wikipedia.org/wiki/Virtual_IP_address