Encapsulating IPsec ESP in UDP for Load-balancing

IPsec Virtual Private Network (VPN) is widely used by enterprises to interconnect their geographical dispersed branch office locations across the Wide Area Network (WAN) or the Internet, especially in the Software-Defined-WAN (SD-WAN) era. In addition, IPsec is also increasingly used by cloud providers to encrypt IP traffic traversing data center networks and data center interconnect WANs so as to meet the security and compliance requirements, especially in financial cloud and governmental cloud environments. To fully utilize the bandwidth available in the data center network, the data center interconnect WAN or the Internet, load balancing of IPsec traffic over Equal Cost Multi-Path (ECMP) and/or Link Aggregation Group (LAG) is much attractive to those enterprises and cloud providers. This document defines a method to encapsulate IPsec Encapsulating Security Payload (ESP) packets over UDP tunnels for improving load-balancing of IPsec ESP traffic.