Energy Sciences Network Jisc Tachyon Dynamics When [RFC6724] was published it defined an address selection algorithm along with a default policy table, and noted a number of examples where that policy table might benefit from adjustment for specific scenarios. It also noted that it is important for implementations to provide a way to change the default policies as more experience is gained. This update draws on several years of operational experience to refine RFC 6724 further, with particular emphasis on preference for the use of ULA addresses over IPv4 addresses and the addition of mandatory support for Rule 5.5. The update also demotes the preference for 6to4 addresses. The changes to default behavior improve supportability of common use cases, including automatic / unmanaged scenarios. It is recognized that some less common deployment scenarios may require explicit configuration or custom changes to achieve desired operational parameters.