Anycast 任播

In Internet Protocol Version 6 (IPv6), anycast is communication
between a single sender and the nearest of several receivers in
a group. The term exists in contradistinction to multicast,
communication between a single sender and multiple receivers, and unicast, communication between a single sender and a single receiver in a network.

在 IPV6 的 Anycast 功能可以讓單一來源點，送給某個特定群體中「最近的一點」主要功能是用來進行路由表更新，概念是：

使用 Anycast 會送給某個群組中「最近」的一點，這個站台視為一個初始點，初始點會把收到的資訊，再以 Anycast 的方式，傳給同群組內的其中一台，就這樣逐一傳遞，讓大家的路由表都更新

Anycasting is designed to let one host initiate the efficient updating of router tables for a group of hosts. IPv6 can determine which gateway host is closest and sends the packets to that host as though it were a unicast communication. In turn, that host can anycast to another host in the group until all routing tables are updated.