當 ARIN 只剩下最後一個 /8 的 IPv4 位置時，將會啟動第四階段的發放機制，而昨天進入這個機制了：「ARIN Enters Phase Four of the IPv4 Countdown Plan」。
出自「ARIN IPv4 Countdown Plan」這頁。
目前的進度是：
- Phase One began in February 2011 when ARIN received its last /8 from IANA.
- Phase Two began in September 2012 when ARIN reached three remaining /8 equivalents.
- Phase Three began in August 2013 when ARIN reached two remaining /8 equivalents.
- Phase Four began in April 2014 when ARIN reached one remaining /8 equivalent.
不過 IPv6 的進展還是苦哈哈啊...