IP over HTTPS ("IP-HTTPS", "MS-IPHTTPS") is a Microsoft network tunneling protocol. The IP-HTTPS protocol transports IPv6 packets across non-IPv6 networks. It does a similar job as the earlier 6to4 or Teredo tunneling mechanisms.
Microsoft used to discourage IP-HTTPS use because it was slow. [1]
For Windows Server 2012, Microsoft changed the internal workings of the protocol, and IP-HTTPS is now the "preferred IPv6 transition technology" for their DirectAccess VPN technology. [2]
The problem with IP-HTTPS is that it should be considered, and is instantiated as, a protocol of last resort. [...] the primary reason being that it's the lowest performing of the IPv6 transition technology protocols.
IP-HTTPS is now the preferred IPv6 transition technology for DirectAccess.