Generic routing encapsulation (GRE) is a standard protocol described by RFC 1701, and is used for several TCP/IP functions. GRE is implemented for only IPv4 packets. GRE enables a wrapper to be placed around a packet during transmission of the data. A receiving stack that supports GRE removes the GRE wrapper, enabling the original packet to be processed by the receiving stack. GRE is often used to deliver a packet to a stack using an alternate destination IP address.