+/**
+ * The IPIP module implements IP{v4,v6} over IP{v4,v6} tunnelling as
+ * described in RFC2473 and to some extent the largely historical
+ * RFC1853. The module also supports an IPv4 over IPv6 automatic
+ * tunnelling mechanism called 6RD (RFC5969).
+ *
+ * The IPIP API module supports a CRD model for adding, deleting and
+ * listing tunnels. A tunnel is represented as an interface in
+ * VPP. The "handle" representing a tunnel is the sw_if_index. As any
+ * interface, the user must configure an IPv4 and/or IPv6 address on
+ * the interface. This is the inner or payload protocol.
+ *
+ * Tunnel MTU: The tunnel MTU (the payload MTU) is configurable per
+ * protocol. If a tunnel MTU is larger than the path MTU, the outer
+ * packet will be fragmented. Fragmentation support is configurable,
+ * as it can have severe performance issues, and might be used as an
+ * attack vector (the remote side must reassemble.)
+ *
+ * Traffic class / TOS field can either be configured to a fixed
+ * value, or can be copied from the inner to the outer header.
+ * (For now we have stolen ~0 to indicate copy).
+ *
+ * Note:
+ *
+ * - The Tunnel encapsulation limit described in RFC2473 is not
+ * implemented.
+ *
+ * - ICMP proxying, as in a tunnel head-end receiving ICMP erors on
+ * the outer packet is currently not relayed to the original source
+ * of the packet.
+ *
+ * - PMTUD / MTU probing and tunnel keepalives are not yet implemented.
+ *
+ */
+
+option version = "1.1.0";