Anything In Anything (AYIYA)
Many users are currently located behind NATs which prohibit the usage of proto-41 IPv6 in IPv4 tunnels [RFC3056] unless they manually reconfigure their NAT setup which in some cases is impossible as the NAT cannot be configured to forward proto-41 ([RFC1933]) to a specific host. There might also be cases when multiple endpoints are behind the same NAT, when multiple NATs are used or when the user has no control at all over the NAT setup. This is an undesired situation as it limits the deployment of IPv6 [RFC3513], which was meant to solve the problem of the disturbance in end to end communications caused by NATs, which where created because of limited address space in the first place.
This problem can be solved easily by tunneling the IPv6 packets over either UDP [RFC0768], TCP [RFC0793] or even SCTP [RFC2960]. Taking into consideration that multiple separate endpoints could be behind the same NAT and/or that the public endpoint can change on the fly, there is also a need to identify the endpoint that certain packets are coming from and endpoints need to be able to change e.g. source addresses of the transporting protocol on the fly while still being identifiable as the same endpoint. The protocol described in this document is independent of the transport and payload's protocol. An example could be IPv6-in-UDP-in-IPv4, which is a typical setup that can be used by IPv6 Tunnel Brokers [RFC3053].
This document does not describe how to determine the identity, signature type or the inner and outer protocols. These should be negotiated manually or automatically by e.g. using TSP or a relevant protocol which is capable of describing the configuration parameters of AYIYA tunnels. Separate documents for the configuration protocols supporting AYIYA should include the details on how this is done.
NOTE: Current AYIYA drafts and implementations use SHA1 as a hashing algorithm. Due to speed reasons this will soon be shifted to MMH (Multilinear Modular Hash) which is a much faster algorithm, thus lightening the load on the PoPs when AYIYA will be in high use.
An official port number has been received from IANA and it is 5072.
Question or comments: Contact SixXS.