Hi, We would like to make the following comments in response to the IETF Last Call on the proposal to publish this draft as an Informational RFC. The guidelines for IP address allocations were documented in RFC2050, adopted in November 1996 as a Best Current Practice. This document described the framework of the Internet Registry system, and the roles and responsibilities of various parties involved in the distribution of addresses in the Internet. The document was not intentionally related to any particular routing technology, and addressed guidelines that would maximise the effective use of address space. The Memorandum of Understanding between the IETF and ICANN over the IANA activity, RFC2860, published in June 2000, provides further details of the address management function. In particular, the document notes that "assignments of specialised address blocks (such as multicast or anycast blocks), and experimental assignments are not considered to be policy issues, and shall remain subject to the provisions of this [document]." RFC 4773, published in December 2006, provides some guidelines to the IANA concerning the management of these specialised address assignments in IPv6: "IANA may undertake IPv6 address designations in support of special purposes as requested in "IANA Considerations" sections in IESG- reviewed RFCs, where an address is requested with an intended use of the designated address block for the purpose of testing or experimental usage activities initiated by IETF, or for specialised use of the address block in a context (e.g., anycast) associated with an Internet Standards track protocol." In this context the request to IANA to reserve an IPv6 /12 address and allocate out of it a /16 block for use as an EID space for the experimental LISP protocol presents some questions. It is noted that the LISP experiment already makes use of a /32 prefix, "with more than 250 sites using a /48 sub prefix", as noted in draft-ietf-lisp-eid-block-03.txt. Even with an overall 50% utilisation rate of this prefix there is scope in the current /32 address block to address some 32,000 further sites using a /48 sub prefix. If the LISP experiment fills this /32 prefix to such a level of utilisation then there would be reasonable grounds to make the case that at such a time the LISP activity would no longer be an experimental effort, as it would be an instance of an application that makes use of the global unicast address pool. In this case the provisions of RFC 4773, and the applicability of a special purpose address allocation would not be expected to apply, as this would fall under the terms of RFC2050 and the address allocation function would be administered by the Regional internet Registries, according to RFC2860. If we were to consider this request for the reservation of a /12 and the allocation of a /16 in the context of support for an experiment, then the nature of the experiment is unclear. At the scale of a /16 being capable of supporting a theoretical maximum of some 4.3 billion /48 end sites, and a /12 supporting a theoretical maximum of 68.7 billion /48 end sites, then the boundary conditions of such an experiment become challenging to define. How can one define the experiment to have finished? What are the plans to migrate out of the experimental address allocation? Would this renumbering out of an experimental address allocation even be feasible to contemplate if the experiment achieves a level of deployment that is commensurate with the allocation of /16? Such large scale deployment activities being undertaken under the provisions of an experimental activity also raises a number of questions about the registry services to be provided in support of such a reservation. Given that this particular experiment is intended to operate on the global IPv6 Internet it is apparent that some form of directory (e.g. Whois) and reverse DNS services will be necessary; is the provision of such services on a large scale (i.e. for potentially tens of thousands of individual entities) to be performed by the IANA? If so then this appears contrary to RFC 4773's statement that the "IANA will not maintain further sub-registries for any special purpose address block designated according to this direction." Further, the implementation of any large scale directory such as resulting from this type of experimental reservation would definitely pose serious policy issues, e.g. trading off operational visibility, privacy, and law enforcement needs, and by the spirit of the IETF/ICANN MOU on IANA activities (RFC 2860). It would appear from this perspective that such an assignment of address resources is not suitable to be made as an experimental assignment. The question this draft raises is to identify the basis of the request. An experimental allocation of this size does not appear to be consistent with a conventional view of an experiment. The draft's proposals appear more aligned to the activity of planning for large scale public deployment of a global routing infrastructure for global unicast addresses. But if that is indeed the case then the provisions of RFC4773 do not apply, as the special Purpose Address Allocation Registry does not encompass the allocation of address blocks for use in a global unicast address context in the context of large scale deployment activities. A possible course of action for the LISP Working Group and the IESG to consider would be for the existing /32 address be documented as an IANA Special Purpose Address allocation for use in supporting the current LISP experiment, and for the LISP advocates to make their case for particular requirements in the handling of global unicast address allocations in IPv6 to the regional addressing communities. This would allow the existing address policy development process to generate outcomes that appropriately address the desires and concerns of the broader community of stakeholders in supporting the potential requirements of a broad base of deployment of LISP in the Internet's routing environment. We do not support the publication of this draft as an Informational RFC. regards, John Curran, Paul Wilson, and Geoff Huston