Internet Engineering Task Force A. Durand Internet-Draft Comcast Intended status: Informational November 12, 2007 Expires: May 15, 2008 Non dual-stack IPv6 deployments for broadband providers draft-durand-v6ops-natv4v6v4-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 15, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract The common thinking for the last 10+ years has been to say that dual stack was the answer to v6 transition and that most things would be converted to dual stack way before we ran out of v4. Well, it has not happened. We are going to run out of IPv4 addresses soon, way before any significant IPv6 deployment will have occur. As a result, broadband deployments now need to contemplate IPv6-only provisioning and NAT as a classic solution to maintain some form of connectivity between those environments and the legacy Internet. Durand Expires May 15, 2008 [Page 1] Internet-Draft Abbreviated Title November 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 2. IPv4 exhaustion coming sooner than expected . . . . . . . . . . 3 3. Handling the legacy . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Legacy edges of the Internet for broadband customers . . . 3 3.2. Content and Services available on the Internet . . . . . . 4 3.3. Burden on service providers . . . . . . . . . . . . . . . . 4 4. Solution space . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. IPv6-only . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. Double IPv4->IPv4->IPv4 NAT . . . . . . . . . . . . . . . . 4 4.3. Double IPv4->IPv6->IPv4 NAT . . . . . . . . . . . . . . . . 5 4.4. Tunneling . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 8. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Durand Expires May 15, 2008 [Page 2] Internet-Draft Abbreviated Title November 2007 1. Introduction This memo will present a service provider view on IPv6 deployment and some of the necessary technologies to achieve it. 1.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2. IPv4 exhaustion coming sooner than expected Global public IPv4 addresses coming from the IANA free pool are running out faster than predicted a few years ago. The current model shows that exhaustion could happen as early as 2010. See http://ipv4.potaroo.net for more details. Those projection ares based on the assumption that tomorrow is going to be very similar to today, ie looking at recent address consumption figures is a good indicator of future consumption patterns. This of course, does not take into account any new large scale deployment of IP technology or any human reaction when facing an upcoming shortage. The prediction of the exact date of exhaustion of the IANA free pool is outside the scope of this document, however one conclusion must be drawn from that study: there will be in the near future a point where new global public IPv4 addresses will not be available and thus any new broadband deployment may have to consider the option of not provisioning any IPv4 addresses to the WAN facing interface of edge devices. The IPv6 deployment model known as "dual stack" can be a non starter in such environments. 3. Handling the legacy 3.1. Legacy edges of the Internet for broadband customers Broadband customers have a mix and match of IP enable devices at home. The most recent operating systems (eg Windows Vista or MacOS-X) can operate in an IPv6-only environment, however most of the legacy one can't. It has been reported, for example, that windows XP cannot process DNS requests over IPv6 transport. Expecting broadband customers to massively upgrade their software (and in most cases the corresponding hardware) to deploy IPv6 is a very tall order. Durand Expires May 15, 2008 [Page 3] Internet-Draft Abbreviated Title November 2007 3.2. Content and Services available on the Internet IPv6 deployment has been very long to take off, so the current situation is that almost none of the content and services available on the Internet are accessible over IPv6. This will probably change in the future, but for now, one has to make the assumption that most of the traffic generated by (and to) broadband customers will be sent to (and originated by) IPv4 nodes. 3.3. Burden on service providers As a conclusion, broadband service providers may be faced with the situation where they have IPv4 customers willing to communicate with IPv4 servers on the Internet but may not have any IPv4 addresses left to assign to them... 4. Solution space A number of solution can be studied in that space: IPv6-only, double IPv4>IPv4->IPv4 NAT, double IPv4->IPv6->IPv4 NAT, and IPv4 over IPv6 tunneling. 4.1. IPv6-only The first solution that comes to mind is simply to provision new broadband customers with only IPv6 addresses. However, two immediate issues come to mind: a. Legacy devices in the customer home will not be able to communicate with the outside. b. New IPv6-only capable devices will not be able to communicate with legacy IPv4-only servers in the Internet. 4.2. Double IPv4->IPv4->IPv4 NAT This solution consists of provisioning broadband customers with a private [RFC1918] address on the WAN side of the home gateway, and then translate this private IPv4 address somewhere within the service provider network into a global IPv4 address. Devices behind the home gateway will then be translated twice, once by the home gateway itself, and another time by the NAT within the service provider. This solution has the advantage of reducing the total number of global IPv4 addresses needed by consolidating the traffic of multiple customers on a unique IPv4 addresses. The first drawback is that some applications may have a more difficult time going through two Durand Expires May 15, 2008 [Page 4] Internet-Draft Abbreviated Title November 2007 levels of NAT. Another drawback that can be a show stopper is that this solution limits the number of customer within an access network to the size of net 10, ie somewhere between 10 and 16 million depending on address efficiency. Note that very large networks such as Comcast have already ran out of RFC1918 space a few years ago. 4.3. Double IPv4->IPv6->IPv4 NAT When private address space is running out as well, the next step is to have the home gateway translate internal RFC1918 space into global IPv6 addresses. However, as the final destination may not be configured with IPv6, those packets will have to be translated a second time into IPv4 packets. This second translation will have to occur within the service provider network. The implications of this second level of translation is very similar to those in the model above of a double IPv4->IPv4->IPv4 translation. There will be a need for a far of translator within the service provider network operating at line speed. Some applications may have a harder time working through a second level of NAT. On top of that, some MTU adaptation will have to take place to accommodate for the longer IPv6 header. 4.4. Tunneling When IPv6-only connectivity is offered to the customer, one could be tempted to look at IPv4 over IPv6 tunnels to re-establish connectivity for the legacy IPv4 hosts. The Softwire hub and spoke solution, based on L2TP tunnels could be the perfect candidate in that space. However, the main drawback of that solution is that it would require an IPv4 address to be configured on that tunnel. More, that address could not be shared among subscribers. As such, this solution would not consume less IPv4 addresses than a regular dual-stack deployment and will be be a non starter in environment where IPv4 addresses are rare. 5. Acknowledgements Send the author comments if you want your name listed here. 6. IANA Considerations This memo includes no request to IANA. Durand Expires May 15, 2008 [Page 5] Internet-Draft Abbreviated Title November 2007 This draft does not request any IANA action. 7. Security Considerations Security issues associated with NAT have long been documented. A future version of this document may include some references here to previous work. 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Author's Address Alain Durand Comcast 1500 Market st Philadelphia, PA 19102 USA Email: alain_durand@cable.comcast.com Durand Expires May 15, 2008 [Page 6] Internet-Draft Abbreviated Title November 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Durand Expires May 15, 2008 [Page 7]