IPv6 Operations J. Livingood Internet-Draft Comcast Intended status: Informational February 22, 2011 Expires: August 26, 2011 IPv6 AAAA DNS Whitelisting Implications draft-ietf-v6ops-v6-aaaa-whitelisting-implications-03 Abstract The objective of this document is to describe what the whitelisting of DNS AAAA resource records is, hereafter referred to as DNS whitelisting, as well as the implications of this emerging practice and what alternatives may exist. The audience for this document is the Internet community generally, including the IETF and IPv6 implementers. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on August 26, 2011. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as Livingood Expires August 26, 2011 [Page 1] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 described in the Simplified BSD License. Livingood Expires August 26, 2011 [Page 2] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. How DNS Whitelisting Works . . . . . . . . . . . . . . . . . . 6 2.1. Description of the Operation of DNS Whitelisting . . . . . 7 3. What Problems Are Implementers Trying To Solve? . . . . . . . 8 4. Concerns Regarding DNS Whitelisting . . . . . . . . . . . . . 9 5. Similarities to Other DNS Operations . . . . . . . . . . . . . 12 5.1. Similarities to Split DNS . . . . . . . . . . . . . . . . 12 5.2. Similarities to DNS Load Balancing . . . . . . . . . . . . 12 6. Likely Deployment Scenarios . . . . . . . . . . . . . . . . . 13 6.1. Deploying DNS Whitelisting On An Ad Hoc Basis . . . . . . 13 6.2. Deploying DNS Whitelisting Universally . . . . . . . . . . 14 7. Implications of DNS Whitelisting . . . . . . . . . . . . . . . 15 7.1. Architectural Implications . . . . . . . . . . . . . . . . 15 7.2. Public IPv6 Address Reachability Implications . . . . . . 16 7.3. Operational Implications . . . . . . . . . . . . . . . . . 17 7.3.1. De-Whitelisting May Occur . . . . . . . . . . . . . . 17 7.3.2. Authoritative DNS Server Operational Implications . . 17 7.3.3. DNS Recursive Resolver Server Operational Implications . . . . . . . . . . . . . . . . . . . . . 18 7.3.4. Monitoring Implications . . . . . . . . . . . . . . . 19 7.3.5. Implications of Operational Momentum . . . . . . . . . 19 7.3.6. Troubleshooting Implications . . . . . . . . . . . . . 20 7.3.7. Additional Implications If Deployed On An Ad Hoc Basis . . . . . . . . . . . . . . . . . . . . . . . . 20 7.4. Homogeneity May Be Encouraged . . . . . . . . . . . . . . 20 7.5. Technology Policy Implications . . . . . . . . . . . . . . 21 7.6. IPv6 Adoption Implications . . . . . . . . . . . . . . . . 22 8. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8.1. Implement DNS Whitelisting Universally . . . . . . . . . . 23 8.2. Implement DNS Whitelisting On An Ad Hoc Basis . . . . . . 23 8.3. Do Not Implement DNS Whitelisting . . . . . . . . . . . . 23 8.3.1. Solving Current End User IPv6 Impairments . . . . . . 24 8.3.2. Gain Experience Using IPv6 Transition Names . . . . . 24 9. Is DNS Whitelisting a Recommended Practice? . . . . . . . . . 24 10. Security Considerations . . . . . . . . . . . . . . . . . . . 25 10.1. DNSSEC Considerations . . . . . . . . . . . . . . . . . . 25 10.2. Authoritative DNS Response Consistency Considerations . . 26 11. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 26 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 27 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 15.1. Normative References . . . . . . . . . . . . . . . . . . . 28 15.2. Informative References . . . . . . . . . . . . . . . . . . 29 Appendix A. Document Change Log . . . . . . . . . . . . . . . . . 31 Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 32 Livingood Expires August 26, 2011 [Page 3] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 32 Livingood Expires August 26, 2011 [Page 4] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 1. Introduction This document describes the emerging practice of whitelisting of DNS AAAA resource records (RRs), which contain IPv6 addresses, hereafter referred to as DNS whitelisting. The document explores the implications of this emerging practice are and what alternatives may exist. The practice of DNS whitelisting appears to have first been used by major web content sites (sometimes described herein as "highly- trafficked domains" or "major domains"). These web site operators, or domain operators, observed that when they added AAAA resource records to their authoritative DNS servers in order to support IPv6 access to their content that a small fraction of end users had slow or otherwise impaired access to a given web site with both AAAA and A resource records. The fraction of users with such impaired access has been estimated to be roughly 0.078% of total Internet users [IETF-77-DNSOP] [NW-Article-DNSOP] [Evaluating IPv6 Adoption] [IPv6 Brokenness]. Thus, in an example Internet Service Provider (ISP) network of 10 million users, approximately 7,800 of those users may experience such impaired access. As a result of this impairment affecting end users of a given domain, a few major domains have either implemented DNS whitelisting or are considering doing so [NW-Article-DNS-WL] [IPv6 Whitelist Operations]. When implemented, DNS whitelisting in practice means that a domain's authoritative DNS will return a AAAA resource record to DNS recursive resolvers [RFC1035] on the whitelist, while returning no AAAA resource records to DNS resolvers which are not on the whitelist. It is important to note that these major domains are motivated by a desire to maintain a high-quality user experience for all of their users. By engaging in DNS whitelisting, they are attempting to shield users with impaired access from the symptoms of those impairments. Critics of the practice of DNS whitelisting have articulated several concerns. Among these are that: o DNS whitelisting is a very different behavior from the current practice concerning the publishing of IPv4 address resource records, o that it may create a two-tiered Internet, o that policies concerning whitelisting and de-whitelisting are opaque, Livingood Expires August 26, 2011 [Page 5] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 o that DNS whitelisting reduces interest in the deployment of IPv6, o that new operational and management burdens are created, o and that the costs and negative implications of DNS whitelisting outweigh the perceived benefits, compared to fixing underlying impairments. This document explores the reasons and motivations for DNS whitelisting. It also explores the outlined concerns regarding this practice. Readers will hopefully better understand what DNS whitelisting is, why some parties are implementing it, and what criticisms of the practice exist. 2. How DNS Whitelisting Works DNS whitelisting is implemented in authoritative DNS servers. These servers implement IP address-based restrictions on AAAA query responses. So far, DNS whitelisting has been primarily implemented by web server operators deploying IPv6-enabled services. For a given operator of a website, such as www.example.com, the operator essentially applies an access control list (ACL) on the authoritative DNS servers for the domain example.com. The ACL is populated with the IPv4 and/or IPv6 addresses or prefix ranges of DNS recursive resolvers on the Internet, which have been authorized to receive AAAA resource record responses. These DNS recursive resolvers are operated by third parties, such as ISPs, universities, governments, businesses, and individual end users. If a DNS recursive resolver IS NOT matched in the ACL, then AAAA resource records will NOT be sent in response to a query for a hostname in the example.com domain. However, if a DNS recursive resolver IS matched in the ACL, then AAAA resource records will be sent in response to a query for a given hostname in the example.com domain. While these are not network- layer access controls they are nonetheless access controls that are a factor for end users and other parties like network operators, especially as networks and hosts transition from one network address family to another (IPv4 to IPv6). In practice, DNS whitelisting generally means that a very small fraction of the DNS recursive resolvers on the Internet (those in the whitelist ACL) will receive AAAA responses. The large majority of DNS resolvers on the Internet will therefore receive only A resource records containing IPv4 addresses. Thus, quite simply, the authoritative server hands out different answers depending upon who is asking; with IPv4 and IPv6 resource records for some on the authorized whitelist, and only IPv4 resource records for everyone else. See Section 2.1 and Figure 1 for a description of how this Livingood Expires August 26, 2011 [Page 6] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 works. Finally, DNS whitelisting can be deployed in two primary ways: universally on a global basis, or on an ad hoc basis. Deployment on a universal deployment basis means that DNS whitelisting is implemented on all authoritative DNS servers, across the entire Internet. In contrast, deployment on an ad hoc basis means that only some authoritative DNS servers, and perhaps even only a few, implement DNS whitelisting. These two potential deployment models are described in Section 6. 2.1. Description of the Operation of DNS Whitelisting The system logic of DNS whitelisting is as follows: 1. The authoritative DNS server for example.com receives DNS queries for the A (IPv4) and AAAA (IPv6) address resource records for the FQDN www.example.com, for which AAAA (IPv6) resource records exist. 2. The authoritative DNS server examines the IP address of the DNS recursive resolver sending the AAAA (IPv6) query. 3. The authoritative DNS server checks this IP address against the access control list (ACL) that is the DNS whitelist. 4. If the DNS recursive resolver's IP address IS matched in the ACL, then the response to that specific DNS recursive resolver can contain AAAA (IPv6) address resource records. 5. If the DNS recursive resolver's IP address IS NOT matched in the ACL, then the response to that specific DNS recursive resolver cannot contain AAAA (IPv6) address resource records. In this case, the server should return a response with the response code (RCODE) being set to 0 (No Error) with an empty answer section for the AAAA record query. Livingood Expires August 26, 2011 [Page 7] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 --------------------------------------------------------------------- A query is sent from a DNS recursive resolver that IS NOT on the DNS whitelist: Request Request www.example.com www.example.com AAAA +-------------+ AAAA +-----------------+ ++--++ ---------> | RESOLVER | ---------> | www.example.com | || || A | **IS NOT** | A | IN A exists | +-++--++-+ ---------> | ON | ---------> | IN AAAA exists | +--------+ A | example.com | A | | Host <--------- | WHITELIST | <--------- | | Computer A Record +-------------+ A Record +-----------------+ Response DNS Recursive Response example.com (only IPv4) Resolver (only IPv4) Authoritative #1 Server --------------------------------------------------------------------- A query is sent from a DNS recursive resolver that IS on the DNS whitelist: Request Request www.example.com www.example.com AAAA +-------------+ AAAA +-----------------+ ++--++ ---------> | RESOLVER | ---------> | www.example.com | || || A | **IS** | A | IN A exists | +-++--++-+ ---------> | ON | ---------> | IN AAAA exists | +--------+ AAAA | example.com | AAAA | | Host <--------- | WHITELIST | <--------- | | Computer A | | A | | <--------- | | <--------- | | A and AAAA +-------------+ A and AAAA +-----------------+ Record DNS Recursive Record example.com Responses Resolver Responses Authoritative (IPv4+IPv6) #2 (IPv4+IPv6) Server --------------------------------------------------------------------- Figure 1: DNS Whitelisting - Functional Diagram 3. What Problems Are Implementers Trying To Solve? As noted in Section 1, domains which implement DNS whitelisting are attempting to protect a few users of their domain, who have impaired IPv6 access, from having a negative experience (poor performance). While it is outside the scope of this document to explore the various reasons why a particular user's system (host) may have impaired IPv6 access, for the users who experience this impairment it is a very real performance impact. It would affect access to all or most dual Livingood Expires August 26, 2011 [Page 8] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 stack services to which the user attempts to connect. This negative end user experience can range from someone slower than usual (as compared to native IPv4-based access), to extremely slow, to no access to the domain whatsoever. While one can debate whether DNS whitelisting is the optimal solution to the end user experience problem, it is quite clear that DNS whitelisting implementers are interested in maximizing the performance of their services for end users as a primary motivation for implementation. At least one highly-trafficked domain has noted that they have received requests to not send DNS responses with AAAA resource records to particular resolvers. In this case, the operators of those recursive resolvers have expressed a concern that their IPv6 network infrastructure is not yet ready to handle the large traffic volume which may be associated with the hosts in their network connecting to the websites of these domains. This concern is clearly a temporary consideration relating to the deployment of IPv6 network infrastructure on the part of networks with end user hosts, rather than a long-term concern. These end user networks may also have other tools at their disposal in order to address this concern, including applying rules to network equipment such as routers and firewalls (this will necessarily vary by the type of network, as well as the technologies used and the design of a given network), as well as configuration of their recursive resolvers (though modifying or suppressing AAAA resource records in a DNSSEC-signed domain on a Security-Aware Resolver will be problematic Section 10.1). Some implementers with highly-trafficked domains have explained that DNS whitelisting is a necessary, though temporary, risk reduction tactic intended to ease their transition to IPv6 and minimize any perceived risk in such a transition. As a result, they perceive this as a tactic to enable them to incrementally enable IPv6 connectivity to their domains during the early phases of their transition to IPv6. Finally, some domains, have run IPv6 experiments whereby they added AAAA resource records and observed and measured errors [Heise Online Experiment], which should be important reading for any domain contemplating either the use of DNS whitelisting or simply adding IPv6 addressing to their site. 4. Concerns Regarding DNS Whitelisting There are a number of potential implications relating to DNS whitelisting, which have been raised as concerns by some parts of the Internet community. Many of those potential implications are further Livingood Expires August 26, 2011 [Page 9] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 enumerated here and in Section 7. Some parties in the Internet community, including ISPs, are concerned that the practice of DNS whitelisting for IPv6 address resource records represents a departure from the generally accepted practices regarding IPv4 address resource records in the DNS on the Internet [Whitelisting Concerns]. These parties explain their belief that for A resource records, containing IPv4 addresses, once an authoritative server operator adds the A record to the DNS, then any DNS recursive resolver on the Internet can receive that A record in response to a query. By extension, this means that any of the hosts connected to any of these DNS recursive resolvers can receive the IPv4 address resource records for a given FQDN. This enables new server hosts which are connected to the Internet, and for which a fully qualified domain name (FQDN) such as www.example.com has been added to the DNS with an IPv4 address record, to be almost immediately reachable by any host on the Internet. In this case, these new servers hosts become more and more widely accessible as new networks and new end user hosts connect to the Internet over time, capitalizing on and increasing so-called "network effects" (also called network externalities). It also means that the new server hosts do not need to know about these new networks and new end user hosts in order to make their content and applications available to them, in essence that each end in this end-to-end model is responsible for connecting to the Internet and once they have done so they can connect to each other without additional impediments or middle networks or intervening networks or servers knowing about these end points and whether one is allowed to contact the other. In contrast, the concern is that DNS whitelisting may fundamentally change this model. In the altered DNS whitelisting end-to-end model, one end (where the end user is located) cannot readily connect to the other end (where the content is located), without parts of the middle (recursive resolvers) used by one end (the client, or end user hosts) being known to an intermediary (authoritative nameservers) and approved for access to the resource at the end. As new networks connect to the Internet over time, those networks need to contact any and all domains which have implemented DNS whitelisting in order to apply to be added to their DNS whitelist, in the hopes of making the content and applications residing on named server hosts in those domains accessible by the end user hosts on that new network. Furthermore, this same need to contact all domains implementing DNS whitelisting also applies to all pre-existing (but not whitelisted) networks connected to the Internet. In the current IPv4 Internet when a new server host is added to the Internet it is generally widely available to all end user hosts and networks, when DNS whitelisting of IPv6 resource records is used, Livingood Expires August 26, 2011 [Page 10] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 these new server hosts are not accessible to any end user hosts or networks until such time as the operator of the authoritative DNS servers for those new server hosts expressly authorizes access to those new server hosts by adding DNS recursive resolvers around the Internet to the ACL. This has the potential to be a significant change in reachability of content and applications by end users and networks as these end user hosts and networks transition to IPv6, resulting in more (but different) breakage. A concern expressed is that if much of the content that end users are most interested in is not accessible as a result, then end users and/or networks may resist adoption of IPv6 or actively seek alternatives to it, such as using multi-layer network address translation (NAT) techniques like NAT444 [I-D.shirasaki-nat444] on a long-term basis. There is also concern that this practice also could disrupt the continued increase in Internet adoption by end users if they cannot simply access new content and applications but must instead contact the operator of their DNS recursive resolver, such as their ISP or another third party, to have their DNS recursive resolver authorized for access to the content or applications that interests them. Meanwhile, these parties say, over 99.9% of the other end users that are also using that same network or DNS recursive resolver are unable to access the IPv6-based content, despite their experience being a positive one. While in Section 1 the level of IPv6-related impairment has been estimated to be as high as 0.078% of Internet users, which is a primary motivation cited for the practice of DNS whitelisting, it is not clear if the level of IPv4-related impairment is more or less that this percentage (which in any case is likely to have declined since its original citation). Indeed, as at least one document reviewer has pointed out, it may simply be that websites are only measuring IPv6 impairments and not IPv4 impairments, whether because IPv6 is new or whether those websites are simply unable to or are otherwise not in a position to be able to measure IPv4 impairment (since this could result in no Internet access whatsoever). As a result, it is worth considering that IPv4-related impairment could exceed that of IPv6-related impairment and that such IPv4-related impairment may have simply been accepted as "background noise" on the Internet for a variety of reasons. Of course, this comparison of the level of worldwide IPv6 impairments to IPv4 impairments is speculation, as the author is not aware of any good measurement of IPv4-related impairments which are comparable in nature to the IPv6- related impairment measurements which have recently been conducted around the world. An additional concern is that the IP address of a recursive resolver is not a precise indicator of the IPv6 preparedness, or lack of IPv6- related impairments, of end user hosts which query (use) a particular recursive resolver. While the recursive resolver may be an imperfect Livingood Expires August 26, 2011 [Page 11] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 proxy for judging IPv6 preparedness, it is at least one of the best available methods at the current time. 5. Similarities to Other DNS Operations Some aspects of DNS whitelisting may be considered similar to other common DNS operational techniques which are explored below. 5.1. Similarities to Split DNS DNS whitelisting has some similarities to so-called split DNS, briefly described in Section 3.8 of [RFC2775]. When split DNS is used, the authoritative DNS server returns different responses depending upon what host has sent the query. While [RFC2775] notes the typical use of split DNS is to provide one answer to hosts on an Intranet and a different answer to hosts on the Internet, the essence is that different answers are provided to hosts on different networks. This is basically the way that DNS whitelisting works, whereby hosts on different networks, which use different DNS recursive resolvers, receive different answers if one DNS recursive resolver is on the whitelist and the other is not. In [RFC2956], Internet transparency and Internet fragmentation concerns regarding split DNS are detailed in Section 2.1. [RFC2956] further notes in Section 2.7, concerns regarding split DNS and that it "makes the use of Fully Qualified Domain Names (FQDNs) as endpoint identifiers more complex." Section 3.5 of [RFC2956] further recommends that maintaining a stable approach to DNS operations is key during transitions such as the one to IPv6 that is underway now, stating that "Operational stability of DNS is paramount, especially during a transition of the network layer, and both IPv6 and some network address translation techniques place a heavier burden on DNS." 5.2. Similarities to DNS Load Balancing DNS whitelisting also has some similarities to DNS load balancing. There are of course many ways that DNS load balancing can be performed. In one example, multiple IP address resource records (A and/or AAAA) can be added to the DNS for a given FQDN. This approach is referred to as DNS round robin [RFC1794]. DNS round robin may also be employed where SRV resource records are used [RFC2782]. In another example, one or more of the IP address resource records in the DNS will direct traffic to a load balancer. That load balancer, in turn, may be application-aware, and pass the traffic on to one or more hosts connected to the load balancer which have different IP Livingood Expires August 26, 2011 [Page 12] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 addresses. In cases where private IPv4 addresses are used [RFC1918], as well as when public IP addresses are used, those end hosts may not be directly reachable without passing through the load balancer first . As such, while the IP address resource records have been added to the DNS, the end hosts are not necessarily directly reachable, which is in a small way similar to one aspect of DNS whitelisting. Additionally, a geographically-aware authoritative DNS server may be used, as is common with Content Delivery Networks (CDNs) or Global Load Balancing (GLB, also referred to as Global Server Load Balancing, or GSLB), whereby the IP address resource records returned to a resolver in response to a query will vary based on the estimated geographic location of the resolver [Resolvers in the Wild]. CDNs perform this function in order to attempt to direct hosts to connect to the nearest content cache. As a result, one can see some similarities with DNS whitelisting insofar as different IP address resource records are selectively returned to resolvers based on the IP address of each resolver (or other imputed factors related to that IP address). However, what is different is that in this case the resolvers are not deliberately blocked from receiving DNS responses containing an entire class of addresses; this load balancing function strives to perform a content location-improvement function and not an access control function. 6. Likely Deployment Scenarios In considering how DNS whitelisting may emerge more widely, there are two likely deployment scenarios, which are explored below. In either of these deployment scenarios, it is possible that reputable third parties could create and maintain DNS whitelists, in much the same way that blacklists are used for reducing email spam. In the email context, a mail operator subscribes to one or more of these lists and as such the operational processes for additions and deletions to the list are managed by a third party. A similar model could emerge for DNS whitelisting, whether deployment occurs universally or on an ad hoc basis. 6.1. Deploying DNS Whitelisting On An Ad Hoc Basis The seemingly most likely deployment scenario is where some authoritative DNS server operators implement DNS whitelisting but many or most others do not do so. What can make this scenario challenging from the standpoint of a DNS recursive resolver operator is determining which domains implement DNS whitelisting, particularly since a domain may not do so as they initially transition to IPv6, and may instead do so later. Thus, a DNS recursive resolver operator Livingood Expires August 26, 2011 [Page 13] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 may initially believe that they can receive AAAA responses as a domain adopts IPv6, but then notice via end user reports that they no longer receive AAAA responses due to that domain adopting DNS whitelisting. Of course, a domain's IPv6 transition may be effectively invisible to recursive server operators due to the effect of DNS whitelisting. In contrast to a universal deployment of DNS whitelisting Section 6.2, deployment on an ad hoc basis is likely to be significantly more challenging from an operational, monitoring, and troubleshooting standpoint. In this scenario, a DNS recursive resolver operator will have no way to systematically determine whether DNS whitelisting is or is not implemented for a domain, since the absence of AAAA resource records may simply be indicative that the domain has not yet added IPv6 addressing for the domain, rather than that they have done so but have restricted query access via DNS whitelisting. As a result, discovering which domains implement DNS whitelisting, in order to differentiate them from those that do not, is likely to be challenging. One benefit of DNS whitelisting being deployed on an ad hoc basis is that only the domains that are interested in doing so would have to upgrade their authoritative DNS servers in order to implement the ACLs necessary to perform DNS whitelisting. In this potential deployment scenario, it is also possible that a given domain will implement DNS whitelisting temporarily. A domain, particularly a highly-trafficked domain, may choose to do so in order to ease their transition to IPv6 through a selective deployment and minimize any perceived risk in such a transition. 6.2. Deploying DNS Whitelisting Universally The least likely deployment scenario is one where DNS whitelisting is implemented on all authoritative DNS servers, across the entire Internet. While this scenario seems less likely than ad hoc deployment due to some parties not sharing the concerns that have so far motivated the use of DNS whitelisting, it is nonetheless conceivable that it could be one of the ways in which DNS whitelisting is deployed. In order for this deployment scenario to occur, it is likely that DNS whitelisting functionality would need to be built into all authoritative DNS server software, and that all operators of authoritative DNS servers would have to upgrade their software and enable this functionality. It is likely that new Internet Draft documents would need to be developed which describe how to properly configure, deploy, and maintain DNS whitelisting. As a result, it is Livingood Expires August 26, 2011 [Page 14] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 unlikely that DNS whitelisting would, at least in the next several years, become universally deployed. Furthermore, these DNS whitelists are likely to vary on a domain-by-domain basis, depending upon a variety of factors. Such factors may include the motivation of each domain owner, the location of the DNS recursive resolvers in relation to the source content, as well as various other parameters that may be transitory in nature, or unique to a specific end user host type. It is probably unlikely that a single clearinghouse for managing whitelisting is possible; it will more likely be unique to the source content owners and/or domains which implement DNS whitelists. While this scenario may be unlikely, it may carry some benefits. First, parties performing troubleshooting would not have to determine whether or not DNS whitelisting was being used, as it always would be in use. In addition, if universally deployed, it is possible that the criteria for being added to or removed from a DNS whitelist could be standardized across the entire Internet. Nevertheless, even if uniform DNS whitelisting policies were not standardized, is also possible that a central registry of these policies could be developed and deployed in order to make it easier to discover them, a key part of achieving transparency regarding DNS whitelisting. 7. Implications of DNS Whitelisting There are many potential implications of DNS whitelisting. The key potential implications are detailed below. 7.1. Architectural Implications DNS whitelisting could be perceived as modifying the end-to-end model and/or the general notion of the architecture that prevails on the Internet today. This is because this approach moves additional access control information and policies into the middle of the DNS resolution path of the IPv6-addressed Internet, which generally did not exist before on the IPv4-addressed Internet. This poses some risks noted in [RFC3724]. In explaining the history of the end-to- end principle [RFC1958] states that one of the goals is to minimize the state, policies, and other functions needed in the middle of the network in order to enable end-to-end communications on the Internet. In this case, the middle network should be understood to mean anything other than the end hosts involved in communicating with one another. Some state, policies, and other functions have always been necessary to enable such end-to-end communication, but the goal of the approach has been to minimize this to the greatest extent possible. Livingood Expires August 26, 2011 [Page 15] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 It is also possible that DNS whitelisting could place at risk some of the observed benefits of the end-to-end principle, as listed in Section 4.1 of [RFC3724], such as protection of innovation. [RFC3234] details issues and concerns regarding so-called middleboxes, so there may also be parallel concerns with the DNS whitelisting approach, especially concerning modified DNS servers noted in Section 2.16 of [RFC3234], as well as more general concerns noted in Section 1.2 of [RFC3234] about the introduction of new failure modes. In particular, there may be concerns that configuration is no longer limited to two ends of a session, and that diagnosis of failures and misconfigurations becomes more complex. Two additional sources worth considering as far as implications for the end-to-end model are concerned are [Tussle in Cyberspace] and [Rethinking the Internet]. In [Tussle in Cyberspace], the authors note concerns regarding the introduction of new control points, as well as "kludges" to the DNS, as risks to the goal of network transparency in the end-to-end model. Some parties concerned with the emerging use of DNS whitelisting have shared similar concerns, which may make [Tussle in Cyberspace] an interesting and relevant document. In addition, [Rethinking the Internet] reviews similar issues that may be of interest to readers of this document. Also, it is possible that DNS whitelisting could affect some of the architectural assumptions which underlie parts of Section 2 of [RFC4213] which outlines the dual stack approach to the IPv6 transition. DNS whitelisting could modify the behavior of the DNS, as described in Section 2.2 of [RFC4213] and could require different sets of DNS servers to be used for hosts that are (using terms from that document) IPv6/IPv4 nodes, IPv4-only nodes, and IPv6-only nodes. As such, broad use of DNS whitelisting may necessitate the review and/or revision of standards documents which describe dual-stack and IPv6 operating modes, dual-stack architecture generally, and IPv6 transition methods, including but not limited to [RFC4213]. 7.2. Public IPv6 Address Reachability Implications The predominant experience of end user hosts and servers on the IPv4- addressed Internet today is that when a new server with a public IPv4 address is added to the DNS, that it is then globally accessible by IPv4-addressed hosts. This is a generalization and in Section 5 there are examples of common cases where this may not necessarily be the case. For the purposes of this argument, that concept of accessibility can be considered "pervasive reachability". It has so far been assumed that the same expectations of pervasive reachability would exist in the IPv6-addressed Internet. However, if DNS whitelisting is deployed, this will not be the case since only end user hosts using DNS recursive resolvers which are included in the Livingood Expires August 26, 2011 [Page 16] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 ACL of a given domain using DNS whitelisting would be able to reach new servers in that given domain via IPv6 addresses. The expectation of any end user host being able to connect to any server (essentially both hosts, just at either end of the network), defined here as "pervasive reachability", will change to "restricted reachability" with IPv6. Establishing DNS whitelisting as an accepted practice in the early phases of mass IPv6 deployment could well establish it as an integral part of how IPv6 DNS resource records are deployed globally. As a result, it is then possible that DNS whitelisting could live on for decades on the Internet as a key foundational element of domain name management that we will all live with for a long time. It is a critical to understand that the concept of reachability described above depends upon a knowledge or awareness of an address in the DNS. Thus, in order to establish reachability to an end point, a host is dependent upon looking up an IP address in the DNS when a FQDN is used. When DNS whitelisting is used, it is quite likely the case that an IPv6-enabled end user host could ping or connect to an example server host, even though the FQDN associated with that server host is restricted via a DNS whitelist. Since most Internet applications and hosts such as web servers depend upon the DNS, and as end users connect to FQDNs such as www.example.com and do not remember or wish to type in an IP address, the notion of reachability described here should be understood to include knowledge how to associate a name with a network address. 7.3. Operational Implications This section explores some of the operational implications which may occur as a result of, are related to, or become necessary when engaging in the practice of DNS whitelisting. 7.3.1. De-Whitelisting May Occur It is possible for a DNS recursive resolver added to a whitelist to then be removed from the whitelist, also known as de-whitelisting. Since de-whitelisting can occur, through a decision by the authoritative server operator, the domain owner, or even due to a technical error, an operator of a DNS recursive resolver will have new operational and monitoring requirements and/or needs as noted in Section 7.3.3, Section 7.3.4, Section 7.3.6, and Section 7.5. 7.3.2. Authoritative DNS Server Operational Implications Operators of authoritative servers may need to maintain an ACL a server-wide basis affecting all domains, on a domain-by-domain basis, Livingood Expires August 26, 2011 [Page 17] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 as well as on a combination of the two. As a result, operational practices and software capabilities may need to be developed in order to support such functionality. In addition, processes may need to be put in place to protect against inadvertently adding or removing IP addresses, as well as systems and/or processes to respond to such incidents if and when they occur. For example, a system may be needed to record DNS whitelisting requests, report on their status along a workflow, add IP addresses when whitelisting has been approved, remove IP addresses when they have been de-whitelisted, log the personnel involved and timing of changes, schedule changes to occur in the future, and to roll back any inadvertent changes. Operators may also need implement new forms of monitoring in order to apply change control, as noted briefly in Section 7.3.4. 7.3.3. DNS Recursive Resolver Server Operational Implications Operators of DNS recursive resolvers, which may include ISPs, enterprises, universities, governments, individual end users, and many other parties, are likely to need to implement new forms of monitoring, as noted briefly in Section 7.3.4. But more critically, such operators may need to add people, processes, and systems in order to manage large numbers of DNS whitelisting applications as part of their own IPv6 transition, for all domains that the end users of such servers are interested in now or in which they may be interested in the future. As anticipation of interesting domains is likely infeasible, it is more likely that operators may either choose to only apply to be whitelisted for a domain based upon one or more end user requests, or that they will attempt to do so for all domains that they can ascertain to be engaging in DNS whitelisting. When operators apply for DNS whitelisting for all domains, that may mean doing so for all registered domains. Thus, some system would have to be developed to discover whether each domain has been whitelisted or not, which is touched on in Section 6 and may vary depending upon whether DNS whitelisting is universally deployed or is deployed on an ad hoc basis. These operators (of recursive resolvers) will need to develop processes and systems to track the status of all DNS whitelisting applications, respond to requests for additional information related to these applications, determine when and if applications have been denied, manage appeals, and track any de-whitelisting actions. Given the large number of domains in existence, the ease with which a new domain can be added, and the continued strong growth in the numbers of new domains, readers should not underestimate the potential significance in personnel and expense that this could Livingood Expires August 26, 2011 [Page 18] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 represent for such operators. In addition, it is likely that systems and personnel may also be needed to handle new end user requests for domains for which to apply for DNS whitelisting, and/or inquiries into the status of a whitelisting application, reports of de- whitelisting incidents, general inquiries related to DNS whitelisting, and requests for DNS whitelisting-related troubleshooting by these end users. 7.3.4. Monitoring Implications Once a DNS recursive resolver has been whitelisted for a particular domain, then the operator of that DNS recursive resolver may need to implement monitoring in order to detect the possible loss of whitelisting status in the future. This DNS recursive resolver operator could configure a monitor to check for a AAAA response in the whitelisted domain, as a check to validate continued status on the DNS whitelist. The monitor could then trigger an alert if at some point the AAAA responses were no longer received, so that operations personnel could begin troubleshooting, as outlined in Section 7.3.6. Also, authoritative DNS server operators are likely to need to implement new forms of monitoring. In this case, they may desire to monitor for significant changes in the size of the whitelist within a certain period of time, which might be indicative of a technical error such as the entire ACL being removed. Authoritative nameserver operators may also wish to monitor their workflow process for reviewing and acting upon DNS whitelisting applications and appeals, potentially measuring and reporting on service level commitments regarding the time an application or appeal can remain at each step of the process, regardless of whether or not such information is shared with parties other than that authoritative DNS server operator. 7.3.5. Implications of Operational Momentum It seems plausible that once DNS whitelisting is implemented it will be very difficult to deprecate such technical and operational practices. This assumption is based in an understanding of human nature, not to mention physics. For example, as Sir Issac Newton noted, "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it" [Laws of Motion]. Thus, once DNS whitelisting is implemented it is quite likely that it would take considerable effort to deprecate the practice and remove it everywhere on the Internet - it will otherwise simply remain in place in perpetuity. To better illustrate this point, one could consider one example (of many) that there are many email servers continuing to attempt to query or otherwise check anti- Livingood Expires August 26, 2011 [Page 19] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 spam DNS blocklists which have long ago ceased to exist. 7.3.6. Troubleshooting Implications The implications of DNS whitelisted present many challenges, which have been detailed in Section 7. These challenges may negatively affect the end users' ability to troubleshoot, as well as that of DNS recursive resolver operators, ISPs, content providers, domain owners (where they may be different from the operator of the authoritative DNS server for their domain), and other third parties. This may make the process of determining why a server is not reachable significantly more complex. 7.3.7. Additional Implications If Deployed On An Ad Hoc Basis Additional implications, should this be deployed on an ad hoc basis, could include scalability problems relating to operational processes, monitoring, and ACL updates. In particular, it seems likely that as the number of domains that are using DNS whitelisting increases, as well as the number of IPv6-capable networks requesting to be whitelisted, that there is an increased likelihood of configuration and other operational errors, especially with respect to the ACLs themselves. It is unclear when and if it would be appropriate to change from whitelisting to blacklisting, and whether or how this could feasibly be coordinated across the Internet, which may be proposed or implemented on an ad hoc basis when a majority of networks (or allocated IPv6 address blocks) have been whitelisted. Finally, some parties implementing DNS whitelisting consider this to be a temporary measure. As such, it is not clear how these parties will judge the network conditions to have changed sufficiently to justify disabling DNS whitelisting and/or what the process and timing will be in order to discontinue this practice. One further potential implication is that an end user with only an IPv4 address, using a DNS resolver which has not been whitelisted by any domains, would not be able to get any AAAA resource records. In such a case, this could give that end user the incorrect impression that there is no IPv6-based content on the Internet since they are unable to discover any IPv6 addresses via the DNS. 7.4. Homogeneity May Be Encouraged A broad trend which has existed on the Internet appears to be a move towards increasing levels of heterogeneity. One manifestation of this is in an increasing number, variety, and customization of end user hosts, including home network, operating systems, client Livingood Expires August 26, 2011 [Page 20] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 software, home network devices, and personal computing devices. This trend appears to have had a positive effect on the development and growth of the Internet. A key facet of this that has evolved is the ability of the end user to connect any technically compliant device or use any technically compatible software to connect to the Internet. Not only does this trend towards greater heterogeneity reduce the control which is exerted in the middle of the network, described in positive terms in [Tussle in Cyberspace], [Rethinking the Internet], and [RFC3724], but it can also help to enable greater and more rapid innovation at the edges. An unfortunate implication of the adoption of DNS whitelisting may be the encouragement of a reversal of this trend, which would be a move back towards greater levels of homogeneity. In this case, a domain owner which has implemented DNS whitelisting may prefer greater levels of control be exerted over end user hosts (which broadly includes all types of end user software and hardware) in order to attempt to enforce technical standards relating to establishing certain IPv6 capabilities or the enforcing the elimination of or restriction of certain end user hosts. While the domain operator is attempting to protect, maintain, and/or optimize the end user experience for their domain, the collective result of many domains implementing DNS whitelisting, or even a few major domains (meaning domains which are a major destination of Internet traffic) implementing DNS whitelisting, may be to encourage a return to more homogenous and/or controlled end user hosts. This could have unintended side effects on and counter-productive implications for future innovation at the edges of the network. 7.5. Technology Policy Implications A key technology policy implication concerns the policies relating to the process of reviewing an application for DNS whitelisting, and the decision-making process regarding whitelisting for a domain. Important questions may include whether these policies have been fully and transparently disclosed, are non-discriminatory, and are not anti-competitive. A related implication is whether and what the process for appeals is, when a domain decides not to add a DNS recursive resolver to the whitelist. Key questions here may include whether appeals are allowed, what the process is, what the expected turn around time is, and whether the appeal will be handled by an independent third party or other entity/group. A further implications arises when de-whitelisting occurs. Questions that may naturally be raised in such a case include whether the criteria for de-whitelisting have been fully and transparently disclosed, are non-discriminatory, and are not anti-competitive. Additionally, the question of whether or not there was a cure period Livingood Expires August 26, 2011 [Page 21] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 available prior to de-whitelisting, during which troubleshooting activities, complaint response work, and corrective actions may be attempted, and whether this cure period was a reasonable amount of time. It is also conceivable that whitelisting and de-whitelisting decisions could be quite sensitive to concerned parties beyond the operator of the domain which has implemented DNS whitelisting and the operator of the DNS recursive resolver, including end users, application developers, content providers, advertisers, public policy groups, governments, and other entities, which may also seek to become involved in or express opinions concerning whitelisting and/or de-whitelisting decisions. Lastly, it is conceivable that any of these interested parties or other related stakeholders may seek redress outside of the process a domain has establishing for DNS whitelisting and de-whitelisting. A final concern is that decisions relating to whitelisting and de- whitelisting may occur as an expression of other commercial, governmental, and/or cultural conflicts, given the new control point which has be established with DNS whitelisting. For example, in one imagined scenario, a domain could withhold adding a network to their DNS whitelisting unless that network agreed to some sort of financial payment, legal agreement, agreement to sever a relationship with a competitor of the domain, etc. In another example, a music-oriented domain may be engaged in some sort of dispute with an academic network concerning copyright infringement concerns within that network, and may choose to de-whitelist that network as a negotiating technique in some sort of commercial discussion. In a final example, a major email domain may choose to de-whitelist a network due to that network sending some large volume of spam, which would have the effect of preventing other, end users on that network from using other, non-email-related applications within that domain. Thus, it seems possible that DNS whitelisting and de-whitelisting could become a vehicle for adjudicating other disputes, and that this may well have intended and unintended consequences for end users which are affected by such decisions and are unlikely to be able to express a strong voice in such decisions. 7.6. IPv6 Adoption Implications As noted in Section 4, the implications of DNS whitelisting may drive end users and/or networks to delay, postpone, or cancel adoption of IPv6, or to actively seek alternatives to it. Such alternatives may include the use of multi-layer network address translation (NAT) techniques like NAT444 [I-D.shirasaki-nat444], which these parties may decide to pursue on a long-term basis to avoid the perceived costs and aggravations related to DNS whitelisting. This could of Livingood Expires August 26, 2011 [Page 22] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 course come at the very time that the Internet community is trying to get these very same parties interested in IPv6 and motivated to begin the transition to IPv6. As a result, parties that are likely to be concerned over the negative implications of DNS whitelisting could logically be concerned of the negative effects that this practice could have on the adoption of IPv6 if it became widespread or was adopted by majors Internet domains or other major parties in the Internet ecosystem. At the same time, as noted in Section 3, some highly-trafficked domains may find the prospect of transitioning to IPv6 daunting without having some short-term ability to incrementally control the amount and source of IPv6 traffic to their domains. 8. Solutions This section outlines several possible solutions when considering DNS whitelisting and associated IPv6-related issues. 8.1. Implement DNS Whitelisting Universally One obvious solution is to implement DNS whitelisted universally, and to do so using some sort of centralized registry of DNS whitelisting policies, contracts, processes, or other information. This potential solution seems unlikely at the current time. 8.2. Implement DNS Whitelisting On An Ad Hoc Basis If DNS whitelisting is to be adopted, it is likely to be adopted on this ad hoc, or domain-by-domain basis. Therefore, only those domains interested in DNS whitelisting would need to adopt the practice, though as noted herein discovering that they a given domain has done so may be problematic. Also in this scenario, ad hoc use by a particular domain may be a temporary measure that has been adopted to ease the transition of the domain to IPv6 over some short-term timeframe. 8.3. Do Not Implement DNS Whitelisting As an alternative to adopting DNS whitelisting, the Internet community generally can choose to take no action whatsoever, perpetuating the current predominant authoritative DNS operational model on the Internet, and leave it up to end users with IPv6-related impairments to discover and fix those impairments. Livingood Expires August 26, 2011 [Page 23] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 8.3.1. Solving Current End User IPv6 Impairments A further extension of not implementing DNS whitelisting, is to also endeavor to actually fix the underlying technical problems that have prompted the consideration of DNS whitelisting in the first place, as an alternative to trying to apply temporary workarounds to avoid the symptoms of underlying end user IPv6 impairments. A first step is obviously to identify which users have such impairments, which would appear to be possible, and then to communicate this information to end users. Such end user communication is likely to be most helpful if the end user is not only alerted to a potential problem but is given careful and detailed advice on how to resolve this on their own, or where they can seek help in doing so. Section 11 may also be relevant in this case. One challenge with this option is the potential difficulty of motivating members of the Internet community to work collectively towards this goal, sharing the labor, time, and costs related to such an effort. Of course, since just such a community effort is now underway for IPv6, it is possible that this would call for only a moderate amount of additional work. Despite any potential challenges, many in the Internet community are already working towards this goal and/or have expressed a general preference for this approach. 8.3.2. Gain Experience Using IPv6 Transition Names Another alternative is for domains to gain experience using an FQDN which has become common for domains beginning the transition to IPv6; ipv6.example.com and www.ipv6.example.com. This can be a way for a domain to gain IPv6 experience and increase IPv6 use on a relatively controlled basis, and to inform any plans for DNS whitelisting with experience. 9. Is DNS Whitelisting a Recommended Practice? Opinions in the Internet community concerning whether or not DNS whitelisting is a recommended practice are understandably quite varied. However, there is clear consensus that DNS whitelisting is at best a useful temporary measure which a domain may choose to pursue as they prepare for the transition to IPv6. In particular, some major domains view DNS whitelisting as one of the few practical and low risk approaches enabling them to prepare for the transition to IPv6. Thus, DNS whitelisting is not a recommended practice over the long-term. In addition, DNS whitelisting should be avoided wherever possible in the short-term and its use is generally Livingood Expires August 26, 2011 [Page 24] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 discouraged. Nevertheless, major domains may find DNS whitelisting a beneficial temporary tactic in their transition to IPv6. Such temporary use during the transition to IPv6 is broadly accepted within the community, so long as it does not become a long-term practice. World IPv6 Day, sponsored by the Internet Society [World IPv6 Day], is scheduled to occur on June 8, 2011. This will be an opportunity for domains to add AAAA resource records to the DNS without using DNS whitelisting. As a result, this is likely an excellent opportunity for domains to evaluate the utility or necessity of DNS whitelisting, even in the short-term. A major German news website, Heise Online, also ran a similar IPv6 experiment whereby they added AAAA resource records and observed and measured any errors [Heise Online Experiment], which is important reading for any domain contemplating either the use of DNS whitelisting or simply adding IPv6 addressing to their site. 10. Security Considerations There are no particular security considerations if DNS whitelisting is not adopted, as this is how the public Internet works today with A resource records. However, if DNS whitelisting is adopted, organizations which apply DNS whitelisting policies in their authoritative servers should have procedures and systems which do not allow unauthorized parties to either remove whitelisted DNS resolvers from the whitelist or add non-whitelisted DNS resolvers to the whitelist. Should such unauthorized additions or removals from the whitelist can be quite damaging, and result in content providers and/or ISPs to incur substantial support costs resulting from end user and/or customer contacts. As such, great care must be taken to control access to the whitelist for an authoritative server. In addition, two other key security-related issues should be taken into consideration: 10.1. DNSSEC Considerations DNS security extensions defined in [RFC4033], [RFC4034], and [RFC4035] use cryptographic digital signatures to provide origin authentication and integrity assurance for DNS data. This is done by creating signatures for DNS data on a Security-Aware Authoritative Name Server that can be used by Security-Aware Resolvers to verify the answers. Since DNS whitelisting is implemented on an authoritative server, which provides different answers depending upon Livingood Expires August 26, 2011 [Page 25] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 which resolver server has sent a query, the DNSSEC chain of trust is not altered. Even though the authoritative server will not always return a AAAA resource record when one exists, respective A resource records and AAAA resource records can and should both be signed. Therefore there are no DNSSEC implications per se. However, any implementer of DNS whitelisting should be careful if they implement both DNSSEC signing of their domain and also DNS whitelisting of that same domain. Specifically, those domains should ensure that resource records are being appropriately and reliably signed, which may present incremental operational and/or technical challenges. However, as noted in Section 3, end user networks may also choose to implement tools at their disposal in order to address IPv6-related impairments. One of those possible tools could involve unspecified changes to the configuration of their recursive resolvers. If it is a Security-Aware Resolver, modifying or suppressing AAAA resource records for a DNSSEC-signed domain will be problematic and could break the chain of trust established with DNSSEC. 10.2. Authoritative DNS Response Consistency Considerations In addition to the considerations raised in Section 10.1, it is conceivable that security concerns may arise when end users or other parties notice that the responses sent from an authoritative DNS server appear to vary from one network or one DNS recursive resolver to another. This may give rise to concerns that, since the authoritative responses vary that there is some sort of security issue and/or some or none of the responses can be trusted. While this may seem a somewhat obscure concern, domains nonetheless may wish to consider this when contemplating whether or not to pursue DNS whitelisting. 11. Privacy Considerations As noted in Section 8.3.1, there may be methods to detect IPv6- related impairments for a particular end user. For example, this may be possible when an end user visits the website of a particular domain. In that example, there are likely no privacy considerations in communicating to that end user that the domain has detected a particular impairment. However, if that domain decided to share information concerning that particular end user with their network operator or another party, then the visited domain may wish to in some manner advise the end user of this or otherwise seek their consent to such information sharing. This may be achieved in a wide variety of ways, from presenting a message asking the user for consent (which will of course help them solve a technical problem of which they are likely unaware) to adding this to a domain's website Livingood Expires August 26, 2011 [Page 26] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 terms of use / service. Such information sharing and communication of such sharing to end users may well vary by geographic area and/or legal jurisdiction. Thus, a domain should consider any potential privacy issues these sorts of scenarios. 12. IANA Considerations There are no IANA considerations in this document. 13. Contributors The following people made significant textual contributions to this document and/or played an important role in the development and evolution of this document: - John Brzozowski - Chris Griffiths - Tom Klieber - Yiu Lee - Rich Woundy 14. Acknowledgements The author and contributors also wish to acknowledge the assistance of the following individuals. Some of these people provided helpful and important guidance in the development of this document and/or in the development of the concepts covered in this document. Other people assisted by performing a detailed review of this document, and then providing feedback and constructive criticism for revisions to this document. All of this was helpful and therefore the following individuals merit acknowledgement: - Bernard Aboba - Frank Bulk - Brian Carpenter - Karsten Fleischhauer - Wesley George Livingood Expires August 26, 2011 [Page 27] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 - Jerry Huang - Joel Jaeggli - Erik Kline - Suresh Krishnan - Victor Kuarsingh - Danny McPherson - Martin Millnert - Thomas Narten - Hannes Tschofenig - Tina Tsou 15. References 15.1. Normative References [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996. [RFC1958] Carpenter, B., "Architectural Principles of the Internet", RFC 1958, June 1996. [RFC2775] Carpenter, B., "Internet Transparency", RFC 2775, February 2000. [RFC2956] Kaat, M., "Overview of 1999 IAB Network Layer Workshop", RFC 2956, October 2000. [RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and Issues", RFC 3234, February 2002. [RFC3724] Kempf, J., Austein, R., and IAB, "The Rise of the Middle and the Future of End-to-End: Reflections on the Evolution of the Internet Architecture", RFC 3724, March 2004. Livingood Expires August 26, 2011 [Page 28] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, March 2005. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Resource Records for the DNS Security Extensions", RFC 4034, March 2005. [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Protocol Modifications for the DNS Security Extensions", RFC 4035, March 2005. [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms for IPv6 Hosts and Routers", RFC 4213, October 2005. 15.2. Informative References [Evaluating IPv6 Adoption] Colitti, L., Gunderson, S., Kline, E., and T. Refice, "Evaluating IPv6 adoption in the Internet", Passive and Active Management (PAM) Conference 2010, April 2010, . [Heise Online Experiment] Heise.de, "World IPv6 Day - June 8, 2011", Heise.de Website http://www.h-online.com, January 2011, . [I-D.shirasaki-nat444] Yamagata, I., Shirasaki, Y., Nakagawa, A., Yamaguchi, J., and H. Ashida, "NAT444", draft-shirasaki-nat444-03 (work in progress), January 2011. [IETF-77-DNSOP] Gashinsky, I., "IPv6 & recursive resolvers: How do we make the transition less painful?", IETF 77 DNS Operations Working Group, March 2010, . [IPv6 Brokenness] Anderson, T., "Measuring and Combating IPv6 Brokenness", Reseaux IP Europeens (RIPE) 61st Meeting, November 2011, . [IPv6 Whitelist Operations] Kline, E., "IPv6 Whitelist Operations", Google Google IPv6 Implementors Conference, June 2010, . [Laws of Motion] Newton, I., "Mathematical Principles of Natural Philosophy (Philosophiae Naturalis Principia Mathematica)", Principia Mathematical Principles of Natural Philosophy (Philosophiae Naturalis Principia Mathematica), July 1687, . [NW-Article-DNS-WL] Marsan, C., "Google, Microsoft, Netflix in talks to create shared list of IPv6 users", Network World , March 2010, . [NW-Article-DNSOP] Marsan, C., "Yahoo proposes 'really ugly hack' to DNS", Network World , March 2010, . [RFC1794] Brisco, T., "DNS Support for Load Balancing", RFC 1794, April 1995. [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, February 2000. [Resolvers in the Wild] Ager, B., Smaragdakis, G., Muhlbauer, W., and S. Uhlig, "Comparing DNS Resolvers in the Wild", ACM Sigcomm Internet Measurement Conference 2010, November 2010, . [Rethinking the Internet] Blumenthal, M. and D. Clark, "Rethinking the design of the Internet: The end to end arguments vs. the brave new world", ACM Transactions on Internet Technology Volume 1, Number 1, Pages 70-109, August 2001, . [Tussle in Cyberspace] Braden, R., Clark, D., Sollins, K., and J. Wroclawski, "Tussle in Cyberspace: Defining Tomorrow's Internet", Proceedings of ACM Sigcomm 2002, August 2002, . Livingood Expires August 26, 2011 [Page 30] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 [Whitelisting Concerns] Brzozowski, J., Griffiths, C., Klieber, T., Lee, Y., Livingood, J., and R. Woundy, "IPv6 DNS Whitelisting - Could It Hinder IPv6 Adoption?", ISOC Internet Society IPv6 Deployment Workshop, April 2010, . [World IPv6 Day] The Internet Society, "World IPv6 Day - June 8, 2011", Internet Society Website http://www.isoc.org, January 2011, . Appendix A. Document Change Log [RFC Editor: This section is to be removed before publication] -03: Several changes suggested by Joel Jaeggli at the end of WGLC. This involved swapping the order of Section 6.1 and 6.2, among other changes to make the document more readable, understandable, and tonally balanced. As suggested by Karsten Fleischhauer, added a reference to RFC 4213 in Section 7.1, as well as other suggestions to that section. As suggested by Tina Tsou, made some changes to the DNSSEC section regarding signing. As suggested by Suresh Krishnan, made several changes to improve various sections of the document, such as adding an alternative concerning the use of ipv6.domain, improving the system logic section, and shortening the reference titles. As suggested by Thomas Narten, added some text regarding the imperfection of making judgements as to end user host impairments based upon the recursive resolver's IP and/or network. Finally, made sure that variations in the use of 'records' and 'resource records' was updated to 'resource records' for uniformity and to avoid confusion. -02: Called for and closed out feedback on dnsop and v6ops mailing lists. Closed out open feedback items from IETF 79. Cleared I-D nits issues, added a section on whether or not this is recommended, made language less company-specific based on feedback from Martin Millnert, Wes George, and Victor Kuarsingh. Also mentioned World IPv6 Day per Wes George's suggestion. Added references to the ISOC World IPv6 Day and the Heise.de test at the suggestion of Jerry Huang, as well as an additional implication in 7.3.7. Made any speculation on IPv4 impairment noted explicitly as such, per feedback from Martin Millnert. Added a reference to DNS SRV in the load balancing section. Added various other references. Numerous changes suggested by John Brzozowski in several sections, to clean up the document. Moved up the section on why whitelisting is performed to Livingood Expires August 26, 2011 [Page 31] Internet-Draft IPv6 AAAA DNS Whitelisting Implications February 2011 make the document flow more logically. Added a note in the ad hoc deployment scenario explaining that a deployment may be temporary, and including more of the perceived benefits of this tactic. Added a Privacy Considerations section to address end-user detection and communication. -01: Incorporated feedback received from Brian Carpenter (from 10/19/ 2010), Frank Bulk (from 11/8/2010), and Erik Kline (from 10/1/2010). Also added an informative reference at the suggestion of Wes George (from from 10/22/2010). Closed out numerous editorial notes, and made a variety of other changes. -00: First version published as a v6ops WG draft. The preceding individual draft was draft-livingood-dns-whitelisting-implications-01. IMPORTANT TO NOTE that no changes have been made yet based on WG and list feedback. These are in queue for a -01 update. Appendix B. Open Issues [RFC Editor: This section is to be removed before publication] 1. Ensure references are in the proper section (normative/ informative) Author's Address Jason Livingood Comcast Cable Communications One Comcast Center 1701 John F. Kennedy Boulevard Philadelphia, PA 19103 US Email: jason_livingood@cable.comcast.com URI: http://www.comcast.com Livingood Expires August 26, 2011 [Page 32]