DNS Extensions Working Group R. Arends Internet-Draft Telematica Instituut Expires:
August 25, 2005April 26, 2006 P. Koch DENIC eG J. Schlyter NIC-SE February 21,October 23, 2005 Evaluating DNSSEC Transition Mechanisms draft-ietf-dnsext-dnssec-trans-02.txtdraft-ietf-dnsext-dnssec-trans-03.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 3 of RFC 3667.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 becomebecomes aware will be disclosed, in accordance with RFC 3668.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. 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 August 25, 2005.April 26, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document collects and summarizes different proposals for alternative and additional strategies for authenticated denial in DNS responses, evaluates these proposals and gives a recommendation for a way forward. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Transition Mechanisms . . . . . . . . . . . . . . . . . . . . 3 2.12.1. Mechanisms With Need of Updating DNSSEC-bis . . . . . . . 4 220.127.116.11.1. Dynamic NSEC Synthesis . . . . . . . . . . . . . . . . 4 18.104.22.168.2. Add Versioning/Subtyping to Current NSEC . . . . . . . 5 22.214.171.124.3. Type Bit Map NSEC Indicator . . . . . . . . . . . . . 6 126.96.36.199.4. New Apex Type . . . . . . . . . . . . . . . . . . . . 6 188.8.131.52.5. NSEC White Lies . . . . . . . . . . . . . . . . . . . 7 184.108.40.206.6. NSEC Optional via DNSSKEY Flag . . . . . . . . . . . . 8 220.127.116.11.7. New Answer Pseudo RR Type . . . . . . . . . . . . . . 9 2.1.8 SIG(0) Based Authenticated Denial . . . . . . . . . . 9 2.22.2. Mechanisms Without Need of Updating DNSSEC-bis . . . . . . 10 2.2.19 2.2.1. Partial Type-code and Signal Rollover . . . . . . . . 10 2.2.29 2.2.2. A Complete Type-code and Signal Rollover . . . . . . . 11 2.2.310 2.2.3. Unknown (New) Algorithm in DS, DNSKEY, and RRSIG . . . 11 2.2.4. Unknown (New) Hash Algorithm in DS . . . . . . . . . . . 1112 3. Recommendation . . . . . . . . . . . . . . . . . . . . . . . . 1213 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.15.1. Normative References . . . . . . . . . . . . . . . . . . . 13 5.25.2. Informative References . . . . . . . . . . . . . . . . . . 1314 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14. . 15 Intellectual Property and Copyright Statements . . . . . . . . 15. . 16 1. Introduction This report shall document the process of dealing with the NSEC walking problem late in the Last Call for [I-D.ietf-dnsext-dnssec-intro, I-D.ietf-dnsext-dnssec-protocol, I-D.ietf-dnsext-dnssec-records].[RFC4033], [RFC4034], and [RFC4035]. It preserves some of the discussion that took place in the DNSEXT WG during the first half of June 2004 as well as some additional ideas that came up subsequently. This is an edited excerpt of the chairs' mail to the WG: The working group consents on not including NSEC-alt in the DNSSEC-bis documents. The working group considers to take up "prevention of zone enumeration" as a work item. There may be multiple mechanisms to allow for co-existence with DNSSEC-bis. The chairs allow the working group a little over a week (up to June 12, 2004) to come to consensus on a possible modification to the document to enable gentle rollover. If that consensus cannot be reached the DNSSEC-bis documents will go out as-is. To ease the process of getting consensus, a summary of the proposed solutions and analysis of the pros and cons were written during the weekend. This summary includes: An inventory of the proposed mechanisms to make a transition to future work on authenticated denial of existence. List the known Pros and Cons, possibly provide new arguments, and possible security considerations of these mechanisms. Provide a recommendation on a way forward that is least disruptive to the DNSSEC-bis specifications as they stand and keep an open path to other methods for authenticated denial of existence. The descriptions of the proposals in this document are coarse and do not cover every detail necessary for implementation. In any case, documentation and further study is needed before implementaion and/or deployment, including those which seem to be solely operational in nature. 2. Transition Mechanisms In the light of recent discussions and past proposals, we have found several ways to allow for transition to future expansion of authenticated denial. We tried to illuminate the paths and pitfalls in these ways forward. Some proposals lead to a versioning of DNSSEC, where DNSSEC-bis may co-exist with DNSSEC-ter, other proposals are 'clean' but may cause delay, while again others may be plain hacks. Some paths do not introduce versioning, and might require the current DNSSEC-bis documents to be fully updated to allow for extensions to authenticated denial mechanisms. Other paths introduce versioning and do not (or minimally) require DNSSEC-bis documents to be updated, allowing DNSSEC-bis to be deployed, while future versions can be drafted independent from or partially depending on DNSSEC-bis. 2.12.1. Mechanisms With Need of Updating DNSSEC-bis Mechanisms in this category demand updates to the DNSSEC-bis document set. 18.104.22.168.1. Dynamic NSEC Synthesis This proposal assumes that NSEC RRs and the authenticating RRSIG will be generated dynamically to just cover the (non existent) query name. The owner name is (the) one preceding the name queried for, the Next Owner Name Field has the value of the Query Name Field + 1 (first successor in canonical ordering). A separate key (the normal ZSK or a separate ZSK per authoritative server) would be used for RRSIGs on NSEC RRs. This is a defense against enumeration, though it has the presumption of online signing. 22.214.171.124.1.1.1. Coexistence and Migration There is no change in interpretation other then that the next owner name might or might not exist. 126.96.36.199.1.1.2. Limitations This introduces an unbalanced cost between query and response generation due to dynamic generation of signatures. 188.8.131.52.1.1.3. Amendments to DNSSEC-bis The current DNSSEC-bis documents might need to be updated to indicate that the next owner name might not be an existing name in the zone. This is not a real change to the spec since implementers have been warned not to synthesize with previously cached NSEC records. A specific bit to identify the dynamic signature generating key might be useful as well, to prevent it from being used to fake positive data. 184.108.40.206.1.1.4. Cons Unbalanced cost is a ground for DDoS. Though this protects against enumeration, it is not really a path for versioning. 220.127.116.11.1.1.5. Pros Hardly any amendments to DNSSEC-bis. 18.104.22.168.2. Add Versioning/Subtyping to Current NSEC This proposal introduces versioning for the NSEC RR type (a.k.a. subtyping) by adding a (one octet) version field to the NSEC RDATA. Version number 0 is assigned to the current (DNSSEC-bis) meaning, making this an 'Must Be Zero' (MBZ) for the to be published docset. 22.214.171.124.1.2.1. Coexistence and Migration Since the versioning is done inside the NSEC RR, different versions may coexist. However, depending on future methods, that may or may not be useful inside a single zone. Resolvers cannot ask for specific NSEC versions but may be able to indicate version support by means of a to be defined EDNS option bit. 126.96.36.199.1.2.2. Limitations There are no technical limitations, though it will cause delay to allow testing of the (currently unknown) new NSEC interpretation. Since the versioning and signaling is done inside the NSEC RR, future methods will likely be restricted to a single RR type authenticated denial (as opposed to e.g. NSEC-alt, which currently proposes three RR types). 188.8.131.52.1.2.3. Amendments to DNSSEC-bis Full Update of the current DNSSEC-bis documents to provide for new fields in NSEC, while specifying behavior in case of unknown field values. 184.108.40.206.1.2.4. Cons Though this is a clean and clear path without versioning DNSSEC, it takes some time to design, gain consensus, update the current dnssec-bisdnssec- bis document, test and implement a new authenticated denial record. 220.127.116.11.1.2.5. Pros Does not introduce an iteration to DNSSEC while providing a clear and clean migration strategy. 18.104.22.168.3. Type Bit Map NSEC Indicator Bits in the type-bit-map are reused or allocated to signify the interpretation of NSEC. This proposal assumes that future extensions make use of the existing NSEC RDATA syntax, while it may need to change the interpretation of the RDATA or introduce an alternative denial mechanism, invoked by the specific type-bit-map-bits. 22.214.171.124.1.3.1. Coexistence and migration Old and new NSEC meaning could coexist, depending how the signaling would be defined. The bits for NXT, NSEC, RRSIG or other outdated RR types are available as well as those covering meta/query types or types to be specifically allocated. 126.96.36.199.1.3.2. Limitations This mechanism uses an NSEC field that was not designed for that purpose. Similar methods were discussed during the Opt-In discussion and the Silly-State discussion. 188.8.131.52.1.3.3. Amendments to DNSSEC-bis The specific type-bit-map-bits must be allocated and they need to be specified as 'Must Be Zero' (MBZ) when used for standard (dnssec-bis) interpretation. Also, behaviour of the resolver and validator must be documented in case unknown values are encountered for the MBZ field. Currently the protocol document specifies that the validator MUST ignore the setting of the NSEC and the RRSIG bits, while other bits are only used for the specific purpose of the type-bit-map field 184.108.40.206.1.3.4. Cons The type-bit-map was not designed for this purpose. It is a straightforward hack. Text in protocol section 5.4 was put in specially to defend against this usage. 220.127.116.11.1.3.5. Pros No change needed to the on-the-wire protocol as specified in the current docset. 18.104.22.168.4. New Apex Type This introduces a new Apex type (parallel to the zone's SOA) indicating the DNSSEC version (or authenticated denial) used in or for this zone. 22.214.171.124.1.4.1. Coexistence and Migration Depending on the design of this new RR type multiple denial mechanisms may coexist in a zone. Old validators will not understand and thus ignore the new type, so interpretation of the new NSEC scheme may fail, negative responses may appear 'bogus'. 126.96.36.199.1.4.2. Limitations A record of this kind is likely to carry additional feature/versioningfeature/ versioning indications unrelated to the current question of authenticated denial. 188.8.131.52.1.4.3. Amendments to DNSSEC-bis The current DNSSEC-bis documents need to be updated to indicate that the absence of this type indicates dnssec-bis, and that the (mere) presence of this type indicated unknown versions. 184.108.40.206.1.4.4. Cons The only other 'zone' or 'apex' record is the SOA record. Though this proposal is not new, it is yet unknown how it might fulfill authenticated denial extensions. This new RR type would only provide for a generalized signaling mechanism, not the new authenticated denial scheme. Since it is likely to be general in nature, due to this generality consensus is not to be reached soon. 220.127.116.11.1.4.5. Pros This approach would allow for a lot of other per zone information to be transported or signaled to both (slave) servers and resolvers. 18.104.22.168.5. NSEC White Lies This proposal disables one part of NSEC (the pointer part) by means of a special target (root, apex, owner, ...), leaving intact only the ability to authenticate denial of existence of RR sets, not denial of existence of domain names (NXDOMAIN). It may be necessary to have one working NSEC to prove the absence of a wildcard. 22.214.171.124.1.5.1. Coexistence and Migration The NSEC target can be specified per RR, so standard NSEC and 'white lie' NSEC can coexist in a zone. There is no need for migration because no versioning is introduced or intended. 126.96.36.199.1.5.2. Limitations This proposal breaks the protocol and is applicable to certain types of zones only (no wildcard, no deep names, delegation only). Most of the burden is put on the resolver side and operational consequences are yet to be studied. 188.8.131.52.1.5.3. Amendments to DNSSEC-bis The current DNSSEC-bis documents need to be updated to indicate that the NXDOMAIN responses may be insecure. 184.108.40.206.1.5.4. Cons Strictly speaking this breaks the protocol and doesn't fully fulfill the requirements for authenticated denial of existence. Security implications need to be carefully documented: search path problems (forged denial of existence may lead to wrong expansion of non-FQDNs [RFC1535]) and replay attacks to deny existence of records. 220.127.116.11.1.5.5. Pros Hardly any amendments to DNSSEC-bis. Operational "trick" that is available anyway. 18.104.22.168.6. NSEC Optional via DNSSKEY Flag A new DNSKEY may be defined to declare NSEC optional per zone. 22.214.171.124.1.6.1. Coexistence and Migration Current resolvers/validators will not understand the Flag bit and will have to treat negative responses as bogus. Otherwise, no migration path is needed since NSEC is simply turned off. 126.96.36.199.1.6.2. Limitations NSEC can only be made completely optional at the cost of being unable to prove unsecure delegations (absence of a DS RR [RFC3658]).RR). A next to this approach would just disable authenticated denial for non-existence of nodes. 188.8.131.52.1.6.3. Amendments to DNSSEC-bis New DNSKEY Flag to be defined. Resolver/Validator behaviour needs to be specified in the light of absence of authenticated denial. 184.108.40.206.1.6.4. Cons Doesn't fully meet requirements. Operational consequences to be studied. 220.127.116.11.1.6.5. Pros Official version of the "trick" presented in (8). Operational problems can be addressed during future work on validators. 18.104.22.168.7. New Answer Pseudo RR Type A new pseudo RR type may be defined that will be dynamically created (and signed) by the responding authoritative server. The RR in the response will cover the QNAME, QCLASS and QTYPE and will authenticate both denial of existence of name (NXDOMAIN) or RRset. 22.214.171.124.1.7.1. Coexistence and Migration Current resolvers/validators will not understand the pseudo RR and will thus not be able to process negative responses so testified. A signaling or solicitation method would have to be specified. 126.96.36.199.1.7.2. Limitations This method can only be used with online keys and online signing capacity. 188.8.131.52.1.7.3. Amendments to DNSSEC-bis Signaling method needs to be defined. 184.108.40.206.1.7.4. Cons Keys have to be held and processed online with all security implications. An additional flag for those keys identifying them as online or negative answer only keys should be considered. 220.127.116.11.1.7.5. Pros Expands DNSSEC authentication to the RCODE. 2.1.8 SIG(0) Based Authenticated Denial 18.104.22.168 Coexistence and Migration 22.214.171.124 Limitations 126.96.36.199 Amendments to DNSSEC-bis 188.8.131.52 Cons 184.108.40.206 Pros 2.22.2. Mechanisms Without Need of Updating DNSSEC-bis 220.127.116.11.1. Partial Type-code and Signal Rollover Carefully crafted type code/signal rollover to define a new authenticated denial space that extends/replaces DNSSEC-bis authenticated denial space. This particular path is illuminated by Paul Vixie in a Message-Id <20040602070859.0F50913951@sa.vix.com> posted to <email@example.com> 2004-06-02. 18.104.22.168.2.1.1. Coexistence and Migration To protect the current resolver for future versions, a new DNSSEC-OK bit must be allocated to make clear it does or does not understand the future version. Also, a new DS type needs to be allocated to allow differentiation between a current signed delegation and a 'future' signed delegation. Also, current NSEC needs to be rolled into a new authenticated denial type. 22.214.171.124.2.1.2. Limitations None. 126.96.36.199.2.1.3. Amendments to DNSSEC-bis None. 188.8.131.52.2.1.4. Cons It is cumbersome to carefully craft an TCR that 'just fits'. The DNSSEC-bis protocol has many 'borderline' cases that needs special consideration. It might be easier to do a full TCR, since a few of the types and signals need upgrading anyway. 184.108.40.206.2.1.5. Pros Graceful adoption of future versions of NSEC, while there are no amendments to DNSSEC-bis. 220.127.116.11.2. A Complete Type-code and Signal Rollover A new DNSSEC space is defined which can exist independent of current DNSSEC-bis space. This proposal assumes that all current DNSSEC type-codes (RRSIG/DNSKEY/NSEC/DS)(RRSIG/ DNSKEY/NSEC/DS) and signals (DNSSEC-OK) are not used in any future versions of DNSSEC. Any future version of DNSSEC has its own types to allow for keys, signatures, authenticated denial, etcetera. 18.104.22.168.2.2.1. Coexistence and Migration Both spaces can co-exist. They can be made completely orthogonal. 22.214.171.124.2.2.2. Limitations None. 126.96.36.199.2.2.3. Amendments to DNSSEC-bis None. 188.8.131.52.2.2.4. Cons With this path we abandon the current DNSSEC-bis. Though it is easy to role specific well-known and well-tested parts into the re-write, once deployment has started this path is very expensive for implementers, registries, registrars and registrants as well as resolvers/users. A TCR is not to be expected to occur frequently, so while a next generation authenticated denial may be enabled by a TCR, it is likely that that TCR will only be agreed upon if it serves a whole basket of changes or additions. A quick introduction of NSEC-ng should not be expected from this path. 184.108.40.206.2.2.5. Pros No amendments/changes to current DNSSEC-bis docset needed. It is always there as last resort. 220.127.116.11.3. Unknown (New) Algorithm in DS, DNSKEY, and RRSIG This proposal assumes that future extensions make use of the existing NSEC RDATA syntax, while itthey may need to change the interpretation of the RDATA or introduce an alternative denial mechanism, invoked by the specific unknown (new) signing algorithm. The different interpretation would be signaled by use of different signature algorithms in the RRSIG records coveringDS RR at the parent. Consequently, the DNSKEY RR for the child zone's KSK would contain a matching algorithm field. 18.104.22.168. Coexistence and migration Old and new NSEC RRs. When an entireRDATA interpretation or known and unknown signatures can NOT coexist in a zone since. While DS RRs with both new and well known algorithm designation could both exist at the parent, that would not lead to an unambiguous interpretation of the NSEC RRs in the zone. RRSIG RRs need to cover complete RRSets, so it is signednot possible to sign an 'old' NSEC RR with an RRSIG using an 'old' algorithm and then, at the same owner, sign another 'new' NSEC RR with an RRSIG of the 'new' algorithm type. 22.214.171.124. Limitations Validating resolvers agnostic of the 'new' signing algorithm (which may be a single unknownwell known algorithm, it will cause implementations that follow current dnssec-bis documentsbut might not be recognized due to the new code) will treat individual RRsetsthe entire zone as unsigned. 126.96.36.199insecure. The algorithm version space is split for each future version of DNSSEC. Violation of the 'modular components' concept. We use the 'validator' to protect the 'resolver' from unknown interpretations. 188.8.131.52. Amendments to DNSSEC-bis None. 184.108.40.206. Cons The algorithm field was not designed for this purpose. This is a straightforward hack. 220.127.116.11. Pros No amendments/changes to current DNSSEC-bis docset needed. 2.2.4. Unknown (New) Hash Algorithm in DS Similar to the previous method this one uses the DS RR at the parent to signal child zone properties. Here, the digest type field of the DS RR would be used to signal presence of a different (than DNSSEC- bis) authenticated denial scheme at the child. 18.104.22.168. Coexistence and migration Old and new NSEC RDATA interpretation or known and unknown Signaturessignatures can NOT coexist in a zone since signatures cover complete (NSEC) RRSets. 22.214.171.124zone. 126.96.36.199. Limitations Validating resolvers agnostic of the 'new' hashing algorithm (which may be a well known algorithm, but might not be recognized due to the new interpretationcode) will treat the NSEC RRset as "not signed". This affects wildcard and non-existence proof, as wellentire zone as proof for (un)secured delegations. Also, all positive signatures (RRSIGs on RRSets other than DS, NSEC) appear insecure/bogus to an old validator.insecure. The algorithm versiondigest type space is split for each future version of DNSSEC. Violation of the 'modular components' concept. We use the 'validator' to protect the 'resolver' from unknown interpretations. 188.8.131.52.2.4.3. Amendments to DNSSEC-bis None. 184.108.40.206.2.4.4. Cons The algorithmdigest type field was not designed for this purpose. This is a straightforward hack. 220.127.116.11.2.4.5. Pros No amendments/changes to current DNSSEC-bis docset needed. 3. Recommendation The authors recommend that the working group commits to and starts work on a partial TCR, allowing graceful transition towards a future version of NSEC. Meanwhile, to accomodate the need for an immediately, temporary, solution against zone-traversal, we recommend On-Demand NSEC synthesis. This approach does not require any mandatory changes to DNSSEC-bis, does not violate the protocol and fulfills the requirements. As a side effect, it moves the cost of implementation and deployment to the users (zone owners) of this mechanism. 4. Acknowledgements The authors would like to thank Sam Weiler and Mark Andrews for their input and constructive comments. 5. References 5.15.1. Normative References [I-D.ietf-dnsext-dnssec-intro] Arends, R., Austein, R., Massey, D., Larson, M. and S. Rose, "DNS Security Introduction and Requirements", Internet-Draft draft-ietf-dnsext-dnssec-intro-13, October 2004. [I-D.ietf-dnsext-dnssec-protocol] Arends, R., "Protocol Modifications for the DNS Security Extensions", Internet-Draft draft-ietf-dnsext-dnssec-protocol-09, October 2004. [I-D.ietf-dnsext-dnssec-records] Arends, R., "Resource Records for the DNS Security Extensions", Internet-Draft draft-ietf-dnsext-dnssec-records-11, October 2004.[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [RFC2931] Eastlake,[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS RequestSecurity Introduction and Transaction Signatures ( SIG(0)s)",Requirements", RFC 2931, September 2000. 5.24033, 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. 5.2. Informative References [RFC1535] Gavron, E., "A Security Problem and Proposed Correction With Widely Deployed DNS Software", RFC 1535, October 1993. [RFC2535] Eastlake, D., "Domain Name System Security Extensions", RFC 2535, March 1999. [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, June 1999. [RFC3658] Gudmundsson, O., "Delegation Signer (DS) Resource Record (RR)", RFC 3658, December 2003.Authors' Addresses Roy Arends Telematica Instituut Brouwerijstraat 1 Enschede 7523 XC The Netherlands Phone: +31 53 4850485 Email: firstname.lastname@example.org Peter Koch DENIC eG Wiesenh"uttenplatzWiesenhuettenplatz 26 Frankfurt 60329 Germany Phone: +49 69 27235 0 Email: pk@DENIC.DE Jakob Schlyter NIC-SE Box 5774 Stockholm SE-114 87 Sweden Email: email@example.com URI: http://www.nic.se/ Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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 firstname.lastname@example.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society.