Network Working Group P. Nikander Internet-Draft Ericsson Research Nomadic Lab Expires: August
20,28, 2006 J. Laganier DoCoMo Euro-Labs February 16,24, 2006 Host Identity Protocol (HIP) Domain Name System (DNS) Extensions draft-ietf-hip-dns-05draft-ietf-hip-dns-06 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 20,28, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document specifies a new resource record (RR) for the Domain Name System (DNS), and how to use it with the Host Identity Protocol (HIP.) This RR allows a HIP node to store in the DNS its Host Identity (HI, the public component of the node public-private key pair), Host Identity Tag (HIT, a truncated hash of its public key), and the Domain Names of its rendezvous servers (RVS.) Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . 4 3. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Simple static singly homed end-host . . . . . . . . . . . 6 3.2. Mobile end-host . . . . . . . . . . . . . . . . . . . . . 7 4. Overview of using the DNS with HIP . . . . . . . . . . . . . . 9 4.1. Storing HI, HIT and RVS in DNS . . . . . . . . . . . . . . 9 4.2. Initiating connections based on DNS names . . . . . . . . 9 5. HIP RR Storage Format . . . . . . . . . . . . . . . . . . . . 10 5.1. HIT length format . . . . . . . . . . . . . . . . . . . . 10 5.2. PK algorithm format . . . . . . . . . . . . . . . . . . . 10 5.3. PK length format . . . . . . . . . . . . . . . . . . . . . 11 5.4. HIT format . . . . . . . . . . . . . . . . . . . . . . . . 11 5.5. Public key format . . . . . . . . . . . . . . . . . . . . 11 5.6. Rendezvous servers format . . . . . . . . . . . . . . . . 11 6. HIP RR Presentation Format . . . . . . . . . . . . . . . . . . 12 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 8.1. Attacker tampering with an insecure HIP RR . . . . . . . . 14 8.2. Hash and HITs Collisions . . . . . . . . . . . . . . . . . 15 8.3. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 11.1. Normative references . . . . . . . . . . . . . . . . . . . 18 11.2. Informative references . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 Intellectual Property and Copyright Statements . . . . . . . . . . 21 1. Introduction This document specifies a new resource record (RR) for the Domain Name System (DNS) [RFC1034], and how to use it with the Host Identity Protocol (HIP) [I-D.ietf-hip-base]. This RR allows a HIP node to store in the DNS its Host Identity (HI, the public component of the node public-private key pair), Host Identity Tag (HIT, a truncated hash of its HI), and the Domain Names of its rendezvous servers (RVS.) [I-D.ietf-hip-rvs] Currently, most of the Internet applications that need to communicate with a remote host first translate a domain name (often obtained via user input) into one or more IP address(es). This step occurs prior to communication with the remote host, and relies on a DNS lookup. With HIP, IP addresses are intended to be used mostly for on-the-wire communication between end hosts, while most ULPs and applications use HIs or HITs instead (ICMP might be an example of an ULP not using them.) Consequently, we need a means to translate a domain name into an HI. Using the DNS for this translation is pretty straightforward: We define a new HIP resource record. Upon query by an application or ULP for a FQDN -> IP lookup, the resolver would then additionally perform an FQDN -> HI lookup, and use it to construct the resulting HI -> IP mapping (which is internal to the HIP layer.) The HIP layer uses the HI -> IP mapping to translate HIs and HITs into IP addresses and vice versa. The HIP rendezvous extensions [I-D.ietf-hip-rvs] proposal allows a HIP node to be reached via the IP address(es) of a third party, the node's rendezvous server (RVS.) An initiator willing to establish a HIP association with a responder served by a RVS would typically initiate a HIP exchange by sending an I1 towards the RVS IP address rather than towards the responder IP address. Consequently, we need a means to translate a domain name into the rendezvous server's domain name. This draft introduces the new HIP DNS Resource Record to store Rendezvous Server (RVS), Host Identity (HI) and Host Identity Tag (HIT) information. 2. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119 [RFC2119]. 3. Usage Scenarios In this section, we briefly introduce a number of usage scenarios where the DNS is useful with the Host Identity Protocol. With HIP, most application and ULPs are unaware of the IP addresses used to carry packets on the wire. Consequently, a HIP node could take advantage of having multiple IP addresses for fail-over, redundancy, mobility, or renumbering, in a manner which is transparent to most ULPs and applications (because they are bound to HIs, hence they are agnostic to these IP address changes.) In these situations, a node wishing to be reachable by reference to its FQDN should store the following information in the DNS: o A set of IP address(es) through A and AAAA RRs. o A Host Identity (HI), Host Identity Tag (HIT) and possibly a set of rendezvous server(s) (RVS) through HIP RRs. When a HIP node wants to initiate a communication with another HIP node, it first needs to perform a HIP base exchange to set-up a HIP association towards its peer. Although such an exchange can be initiated opportunistically, i.e., without prior knowledge of the responder's HI, by doing so both nodes knowingly risk man-in-the- middle attacks on the HIP exchange. To prevent these attacks, it is recommended that the initiator first obtain the HI of the responder, and then initiate the exchange. This can be done, for example, through manual configuration or DNS lookups. Hence, a new HIP RR is introduced. When a HIP node is frequently changing its IP address(es), the dynamic DNS update latency may prevent it from publishing its new IP address(es) in the DNS. For solving this problem, the HIP architecture introduces rendezvous servers (RVS.) A HIP host uses a rendezvous server as a rendezvous point, to maintain reachability with possible HIP initiators. Such a HIP node would publish in the DNS its RVS domain name(s) in a HIP RR, while keeping its RVS up-to- date with its current set of IP addresses. When a HIP node wants to initiate a HIP exchange with a responder it will perform a number of DNS lookups. Depending on the type of the implementation, the order in which those lookups will be issued may vary. For instance, implementations using HIT in APIS may typically first query for HIP resource records at the responder FQDN, while those using IP address in APIs may typically first query for A and/or AAAA resource records. In the following we assume that the initiator first queries for HIP resource records at the responder FQDN. If the query for the HIP type was responded to with a DNS answer with RCODE=3 (Name Error), then the responder's information is not present in the DNS and further queries SHOULD NOT be made. In case the query for the HIP records returned a DNS answer with RCODE=0 (No Error), then the initiator sends out one more query for for A and AAAA types at the responder's FQDN. Depending on the combinations of answer the situations described in Section 3.1 and Section 3.2 can occur. Note that storing HIP RR information in the DNS at a FQDN which is assigned to a non-HIP node might have ill effects on its reachability by HIP nodes. 3.1. Simple static singly homed end-host A HIP node (R) with a single static network attachment, wishing to be reachable by reference to its FQDN (www.example.com), would store in the DNS, in addition to its IP address(es) (IP-R), its Host Identity (HI-R) and Host Identity Tag (HIT-R) in a HIP resource record. An initiator willing to associate with a node would typically issue the following queries: QNAME=www.example.com, QTYPE=HIP (QCLASS=IN is assumed and omitted from the examples) Which returns a DNS packet with RCODE=0 and one or more HIP RRs with the HIT and HI (e.g. HIT-R and HI-R) of the responder in the answer section, but no RVS. QNAME=www.example.com, QTYPE=A Which returns a DNS packet with RCODE=0 and one or more A or AAAA RRs containing IP address(es) of the responder (e.g. IP-R) in the answer section. Caption: In the remainder of this document, for the sake of keeping diagrams simple and concise, several DNS queries and answers are represented as one single transaction, while in fact there are several queries and answers flowing back and forth, as described in the textual examples. [HIP? A? ] [www.example.com] +-----+ +-------------------------------->| | | | DNS | | +-------------------------------| | | | [HIP? A? ] +-----+ | | [www.example.com] | | [HIP HIT-R HI-R ] | | [A IP-R ] | v +-----+ +-----+ | |--------------I1------------->| | | I |<-------------R1--------------| R | | |--------------I2------------->| | | |<-------------R2--------------| | +-----+ +-----+ The initiator would then send an I1 to the responder's IP addresses (IP-R.) 3.2. Mobile end-host A mobile HIP node (R) wishing to be reachable by reference to its FQDN (www.example.com) would store in the DNS, possibly in addition to its IP address(es) (IP-R), its HI (HI-R), HIT (HIT-R) and the domain name(s) of its rendezvous server(s) (rvs.example.com) in HIP resource record(s). The mobile HIP node also needs to notify its rendezvous servers of any change in its set of IP address(es). An initiator willing to associate with such mobile node would typically issue the following queries: QNAME=www.example.com, QTYPE=HIP Which returns a DNS packet with RCODE=0 and one or more HIP RRs with the HIT, HI and RVS domain name(s) (e.g. HIT-R, HI-R, and rvs.example.com) of the responder in the answer section. QNAME=rvs.example.com, QTYPE=A Which returns a DNS packet with RCODE=0 and one or more A or AAAA RRs containing IP address(es) of the responder's RVS (e.g. IP-RVS) in the answer section. [HIP? ] [www.example.com] [A? ] [rvs.example.com] +-----+ +----------------------------------------->| | | | DNS | | +----------------------------------------| | | | [HIP? ] +-----+ | | [www.example.com ] | | [HIP HIT-R HI-R rvs.example.com] | | | | [A? ] | | [rvs.example.com] | | [A IP-RVS ] | | | | +-----+ | | +------I1----->| RVS |-----I1------+ | | | +-----+ | | | | | | | | | | v | v +-----+ +-----+ | |<---------------R1------------| | | I |----------------I2----------->| R | | |<---------------R2------------| | +-----+ +-----+ The initiator would then send an I1 to the RVS IP address (IP-RVS.) Following, the RVS will relay the I1 up to the mobile node's IP address (IP-R), which will complete the HIP exchange. 4. Overview of using the DNS with HIP 4.1. Storing HI, HIT and RVS in DNS Any conforming implementation may store a Host Identity (HI) and its associated Host Identity Tag (HIT) in a DNS HIP RDATA format. If a particular form of an HI does not already have a specified RDATA format, a new RDATA-like format SHOULD be defined for the HI. HI and HIT are defined in Section 3 of [I-D.ietf-hip-base]. Upon return of a HIP RR, a host MUST always calculate the HI- derivative HIT to be used in the HIP exchange, as specified in Section 3 of the HIP base specification [I-D.ietf-hip-base], while the HIT possibly embedded along SHOULD only be used as an optimization (e.g. table lookup.) The HIP resource record may also containscontain one or more domain name(s) of rendezvous server(s) towards which HIP I1 packets might be sent to trigger the establishment of an association with the entity named by this resource record [I-D.ietf-hip-rvs]. The rendezvous server field of the HIP resource record stored at a given domain name MAY include the domain name itself. A semantically equivalent situation occurs if no rendezvous server is stored in the HIP resource record of that domain. Such situations occurs in two cases: o The host is mobile, and the A and/or AAAA resource record(s) stored at its domain name contains the IP address(es) of its rendezvous server rather than its own one. o The host is stationary, and can be reached directly at IP address(es) contained in A and/or AAAA resource record(s) stored at its domain name. This a degenerated case of rendezvous service where the host somewhat acts as a rendezvous server for itself. An RVS receiving such an I1 would then relay it to the appropriate responder (the owner of the I1 receiver HIT.) The responder will then complete the exchange with the initiator, typically without ongoing help from the RVS. 4.2. Initiating connections based on DNS names On a HIP node, a Host Identity Protocol exchange SHOULD be initiated whenever an Upper Layer Protocol attemptattempts to communicate with an entity and the DNS lookup returns HIP resource records. 5. HIP RR Storage Format The RDATA for a HIP RR consists of a public key algorithm type, the HIT length, a HIT, a public key, and optionnallyoptionally one or more rendezvous server(s). 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | HIT length | PK algorithm | PK length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ HIT ~ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | +-+-+-+-+-+-+-+-+-+-+-+ + | Public Key | ~ ~ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | ~ Rendezvous Servers ~ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+ The HIT length, PK algorithm, PK length, HIT and Public Key field are REQUIRED. The Rendezvous Servers field is OPTIONAL. 5.1. HIT length format The HIT length indicates the length in bytes of the HIT field. This is an 8 bits unsigned integer. 5.2. PK algorithm format The PK algorithm field indicates the public key cryptographic algorithm and the implied public key field format. This is an 8 bits unsigned integer. This document reuses the values defined for the 'algorithm type' of the IPSECKEY RR [RFC4025] 'gateway type' field. The presently defined values are shown here for reference: 1 A DSA key is present, in the format defined in RFC2536 [RFC2536]. 2 A RSA key is present, in the format defined in RFC3110 [RFC3110]. 5.3. PK length format The PK length indicates the length in bytes of the Public key field. This is a 16 bits unsigned integer in network byte order. 5.4. HIT format The HIT is stored, as a binary value, in network byte order. 5.5. Public key format Both of the public key types defined in this document (RSA and DSA) reuse the public key formats defined for the IPSECKEY RR [RFC4025] (which in turns contains the algorithm-specific portion of the KEY RR RDATA, all of the KEY RR DATA after the first four octets, corresponding to the same portion of the KEY RR that must be specified by documents that define a DNSSEC algorithm.) In the future, if a new algorithm is to be used both by IPSECKEY RR and HIP RR, it should use the same public key encoding for both RRs. Unless specified otherwise, the HIP RR public key field SHOULD use the same public key format as the IPSECKEY RR RDATA for the corresponding algorithm. The DSA key format is defined in RFC2536 [RFC2536]. The RSA key format is defined in RFC3110 [RFC3110] and the RSA key size limit (4096 bits) is relaxed in the IPSECKEY RR [RFC4025] specification. 5.6. Rendezvous servers format The Rendezvous servers field indicates one or more variable length wire-encoded domain names rendezvous server(s), as described in Section 3.3 of RFC1035 [RFC1035]. The wire-encoded format is self- describing, so the length is implicit. The domain names MUST NOT be compressed. The rendezvous server(s) are listed in order of preference (i.e. first rendezvous server(s) are preferred). 6. HIP RR Presentation Format This section specifies the representation of the HIP RR in a zone data master file. The HIT length field is not represented as it is implicitly known thanks to the HIT field representation. The PK algorithm field is represented as unsigned integers. The PK length field is not represented as it is implicitly known thanks to the Public key field representation. The HIT field is represented as the Base16 encoding [RFC3548] (a.k.a. hex or hexadecimal) of the HIT. The encoding MUST NOT contain whitespace(s). The Public Key field is represented as the Base64 encoding [RFC3548] of the public key. The encoding MAY contain whitespace(s), and such whitespace(s) MUST be ignored. The Rendezvous servers field is represented by one or more uncompressed domain name(s) The complete representation of the HPIHI record is: IN HIP ( pk-algorithm base16-encoded-hit base64-encoded-public-key rendezvous-server ... rendezvous-server[n] ) 7. Examples Example of a node with HI and HIT but no RVS: www.example.comwww.example.com. IN HIP ( 2 2A20E0FF0FE8A52422D059FFFEA938A1 AB3NzaC1kc3MAAACBAOBhKn TCPOuFBzZQX/N3O9dm9P9iv UIMoId==4009D9BA7B1A74DF365639CC39F1D578 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIv M4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy 87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRG Qb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48A WkskmdHaVDP4BcelrTI3rMXdXF5D ) Example of a node with a HI, HIT and one RVS: www.example.comwww.example.com. IN HIP ( 2 2A20E0FF0FE8A52422D059FFFEA938A1 AB3NzaC1kc3MAAACBAOBhKn TCPOuFBzZQX/N3O9dm9P9iv UIMoId==4009D9BA7B1A74DF365639CC39F1D578 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIv M4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy 87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRG Qb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48A WkskmdHaVDP4BcelrTI3rMXdXF5D rvs.example.com ) Example of a node with a HI, HIT and two RVS: www.example.comwww.example.com. IN HIP ( 2 2A20E0FF0FE8A52422D059FFFEA938A1 AB3NzaC1kc3MAAACBAOBhKn TCPOuFBzZQX/N3O9dm9P9iv UIMoId==4009D9BA7B1A74DF365639CC39F1D578 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIv M4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy 87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRG Qb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48A WkskmdHaVDP4BcelrTI3rMXdXF5D rvs1.example.com rvs2.example.com ) 8. Security Considerations Though the security considerations of the HIP DNS extensions still need to be more investigated and documented, this section contains a description of the known threats involved with the usage of the HIP DNS extensions. In a manner similar to the IPSECKEY RR [RFC4025], the HIP DNS Extensions allows to provision two HIP nodes with the public keying material (HI) of their peer. These HIs will be subsequently used in a key exchange between the peers. Hence, the HIP DNS Extensions introduce the same kind of threats that IPSECKEY does, plus threats caused by the possibility given to a HIP node to initiate or accept a HIP exchange using "opportunistic" or "unpublished initiator HI" modes. A HIP node SHOULD obtain HIP RRs from a trusted party trough a secure channel insuring proper data integrity of the RRs. DNSSEC [RFC2065] provides such a secure channel. In the absence of a proper secure channel, both parties are vulnerable to MitM and DoS attacks, and unrelated parties might be subject to DoS attacks as well. These threats are described in the following sections. 8.1. Attacker tampering with an insecure HIP RR The HIP RR contains public keying material in the form of the named peer's public key (the HI) and its secure hash (the HIT.) Both of these are not sensitive to attacks where an adversary gains knowledge of them. However, an attacker that is able to mount an active attack on the DNS, i.e., tampers with this HIP RR (e.g. using DNS spoofing) is able to mount Man-in-the-Middle attacks on the cryptographic core of the eventual HIP exchange (responder's HIP RR rewritten by the attacker.) The HIP RR may contain a rendezvous server domain name resolved into a destination IP address where the named peer is reachable by an I1 (HIP Rendezvous Extensions IPSECKEY RR [I-D.ietf-hip-rvs].) Thus, an attacker able to tamper with this RR is able to redirect I1 packets sent to the named peer to a chosen IP address, for DoS or MitM attacks. Note that this kind of attack is not specific to HIP and exists independently to whether or not HIP and the HIP RR are used. Such an attacker might tamper with A and AAAA RRs as well. An attacker might obviously use these two attacks in conjunction: It will replace the responder's HI and RVS IP address by its owns in a spoofed DNS packet sent to the initiator HI, then redirect all exchanged packets to him and mount a MitM on HIP. In this case HIP won't provide confidentiality nor initiator HI protection from eavesdroppers. 8.2. Hash and HITs Collisions As many cryptographic algorithm, some secure hashes (e.g. SHA1, used by HIP to generate a HIT from an HI) eventually become insecure, because an exploit has been found in which an attacker with a reasonable computation power breaks one of the security features of the hash (e.g. its supposed collision resistance.) This is why a HIP end-node implementation SHOULD NOT authenticate its HIP peers based solely on a HIT retrieved from DNS, but SHOULD rather use HI-based authentication. 8.3. DNSSEC In the absence of DNSSEC, the HIP RR is subject to the threats described in RFC 3833 [RFC3833]. 9. IANA Considerations IANA should allocate one new RR type code (TBD, 55?) for the HIP RR from the standard RR type space. IANA does not need to open a new registry for public key algorithms of the HIP RR because the HIP RR reuses "algorithms types" defined for the IPSECKEY RR [RFC4025]. The presently defined values are shown here for reference: 0 is reserved 1 is RSA 2 is DSA 10. Acknowledgments As usual in the IETF, this document is the result of a collaboration between many people. The authors would like to thanks the author (Michael Richardson), contributors and reviewers of the IPSECKEY RR [RFC4025] specification, which this document was framed after. The authors would also like to thanks the following people, who have provided thoughtful and helpful discussions and/or suggestions, that have helped improving this document: Jeff Ahrenholz, Rob Austein, Hannu Flinck, Tom Henderson, Olaf Kolkman, Miika Komu, Andrew McGregor, Erik Nordmark, and Gabriel Montenegro. Some parts of this draft stem from [I-D.ietf-hip-base]. Julien Laganier is partly funded by Ambient Networks, a research project supported by the European Commission under its Sixth Framework Program. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Ambient Networks project or the European Commission. 11. References 11.1. Normative references [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. [RFC2065] Eastlake, D. and C. Kaufman, "Domain Name System Security Extensions", RFC 2065, January 1997. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2536] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System (DNS)", RFC 2536, March 1999. [RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS)", RFC 3110, May 2001. [RFC3363] Bush, R., Durand, A., Fink, B., Gudmundsson, O., and T. Hain, "Representing Internet Protocol version 6 (IPv6) Addresses in the Domain Name System (DNS)", RFC 3363, August 2002. [RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 3548, July 2003. [RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, "DNS Extensions to Support IP Version 6", RFC 3596, October 2003. [RFC4025] Richardson, M., "A Method for Storing IPsec Keying Material in DNS", RFC 4025, March 2005. [I-D.ietf-hip-base] Moskowitz, R., "Host Identity Protocol", draft-ietf-hip-base-04 (work in progress), October 2005. [I-D.ietf-hip-rvs] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) Rendezvous Extension", draft-ietf-hip-rvs-04 (work in progress), October 2005. 11.2. Informative references [I-D.ietf-hip-arch] Moskowitz, R. and P. Nikander, "Host Identity Protocol Architecture", draft-ietf-hip-arch-03 (work in progress), August 2005. [I-D.ietf-hip-mm] Nikander, P., "End-Host Mobility and Multihoming with the Host Identity Protocol", draft-ietf-hip-mm-02 (work in progress), July 2005. [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain Name System (DNS)", RFC 3833, August 2004. Authors' Addresses Pekka Nikander Ericsson Research Nomadic Lab JORVAS FIN-02420 FINLAND Phone: +358 9 299 1 Email: email@example.com Julien Laganier DoCoMo Communications Laboratories Europe GmbH Landsberger Strasse 312 Munich 80687 Germany Phone: +49 89 56824 231 Email: firstname.lastname@example.org URI: http://www.docomolab-euro.com/ 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. 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