A Dynamic Host Configuration Protocol (DHCP) based Location-to-Service Translation Protocol (LoST) Discovery Procedure
draft-ietf-ecrit-dhc-lost-discovery-03.txt

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 November 30, 2008.

Abstract

The Location-to-Service Translation Protocol (LoST) describes an XML-based protocol for mapping service identifiers and geospatial or civic location information to service contact Uniform Resource Locators (URLs). LoST servers can be located anywhere but a placement closer to the end host, e.g., in the access network, is desireable. Such a LoST server placement provides benefits in disaster situations with intermittent network connectivity regarding the resiliency of emergency service communication.

This document describes how a LoST client can discover a LoST server using the Dynamic Host Configuration Protocol (DHCP).

Table of Contents

1.  Introduction
2.  Terminology
3.  Domain Name Encoding
4.  LoST Server DHCPv4 Option
5.  LoST Server DHCPv6 Option
6.  Example
7.  IANA Considerations
    7.1.  IANA Consideration for DHCPv4 Option
    7.2.  IANA Consideration for DHCPv6 Option
8.  Security Considerations
9.  Acknowledgements
10.  References
    10.1.  Normative References
    10.2.  Informative References
§  Authors' Addresses
§  Intellectual Property and Copyright Statements

1.  Introduction

The Location-to-Service Translation Protocol (LoST) [I‑D.ietf‑ecrit‑lost] (Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, “LoST: A Location-to-Service Translation Protocol,” May 2008.) describes an XML-based protocol for mapping service identifiers and geospatial or civic location information to service contact Uniform Resource Locators (URLs).

In order to interact with a LoST server, the LoST client eventually needs to discover the server's IP address. Several mechanisms can be used to learn this address, including manual configuration. In environments where the access network itself either deploys a LoST server or knows a third party that operates a LoST server, DHCP can provide the end host with a domain name. This domain name is then used as input to the DNS-based resolution mechanism described in LoST [I‑D.ietf‑ecrit‑lost] (Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, “LoST: A Location-to-Service Translation Protocol,” May 2008.) that reuses the URI-enabled NAPTR specification (see [RFC4848] (Daigle, L., “Domain-Based Application Service Location Using URIs and the Dynamic Delegation Discovery Service (DDDS),” April 2007.)).

This document specifies a DHCPv4 and a DHCPv6 option that allows LoST clients to discover local LoST servers.

Section 2 (Terminology) provides terminology. Section 3 (Domain Name Encoding) shows the encoding of the domain name. Section 4 (LoST Server DHCPv4 Option) describes the DHCPv4 option while Section 5 (LoST Server DHCPv6 Option) describes the DHCPv6 option, with the same functionality. IANA and Security Considerations complete the document in Section 7 (IANA Considerations) and Section 8 (Security Considerations).

2.  Terminology

In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

Within this document, we use terminology from [RFC5012] (Schulzrinne, H. and R. Marshall, “Requirements for Emergency Context Resolution with Internet Technologies,” January 2008.) and [I‑D.ietf‑ecrit‑lost] (Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, “LoST: A Location-to-Service Translation Protocol,” May 2008.).

3.  Domain Name Encoding

This section describes the encoding of the domain name used in the DHCPv4 option shown in Section 4 (LoST Server DHCPv4 Option) and also used in the DHCPv6 option shown in Section 5 (LoST Server DHCPv6 Option).

The domain name is encoded according to Section 3.1 of RFC 1035 [RFC1035] (Mockapetris, P., “Domain names - implementation and specification,” November 1987.) whereby each label is represented as a one octet length field followed by that number of octets. Since every domain name ends with the null label of the root, a domain name is terminated by a length byte of zero. The high order two bits of every length octet MUST be zero, and the remaining six bits of the length field limit the label to 63 octets or less. To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less.

4.  LoST Server DHCPv4 Option

The LoST server DHCPv4 option carries a DNS (RFC 1035 [RFC1035] (Mockapetris, P., “Domain names - implementation and specification,” November 1987.)) fully-qualified domain name to be used by the LoST client to locate a LoST server.

The DHCP option for this encoding has the following format:

      Code    Len   LoST Server Domain Name
      +-----+-----+-----+-----+-----+-----+-----+----
      | TBD1|  n  |  s1 |  s2 |  s3 |  s4 | s5  |  ...
      +-----+-----+-----+-----+-----+-----+-----+----

The values s1, s2, s3, etc. represent the domain name labels in the domain name encoding. Note that the length field in the DHCPv4 option represents the length of the entire domain name encoding, whereas the length fields in the domain name encoding (see Section 3 (Domain Name Encoding)) is the length of a single domain name label.

   Code: OPTION_V4_LOST (TBD1)

   Len: Length of the 'LoST Server Domain Name' field
   in octets; variable.

   LoST server Domain Name: The domain name of the LoST
   server for the client to use.

A DHCPv4 client MAY request a LoST server domain name in an Parameter Request List option, as described in [RFC2131] (Droms, R., “Dynamic Host Configuration Protocol,” March 1997.).

The encoding of the domain name is described in Section 3 (Domain Name Encoding).

This option contains a single doamin name, and as such MUST contain precisely one root label.

5.  LoST Server DHCPv6 Option

This section defines a DHCPv6 option to carry a domain name.

The DHCPv6 option has the format shown in Figure 2 (DHCPv6 Option for LoST Server Domain Name List).

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      OPTION_V6_LOST           |         option-length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                LoST Server Domain Name                        |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code: OPTION_V6_LOST (TBD2)

   option-length: Length of the 'LoST Server Domain Name' field
   in octets; variable.

   LoST server Domain Name: The domain name of the LoST
   server for the client to use.

A DHCPv6 client MAY request a LoST server domain name in an Options Request Option (ORO), as described in [RFC3315] (Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, “Dynamic Host Configuration Protocol for IPv6 (DHCPv6),” July 2003.).

The encoding of the domain name is described in Section 3 (Domain Name Encoding).

This option contains a single doamin name, and as such MUST contain precisely one root label.

6.  Example

This section shows an example of a DHCPv4 option where the DHCP server wants to offer the "example.com" domain name to the client as input to the U-NAPTR LoST discovery procedure. This domain name would be encoded as follows:

+----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|TBD1|13 | 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'c'|'o'|'m'| 0 |
+----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

7.  IANA Considerations

7.1.  IANA Consideration for DHCPv4 Option

The following DHCPv4 option code for the Location-to-Service Translation Protocol (LoST) server option must be assigned by IANA:

    Option  Name            Value       Described in
    -----------------------------------------------
    OPTION_V4_LOST           TBD1         Section 4

7.2.  IANA Consideration for DHCPv6 Option

IANA is requested to assign the following DHCPv6 option codes for the Location-to-Service Translation Protocol (LoST) options:

    Option  Name            Value       Described in
    ------------------------------------------------
    OPTION_V6_LOST           TBD2         Section 5

8.  Security Considerations

If an adversary manages to modify the response from a DHCP server or insert its own response, a LoST client could be led to contact a rogue LoST server under the control of the adversary or be given an invalid address. These threats are documented in [RFC5069] (Taylor, T., Tschofenig, H., Schulzrinne, H., and M. Shanmugam, “Security Threats and Requirements for Emergency Call Marking and Mapping,” January 2008.). The security considerations in [RFC2131] (Droms, R., “Dynamic Host Configuration Protocol,” March 1997.), [RFC2132] (Alexander, S. and R. Droms, “DHCP Options and BOOTP Vendor Extensions,” March 1997.) and [RFC3315] (Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, “Dynamic Host Configuration Protocol for IPv6 (DHCPv6),” July 2003.) are applicable to this document.

With respect to the LoST security mechanisms please refer to [I‑D.ietf‑ecrit‑lost] (Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, “LoST: A Location-to-Service Translation Protocol,” May 2008.).

9.  Acknowledgements

The authors would like to thank Andrew Newton and Leslie Daigle for their draft review and Andy for the proposed simplifications.

Mark Stapp and David W. Hankins did the document review for the DHC working group as part of the joint working group last call.

We would like to thank Vijay K. Gurbani for the Gen-ART review. Furthermore, we would like to thank Russ Housley, Tim Polk, Jari Arkko, and Christian Vogt.

10.  References

10.1. Normative References

10.2. Informative References

Authors' Addresses

Full Copyright Statement

Copyright © The IETF Trust (2008).

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.

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, THE IETF TRUST 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.

Intellectual Property

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 ietf-ipr@ietf.org.