Internet Engineering Task force Gabor Bajko Internet Draft Nokia Intended Status: Proposed Standard Subir Das Expires: June 25, 2009 Telcordia Technologies December 26, 2008 Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for IEEE 802.21 Mobility Services (MoS) Discovery draft-ietf-mipshop-mos-dhcp-options-09 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 June 25, 2009. Copyright Notice Copyright (c) 2008 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. Abstract This document defines a number of Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) options that contain a list of domain names or IP addresses that can be mapped to servers providing IEEE 802.21 G. Bajko & S Das Expires 06/25/09 [Page 1] Mobility Services DHCP Options December 2008 type of Mobility Service (MoS)[MSFD]. These Mobility Services are used to assist an MN in handover preparation (network discovery) and handover decision (network selection). The services addressed in this document are the Media Independent Handover Services defined in [IEEE802.21]. (1) 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 RFC-2119. (2) Terminology and abbreviations used in this document Mobility Services: a set of different services provided by the network to mobile nodes to facilitate handover preparation and handover decision. In this document, Mobility Services refer to the services defined in IEEE 802.21 specifications [IEEE802.21] Mobility Server: a network node providing Mobility Support Services. MIH: Media Independent Handover, as defined in [IEEE802.21]. MIH Service: IS, ES or CS type of service, as defined in [IEEE802.21] Table of Contents 1. Introduction .................................................2 2. DHCPv4 Options for MoS Discovery..............................3 2.1 Domain Name List........................................5 2.2 IPv4 Address List.......................................6 3. DHCPv6 Options for MoS Discovery..............................6 4. Option Usage..................................................8 4.1 Usage of DHCPv4 Options for MoS Discovery...............8 4.2 Usage of DHCPv6 Options for MoS Discovery...............9 5. Security Considerations .....................................10 6. IANA Considerations .........................................10 7. Acknowledgements ............................................11 8. References ..................................................11 8.1 Normative References ...................................11 8.2 Informative References .................................12 Author's Addresses .............................................12 Intellectual Property and Copyright Statements .................13 G. Bajko & S. Das Expires 06/25/09 [Page 2] Mobility Services DHCP Options December 2008 1. Introduction IEEE 802.21 [IEEE802.21] defines three distinct service types to facilitate link layer handovers across heterogeneous technologies: a) Information Services (IS) IS provides a unified framework to the higher layer entities across the heterogeneous network environment to facilitate discovery and selection of multiple types of networks existing within a geographical area, with the objective to help the higher layer mobility protocols to acquire a global view of heterogeneous networks and perform seamless handover across these networks. b) Event Services (ES) Events may indicate changes in state and transmission behavior of the physical, data link and logical link layers, or predict state changes of these layers. The Event Service may also be used to indicate management actions or command status on the part of the network or some management entity. c) Command Services (CS) The command service enables higher layers to control the physical, data link, and logical link layers. The higher layers may control the reconfiguration or selection of an appropriate link through a set of handover commands. In IEEE terminology these services are called Media Independent Handover (MIH) services. While these services may be co-located, the different pattern and type of information they provide does not necessitate the co-location. An MN may make use of any of these MIH service types separately or any combination of them [MSFD]. In practice a Mobility Server may not necessarily host all three of these MIH services together, thus there is a need to discover the MIH services types separately. This document defines new DHCPv4 and DHCPv6 options and sub-options called the MoS Discovery Option, which allows the MN to locate a Mobility Server which hosts the desired service type (i.e. IS, ES or CS) as defined in [IEEE802.21]. Apart from manual configuration, this is one of the possible solutions for locating a server providing Mobility Services. 2. DHCPv4 Option for MoS Discovery This section describes the MoS Discovery Option for DHCPv4. Whether the MN receives an MoS address from local or home network will depend on the actual network deployment [MSFD]. The MoS Discovery G. Bajko & S. Das Expires 06/25/09 [Page 3] Mobility Services DHCP Options December 2008 Option begins with a option code followed by a length and sub-options. The value of the length octet does not include itself or the option code. The option layout is depicted below: 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 Code | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Option 1 | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Option n | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option Code OPTION-IPv4-MoS (To Be Assigned) - 1 byte Length An 8-bit field indicating the length of the option excluding the 'Option Code' and the 'Length' fields Sub-options A series of DHCPv4 sub-options. When the total length of a MoS Discovery Option exceeds 254 octets, the procedure outlined in [RFC3396] MUST be employed to split the option into multiple, smaller options. A sub-option begins with a sub-option Type followed by a length and a `enc` field. The value of the length octet does not include itself or the Sub-opt Type field. There are two types of encodings, specified by the encoding byte ('enc') that follows the code byte. If the encoding byte has the value 0, it is followed by a list of domain names, as described below (Section 2.1). If the encoding byte has the value 1, it is followed by one or more IPv4 addresses (Section 2.2). All implementations MUST support both encodings. A DHCP server MUST NOT mix the two encodings in the same DHCP message, even if it sends two different instances of the same option. Attempts to do so would result in incorrect client behavior as DHCP processing rules call G. Bajko & S. Das Expires 06/25/09 [Page 4] Mobility Services DHCP Options December 2008 for the concatenation of multiple instances of an option into a single option prior to processing the option [RFC3396]. The sub-option layout is depicted below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-opt Type | length | enc | FQDN or . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . IP Address . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The sub-option Types are summarized below. +--------------+---------------+ | Sub-opt | Service | | Type* | Name | +==============+===============+ | 1 | IS | +--------------+---------------+ | 2 | ES | +--------------+---------------+ | 3 | IS and ES | +--------------+---------------+ | 4 | CS | +--------------+---------------+ | 5 | IS and CS | +--------------+---------------+ | 6 | ES and CS | +--------------+---------------+ | 7 | IS, CS and ES | +--------------+---------------+ *Note: The values `0` '8' to '255' are reserved and MUST NOT be used. 2.1 Domain Name List If the 'enc' byte has a value of 0, the encoding byte is followed by a sequence of labels, encoded according to Section 8 of [RFC3315], quoted below: So that domain names may be encoded uniformly, a domain name or a list of domain names is encoded using the technique described in section 3.1 of [RFC1035]. A domain name, or list of domain names, in DHCP MUST NOT be stored in compressed form, as described in section 4.1.4 of [RFC1035]. G. Bajko & S. Das Expires 06/25/09 [Page 5] Mobility Services DHCP Options December 2008 [RFC1035] encoding was chosen to accommodate future international- lized domain name mechanisms. The minimum length for this encoding is 3. The option MAY contain multiple domain names, but these should refer to the NAPTR records of different providers, rather than different A records within the same provider. That is, the use of multiple domain names is not meant to replace NAPTR and SRV records, but rather to allow a single DHCP server to indicate MIH servers operated by multiple providers. The client MUST try the records in the order listed, applying the mechanism described in [MoS-DNS] for each. The client only resolves the subsequent domain names if attempts to contact the first one failed or yielded no common transport protocols between the MN and the server. The sub-option for this encoding has the following format: Type Len enc DNS name of MoS server +-----+---+---+-----+-----+-----+-----+-----+-- |1..7 | n | 0 | s1 | s2 | s3 | s4 | s5 | ... +-----+---+---+-----+-----+-----+-----+-----+-- As an example, consider the case where the server wants to offer two MIH IS servers, "example.com" and "example.net". These would be encoded as follows: +----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ |1..7|27 | 0 | 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'c'|'o'|'m'| 0 | +----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+ | 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'n'|'e'|'t'| 0 | +---+---+---+---+---+---+---+---+---+---+---+---+---+ 2.2 IPv4 Address List If the 'enc' byte has a value of 1, the encoding byte is followed by a list of IPv4 addresses indicating appropriate MIH servers available to the MN. Servers MUST be listed in order of preference. Its minimum length is 5, and the length MUST be a multiple of 4 plus one. The sub-option for this encoding has the following format: G. Bajko & S. Das Expires 06/25/09 [Page 6] Mobility Services DHCP Options December 2008 Code Len enc IPv4 Address 1 IPv4 Address 2 +-----+---+---+-----+----+---+----+----+-- |1..7 | n | 1 | a1 | a2 |a3 | a4 | a1 | ... +-----+---+---+-----+----+---+----+----+-- 3. DHCPv6 Option for MoS discovery This section introduces new DHCPv6 option used for MoS discovery. Whether the MN receives an MoS address from local or home network will depend on the actual network deployment [MSFD]. The MoS Discovery Option begins with a option code followed by a length and sub-options. The value of the length octet does not include itself or the option code. The option layout is depicted below: 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 Code | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Option 1 | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Option n | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option Code OPTION-IPv6-MoS (To Be Assigned) - 2 bytes Length A 16-bit field indicating the length of the option excluding the 'Option Code' and the 'Length' fields. Sub-options A series of DHCPv6 sub-options. The sub-options follow the same format (except the Sub-opt Type and G. Bajko & S. Das Expires 06/25/09 [Page 7] Mobility Services DHCP Options December 2008 Length value) and 'enc' rules as described in Section 2. The value of the Sub-opt Type and Length are 2-octets and the Length does not include itself or the Sub-opt Type field. The sub-option layout is depicted below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | sub-opt Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | enc | FQDN or IP Address | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The sub-option Types are summarized below. +--------------+---------------+ | Sub-opt | Service | | Type* | Name | +==============+===============+ | 1 | IS | +--------------+---------------+ | 2 | ES | +--------------+---------------+ | 3 | IS and ES | +--------------+---------------+ | 4 | CS | +--------------+---------------+ | 5 | IS and CS | +--------------+---------------+ | 6 | ES and CS | +--------------+---------------+ | 7 | IS, CS and ES | +--------------+---------------+ *Note: The values `0` '8' to '65535' are reserved and MUST NOT be used. 4. Option Usage 4.1 Usage of DHCPv4 Options for MoS Discovery The requesting and sending of the proposed DHCPv4 option follow the rules for DHCP options in [RFC2131]. 4.1.1 Mobile Node behavior The mobile node may perform the MoS information discovery procedure either during initial association with a network or when the G. Bajko & S. Das Expires 06/25/09 [Page 8] Mobility Services DHCP Options December 2008 mobility service is required. It may also try to perform the MoS information discovery when it lacks the network information for MoS or needs to change the MoS for some reasons, for instance, to recover from the single point of failure of the existing MoS. In order to request an address of a MoS Server, the mobile node (DHCP client) MUST include a MoS Discovery Option into either a DHCPDISCOVER or DHCPINFORM message. The inserted MoS Discovery Option MUST include only one sub-option, with the Sub-opt Type that represents either the service or the union of the services the mobile host is interested in. 4.1.2 DHCP Server behavior When the DHCP server receives either a DHCPDISCOVER or DHCPINFORM message with a MOS Discovery Option, the DHCP server MUST always construct the response according to the sub-option code representing either the service or the union of services desired by the mobile node in the sub-option code field. The response message may contain the IP address or the FQDN of the MoS Server. If set of FQDNs in the response message turns out to be more than 256 bytes, the DHCP server should send a reduced list of FQDNs so that they fit into one sub option. In case that the server cannot find any Mobility Server satisfying the requested Sub-opt Type, the server MUST return the MoS Discovery Option with a sub-option by setting the Sub-opt Type to the requested Sub-opt Type and the length of the sub-option to 1. 4.2 DHCPv6 Options for MoS discovery The requesting and sending of the proposed DHCPv6 options follow the rules for DHCP options in [RFC3315]. 4.2.1 Mobile node behavior The mobile node may perform the MoS information discovery procedure either during initial association with a network or when the mobility service is required. It may also try to perform the MoS information discovery when it lacks the network information for MoS or needs to change the MoS for some reasons, for instance, to recover from the single point of failure of the existing MoS. In order to request an address of a Mobility Server, the mobile node(DHCP client) MUST include a MoS Discovery Option into either a REQUEST or an INFORMATION-REQUEST message. The inserted MoS Discovery Option MUST include only one sub-option, with the G. Bajko & S. Das Expires 06/25/09 [Page 9] Mobility Services DHCP Options December 2008 Sub-opt Type that represents either the service or the union of the services the mobile host is interested in. 4.2.2 DHCP Server behavior When the DHCP Server receives either a REQUEST or an INFORMATION- REQUEST message with a MoS Discovery Option, the DHCP server MUST always construct the response according to the sub-option code representing either the service or the union of services desired by the mobile node in the sub-option code field. The response message may contain the IP address or the FQDN of the desired MoS server. In case that the server cannot find any Mobility Server satisfying the requested Sub-opt Type, the server MUST return the MoS Discovery Option with a sub-option by setting the Sub-opt Type to the requested Sub-opt Type and the length of the sub-option to 1. 5. Security Considerations The security considerations in [RFC2131] apply. If an adversary manages to modify the response from a DHCP server or insert its own response, an MN could be led to contact a rogue Mobility Server, possibly one that then would provide wrong information, event or command for handover. It is recommended to use either DHCP authentication option described in [RFC3118] where available, or rely upon link layer security. This will also protect the denial of service attacks to DHCP servers. [RFC3118] provides mechanisms for both entity authentication and message authentication. 6. IANA Considerations This document defines one new DHCPv4 option as described in section 2. MoS Discovery Option for DHCPv4 (OPTION-IPv4-MoS) To Be Assigned This document creates a new registry for the Sub-Option field in the MoS DHCPv4 option called the "IEEE 802.21 Service Type" (Section 2). IS 1 ES 2 IS and ES 3 CS 4 IS and CS 5 ES and CS 6 G. Bajko & S. Das Expires 06/25/09 [Page 10] Mobility Services DHCP Options December 2008 IS, CS and ES 7 The values '0', '8' to '255' are reserved and MUST NOT be used. New values can be allocated by Standards Action or IESG approval. This document also defines one DHCPv6 option as described in section 3. MoS Discovery Option for DHCPv6 (OPTION-IPv6-MoS) To Be Assigned This document creates a new registry for the sub-option field in the MoS DHCPv6 option called the "IEEE 802.21 Service Type" (section 3). IS 1 ES 2 IS and ES 3 CS 4 IS and CS 5 ES and CS 6 IS, CS and ES 7 The values '0', '8' to '65535' are reserved and MUST NOT be used. New Values can be allocated via Standards Action as defined in [RFC5226]. 7. Acknowledgements Authors would like to acknowledge the following individuals for their valuable comments. Bernie Volz, Vijay Devarapalli, Alfred Hoenes, Telemaco Melia, and Yoshihiro Ohba 8. References 8.1 Normative References [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC3315] Dynamic Host Configuration Protocol for IPv6 (DHCPv6), Droms et al, July 2003 [RFC3118] Authentication for DHCP Messages, Droms et al, June 2001 G. Bajko & S. Das Expires 06/25/09 [Page 11] Mobility Services DHCP Options December 2008 [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long DHCP Options", RFC3396, November 2002. [RFC5226] T. Narten and H. Alvestrand, ?Guidelines for Writing an IANA Considerations Section in RFCs? , May 2008. [MSFD] T Melia, Ed., " Mobility Services Framework Design (MSFD)", draft-ietf-mipshop-mstp-solution-09.txt (Work in Progress). [MoS-DNS] Bajko, G., "Locating Mobility Servers", draft-ietf-mipshop-mos-dns-discovery-04.txt (Work in Progress), 8.2 Informative References [IEEE802.21] IEEE 802.21 Standard for Local and Metropolitan Area Networks: Media Independent Handover Services Authors' Addresses Gabor Bajko Nokia e-mail: gabor.bajko@nokia.com Subir Das Telcordia Technologies Inc. e-mail: subir@research.telcordia.com G. Bajko & S. Das Expires 06/25/09 [Page 12]