MIPSHOP WG Gabor Bajko Internet Draft Nokia Intended Status: Proposed Standard Subir Das Expires: April 17, 2009 Telcordia October 17, 2008 Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for Mobility Server (MoS) discovery draft-ietf-mipshop-mos-dhcp-options-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 October 19, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). 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 type of Mobility Services [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]. G. Bajko & S Das Expires 04/17/09 [Page 1] Mobility Services DHCP Options October 2008 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. Terminology and abbreviations used in this document Mobility Services: comprises of a set of different services provided by the network to mobile nodes to facilitate handover preparation and handover decision. 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 Content 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 .................................11 Author's Addresses .............................................11 Intellectual Property and Copyright Statements .................12 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 G. Bajko & S. Das Expires 03/07/09 [Page 2] Mobility Services DHCP Options September 2008 mobility protocols to acquire a global view of the 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 a new dhcpv4 option called MoS 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]. The MoS information type defines sub-options for different services. The document also defines DHCPv6 options that allow the MN to discover Mobility Servers hosting MIH services in different deployment scenarios. 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 option for DHCPv4. The MoS 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 | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G. Bajko & S. Das Expires 04/17/09 [Page 3] Mobility Services DHCP Options October 2008 | ... | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Option n | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option Code OPTION-IPv4-MoS (TBD) - 1 byte Length 1 byte Sub-options A series of DHCPv4 sub-options. When the total length of a MoS 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 option code. 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 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 . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G. Bajko & S. Das Expires 04/17/09 [Page 4] Mobility Services DHCP Options October 2008 +---------------------------------------------------------------+ . 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. Future sub-options may or may not use the above format. 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]. [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 different NAPTR records, rather than different A records. The client MUST try the records in the order listed, applying the mechanism described in [MoS-DNS] for each. The client only resolves G. Bajko & S. Das Expires 04/17/09 [Page 5] Mobility Services DHCP Options October 2008 the subsequent domain names if attempts to contact the first one failed or yielded no common transport protocols between the MN and the server. 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 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: 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]. G. Bajko & S. Das Expires 04/17/09 [Page 6] Mobility Services DHCP Options October 2008 The MoS 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 (TBD) - 2 bytes Length 2 bytes Sub-options A series of DHCPv6 sub-options. The sub-options follow the same format (except the length value) and 'enc' rules as described in Section 2. 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 . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G. Bajko & S. Das Expires 04/17/09 [Page 7] Mobility Services DHCP Options October 2008 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. Future sub-options may or may not use the above format. 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 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 acquire the MoS information, the mobile node MUST send either a DHCPDISCOVER or DHCPINFORM message to a subnet broadcast or a unicast server address, respectively. In this message the mobile node (DHCP client) MUST include the sub-opt Type for the MoS Discovery in the sub-options field. G. Bajko & S. Das Expires 04/17/09 [Page 8] Mobility Services DHCP Options October 2009 4.1.2 DHCP Server behavior When the DHCP server receives the DHCPDISCOVER or DHCPINFORM message with the MoS Discovery option in the options field, the DHCP server MUST follow the [RFC2131] logic to construct either a DHCPOFFER or DHCPACK message including the MoS Discovery option. The reply message may contain the IP address or the FQDN of the MoS Server. The DHCP server MUST always construct the response according to the Sub-opt Type requested by the DHCP client. In case that the server cannot find any MoS information for a specific MoS sub-opt Type, it MUST return the MoS 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 acquire the MoS address, the mobile node MUST send either a REQUEST or INFORMATION_REQUEST message to the All_DHCP_Servers multicast address. In this message the mobile node (DHCP client) MUST include the Option Code for the MoS Discovery option in the option_code. 4.2.2 DHCP Server behavior When the DHCP Server receives either REQUEST or INFORMATION-REQUEST message the DHCP server MUST follow the following logic to construct a REPLY message with the MoS Information option. If the DHCP server has the requested MoS information, it MUST include the information in the MoS Information option. The server may provide the matching information from the preconfigured information available locally. G. Bajko & S. Das Expires 04/17/09 [Page 9] Mobility Services DHCP Options September 2008 The DHCP server MUST always construct the response according to the Sub-Opt Type requested by the DHCP client. In case that the server cannot find any MoS information for a specific MoS type, it MUST return the MoS 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 Option for DHCPv4 (OPTION-IPv4-MoS) TBD This document creates a new registry for the Sub-Option field in the MoS DHCPv4 option called the "MoS Service Type" (Section 2). 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 '255' are reserved and MUST NOT be used. New values can be allocated by Standards Action or IESG approval. This document also defines new DHCPv6 options as described in section 3 G. Bajko & S. Das Expires 04/17/09 [Page 10] Mobility Services DHCP Options October 2008 MoS Option for DHCPv6 (OPTION-IPv6-MoS) TBD This document creates a new registry for the sub-option field in the MoS DHCPv6 option called the ?MoS 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 '255' are reserved and MUST NOT be used. New Values can be allocated by Standards Action or IESG approval. 7. Acknowledgements Authors would like to acknowledge the following individuals for their valuable comments. Vijay Devarapalli, Telemaco Melia, and Yoshihiro Ohba 8. References 8.1 Normative References [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long DHCP Options", RFC3396, November 2002. [RFC3118] Authentication for DHCP Messages, Droms et al, June 2001 [RFC3315] Dynamic Host Configuration Protocol for IPv6 (DHCPv6), Droms et al, July 2003 8.2 Informative References [IEEE802.21] IEEE 802.21 Standard for Local and Metropolitan Area Networks: Media Independent Handover Services G. Bajko & S. Das Expires 04/17/09 [Page 11] Mobility Services DHCP Options October 2008 [MoS-DNS] Bajko, G., "Locating Mobility Servers", draft-ietf-mipshop-mos-dns-discovery, (Work in Progress), May 2008. [MSFD] T Melia, Ed., " Mobility Services Framework Design (MSFD)", draft-ietf-mipshop-mstp-solution, (Work in Progress) Authors' Addresses Gabor Bajko Nokia e-mail: gabor.bajko@nokia.com Subir Das Telcordia Technologies Inc. e-mail: subir@research.telcordia.com Full Copyright Statement Copyright (C) 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. 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