MIPSHOP WG Gabor Bajko Internet Draft Nokia Intended Status: Standards Track Subir Das Expires: May 18, 2008 Telcordia November 18, 2007 Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for Mobility Server (MoS) discovery draft-bajko-mos-dhcp-options-01 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 May 18, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document defines a number of Dynamic Host Configuration Protocol (DHCP-for-IPv4 and DHCP-for-IPv6) 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. These Mobility Services are used to assist an MN in handover preparation (network discovery) and handover decision (network selection). The services addressed by this document are the Media Independent Handover Services defined in [1]. Conventions used in this document G. Bajko Expires 02/20/08 [Page 1] Mobility Services DHCP Options August 2007 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 [1]. 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 [1]. MIH Service: IS, ES or CS type of service, as defined in [1]. Table of Content 1. Introduction ...................................................2 2. DHCPv4 Options for MoS Discovery................................3 2.1 Domain Name List .........................................4 2.2 IPv4 Address List ........................................5 3. DHCPv6 Options for MoS Discovery................................5 3.1 MoS Identifier Option.....................................6 3.2 IPv6 Relay Agent MoS Option...............................7 3.3 MoS Information Option 8 4. Option Usage 10 4.1 Usage of DHCPv4 Options for MoS Discovery 10 4.2 Usage of DHCPv6 Options for MoS Discovery 11 5. Security Considerations .......................................11 6. IANA Considerations ...........................................11 7. Acknowledgements ..............................................12 8. Normative References ..........................................12 9. Informative References ........................................12 10. Author's Addresses ...........................................12 1. Introduction IEEE 802.21 [1] 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 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 G. Bajko Expires 02/20/08 [Page 2] Mobility Services DHCP Options August 2007 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. It is anticipated that a Mobility Server will 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 three dhcp options for DHCPv4 and DHCPv6, one for each of the services defined in [1], namely IS, ES and CS. The options would allow an MN to locate a Mobility Server which hosts the desired MIH service type (IS, ES or CS) the MN is looking for. This is one of the possible solutions for locating a server providing Mobility Services; manual configuration is an example of another. 2. DHCPv4 Options for MoS Discovery This section describes three options for DHCPv4. The DHCPv4 options for MoS discovery carry either a 32-bit (binary) IPv4 address or, preferably, a DNS [RFC1035] fully-qualified domain name to be used by the MN to locate a server hosting either an IS, an ES or a CS service. 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_code| Length | enc | ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Mos Server (domain name or IP address list) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option code: IPv4 MoS option codes assigned by IANA (tbd), separate ones for IS (IPv4-IS), for ES (IPv4-ES) and CS (IPv4-CS). Length: indicates the total number of octets in the option following the 'Length' field, including the encoding byte G. Bajko Expires 02/20/08 [Page 3] Mobility Services DHCP Options August 2007 enc: one byte indicating the encoding type of the next field The options have two 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. The 'Length' field indicates the total number of octets in the option following the 'Length' field, including the encoding byte. 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 [7]. The code for the MIH IS option is XXX. The code for the MIH ES option is YYY. The code for the MIH CS option is ZZZ. 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 3.1 of [RFC1035], quoted below: Domain names in messages are expressed in terms of a sequence of labels. 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. [RFC1035] encoding was chosen to accommodate future internationalized 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 [8] 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. G. Bajko Expires 02/20/08 [Page 4] Mobility Services DHCP Options August 2007 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. Clients MUST support compression according to the encoding in Section 4.1.4 of "Domain Names - Implementation And Specification" [RFC1035]. Since the domain names are supposed to be different domains, compression will likely have little effect, however. If the length of the domain list exceeds the maximum permissible within a single option (254 octets), then the domain list MUST be represented in the DHCP message as specified in [7]. The DHCP option for this encoding has the following format: Code Len enc DNS name of MoS server +-----+-----+-----+-----+-----+-----+-----+-----+-- | XXX | 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: +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ |XXX|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 DHCP option for this encoding has the following format: Code Len enc IPv4 Address 1 IPv4 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | XXX | n | 1 | a1 | a2 | a3 | a4 | a1 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 3. DHCPv6 Options for MoS discovery 3.1 MoS Identifier Option G. Bajko Expires 02/20/08 [Page 5] Mobility Services DHCP Options August 2007 This option is included in the Information-request message and used to request an MoS-type information from a given network by the mobile node from the DHCP server. 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 IPv6-MoS | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |target network | MoS-type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + . . . Home Network Identifier . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_IPv6-MoS (TBD) option-len 2 + length of the Home Network Identifier field Target network The target network for the location of MoS Identifier: 1 local network 2 home network 3 both local and home networks MoS-Type The type of Mobility Services the MN is looking for, i.e. IS, ES or CS or a combination of these: 1 IS service 2 ES service 3 both IS and ES services 4 CS service 5 IS and CS services 6 ES and CS services 7 IS, ES and CS services Home Network Identifier The identifier to specify the requested home network of the mobile node. This field MUST be set in the form of FQDN [RFC1035]. The target network value 1 indicates the mobile node is interested in learning MoS information that pertains to the currently visited network. This type can be used to discover local MoS. In this case, G. Bajko Expires 02/20/08 [Page 6] Mobility Services DHCP Options August 2007 the option-len field is set to 2 and the Home Network Identifier field MUST NOT be included. The target network value of 2 indicates the mobile node is interested in learning the MoS information that pertains to the home network of the MN. This type can be used to discover MoS that are hosted by a user's home domain. The MN's home network is specified in the Home Network Identifier field. The target network value of 3 indicates the mobile node is interested in learning the MoS information that pertains to both local and home networks of the MN. 3.2 IPv6 Relay Agent MoS Option This option carries the home network information which was transferred to the NAS from AAAH by using [I-D.ietf-mip6-radius-MoS, TBD]. The DHCP relay agent sends this option to the DHCP server in the Relay-forward Message. 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_IPv6-MoS-RELAY | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . sub-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_IPv6-MoS-RELAY (TBD). option-len The length of sub-options sub-options A series of IPv6 Relay Agent sub-options. 3.2.1. IPv6 Relay Agent Sub-option This sub-option carries the MoS information to the DHCP server. 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-code | sub-opt-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MoS Type | | G. Bajko Expires 02/20/08 [Page 7] Mobility Services DHCP Options August 2007 . MoS Address . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ sub-opt-code A 16-bit unsigned integer for the type of the following MoS Address field. Possible values are: 1 MoS IP address list 2 MoS FQDN list sub-opt-len 1 + The length of MoS Address field. MoS type The type of MoS services the server supports. Valid values: 1 IS service 2 ES service 3 both IS and ES services 4 CS service 5 IS and CS services 6 ES and CS services 7 IS, ES and CS services MoS Address An MoS IP address or MoS FQDN to be provided to a mobile node according to the sub-opt-code. When the sub-opt-code is set to 1, the MoS Address field MUST contain the 128-bit IPv6 address of the MoS. When the sub-opt-code is set to 2, the MoS Address field MUST contain the FQDN of the MoS as described in Section 8 of [RFC3315]. Multiple sub-options may exist in a IPv6 Relay Agent option to carry more than one MoS address or FQDN. 3.3 MoS Information Option This option is included in the Reply message and used to carry MoS information to the mobile node in the form of one or more of MoS IP address(es) or MoS FQDN(s). 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 G. Bajko Expires 02/20/08 [Page 8] Mobility Services DHCP Options August 2007 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_IPv6-MoSINF | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . sub-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_IPv6-MoSINF (TBD). option-len length of sub-options sub-options A series of MoS Information sub-options. 3.3.1 MoS Information Sub-option This sub-option carries the assigned MoS information to the DHCP client. 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-code | sub-opt-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MoS Type | network | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + . MoS Information . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ sub-opt-code A 16-bit unsigned integer for the type of the following MoS Information field. Possible values are: 1 MoS address 2 MoS FQDN sub-opt-len 2 + length of MoS Information field. MoS type An 8 bit integer specifying the type of MoS services the G. Bajko Expires 02/20/08 [Page 9] Mobility Services DHCP Options August 2007 server supports. Valid values are: 0 NULL 1 IS service 2 ES service 3 both IS and ES services 4 CS services 5 IS and CS services 6 ES and CS services 7 IS, ES and CS services network An 8 bit integer specifying the network where the MoS whose address is attached, resides. Valid values: 1 home network 2 local network MoS Information An MoS IP address or MoS FQDN to be provided to a mobile node according to the sub-opt-code. The sub-opt-code, sub-opt-len and MoS Information fields are set in the same manner as those of an IPv6 Relay Agent sub-option. 4. Option Usage 4.1 Usage of DHCPv4 Options for MoS Discovery The requesting and sending of the proposed DHCPv4 options 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 a REQUEST message to a unicast server address. In this message the mobile node (DHCP client) MUST include the Option Code for the MoS Discovery option in the OPTION_code. 4.1.2 DHCP Server behavior G. Bajko Expires 02/20/08 [Page 10] Mobility Services DHCP Options August 2007 When the DHCP server receives the REQUEST message with the MoS Discovery option in the OPTION_code, the DHCP server MUST follow the [RFC2131] logic to construct a REPLY message with the MoS Discovery option. The reply message may contain IP address or the FQDN of the MoS Server. In case that the server cannot find any MoS information, it MUST return the MoS Discovery option by setting the MoS Server address 0.0.0.0 with 'enc' 1. 4.2 DHCPv6 Options for MoS discovery TBD. 4.2.1 Mobile node behavior 4.2.2 DHCP Relay Agent behavior 4.2.3 DHCP Server behavior 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 registers the following dhcpv4 options with IANA: IPv4-IS IPv4-ES IPv4-CS This document also registers the following dhcpv6 options with IANA: IPv6-MoSINF IPv6-MoS This document also registers the following dhcpv6 Relay options with IANA: IPv6-MoS-RELAY G. Bajko Expires 02/20/08 [Page 11] Mobility Services DHCP Options August 2007 7. Acknowledgements Acknowledgements to the DT members. 8. Normative References [1] IEEE 802.21 Standard for Local and Metropolitan Area Networks: Media Independent Handover Services [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. [7] 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 9. Informative References [8] Bajko, G. " Locating Mobility Servers", draft-bajko-mos-dns- discovery-00.txt 10. Author's Addresses Gabor Bajko Nokia gabor.bajko@nokia.com Subir Das Telcordia subir@research.telcordia.com G. Bajko Expires 02/20/08 [Page 12] Mobility Services DHCP Options August 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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. 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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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). G. Bajko Expires 02/20/08 [Page 13]