MIPSHOP WG Gabor Bajko Internet Draft Nokia Intended Status: Proposed Standard Subir Das Expires: December 22, 2008 Telcordia June 22, 2008 Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for Mobility Server (MoS) discovery draft-ietf-mipshop-mos-dhcp-options-03 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 (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 [IEEE802.21]. Conventions used in this document G. Bajko & S Das Expires 12/22/08 [Page 1] Mobility Services DHCP Options December 2008 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. DHCPv4 Relay Agent MoS Option.................................6 3.2.1. IPv4 MoS Relay Agent Sub-option......................7 4. DHCPv6 Options for MoS Discovery..............................6 4.1 IPv6 MoS Identifier Option..............................6 4.2 IPv6 Relay Agent MoS Option.............................9 4.3 IPv6 MoS Information Option............................11 5. Option Usage.................................................13 5.1 Usage of DHCPv4 Options for MoS Discovery..............13 5.2 Usage of DHCPv6 Options for MoS Discovery..............14 6. Security Considerations .....................................15 7. IANA Considerations .........................................15 8. Acknowledgements ............................................16 9. Normative References ........................................16 10. Informative References .....................................17 11. Author's Addresses .........................................17 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 the heterogeneous networks and perform seamless handover across these networks. G. Bajko & S. Das Expires 12/22/08 [Page 2] Mobility Services DHCP Options December 2008 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. 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 three DHCPv6 options which 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 | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Option n | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G. Bajko & S. Das Expires 12/22/08 [Page 3] Mobility Services DHCP Options December 2008 Option Code OPTION-IPv4-MoS (TBD) - 2 bytes Length 2 bytes Sub-options A series of DHCPv4 sub-options. When the total length of a MoS option exceeds 255 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(N) and sub-option value. The value of the length octet does not include itself or the option code. Sub-option value has 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. 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 IP Address | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The sub-option Types are summarized below. +--------------+---------------+ | Sub-opt | Service | | Type* | Name | +==============+===============+ | 1 | IS | +--------------+---------------+ | 2 | ES | +--------------+---------------+ G. Bajko & S. Das Expires 12/22/08 [Page 4] Mobility Services DHCP Options December 2008 +--------------+---------------+ | 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 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 limits 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 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 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: G. Bajko & S. Das Expires 12/22/08 [Page 5] Mobility Services DHCP Options December 2008 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. IPv4 Relay Agent MoS Option This option carries the home network MoS information which was transferred to the NAS from AAAH by using [MoS-AAA]. The DHCP relay agent insert this option when forwarding client-originated DHCP packets to a 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 Code | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-options | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code OPTION-IPv4-MoS-RELAY (TBD) - 2 bytes G. Bajko & S. Das Expires 12/22/08 [Page 6] Mobility Services DHCP Options December 2008 Length The length of sub-options Sub-options A series of IPv4 Relay Agent sub-options. When the total length of a Relay Agent MoS option exceeds 255 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(N) and sub-option value. The value of the length octet does not include itself or the option code. Sub-option value has two encodings, specified by the encoding byte ('enc')as described in Section 2.1 and Section 2.2. 3.2.1. IPv4 MoS Relay Agent Sub-option 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 | +--------------+---------------+ G. Bajko & S. Das Expires 12/22/08 [Page 7] Mobility Services DHCP Options December 2008 *Note: The values ?0?, '8' to '255' are reserved and MUST NOT be used. 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] as described in Section 2.1. 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 as described in Section 2.2. 4. DHCPv6 Options for MoS discovery This section introduces new DHCPv6 options used for MoS discovery. Whether the MN receives an MoS address from local or home network will depend on the actual network deployment. In general, following rules apply to discovery rules: a) In a split scenario, where the network access authentication is independent of the home network authentication, the MN will discover the MoS in the local (visited) network. b) In an integrated scenario, where the network access authentication is performed by the home network, the MN will discover the MoS as per the home network policy, usually stored in the subscription profile. When the policy dictates that an MoS located in the home network has to be used, the address of the MoS from the home network may be sent to a NAS (via AAA protocols) to the visited network during the authentication procedure. A DHCP relay agent may be provisioned accordingly to forward the MOS address to the DHCP Server. The DHCPv6 options defined in this section together with the procedures defined in section 4 can support both scenarios. 4.1 IPv6 MoS Identifier Option This option is included in the Information-request message and used to request the address of a specific (e.g., IS, ES, CS or any combination) MoS-type from a 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 Code | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MoS-type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option Code OPTION-IPv6-MoS (TBD) - 2 bytes G. Bajko & S. Das Expires 12/22/08 [Page 8] Mobility Services DHCP Options December 2008 Length 2 bytes MoS-Type* 1 byte The type of Mobility Services the MN is looking for, i.e., IS, ES or CS or a combination of these: +--------------+-------------- + | MoS-type | MoS Name | | value | | +==============+===============+ | 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. 4.2 IPv6 Relay Agent MoS Option This option carries the home network information which was transferred to the NAS from AAAH by using [MoS-AAA]. 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 Code | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-options | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G. Bajko & S. Das Expires 12/22/08 [Page 9] Mobility Services DHCP Options December 2008 Option-code OPTION-IPv6-MoS-RELAY (TBD) - 2 bytes Length The length of sub-options Sub-options A series of IPv6 Relay Agent sub-options. 4.2.1. IPv6 MoS 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 | Length | MoS Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . MoS Information . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Sub-opt-code An 8-bit unsigned integer for the type of the following MoS Information field. Possible values are: 1 MoS IP address list 2 MoS FQDN list Length 1 + the length of MoS Information field. MoS-Type* 1 byte The type of Mobility Services the MN is looking for, i.e., IS, ES or CS or a combination of these: +--------------+-------------- + | MoS Type | MoS Name | | value | | +==============+===============+ | 1 | IS | +--------------+---------------+ | 2 | ES | +--------------+---------------+ | 3 | IS and ES | +--------------+---------------+ G. Bajko & S. Das Expires 12/22/08 [Page 10] Mobility Services DHCP Options December 2008 +--------------+---------------+ | 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. MoS Information An MoS IP address or MoS FQDN. When the sub-opt-code is set to 1, the MoS Information field MUST contain the 128-bit IPv6 address of the MoS. When the sub-opt-code is set to 2, the MoS Information 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 Information (IPv6 address or FQDN). 4.3 IPv6 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Code | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . Sub-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option Code OPTION-IPv6-MoSINF (TBD)- 2 bytes Length The length of sub-options sub-options A series of MoS Information sub-options. G. Bajko & S. Das Expires 12/22/08 [Page 11] Mobility Services DHCP Options December 2008 4.3.1 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 | Length | MoS Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . MoS Information . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Sub-opt Code An 8-bit unsigned integer for the type of the following MoS Information field. Possible values are: 1 MoS IP address 2 MoS FQDN Length 1 + length of MoS Information field. MoS-Type* 1 byte The type of Mobility Services the MN is looking for, i.e., IS, ES or CS or a combination of these: +--------------+-------------- + | MoS Type | MoS Name | | value | | +==============+===============+ | 1 | IS | +--------------+---------------+ | 2 | ES | +--------------+---------------+ | 3 | IS and ES | +--------------+---------------+ | 4 | CS | +--------------+---------------+ | 5 | IS and CS | +--------------+---------------+ | 6 | ES and CS | +--------------+---------------+ | 7 | IS, CS and ES | +--------------+---------------+ G. Bajko & S. Das Expires 12/22/08 [Page 12] Mobility Services DHCP Options December 2008 *Note: The values '0', '8' to '255' are reserved and MUST NOT be used. MoS Information An MoS IP address or MoS FQDN to be provided to a mobile node as indicated in 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 MoS Relay Agent sub-option. 5. Option Usage 5.1 Usage of DHCPv4 Options for MoS Discovery The requesting and sending of the proposed DHCPv4 options follow the rules for DHCP options in [RFC2131]. 5.1.1 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. 5.1.2 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 and not based upon the Sub-opt Type that is inserted by the relay agent. G. Bajko & S. Das Expires 12/22/08 [Page 13] Mobility Services DHCP Options December 2008 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. 5.1.3 DHCP Relay Agent behavior Upon receiving the DHCP-REQUEST from the mobile node, the DHCP relay agent MUST forward the message to the DHCP server as per [RFC2131]. If the relay agent determines that the AAAV/NAS has passed MoS information for this mobile node and has available MoS information for it, the relay agent MUST include the MoS information in the IPv4 Relay Agent MoS option, and insert this option in client-originated DHCP packets to a DHCP server. In case the relay agent does not maintain any MoS information for the requesting mobile node, it simply forwards the received message to the DHCP server according to the [RFC2131]. Servers recognizing the IPv4 Agent MoS option may use the information to implement MoS IP address or other parameter assignment policies. The DHCP Server echoes the option back verbatim to the relay agent in server-to-client replies, and the relay agent strips the option before forwarding the reply to the client according to the [RFC2131]. 5.2 DHCPv6 Options for MoS discovery The requesting and sending of the proposed DHCPv6 options follow the rules for DHCP options in [RFC3315]. 5.2.1 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 an Information-request message to the All_DHCP_Relay_Agents_and_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. 5.2.2 DHCP Relay Agent behavior Upon receiving the Information-request from the mobile node, the DHCP relay agent MUST forward the message to the DHCP server as per [RFC3315]. G. Bajko & S. Das Expires 12/22/08 [Page 14] Mobility Services DHCP Options December 2008 If the relay agent determines that the AAAV/NAS has passed MoS information for this mobile node and has available MoS information for it, the relay agent MUST include the MoS information in the IPv6 Relay Agent option, and attach this option in the Relay-forward message. In case the relay agent does not maintain any MoS information for the requesting mobile node, it simply forwards the received message to the DHCP server according to the [RFC3315]. Upon receiving a Relay-reply message from the DHCPv6 server, the relay agent MUST follow the guidelines defined in [RFC3315]. The relay agent extracts the Reply message from the Relay Message option in the Relay-reply message and relays it to the mobile node. 5.2.3 DHCP Server behavior When the DHCP Server receives the Information-request message with the MoS Identifier option in the Relay-forward message, it looks for a MIP6 Relay Agent Option containing MoS Information. The Information-request message may not include the MIP6 Relay Agent option in case there was no MoS information available at the NAS / DHCP Relay Agent for a mobile node. The DHCP server MUST follow the following logic to construct a Reply message with the MoS Information option, and include the Reply message in the payload of a Relay Message option of Relay-reply message. 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 either extracted from the IPv6 MOS Relay Agent option or from the preconfigured information available locally. The DHCP server MUST always construct the response according to the MoS Type requested by the DHCP client and not based upon the MoS Type that is inserted by the relay agent. In case that the server cannot find any MoS information for a specific MoS type, it MUST return the MoS Information option with a sub-option by setting the MoS type to the requested MoS Type and the length of the sub-option is to 4. 6. 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, G. Bajko & S. Das Expires 12/22/08 [Page 15] Mobility Services DHCP Options December 2008 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. 7. IANA Considerations This document defines one new DHCPv4 option as described in section 2. MoS Option for DHCPv4 (OPTION-IPv4-MoS) TBD Mos Option for DHCPv4 Relay (OPTION-IPV4-MoS-RELAY) TBD This document creates a new registry for the Sub-Option field in the MoS DHCPv4 option called the "MoS Service Type". 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 three new DHCPv6 options as described in sections 3.1 and 3.2 IPv6-MoSINF (IPv6 MoS Information Option) TBD IPv6-MoS (IPv6 MoS Identifier Option) TBD IPv6-MoS-RELAY (IPv6 Relay Agent MoS Option) TBD This document creates a new registry for the "MoS Type" field in the IPv6 MoS Relay Agent Sub-option (section 3.2.1) and the MoS Information Sub-option (section 3.3.1). 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. G. Bajko & S. Das Expires 12/22/08 [Page 16] Mobility Services DHCP Options December 2008 8. Acknowledgements Authors would like to acknowledge the following individuals for their valuable comments. Vijay Devarapalli, Telemaco Melia, and Yoshihiro Ohba 9. 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 10. Informative References [IEEE802.21] IEEE 802.21 Standard for Local and Metropolitan Area Networks: Media Independent Handover Services [MoS-DNS] Bajko, G., "Locating Mobility Servers", draft-ietf-mipshop-mos-dns-discovery-01, (Work in Progress), May 2008. [MoS-AAA] Stuper, Patrick et.al, ?Diameter extensions for MoS Discovery? draft-stupar-dime-mos-options-00? (Work in progress), February, 2008 11. 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 12/22/08 [Page 17] Mobility Services DHCP Options December 2008 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. 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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). G. Bajko & S. Das Expires 12/22/08 [Page 18]