Internet Draft Daichi Funato draft-funato-seamoby-gaard-00.txt Xiaoning He Expires: May 14, 2002 Carl Williams Atsushi Takeshita DoCoMo USA Labs Geographically Adjacent Access Router Discovery Protocol Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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.'' To view the list Internet-Draft Shadow Directories, see http://www.ietf.org/shadow.html. Distribution of this memo is unlimited. The internet-draft will expire in 6 months. The date of expiration will be May 14, 2002. Abstract This document describes a scheme (GAARD) that discovers geographically adjacent access routers (GAARs). This is accomplished through a distributed process whereby all mobile hosts associated with the current access router identify geographically adjacent access routers by their corresponding Link-Layer beacons sent by geographically adjacent access points. The Link-Layer identifiers are pushed to a cache located on current access router. The GAARD scheme then specifies a mechanism whereby the current access router resolves the Link-Layer to IP Layer mapping for the geographically adjacent access routers. In this respect the mobile hosts function as sensors for identifying GAARs in order to provide information critical to the current access router and mobile host's capability to perform seamless IP-level handovers, such as fast handover and context transfer. The GAARD cache has the effect of providing information about the current access router surroundings not only to all the mobile hosts attached to the current access router, but also to those mobile hosts that may become attached in the future. Funato Expires May 14, 2002 [Page 1] Internet-Draft GAARD November 2001 Table of Contents 1. Introduction.................................................... 3 2. Terminology..................................................... 4 3. Protocol Overview............................................... 4 4. Proxy Router Solicitation and Advertisement Process............. 5 4.1 Mobile Host and Current Access Router Process............... 5 4.1.1 Mobile Host............................................. 6 4.1.2 Current Access Router................................... 6 4.2 Proxy Router Solicitation................................... 6 4.3 Proxy Router Advertisement.................................. 8 4.4 Discussion............................... ................. 11 4.5 Optional Fields Format..................................... 11 4.5.1 Link-Layer Address Field............................... 11 4.5.2 Prefix Information..................................... 13 4.5.3 Cache Update Field..................................... 14 4.6 GAARD Address Resolution for IPv4.......................... 15 4.7 GAARD Address Router Cache................................. 16 4.7.1 Optional Field Format.................................. 16 5. GAARD SLP Process.............................................. 17 6. Security ...................................................... 18 7. References..................................................... 18 8. AuthorsĘ Addresses............................................. 19 9. Acknowledgements............................................... 20 10. IPR Statement.................................................. 20 Funato Expires May 14, 2002 [Page 2] Internet-Draft GAARD November 2001 1. Introduction In a mobile network, handover occurs when a mobile host moves from the current Access Point (AP) to the geographically adjacent access point. For each geographically adjacent access point, the corresponding access router (AR) is defined as a Geographically Adjacent Access Router (GAAR) even if the access router is located in a logically distant subnet. For real-time mobile applications, a smooth and fast handover is critical. Furthermore, for most fast hand-over schemes, it is important for both the Mobile Host (MH) and the current access router to be aware of the identity of its GAAR. One existing approach is to manually configure this geographical neighborhood at each AR. However, such an approach requires precise wireless coverage planning and it may not be feasible in some cases, such as WLAN hot spot support. Another approach is based on special location information system such as GPS (Global Positioning System). GPS based system can provide information to AP and MH with candidates of geographically adjacent APs. However, the GPS is not always available. Due to these facts, it is clear that an automatic and dynamic mechanism is required to discover GAARs without much administrative intervention. GAARD protocol provides that kind of discovery mechanism. In the rest of this document, the GAARD protocol is presented. The GAARD protocol is a pre-movement or an "anticipated" protocol in the sense that a mobile host can get useful information about the potential next access router, e.g. IP address and prefix, from a Link-Layer id. The GAARD allows the mobile host or the current AR to decide with which access router it will register. As a result, the GAARD is able to provide a seamless handoff to the mobile host. In the GAARD, the mobile host acts as a sensor in surrounding wireless environments. If a mobile host can simultaneously listen to multiple APs' Link-Layer id, the GAARD protocol is able to work in a heterogeneous environment. As a result, the access router is able to quickly have a complete knowledge about its adjacent access routers. Funato Expires May 14, 2002 [Page 3] Internet-Draft GAARD November 2001 The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined in [KEYWORDS]. 2. Terminology -Access Point (AP) A radio transceiver by which an MN obtains Link-Layer connectivity with the wired network. -Access Router (AR) An IP router residing in an access network and connected to one or more APs. An AR offers IP connectivity to MN. -Geographically Adjacent AR (GAAR) An AR whose coverage area is such that an MN may move from the coverage area of the AR currently serving the MN into the coverage area of this AR. In other words, GAARs have APs whose coverage areas are geographically adjacent or overlap. 3. Protocol Overview ~~~~~~~~~~~ { } { } +--------->{ IP Cloud }-----------+ GAARD SLP |+----------{ }<----------+| Service || GAARD { } || Request || SLP ~~~~~~~~~~~ || |V Service Reply |V +---------+ +---------+ | Current | | Next | | AR | | AR | +---------+ +---------+ ^| | | Proxy || Proxy | | Router || Router | | Solicitation |V Advertisement +---+ +---+ +--------------+ L2 id +--|AP1| |AP2| | Mobile |<---------------------+ +---+ +---+ | Host |<--------------------------------| +--------------+ L2 id Figure.1 GAARD Protocol Funato Expires May 14, 2002 [Page 4] Internet-Draft GAARD November 2001 In short, the GAARD protocol intends to allow a mobile host to resolve the IP address and prefix of the GAAR across different subnets based on a Link-Layer id within the beacon broadcasted by the access point connected to GAAR. Since the protocol such as RARP or Inverse Neighbor Discovery can only resolve the IP address within a subnet, it is necessary to develop a protocol such as the GAARD protocol presented in this draft to resolve the IP address based on Link-Layer id across multiple subnets. In GAARD protocol, each access point MUST be able to broadcast a Link-Layer beacon which MUST contain a unique Link-Layer id. The mobile host MUST be able to listen to these Link-Layer beacons simultaneously. When the Mobile Host receives the Link-Layer id carried in the beacons, it sends the Proxy Router Solicitation message carrying this Link-Layer id to its current access router. In this darft , the access point is considered as an extended interface of the access router. At each access router, a GAARD cache defined in section 4.5 should be maintained. Each cache entry contains the Link-Layer id and the IP addresses associated with this id. After the current access router received the Proxy Router Solicitation message which contains a Link-Layer id, if the IP address associated with this Link-Layer id is found in the GAARD cache located at the current access router, the current access router must format a Proxy Router Advertisement message and sent back to the Mobile Host. Otherwise, the GAARD protocol will attempt to resolve the IP address first. As defined in section 5, the Service Location Protocol(SLP) [SLP] is used to resolve the IP address based on the Link-Layer id across multiple subnets. 4. Proxy Router Solicitation and Advertisement Process 4.1 Mobile Host and Current Access Router Process For the different IP versions, the messages between Mobile Host and current Access Router are extension of different protocols. For IPv6, the messages are defined as the extensions of Fast Mobile IPv6 [FMIPv6] Proxy Router Solicitation/Advertisement [FMIPv6,IPv6] in section 4.2 and 4.3. Funato Expires May 14, 2002 [Page 5] Internet-Draft GAARD November 2001 4.1.1 Mobile Host When a mobile host receives a new Link-Layer id, it first searches the local GAARD cache maintained at itself. If the IP address associated with this Link-Layer id can not be found, the mobile host MUST format a Proxy Server Solicitation message as defined in section 4.2 and sends it to the current access router. When the current access router sends back the GAARD Proxy Router Advertisement message which contains the IP addresses associated with the Link-layer id, the mobile node may add or update this information in its cache to facilitate the later use. If a GAARD cache is maintained at the mobile host, the mobile host MUST be able to process the Cache Update messages as defined in section 4.5.1. 4.1.2 Current Access Router After receives a Proxy Router Solicitation message, the current access router first checks the Sub-Type field of Link-layer Addresses (LLA) field. If this field is set to NULL, the access router MUST send back the whole cache to the mobile host in a GAARD Proxy Router Advertisement message. If the LLA field is set to be NULL and Sub-Type field is not NULL, the access router MUST send all the cache entries which have the same Link-Layer Type as indicated in Sub-Type field back to Mobile Host. If the LLA filed is not NULL and the IP address associated with the LLA is found in the cache, the access router MUST format a GAARD Proxy Router Advertisement message and send it back to the Mobile Host. If the IP address associated with the LLA can not be found in the cache, the GAARD SLP process defined in section 5 MUST be performed. 4.2 Proxy Router Solicitation A Mobile Host sends a Proxy Router Solicitation message which MUST carry the Link-Layer id obtained from Link-Layer's beacon to its current access router. Funato Expires May 14, 2002 [Page 6] Internet-Draft GAARD November 2001 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- IP Fields: Source Address An IP address of the Mobile Host Destination Address The address of the current Access Router Hop Limit 255 Authentication Header If a Security Association for the IP Authentication Header exists between the sender and the destination address, then the sender SHOULD include this header. ICMP Fields: Type TBD Code 0 Checksum The ICMP checksum. See [ICMPv6]. Identifier MUST be set by the sender so replies can be matched to this Solicitation. Reserved MUST be set to zero by the sender and ignored by the receiver. Required options: The sender node MUST send one or more following options in the GAARD Proxy Router Solicitation message: Funato Expires May 14, 2002 [Page 7] Internet-Draft GAARD November 2001 Target link-layer address field The link-layer address field of the access router whose IP address will be resolved, if known. The format of this field is defined in section Other valid options: Future versions of this protocol may add other option types. Receivers MUST silently ignore any options they do not recognize and continue processing the message. 4.3 Proxy Router Advertisement After received a Proxy Router Solicitation message, the current access router replies with the Proxy Router Advertisement. If the Sub-Type filed of Target link-layer address field in the Proxy Router Solicitation message is 0, the access router MUST send back all the cache entries back to the mobile Host. If the LLA in the Target link-layer address field is set to be 0 and Sub-Type field is not 0, the access router MUST send all the cache entries which have the same Link-Layer Type as indicated in Sub-Type Type filed of the Proxy Router Advertisement message back to Mobile Host. If both the LLA field and Sub-Type fields in the Proxy Router Solicitation message are not NULL and a cache entry is found which contains the IP addresses associated with the Link Layer id carried in the Proxy Router Solicitation message or the SLP Process as defined in Section 5 is successfully being performed, the access router MUST send back this cache entry to the Mobile Host. Funato Expires May 14, 2002 [Page 8] Internet-Draft GAARD November 2001 The Proxy Router Advertisement message is defined as an extension of the FMIPv6 Proxy Router Advertisement: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- IP Fields: Source Address The address of current access router Destination Address The address of mobile host Hop Limit 255 Authentication Header If a Security Association for the IP Authentication Header exists between the sender and the destination address, then the sender SHOULD include this header. ICMP Fields: Type TBD Code 0 Handover Information 1 No change of COA required 128 New Attachment Point not known Checksum The ICMP checksum. See [ICMPv6]. Identifier Copied from Router Solicitation for Proxy or set to Zero if unsolicited. Reserved MUST be set to zero by the sender and ignored by the receiver. Funato Expires May 14, 2002 [Page 9] Internet-Draft GAARD November 2001 Required options: The sender node MUST send following options in the GAARD Proxy Router Advertisement message: Link-layer address The link-layer id of the access router which the mobile host tries to resolve the IP address. Prefix Information These options specify the IP address and prefix associated with the link-layer id. Note that if the mobile host set the Sub-Type field or LLA field to NULL, the Proxy router solicitation will carry multiple Link-Layer address and Prefix Information field pair in a single Proxy Router Solicitation message. Other valid options: The format of this filed in defined in Section 4.4. The sender node MAY choose to add the following option in the Advertisement message: New COA Option In stateful configuration, this option MUST be sent to allocate an address on behalf of the Access Router this message is proxied for (i.e.: the new access router). In stateless address auto- configuration this option may or may not be sent. If sent, indicates that the requesting node SHOULD use this address as new care-of-address for the duration of the handover. If not sent the requesting node SHOULD compute the new care-of- address using the Interface ID from the Destination Address of this message. Cache Update Cache Update actions used to keep the GAARD at the Funato Expires May 14, 2002 [Page 10] Internet-Draft GAARD November 2001 Mobile Host synchronized with the GAARD cache at the access router. Future versions of this protocol may add other option types. Receivers MUST silently ignore any options they do not recognize and continue processing the message. 4.4 Discussion In section 4.2 and 4.3, the Proxy Router Solicitation/Advertisement messages are being used. However, different from usage of Proxy Router Solicitation/Advertisment message in the FMIPv6, in GAARD, the some optional fields are mandatory. Also, a new optinal field, i.e. Cache Update is defined. 4.5 Optional Fields Format 4.5.1 Link-layer Addresses Filed This extension is based on the [MIER] format. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Sub-Type | LLA ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fields: Type TBD Length The length of the option (including the type, sub-type and length fields) in units of 8 octets. Funato Expires May 14, 2002 [Page 11] Internet-Draft GAARD November 2001 Sub-Type 0 Get whole cache from the current access router 1 for the Link-layer Address of the new Attachment Point. 2 for the Link-layer Address of the Mobile Node. 3 for the Link-layer Address of the Proxied Originator TBD for the link-layer id identifying the access technology, e.g. 802.11 LLA The variable length link-layer id or address. The content and format of this field (including byte and bit ordering) is expected to be specified in specific documents that describe how IPv6 operates over different link layers. Description The New Attachment Point Link Layer address contains the link-layer address of the attachment point the mobile node attempts to handover to. This is used in the Router Solicitation for Proxy message. The Mobile Node Link-Layer address option contains the link- layer address of a mobile node. It is used in the Handover Initiation message. The Proxied Originator Link-Layer address option contains the Link Layer address of the Access Router the Proxy Router Solicitation message refers to. These options MUST be silently ignored for other Neighbor Discovery messages. NOTE: Source and Target Link Layer Addresses as defined in [ND] MAY also be used by Router Solicitation for Proxy and Proxy Routing Advertisement messages. Funato Expires May 14, 2002 [Page 12] Internet-Draft GAARD November 2001 4.5.2. Prefix Information 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Prefix Length |L|A| Reserved1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Valid Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Preferred Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fields: Type TBD Length 4 Prefix Length 8-bit unsigned integer. The number of leading bits in the Prefix that are valid. The value ranges from 0 to 128. L 1-bit on-link flag. When set, indicates that this prefix can be used for on-link determination. When not set the advertisement makes no statement about on-link or off-link properties of the prefix. For instance, the prefix might be used for address configuration with some of the addresses belonging to the prefix being on-link and others being off- link. A 1-bit autonomous address-configuration flag. When set indicates that this prefix can be used for autonomous address configuration as specified in [ADDRCONF]. Funato Expires May 14, 2002 [Page 13] Internet-Draft GAARD November 2001 Reserved1 6-bit unused field. It MUST be initialized to zero by the sender and MUST be ignored by the receiver. Valid Lifetime 32-bit unsigned integer. The length of time in seconds (relative to the time the packet is sent) that the prefix is valid for the purpose of on-link determination. A value of all one bits (0xffffffff) represents infinity. The Valid Lifetime is also used by [ADDRCONF]. Preferred Lifetime 32-bit unsigned integer. The length of time in seconds (relative to the time the packet is sent) that addresses generated from the prefix via stateless address autoconfiguration remain preferred [ADDRCONF]. A value of all one bits (0xffffffff) represents infinity. See [ADDRCONF]. Reserved2 This field is unused. It MUST be initialized to zero by the sender and MUST be ignored by the receiver. Prefix An IPaddress. The first Prefix Length many bits of this address contains the prefix information for this address. 4.5.3 Cache Update Field When a cache entry at the access router has been changed or deleted, the GAARD Cache Update message MUST be broadcasted. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AC| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- Funato Expires May 14, 2002 [Page 14] Internet-Draft GAARD November 2001 Fields: Type TBD Code 0 Length The Length of the cache update message AC Action of the Update 0 Update an entry 1 Remove an entry Reserved 32-bit unused field. It MUST be initialized to zero by the sender and MUST be ignored by the receiver. Required options: TBD Other valid options: TBD Future versions of this protocol may add other option types. When the AC filed is set to be 0, the Mobile Host MUST update the entry with the information carried in the GAARD Cache Update message. When the AC filed is set to be 1, the Mobile Host MUST remove the entry. 4.6 GAARD Address Resolution for IPv4 TBD Funato Expires May 14, 2002 [Page 15] Internet-Draft GAARD November 2001 4.7 GAARD Access Router Cache Each GAARD access router MUST maintain a cache table. Each entry in the cache table has the follow format: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | Length | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + LLA + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + IP Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + One or More Optional Fields + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The cache entry SHOULD be periodically updated and broadcasted. In order to keep the cache synchronized, when the cache entry in the access router. When a cache entry in the access router has been changed or deleted, the access router MUST format a GAARD Cache Update message and broadcast this message. 4.7.1 Optional Field Format The optional fields allow the access router to put extra information to assist the mobile host in the handover. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type Type of the value Funato Expires May 14, 2002 [Page 16] Internet-Draft GAARD November 2001 Length The length of the option (including the Type, Length, and the Reserved fields) in units of 8 octets. Reserved This field is unused. It MUST be initialized to zero by the sender and MUST be ignored by the receiver. 5. GAARD SLP Process In order to resolve the GAAR's IP address across multiple subnets, the Service Location Protocol (SLP) can be used in the GAARD protocol. Inter-Administrative Domain Discovery is not covered in this draft and may be covered in the following drafts. At each access router, a list which contains the Link-Layer id of the access points connected to it MUST be maintained. If a SLP DA is deployed, the access router MUST format and send a service registration message (ServReg) which contains both IP address of the access router and the Link-Layer id list to the Directory Agent (DA) in its scope periodically. If there is no deployed DA, the access router MUST function as a SLP Service Agent (SA) and service any queries for the reverse address resolution. After the access router receives the Proxy Router Solicitation message from the mobile host and if the IP address associated with the Link-Layer id is not found in the cache, the access router MUST format a Service Request (ServReq) message which queries the IP addresses associated with the Link-Layer id. For example, when the current access router has to resolve the IP address associated with the Link-Layer id = XXXX, it MUST function as a SLP User Agent (UA) and format and send the following ServReq message After receiving the Service Request message mentioned above, either the DA or the access router which is a SLP SA in conformance with the SLP specification MUST reply with a Service Reply message. For example, the access router who is connected to the access point with Link-Layer-id is XXXX must send back the Service Reply message shown as follows Funato Expires May 14, 2002 [Page 17] Internet-Draft GAARD November 2001 Another example is that the access router may send back the Service Reply message shown as follows In this case, the access router not only sends back the IP address of the access router, but also send back the network prefix of the access router's network. This example shows that the GAARD is flexible and be able to provide useful information to assist the mobile node. This is only a brief overview of how SLP is used in GAARD protocol to achieve cross subnet address resolution. A similar process is used in IAPP [IAPP]. The new SLP templates and attributes defined for the GAARP will be described in other drafts. 6. Security There are several security related issues associated with the GAARD which will be addressed in the revisions of this draft. 7. References [IPv6] Deering, S. and R. Hinden, "Internet Protocol Version 6 Specification", RFC 2460, December 1998. [MIER] Khalil, M., Narayanan, R., Akhtar, H., Qaddoura, E., "Mobile IP Extensions Rationalization (MIER)", Work in progress, December 1999. [ICMPv6] Conta, A., and S. Deering "Internet Control Message Protocol for the Internet Protocol Version 6", RFC 2463, December 1998. [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [SLP] Guttman, E., Perkins, C., Veizades, J, Day, M., "Service Location Protocol, Version 2", RFC 2608, June 1999. [IAPP] IEEE Std 802.11f/D2.0, "Draft Recommended Practice for Multi-Vendor Access Point Interoperability via an Inter-Access Point Protocol Across Distribution Systems Supporting IEEE 802.11 Operation ", July 2001 Funato Expires May 14, 2002 [Page 18] Internet-Draft GAARD November 2001 [L2REQ] Kempf, J., Funato, D., Malki, K., Gwon, Y., Pettersson, M. Reoberts, P., Soliman, H., Takeshita, A., Yegin, A., " Requirements for Layer 2 Protocols to Support Optimized Handover for IP Mobility ", Working in Progress [FMIPv6] Dommety, G., Yegin, A., Perkins, C., Tsirtsis, G., El-Malki, K., Khalil, M., " Fast Handovers for Mobile IPv6 ", Work in Progress, July 2001. 8. Authors' Addresses Daichi Funato DoCoMo Communications Laboratories USA, Inc. 181 Metro Drive, Suite 300 San Jose, CA 95110 USA Phone: +1 408-451-4736 EMail: funato@docomolabs-usa.com Xiaoning He DoCoMo Communications Laboratories USA, Inc. 181 Metro Drive, Suite 300 San Jose, CA 95110 USA Phone: +1 408-451-4737 EMail: xiaoning@docomolabs-usa.com Carl Williams DoCoMo Communications Laboratories USA, Inc. 181 Metro Drive, Suite 300 San Jose, CA 95110 USA Phone: +1 408-451-4741 EMail: carlw@docomolabs-usa.com Atsushi Takeshita DoCoMo Communications Laboratories USA, Inc. 181 Metro Drive, Suite 300 San Jose, CA 95110 USA Phone: +1 408-451-4705 EMail: takeshita@docomolabs-usa.com Funato Expires May 14, 2002 [Page 19] Internet-Draft GAARD November 2001 9. Acknowledgements Thanks to James Kempf and Alper Yegin, DoCoMo USA Labs, for reviewing the SLP protocol and FMIPv6. We also thank Fujio Watanabe, DoCoMo USA Labs, for his consultation on IEEE 802.11 protocols. 10. IPR Statement Copyright (C) The Internet Society (2001). All Rights Reserved. DoCoMo Communications Laboratories USA, Inc. (DoCoMo USA Labs) hereby declare that we are in conformity with Section 10 of RFC 2026. Contributions of DoCoMo USA Labs may contain one or more patents or patent applications. To the extent that the contribution of DoCoMo USA Labs is adopted to the specification, DoCoMo USA Labs undertakes to license patents technically necessary to implement the specification on fair, reasonable and nondiscriminatory terms based on recipprocity. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. Funato Expires May 14, 2002 [Page 20]