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Network Working Group                                      J. Kempf, Ed.Request for Comments: 4831                               DoCoMo USA LabsCategory: Informational                                       April 2007Goals for Network-Based Localized Mobility Management (NETLMM)Status of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The IETF Trust (2007).Abstract   In this document, design goals for a network-based localized mobility   management (NETLMM) protocol are discussed.Table of Contents1. Introduction ....................................................21.1. Terminology ................................................22. NETLMM Functional Architecture ..................................33. Goals for the NETLMM Protocol ...................................33.1. Goal 1: Handover Performance Improvement ...................43.2. Goal 2: Reduction in Handover-Related Signaling Volume .....53.3. Goal 3: Location Privacy ...................................63.4. Goal 4: Limit Overhead in the Network ......................7      3.5. Goal 5: Simplify Mobile Node Mobility Management           Security by Deriving from IP Network Access and/or IP           Movement Detection Security ................................73.6. Goal 6: Link Technology Agnostic ...........................83.7. Goal 7: Support for Unmodified Mobile Nodes ................83.8. Goal 8: Support for IPv4 and IPv6 ..........................93.9. Goal 9: Reuse of Existing Protocols Where Sensible ........10      3.10. Goal 10: Localized Mobility Management            Independent of Global Mobility Management ................10      3.11. Goal 11: Configurable Data Plane Forwarding            between Local Mobility Anchor and Mobile Access Gateway ..114. Security Considerations ........................................115. Acknowledgements ...............................................116. Normative References ...........................................127. Informative References .........................................128. Contributors ...................................................13Kempf                        Informational                      [Page 1]

RFC 4831                      NETLMM Goals                    April 20071.  Introduction   In [1], the basic problems that occur when a global mobility protocol   is used for managing local mobility are described, and two currently   used approaches to localized mobility management -- the host-based   approach that is used by most IETF protocols, and the proprietary   Wireless LAN (WLAN) switch approach used between WLAN switches in   different subnets -- are examined.  The conclusion from the problem   statement document is that none of the approaches has a complete   solution to the problem.  While the WLAN switch approach is most   convenient for network operators and users because it requires no   software on the mobile node other than the standard drivers for WiFi,   the proprietary nature limits interoperability, and the restriction   to a single last-hop link type and wired backhaul link type restricts   scalability.  The IETF host-based protocols require host software   stack changes that may not be compatible with all global mobility   protocols.  They also require specialized and complex security   transactions with the network that may limit deployability.  The   conclusion is that a localized mobility management protocol that is   network based and requires no software on the host for localized   mobility management is desirable.   This document develops a brief functional architecture and detailed   goals for a network-based localized mobility management protocol   (NETLMM).Section 2 describes the functional architecture of NETLMM.   InSection 3, a list of goals that is desirable in the NETLMM   protocol is presented.Section 4 briefly outlines Security   Considerations.  More discussion of security can be found in the   threat analysis document [2].1.1.  Terminology   Mobility terminology in this document follows that inRFC 3753 [10]   and in [1].  In addition, the following terms are related to the   functional architecture described inSection 2:   Localized Mobility Management Domain      An Access Network in the sense defined in [1] in which mobility is      handled by the NETLMM protocol.   Mobile Access Gateway      A Mobile Access Gateway (MAG) is a functional network element that      terminates a specific edge link and tracks mobile node IP-level      mobility between edge links, through NETLMM signaling with the      Localized Mobility Anchor.  The MAG also terminates host routed      data traffic from the Localized Mobility Anchor for mobile nodesKempf                        Informational                      [Page 2]

RFC 4831                      NETLMM Goals                    April 2007      currently located within the edge link under the MAG's control,      and forwards data traffic from mobile nodes on the edge link under      its control to the Localized Mobility Anchor.   Local Mobility Anchor      A Local Mobility Anchor (LMA) is a router that maintains a      collection of host routes and associated forwarding information      for mobile nodes within a localized mobility management domain      under its control.  Together with the MAGs associated with it, the      LMA uses the NETLMM protocol to manage IP node mobility within the      localized mobility management domain.  Routing of mobile node data      traffic is anchored at the LMA as the mobile node moves around      within the localized mobility management domain.2.  NETLMM Functional Architecture   The NETLMM architecture consists of the following components.   Localized Mobility Anchors (LMAs) within the backbone network   maintain a collection of routes for individual mobile nodes within   the localized mobility management domain.  The routes point to the   Mobile Access Gateways (MAGs) managing the links on which the mobile   nodes currently are located.  Packets for a mobile node are routed to   and from the mobile node through tunnels between the LMA and MAG.   When a mobile node moves from one link to another, the MAG sends a   route update to the LMA.  While some mobile node involvement is   necessary and expected for generic mobility functions such as   movement detection and to inform the MAG about mobile node movement,   no specific mobile-node-to-network protocol will be required for   localized mobility management itself.  Host stack involvement in   mobility management is thereby limited to generic mobility functions   at the IP layer, and no specialized localized mobility management   software is required.3.  Goals for the NETLMM Protocol   Section 2 of [1] describes three problems with using a global   mobility management protocol for localized mobility management.  Any   localized mobility management protocol must naturally address these   three problems.  In addition, the side effects of introducing such a   solution into the network need to be limited.  In this section, we   address goals for NETLMM, including both solving the basic problems   (Goals 1, 2, and 3) and limiting the side effects (Goals 4+).Kempf                        Informational                      [Page 3]

RFC 4831                      NETLMM Goals                    April 2007   Some basic goals of all IETF protocols are not discussed in detail   here, but any solution is expected to satisfy them.  These goals are   fault tolerance, robustness, interoperability, scalability, and   minimal specialized network equipment.  A good discussion of their   applicability to IETF protocols can be found in [4].   Out of scope for the initial goals discussion are Quality of Service   (QoS) and dormant mode/paging.  While these are important functions   for mobile nodes, they are not part of the base localized mobility   management problem.  In addition, mobility between localized mobility   management domains is not covered here.  It is assumed that this is   covered by the global mobility management protocols.3.1.  Goal 1: Handover Performance Improvement   Handover packet loss occurs because there is usually latency between   when the link handover starts and when the IP subnet configuration   and global mobility management signaling completes.  During this   time, the mobile node is unreachable at its former topological   location on the old link where correspondents are sending packets.   Such misrouted packets are dropped.  This aspect of handover   performance optimization has been the subject of much work, both in   other Standards Development Organizations (SDOs) and in the IETF, in   order to reduce the latency in IP handover.  Many solutions to this   problem have been proposed at the link layer and at the IP layer.   One aspect of this goal for localized mobility management is that the   processing delay for changing the forwarding after handover must   approach as closely as possible the sum of the delay associated with   link-layer handover and the delay required for active IP-layer   movement detection, in order to avoid excessive packet loss.   Ideally, if network-side link-layer support is available for handling   movement detection prior to link handover or as part of the link   handover process, the routing update should complete within the time   required for link handover.  This delay is difficult to quantify, but   for voice traffic, the entire handover delay, including Layer 2   handover time and IP handover time should be between 40-70 ms to   avoid any degradation in call quality.  Of course, if the link-layer   handover latency is too high, sufficient IP-layer handover   performance for good real-time service cannot be matched.   A goal of the NETLMM protocol -- in networks where the link-layer   handover latency allows it -- is to reduce the amount of latency in   IP handover, so that the combined IP-layer and link-layer handover   latency is less than 70 ms.Kempf                        Informational                      [Page 4]

RFC 4831                      NETLMM Goals                    April 20073.2.  Goal 2: Reduction in Handover-Related Signaling Volume   Considering Mobile IPv6 [9] as the global mobility protocol (other   mobility protocols require about the same or somewhat less), if a   mobile node using address autoconfiguration is required to   reconfigure on every move between links, the following signaling must   be performed:   1) Link-layer signaling required for handover and reauthentication.      For example, in 802.11 [7], this is the Reassociate message      together with 802.1x [8] reauthentication using EAP.   2) Active IP-level movement detection, including router reachability.      The Detecting Network Attachment (DNA) protocol [5] uses Router      Solicitation/Router Advertisement for this purpose.  In addition,      if SEcure Neighbor Discovery (SEND) [3] is used and the mobile      node does not have a certificate cached for the router, the mobile      node must use Certification Path Solicitation/Certification Path      Advertisement to obtain a certification path.   3) Two Multicast Listener Discovery (MLD) [14] REPORT messages, one      for each of the solicited node multicast addresses corresponding      to the link local address and the global address.   4) Two Neighbor Solicitation (NS) messages for duplicate address      detection, one for the link local address and one for the global      address.  If the addresses are unique, no response will be      forthcoming.   5) Two NS messages from the router for address resolution of the link      local and global addresses, and two Neighbor Advertisement      messages in response from the mobile node.   6) Binding Update/Binding Acknowledgement between the mobile node and      home agent to update the care of address binding.   7) Return routability signaling between the correspondent node and      mobile node to establish the binding key, consisting of one Home      Test Init/Home Test and Care of Test Init/Care of Test.   8) Binding Update/Binding Acknowledgement between the correspondent      node and mobile node for route optimization.   Note that Steps 1-2 may be necessary, even for intra-link mobility,   if the last-hop link protocol doesn't provide much help for IP   handover.  Steps 3-5 will be different if stateful address   configuration is used, since additional messages are required to   obtain the address.  Steps 6-8 are only necessary when Mobile IPv6 isKempf                        Informational                      [Page 5]

RFC 4831                      NETLMM Goals                    April 2007   used.  The result is approximately 18 messages at the IP level, where   the exact number depends on various specific factors, such as whether   or not the mobile node has a router certificate cached before a   mobile node can be ensured that it is established on a link and has   full IP connectivity.  In addition to handover related signaling, if   the mobile node performs Mobile IPv6 route optimization, it may be   required to renew its return routability key periodically (on the   order of every 7 minutes), even if it is not moving, resulting in   additional signaling.   The signaling required has a large impact on the performance of   handover, impacting Goal 1.  Perhaps more importantly, the aggregate   impact from many mobile nodes of such signaling on expensive shared   links (such as wireless where the capacity of the link cannot easily   be expanded) can result in reduced last-hop link capacity for data   traffic.  Additionally, in links where the end user is charged for IP   traffic, IP signaling is not without cost.   To address the issue of signaling impact described above, the goal is   that handover signaling volume from the mobile node to the network   should be no more than what is needed for the mobile node to perform   secure IP-level movement detection, in cases where no link-layer   support exists.  Furthermore, NETLMM should not introduce any   additional signaling during handover beyond what is required for IP-   level movement detection.  If link-layer support exists for IP-level   movement detection, the mobile node may not need to perform any   additional IP-level signaling after link-layer handover.3.3.  Goal 3: Location Privacy   In any IP network, there is a threat that an attacker can determine   the physical location of a network node from the node's topological   location.  Depending on how an operator deploys their network, an   operator may choose to assign subnet coverage in a way that is   tightly bound to geography at some timescale, or it may choose to   assign it in ways in which the threat of someone finding a node   physically based on its IP address is smaller.  Allowing the L2   attachment and L3 address to be less tightly bound is one tool for   reducing this threat to location privacy.   Mobility introduces an additional threat.  An attacker can track a   mobile node's geographical location in real-time, if the victim   mobile node must change its IP address as it moves from one subnet to   another through the covered geographical area.  If the granularity of   the mapping between the IP subnets and geographical area is small for   the particular link type in use, the attacker can potentially   assemble enough information to find the victim in real time.Kempf                        Informational                      [Page 6]

RFC 4831                      NETLMM Goals                    April 2007   In order to reduce the risk from location privacy compromises as a   result of IP address changes, the goal for NETLMM is to remove the   need to change IP address as a mobile node moves across links in an   access network.  Keeping the IP address fixed over a large   geographical region fuzzes out the resolution of the mapping between   the IP subnets and geographical area, regardless of how small the   natural deployment granularity may be.  This reduces the chance that   the attacker can deduce the precise geographic location of the mobile   node.3.4.  Goal 4: Limit Overhead in the Network   Access networks, including both the wired and wireless parts, tend to   have somewhat stronger bandwidth and router processing constraints   than the backbone.  In the wired part of the network, these   constraints are a function of the cost of laying fiber or wiring to   the wireless access points in a widely dispersed geographic area.  In   the wireless part of the network, these constraints are due to the   limitation on the number of bits per Hertz imposed by the physical   layer protocol.  Therefore, any solutions for localized mobility   management should minimize overhead within the access network.3.5.  Goal 5: Simplify Mobile Node Mobility Management Security by      Deriving from IP Network Access and/or IP Movement Detection      Security   Localized mobility management protocols that have host involvement   may require an additional security association between the mobile   node and the mobility anchor, and establishing this security   association may require additional signaling between the mobile node   and the mobility anchor (see [13] for an example).  The additional   security association requires extra signaling and therefore extra   time to negotiate.  Reducing the complexity of mobile-node-to-network   security for localized mobility management can therefore reduce   barriers to deployment and improve responsiveness.  Naturally, such   simplification must not come at the expense of maintaining strong   security guarantees for both the network and mobile node.   In NETLMM, the network (specifically, the MAG) derives the occurrence   of a mobility event, requiring a routing update for a mobile node   from link-layer handover signaling, or IP-layer movement detection   signaling from the mobile node.  This information is used to update   routing for the mobile node at the LMA.  The handover, or movement   detection signaling, must provide the network with proper   authentication and authorization so that the network can definitively   identify the mobile node and determine its authorization.  The   authorization may be at the IP level -- for example, using something   like SEND [3] to secure IP movement detection signaling -- or it atKempf                        Informational                      [Page 7]

RFC 4831                      NETLMM Goals                    April 2007   the link level.  Proper authentication and authorization must be   implemented on link-layer handover signaling and/or IP-level movement   detection signaling in order for the MAG to securely deduce mobile   node movement events.  Security threats to the NETLMM protocol are   discussed in [2].   The goal is that security for NETLMM mobile node mobility management   should derive from IP network access and/or IP movement detection   security, such as SEND or network access authentication, and not   require any additional security associations or additional signaling   between the mobile node and the network.3.6.  Goal 6: Link Technology Agnostic   The number of wireless link technologies available is growing, and   the growth seems unlikely to slow down.  Since the standardization of   a wireless link physical and medium access control layers is a time-   consuming process, reducing the amount of work necessary to interface   a particular wireless link technology to an IP network is necessary.   When the last-hop link is a wireless link, a localized mobility   management solution should ideally require minimal work to interface   with a new wireless link technology.   In addition, an edge mobility solution should provide support for   multiple wireless link technologies.  It is not required that the   localized mobility management solution support handover from one   wireless link technology to another without a change in the IP   address, but this possibility should not be precluded.   The goal is that the localized mobility management protocol should   not use any wireless link specific information for basic routing   management, though it may be used for other purposes, such as   securely identifying a mobile node.3.7.  Goal 7: Support for Unmodified Mobile Nodes   In the WLAN switching market, no modification of the software on the   mobile node is required to achieve localized mobility management.   Being able to accommodate unmodified mobile nodes enables a service   provider to offer service to as many customers as possible, the only   constraint being that the customer is authorized for network access.   Another advantage of minimizing mobile node software for localized   mobility management is that multiple global mobility management   protocols can be supported.  There are a variety of global mobility   management protocols that might also need support, including   proprietary or link technology-specific protocols needing support for   backward compatibility reasons.  Within the Internet, both HostKempf                        Informational                      [Page 8]

RFC 4831                      NETLMM Goals                    April 2007   Identity Protocol (HIP) [11] and IKEv2 Mobility and Multihoming   (MOBIKE) [6] are likely to need support in addition to Mobile IPv6   [9], and Mobile IPv4 [12] support may also be necessary.   Note that this goal does NOT mean that the mobile node has no   software at all associated with mobility.  The mobile node must have   some kind of global mobility protocol if it is to move from one   domain of edge mobility support to another and maintain session   continuity, although no global mobility protocol is required if the   mobile node only moves within the coverage area of the localized   mobility management protocol or no session continuity is required   during global movement.  Also, if the last-hop link is a wireless   link, every wireless link protocol requires handover support on the   mobile node in the physical and medium access control layers,   typically in the wireless interface driver.  Information passed from   the medium access control layer to the IP layer on the mobile node   may be necessary to trigger IP signaling for IP handover.  Such   movement detection support at the IP level may be required in order   to determine whether the mobile node's default router is still   reachable after the move to a new access point has occurred at the   medium access control layer.  Whether or not such support is required   depends on whether the medium access control layer can completely   hide link movement from the IP layer.  For cellular type wireless   link protocols, the mobile node and network undergo an extensive   negotiation at the medium access control layer prior to handover, so   it may be possible to trigger a routing update without any IP   protocol involvement.  However, for a wireless link protocol such as   IEEE 802.11 [7] in which the decision for handover is entirely in the   hands of the mobile node, IP-layer movement detection signaling from   the mobile node may be required to trigger a routing update.   The goal is that the localized mobility management solution should be   able to support any mobile node that joins the link and that has an   interface that can communicate with the network, without requiring   localized mobility management software on the mobile node.3.8.  Goal 8: Support for IPv4 and IPv6   While most of this document is written with IPv6 in mind, localized   mobility management is a problem in IPv4 networks as well.  A   solution for localized mobility that works for both versions of IP is   desirable, though the actual protocol may be slightly different due   to the technical details of how each IP version works.  From Goal 7   (Section 3.7), minimizing mobile node support for localized mobility   means that ideally no IP version-specific changes should be required   on the mobile node for localized mobility, and that global mobility   protocols for both IPv4 and IPv6 should be supported.  Any IP   version-specific features should be confined to the network protocol.Kempf                        Informational                      [Page 9]

RFC 4831                      NETLMM Goals                    April 20073.9.  Goal 9: Reuse of Existing Protocols Where Sensible   Many existing protocols are available as Internet Standards upon   which the NETLMM protocol can be built.  The design of the protocol   should have a goal to reuse existing protocols where it makes   architectural and engineering sense to do so.  However, the design   should not attempt to reuse existing protocols where there is no real   architectural or engineering reason.  For example, the suite of   Internet Standards contains several good candidate protocols for the   transport layer, so there is no real need to develop a new transport   protocol specifically for NETLMM.  Reuse is clearly a good   engineering decision in this case, since backward compatibility with   existing protocol stacks is important.  On the other hand, the   network-based, localized mobility management functionality being   introduced by NETLMM is a new piece of functionality, and therefore   any decision about whether to reuse an existing global mobility   management protocol should carefully consider whether reusing such a   protocol really meets the needs of the functional architecture for   network-based localized mobility management.  The case for reuse is   not so clear in this case, since there is no compelling backward   compatibility argument.3.10.  Goal 10: Localized Mobility Management Independent of Global       Mobility Management   Localized mobility management should be implementable and deployable   independently of any global mobility management protocol.  This   enables the choice of local and global mobility management to be made   independently of particular protocols that are implemented and   deployed to solve the two different sorts of mobility management   problems.  The operator can choose a particular localized mobility   management protocol according to the specific features of their   access network.  It can subsequently upgrade the localized mobility   management protocol on its own, without even informing the mobile   nodes.  Similarly, the mobile nodes can use a global mobility   management protocol that best suits their requirements, or not use   one at all.  Also, a mobile node can move into a new access network   without having to check that it understands the localized mobility   management protocol being used there.   The goal is that the implementation and deployment of the localized   mobility management protocol should not restrict, or be restricted   by, the choice of global mobility management protocol.Kempf                        Informational                     [Page 10]

RFC 4831                      NETLMM Goals                    April 20073.11.  Goal 11: Configurable Data Plane Forwarding between Local       Mobility Anchor and Mobile Access Gateway   Different network operators may require different types of forwarding   options between the LMA and the MAGs for mobile node data plane   traffic.  An obvious forwarding option that has been used in past   IETF localized mobility management protocols is IP-IP encapsulation   for bidirectional tunneling.  The tunnel endpoints are the LMA and   the MAGs.  But other options are possible.  Some network deployments   may prefer routing-based solutions.  Others may require security   tunnels using IPsec Encapsulating Security Payload (ESP)   encapsulation if part of the localized mobility management domain   runs over a public access network and the network operator wants to   protect the traffic.   A goal of the NETLMM protocol is to allow the forwarding between the   LMA and MAGs to be configurable depending on the particulars of the   network deployment.  Configurability is not expected to be dynamic,   as in controlled by the arrival of a mobile node; but rather,   configuration is expected to be similar in timescale to configuration   for routing.  The NETLMM protocol may designate a default forwarding   mechanism.  It is also possible that additional work may be required   to specify the interaction between a particular forwarding mechanism   and the NETLMM protocol, but this work is not in scope of the NETLMM   base protocol.4.  Security Considerations   There are two kinds of security issues involved in network-based   localized mobility management: security between the mobile node and   the network, and security between network elements that participate   in the NETLMM protocol.  The security-related goals in this document,   described inSection 3.3 and 3.5, focus on the former, because those   are unique to network-based mobility management. The threat analysis   document [2] contains a more detailed discussion of both kinds of   threats, which the protocol design must address.5.  Acknowledgements   The authors would like to acknowledge the following people for   particularly diligent reviewing: Vijay Devarapalli, Peter McCann,   Gabriel Montenegro, Vidya Narayanan, Pekka Savola, and Fred Templin.Kempf                        Informational                     [Page 11]

RFC 4831                      NETLMM Goals                    April 20076.  Normative References   [1]  Kempf, J., Ed., "Problem Statement for Network-Based Localized        Mobility Management (NETLMM)",RFC 4830, April 2007.   [2]  Vogt, C., and Kempf, J., "Security Threats to Network-Based        Localized Mobility Management (NETLMM)",RFC 4832, April 2007.7.  Informative References   [3]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure        Neighbor Discovery (SEND)",RFC 3971, March 2005.   [4]  Carpenter, B., "Architectural Principles of the Internet",RFC1958, June 1996.   [5]  Choi, JH. and G. Daley, "Goals of Detecting Network Attachment        in IPv6",RFC 4135, August 2005.   [6]  Eronen, P., "IKEv2 Mobility and Multihoming Protocol (MOBIKE)",RFC 4555, June 2006.   [7]  IEEE, "Wireless LAN Medium Access Control (MAC)and Physical        Layer (PHY) specifications", IEEE Std. 802.11, 1999.   [8]  IEEE, "Port-based Access Control", IEEE LAN/MAN Standard 802.1x,        June, 2001.   [9]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in        IPv6",RFC 3775, June 2004.   [10] Manner, J. and M. Kojo, "Mobility Related Terminology",RFC3753, June 2004.   [11] Moskowitz, R. and P. Nikander, "Host Identity Protocol (HIP)        Architecture",RFC 4423, May 2006.   [12] Perkins, C., "IP Mobility Support for IPv4",RFC 3344, August        2002.   [13] Soliman, H., Castelluccia, C., El Malki, K., and L. Bellier,        "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)",RFC4140, August 2005.   [14] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2        (MLDv2) for IPv6",RFC 3810, June 2004.Kempf                        Informational                     [Page 12]

RFC 4831                      NETLMM Goals                    April 20078.  Contributors   Kent Leung   Cisco Systems, Inc.   170 West Tasman Drive   San Jose, CA 95134   USA   EMail: kleung@cisco.com   Phil Roberts   Motorola Labs   Schaumberg, IL   USA   EMail: phil.roberts@motorola.com   Katsutoshi Nishida   NTT DoCoMo Inc.   3-5 Hikarino-oka, Yokosuka-shi   Kanagawa,   Japan   Phone: +81 46 840 3545   EMail: nishidak@nttdocomo.co.jp   Gerardo Giaretta   Telecom Italia Lab   via G. Reiss Romoli, 274   10148 Torino   Italy   Phone: +39 011 2286904   EMail: gerardo.giaretta@tilab.com   Marco Liebsch   NEC Network Laboratories   Kurfuersten-Anlage 36   69115 Heidelberg   Germany   Phone: +49 6221-90511-46   EMail: marco.liebsch@ccrle.nec.deEditor's Address   James Kempf   DoCoMo USA Labs   181 Metro Drive, Suite 300   San Jose, CA 95110   USA   Phone: +1 408 451 4711   EMail: kempf@docomolabs-usa.comKempf                        Informational                     [Page 13]

RFC 4831                      NETLMM Goals                    April 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 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 inBCP 78 andBCP 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 athttp://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.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Kempf                        Informational                     [Page 14]