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INFORMATIONAL
Internet Engineering Task Force (IETF)                       D. Liu, Ed.Request for Comments: 7429                                  China MobileCategory: Informational                                  JC. Zuniga, Ed.ISSN: 2070-1721                                             InterDigital                                                                P. Seite                                                                  Orange                                                                 H. Chan                                                     Huawei Technologies                                                           CJ. Bernardos                                                                    UC3M                                                            January 2015Distributed Mobility Management: Current Practices and Gap AnalysisAbstract   This document analyzes deployment practices of existing IP mobility   protocols in a distributed mobility management environment.  It then   identifies existing limitations when compared to the requirements   defined for a distributed mobility management solution.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7429.Liu, et al.                   Informational                     [Page 1]

RFC 7429             DMM Best Practices Gap Analysis        January 2015Copyright Notice   Copyright (c) 2015 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .32.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .33.  Functions of Existing Mobility Protocols  . . . . . . . . . .44.  DMM Practices . . . . . . . . . . . . . . . . . . . . . . . .54.1.  Assumptions . . . . . . . . . . . . . . . . . . . . . . .54.2.  IP Flat Wireless Network  . . . . . . . . . . . . . . . .64.2.1.  Host-Based IP DMM Practices . . . . . . . . . . . . .74.2.2.  Network-Based IP DMM Practices  . . . . . . . . . . .124.3.  Flattening 3GPP Mobile Network Approaches . . . . . . . .155.  Gap Analysis  . . . . . . . . . . . . . . . . . . . . . . . .195.1.  Distributed Mobility Management - REQ1  . . . . . . . . .19     5.2.  Bypassable Network-Layer Mobility Support for Each           Application Session - REQ2  . . . . . . . . . . . . . . .215.3.  IPv6 Deployment - REQ3  . . . . . . . . . . . . . . . . .225.4.  Considering Existing Mobility Protocols - REQ4  . . . . .23     5.5.  Coexistence with Deployed Networks/Hosts and Operability           across Different Networks - REQ5  . . . . . . . . . . . .235.6.  Operation and Management Considerations - REQ6  . . . . .235.7.  Security Considerations - REQ7  . . . . . . . . . . . . .245.8.  Multicast Considerations - REQ8  . . .  . . . . . . . . .255.9.  Summary . . . . . . . . . . . . . . . . . . . . . . . . .256.  Security Considerations . . . . . . . . . . . . . . . . . . .287.  References  . . . . . . . . . . . . . . . . . . . . . . . . .287.1.  Normative References  . . . . . . . . . . . . . . . . . .287.2.  Informative References  . . . . . . . . . . . . . . . . .28   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .33   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .33Liu, et al.                   Informational                     [Page 2]

RFC 7429             DMM Best Practices Gap Analysis        January 20151.  Introduction   Existing network-layer mobility management protocols have primarily   employed a mobility anchor to ensure connectivity of a mobile node by   forwarding packets destined to, or sent from, the mobile node after   the node has moved to a different network.  The mobility anchor has   been centrally deployed in the sense that the traffic of millions of   mobile nodes in an operator network is typically managed by the same   anchor.  This centralized deployment of mobility anchors to manage IP   sessions poses several problems.  In order to address these problems,   a distributed mobility management (DMM) architecture has been   proposed.  This document investigates whether it is feasible to   deploy current IP mobility protocols in a DMM scenario in a way that   can fulfill the requirements as defined in [RFC7333], discusses   current deployment practices of existing mobility protocols, and   identifies the limitations (gaps) in these practices from the   standpoint of satisfying DMM requirements.  The analysis is primarily   towards IPv6 deployment but can be seen to also apply to IPv4   whenever there are IPv4 counterparts equivalent to the IPv6 mobility   protocols.   The rest of this document is organized as follows:Section 3 analyzes   existing IP mobility protocols by examining their functions and how   these functions can be configured and used to work in a DMM   environment,Section 4 presents the current practices of IP wireless   networks and 3GPP architectures (both network- and host-based   mobility protocols are considered), andSection 5 presents the gap   analysis with respect to the current practices.2.  Terminology   All general mobility-related terms and their acronyms used in this   document are to be interpreted as defined in the Mobile IPv6 base   specification [RFC6275], in the Proxy Mobile IPv6 specification   [RFC5213], and in the Distributed Mobility Management Requirements   [RFC7333].  These terms include mobile node (MN), correspondent node   (CN), home agent (HA), local mobility anchor (LMA), mobile access   gateway (MAG), centrally deployed mobility anchors, distributed   mobility management, hierarchical mobile network, flatter mobile   network, and flattening mobile network.   In addition, this document also introduces some definitions of IP   mobility functions inSection 3.   In this document there are also references to a "distributed mobility   management environment."  By this term, we refer to a scenario in   which the IP mobility, access network, and routing solutions allowLiu, et al.                   Informational                     [Page 3]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   for setting up IP networks so that traffic is distributed in an   optimal way without relying on centrally deployed mobility anchors to   manage IP mobility sessions.3.  Functions of Existing Mobility Protocols   The host-based Mobile IPv6 (MIPv6) [RFC6275] and its network-based   extension, Proxy Mobile IPv6 (PMIPv6) [RFC5213], as well as   Hierarchical Mobile IPv6 (HMIPv6) [RFC5380], are logically   centralized mobility management approaches addressing primarily   hierarchical mobile networks.  Although these approaches are   centralized, they have important mobility management functions   resulting from years of extensive work to develop and to extend these   functions.  It is therefore useful to take these existing functions   and examine them in a DMM scenario in order to understand how to   deploy the existing mobility protocols to provide distributed   mobility management.   The main mobility management functions of MIPv6, PMIPv6, and HMIPv6   are the following:   1.  Anchoring Function (AF): allocation to a mobile node of an IP       address, i.e., Home Address (HoA), or prefix, i.e., Home Network       Prefix (HNP), topologically anchored by the advertising node.       That is, the anchor node is able to advertise a connected route       into the routing infrastructure for the allocated IP prefixes.       This function is a control-plane function.   2.  Internetwork Location Management (LM) function: managing and       keeping track of the internetwork location of an MN.  The       location information may be a binding of the advertised IP       address/prefix, e.g., HoA or HNP, to the IP routing address of       the MN, or it may be a binding of a node that can forward packets       destined to the MN.  It is a control-plane function.       In a client-server protocol model, location query and update       messages may be exchanged between a Location Management client       (LMc) and a Location Management server (LMs).   3.  Forwarding Management (FM) function: packet interception and       forwarding to/from the IP address/prefix assigned to the MN,       based on the internetwork location information, either to the       destination or to some other network element that knows how to       forward the packets to their destination.       FM may optionally be split into the control plane (FM-CP) and       data plane (FM-DP).Liu, et al.                   Informational                     [Page 4]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   In Mobile IPv6, the home agent (HA) typically provides the AF; the   LMs is at the HA, whereas the LMc is at the MN; the FM function is   distributed between the ends of the tunnel at the HA and the MN.   In Proxy Mobile IPv6, the local mobility anchor (LMA) provides the   AF; the LMs is at the LMA, whereas the LMc is at the MAG; the FM   function is distributed between the ends of the tunnel at the LMA and   the MAG.   In HMIPv6 [RFC5380], the Mobility Anchor Point (MAP) serves as a   location information aggregator between the LMs at the HA and the LMc   at the MN.  The MAP also provides the FM function to enable tunneling   between HA and itself, as well as tunneling between the MN and   itself.4.  DMM Practices   This section documents deployment practices of existing mobility   protocols to satisfy distributed mobility management requirements.   This description considers both IP wireless, e.g., evolved Wi-Fi   hotspots, and 3GPP flattening mobile networks.   While describing the current DMM practices, the section provides   references to the generic mobility management functions described inSection 3 as well as some initial hints on the identified gaps with   respect to the DMM requirements documented in [RFC7333].4.1.  Assumptions   There are many different approaches that can be considered to   implement and deploy a distributed anchoring and mobility solution.   The focus of the gap analysis is on certain current mobile network   architectures and standardized IP mobility solutions, considering any   kind of deployment options that do not violate the original protocol   specifications.  In order to limit the scope of our analysis of DMM   practices, we consider the following list of technical assumptions:   1.  Both host- and network-based solutions are considered.   2.  Solutions should allow selecting and using the most appropriate       IP anchor among a set of available candidates.   3.  Mobility management should be realized by the preservation of the       IP address across the different points of attachment (i.e.,       provision of IP address continuity).  This is in contrast to       certain transport-layer-based approaches such as Stream Control       Transmission Protocol (SCTP) [RFC4960] or application-layer       mobility.Liu, et al.                   Informational                     [Page 5]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   Applications that can cope with changes in the MN's IP address do not   depend on IP mobility management protocols such as DMM.  Typically, a   connection manager, together with the operating system, will   configure the source address selection mechanism of the IP stack.   This might involve identifying application capabilities and   triggering the mobility support accordingly.  Further considerations   on application management and source address selection are out of the   scope of this document, but the reader might consult [RFC6724].4.2.  IP Flat Wireless Network   This section focuses on common IP wireless network architectures and   how they can be flattened from an IP mobility and anchoring point of   view using common and standardized protocols.  We take Wi-Fi as a   useful wireless technology since it is widely known and deployed   nowadays.  Some representative examples of Wi-Fi deployment   architectures are depicted in Figure 1.                      +-------------+             _----_     +---+            |   Access    |           _(      )_     |AAA|. . . . . . | Aggregation |----------( Internet )     +---+            |   Gateway   |           (_      _)                      +-------------+             '----'                         |  |   |                         |  |   +-------------+                         |  |                 |                         |  |              +-----+         +---------------+  |              | AR  |         |                  |              +--+--+      +-----+            +-----+         *----+----*      | RG  |            | WLC |        (    LAN    )      +-----+            +-----+         *---------*         .                /   \            /     \        / \          +-----+ +-----+  +-----+   +-----+       /   \         |Wi-Fi| |Wi-Fi|  |Wi-Fi|   |Wi-Fi|     MN1   MN2       | AP1 | | AP2 |  | AP3 |   | AP4 |                     +-----+ +-----+  +-----+   +-----+                        .                .                       / \              / \                      /   \            /   \                     MN3  MN4         MN5  MN6                 Figure 1: IP Wi-Fi Network Architectures   In Figure 1, three typical deployment options are shown   [COMMUNITY-WIFI].  On the left-hand side of the figure, mobile nodes   MN1 and MN2 directly connect to a Residential Gateway (RG) at the   customer premises.  The RG hosts the 802.11 Access Point (AP)Liu, et al.                   Informational                     [Page 6]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   function to enable wireless Layer 2 access connectivity and also   provides Layer 3 routing functions.  In the middle of the figure,   mobile nodes MN3 and MN4 connect to Wi-Fi access points AP1 and AP2   that are managed by a Wireless LAN Controller (WLC), which performs   radio resource management on the APs, domain-wide mobility policy   enforcement, and centralized forwarding function for the user   traffic.  The WLC could also implement Layer 3 routing functions or   attach to an access router (AR).  Last, on the right-hand side of the   figure, access points AP3 and AP4 are directly connected to an access   router.  This can also be used as a generic connectivity model.   IP mobility protocols can be used to provide heterogeneous network   mobility support to users, e.g., handover from Wi-Fi to cellular   access.  Two kinds of protocols can be used: Proxy Mobile IPv6   [RFC5213] or Mobile IPv6 [RFC5555], with the role of mobility anchor   (e.g., local mobility anchor or home agent) typically being played by   the edge router of the mobile network [SDO-3GPP.23.402].   Although this section has made use of the example of Wi-Fi networks,   there are other flattening mobile network architectures specified,   such as Worldwide Interoperability for Microwave Access (WiMAX)   [IEEE.802-16.2009], which integrates both host- and network-based IP   mobility functions.   Existing IP mobility protocols can also be deployed in a flatter   manner so that the anchoring and access aggregation functions are   distributed.  We next describe several practices for the deployment   of existing mobility protocols in a distributed mobility management   environment.  The analysis in this section is limited to protocol   solutions based on existing IP mobility protocols, either host- or   network-based, such as Mobile IPv6 [RFC6275] [RFC5555], Proxy Mobile   IPv6 (PMIPv6) [RFC5213] [RFC5844], and Network Mobility (NEMO) Basic   Support Protocol [RFC3963].  Extensions to these base protocol   solutions are also considered.  The analysis is divided into two   parts: host- and network-based practices.4.2.1.  Host-Based IP DMM Practices   Mobile IPv6 (MIPv6) [RFC6275] and its extension to support mobile   networks, the NEMO Basic Support protocol (hereafter, simply referred   to as NEMO) [RFC3963], are well-known, host-based IP mobility   protocols.  They depend on the function of the home agent (HA), a   centralized anchor, to provide mobile nodes (hosts and routers) with   mobility support.  In these approaches, the home agent typically   provides the AF, FM function, and Location Management server (LMs)   functions.  The mobile node possesses the Location Management client   (LMc) function and the FM function to enable tunneling between the HALiu, et al.                   Informational                     [Page 7]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   and itself.  We next describe some practices that show how MIPv6/NEMO   and several other protocol extensions can be deployed in a   distributed mobility management environment.   One approach to distribute the anchors can be to deploy several HAs   (as shown in Figure 2), and assign the topologically closest anchor   to each MN [RFC4640] [RFC5026] [RFC6611].  In the example shown in   Figure 2, the mobile node MN1 is assigned to the home agent HA1 and   uses a home address anchored by HA1 to communicate with the   correspondent node CN1.  Similarly, the mobile node MN2 is assigned   to the home agent HA2 and uses a home address anchored by HA2 to   communicate with the correspondent node CN2.  Note that MIPv6/NEMO   specifications do not prevent the simultaneous use of multiple home   agents by a single mobile node.  In this deployment model, the mobile   node can use several anchors at the same time, each of them anchoring   IP flows initiated at a different point of attachment.  However,   there is currently no mechanism specified in IETF standard to enable   an efficient dynamic discovery of available anchors and the selection   of the most suitable one.Liu, et al.                   Informational                     [Page 8]

RFC 7429             DMM Best Practices Gap Analysis        January 2015    <-INTERNET-> <- HOME NETWORK -> <------- ACCESS NETWORK ------->     +-----+                            +-----+       +--------+     | CN1 |---                      ===| AR1 |=======|   MN1  |     +-----+   \   +-----------+   //   +-----+       |(FM,LMc)|                ---|    HA1    |===                   +--------+                   |(AF,FM,LMs)|        +-----+       (anchored                   +-----------+        | AR2 |          at HA1)                                        +-----+     +-----+       +-----------+     | CN2 |-------|    HA2    |===     +-----+       |(AF,FM,LMs)|   \\   +-----+=======+--------+                   +-----------+     ===| AR3 |       |   MN2  |                                        +-----+-------|(FM,LMc)|     +-----+                              /           +--------+     | CN3 |-----------------------------/            (anchored     +-----+                                             at HA2)                                        +-----+                                        | AR4 |                                        +-----+    CN1   CN2  CN3   HA1   HA2         AR1   AR3      MN1    MN2     |     |    |     |     |           |     |        |      |     |<-------------->|<======tunnel====+=============>|      | BT mode     |     |    |     |     |           |     |        |      |     |     |<-------------->|<======tunnel====+==============>| BT mode     |     |    |     |     |           |     |        |      |     |     |    |<----------------------------+-------------->| RO mode     |     |    |     |     |           |     |        |      |      Figure 2: Distributed Operation of Mobile IPv6 (BT and RO)/NEMO   One goal of the deployment of mobility protocols in a distributed   mobility management environment is to avoid the suboptimal routing   caused by centralized anchoring.  Here, the Route Optimization (RO)   support provided by Mobile IPv6 can be used to achieve a flatter IP   data forwarding.  By default, Mobile IPv6 and NEMO use the so-called   Bidirectional Tunnel (BT) mode, in which data traffic is always   encapsulated between the MN and its HA before being directed to any   other destination.  The RO mode allows the MN to update its current   location on the CNs and then use the direct path between them.  Using   the example shown in Figure 2, MN1 and MN2 are using BT mode with CN1   and CN2, respectively, while MN2 is in RO mode with CN3.  However,   the RO mode has several drawbacks:Liu, et al.                   Informational                     [Page 9]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   o  The RO mode is only supported by Mobile IPv6.  There is no route      optimization support standardized for the NEMO protocol because of      the security problems posed by extending return routability tests      for prefixes, although many different solutions have been proposed      [RFC4889].   o  The RO mode requires signaling that adds some protocol overhead.   o  The signaling required to enable RO involves the home agent and is      repeated periodically for security reasons [RFC4225].  Therefore,      the HA remains a single point of failure.   o  The RO mode requires support from the CN.   Notwithstanding these considerations, the RO mode does offer the   possibility of substantially reducing traffic through the home agent,   in cases when it can be supported by the relevant correspondent   nodes.  Note that a mobile node can also use its Care-of Address   (CoA) directly [RFC5014] when communicating with CNs on the same link   or anywhere in the Internet, although no session continuity support   would be provided by the IP stack in this case.   HMIPv6 [RFC5380], as shown in Figure 3, is another host-based IP   mobility extension that can be considered as a complement to provide   a less centralized mobility deployment.  It allows the reduction of   the amount of mobility signaling as well as improving the overall   handover performance of Mobile IPv6 by introducing a new hierarchy   level to handle local mobility.  The Mobility Anchor Point (MAP)   entity is introduced as a local mobility handling node deployed   closer to the mobile node.  It provides LM intermediary function   between the LMs at the HA and the LMc at the MN.  It also performs   the FM function to tunnel with the HA and also with the MN.Liu, et al.                   Informational                    [Page 10]

RFC 7429             DMM Best Practices Gap Analysis        January 2015    <INTERNET> <- HOME NETWORK -> <---------- ACCESS NETWORK ---------->                                                   LCoA anchored                                                      at AR1                                                       +---+  +--------+                                                    ===|AR1|==|   MN1  |     +-----+    +-----------+      +----------+   //   +---+  |(FM,LMc)|     | CN1 |----|    HA1    |======|   MAP1   |===            +--------+     +-----+    |(AF,FM,LMs)|     /|(AF,FM,LM)|        +---+        HoA,                +-----------+    / +----------+        |AR2|       RCoA,                 HoA anchored   /  RCoA anchored       +---+       LCoA                    at HA1     /      at MAP1                              /                        +---+                             /                         |AR3|     +-----+                /      +----------+        +---+     | CN2 |----------------       |   MAP2   |     +-----+                       |(AF,FM,LM)|        +---+                                   +----------+        |AR4|                                                       +---+    CN1   CN2        HA1               MAP1             AR1     MN1     |     |          |                 |                |       |     |<-------------->|<===============>|<====tunnel============>| HoA     |     |          |                 |                |       |     |     |<-------------------------->|<====tunnel============>| RCoA     |     |          |                 |                |       |                    Figure 3: Hierarchical Mobile IPv6   When HMIPv6 is used, the MN has two different temporary addresses:   the Regional Care-of Address (RCoA) and the Local Care-of Address   (LCoA).  The RCoA is anchored at one MAP, which plays the role of   local home agent, while the LCoA is anchored at the access-router   level.  The mobile node uses the RCoA as the CoA that is signaled to   its home agent.  Therefore, while roaming within a local domain   handled by the same MAP, the mobile node does not need to update its   home agent, i.e., the mobile node does not change its RCoA.   The use of HMIPv6 enables a form of route optimization, since a   mobile node may decide to directly use the RCoA as the source address   for a communication with a given correspondent node, particularly if   the MN does not expect to move outside the local domain during the   lifetime of the communication.  This can be seen as a potential DMM   mode of operation, though it fails to provide session continuity if   and when the MN moves outside the local domain.  In the example shown   in Figure 3, MN1 is using its global HoA to communicate with CN1,   while it is using its RCoA to communicate with CN2.Liu, et al.                   Informational                    [Page 11]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   Furthermore, a local domain might have several MAPs deployed, thus   enabling different kinds of HMIPv6 deployments that are flattening   and distributed.  The HMIPv6 specification supports a flexible   selection of the MAP, including selections based on the expected   mobility pattern of the MN or on the distance between the MN and the   MAP.   Another extension that can be used to help with distributing mobility   management functions is the Home Agent switch specification   [RFC5142], which defines a new mobility header to signal to a mobile   node that it should acquire a new home agent.  [RFC5142] does not   specify the case of changing the mobile node's home address, as that   might imply loss of connectivity for ongoing persistent connections.   Nevertheless, that specification could be used to force the change of   home agent in those situations where there are no active persistent   data sessions that cannot cope with a change of home address.   There are other host-based approaches standardized that can be used   to provide mobility support.  For example, IKEv2 Mobility and   Multihoming (MOBIKE) [RFC4555] allows a mobile node encrypting   traffic through Internet Key Exchange Protocol Version 2 (IKEv2)   [RFC7296] to change its point of attachment while maintaining a   Virtual Private Network (VPN) session.  The MOBIKE protocol allows   updating the VPN Security Associations (SAs) in cases where the base   connection initially used is lost and needs to be re-established.   The use of the MOBIKE protocol avoids having to perform an IKEv2   renegotiation.  Similar considerations to those made for Mobile IPv6   can be applied to MOBIKE; though MOBIKE is best suited for situations   where the address of at least one endpoint is relatively stable and   can be discovered using existing mechanisms such as DNS.   Extensions have been defined to the mobility protocol to optimize the   handover performance.  Mobile IPv6 Fast Handovers (FMIPv6) [RFC5568]   is the extension to optimize handover latency.  It defines new access   router discovery mechanism before handover to reduce the new network   discovery latency.  It also defines a tunnel between the previous   access router and the new access router to reduce the packet loss   during handover.  The Candidate Access Router Discovery (CARD)   [RFC4066] and Context Transfer Protocol (CXTP) [RFC4067] protocols   were standardized to improve the handover performance.  The DMM   deployment practice discussed in this section can also use those   extensions to improve the handover performance.4.2.2.  Network-Based IP DMM Practices   Proxy Mobile IPv6 (PMIPv6) [RFC5213] is the main network-based IP   mobility protocol specified for IPv6.  Proxy Mobile IPv4 [RFC5844]   defines some IPv4 extensions.  With network-based IP mobilityLiu, et al.                   Informational                    [Page 12]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   protocols, the LMA typically provides the AF, FM function, and   Location Management server (LMs) function.  The mobile access gateway   (MAG) provides the Location Management client (LMc) function and FM   function to tunnel with LMA.  PMIPv6 is architecturally almost   identical to MIPv6, as the mobility signaling and routing between LMA   and MAG in PMIPv6 is similar to those between the HA and MN in MIPv6.   The required mobility functionality at the MN is provided by the MAG   so that the involvement in mobility support by the MN is not   required.   We next describe some practices that show how network-based mobility   protocols and several other protocol extensions can be deployed in a   distributed mobility management environment.   One way to decentralize Proxy Mobile IPv6 operation can be to deploy   several LMAs and use some selection criteria to assign LMAs to   attaching mobile nodes.  An example of this type of assignment is   shown in Figure 4.  As with the client-based approach, a mobile node   may use several anchors at the same time, each of them anchoring IP   flows initiated at a different point of attachment.  This assignment   can be static or dynamic.  The main advantage of this simple approach   is that the IP address anchor, i.e., the LMA, could be placed closer   to the mobile node.  Therefore, the resulting paths are close to   optimal.  On the other hand, as soon as the mobile node moves, the   resulting path will start deviating from the optimal one.Liu, et al.                   Informational                    [Page 13]

RFC 7429             DMM Best Practices Gap Analysis        January 2015    <INTERNET> <--- HOME NETWORK ---> <------ ACCESS NETWORK ------->                                                +--------+      +---+                                         =======|  MAG1  |------|MN1|     +-----+       +-----------+       //       |(FM,LMc)|      +---+     | CN1 |-------|    LMA1   |=======         +--------+     +-----+       |(AF,FM,LMs)|                   +-----------+                +--------+     +-----+                                    |  MAG2  |     | CN2 |---                                 |(FM,LMc)|     +-----+   \   +-----------+                +--------+                ---|    LMA2   |=======     +-----+       |(AF,FM,LMs)|       \\       +--------+      +---+     | CN3 |       +-----------+         =======|  MAG3  |------|MN2|     +-----+                                    |(FM,LMc)|      +---+                                                +--------+    CN1   CN2        LMA1  LMA2                  MAG1 MAG3     MN1  MN2     |     |          |     |                     |    |        |    |     |<-------------->|<===========tunnel========>|<----------->|    |     |     |          |     |                     |    |        |    |     |     |<-------------->|<=====tunnel=============>|<----------->|     |     |          |     |                     |    |        |    |           Figure 4: Distributed Operation of Proxy Mobile IPv6   In a similar way to the host-based IP mobility case, network-based IP   mobility has some extensions defined to mitigate the suboptimal   routing issues that may arise due to the use of a centralized anchor.   The Local Routing extensions [RFC6705] enable optimal routing in   Proxy Mobile IPv6 in three cases: i) when two communicating MNs are   attached to the same MAG and LMA, ii) when two communicating MNs are   attached to different MAGs but to the same LMA, and iii) when two   communicating MNs are attached to the same MAG but have different   LMAs.  In these three cases, data traffic between the two mobile   nodes does not traverse the LMA(s), thus providing some form of path   optimization, since the traffic is locally routed at the edge.  The   main disadvantage of this approach is that it only tackles the MN-to-   MN communication scenario and only under certain circumstances.   An interesting extension that can also be used to facilitate the   deployment of network-based mobility protocols in a distributed   mobility management environment is the support of an LMA runtime   assignment described in [RFC6463].  This extension specifies a   runtime LMA assignment functionality and corresponding mobility   options for Proxy Mobile IPv6.  This runtime LMA assignment takes   place during the Proxy Binding Update / Proxy Binding Acknowledgment   message exchange between a mobile access gateway and an LMA.  While   this mechanism is mainly aimed for load-balancing purposes, it can   also be used to select an optimal LMA from the routing point of view.Liu, et al.                   Informational                    [Page 14]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   A runtime LMA assignment can be used to change the assigned LMA of an   MN, for example, in cases when the mobile node does not have any   active session or when the running sessions can survive an IP address   change.  Note that several possible dynamic LMA discovery solutions   can be used, as described in [RFC6097].4.3.  Flattening 3GPP Mobile Network Approaches   The 3GPP is the standards development organization that specifies the   3rd generation mobile network and the Evolved Packet System (EPS)   [SDO-3GPP.23.402], which mainly comprises the Evolved Packet Core   (EPC) and a new radio access network, usually referred to as LTE   (Long Term Evolution).   Architecturally, the 3GPP EPC network is similar to an IP wireless   network running PMIPv6 or MIPv6, as it relies on the Packet Data   Network Gateway (P-GW) anchoring services to provide mobile nodes   with mobility support (see Figure 5).  There are client-based and   network-based mobility solutions in 3GPP, which for simplicity will   be analyzed together.  We next describe how 3GPP mobility protocols   and several other completed or ongoing extensions can be deployed to   meet some of the DMM requirements [RFC7333].Liu, et al.                   Informational                    [Page 15]

RFC 7429             DMM Best Practices Gap Analysis        January 2015             +---------------------------------------------------------+             |                           PCRF                          |             +-----------+--------------------------+----------------+-+                         |                          |                |    +----+   +-----------+------------+    +--------+-----------+  +-+-+    |    |   |          +-+           |    |  Core Network      |  |   |    |    |   | +------+ |S|__         |    | +--------+  +---+  |  |   |    |    |   | |GERAN/|_|G|  \        |    | |  HSS   |  |   |  |  |   |    |    +-----+ UTRAN| |S|   \       |    | +---+----+  |   |  |  | E |    |    |   | +------+ |N|  +-+-+    |    |     |       |   |  |  | x |    |    |   |          +-+ /|MME|    |    | +---+----+  |   |  |  | t |    |    |   | +---------+ / +---+    |    | |  3GPP  |  |   |  |  | e |    |    +-----+ E-UTRAN |/           |    | |  AAA   |  |   |  |  | r |    |    |   | +---------+\           |    | | SERVER |  |   |  |  | n |    |    |   |             \ +----+   |    | +--------+  |   |  |  | a |    |    |   |   3GPP AN    \|S-GW+---- S5---------------+ P |  |  | l |    |    |   |               +----+   |    |             | - |  |  |   |    |    |   +------------------------+    |             | G |  |  | I |    | UE |                                 |             | W |  |  | P |    |    |   +------------------------+    |             |   +-----+   |    |    |   |+-------------+ +------+|    |             |   |  |  | n |    |    |   || Untrusted   +-+ ePDG +-S2b---------------+   |  |  | e |    |    +---+| non-3GPP AN | +------+|    |             |   |  |  | t |    |    |   |+-------------+         |    |             |   |  |  | w |    |    |   +------------------------+    |             |   |  |  | o |    |    |                                 |             |   |  |  | r |    |    |   +------------------------+    |             |   |  |  | k |    |    +---+  Trusted non-3GPP AN   +-S2a--------------+   |  |  | s |    |    |   +------------------------+    |             |   |  |  |   |    |    |                                 |             +-+-+  |  |   |    |    +--------------------------S2c--------------------|    |  |   |    |    |                                 |                    |  |   |    +----+                                 +--------------------+  +---+     where E-UTRAN - Evolved Universal Terrestrial Radio Access Network           GERAN   - GSM EDGE Radio Access Network           HSS     - Home Subscriber Server           MME     - Mobility Management Entity           PCRF    - Policy and Charging Rule Function           SGSN    - Serving GPRS Support Node           UTRAN   - Universal Terrestrial Radio Access Network             Figure 5: EPS (Non-roaming) Architecture Overview   The GPRS Tunneling Protocol (GTP) [SDO-3GPP.29.060] [SDO-3GPP.29.281]   [SDO-3GPP.29.274] is a network-based mobility protocol specified for   3GPP networks (S2a, S2b, S5, and S8 interfaces).  In a similar way to   PMIPv6, it can handle mobility without requiring the involvement ofLiu, et al.                   Informational                    [Page 16]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   the mobile nodes.  In this case, the mobile node functionality is   provided in a proxy manner by the Serving Data Gateway (S-GW),   Evolved Packet Data Gateway (ePDG), or Trusted Wireless Access   Gateway (TWAG [SDO-3GPP.23.402]) .   3GPP specifications also include client-based mobility support, based   on adopting the use of Dual-Stack Mobile IPv6 (DSMIPv6) [RFC5555] for   the S2c interface [SDO-3GPP.24.303].  In this case, the User   Equipment (UE) implements the binding update functionality, while the   home agent role is played by the P-GW.   A Local IP Access (LIPA) and Selected IP Traffic Offload (SIPTO)   enabled network [SDO-3GPP.23.401] allows offloading some IP services   at the local access network above the Radio Access Network (RAN)   without the need to travel back to the P-GW (see Figure 6).      +---------+ IP traffic to mobile operator's CN      |  User   |....................................(Operator's CN)      | Equipm. |..................      +---------+                 . Local IP traffic                                  .                            +-----------+                            |Residential|                            |enterprise |                            |IP network |                            +-----------+                          Figure 6: LIPA Scenario   SIPTO enables an operator to offload certain types of traffic at a   network node close to the UE's point of attachment to the access   network.  This is done by selecting a set of GWs (S-GW and P-GW1 in   the figure below) that are geographically/topologically close to the   UE's point of attachment.                         SIPTO Traffic                              |                              .                              .                          +-------+        +------+                          | P-GW1 |   ---- | MME  |                          +-------+  /     +------+                               |    /    +------+     +-----+   +------+/       +-------+    |  UE  |.....| eNB |...| S-GW |........| P-GW2 |... CN Traffic    +------+     +-----+   +------+        +-------+                       Figure 7: SIPTO ArchitectureLiu, et al.                   Informational                    [Page 17]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   LIPA, on the other hand, enables an IP addressable UE connected via a   Home evolved Network B (HeNB) to access other IP addressable entities   in the same residential/enterprise IP network without traversing the   mobile operator's network core in the user plane.  In order to   achieve this, a Local GW (L-GW) collocated with the HeNB is used.  To   establish LIPA, the UE requests a new Public Data Network (PDN)   connection to an access point name for which LIPA is permitted, the   network selects the Local GW associated with the HeNB, and the   network enables a direct user-plane path between the Local GW and the   HeNB.    +------------+  +------+  +----------+  +-------------+    =====    |Residential |  | HeNB |  | Backhaul |  |Mobile       |   ( IP  )    |Enterprise  |..|------|..|          |..|Operator     |..(Network)    |Network     |  | L-GW |  |          |  |Core network |   =======    +------------+  +------+  +----------+  +-------------+                       /                       |                       /                   +-----+                   | UE  |                   +-----+                        Figure 8: LIPA Architecture   The 3GPP architecture specifications also provide mechanisms to allow   discovery and selection of gateways [SDO-3GPP.29.303].  These   mechanisms enable decisions that take into consideration topological   location and gateway collocation aspects, by relying upon the DNS as   a "location database."   Both SIPTO and LIPA have a very limited mobility support, especially   in 3GPP specifications up to Rel-12.  Briefly, LIPA mobility support   is limited to handovers between HeNBs that are managed by the same   L-GW (i.e., mobility within the local domain).  There is no guarantee   of IP session continuity for SIPTO.Liu, et al.                   Informational                    [Page 18]

RFC 7429             DMM Best Practices Gap Analysis        January 20155.  Gap Analysis   This section identifies the limitations in the current practices,   described inSection 4, with respect to the DMM requirements listed   in [RFC7333].5.1.  Distributed Mobility Management - REQ1   According to requirement REQ1 stated in [RFC7333], IP mobility,   network access, and forwarding solutions provided by DMM must make it   possible for traffic to avoid traversing a single mobility anchor far   from the optimal route.   From the analysis performed inSection 4, a DMM deployment can meet   the requirement "REQ1 Distributed mobility management" usually   relying on the following functions:   o  Multiple (distributed) anchoring: ability to anchor different      sessions of a single mobile node at different anchors.  In order      to provide improved routing, some anchors might need to be placed      closer to the mobile node or the corresponding node.   o  Dynamic anchor assignment/re-location: ability to i) assign the      initial anchor, and ii) dynamically change the initially assigned      anchor and/or assign a new one (this may also require the transfer      of mobility context between anchors).  This can be achieved either      by changing anchor for all ongoing sessions or by assigning new      anchors just for new sessions.   GAP1-1:  Both the main client- and network-based IP mobility            protocols (namely, MIPv6, DSMIPv6, and PMIPv6) allow            deploying multiple anchors (i.e., home agents and localized            mobility anchors), thereby providing the multiple anchoring            function.  However, existing solutions only provide an            initial anchor assignment, thus the lack of dynamic anchor            change/new anchor assignment is a gap.  Neither the HA            switch nor the LMA runtime assignment allows changing the            anchor during an ongoing session.  This actually comprises            several gaps: ability to perform anchor assignment at any            time (not only at the initial MN's attachment), ability of            the current anchor to initiate/trigger the relocation, and            ability to transfer registration context between anchors.   GAP1-2:  Dynamic anchor assignment may lead the MN to manage            different mobility sessions served by different mobility            anchors.  This is not an issue with client-based mobility            management, where the mobility client natively knows the            anchor associated with each of its mobility sessions.Liu, et al.                   Informational                    [Page 19]

RFC 7429             DMM Best Practices Gap Analysis        January 2015            However, there is one gap, as the MN should be capable of            handling IP addresses in a DMM-friendly way, meaning that            the MN can perform smart source address selection (i.e.,            deprecating IP addresses from previous mobility anchors so            they are not used for new sessions).  Besides, managing            different mobility sessions served by different mobility            anchors may raise issues with network-based mobility            management.  In this case, the mobile client located in the            network, e.g., MAG, usually retrieves the MN's anchor from            the MN's policy profile, as described inSection 6.2 of            [RFC5213].  Currently, the MN's policy profile implicitly            assumes a single serving anchor and thus does not maintain            the association between home network prefix and anchor.   GAP1-3:  The consequence of the distribution of the mobility anchors            is that there might be more than one available anchor for a            mobile node to use, which leads to an anchor discovery and            selection issue.  Currently, there is no efficient mechanism            specified to allow the dynamic discovery of the presence of            nodes that can play the anchor role, the discovery of their            capabilities, and the selection of the most suitable one.            There is also no mechanism to allow selecting a node that is            currently anchoring a given home address/prefix (capability            sometimes required to meet REQ#2).  However, there are some            mechanisms that could help to discover anchors, such as the            Dynamic Home Agent Address Discovery (DHAAD) [RFC6275], the            use of the home agent flag (H) in Router Advertisements            (which indicates that the router sending the Router            Advertisement is also functioning as a Mobile IPv6 home            agent on the link) or the MAP option in Router            Advertisements defined by HMIPv6.  Note that there are 3GPP            mechanisms providing that functionality defined in            [SDO-3GPP.29.303].   Regarding the ability to transfer registration context between   anchors, there are already some solutions that could be reused or   adapted to fill that gap, such as Fast Handovers for Mobile IPv6   [RFC5568] to enable traffic redirection from the old to the new   anchor, the Context Transfer Protocol [RFC4067] to enable the   required transfer of registration information between anchors, or the   Handover Keying architecture solutions [RFC6697] to speed up the re-   authentication process after a change of anchor.  Note that some   extensions might be needed in the context of DMM, as these protocols   were designed in the context of centralized client IP mobility   (focusing on the access reattachment and authentication).Liu, et al.                   Informational                    [Page 20]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   GAP1-4:  Also note that REQ1 is intended to prevent the data-plane            traffic from taking a suboptimal route.  Distributed            processing of the traffic may then be needed only in the            data plane.  Provision of this capability for distributed            processing should not conflict with the use of a centralized            control plane.  Other control-plane solutions (such as            charging, lawful interception, etc.) should not be            constrained by the DMM solution.  On the other hand,            combining the control-plane and data-plane FM function may            limit the choice of solutions to those that distribute both            data plane and control plane together.  In order to enable            distribution of only the data plane without distributing the            control plane, it would be necessary to split the forwarding            management function into the control-plane (FM-CP) and data-            plane (FM-DP) components; there is currently a gap here.5.2.  Bypassable Network-Layer Mobility Support for Each Application      Session - REQ2   The requirement REQ2 for "bypassable network-layer mobility support   for each application session" introduced in [RFC7333] requires   flexibility in determining whether network-layer mobility support is   needed.  This requirement enables one to choose whether or not to use   network-layer mobility support.  The following two functions are also   needed:   o  Dynamically assign/relocate anchor: A mobility anchor is assigned      only to sessions that use the network-layer mobility support.  The      MN may thus manage more than one session; some of them may be      associated with anchored IP address(es), while the others may be      associated with local IP address(es).   o  Multiple IP address management: This function is related to the      preceding item and is about the ability of the mobile node to      simultaneously use multiple IP addresses and select the best one      (from an anchoring point of view) to use on a per-      session/application/service basis.  This requires MN to acquire      information regarding the properties of the available IP      addresses.   GAP2-1:  The dynamic anchor assignment/relocation needs to ensure            that IP address continuity is guaranteed for sessions that            use such mobility support (e.g., in some scenarios, the            provision of mobility locally within a limited area might be            enough from the point of view of the mobile node or the            application) at the relocated anchor.  Implicitly, DMM may            release the needed resources when no applications are using            the network-layer mobility support.  DMM is then potentiallyLiu, et al.                   Informational                    [Page 21]

RFC 7429             DMM Best Practices Gap Analysis        January 2015            required to know which sessions at the mobile node are            active and are using the mobility support.  Typically, this            is known only by the MN (e.g., by its connection manager)            and would require some signaling support, such as socket API            extensions, from applications to indicate to the IP stack            whether or not mobility support is required.  This may imply            having the knowledge of which sessions at the mobile node            are active and are using the mobility support.  This is            something typically known only by the MN, e.g., by its            connection manager, and would also typically require some            signaling support, such as socket API extensions, from            applications to indicate to the IP stack whether mobility            support is required or not.  Therefore, (part of) this            knowledge might need to be transferred to/shared with the            network.   GAP2-2:  Management of multiple IP addresses provides the MN with the            choice to pick the correct address (e.g., from those            provided or not provided with mobility support) depending on            the application requirements.  When using client-based            mobility management, the MN is itself aware of the anchoring            capabilities of its assigned IP addresses.  This is not            necessarily the case with network-based IP mobility            management, as current mechanisms do not allow the MN to be            aware of the properties of its IP addresses.  For example,            the MN does not know whether or not the allocated IP            addresses are anchored.  However, there are proposals such            as [CLASS-PREFIX], [PREFIX-PROPERTIES], and [MULTI-ARCH],            where the network could indicate such properties during IP            address assignment procedures.  These proposals could be            considered as attempts to fix the gap.   GAP2-3:  The handling of mobility management to the granularity of an            individual session of a user/device needs proper session            identification in addition to user/device identification.5.3.  IPv6 Deployment - REQ3   This requirement states that DMM solutions should primarily target   IPv6 as the primary deployment environment.  IPv4 support is not   considered mandatory and solutions should not be tailored   specifically to support IPv4.   All analyzed DMM practices support IPv6.  Some of them, such as   MIPv6/NEMO (including the support of dynamic HA selection), MOBIKE,   and SIPTO also have IPv4 support.  Some solutions, e.g., PMIPv6, also   have some limited IPv4 support.  In conclusion, this requirement is   met by existing DMM practices.Liu, et al.                   Informational                    [Page 22]

RFC 7429             DMM Best Practices Gap Analysis        January 20155.4.  Considering Existing Mobility Protocols - REQ4   A DMM solution must first consider reusing and extending IETF-   standardized protocols before specifying new protocols.   As stated in [RFC7333], a DMM solution could reuse existing IETF and   standardized protocols before specifying new protocols.  Besides,Section 4 of this document discusses various ways to flatten and   distribute current mobility solutions.  Actually, nothing prevents   the distribution of mobility functions within IP mobility protocols.   However, as discussed in Sections5.1 and5.2, limitations exist.   The 3GPP data-plane anchoring function, i.e., the P-GW, can also be   distributed but with limitations such as no anchoring relocation and   no context transfer between anchors and the centralized control   plane.  The 3GPP architecture is also going in the direction of   flattening with SIPTO and LIPA, though they do not provide full   mobility support.  For example, mobility support for SIPTO traffic   can be rather limited, and offloaded traffic cannot access operator   services.  Thus, the operator must be very careful in selecting which   traffic to offload.5.5.  Coexistence with Deployed Networks/Hosts and Operability across      Different Networks - REQ5   According to [RFC7333], DMM implementations are required to coexist   with existing network deployments, end hosts, and routers.   Additionally, DMM solutions are expected to work across different   networks, possibly operated as separate administrative domains, when   the necessary mobility management signaling, forwarding, and network   access are allowed by the trust relationship between them.  All   current mobility protocols can coexist with existing network   deployments and end hosts.  There is no gap between existing mobility   protocols and this requirement.5.6.  Operation and Management Considerations - REQ6   This requirement actually comprises several aspects, as summarized   below.   o  A DMM solution needs to consider configuring a device, monitoring      the current operational state of a device, responding to events      that impact the device, possibly by modifying the configuration,      and storing the data in a format that can be analyzed later.   o  A DMM solution has to describe in what environment and how it can      be scalably deployed and managed.Liu, et al.                   Informational                    [Page 23]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   o  A DMM solution has to support mechanisms to test if the DMM      solution is working properly.   o  A DMM solution is expected to expose the operational state of DMM      to the administrators of the DMM entities.   o  A DMM solution, which supports flow mobility, is also expected to      support means to correlate the flow routing policies and the      observed forwarding actions.   o  A DMM solution is expected to support mechanisms to check the      liveness of the forwarding path.   o  A DMM solution has to provide fault management and monitoring      mechanisms to manage situations where update of the mobility      session or the data path fails.   o  A DMM solution is expected to be able to monitor the usage of the      DMM protocol.   o  DMM solutions have to support standardized configuration with      Network Configuration Protocol (NETCONF) [RFC6241] using YANG      [RFC6020] modules, which are expected to be created for DMM when      needed for such configuration.   GAP6-1:  Existing mobility management protocols have not thoroughly            documented how, or whether, they support the above list of            operation and management considerations.  Each of the above            needs to be considered from the beginning in a DMM solution.   GAP6-2:  Management Information Base (MIB) objects are currently            defined in [RFC4295] for MIPv6 and in [RFC6475] for PMIPv6.            Standardized configuration with NETCONF [RFC6241], using            YANG [RFC6020] modules, is lacking.5.7.  Security Considerations - REQ7   As stated in [RFC7333], a DMM solution has to support any security   protocols and mechanisms needed to secure the network and to make   continuous security improvements.  In addition, with security taken   into consideration early in the design, a DMM solution cannot   introduce new security risks or privacy concerns, or amplify existing   security risks that cannot be mitigated by existing security   protocols and mechanisms.   Any solutions that are intended to fill in gaps identified in this   document need to meet this requirement.  At present, it does not   appear that using existing solutions to support DMM has introducedLiu, et al.                   Informational                    [Page 24]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   any new security issues.  For example, Mobile IPv6 defines security   features to protect binding updates both to home agents and   correspondent nodes.  It also defines mechanisms to protect the data   packets transmission for Mobile IPv6 users.  Proxy Mobile IPv6 and   other variations of mobile IP also have similar security   considerations.5.8.  Multicast Considerations - REQ8   It is stated in [RFC7333] that DMM solutions are expected to allow   the development of multicast solutions to avoid network inefficiency   in multicast traffic delivery.   Current IP mobility solutions address mainly the mobility problem for   unicast traffic.  Solutions relying on the use of an anchor point for   tunneling multicast traffic down to the access router, or to the   mobile node, introduce the so-called "tunnel convergence problem".   This means that multiple instances of the same multicast traffic can   converge to the same node, diminishing the advantage of using   multicast protocols.   [RFC6224] documents a baseline solution for the previous issue, and   [RFC7028] documents a routing optimization solution.  The baseline   solution suggests deploying a Multicast Listener Discovery (MLD)   proxy function at the MAG and either a multicast router or another   MLD proxy function at the LMA.  The routing optimization solution   describes an architecture where a dedicated multicast tree mobility   anchor or a direct routing option can be used to avoid the tunnel   convergence problem.   Besides the solutions highlighted before, there are no other   mechanisms for mobility protocols to address the multicast tunnel   convergence problem.5.9.  Summary   We next list the main gaps identified from the analysis performed   above:   GAP1-1:  Existing solutions only provide an optimal initial anchor            assignment, a gap being the lack of dynamic anchor change/            new anchor assignment.  Neither the HA switch nor the LMA            runtime assignment allows changing the anchor during an            ongoing session.  MOBIKE allows change of GW, but its            applicability has been scoped to a very narrow use case.Liu, et al.                   Informational                    [Page 25]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   GAP1-2:  The MN needs to be able to perform source address selection.            A proper mechanism to inform the MN is lacking, so there is            not a basis for performing the correct selection.   GAP1-3:  Currently, there is no efficient mechanism specified by the            IETF that allows the dynamic discovery of the presence of            nodes that can play the role of anchor, discover their            capabilities, and allow the selection of the most suitable            one.  However, the following mechanisms could help            discovering anchors:            Dynamic Home Agent Address Discovery (DHAAD): The use of the            home agent flag (H) in Router Advertisements (which            indicates that the router sending the Router Advertisement            is also functioning as a Mobile IPv6 home agent on the link)            and the MAP option in Router Advertisements defined by            HMIPv6.   GAP1-4:  While existing network-based DMM practices may allow the            deployment of multiple LMAs and dynamically select the best            one, this requires to still keep some centralization in the            control plane to access the policy database (as defined inRFC 5213).  Although [RFC7389] allows a MAG to perform            splitting of its control and user planes, there is a lack of            solutions/extensions that support a clear control- and data-            plane separation for IETF IP mobility protocols in a DMM            context.   GAP2-1:  The information of which sessions at the mobile node are            active and are using the mobility support need to be            transferred to, or shared with, the network.  Such mechanism            has not been defined.   GAP2-2:  The mobile node needs to simultaneously use multiple IP            addresses with different properties.  There is a lack of            mechanism to expose this information to the mobile node,            which can then update accordingly its source address            selection mechanism.   GAP2-3:  The handling of mobility management has not been to the            granularity of an individual session of a user/device            before.  The combination of session identification and user/            device identification may be lacking.Liu, et al.                   Informational                    [Page 26]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   GAP6-1:  Mobility management protocols have not thoroughly documented            how, or whether, they support the following list of            operation and management considerations:            *  A DMM solution needs to consider configuring a device,               monitoring the current operational state of a device, and               responding to events that impact the device possibly by               modifying the configuration and storing the data in a               format that can be analyzed later.            *  A DMM solution has to describe in what environment, and               how, it can be scalably deployed and managed.            *  A DMM solution has to support mechanisms to test if the               DMM solution is working properly.            *  A DMM solution is expected to expose the operational               state of DMM to the administrators of the DMM entities.            *  A DMM solution, which supports flow mobility, is also               expected to support means to correlate the flow routing               policies and the observed forwarding actions.            *  A DMM solution is expected to support mechanisms to check               the liveness of the forwarding path.            *  A DMM solution has to provide fault management and               monitoring mechanisms to manage situations where update               of the mobility session or the data path fails.            *  A DMM solution is expected to be able to monitor the               usage of the DMM protocol.            *  DMM solutions have to support standardized configuration               with NETCONF [RFC6241], using YANG [RFC6020] modules,               which are expected to be created for DMM when needed for               such configuration.   GAP6-2:  Management Information Base (MIB) objects are currently            defined in [RFC4295] for MIPv6 and in [RFC6475] for PMIPv6.            Standardized configuration with NETCONF [RFC6241], using            YANG [RFC6020] modules, is lacking.Liu, et al.                   Informational                    [Page 27]

RFC 7429             DMM Best Practices Gap Analysis        January 20156.  Security Considerations   The deployment of DMM using existing IP mobility protocols raises   similar security threats as those encountered in centralized mobility   management systems.  Without authentication, a malicious node could   forge signaling messages and redirect traffic from its legitimate   path.  This would amount to a denial-of-service attack against the   specific node or nodes for which the traffic is intended.   Distributed mobility anchoring, while keeping current security   mechanisms, might require more security associations to be managed by   the mobility management entities, potentially leading to scalability   and performance issues.  Moreover, distributed mobility anchoring   makes mobility security problems more complex, since traffic   redirection requests might come from previously unconsidered origins,   thus leading to distributed points of attack.  Consequently, the DMM   security design needs to account for the distribution of security   associations between additional mobility entities and fulfill the   security requirement of [RFC7333].7.  References7.1.  Normative References   [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support              in IPv6",RFC 6275, July 2011,              <http://www.rfc-editor.org/info/rfc6275>.   [RFC7333]  Chan, H., Liu, D., Seite, P., Yokota, H., and J. Korhonen,              "Requirements for Distributed Mobility Management",RFC7333, August 2014,              <http://www.rfc-editor.org/info/rfc7333>.7.2.  Informative References   [CLASS-PREFIX]              Systems, C., Halwasia, G., Gundavelli, S., Deng, H.,              Thiebaut, L., Korhonen, J., and I. Farrer, "DHCPv6 class              based prefix", Work in Progress,draft-bhandari-dhc-class-based-prefix-05, July 2013.   [COMMUNITY-WIFI]              Gundavelli, S., Grayson, M., Seite, P., and Y. Lee,              "Service Provider Wi-Fi Services Over Residential              Architectures", Work in Progress,draft-gundavelli-v6ops-community-wifi-svcs-06, April 2013.Liu, et al.                   Informational                    [Page 28]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   [IEEE.802-16.2009]              IEEE, "IEEE Standard for Local and metropolitan area              networks Part 16: Air Interface for Broadband Wireless              Access Systems", IEEE Standard 802.16, 2009,              <http://standards.ieee.org/getieee802/download/802.16-2009.pdf>.   [MULTI-ARCH]              Anipko, D., Ed., "Multiple Provisioning Domain              Architecture", Work in Progress,draft-ietf-mif-mpvd-arch-08, January 2015.   [PREFIX-PROPERTIES]              Korhonen, J., Patil, B., Gundavelli, S., Seite, P., and D.              Liu, "IPv6 Prefix Properties", Work in Progress,draft-korhonen-6man-prefix-properties-02, July 2013.   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.              Thubert, "Network Mobility (NEMO) Basic Support Protocol",RFC 3963, January 2005,              <http://www.rfc-editor.org/info/rfc3963>.   [RFC4066]  Liebsch, M., Singh, A., Chaskar, H., Funato, D., and E.              Shim, "Candidate Access Router Discovery (CARD)",RFC4066, July 2005, <http://www.rfc-editor.org/info/rfc4066>.   [RFC4067]  Loughney, J., Nakhjiri, M., Perkins, C., and R. Koodli,              "Context Transfer Protocol (CXTP)",RFC 4067, July 2005,              <http://www.rfc-editor.org/info/rfc4067>.   [RFC4225]  Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.              Nordmark, "Mobile IP Version 6 Route Optimization Security              Design Background",RFC 4225, December 2005,              <http://www.rfc-editor.org/info/rfc4225>.   [RFC4295]  Keeni, G., Koide, K., Nagami, K., and S. Gundavelli,              "Mobile IPv6 Management Information Base",RFC 4295, April              2006, <http://www.rfc-editor.org/info/rfc4295>.   [RFC4555]  Eronen, P., "IKEv2 Mobility and Multihoming Protocol              (MOBIKE)",RFC 4555, June 2006,              <http://www.rfc-editor.org/info/rfc4555>.   [RFC4640]  Patel, A. and G. Giaretta, "Problem Statement for              bootstrapping Mobile IPv6 (MIPv6)",RFC 4640, September              2006, <http://www.rfc-editor.org/info/rfc4640>.Liu, et al.                   Informational                    [Page 29]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   [RFC4889]  Ng, C., Zhao, F., Watari, M., and P. Thubert, "Network              Mobility Route Optimization Solution Space Analysis",RFC4889, July 2007, <http://www.rfc-editor.org/info/rfc4889>.   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol",RFC4960, September 2007,              <http://www.rfc-editor.org/info/rfc4960>.   [RFC5014]  Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6              Socket API for Source Address Selection",RFC 5014,              September 2007, <http://www.rfc-editor.org/info/rfc5014>.   [RFC5026]  Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6              Bootstrapping in Split Scenario",RFC 5026, October 2007,              <http://www.rfc-editor.org/info/rfc5026>.   [RFC5142]  Haley, B., Devarapalli, V., Deng, H., and J. Kempf,              "Mobility Header Home Agent Switch Message",RFC 5142,              January 2008, <http://www.rfc-editor.org/info/rfc5142>.   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,              and B. Patil, "Proxy Mobile IPv6",RFC 5213, August 2008,              <http://www.rfc-editor.org/info/rfc5213>.   [RFC5380]  Soliman, H., Castelluccia, C., ElMalki, K., and L.              Bellier, "Hierarchical Mobile IPv6 (HMIPv6) Mobility              Management",RFC 5380, October 2008,              <http://www.rfc-editor.org/info/rfc5380>.   [RFC5555]  Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and              Routers",RFC 5555, June 2009,              <http://www.rfc-editor.org/info/rfc5555>.   [RFC5568]  Koodli, R., "Mobile IPv6 Fast Handovers",RFC 5568, July              2009, <http://www.rfc-editor.org/info/rfc5568>.   [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy              Mobile IPv6",RFC 5844, May 2010,              <http://www.rfc-editor.org/info/rfc5844>.   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the              Network Configuration Protocol (NETCONF)",RFC 6020,              October 2010, <http://www.rfc-editor.org/info/rfc6020>.   [RFC6097]  Korhonen, J. and V. Devarapalli, "Local Mobility Anchor              (LMA) Discovery for Proxy Mobile IPv6",RFC 6097, February              2011, <http://www.rfc-editor.org/info/rfc6097>.Liu, et al.                   Informational                    [Page 30]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   [RFC6224]  Schmidt, T., Waehlisch, M., and S. Krishnan, "Base              Deployment for Multicast Listener Support in Proxy Mobile              IPv6 (PMIPv6) Domains",RFC 6224, April 2011,              <http://www.rfc-editor.org/info/rfc6224>.   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.              Bierman, "Network Configuration Protocol (NETCONF)",RFC6241, June 2011, <http://www.rfc-editor.org/info/rfc6241>.   [RFC6463]  Korhonen, J., Gundavelli, S., Yokota, H., and X. Cui,              "Runtime Local Mobility Anchor (LMA) Assignment Support              for Proxy Mobile IPv6",RFC 6463, February 2012,              <http://www.rfc-editor.org/info/rfc6463>.   [RFC6475]  Keeni, G., Koide, K., Gundavelli, S., and R. Wakikawa,              "Proxy Mobile IPv6 Management Information Base",RFC 6475,              May 2012, <http://www.rfc-editor.org/info/rfc6475>.   [RFC6611]  Chowdhury, K. and A. Yegin, "Mobile IPv6 (MIPv6)              Bootstrapping for the Integrated Scenario",RFC 6611, May              2012, <http://www.rfc-editor.org/info/rfc6611>.   [RFC6697]  Zorn, G., Wu, Q., Taylor, T., Nir, Y., Hoeper, K., and S.              Decugis, "Handover Keying (HOKEY) Architecture Design",RFC 6697, July 2012,              <http://www.rfc-editor.org/info/rfc6697>.   [RFC6705]  Krishnan, S., Koodli, R., Loureiro, P., Wu, Q., and A.              Dutta, "Localized Routing for Proxy Mobile IPv6",RFC6705, September 2012,              <http://www.rfc-editor.org/info/rfc6705>.   [RFC6724]  Thaler, D., Draves, R., Matsumoto, A., and T. Chown,              "Default Address Selection for Internet Protocol Version 6              (IPv6)",RFC 6724, September 2012,              <http://www.rfc-editor.org/info/rfc6724>.   [RFC7028]  Zuniga, JC., Contreras, LM., Bernardos, CJ., Jeon, S., and              Y. Kim, "Multicast Mobility Routing Optimizations for              Proxy Mobile IPv6",RFC 7028, September 2013,              <http://www.rfc-editor.org/info/rfc7028>.   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.              Kivinen, "Internet Key Exchange Protocol Version 2              (IKEv2)",RFC 7296, October 2014,              <http://www.rfc-editor.org/info/rfc7296>.Liu, et al.                   Informational                    [Page 31]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   [RFC7389]  Wakikawa, R., Pazhyannur, R., Gundavelli, S., and C.              Perkins, "Separation of Control and User Plane for Proxy              Mobile IPv6",RFC 7389, October 2014,              <http://www.rfc-editor.org/info/rfc7389>.   [SDO-3GPP.23.401]              3GPP, "General Packet Radio Service (GPRS) enhancements              for Evolved Universal Terrestrial Radio Access Network              (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013.   [SDO-3GPP.23.402]              3GPP, "Architecture enhancements for non-3GPP accesses",              3GPP TS 23.402 10.8.0, September 2012.   [SDO-3GPP.24.303]              3GPP, "Mobility management based on Dual-Stack Mobile              IPv6; Stage 3", 3GPP TS 24.303 10.0.0, June 2013.   [SDO-3GPP.29.060]              3GPP, "General Packet Radio Service (GPRS); GPRS              Tunnelling Protocol (GTP) across the Gn and Gp interface",              3GPP TS 29.060 3.19.0, March 2004.   [SDO-3GPP.29.274]              3GPP, "3GPP Evolved Packet System (EPS); Evolved General              Packet Radio Service (GPRS) Tunnelling Protocol for              Control plane (GTPv2-C); Stage 3", 3GPP TS 29.274 10.11.0,              June 2013.   [SDO-3GPP.29.281]              3GPP, "General Packet Radio System (GPRS) Tunnelling              Protocol User Plane (GTPv1-U)", 3GPP TS 29.281 10.3.0,              September 2011.   [SDO-3GPP.29.303]              3GPP, "Domain Name System Procedures; Stage 3", 3GPP TS              29.303 10.4.0, September 2012.Liu, et al.                   Informational                    [Page 32]

RFC 7429             DMM Best Practices Gap Analysis        January 2015Contributors   This document has benefited due to valuable contributions from   Charles E. Perkins   Huawei Technologies   EMail: charliep@computer.org   who produced a matrix to compare the different mobility protocols and   extensions against a list of desired DMM properties.  They were   useful inputs in the early work of gap analysis.  He continued to   give suggestions as well as extensively review comments for this   document.Authors' Addresses   Dapeng Liu (editor)   China Mobile   Unit 2, 28 Xuanwumenxi Ave, Xuanwu District   Beijing  100053   China   EMail: liudapeng@chinamobile.com   Juan Carlos Zuniga (editor)   InterDigital Communications, LLC   1000 Sherbrooke Street West, 10th floor   Montreal, Quebec  H3A 3G4   Canada   EMail: JuanCarlos.Zuniga@InterDigital.com   URI:http://www.InterDigital.com/   Pierrick Seite   Orange   4, rue du Clos Courtel, BP 91226   Cesson-Sevigne  35512   France   EMail: pierrick.seite@orange.comLiu, et al.                   Informational                    [Page 33]

RFC 7429             DMM Best Practices Gap Analysis        January 2015   H Anthony Chan   Huawei Technologies   5340 Legacy Dr. Building 3   Plano, TX  75024   United States   EMail: h.a.chan@ieee.org   Carlos J. Bernardos   Universidad Carlos III de Madrid   Av. Universidad, 30   Leganes, Madrid  28911   Spain   Phone: +34 91624 6236   EMail: cjbc@it.uc3m.es   URI:http://www.it.uc3m.es/cjbc/Liu, et al.                   Informational                    [Page 34]

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