DMM Working Group CJ. Bernardos Internet-Draft A. de la Oliva Intended status: Experimental UC3M Expires: September 9, 2020 F. Giust Athonet JC. Zuniga SIGFOX A. Mourad InterDigital March 8, 2020 Proxy Mobile IPv6 extensions for Distributed Mobility Management draft-ietf-dmm-pmipv6-dlif-06 Abstract Distributed Mobility Management solutions allow for setting up networks so that traffic is distributed in an optimal way and does not rely on centrally deployed anchors to provide IP mobility support. There are many different approaches to address Distributed Mobility Management, as for example extending network-based mobility protocols (like Proxy Mobile IPv6), or client-based mobility protocols (like Mobile IPv6), among others. This document follows the former approach and proposes a solution based on Proxy Mobile IPv6 in which mobility sessions are anchored at the last IP hop router (called mobility anchor and access router). The mobility anchor and access router is an enhanced access router which is also able to operate as a local mobility anchor or mobility access gateway, on a per prefix basis. The document focuses on the required extensions to effectively support simultaneously anchoring several flows at different distributed gateways. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Bernardos, et al. Expires September 9, 2020 [Page 1] Internet-Draft PMIPv6 DMM and DLIF March 2020 Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on September 9, 2020. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://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 Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. PMIPv6 DMM extensions . . . . . . . . . . . . . . . . . . . . 6 3.1. Initial registration . . . . . . . . . . . . . . . . . . 7 3.2. The CMD as PBU/PBA relay . . . . . . . . . . . . . . . . 8 3.3. The CMD as MAAR locator . . . . . . . . . . . . . . . . . 11 3.4. The CMD as MAAR proxy . . . . . . . . . . . . . . . . . . 12 3.5. De-registration . . . . . . . . . . . . . . . . . . . . . 13 3.6. Retransmissions and Rate Limiting . . . . . . . . . . . . 14 3.7. The Distributed Logical Interface (DLIF) concept . . . . 14 4. Message Format . . . . . . . . . . . . . . . . . . . . . . . 18 4.1. Proxy Binding Update . . . . . . . . . . . . . . . . . . 18 4.2. Proxy Binding Acknowledgment . . . . . . . . . . . . . . 19 4.3. Anchored Prefix Option . . . . . . . . . . . . . . . . . 19 4.4. Local Prefix Option . . . . . . . . . . . . . . . . . . . 21 4.5. Previous MAAR Option . . . . . . . . . . . . . . . . . . 22 4.6. Serving MAAR Option . . . . . . . . . . . . . . . . . . . 23 4.7. DLIF Link-local Address Option . . . . . . . . . . . . . 24 4.8. DLIF Link-layer Address Option . . . . . . . . . . . . . 25 Bernardos, et al. Expires September 9, 2020 [Page 2] Internet-Draft PMIPv6 DMM and DLIF March 2020 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 6. Security Considerations . . . . . . . . . . . . . . . . . . . 26 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.1. Normative References . . . . . . . . . . . . . . . . . . 27 8.2. Informative References . . . . . . . . . . . . . . . . . 28 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 1. Introduction The Distributed Mobility Management (DMM) paradigm aims at minimizing the impact of currently standardized mobility management solutions which are centralized (at least to a considerable extent) [RFC7333]. Current IP mobility solutions, standardized with the names of Mobile IPv6 [RFC6275], or Proxy Mobile IPv6 (PMIPv6) [RFC5213], just to cite the two most relevant examples, offer mobility support at the cost of handling operations at a cardinal point, the mobility anchor (i.e., the home agent for Mobile IPv6, and the local mobility anchor for Proxy Mobile IPv6), and burdening it with data forwarding and control mechanisms for a great amount of users. As stated in [RFC7333], centralized mobility solutions are prone to several problems and limitations: longer (sub-optimal) routing paths, scalability problems, signaling overhead (and most likely a longer associated handover latency), more complex network deployment, higher vulnerability due to the existence of a potential single point of failure, and lack of granularity of the mobility management service (i.e., mobility is offered on a per-node basis, not being possible to define finer granularity policies, as for example per-application). The purpose of Distributed Mobility Management is to overcome the limitations of the traditional centralized mobility management [RFC7333] [RFC7429]; the main concept behind DMM solutions is indeed bringing the mobility anchor closer to the Mobile Node (MN). Following this idea, the central anchor is moved to the edge of the network, being deployed in the default gateway of the mobile node. That is, the first elements that provide IP connectivity to a set of MNs are also the mobility managers for those MNs. In this document, we call these entities Mobility Anchors and Access Routers (MAARs). This document focuses on network-based DMM, hence the starting point is making PMIPv6 work in a distributed manner [RFC7429]. Mobility is handled by the network without the MNs involvement, but, differently from PMIPv6, when the MN moves from one access network to another, it may also change anchor router, hence requiring signaling between the anchors to retrieve the MN's previous location(s). Also, a key- aspect of network-based DMM, is that a prefix pool belongs exclusively to each MAAR, in the sense that those prefixes are Bernardos, et al. Expires September 9, 2020 [Page 3] Internet-Draft PMIPv6 DMM and DLIF March 2020 assigned by the MAAR to the MNs attached to it, and they are routable at that MAAR. Prefixes are assigned to MNs attached a MAAR at that time, but remain with those MNs as mobility occurs, remaining always routable at that MAAR as well as towards the MN itself. We consider partially distributed schemes, where only the data plane is distributed among access routers similar to MAGs, whereas the control plane is kept centralized towards a cardinal node used as information store, but relieved from any route management and MN's data forwarding task. 2. Terminology The following terms used in this document are defined in the Proxy Mobile IPv6 specification [RFC5213]: Local Mobility Anchor (LMA) Mobile Access Gateway (MAG) Mobile Node (MN) Binding Cache Entry (BCE) Proxy Care-of Address (P-CoA) Proxy Binding Update (PBU) Proxy Binding Acknowledgement (PBA) The following terms are used in this document: Home Control-Plane Anchor (Home-CPA or H-CPA): The Home-CPA function hosts the mobile node (MN)'s mobility session. There can be more than one mobility session for a mobile node and those sessions may be anchored on the same or different Home-CPA's. The home-CPA will interface with the home-DPA for managing the forwarding state. Home Data Plane Anchor (Home-DPA or H-DPA): The Home-DPA is the topological anchor for the MN's IP address/ prefix(es). The Home- DPA is chosen by the Home-CPA on a session- basis. The Home-DPA is in the forwarding path for all the mobile node's IP traffic. Bernardos, et al. Expires September 9, 2020 [Page 4] Internet-Draft PMIPv6 DMM and DLIF March 2020 Access Control Plane Node (Access-CPN or A-CPN): The Access-CPN is responsible for interfacing with the mobile node's Home-CPA and with the Access-DPN. The Access-CPN has a protocol interface to the Home-CPA. Access Data Plane Node (Access-DPN or A-DPN): The Access-DPN function is hosted on the first-hop router where the mobile node is attached. This function is not hosted on a layer-2 bridging device such as a eNode(B) or Access Point. The following terms are defined and used in this document: MAAR (Mobility Anchor and Access Router). First hop router where the mobile nodes attach to. It also plays the role of mobility manager for the IPv6 prefixes it anchors, running the functionalities of PMIP's MAG and LMA. Depending on the prefix, it plays the role of Access-DPN, Home-DPA and Access-CPN. CMD (Central Mobility Database). The node that stores the BCEs allocated for the MNs in the mobility domain. It plays the role of Home-CPA. P-MAAR (Previous MAAR). When a MN moves to a new point of attachment a new MAAR might be allocated as its anchor point for future IPv6 prefixes. The MAAR that served the MN prior to new attachment becomes the P-MAAR. It is still the anchor point for the IPv6 prefixes it had allocated to the MN in the past and serves as the Home-DPA for flows using these prefixes. There might be several P-MAARs serving a MN when the MN is frequently switching points of attachment while maintaining long-lasting flows. S-MAAR (Serving MAAR). The MAAR which the MN is currently attached to. Depending on the prefix, it plays the role of Access-DPN, Home-DPA and Access-CPN. Anchoring MAAR. A MAAR anchoring an IPv6 prefix used by an MN. DLIF (Distributed Logical Interface). It is a logical interface at the IP stack of the MAAR. For each active prefix used by the MN, the S-MAAR has a DLIF configured (associated to each MAAR still anchoring flows). In this way, an S-MAAR exposes itself towards each MN as multiple routers, one as itself and one per P-MAAR. Bernardos, et al. Expires September 9, 2020 [Page 5] Internet-Draft PMIPv6 DMM and DLIF March 2020 3. PMIPv6 DMM extensions The solution consists of de-coupling the entities that participate in the data and the control planes: the data plane becomes distributed and managed by the MAARs near the edge of the network, while the control plane, besides those on the MAARs, relies on a central entity called Central Mobility Database (CMD). In the proposed architecture, the hierarchy present in PMIPv6 between LMA and MAG is preserved, but with the following substantial variations: o The LMA is relieved from the data forwarding role, only the Binding Cache and its management operations are maintained. Hence the LMA is renamed into CMD, which is therefore a Home-CPA. Also, the CMD is able to send and parse both PBU and PBA messages. o The MAG is enriched with the LMA functionalities, hence the name Mobility Anchor and Access Router (MAAR). It maintains a local Binding Cache for the MNs that are attached to it and it is able to send and parse PBU and PBA messages. o The binding cache will be extended to include information regarding P-MAARs where the mobile node was anchored and still retains active data sessions. o Each MAAR has a unique set of global prefixes (which are configurable), that can be allocated by the MAAR to the MNs, but must be exclusive to that MAAR, i.e. no other MAAR can allocate the same prefixes. The MAARs leverage the CMD to access and update information related to the MNs, stored as mobility sessions; hence, a centralized node maintains a global view of the network status. The CMD is queried whenever a MN is detected to join/leave the mobility domain. It might be a fresh attachment, a detachment or a handover, but as MAARs are not aware of past information related to a mobility session, they contact the CMD to retrieve the data of interest and eventually take the appropriate action. The procedure adopted for the query and the message exchange sequence might vary to optimize the update latency and/or the signaling overhead. Here is presented one method for the initial registration, and three different approaches for updating the mobility sessions using PBUs and PBAs. Each approach assigns a different role to the CMD: o The CMD is a PBU/PBA relay; o The CMD is only a MAAR locator; o The CMD is a PBU/PBA proxy. Bernardos, et al. Expires September 9, 2020 [Page 6] Internet-Draft PMIPv6 DMM and DLIF March 2020 The solution described in this document allows performing per-prefix anchoring decisions, to support e.g., some flows to be anchored at a central Home-DPA (like a traditional LMA) or to enable an application to switch to the locally anchored prefix to gain route optimization, as indicated in [RFC8563]. This type of per-prefix treatment would potentially require additional extensions to the MAARs and signaling between the MAARs and the MNs to convey the per-flow anchor preference (central, distributed), which are not covered in this document. Note that a MN may move across different MAARs, which might result in several P-MAARs existing at a given moment of time, each of them anchoring a different prefix used by the MN. 3.1. Initial registration Initial registration is performed when an MN attaches to a network for the first time (rather than attaching to a new network after moving from a previous one). In this description (shown in Figure 1), it is assumed that: 1. The MN is attaching to MAAR1. 2. The MN is authorized to attach to the network. Upon MN attachment, the following operations take place: 1. MAAR1 assigns a global IPv6 prefix from its own prefix pool to the MN (Pref1). It also stores this prefix (Pref1) in the locally allocated temporary Binding Cache Entry (BCE). 2. MAAR1 sends a PBU [RFC5213] with Pref1 and the MN's MN-ID to the CMD. 3. Since this is an initial registration, the CMD stores a BCE containing as primary fields the MN-ID, Pref1 and MAAR1's address as a Proxy-CoA. 4. The CMD replies with a PBA with the usual options defined in PMIPv6 [RFC5213], meaning that the MN's registration is fresh and no past status is available. 5. MAAR1 stores the BCE described in (1) and unicasts a Router Advertisement (RA) to the MN with Pref1. 6. The MN uses Pref1 to configure an IPv6 address (IP1) (e.g., with stateless auto-configuration, SLAAC). Bernardos, et al. Expires September 9, 2020 [Page 7] Internet-Draft PMIPv6 DMM and DLIF March 2020 Note that: 1. Alternative IPv6 auto-configuration mechanisms can also be used, though this document describes the SLAAC-based one. 2. IP1 is routable at MAAR1, in the sense that it is on the path of packets addressed to the MN. 3. MAAR1 acts as a plain router for packets destined to the MN, as no encapsulation nor special handling takes place. In the diagram shown in Figure 1 (and subsequent diagrams), the flow of packets is presented using '*'. +-----+ +---+ +--+ |MAAR1| |CMD| |CN| +-----+ +---+ +*-+ | | * MN | * +---+ attach. | ***** _|CMD|_ detection | flow1 * / +-+-+ \ | | * / | \ local BCE | * / | \ allocation | * / | \ |--- PBU -->| +---*-+-' +--+--+ `+-----+ | BCE | * | | | | | | creation |MAAR1+------+MAAR2+-----+MAAR3| |<-- PBA ---| | * | | | | | local BCE | +---*-+ +-----+ +-----+ finalized | * | | Pref1 * | | +*-+ | | |MN| | | +--+ Operations sequence Packets flow Figure 1: First attachment to the network Note that the registration process does not change regardless of the CMD's modes (relay, locator or proxy) described next. The procedure is depicted in Figure 1. 3.2. The CMD as PBU/PBA relay Upon MN mobility, if the CMD behaves as PBU/PBA relay, the following operations take place: Bernardos, et al. Expires September 9, 2020 [Page 8] Internet-Draft PMIPv6 DMM and DLIF March 2020 1. When the MN moves from its current point of attachment and attaches to MAAR2 (now the S-MAAR), MAAR2 reserves an IPv6 prefix (Pref2), it stores a temporary BCE, and it sends a PBU to the CMD for registration. 2. Upon PBU reception and BC lookup, the CMD retrieves an already existing entry for the MN, binding the MN-ID to its former location; thus, the CMD forwards the PBU to the MAAR indicated as Proxy CoA (MAAR1), including a new mobility option to communicate the S-MAAR's global address to MAAR1, defined as Serving MAAR Option in Section 4.6. The CMD updates the P-CoA field in the BCE related to the MN with the S-MAAR's address. 3. Upon PBU reception, MAAR1 can install a tunnel on its side towards MAAR2 and the related routes for Pref1. Then MAAR1 replies to the CMD with a PBA (including the option mentioned before) to ensure that the new location has successfully changed, containing the prefix anchored at MAAR1 in the Home Network Prefix option. 4. The CMD, after receiving the PBA, updates the BCE populating an instance of the P-MAAR list. The P-MAAR list is an additional field on the BCE that contains an element for each P-MAAR involved in the MN's mobility session. The list element contains the P-MAAR's global address and the prefix it has delegated. Also, the CMD sends a PBA to the new S-MAAR, containing the previous Proxy-CoA and the prefix anchored to it embedded into a new mobility option called Previous MAAR Option (defined in Section 4.5), so that, upon PBA arrival, a bi-directional tunnel can be established between the two MAARs and new routes are set appropriately to recover the IP flow(s) carrying Pref1. 5. Now packets destined to Pref1 are first received by MAAR1, encapsulated into the tunnel and forwarded to MAAR2, which finally delivers them to their destination. In uplink, when the MN transmits packets using Pref1 as source address, they are sent to MAAR2, as it is MN's new default gateway, then tunneled to MAAR1 which routes them towards the next hop to destination. Conversely, packets carrying Pref2 are routed by MAAR2 without any special packet handling both for uplink and downlink. Bernardos, et al. Expires September 9, 2020 [Page 9] Internet-Draft PMIPv6 DMM and DLIF March 2020 +-----+ +---+ +-----+ +--+ +--+ |MAAR1| |CMD| |MAAR2| |CN| |CN| +-----+ +---+ +-----+ +*-+ +*-+ | | | * * | | MN * +---+ * | | attach. ***** _|CMD|_ * | | det. flow1 * / +-+-+ \ *flow2 | |<-- PBU ---| * / | \ * | BCE | * / | ******* | check+ | * / | * \ | update | +---*-+-' +--+-*+ `+-----+ |<-- PBU*---| | | * | | *| | | route | | |MAAR1|______|MAAR2+-----+MAAR3| update | | | **(______)** *| | | |--- PBA*-->| | +-----+ +-*--*+ +-----+ | BCE | * * | update | Pref1 * *Pref2 | |--- PBA*-->| +*--*+ | | route ---move-->|*MN*| | | update +----+ Operations sequence Data Packets flow PBU/PBA Messages with * contain a new mobility option Figure 2: Scenario after a handover, CMD as relay For MN's next movements the process is repeated except the number of P-MAARs involved increases (accordingly to the number of prefixes that the MN wishes to maintain). Indeed, once the CMD receives the first PBU from the new S-MAAR, it forwards copies of the PBU to all the P-MAARs indicated in the BCE, namely the one registered as current P-CoA (i.e., the MAAR prior to handover) plus the ones in the P-MAARs list. They reply with a PBA to the CMD, which aggregates them into a single one to notify the S-MAAR, that finally can establish the tunnels with the P-MAARs. It should be noted that this design separates the mobility management at the prefix granularity, and it can be tuned in order to erase old mobility sessions when not required, while the MN is reachable through the latest prefix acquired. Moreover, the latency associated to the mobility update is bound to the PBA sent by the furthest P-MAAR, in terms of RTT, that takes the longest time to reach the CMD. The drawback can be mitigated introducing a timeout at the CMD, by which, after its expiration, all the PBAs so far collected are transmitted, and the remaining are sent later upon their arrival. Note that in this case the S-MAAR might receive multiple PBAs from the CMD in response to a PBU. The CMD SHOULD follow the Bernardos, et al. Expires September 9, 2020 [Page 10] Internet-Draft PMIPv6 DMM and DLIF March 2020 retransmissions and rate limiting considerations described in Section 3.6, especially when aggregating and relaying PBAs. When there are multiple previous MAARs, e.g., k MAARs, a single PBU received by the CMD triggers k outgoing packets from a single incoming packet. This may lead to packet bursts originated from the CMD, albeit to different targets. Pacing mechanisms MUST be introduced to avoid bursts on the outgoing link. 3.3. The CMD as MAAR locator The handover latency experienced in the approach shown before can be reduced if the P-MAARs are allowed to signal directly their information to the new S-MAAR. This procedure reflects what was described in Section 3.2 up to the moment the P-MAAR receives the PBU with the S-MAAR option. At that point a P-MAAR is aware of the new MN's location (because of the S-MAAR's address in the S-MAAR option), and, besides sending a PBA to the CMD, it also sends a PBA to the S-MAAR including the prefix it is anchoring. This latter PBA does not need to include new options, as the prefix is embedded in the HNP option and the P-MAAR's address is taken from the message's source address. The CMD is relieved from forwarding the PBA to the S-MAAR, as the latter receives a copy directly from the P-MAAR with the necessary information to build the tunnels and set the appropriate routes. Figure 3 illustrates the new message sequence, while the data forwarding is unaltered. Bernardos, et al. Expires September 9, 2020 [Page 11] Internet-Draft PMIPv6 DMM and DLIF March 2020 +-----+ +---+ +-----+ +--+ +--+ |MAAR1| |CMD| |MAAR2| |CN| |CN| +-----+ +---+ +-----+ +*-+ +*-+ | | | * * | | MN * +---+ * | | attach. ***** _|CMD|_ * | | det. flow1 * / +-+-+ \ *flow2 | |<-- PBU ---| * / | \ * | BCE | * / | ******* | check+ | * / | * \ | update | +---*-+-' +--+-*+ `+-----+ |<-- PBU*---| | | * | | *| | | route | | |MAAR1|______|MAAR2+-----+MAAR3| update | | | **(______)** *| | | |--------- PBA -------->| +-----+ +-*--*+ +-----+ |--- PBA*-->| route * * | BCE update Pref1 * *Pref2 | update | +*--*+ | | | ---move-->|*MN*| | | | +----+ Operations sequence Data Packets flow PBU/PBA Messages with * contain a new mobility option Figure 3: Scenario after a handover, CMD as locator 3.4. The CMD as MAAR proxy A further enhancement of previous solutions can be achieved when the CMD sends the PBA to the new S-MAAR before notifying the P-MAARs of the location change. Indeed, when the CMD receives the PBU for the new registration, it is already in possession of all the information that the new S-MAAR requires to set up the tunnels and the routes. Thus the PBA is sent to the S-MAAR immediately after a PBU is received, including also in this case the P-MAAR option. In parallel, a PBU is sent by the CMD to the P-MAARs containing the S-MAAR option, to notify them about the new MN's location, so they receive the information to establish the tunnels and routes on their side. When P-MAARs complete the update, they send a PBA to the CMD to indicate that the operation is concluded and the information is updated in all network nodes. This procedure is obtained from the first one re-arranging the order of the messages, but the parameters communicated are the same. This scheme is depicted in Figure 4, where, again, the data forwarding is kept untouched. Bernardos, et al. Expires September 9, 2020 [Page 12] Internet-Draft PMIPv6 DMM and DLIF March 2020 +-----+ +---+ +-----+ +--+ +--+ |MAAR1| |CMD| |MAAR2| |CN| |CN| +-----+ +---+ +-----+ +*-+ +*-+ | | | * * | | MN * +---+ * | | attach. ***** _|CMD|_ * | | det. flow1 * / +-+-+ \ *flow2 | |<-- PBU ---| * / | \ * | BCE | * / | ******* | check+ | * / | * \ | update | +---*-+-' +--+-*+ `+-----+ |<-- PBU*---x--- PBA*-->| | * | | *| | | route | route |MAAR1|______|MAAR2+-----+MAAR3| update | update | **(______)** *| | | |--- PBA*-->| | +-----+ +-*--*+ +-----+ | BCE | * * | update | Pref1 * *Pref2 | | | +*--*+ | | | ---move-->|*MN*| | | | +----+ Operations sequence Data Packets flow PBU/PBA Messages with * contain a new mobility option Figure 4: Scenario after a handover, CMD as proxy 3.5. De-registration The de-registration mechanism devised for PMIPv6 cannot be used as-is in this solution. The reason for this is that each MAAR handles an independent mobility session (i.e., a single or a set of prefixes) for a given MN, whereas the aggregated session is stored at the CMD. Indeed, if a previous MAAR initiates a de-registration procedure, because the MN is no longer present on the MAAR's access link, it removes the routing state for that (those) prefix(es), that would be deleted by the CMD as well, hence defeating any prefix continuity attempt. The simplest approach to overcome this limitation is to deny a P-MAAR to de-register a prefix, that is, allowing only a serving MAAR to de-register the whole MN session. This can be achieved by first removing any layer-2 detachment event, so that de- registration is triggered only when the binding lifetime expires, hence providing a guard interval for the MN to connect to a new MAAR. Then, a change in the MAAR operations is required, and at this stage two possible solutions can be deployed: o A previous MAAR stops the BCE timer upon receiving a PBU from the CMD containing a "Serving MAAR" option. In this way only the Bernardos, et al. Expires September 9, 2020 [Page 13] Internet-Draft PMIPv6 DMM and DLIF March 2020 Serving MAAR is allowed to de-register the mobility session, arguing that the MN definitely left the domain. o Previous MAARs can, upon BCE expiry, send de-registration messages to the CMD, which, instead of acknowledging the message with a 0 lifetime, sends back a PBA with a non-zero lifetime, hence re- newing the session, if the MN is still connected to the domain. 3.6. Retransmissions and Rate Limiting When sending PBUs, the node sending them (the CMD or S-MAAR) SHOULD make use of the timeout also to deal with missing PBAs (to retransmit PBUs). The INITIAL_BINDACK_TIMEOUT [RFC6275] SHOULD be used for configuring the retransmission timer. The retransmissions by the node MUST use an exponential backoff process in which the timeout period is doubled upon each retransmission, until either the node receives a response or the timeout period reaches the value MAX_BINDACK_TIMEOUT [RFC6275]. The node MAY continue to send these messages at this slower rate indefinitely. The node MUST NOT send PBU messages to a particular node more than MAX_UPDATE_RATE times within a second [RFC6275]. 3.7. The Distributed Logical Interface (DLIF) concept One of the main challenges of a network-based DMM solution is how to allow a mobile node to simultaneously send/receive traffic which is anchored at different MAARs, and how to influence the mobile node's selection process of its source IPv6 address for a new flow, without requiring special support from the mobile node's IP stack. This document defines the Distributed Logical Interface (DLIF), which is a software construct in the MAAR that allows to easily hide the change of associated anchors from the mobile node. Bernardos, et al. Expires September 9, 2020 [Page 14] Internet-Draft PMIPv6 DMM and DLIF March 2020 +---------------------------------------------------+ ( Operator's ) ( core ) +---------------------------------------------------+ | | +---------------+ tunnel +---------------+ | IP stack |===============| IP stack | +---------------+ +-------+-------+ | mn1mar1 |--+ (DLIFs) +--|mn1mar1|mn1mar2|--+ +---------------+ | | +-------+-------+ | | phy interface | | | | phy interface | | +---------------+ | | +---------------+ | MAAR1 (o) (o) MAAR2 (o) x x x x prefA::/64 x x prefB::/64 (AdvPrefLft=0) x x (o) | +-----+ prefA::MN1 | MN1 | prefB::MN1 (deprecated) +-----+ Figure 5: DLIF: exposing multiple routers (one per P-MAAR) The basic idea of the DLIF concept is the following: each serving MAAR exposes itself towards a given MN as multiple routers, one per P-MAAR associated to the MN. Let's consider the example shown in Figure 5, MN1 initially attaches to MAAR1, configuring an IPv6 address (prefA::MN1) from a prefix locally anchored at MAAR1 (prefA::/64). At this stage, MAAR1 plays both the role of anchoring and serving MAAR, and also behaves as a plain IPv6 access router. MAAR1 creates a distributed logical interface to communicate (point- to-point link) with MN1, exposing itself as a (logical) router with a specific MAC and IPv6 addresses (e.g., prefA::MAAR1/64 and fe80::MAAR1/64) using the DLIF mn1mar1. As explained below, these addresses represent the "logical" identity of MAAR1 towards MN1, and will "follow" the mobile node while roaming within the domain (note that the place where all this information is maintained and updated is out-of-scope of this draft; potential examples are to keep it on the home subscriber server -- HSS -- or the user's profile). If MN1 moves and attaches to a different MAAR of the domain (MAAR2 in the example of Figure 5), this MAAR will create a new logical interface (mn1mar2) to expose itself towards MN1, providing it with a locally anchored prefix (prefB::/64). In this case, since the MN1 has another active IPv6 address anchored at a MAAR1, MAAR2 also needs to create an additional logical interface configured to resemble the Bernardos, et al. Expires September 9, 2020 [Page 15] Internet-Draft PMIPv6 DMM and DLIF March 2020 one used by MAAR1 to communicate with MN1. In this example, there is only one P-MAAR (in addition to MAAR2, which is the serving one): MAAR1, so only the logical interface mn1mar1 is created, but the same process would be repeated in case there were more P-MAARs involved. In order to maintain the prefix anchored at MAAR1 reachable, a tunnel between MAAR1 and MAAR2 is established and the routing is modified accordingly. The PBU/PBA signaling is used to set-up the bi- directional tunnel between MAAR1 and MAAR2, and it might also be used to convey to MAAR2 the information about the prefix(es) anchored at MAAR1 and about the addresses of the associated DLIF (i.e., mn1mar1). +------------------------------------------+ +----------------------+ | MAAR1 | | MAAR2 | |+----------------------------------------+| |+--------------------+| ||+------------------++------------------+|| ||+------------------+|| |||+-------++-------+||+-------++-------+||| |||+-------++-------+||| ||||mn3mar1||mn3mar2||||mn2mar1||mn2mar2|||| ||||mn1mar1||mn1mar2|||| |||| LMAC1 || LMAC2 |||| LMAC3 || LMAC4 |||| |||| LMAC5 || LMAC6 |||| |||+-------++-------+||+-------++-------+||| |||+-------++-------+||| ||| LIFs of MN3 || LIFs of MN2 ||| ||| LIFs of MN1 ||| ||+------------------++------------------+|| ||+------------------+|| || MAC1 (phy if MAAR1) || || MAC2 (phy if MAAR2)|| |+----------------------------------------+| |+--------------------+| +------------------------------------------+ +----------------------+ x x x x x x (o) (o) (o) | | | +--+--+ +--+--+ +--+--+ | MN3 | | MN2 | | MN1 | +-----+ +-----+ +-----+ Figure 6: Distributed Logical Interface concept Figure 6 shows the logical interface concept in more detail. The figure shows two MAARs and three MNs. MAAR1 is currently serving MN2 and MN3, while MAAR2 is serving MN1. Note that a serving MAAR always plays the role of anchoring MAAR for the attached (served) MNs. Each MAAR has one single physical wireless interface as depicted in this example. As introduced before, each MN always "sees" multiple logical routers -- one per anchoring MAAR -- independently of its currently serving MAAR. From the point of view of the MN, these MAARs are portrayed as different routers, although the MN is physically attached to one single interface. The way this is achieved is by the serving MAAR configuring different logical interfaces. Focusing on MN1, it is currently attached to MAAR2 (i.e., MAAR2 is its serving MAAR) and, Bernardos, et al. Expires September 9, 2020 [Page 16] Internet-Draft PMIPv6 DMM and DLIF March 2020 therefore, it has configured an IPv6 address from MAAR2's pool (e.g., prefB::/64). MAAR2 has set-up a logical interface (mn1mar2) on top of its wireless physical interface (phy if MAAR2) which is used to serve MN1. This interface has a logical MAC address (LMAC6), different from the hardware MAC address (MAC2) of the physical interface of MAAR2. Over the mn1mar2 interface, MAAR2 advertises its locally anchored prefix prefB::/64. Before attaching to MAAR2, MN1 was attached to MAAR1, configuring also an address locally anchored at that MAAR, which is still being used by MN1 in active communications. MN1 keeps "seeing" an interface connecting to MAAR1, as if it were directly connected to the two MAARs. This is achieved by the serving MAAR (MAAR2) configuring an additional distributed logical interface: mn1mar1, which behaves as the logical interface configured by MAAR1 when MN1 was attached to it. This means that both the MAC and IPv6 addresses configured on this logical interface remain the same regardless of the physical MAAR which is serving the MN. The information required by a serving MAAR to properly configure this logical interfaces can be obtained in different ways: as part of the information conveyed in the PBA, from an external database (e.g., the HSS) or by other means. As shown in the figure, each MAAR may have several logical interfaces associated to each attached MN, having always at least one (since a serving MAAR is also an anchoring MAAR for the attached MN). In order to enforce the use of the prefix locally anchored at the serving MAAR, the router advertisements sent over those logical interfaces playing the role of anchoring MAARs (different from the serving one) include a zero preferred prefix lifetime (and a non-zero valid prefix lifetime, so the prefix remains valid, while being deprecated). The goal is to deprecate the prefixes delegated by these MAARs (so that they will no longer be serving the MN). Note that on-going communications may keep on using those addresses, even if they are deprecated, so this only affects the establishment of new sessions. The distributed logical interface concept also enables the following use case: suppose that access to a local IP network is provided by a given MAAR (e.g., MAAR1 in the example shown in Figure 5) and that the resources available at that network cannot be reached from outside the local network (e.g., cannot be accessed by an MN attached to MAAR2). This is similar to the local IP access scenario considered by 3GPP, where a local gateway node is selected for sessions requiring access to services provided locally (instead of going through a central gateway). The goal is to allow an MN to be able to roam while still being able to have connectivity to this local IP network. The solution adopted to support this case makes use of RFC 4191 [RFC4191] more specific routes when the MN moves to a MAAR different from the one providing access to the local IP network Bernardos, et al. Expires September 9, 2020 [Page 17] Internet-Draft PMIPv6 DMM and DLIF March 2020 (MAAR1 in the example). These routes are advertised through the distributed logical interface representing the MAAR providing access to the local network (MAAR1 in this example). In this way, if MN1 moves from MAAR1 to MAAR2, any active session that MN1 may have with a node on the local network connected to MAAR1 will survive via the tunnel between MAAR1 and MAAR2. Also, any potential future connection attempt towards the local network will be supported, even though MN1 is no longer attached to MAAR1. 4. Message Format This section defines extensions to the Proxy Mobile IPv6 [RFC5213] protocol messages. 4.1. Proxy Binding Update A new flag (D) is included in the Proxy Binding Update to indicate that the Proxy Binding Update is coming from a MAAR or a CMD and not from a mobile access gateway. The rest of the Proxy Binding Update format remains the same as defined in [RFC5213]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A|H|L|K|M|R|P|F|T|B|S|D| Rsrvd | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Mobility options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ DMM Flag (D) The D Flag is set to indicate to the receiver of the message that the Proxy Binding Update is from a MAAR or a CMD. When an LMA that does not support the extensions described in this document receives a message with the D-Flag set, the PBU in that case MUST NOT be processed by the LMA and an error MUST be returned. Mobility Options Variable-length field of such length that the complete Mobility Header is an integer multiple of 8 octets long. This field contains zero or more TLV-encoded mobility options. The encoding Bernardos, et al. Expires September 9, 2020 [Page 18] Internet-Draft PMIPv6 DMM and DLIF March 2020 and format of defined options are described in Section 6.2 of [RFC6275]. The receiving node MUST ignore and skip any options that it does not understand. 4.2. Proxy Binding Acknowledgment A new flag (D) is included in the Proxy Binding Acknowledgment to indicate that the sender supports operating as a MAAR or CMD. The rest of the Proxy Binding Acknowledgment format remains the same as defined in [RFC5213]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status |K|R|P|T|B|S|D| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Mobility options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ DMM Flag (D) The D flag is set to indicate that the sender of the message supports operating as a MAAR or a CMD. When a MAG that does not support the extensions described in this document receives a message with the D-Flag set, it MUST ignore the message and an error MUST be returned. Mobility Options Variable-length field of such length that the complete Mobility Header is an integer multiple of 8 octets long. This field contains zero or more TLV-encoded mobility options. The encoding and format of defined options are described in Section 6.2 of [RFC6275]. The MAAR MUST ignore and skip any options that it does not understand. 4.3. Anchored Prefix Option A new Anchored Prefix option is defined for use with the Proxy Binding Update and Proxy Binding Acknowledgment messages exchanged between MAARs and CMDs. Therefore, this option can only appear if the D bit is set in a PBU/PBA. This option is used for exchanging Bernardos, et al. Expires September 9, 2020 [Page 19] Internet-Draft PMIPv6 DMM and DLIF March 2020 the mobile node's prefix anchored at the anchoring MAAR. There can be multiple Anchored Prefix options present in the message. The Anchored Prefix Option has an alignment requirement of 8n+4. Its format is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Anchored Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type IANA-1. Length 8-bit unsigned integer indicating the length of the option in octets, excluding the type and length fields. This field MUST be set to 18. Reserved This field is unused for now. The value MUST be initialized to 0 by the sender and MUST be ignored by the receiver. Prefix Length 8-bit unsigned integer indicating the prefix length in bits of the IPv6 prefix contained in the option. Anchored Prefix A sixteen-octet field containing the mobile node's IPv6 Anchored Prefix. Only the first Prefix Length bits are valid for the Anchored Prefix. The rest of the bits MUST be ignored. Bernardos, et al. Expires September 9, 2020 [Page 20] Internet-Draft PMIPv6 DMM and DLIF March 2020 4.4. Local Prefix Option A new Local Prefix option is defined for use with the Proxy Binding Update and Proxy Binding Acknowledgment messages exchanged between MAARs or between a MAAR and a CMD. Therefore, this option can only appear if the D bit is set in a PBU/PBA. This option is used for exchanging a prefix of a local network that is only reachable via the anchoring MAAR. There can be multiple Local Prefix options present in the message. The Local Prefix Option has an alignment requirement of 8n+4. Its format is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Local Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type IANA-2. Length 8-bit unsigned integer indicating the length of the option in octets, excluding the type and length fields. This field MUST be set to 18. Reserved This field is unused for now. The value MUST be initialized to 0 by the sender and MUST be ignored by the receiver. Prefix Length 8-bit unsigned integer indicating the prefix length in bits of the IPv6 prefix contained in the option. Local Prefix Bernardos, et al. Expires September 9, 2020 [Page 21] Internet-Draft PMIPv6 DMM and DLIF March 2020 A sixteen-octet field containing the IPv6 Local Prefix. Only the first Prefix Length bits are valid for the IPv6 Local Prefix. The rest of the bits MUST be ignored. 4.5. Previous MAAR Option This new option is defined for use with the Proxy Binding Acknowledgement messages exchanged by the CMD to a MAAR. This option is used to notify the S-MAAR about the previous MAAR's global address and the prefix anchored to it. There can be multiple Previous MAAR options present in the message. Its format is as follows: The Previous MAAR Option has an alignment requirement of 8n+4. Its format is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + P-MAAR's address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Home Network Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type IANA-3. Length 8-bit unsigned integer indicating the length of the option in octets, excluding the type and length fields. This field MUST be set to 34. Reserved Bernardos, et al. Expires September 9, 2020 [Page 22] Internet-Draft PMIPv6 DMM and DLIF March 2020 This field is unused for now. The value MUST be initialized to 0 by the sender and MUST be ignored by the receiver. Prefix Length 8-bit unsigned integer indicating the prefix length in bits of the IPv6 prefix contained in the option. Previous MAAR's address A sixteen-octet field containing the P-MAAR's IPv6 global address. Home Network Prefix A sixteen-octet field containing the mobile node's IPv6 Home Network Prefix. Only the first Prefix Length bits are valid for the mobile node's IPv6 Home Network Prefix. The rest of the bits MUST be ignored. 4.6. Serving MAAR Option This new option is defined for use with the Proxy Binding Update message exchanged between the CMD and a Previous MAAR. This option is used to notify the P-MAAR about the current Serving MAAR's global address. Its format is as follows: The Serving MAAR Option has an alignment requirement of 8n+6. Its format is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + S-MAAR's address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type IANA-4. Bernardos, et al. Expires September 9, 2020 [Page 23] Internet-Draft PMIPv6 DMM and DLIF March 2020 Length 8-bit unsigned integer indicating the length of the option in octets, excluding the type and length fields. This field MUST be set to 16. Serving MAAR's address A sixteen-octet field containing the S-MAAR's IPv6 global address. 4.7. DLIF Link-local Address Option A new DLIF Link-local Address option is defined for use with the Proxy Binding Acknowledgment message exchanged between MAARs and between a MAAR and a CMD. This option is used for exchanging the link-local address of the DLIF to be configured on the serving MAAR so it resembles the DLIF configured on the P-MAAR. The DLIF Link-local Address option has an alignment requirement of 8n+6. Its format is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + DLIF Link-local Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type IANA-5. Length 8-bit unsigned integer indicating the length of the option in octets, excluding the type and length fields. This field MUST be set to 16. DLIF Link-local Address Bernardos, et al. Expires September 9, 2020 [Page 24] Internet-Draft PMIPv6 DMM and DLIF March 2020 A sixteen-octet field containing the link-local address of the logical interface. 4.8. DLIF Link-layer Address Option A new DLIF Link-layer Address option is defined for use with the Proxy Binding Acknowledgment message exchanged between MAARs and betwwe a MAAR and a CMD. This option is used for exchanging the link-layer address of the DLIF to be configured on the serving MAAR so it resembles the DLIF configured on the P-MAAR. The format of the DLIF Link-layer Address option is shown below. Based on the size of the address, the option MUST be aligned appropriately, as per mobility option alignment requirements specified in [RFC6275]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + DLIF Link-layer Address + . ... . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type IANA-6. Length 8-bit unsigned integer indicating the length of the option in octets, excluding the type and length fields. Reserved This field is unused for now. The value MUST be initialized to 0 by the sender and MUST be ignored by the receiver. DLIF Link-layer Address A variable length field containing the link-layer address of the logical interface to be configured on the S-MAAR. The content and format of this field (including octet and bit ordering) is as specified in Section 4.6 of [RFC4861] for carrying Bernardos, et al. Expires September 9, 2020 [Page 25] Internet-Draft PMIPv6 DMM and DLIF March 2020 link-layer addresses. On certain access links, where the link- layer address is not used or cannot be determined, this option cannot be used. 5. IANA Considerations This document defines six new mobility options, the Anchored Prefix Option, the Local Prefix Option, the Previous MAAR Option, the Serving MAAR Option, the DLIF Link-local Address Option and the DLIF Link-layer Address Option. The Type value for these options needs to be assigned from the same numbering space as allocated for the other mobility options in the "Mobility Options" registry defined in http://www.iana.org/assignments/mobility-parameters. The required IANA actions are marked as IANA-1 to IANA-6. This document reserves a new flag (D) in the "Binding Update Flags" and a new flag (D) in the "Binding Acknowledgment Flags" of the "Mobile IPv6 parameters" registry http://www.iana.org/assignments/ mobility-parameters. 6. Security Considerations The protocol extensions defined in this document share the same security concerns of Proxy Mobile IPv6 [RFC5213]. It is recommended that the signaling messages, Proxy Binding Update and Proxy Binding Acknowledgment, exchanged between the MAARs are protected using IPsec using the established security association between them. This essentially eliminates the threats related to the impersonation of a MAAR. When the CMD acts as a PBU/PBA relay, the CMD may act as a relay of a single PBU to multiple previous MAARs. In situations of many fast handovers (e.g., with vehicular networks), there may exist multiple previous (e.g., k) MAARs. In this situation, the CMD creates k outgoing packets from a single incoming packet. This bears a certain amplification risk. The CMD MUST use a pacing approach in the outgoing queue to cap the output traffic (i.e., the rate of PBUs sent) to limit this amplification risk. When the CMD acts as MAAR locator, mobility signaling (PBAs) is exchanged between P-MAARs and current S-MAAR. Hence, security associations are REQUIRED to exist between the involved MAARs (in addition to the ones needed with the CMD). Since deregistration is performed by timeout, measures SHOULD be implemented to minimize the risks associated to continued resource consumption (DoS attacks), e.g., imposing a limit of the number of P-MAARs associated to a given MN. Bernardos, et al. Expires September 9, 2020 [Page 26] Internet-Draft PMIPv6 DMM and DLIF March 2020 The CMD and the participating MAARs MUST be trusted parties, authorized perform all operations relevant to their role. There are some privacy considerations to consider. While the involved parties trust each other, the signalling involves disclosing information about the previous locations visited by each MN, as well as the active prefixes they are using at a given point of time. Therefore, mechanisms MUST be in place to ensure that MAARs and CMD do not disclose this information to other parties nor use it for other ends that providing the distributed mobility support specified in this document. 7. Acknowledgments The authors would like to thank Dirk von Hugo, John Kaippallimalil, Ines Robles, Joerg Ott, Carlos Pignataro, Vincent Roca, Mirja Kuehlewind, Eric Vyncke, Adam Roach, Benjamin Kaduk and Roman Danyliw for the comments on this document. The authors would also like to thank Marco Liebsch, Dirk von Hugo, Alex Petrescu, Daniel Corujo, Akbar Rahman, Danny Moses, Xinpeng Wei and Satoru Matsushima for their comments and discussion on the documents [I-D.bernardos-dmm-distributed-anchoring] and [I-D.bernardos-dmm-pmip] on which the present document is based. The authors would also like to thank Lyle Bertz and Danny Moses for their in-deep review of this document and their very valuable comments and suggestions. 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, November 2005, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . Bernardos, et al. Expires September 9, 2020 [Page 27] Internet-Draft PMIPv6 DMM and DLIF March 2020 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, DOI 10.17487/RFC5213, August 2008, . [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 2011, . [RFC7333] Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J. Korhonen, "Requirements for Distributed Mobility Management", RFC 7333, DOI 10.17487/RFC7333, August 2014, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 8.2. Informative References [I-D.bernardos-dmm-distributed-anchoring] Bernardos, C. and J. Zuniga, "PMIPv6-based distributed anchoring", draft-bernardos-dmm-distributed-anchoring-09 (work in progress), May 2017. [I-D.bernardos-dmm-pmip] Bernardos, C., Oliva, A., and F. Giust, "A PMIPv6-based solution for Distributed Mobility Management", draft- bernardos-dmm-pmip-09 (work in progress), September 2017. [RFC7429] Liu, D., Ed., Zuniga, JC., Ed., Seite, P., Chan, H., and CJ. Bernardos, "Distributed Mobility Management: Current Practices and Gap Analysis", RFC 7429, DOI 10.17487/RFC7429, January 2015, . [RFC8563] Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky, Ed., "Bidirectional Forwarding Detection (BFD) Multipoint Active Tails", RFC 8563, DOI 10.17487/RFC8563, April 2019, . Authors' Addresses Bernardos, et al. Expires September 9, 2020 [Page 28] Internet-Draft PMIPv6 DMM and DLIF March 2020 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/ Antonio de la Oliva Universidad Carlos III de Madrid Av. Universidad, 30 Leganes, Madrid 28911 Spain Phone: +34 91624 8803 Email: aoliva@it.uc3m.es URI: http://www.it.uc3m.es/aoliva/ Fabio Giust Athonet S.r.l. Email: fabio.giust.2011@ieee.org Juan Carlos Zuniga SIGFOX 425 rue Jean Rostand Labege 31670 France Email: j.c.zuniga@ieee.org URI: http://www.sigfox.com/ Alain Mourad InterDigital Europe Email: Alain.Mourad@InterDigital.com URI: http://www.InterDigital.com/ Bernardos, et al. Expires September 9, 2020 [Page 29]