| RFC 8885 | PMIPv6 DMM and DLIF | October 2020 |
| Bernardos, et al. | Experimental | [Page] |
Distributed Mobility Management solutions allow networks to be set up in such a way that traffic is distributed optimally and centrally deployed anchors are not relied upon to provide IP mobility support.¶
There are many different approaches to address Distributed Mobility Management -- 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 the mobility anchor and access router). The mobility anchor and access router is an enhanced access router that 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 the simultaneous anchoring several flows at different distributed gateways.¶
This document is not an Internet Standards Track specification; it is published for examination, experimental implementation, and evaluation.¶
This document defines an Experimental Protocol for the Internet community. 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 candidates for any level of Internet Standard; see Section 2 of RFC 7841.¶
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8885.¶
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.¶
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].¶
The two most relevant examples of current IP mobility solutions are Mobile IPv6 [RFC6275] and Proxy Mobile IPv6 (PMIPv6) [RFC5213]. These solutions offer mobility support at the cost of handling operations at a cardinal point (i.e., the mobility anchor) and burdening it with data forwarding and control mechanisms for a large number of users. The mobility anchor is the home agent for Mobile IPv6 and the local mobility anchor for PMIPv6. 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 because it is not possible to define finer granularity policies, for example, on a per-application basis).¶
The purpose of DMM 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 and is deployed in the default gateway of the MN. 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 MN's involvement. But differently from PMIPv6, when the MN moves from one access network to another, the router anchoring the MN's address may change, 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 assigned by the MAAR to the MNs attached to it and are routable at that MAAR. Prefixes are assigned to MNs attached to 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 mobile access gateways (MAGs), whereas the control plane is kept centralized towards a cardinal node (used as an information store), which is discharged from any route management and MN's data forwarding tasks.¶
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.¶
The following terms used in this document are defined in the PMIPv6 specification [RFC5213]:¶
The following terms used in this document are defined in the Mobile IPv6 (MIPv6) specification [RFC6275]:¶
The following terms are used in this document:¶
The following terms are defined and used in this document:¶
The solution consists of decoupling 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 the 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:¶
The MAARs leverage the CMD to access and update information related to the MNs, which is stored as mobility sessions; hence, a centralized node maintains a global view of the network status. The CMD is queried whenever an MN is detected joining/leaving 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, one method for the initial registration and three different approaches for updating the mobility sessions using PBUs and PBAs are presented. Each approach assigns a different role to the CMD:¶
The solution described in this document allows per-prefix anchoring decisions -- for example, to support the anchoring of some flows 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 an 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.¶
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:¶
Upon MN attachment, the following operations take place:¶
Note that:¶
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 Packet flow
Note that the registration process does not change regardless of the CMD's modes (relay, locator, or proxy) described in the following sections. The procedure is depicted in Figure 1.¶
Upon MN mobility, if the CMD behaves as a PBU/PBA relay, the following operations take place:¶
+-----+ +---+ +-----+ +--+ +--+
|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 Packet flow
PBU/PBA messages with * contain
a new mobility option
For MN's next movements, the process is repeated, but the number of P-MAARs involved increases (according 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 P-MAAR registered as the current P-CoA (i.e., the MAAR prior to handover) plus the ones in the P-MAAR list. Those P-MAARs reply with a PBA to the CMD, which aggregates all of the PBAs into one PBA to notify the S-MAAR, which 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 with 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 by 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 retransmissions and rate-limiting considerations described in Section 3.6, especially when aggregating and relaying PBAs.¶
When there are multiple P-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 originating from the CMD, albeit to different targets. Pacing mechanisms MUST be introduced to avoid bursts on the outgoing link.¶
The handover latency experienced in the approach shown before can be reduced if the P-MAARs are allowed to directly signal 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 Serving 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 Serving 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 Home Network Prefix (HNP) option and the P-MAAR's address is taken from the message's source address. The CMD is released 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. The data forwarding is unaltered.¶
+-----+ +---+ +-----+ +--+ +--+
|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 Packet flow
PBU/PBA messages with * contain
a new mobility option
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 the Previous MAAR option in this case. In parallel, a PBU is sent by the CMD to the P-MAARs containing the Serving MAAR option to notify them about the new MN's location so that 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 has concluded and the information is updated in all network nodes. This procedure is obtained from the first procedure rearranging 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.¶
+-----+ +---+ +-----+ +--+ +--+
|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 Packet flow
PBU/PBA messages with * contain
a new mobility option
The de-registration mechanism devised for PMIPv6 cannot be used as is in this solution because each MAAR handles an independent mobility session (i.e., a single prefix or a set of prefixes) for a given MN, whereas the aggregated session is stored at the CMD. Indeed, if a P-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 the 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 an S-MAAR to de-register the whole MN session. This can be achieved by first removing any L2 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:¶
The node sending PBUs (the CMD or S-MAAR) SHOULD make use of the timeout to also 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].¶
One of the main challenges of a network-based DMM solution is how to allow a MN to simultaneously send/receive traffic that is anchored at different MAARs and how to influence the MN's selection process of its source IPv6 address for a new flow without requiring special support from the MN's IP stack. This document defines the DLIF, which is a software construct in the MAAR that can easily hide the change of associated anchors from the MN.¶
+---------------------------------------------------+
( 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) +-----+
The basic idea of the DLIF concept is the following: each S-MAAR exposes itself to a given MN as multiple routers, one per P-MAAR associated with 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 the role of both anchoring and serving MAAR and also behaves as a plain IPv6 access router. MAAR1 creates a DLIF to communicate (through a point-to-point link) with MN1, exposing itself as a (logical) router with 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 for MN1 and will "follow" the MN while roaming within the domain (note that the place where all this information is maintained and updated is out of scope of this document; 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 to MN1, providing it with a locally anchored prefix (prefB::/64). In this case, since the MN1 has another active IPv6 address anchored at MAAR1, MAAR2 also needs to create an additional logical interface configured to resemble the one used by MAAR1 to communicate with MN1. In this example, MAAR1 is the only P-MAAR (MAAR2 is the same as S-MAAR), so only the logical interface mn1mar1 is created. However, the same process would be repeated if more P-MAARs were involved. In order to keep 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 bidirectional tunnel between MAAR1 and MAAR2, and it might also be used to convey the information about the prefix(es) anchored at MAAR1 and the addresses of the associated DLIF (i.e., mn1mar1) to MAAR2.¶
+------------------------------------------+ +----------------------+
| 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 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 an S-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 discussed before, each MN always "sees" multiple logical routers -- one per anchoring MAAR -- independently of its currently S-MAAR. From the point of view of the MN, these MAARs are portrayed as different routers, although the MN is physically attached to a single interface. This is achieved by the S-MAAR configuring different logical interfaces. MN1 is currently attached to MAAR2 (i.e., MAAR2 is its S-MAAR) and, 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) that is 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 and configured a locally anchored address 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 S-MAAR (MAAR2) configuring an additional DLIF, 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 that is serving the MN. The information required by an S-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 with each attached MN and always has at least one (since an S-MAAR is also an anchoring MAAR for the attached MN).¶
In order to enforce the use of the prefix locally anchored at the S-MAAR, the RAs 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 ongoing communications may keep on using those addresses even if they are deprecated, so this only affects the establishment of new sessions.¶
The DLIF 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 more specific routes, as discussed in RFC 4191 [RFC4191], when the MN moves to a MAAR different from the one providing access to the local IP network (MAAR1 in the example). These routes are advertised through the DLIF where the MAAR is 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 to the local network will be supported even though MN1 is no longer attached to MAAR1, so long as a source address configured from MAAR1 is selected for new connections (see [RFC6724], rule 5.5).¶
This section defines extensions to the PMIPv6 [RFC5213] protocol messages.¶
A new flag (D) is included in the PBU to indicate that the PBU is coming from a MAAR or a CMD and not from a MAG. The rest of the PBU 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 .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
A new flag (D) is included in the PBA to indicate that the sender supports operating as a MAAR or CMD. The rest of the PBA 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 .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
A new Anchored Prefix option is defined for use with the PBU and PBA 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 the MN'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 + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
A new Local Prefix option is defined for use with the PBU and PBA 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 + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
This new option is defined for use with the PBA messages exchanged by the CMD to a MAAR. This option is used to notify the S-MAAR about the P-MAAR's global address and the prefix anchored to it. There can be multiple Previous MAAR options present in the message.¶
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Previous MAAR + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Home Network Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
This new option is defined for use with the PBU message exchanged between the CMD and a P-MAAR. This option is used to notify the P-MAAR about the current S-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 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
A new DLIF Link-Local Address option is defined for use with the PBA 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 S-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 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
A new DLIF Link-Layer Address option is defined for use with the PBA message exchanged between MAARs and between a MAAR and a CMD. This option is used for exchanging the link-layer address of the DLIF to be configured on the S-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 the 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 + . ... . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
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 link-layer addresses. On certain access links where the link-layer address is not used or cannot be determined, this option cannot be used.¶
This document defines six new mobility options: Anchored Prefix, Local Prefix, Previous MAAR, Serving MAAR, DLIF Link-Local Address, and DLIF Link-Layer Address. IANA has assigned Type values for these options 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.¶
This document reserves a new flag (D) with a value of 0x0010 in the "Binding Update Flags" registry and a new flag (D) with a value of 0x02 in the "Binding Acknowledgment Flags" of the "Mobile IPv6 parameters" registry (http://www.iana.org/assignments/mobility-parameters).¶
The protocol extensions defined in this document share the same security concerns of PMIPv6 [RFC5213]. It is recommended that the signaling messages, PBU and PBA, exchanged between the MAARs be protected using IPsec, specifically by 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 P-MAARs. In situations with many fast handovers (e.g., with vehicular networks), multiple previous (e.g., k) MAARs may exist. 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 a MAAR locator, mobility signaling (PBAs) is exchanged between P-MAARs and the current S-MAAR. Hence, security associations are REQUIRED to exist between the involved MAARs (in addition to the ones needed with the CMD).¶
Since de-registration is performed by timeout, measures SHOULD be implemented to minimize the risks associated with continued resource consumption (DoS attacks), e.g., imposing a limit on the number of P-MAARs associated with a given MN.¶
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 signaling 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 CMDs do not disclose this information to other parties or use it for other ends than providing the distributed mobility support specified in this document.¶
The authors would like to thank Dirk von Hugo, John Kaippallimalil, Ines Robles, Joerg Ott, Carlos Pignataro, Vincent Roca, Mirja Kühlewind, Éric 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 [DISTRIBUTED-ANCHORING] and [DMM-PMIP], on which the present document is based.¶
The authors would also like to thank Lyle Bertz and Danny Moses for their in-depth review of this document and their very valuable comments and suggestions.¶