Proxy Mobile IPv6 Extensions for Distributed Mobility ManagementUniversidad Carlos III de MadridAv. Universidad, 30LeganesMadrid28911Spain+34 91624 6236cjbc@it.uc3m.eshttp://www.it.uc3m.es/cjbc/Universidad Carlos III de MadridAv. Universidad, 30LeganesMadrid28911Spain+34 91624 8803aoliva@it.uc3m.eshttp://www.it.uc3m.es/aoliva/Athonet S.r.l.via Ca' del Luogo 6/8Bolzano Vicentino (VI)36050Italyfabio.giust.research@gmail.comSIGFOX425 rue Jean RostandLabege31670Francej.c.zuniga@ieee.orghttp://www.sigfox.com/InterDigital EuropeAlain.Mourad@InterDigital.comhttp://www.InterDigital.com/
Internet
DMM Working GroupPMIPv6anchorsession continuityaddress reachabilityHNPCMDMAAR
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.
Status of This Memo
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
.
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
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Table of Contents
. Introduction
. Requirements Language
. Terminology
. PMIPv6 DMM Extensions
. Initial Registration
. The CMD as PBU/PBA Relay
. The CMD as MAAR Locator
. The CMD as PBU/PBA Proxy
. De-registration
. Retransmissions and Rate Limiting
. The Distributed Logical Interface (DLIF) Concept
. Message Format
. Proxy Binding Update
. Proxy Binding Acknowledgement
. Anchored Prefix Option
. Local Prefix Option
. Previous MAAR Option
. Serving MAAR Option
. DLIF Link-Local Address Option
. DLIF Link-Layer Address Option
. IANA Considerations
. Security Considerations
. References
. Normative References
. Informative References
Acknowledgements
Authors' Addresses
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) .
The two most relevant examples of current IP mobility solutions are Mobile
IPv6 and Proxy Mobile IPv6 (PMIPv6)
. 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 , 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 ; 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 . 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.
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
when, and only when, they appear in all capitals, as shown here.
Terminology
The following terms used in this document are defined in the PMIPv6
specification :
BCE:
Binding Cache Entry
LMA:
Local Mobility Anchor
MAG:
Mobile Access Gateway
MN:
Mobile Node
P-CoA:
Proxy Care-of Address
PBA:
Proxy Binding Acknowledgement
PBU:
Proxy Binding Update
The following terms used in this document are defined in the Mobile IPv6
(MIPv6) specification :
CN:
Correspondent Node
The following terms are used in this document:
Home Control-Plane Anchor (Home-CPA or H-CPA):
The Home-CPA function hosts the MN's mobility
session. There can be more than one mobility session for an MN, and those sessions may be anchored on the same or different
Home-CPAs. 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 addresses
and/or prefixes.
The Home-DPA is chosen by the Home-CPA on a session basis. The Home-DPA is in the forwarding path for all the MN's IP traffic.
Access Control Plane Node (Access-CPN or A-CPN):
The Access-CPN is responsible for interfacing with the MN's Home-CPA and 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 MN is attached. This function is not hosted on a
Layer 2 (L2) bridging device such as an 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 MNs attach. 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 an 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 an MN in
cases when the MN is frequently switching points of attachment while
maintaining long-lasting flows.
S-MAAR (Serving MAAR):
The MAAR to which the MN is currently attached. 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 with 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.
PMIPv6 DMM Extensions
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 LMA is discharged from the data forwarding role; only the Binding Cache and
its management operations are maintained. Hence, the LMA is renamed as "CMD",
which is therefore a Home-CPA. Also, the CMD is able to send and parse both PBU
and PBA messages.
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.
The Binding Cache will be extended to include information regarding P-MAARs
where the MN was anchored and still retains active data sessions.
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,
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 CMD is a PBU/PBA relay;
The CMD is only a MAAR locator;
The CMD is a PBU/PBA proxy.
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 . 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
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 ), it is assumed that:
The MN is attaching to MAAR1.
The MN is authorized to attach to the network.
Upon MN attachment, the following operations take place:
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 BCE.
MAAR1 sends a PBU with Pref1 and the MN's MN-ID to the
CMD.
Since this is an initial registration, the CMD stores a BCE containing the
MN-ID, Pref1, and MAAR1's address (as a Proxy-CoA) as the primary fields.
The CMD replies with a PBA with the usual options defined in PMIPv6 , meaning that the MN's registration is fresh and no past
status is available.
MAAR1 stores the BCE described in (1) and unicasts a Router Advertisement (RA) to
the MN with Pref1.
The MN uses Pref1 to configure an IPv6 address (IP1) (e.g., with stateless
address autoconfiguration (SLAAC)).
Note that:
Alternative IPv6 autoconfiguration mechanisms can also be used, though this
document describes the SLAAC-based one.
IP1 is routable at MAAR1 in the sense that it is on the path of packets
addressed to the MN.
MAAR1 acts as a plain router for packets destined to the MN as no encapsulation
or special handling takes place.
In the diagram shown in (and subsequent diagrams),
the flow of packets is presented using '*'.
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 .
The CMD as PBU/PBA Relay
Upon MN mobility, if the CMD behaves as a PBU/PBA relay, the following operations take place:
When the MN moves from its current point of attachment and attaches to MAAR2
(now the S-MAAR), MAAR2 reserves an IPv6 prefix (Pref2), stores a temporary
BCE, and sends a PBU to the CMD for registration.
Upon PBU reception and BC lookup, the CMD retrieves an already existing entry
for the MN and binds the MN-ID to its former location; thus, the CMD forwards the
PBU to the MAAR indicated as Proxy-CoA (MAAR1) and includes a new mobility option
to communicate the S-MAAR's global address to MAAR1 (defined as the Serving MAAR
option in ). The CMD updates the P-CoA field in
the BCE related to the MN with the S-MAAR's address.
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. The PBA contains the prefix anchored at MAAR1 in the Home Network Prefix
option.
The CMD, after receiving the PBA, updates the BCE and populates 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, which contains the previous Proxy-CoA and the
prefix anchored to it embedded into a new mobility option called the Previous MAAR
option (defined in ). Then, upon PBA
arrival, a bidirectional tunnel can be established between the two MAARs, and
new routes are set appropriately to recover the IP flow(s) carrying Pref1.
Now, packets destined for Pref1 are first received by MAAR1, encapsulated into the
tunnel, and forwarded to MAAR2, which finally delivers them to their destination.
In the uplink, when the MN transmits packets using Pref1 as a source address, they are
sent to MAAR2 (as it is the MN's new default gateway) and then tunneled to MAAR1, which
routes them towards the next hop to the destination. Conversely, packets carrying
Pref2 are routed by MAAR2 without any special packet handling both for the uplink
and downlink.
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
, 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 CMD as MAAR Locator
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 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. illustrates the new message
sequence. The data forwarding is unaltered.
The CMD as PBU/PBA 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 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 , where, again, the data forwarding is kept untouched.
De-registration
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:
A P-MAAR stops the BCE timer upon receiving a PBU from the CMD containing
a "Serving MAAR" option. In this way, only the S-MAAR is allowed to
de-register the mobility session, arguing that the MN definitely left the
domain.
P-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 renewing the session if the MN is still
connected to the domain.
Retransmissions and Rate Limiting
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 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 . 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 .
The Distributed Logical Interface (DLIF) Concept
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.
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 : 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 ), 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.
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 )
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 , 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 , rule 5.5).
Message Format
This section defines extensions to the PMIPv6 protocol messages.
Proxy Binding Update
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 .
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 PBU 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 that is a multiple of 8 octets long. This field contains zero or more TLV-encoded
mobility options. The encoding and format of the defined options are described in . The receiving node MUST ignore and
skip any options that it does not understand.
Proxy Binding Acknowledgement
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 .
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 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 the defined options are described in . The MAAR MUST ignore and skip any
options that it does not understand.
Anchored Prefix Option
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 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
65
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 at the time of publication. 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 16-octet field containing the MN's IPv6 Anchored Prefix. Only the
first Prefix Length bits are valid for the Anchored Prefix option. The rest of the
bits MUST be ignored.
Local Prefix Option
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 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
66
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 at the time of publication. 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
A 16-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.
Previous MAAR Option
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 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
67
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
This field is unused at the time of publication. 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
A 16-octet field containing the P-MAAR's IPv6 global address.
Home Network Prefix
A 16-octet field containing the MN's IPv6 Home Network Prefix. Only
the first Prefix Length bits are valid for the MN's IPv6 Home Network
Prefix. The rest of the bits MUST be ignored.
Serving MAAR Option
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 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
68
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
A 16-octet field containing the S-MAAR's IPv6 global address.
DLIF Link-Local Address Option
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 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
69
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
A 16-octet field containing the link-local address of the logical interface.
DLIF Link-Layer Address Option
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 .
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
70
Length
8-bit unsigned integer indicating the length of the option in octets, excluding
the type and length fields.
Reserved
This field is unused at the time of publication. 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 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.
IANA Considerations
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 .
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 ().
Security Considerations
The protocol extensions defined in this document share the same security
concerns of PMIPv6 . 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.
ReferencesNormative ReferencesKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.Default Router Preferences and More-Specific RoutesThis document describes an optional extension to Router Advertisement messages for communicating default router preferences and more-specific routes from routers to hosts. This improves the ability of hosts to pick an appropriate router, especially when the host is multi-homed and the routers are on different links. The preference values and specific routes advertised to hosts require administrative configuration; they are not automatically derived from routing tables. [STANDARDS-TRACK]Neighbor Discovery for IP version 6 (IPv6)This document specifies the Neighbor Discovery protocol for IP Version 6. IPv6 nodes on the same link use Neighbor Discovery to discover each other's presence, to determine each other's link-layer addresses, to find routers, and to maintain reachability information about the paths to active neighbors. [STANDARDS-TRACK]Proxy Mobile IPv6Network-based mobility management enables IP mobility for a host without requiring its participation in any mobility-related signaling. The network is responsible for managing IP mobility on behalf of the host. The mobility entities in the network are responsible for tracking the movements of the host and initiating the required mobility signaling on its behalf. This specification describes a network-based mobility management protocol and is referred to as Proxy Mobile IPv6. [STANDARDS-TRACK]Mobility Support in IPv6This document specifies Mobile IPv6, a protocol that allows nodes to remain reachable while moving around in the IPv6 Internet. Each mobile node is always identified by its home address, regardless of its current point of attachment to the Internet. While situated away from its home, a mobile node is also associated with a care-of address, which provides information about the mobile node's current location. IPv6 packets addressed to a mobile node's home address are transparently routed to its care-of address. The protocol enables IPv6 nodes to cache the binding of a mobile node's home address with its care-of address, and to then send any packets destined for the mobile node directly to it at this care-of address. To support this operation, Mobile IPv6 defines a new IPv6 protocol and a new destination option. All IPv6 nodes, whether mobile or stationary, can communicate with mobile nodes. This document obsoletes RFC 3775. [STANDARDS-TRACK]Requirements for Distributed Mobility ManagementThis document defines the requirements for Distributed Mobility Management (DMM) at the network layer. The hierarchical structure in traditional wireless networks has led primarily to centrally deployed mobility anchors. As some wireless networks are evolving away from the hierarchical structure, it can be useful to have a distributed model for mobility management in which traffic does not need to traverse centrally deployed mobility anchors far from the optimal route. The motivation and the problems addressed by each requirement are also described.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.Informative ReferencesPMIPv6-based distributed anchoringDistributed Mobility Management solutions allow for setting up networks so that traffic is distributed in an optimal way and does not rely on centralized 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 (as 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 distributed gateway). The distributed gateway is an enhanced access router which is also able to operate as local mobility anchor or mobility access gateway, on a per prefix basis. The draft focuses on the required extensions to effectively support simultaneously anchoring several flows at different distributed gateways. This draft introduces the concept of distributed logical interface (at the distributed gateway), which is a software construct that allows to easily hide the change of anchor from the mobile node. Additionally, the draft describes how to provide session continuity in inter-domain scenarios in which dynamic tunneling or signaling between distributed gateways from different operators is not allowed.Work in ProgressA PMIPv6-based solution for Distributed Mobility ManagementThe number of mobile users and their traffic demand is expected to be ever-increasing in future years, and this growth can represent a limitation for deploying current mobility management schemes that are intrinsically centralized, e.g., Mobile IPv6 and Proxy Mobile IPv6. For this reason it has been waved a need for distributed and dynamic mobility management approaches, with the objective of reducing operators' burdens, evolving to a cheaper and more efficient architecture. This draft describes multiple solutions for network-based distributed mobility management inspired by the well known Proxy Mobile IPv6.Work in ProgressDefault Address Selection for Internet Protocol Version 6 (IPv6)This document describes two algorithms, one for source address selection and one for destination address selection. The algorithms specify default behavior for all Internet Protocol version 6 (IPv6) implementations. They do not override choices made by applications or upper-layer protocols, nor do they preclude the development of more advanced mechanisms for address selection. The two algorithms share a common context, including an optional mechanism for allowing administrators to provide policy that can override the default behavior. In dual-stack implementations, the destination address selection algorithm can consider both IPv4 and IPv6 addresses -- depending on the available source addresses, the algorithm might prefer IPv6 addresses over IPv4 addresses, or vice versa.Default address selection as defined in this specification applies to all IPv6 nodes, including both hosts and routers. This document obsoletes RFC 3484. [STANDARDS-TRACK]Distributed Mobility Management: Current Practices and Gap AnalysisThis 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.Bidirectional Forwarding Detection (BFD) Multipoint Active TailsThis document describes active tail extensions to the Bidirectional Forwarding Detection (BFD) protocol for multipoint networks.Acknowledgements
The authors would like to thank , , ,
, , , , , , , and for the comments on this
document. The authors would also like to thank , ,
, , , , , and for their comments and discussion on the documents and , on which the present document is based.
The authors would also like to thank and for their
in-depth review of this document and their very valuable comments and
suggestions.
Authors' AddressesUniversidad Carlos III de MadridAv. Universidad, 30LeganesMadrid28911Spain+34 91624 6236cjbc@it.uc3m.eshttp://www.it.uc3m.es/cjbc/Universidad Carlos III de MadridAv. Universidad, 30LeganesMadrid28911Spain+34 91624 8803aoliva@it.uc3m.eshttp://www.it.uc3m.es/aoliva/Athonet S.r.l.via Ca' del Luogo 6/8Bolzano Vicentino (VI)36050Italyfabio.giust.research@gmail.comSIGFOX425 rue Jean RostandLabege31670Francej.c.zuniga@ieee.orghttp://www.sigfox.com/InterDigital EuropeAlain.Mourad@InterDigital.comhttp://www.InterDigital.com/