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Versions: (draft-bernardos-dmm-pmipv6-dlif)
00 01 02 03 04 05
DMM Working Group CJ. Bernardos
Internet-Draft A. de la Oliva
Intended status: Experimental UC3M
Expires: May 5, 2020 F. Giust
Athonet
JC. Zuniga
SIGFOX
A. Mourad
InterDigital
November 2, 2019
Proxy Mobile IPv6 extensions for Distributed Mobility Management
draft-ietf-dmm-pmipv6-dlif-05
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.
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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 May 5, 2020.
Copyright Notice
Copyright (c) 2019 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 . . . . . . . . . . . . . . . . . . . . 5
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. 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 . . . . . . . . . . . . . . . . . . . 20
4.5. Previous MAAR Option . . . . . . . . . . . . . . . . . . 22
4.6. Serving MAAR Option . . . . . . . . . . . . . . . . . . . 23
4.7. DLIF Link-local Address Option . . . . . . . . . . . . . 23
4.8. DLIF Link-layer Address Option . . . . . . . . . . . . . 24
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
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6. Security Considerations . . . . . . . . . . . . . . . . . . . 25
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1. Normative References . . . . . . . . . . . . . . . . . . 26
8.2. Informative References . . . . . . . . . . . . . . . . . 27
Appendix A. Comparison with Requirement document . . . . . . . . 28
A.1. Distributed mobility management . . . . . . . . . . . . . 28
A.2. Bypassable network-layer mobility support for each
application session . . . . . . . . . . . . . . . . . . . 28
A.3. IPv6 deployment . . . . . . . . . . . . . . . . . . . . . 29
A.4. Existing mobility protocols . . . . . . . . . . . . . . . 29
A.5. Coexistence with deployed networks/hosts and operability
across different networks . . . . . . . . . . . . . . . . 29
A.6. Operation and management considerations . . . . . . . . . 30
A.7. Security considerations . . . . . . . . . . . . . . . . . 30
A.8. Multicast considerations . . . . . . . . . . . . . . . . 30
Appendix B. Implementation experience . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
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).
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, in our proposal, 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
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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
assigned by the MAAR to the MNs attached to it, and they are routable
at that MAAR.
We consider partially distributed schemes, where the data plane only
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 used in this document are defined in the DMM
Deployment Models and Architectural Considerations document
[I-D.ietf-dmm-deployment-models]:
Home Control-Plane Anchor (Home-CPA)
Home Data Plane Anchor (Home-DPA)
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Access Control Plane Node (Access-CPN)
Access Data Plane Node (Access-DPN)
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.
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.
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 Central Mobility Database (CMD), which is
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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, see Appendix B for further details.
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 Central Mobility Database (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 messages 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.
This solution can be categorized under Model-1: Split Home Anchor
Mode in [I-D.ietf-dmm-deployment-models]. As another note, 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.
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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 an IPv6 global 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 permanent
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).
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.
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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:
1. When the MN moves from its current point of attachment and
attaches to MAAR2 (now the S-MAAR), MAAR2 reserves another IPv6
prefix (Pref2), it stores a temporary BCE, and it sends a plain
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
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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 (see
Appendix B for further details). 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.
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+-----+ +---+ +-----+ +--+ +--+
|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 as current P-CoA (i.e., the MAAR
prior to handover) and 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. When aggregating and relaying PBAs,
the CMD SHOULD make use of the timeout also to deal with missing PBAs
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(to retransmit PBUs). The INITIAL_BINDACK_TIMEOUT [RFC6275] SHOULD
be used for configuring the retransmission timer.
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 MAY 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 P-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.
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+-----+ +---+ +-----+ +--+ +--+
|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.
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+-----+ +---+ +-----+ +--+ +--+
|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, when 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 session 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
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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. 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 that allows to easily hide the change of
associated anchors from the mobile node.
+---------------------------------------------------+
( 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
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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 (e.g., 00:11:22:33:01:01) and IPv6 addresses (e.g.,
prefA::MAAR1/64 and fe80:211:22ff:fe33:101/64) 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 exactly
resemble the 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).
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+------------------------------------------+ +----------------------+
| MAAR1 | | MAAR2 |
|+----------------------------------------+| |+--------------------+|
||+------------------++------------------+|| ||+------------------+||
|||+-------++-------+||+-------++-------+||| |||+-------++-------+|||
||||mn3mar1||mn3mar2||||mn2mar1||mn2mar2|||| ||||mn1mar1||mn1mar2||||
|||| LMAC1 || LMAC2 |||| LMAC3 || LMAC4 |||| |||| LMAC5 || LMAC6 ||||
|||+-------++-------+||+-------++-------+||| |||+-------++-------+|||
||| LIFs of MN3 || LIFs of MN2 ||| ||| LIFs of MN1 |||
||+------------------++------------------+|| ||+------------------+||
|| HMAC1 (phy if MAAR1) || ||HMAC2 (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. MN1, MN2 and MN3 have two
P-MAARs: MAAR1 and MAAR2. 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 introduced before, each MN always "sees" multiple logical routers
-- one per P-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,
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 (HMAC2) 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
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by the serving MAAR (MAAR2) configuring an additional distributed
logical interface: mn1mar1, which behaves exactly 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 (which will be no longer 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
(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.
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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 Mobility Anchor and
Access Router 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| Reser | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MAAR Flag (D)
The D Flag is set to indicate to the receiver of the message that
the Proxy Binding Update is from a MAAR. 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
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.
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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 Mobility Anchor and
Access Router. 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 .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MAAR (D)
The D is set to indicate that the sender of the message supports
operating as a Mobility Anchor and Access Router. 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
the mobile node's prefix anchored at the anchoring MAAR. There can
be multiple Anchored Prefix options present in the message.
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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 of the IPv6
prefix contained in the option.
Anchored Prefix
A sixteen-byte field containing the mobile node's IPv6 Anchored
Prefix. Only the first Prefix Length bytes are valid for the
Anchored Prefix. The rest of the bytes MUST be ignored.
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. Therefore, this option can only appear if the D bit is set in
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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 of the IPv6
prefix contained in the option.
Local Prefix
A sixteen-byte field containing the IPv6 Local Prefix. Only the
first Prefix Length bytes are valid for the IPv6 Local Prefix.
The rest of the bytes MUST be ignored.
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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:
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 | 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 33.
Prefix Length
8-bit unsigned integer indicating the prefix length of the IPv6
prefix contained in the option.
Previous MAAR's address
A sixteen-byte field containing the P-MAAR's IPv6 global address.
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Home Network Prefix
A sixteen-byte field containing the mobile node's IPv6 Home
Network Prefix. Only the first Prefix Length bytes are valid for
the mobile node's IPv6 Home Network Prefix. The rest of the bytes
MUST be ignored.
4.6. Serving MAAR Option
This new option is defined for use with the Proxy Binding Update and
Proxy Binding Acknowledgement messages 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:
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.
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-byte 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 Update and Proxy Binding Acknowledgment messages
exchanged between MAARs. This option is used for exchanging the
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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
A sixteen-byte 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 Update and Proxy Binding Acknowledgment messages
exchanged between MAARs. 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].
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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 byte 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.
5. IANA Considerations
This document defines six new mobility options that need to be
registered in the Mobility Options registry on the Mobile IPv6
parameters registry. The required IANA actions are marked as IANA-1
to IANA-6.
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
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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 exist. In this situation, the CMD creates k
outgoing packets from a single incoming packet. This bears a certain
amplification risk. The CMD SHOULD use a pacing approach to limit
this amplification risk.
When the CMD acts as MAAR locator, mobility signaling (PBAs) is
exchanged between P-MAARs and current S-MAAR. This requires security
associations 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.
7. Acknowledgments
The authors would like to thank Dirk von Hugo, John Kaippallimalil,
Ines Robles and Joerg Ott 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,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
November 2005, <https://www.rfc-editor.org/info/rfc4191>.
[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,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
RFC 5213, DOI 10.17487/RFC5213, August 2008,
<https://www.rfc-editor.org/info/rfc5213>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <https://www.rfc-editor.org/info/rfc6275>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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.
[I-D.ietf-dmm-deployment-models]
Gundavelli, S. and S. Jeon, "DMM Deployment Models and
Architectural Considerations", draft-ietf-dmm-deployment-
models-04 (work in progress), May 2018.
[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,
<https://www.rfc-editor.org/info/rfc7333>.
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[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,
<https://www.rfc-editor.org/info/rfc7429>.
[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,
<https://www.rfc-editor.org/info/rfc8563>.
Appendix A. Comparison with Requirement document
In this section we describe how our solution addresses the DMM
requirements listed in [RFC7333].
A.1. Distributed mobility management
"IP mobility, network access solutions, and forwarding solutions
provided by DMM MUST enable traffic to avoid traversing a single
mobility anchor far from the optimal route."
In our solution, a MAAR is responsible to handle the mobility for
those IP flows started when the MN is attached to it. As long as the
MN remains connected to the MAAR's access links, the IP packets of
such flows can benefit from the optimal path. When the MN moves to
another MAAR, the path becomes non-optimal for ongoing flows, as they
are anchored to the previous MAAR, but newly started IP sessions are
forwarded by the new MAAR through the optimal path.
A.2. Bypassable network-layer mobility support for each application
session
"DMM solutions MUST enable network-layer mobility, but it MUST be
possible for any individual active application session (flow) to not
use it. Mobility support is needed, for example, when a mobile host
moves and an application cannot cope with a change in the IP address.
Mobility support is also needed when a mobile router changes its IP
address as it moves together with a host and, in the presence of
ingress filtering, an application in the host is interrupted.
However, mobility support at the network layer is not always needed;
a mobile node can often be stationary, and mobility support can also
be provided at other layers. It is then not always necessary to
maintain a stable IP address or prefix for an active application
session."
Our DMM solution operates at the IP layer, hence upper layers are
totally transparent to the mobility operations. In particular,
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ongoing IP sessions are not disrupted after a change of access
network. The routability of the old address is ensured by the IP
tunnel with the old MAAR. New IP sessions are started with the new
address. From the application's perspective, those processes which
sockets are bound to a unique IP address do not suffer any impact.
For the other applications, the sockets bound to the old address are
preserved, whereas next sockets use the new address.
A.3. IPv6 deployment
"DMM solutions SHOULD target IPv6 as the primary deployment
environment and SHOULD NOT be tailored specifically to support IPv4,
particularly in situations where private IPv4 addresses and/or NATs
are used."
The DMM solution we propose targets IPv6 only.
A.4. Existing mobility protocols
"A DMM solution MUST first consider reusing and extending IETF
standard protocols before specifying new protocols."
This DMM solution is derived from the operations and messages
specified in [RFC5213].
A.5. Coexistence with deployed networks/hosts and operability across
different networks
"A DMM solution may require loose, tight, or no integration into
existing mobility protocols and host IP stacks. Regardless of the
integration level, DMM implementations MUST be able to coexist with
existing network deployments, end hosts, and routers that may or may
not implement existing mobility protocols. Furthermore, a DMM
solution SHOULD work across different networks, possibly operated as
separate administrative domains, when the needed mobility management
signaling, forwarding, and network access are allowed by the trust
relationship between them"
The partially distributed DMM solution (distributed data plane and
centralized control plane) can be extended to provide a fallback
mechanism to operate as legacy Proxy Mobile IPv6. It is necessary to
instruct MAARs to always establish a tunnel with the same MAAR,
working as LMA. The fully distributed DMM solution (distributed data
and control plane) can be extended as well, but it requires more
intervention. The partially distributed DMM solution can be deployed
across different domains with trust agreements if the CMDs of the
operators are enabled to transfer context from one node to another.
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The fully distributed DMM solution works across multiple domains if
the same signalling scheme is used in both domains.
A.6. Operation and management considerations
"A DMM solution needs to consider configuring a device, monitoring
the current operational state of a device, and responding to events
that impact the device, possibly by modifying the configuration and
storing the data in a format that can be analyzed later.
The proposed solution can re-use existing mechanisms defined for the
operation and management of Proxy Mobile IPv6.
A.7. Security considerations
"A DMM solution MUST support any security protocols and mechanisms
needed to secure the network and to make continuous security
improvements. In addition, with security taken into consideration
early in the design, a DMM solution MUST NOT introduce new security
risks or amplify existing security risks that cannot be mitigated by
existing security protocols and mechanisms."
The proposed solution does not specify a security mechanism, given
that the same mechanism for PMIPv6 can be used.
A.8. Multicast considerations
"DMM SHOULD enable multicast solutions to be developed to avoid
network inefficiency in multicast traffic delivery."
This solution in its current version does not specify any support for
multicast traffic.
Appendix B. Implementation experience
The network-based DMM solution described in section Section 3.4 is
now available at the Open Distributed Mobility Management (ODMM)
project (http://www.odmm.net/), under the name of Mobility Anchors
Distribution for PMIPv6 (MAD-PMIPv6). The ODMM platform is intended
to foster DMM development and deployment, by serving as a framework
to host open source implementations.
The MAD-PMIPv6 code is developed in ANSI C from the existing UMIP
implementation for PMIP. The most relevant changes with respect to
the UMIP original version are related to how to create the CMD and
MAAR's state machines from those of an LMA and a MAG; for this
purpose, part of the LMA code was copied to the MAG, in order to send
PBA messages and parse PBU. Also, the LMA routing functions were
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removed completely, and moved to the MAG, because MAARs need to route
through the tunnels in downlink (as an LMA) and in uplink (as a MAG).
Tunnel management is hence a relevant technical aspect, as multiple
tunnels are established by a single MAAR, which keeps their status
directly into the MN's BCE. Indeed, from the implementation
experience it was chosen to create an ancillary data structure as
field within a BCE: the data structure is called "MAAR list" and
stores the previous MAARs' address and the corresponding prefix(es)
assigned for the MN. Only the CMD and the serving MAAR store this
data structure, because the CMD maintains the global MN's mobility
session formed during the MN's roaming within the domain, and the
serving MAAR needs to know which previous MAARs were visited, the
prefix(es) they assigned and the tunnels established with them.
Conversely, a previous MAAR only needs to know which is the current
Serving MAAR and establish a single tunnel with it. For this reason,
a MAAR that receives a PBU from the CMD (meaning that the MN attached
to another MAAR), first sets up the routing state for the MN's
prefix(es) it is anchoring, then stops the BCE expiry timer and
deletes the MAAR list (if present) since it is no longer useful.
In order to have the MN totally unaware of the changes in the access
link, all MAARs implement the Distributed Logical Interface (DLIF)
concept. Moreover, it should be noted that the protocols designed in
the document work only at the network layer to handle the MNs joining
or leaving the domain. This should guarantee a certain independency
to a particular access technology. The implementation reflects this
reasoning, but we argue that an interaction with lower layers
produces a more effective attachment and detachment detection,
therefore improving the performance, also regarding de-registration
mechanisms.
It was chosen to implement the "proxy" solution because it produces
the shortest handover latency, but a slight modification on the CMD
state machine can produce the first scenario described ("relay")
which guarantees a more consistent request/ack scheme between the
MAARS. By modifying also the MAAR's state machine it can be
implemented the second solution ("locator").
An early MAD-PMIPv6 implementation was shown during a demo session at
the IETF 83rd, in Paris in March 2012. An enhancement version of the
prototype has been presented at the 87th IETF meeting in Berlin, July
2013. The updated demo included a use case scenario employing a CDN
system for video delivery. More, MAD-PMIPv6 has been extensively
used and evaluated within a testbed employing heterogeneous radio
accesses within the framework of the MEDIEVAL EU project. MAD-PMIPv6
software is currently part of a DMM test-bed comprising 3 MAARs, one
CMD, one MN and a CN. All the machines used in the demos were Linux
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UBUNTU 10.04 systems with kernel 2.6.32, but the prototype has been
tested also under newer systems. This testbed was also used by the
iJOIN EU project.
Authors' Addresses
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/
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Alain Mourad
InterDigital Europe
Email: Alain.Mourad@InterDigital.com
URI: http://www.InterDigital.com/
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