Internet DRAFT - draft-bernardos-dmm-pmipv6-dlif
draft-bernardos-dmm-pmipv6-dlif
DMM Working Group CJ. Bernardos
Internet-Draft A. de la Oliva
Intended status: Standards Track UC3M
Expires: September 3, 2018 F. Giust
NEC
JC. Zuniga
SIGFOX
A. Mourad
InterDigital
March 2, 2018
Proxy Mobile IPv6 extensions for Distributed Mobility Management
draft-bernardos-dmm-pmipv6-dlif-01
Abstract
Distributed 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
mobility anchor and access router). The mobility anchor and access
router 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 document focuses on the required extensions to
effectively support simultaneously anchoring several flows at
different distributed gateways.
This document introduces the concept of distributed logical
interface, which is a software construct that allows to easily hide
the change of anchor from the mobile node.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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Status of This Memo
This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on September 3, 2018.
Copyright Notice
Copyright (c) 2018 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. PMIPv6 DMM extenstions . . . . . . . . . . . . . . . . . . . 5
3.1. Initial registration . . . . . . . . . . . . . . . . . . 7
3.2. The CMD as PBU/PBA relay . . . . . . . . . . . . . . . . 8
3.3. The CMD as MAAR locator . . . . . . . . . . . . . . . . . 10
3.4. The CMD as MAAR proxy . . . . . . . . . . . . . . . . . . 11
3.5. De-registration . . . . . . . . . . . . . . . . . . . . . 12
3.6. The Distributed Logical Interface (DLIF) concept . . . . 12
3.7. Message Format . . . . . . . . . . . . . . . . . . . . . 16
3.7.1. Proxy Binding Update . . . . . . . . . . . . . . . . 16
3.7.2. Proxy Binding Acknowledgment . . . . . . . . . . . . 17
3.7.3. Anchored Prefix Option . . . . . . . . . . . . . . . 17
3.7.4. Local Prefix Option . . . . . . . . . . . . . . . . . 18
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3.7.5. Previous MAAR Option . . . . . . . . . . . . . . . . 19
3.7.6. Serving MAAR Option . . . . . . . . . . . . . . . . . 21
3.7.7. DLIF Link-local Address Option . . . . . . . . . . . 21
3.7.8. DLIF Link-layer Address Option . . . . . . . . . . . 22
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
5. Security Considerations . . . . . . . . . . . . . . . . . . . 23
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.1. Normative References . . . . . . . . . . . . . . . . . . 24
7.2. Informative References . . . . . . . . . . . . . . . . . 24
Appendix A. Comparison with Requirement document . . . . . . . . 25
A.1. Distributed mobility management . . . . . . . . . . . . . 25
A.2. Bypassable network-layer mobility support for each
application session . . . . . . . . . . . . . . . . . . . 26
A.3. IPv6 deployment . . . . . . . . . . . . . . . . . . . . . 26
A.4. Existing mobility protocols . . . . . . . . . . . . . . . 26
A.5. Coexistence with deployed networks/hosts and operability
across different networks . . . . . . . . . . . . . . . . 27
A.6. Operation and management considerations . . . . . . . . . 27
A.7. Security considerations . . . . . . . . . . . . . . . . . 27
A.8. Multicast . . . . . . . . . . . . . . . . . . . . . . . . 28
Appendix B. Implementation experience . . . . . . . . . . . . . 28
Appendix C. Applicability to the fog environment . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
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 [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, 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 on 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
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[RFC7333] [RFC7429]; the main concept behind DMM solutions is indeed
bringing the mobility anchor closer to the 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 connectivity to a set of
MNs are also the mobility managers for those MNs. In the following,
we will call these entities Mobility Anchor and Access Routers
(MAARs).
This document focuses on network-based DMM, hence the starting point
is making PMIPv6 working 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 also changes 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]:
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Home Control-Plane Anchor (H-CPA)
Home Data Plane Anchor (Home-DPA)
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). Node that stores the BCEs allocated
for the MNs in the mobility domain. It plays the role of Home-
CPA.
P-MAAR (Previous MAAR). MAAR which was previously visited by the MN
and is still involved in an active flow using an IPv6 prefix it
has advertised to the MN (i.e., MAAR where that IPv6 prefix is
anchored). There might be multiple P-MAARs for an MN's mobility
session. It plays the role of Home-DPA.
S-MAAR (Serving MAAR). 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
mobile node, the serving MAAR has a DLIF configured (associated to
the anchoring MAAR). In this way, a serving MAAR exposes itself
towards each MN as multiple routers, one per active anchoring
MAAR.
3. PMIPv6 DMM extenstions
The solution consists in de-coupling the entities that participates
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 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:
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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
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 have to be extended to include information
regarding previous 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 on 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 on the
status of the network. 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 to update 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
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to switch to the locally anchored prefix to gain route optimization,
as indicated in [I-D.ietf-dmm-ondemand-mobility].
3.1. Initial registration
Upon the MN's attachment to a MAAR, say MAAR1, if the MN is
authorized for the service, an IPv6 global prefix belonging to the
MAAR's prefix pool is reserved for it (Pref1) into a temporal Binding
Cache Entry (BCE) allocated locally. The prefix is sent in a
[RFC5213] PBU with the MN's Identifier (MN-ID) to the CMD, which,
since the session is new, stores a permanent BCE containing as main
fields the MN-ID, the MN's prefix and MAAR1's address as Proxy-CoA.
The CMD replies to MAAR1 with a PBA including the usual options
defined in PMIP/RFC5213, meaning that the MN's registration is fresh
and no past status is available. MAAR1 definitely stores the
temporal BCE previously allocated and unicasts a Router Advertisement
(RA) to the MN including the prefix reserved before, that can be used
by the MN to configure an IPv6 address (e.g., with stateless auto-
configuration). The address is routable at the MAAR, in the sense
that it is on the path of packets addressed to the MN. Moreover, the
MAAR acts as plain router for those packets, as no encapsulation nor
special handling takes place. Figure 1 illustrates this scenario.
+-----+ +---+ +--+
|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
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3.2. The CMD as PBU/PBA relay
When the MN moves from its current access and associates to MAAR2
(now the S-MAAR), MAAR2 reserves another IPv6 prefix (Pref2), it
stores a temporal BCE, and it sends a plain PBU to the CMD for
registration. Upon PBU reception and BC lookup, the CMD retrieves an
already existing entry for the MN, binding the MN-ID to its former
location; thus, the CMD forwards the PBU to the MAAR indicated as
Proxy CoA (MAAR1), including a new mobility option to communicate the
S-MAAR's global address to MAAR1, defined as Serving MAAR Option in
Section 3.7.6. 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, containing the prefix
anchored at MAAR1 in the Home Network Prefix option. 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 send 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 3.7.5), 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.
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. The procedure is depicted in Figure 2.
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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 next MN's movements the process is repeated except for the number
of P-MAARs involved, that rises 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.
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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 reflect 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 OS 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. In Figure 3 is illustrated the new messages sequence, while
the data forwarding is unaltered.
+-----+ +---+ +-----+ +--+ +--+
|MAAR1| |CMD| |MAAR2| |CN| |CN|
+-----+ +---+ +-----+ +*-+ +*-+
| | | * *
| | MN * +---+ *
| | attach. ***** _|CMD|_ *
| | det. flow1 * / +-+-+ \ *flow2
| |<-- PBU ---| * / | \ *
| BCE | * / | *******
| check+ | * / | * \
| update | +---*-+-? +--+-*+ `+-----+
|<-- PBU*---| | | * | | *| | |
route | | |MAAR1|______|MAAR2+-----+MAAR3|
update | | | **(______)** *| | |
|--------- PBA -------->| +-----+ +-*--*+ +-----+
|--- PBA*-->| route * *
| BCE update Pref1 * *Pref2
| update | +*--*+
| | | ---move-->|*MN*|
| | | +----+
Operations sequence Data Packets flow
PBU/PBA Messages with * contain
a new mobility option
Figure 3: Scenario after a handover, CMD as locator
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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 possess 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 are
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.
+-----+ +---+ +-----+ +--+ +--+
|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
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3.5. De-registration
The de-registration mechanism devised for PMIPv6 is no longer valid
in the Partial DMM architecture. This is motivated by the fact 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 an old 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
Serving MAAR is allowed to de-register the mobility session,
arguing that the MN left definitely 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, send back a PBA with a non-zero lifetime, hence re-
newing the session, if the MN is still connected to the domain.
The evaluation of these methods is left for future work.
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 on the preference
of the mobile selecting the source IPv6 address for a new
communication, without requiring special support on the mobile node
stack. This document defines the Distributed Logical Interface
(DLIF), which is a software construct that allows to easily hide the
change of anchor from the mobile node.
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+---------------------------------------------------+
( 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 active anchoring
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
active anchoring MAAR associated to the MN. Let's consider the
example shown in Figure 5, MN1 initially attaches to MAAR1,
configuring an IPv6 address (prefA::MN1) from a prefix locally
anchored at MAAR1 (prefA::/64). At this stage, MAAR1 plays both the
role of anchoring and serving MAAR, and also it 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
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
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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 active anchoring 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 active anchoring MAARs involved. In order to
maintain the prefix anchored at MAAR1 reachable, a tunnel between
MAAR1 and MAAR2 is established and the routing is modified
accordingly. The PBU/PBA signaling is used to set-up the bi-
directional tunnel between MAAR1 and MAAR2, and it might also be used
to convey to MAAR2 the information about the prefix(es) anchored at
MAAR1 and about the addresses of the associated DLIF (i.e., mn1mar1).
+------------------------------------------+ +----------------------+
| MAAR1 | | MAAR2 |
|+----------------------------------------+| |+--------------------+|
||+------------------++------------------+|| ||+------------------+||
|||+-------++-------+||+-------++-------+||| |||+-------++-------+|||
||||mn3mar1||mn3mar2||||mn2mar1||mn2mar2|||| ||||mn1mar1||mn1mar2||||
|||| LMAC1 || LMAC2 |||| LMAC3 || LMAC4 |||| |||| LMAC5 || LMAC6 ||||
|||+-------++-------+||+-------++-------+||| |||+-------++-------+|||
||| LIFs of MN3 || LIFs of MN2 ||| ||| LIFs of MN1 |||
||+------------------++------------------+|| ||+------------------+||
|| 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
active anchoring 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 active anchoring MAAR -- independently of to which serving
MAAR the MN is currently attached. From the point of view of the MN,
these MAARs are portrayed as different routers, although the MN is
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physically attached to one single interface . The way this is
achieved is by the serving MAAR configuring different logical
interfaces. If we focus 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 (mn1dgw2) 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 mn1dgw2
interface, MAAR2 advertises its locally anchored prefix prefB::/64.
Before attaching to MAAR2, MN1 visited MAAR1, configuring also an
address locally anchored at this MAAR, which is still being used by
the MN1 in active communications. MN1 keeps "seeing" an interface
connecting to MAAR1, as if it were directly connected to the two
MAARs. This is achieved by the serving MAAR (MAAR1) configuring an
additional distributed logical interface: mn1dgw1, which behaves
exactly as the logical interface configured by the actual 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 prefix lifetime. The goal is to
deprecate the prefixes delegated by these MAARs (which will be no
longer serving the MN). Note that on-going communications keep on
using those addresses, even if they are deprecated, so this only
affects to 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 LIPA scenario currently being
consider by 3GPP. 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
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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 of
the local network connected to MAAR1 will survive, being the traffic
forwarded 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.
3.7. Message Format
This section defines extensions to the Proxy Mobile IPv6 [RFC5213]
protocol messages.
3.7.1. 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|D| Reserved | 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.
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
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[RFC6275]. The MAAR MUST ignore and skip any options that it does
not understand.
3.7.2. Proxy Binding Acknowledgment
A new flag (D) is included in the Proxy Binding Acknowledgment to
indicate that the sender supports operating as a distributed gateway.
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|D| Reser |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MAAR (D)
The D is set to indicate that the sender of the message supports
operating as a distributed gateway.
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.
3.7.3. Anchored Prefix Option
A new Anchored Prefix option is defined for use with the Proxy
Binding Update and Proxy Binding Acknowledgment messages exchanged
between distributed gateways. 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.
The Anchored Prefix Option has an alignment requirement of 8n+4. Its
format is as follows:
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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 | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Anchored Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
To be assigned by IANA.
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.
3.7.4. 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. 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.
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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
To be assigned by IANA.
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.
3.7.5. 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:
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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 | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ P-MAAR's address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Home Network Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
To be assigned by IANA.
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.
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.
Home Network Prefix
A sixteen-byte field containing the mobile node's IPv6 Home
Network Prefix.
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3.7.6. 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
To be assigned by IANA.
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.
3.7.7. 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
link-local address of the DLIF to be configured on the serving MAAR
so it resembles the DLIF configured on the anchoring MAAR.
The DLIF Link-local Address option has an alignment requirement of
8n+6. Its format is as follows:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ DLIF Link-local Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
To be assigned by IANA.
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.
3.7.8. 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 anchoring 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
To be assigned by IANA.
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 serving distributed
gateway.
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.
4. IANA Considerations
This document defines new mobility options that require IANA actions.
TBD.
5. 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.
6. Acknowledgments
The authors would like to thank Marco Liebsch for his 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.
7. References
7.1. 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>.
[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>.
7.2. 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.
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[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-03 (work in progress), November 2017.
[I-D.ietf-dmm-ondemand-mobility]
Yegin, A., Moses, D., Kweon, K., Lee, J., Park, J., and S.
Jeon, "On Demand Mobility Management", draft-ietf-dmm-
ondemand-mobility-13 (work in progress), January 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>.
[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>.
Appendix A. Comparison with Requirement document
In this section we descrbe 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.
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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,
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].
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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 DMM solution 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 DMM solution can be extended as well, but
it requires more intervention. The partially DMM solution can be
deployed across different domains with trust agreements if the CMDs
ot the operators are enabled to transfer context from one node to
another. The fully DMM solution works across multiple domains if
both solution apply the same signalling scheme.
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.
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A.8. Multicast
"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, which is left for study in future versions.
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
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 stop 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
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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
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.
Appendix C. Applicability to the fog environment
Virtualization is invading all domains of the E2E 5G network,
including the access, as a mean to achieve the necessary flexibility
in support of the E2E slicing concept. The ETSI NFV framework is the
cornerstone for making virtualization such a promising technology
that can be matured in time for 5G. Typically, virtualization has
been mostly envisaged in the core network, where sophisticated data
centers and clouds provided the right substrate. And mostly, the
framework focused on virtualizing network functions, so called VNFs
(virtualized network functions), which were somewhat limited to
functions that are delay tolerant, typically from the core and
aggregation transport.
As the community has recently been developing the 5G applications and
their technical requirements, it has become clear that certain
applications would require very low latency which is extremely
challenging and stressing for the network to deliver through a pure
centralized architecture. The need to provide networking, computing,
and storage capabilities closer to the users has therefore emerged,
leading to what is known today as the concept of intelligent edge.
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ETSI has been the first to address this need recently by developing
the framework of mobile edge computing (MEC).
Such an intelligent edge could not be envisaged without
virtualization. Beyond applications, it raises a clear opportunity
for networking functions to execute at the edge benefiting from
inherent low latencies.
Whilst it is appreciated the particular challenge for the intelligent
edge concept in dealing with mobile users, the edge virtualization
substrate has been largely assumed to be fixed or stationary.
Although little developed, the intelligent edge concept is being
extended further to scenarios where for example the edge computing
substrate is on the move, e.g., on-board a car or a train, or that it
is distributed further down the edge, even integrating resources from
different stakeholders, into what is known as the fog. The
challenges and opportunities for such extensions of the intelligent
edge remain an exciting area of future research.
Figure 7 shows a diagram representing the fog virtualization concept.
The fog is composed by virtual resources on top of heterogeneous
resources available at the edge and even further in the RAN and end-
user devices. These resources are therefore owned by different
stakeholders who collaboratively form a single hosting environment
for the VNFs to run. As an example, virtual resources provided to
the fog might be running on eNBs, APs, at micro data centers deployed
in shopping malls, cars, trains, etc. The fog is connected to data
centers deeper into the network architecture (at the edge ir the
core).
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+--------------------------------+ +-------------------+
| ------- -------- -------- | | ---------- |
| | | | | | | | | ---------- | |
| | @UE | | @car | | @eNB | | | ---------- | | |
| ------- -------- -------- | | | Data | | | |
| | | | Center | | - |
| -------- Heterogeneous ------- | | | (DC) |- |
phy | | | computing | | | | ---------- |
infra | |@train| devices | @AP | |==| ---------- |
| -------- forming ------- | | ---------- | |
| the fog | | ---------- | | |
| --------- ------------ | | | Data | | | |
| | | | | | | | Center | | - |
| | @mall | | @localDC | | | | (DC) |- |
| --------- ------------ | | ---------- |
| FOG | | CLOUD |
+--------------------------------+ +-------------------+
<--------- fog and edge ----------------->
<--- edge & central cloud --->
Figure 7: Fog virtualization
In this context, where the "fog" hosts functions and resources, it is
important to enable their mobility. In future versions of this
document we will describe how to apply the solution described here to
the fog environment.
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/
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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
NEC Laboratories Europe
NEC Europe Ltd.
Kurfuersten-Anlage 36
Heidelberg D-69115
Germany
Phone: +49 6221 4342216
Email: fabio.giust@neclab.eu
Juan Carlos Zuniga
SIGFOX
425 rue Jean Rostand
Labege 31670
France
Email: j.c.zuniga@ieee.org
URI: http://www.sigfox.com/
Alain Mourad
InterDigital Europe
Email: Alain.Mourad@InterDigital.com
URI: http://www.InterDigital.com/
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