Internet DRAFT - draft-bernardos-dmm-cmip
draft-bernardos-dmm-cmip
DMM Working Group CJ. Bernardos
Internet-Draft A. de la Oliva
Intended status: Informational UC3M
Expires: March 12, 2018 F. Giust
NEC
September 8, 2017
An IPv6 Distributed Client Mobility Management approach using existing
mechanisms
draft-bernardos-dmm-cmip-08
Abstract
The use of centralized mobility management approaches -- such as
Mobile IPv6 -- poses some difficulties to operators of current and
future networks, due to the expected large number of mobile users and
their exigent demands. All this has triggered the need for
distributed mobility management alternatives, that alleviate
operators' concerns allowing for cheaper and more efficient network
deployments.
This draft describes a possible way of achieving a distributed
mobility behavior with Client Mobile IP, based on Mobile IPv6 and the
use of Cryptographic Generated Addresses.
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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 http://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 March 12, 2018.
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Copyright Notice
Copyright (c) 2017 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
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Description of the solution . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Comparison with Requirement document . . . . . . . . 11
A.1. Distributed mobility management . . . . . . . . . . . . . 11
A.2. Bypassable network-layer mobility support for each
application session . . . . . . . . . . . . . . 12
A.3. IPv6 deployment . . . . . . . . . . . . . . . . . . . . . 12
A.4. Existing mobility protocols . . . . . . . . . . . . . . . 12
A.5. Coexistence with deployed networks/hosts and operability
across different networks . . . . . . . . . . . . . . . . 13
A.6. Operation and management considerations . . . . . . . . . 13
A.7. Security considerations . . . . . . . . . . . . . . . . . 13
A.8. Multicast . . . . . . . . . . . . . . . . . . . . . . . . 13
Appendix B. Open DMM platform . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
Most of the currently standardized IP mobility solutions, like Mobile
IPv6 [RFC6275], or Proxy Mobile IPv6 [RFC5213] rely to a certain
extent on a centralized mobility anchor entity. This centralized
network node is in charge of both the control of the network entities
involved in the mobility management (i.e., it is a central point for
the control signalling), and the user data forwarding (i.e., it is
also a central point for the user plane). This makes centralized
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mobility solutions prone to several problems and limitations, as
identified in [RFC7333]: 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).
There are basically two main approaches that are being researched
now: one aimed at making Mobile IPv6 work in a distributed way, and
another one doing the same exercise for Proxy Mobile IPv6 (see the
document [RFC7429]). In this draft we describe a solution to achieve
a DMM behavior with a CMIP (MIPv6) solution. This document is based
on a research paper of the same authors, called "Flat Access and
Mobility Architecture: an IPv6 Distributed Client Mobility Management
solution" [GOB11].
2. Terminology
The following terms used in this document are defined in the Mobile
IPv6 specification [RFC6275]:
Home Agent (HA)
Home Link
Home Address (HoA)
Care-of Address (CoA)
Binding Update (BU)
Binding Acknowledgement (BA)
The following terms are defined and used in this document:
DAR (Distributed Anchor Router). First hop routers where the mobile
nodes attach to. They also play the role of mobility managers for
the IPv6 addresses they anchor.
HDAR (Home Distributed Anchor Router). DAR which plays the role of
Home Agent for a particular IPv6 address (i.e., DAR where that
IPv6 address is anchored).
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3. Description of the solution
Distributed Mobility Management approaches try to overcome the
limitations of the traditional centralized mobility management, i.e.,
Mobile IP, by bringing the mobility anchor closer to the MN.
Following this idea, in our approach -- that we call Flat Access and
Mobility Architecture (FAMA) -- the MIPv6 centralized home agent 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 access routers
Distributed Anchor Routers (DARs).
The diagram in Figure 1 depicts the operations of the proposed
solution. When a mobile node attaches to a distributed anchor
router, it gets an IPv6 address which is topologically anchored at
the DAR (Pref1::addr1 - HoA1). In the scheme we assume the address
configuration takes place through a Router Solicitation/Router
Advertisement handshake. While attached to this DAR, the mobile can
send and receive traffic using HoA1 without traversing any tunneling
nor special packet handling.
If the the mobile node moves to a different DAR, it gets a new IPv6
address from the new access router (Pref2::addr2 - HoA2). In case
the MN wants to keep the reachability of the IPv6 address(es) it
obtained from the previous DAR (note that this decision is dynamic
and it is out of scope of this document, it can be done on an
application basis for example), the host has to involve its MIPv6
stack, by sending a Binding Update to the DAR where the IPv6 address
is anchored, using the address obtained from the current DAR as care-
of address (in our example the MN binds HoA2 as CoA to DAR1).
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+-----+ +-----+ +-----+ +-----+ +-----+
| MN | |DAR1 | |DAR2 | | CN1 | | CN2 |
+-----+ +-----+ +-----+ +-----+ +-----+
| | | | |
|-Rtr. Sol.->| | | |
|<-Rtr. Adv.-| | | |
| | | | |
Pref1::addr1 | | | |
conf. (HoA1) | | | |
| | | | |
|<-----------+--IP flow 1------------->| |
| | | | |
- o - o - o - o - o Handover to DAR2 o - o - o - o - o - o -
| | | | |
|--------Rtr. Sol.------->| | |
|<-------Rtr. Adv.--------| | |
Pref2::addr2 | | | |
conf. (HoA2) | | | |
|----BU----->| | | |
| (CoA=HoA2) | | | |
|<---BA------| | | |
|(-tnl est.-)| | | |
| | | | |
|(<---------)+--IP flow 1------------->| |
| | | | |
|<--------------IP flow 2-+------------------------>|
| | | | |
Figure 1: Signalling after the first handover
In this way, the IPv6 address that the node wants to maintain in use
(Pref1::addr1) plays the role of home address (HoA1), and the DAR
from where that address was configured plays the role of Home Agent
(for that particular address). In this scenario, old flows are
anchored to the previous DAR (DAR1), which is in charge to
encaspulate the packets and deliver them to the MN's CoA. The IP
tunnel is bi-directional, so the MN does the same when sending
packets with the old address (HoA1). Conversely, new IP flows are
started using the address configured at the new DAR (HoA2). These
flows are handled by the new DAR as a plain IPv6 router.
Note that the FAMA approach basically enables a mobile node to
simultaneously handle several IPv6 addresses -- each of them anchored
at a different DAR -- ensuring their continuous reachability by using
Mobile IPv6 in a distributed fashion (i.e., each access router is a
potential home agent for the address it delegates, if required).
Figure 2 illustrates the above case in which the MN is connected to
DAR2, but flow1 is anchored at DAR1, because it was started by the MN
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using the IPv6 address Pref1::addr1, configured when the MN was
connected to DAR1. In the same example, the MN starts flow2 using
Pref2::addr2, assigned by DAR2.
+---+ +---+
|CN1| |CN2|
+*--+ +*--+
* *
* *
***** *
flow1 * * flow2
* *
* *
* *
+---*-+ +----*+ +-----+
| * | ___ | *| | |
|DAR1**(__*\-+DAR2*+-----+DAR3 |
| | \*\| *| | |
+-----+ \*\----*+ +-----+
\*\ *
\*\ *
flow1 using \*--*+ flow2 using
Pref1::addr1 |* *| Pref2::addr2
|*MN*|
+----+
Operations sequence Packets flow
Figure 2: MN's flows forwarding in FAMA
The same operations take place if the MN moves to another DAR. The
MN obtains a new address (Pref3::addr3 - HoA3), which is indicated as
CoA in the BU messages sent by the MN to the previous DARs. This
distributed address anchoring is enabled on demand and on a per-
address granularity, which means that depending on the user needs, it
might be the case that all, some or none of the IPv6 addresses that a
mobile node configures while moving within a FAMA domain, are kept
reachable and used by the mobile. The scheme in Figure 3 depicts the
example where the MN updates all the previous DARs, mapping the
corresponding HoA with the new CoA
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+-----+ +-----+ +-----+ +-----+ +-----+
| MN | |DAR1 | |DAR2 | |DAR3 | | CNs |
+-----+ +-----+ +-----+ +-----+ +-----+
| | | | |
(<-----------)--IP flow 1-------------------------->|
| | | | |
|<--------------IP flow 2-+------------------------>|
| | | | |
- o - o - o - o - o Handover to DAR2 o - o - o - o - o - o -
| | | | |
|--------------Rtr. Sol.-------------->| |
|<-------------Rtr. Adv.---------------| |
Pref3::addr3 | | | |
conf. (HoA3) | | | |
|----BU----->| | | |
| (CoA=HoA) | | | |
|<---BA------| | | |
|(-tnl est.-)| | | |
|------------BU---------->| | |
| (CoA=HoA3) | | |
|<-----------BA-----------| | |
|(---------tnl est.------)| | |
| | | | |
|(<---------)+-IP flow 1--------------------------->|
| | | | |
|(<------------IP flow 2-)+------------------------>|
| | | | |
|<-------------IP flow 3---------------+----------->|
| | | | |
Figure 3: Signalling after a second handover
In traditional Mobile IPv6, the communication between the MN and the
HA is secured through IPsec [RFC4877]. Following a similar approach
in FAMA is difficult due to the large number of security associations
that would be required, since any gateway of the access network can
play the role of home agent for any mobile node. In order to
overcome this problem and provide authentication between the DAR and
the MNs, we propose the use of Cryptographically Generated Addresses
[RFC3972] (CGAs), as introduced in [I-D.laganier-mext-cga]. CGAs are
a powerful mechanism allowing authentication of the packets and
requires no public-key infrastructure, hence it is well-suited for
this application.
Following the ideas presented above, every time an MN attaches to a
DAR, it configures a CGA from a prefix anchored at the DAR (e.g., by
using stateless address auto-configuration mechanisms). This address
can then be used by the MN to establish a communication with a remote
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Correspondent Node (CN) while attached to that particular DAR. If
the mobile then moves to a new DAR (nDAR), the following two cases
are possible: i) there is no need for the address that was configured
at the previous DAR (pDAR) to survive the movement: in this case
there is no further action required; ii) the mobile wants to keep the
reachability of the address configured at pDAR: in this case Mobile
IPv6 is triggered, and the MN sends a Binding Update (BU) message to
the pDAR, using the address configured at the previous DAR as home
address, and the address configured at the new DAR as care-of
address. This BU includes the CGA parameters and signature
[I-D.laganier-mext-cga], which are used by the receiving DAR to
identify the MN as the legitimate owner of the address. Although the
use of CGAs does not impose a heavy burden in terms of performance,
depending on the number of MNs handled at the DAR, the processing of
the CGAs can be problematic. To reduce the complexity of the
proposed protocol, we suggest an alternative mechanism to
authenticate any subsequent signaling packets exchanged between the
MN and the DAR (in case the mobile performs a new attachment to a
different DAR). This alternative method relies on the use of a
Permanent Home Keygen Token (PHKT), which will be used to generate
the Authorization option that the MN has to include in all next
Binding Update messages. This token is forwarded to the MN in the
Binding Acknowledgment message, sent on reply to the BU. The
procedure is depicted in Figure 4. Once the signaling procedure is
completed, a bi-directional tunnel is established between the mobile
node and the DAR where the IPv6 address is anchored (the "home" DAR
-- HDAR -- for that particular address), so the mobile can continue
using the IPv6 address.
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------ -------
| MN | | DAR |
------ -------
| |
CGA | |
config |-- BU + CGA param + signature ------>|
| | MN
PHKT |<----------------------- BA + PHKT --| auth
caching | |
| |
(first handoff)
PHKT | |
refresh,| |
next |-- BU(PHKT auth) ------------------->|
handoffs,| | MN
de-reg |<------------------------------ BA --| auth
| |
| |
(subsequent signaling)
Figure 4: Signaling between the MN and the DAR
In case the MN performs any subsequent movements and it requires to
maintain the reachability of an address for which it has already sent
a BU, the following BU messages can be secured using the PHKT
exchanged before, reducing the computational load at the receiving
DAR.
Note that on every attachment of a node to a DAR, the terminal also
obtains a new IPv6 address which is topologically anchored at that
DAR, and that this address can be used for new communications
(avoiding in this way the tunneling required when using an address
anchored at a different DAR). A mobile can keep multiple IPv6
addresses active and reachable at a given time, and that requires to
send -- every time the MN moves -- a BU message to all the previous
DARs that are anchoring the IP flows that the MN wish to maintain.
4. IANA Considerations
TBD.
5. Security Considerations
Although the approach documented in this document is attractive for
the reduced signaling overhead caused by the mobility support, it can
be misused in some particular scenarios by malicious nodes that wish
to export an incorrect CoA in the BU message, since it does provide
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proof of the MN's reachability at the visited network. Indeed, the
CGA approach assures that the BU message has been sent by the
legitimate HoA's owner but it does not make sure that same MN to be
reachable at the CoA indicated. This requires further analysis.
A possible approach to provide a more secure solution is the
following: a Return Routability procedure similar to the one defined
in MIPv6 Route Optimization can be used to mitigate the
aforementioned security issue. The Return Routability procedure
starts after the handoff. Instead of sending the BU message, the MN
sends a Care-of Test Init message (CoTI). This message is replied by
the DAR with a Care-Of Test message containing a CoA Keygen Token.
The MN can now send a BU using both Home and CoA Keygen tokens to
proof its reachability at both the HoA and the CoA. The message and
the knowledge of both tokens is a proof that the MN is the legitimate
node who has sent the BU and also is reachable at the CoA indicated.
As all security improvements, the one proposed incurs in a
performance penalty, in this case an increase in the handover delay.
Specifically this enhanced security approach requires four messages
to be exchanged between the MN and the DAR instead of the two
messages of the original solution. In terms of handover delay, it
increases it by a factor of two, as the new solution requires to two
Round Trip Times (RTTs) to conclude, instead of one.
6. References
6.1. 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>.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>.
[RFC4877] Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with
IKEv2 and the Revised IPsec Architecture", RFC 4877,
DOI 10.17487/RFC4877, April 2007, <https://www.rfc-
editor.org/info/rfc4877>.
[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>.
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[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>.
6.2. Informative References
[GOB11] Giust, F., de la Oliva, A., and CJ. Bernardos, "Flat
Access and Mobility Architecture: an IPv6 Distributed
Client Mobility Management solution", 3rd IEEE
International Workshop on Mobility Management in the
Networks of the Future World (MobiWorld 2011), colocated
with IEEE INFOCOM 2011 , 2011.
[I-D.laganier-mext-cga]
Laganier, J., "Authorizing Mobile IPv6 Binding Update with
Cryptographically Generated Addresses", draft-laganier-
mext-cga-01 (work in progress), October 2010.
[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 DAR 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 DAR's access links, the IP packets of
such flows can benefit from the optimal path. When the MN moves to
another DAR, the path becomes non-optimal for ongoing flows, as they
are anchored to the previous DAR, but newly started IP sessions are
forwarded by the new DAR 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 DAR. 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 [RFC6275], [RFC3972], and [I-D.laganier-mext-cga].
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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 proposed solution can provide a fallback mechanism employing
legacy Mobile IPv6, for instance forcing the MN to use only one DAR.
Moreover, this solution applies when the MN is connected to an
administrative domain not supporting trust relationships. Indeed,
all the IP sessions can remain anchored to the DARs of the "home"
domain. Our solution can be deployed across different domains with
trust agreements.
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 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 uses a CGA-based security system to enable
authentication and authorization of mobile hosts.
A.8. Multicast
"DMM SHOULD enable multicast solutions to be developed to avoid
network inefficiency in multicast traffic delivery."
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This solution does not include multicast traffic in its scope.
Nevertheless, it allows combining multicast support solutions, such
as local subscription at each DAR, which would result in a flexible
distribution scenario.
Appendix B. Open DMM platform
The client-based DMM solution described in this document is available
at the Open Distributed Mobility Management (ODMM) project
(http://www.odmm.net/). The ODMM platform is intended to foster DMM
development and deployment, by serving as a framework to host open
source implementations.
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
NEC Laboratories Europe
NEC Europe Ltd.
Kurfuersten-Anlage 36
Heidelberg D-69115
Germany
Phone: +49 6221 4342216
Email: fabio.giust@neclab.eu
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