Network Working Group M. Liebsch
Internet-Draft NEC
Intended status: Informational February 5, 2009
Expires: August 9, 2009
PMIPv6 Localized Routing Problem Statement
draft-liebsch-netext-pmip6-ro-ps-00.txt
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Abstract
Proxy Mobile IPv6 is the IETF standard for network-based localized
mobility management. In Proxy Mobile IPv6, mobile nodes are
topologically anchored at a Local Mobility Anchor, which forwards all
data for registered mobile nodes. The set up and support for
localized routing, which allows forwarding of data packets between
mobile nodes and correspondent nodes directly without traversing an
LMA, is not considered. This document describes the problem space of
localized routing in Proxy Mobile IPv6.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. Problem Statement for Localized Routing in PMIPv6 . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Normative References . . . . . . . . . . . . . . . . . . . 11
6.2. Informative References . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
The IETF has specified Proxy Mobile IPv6 (PMIPv6) [RFC5213] as the
protocol for network-based localized mobility management (NetLMM),
which takes basic operation for registration, de-registration and
handover into account. In scope of the base protocol specification
is the set up and maintenance of a forwarding tunnel between an MN's
Mobility Access Gateway (MAG) and its selected Local Mobility Anchor
(LMA). Data packets will always traverse the MN's MAG and its LMA,
irrespective of the location of the MN's remote communication
endpoint. Even though two communicating MNs might be attached to the
same MAG or to different MAGs of the same local mobility domain,
packets will traverse the MNs' LMA(s).
Objectives of designing a solution for localized routing in PMIPv6
are to specify protocol messages and enable associated protocol
operation between PMIPv6 components to support the set up of a direct
routing path for data packets between the MNs' MAGs without
forwarding these packets through the MNs' LMA(s) and to maintain
localized routing in case one or both MNs handover to a different
MAG. Relevant protocol interfaces may include the interface between
associated MAGs, between a MAG and an LMA as well as between LMAs.
This document analyzes and discusses the problem space of using
always the default route through two communicating mobile nodes'
mobility anchors. Furthermore, the problem space of enabling
localized routing in PMIPv6 is analyzed and described, while
different communication and mobility scenarios are taken into
account.
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2. Conventions and Terminology
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 [RFC2119].
This document uses the terminology of [RFC5213]. The following terms
are used in the context of this problem statement:
o Mobile Node (MN): Mobile Node without IP mobility support, which
is attached to a Mobility Access Gateway (MAG) and registered with
a Local Mobility Anchor (LMA) according to the PMIPv6
specification [RFC5213].
o Correspondent Node (CN): Correspondent Node with or without IP
mobility support. The CN represents the communication peer of an
MN, which is attached to a MAG and registered with an LMA
according to the PMIPv6 specification.
o Localized Routing: Result of signaling to set up routing states on
relevant network entities to allow forwarding of data packets
between an MN and a CN within a single PMIPv6 domain without
traversing the MN's LMA and without traversing the CN's mobility
anchor.
o Localized Routing States: Information for localized routing on
relevant forwarding entities on the optimized data path between an
MN and a CN. Such information includes route entries and may
include further information about the MN and the CN, such as IDs.
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3. Problem Statement for Localized Routing in PMIPv6
The Mobile IPv6 (MIPv6) protocol [RFC3775] has built-in mechanisms
for direct communication between a MN and a CN. Mechanisms for route
optimization in MIPv6 cannot be directly applied in PMIPv6, as MNs do
not take part in mobility management and associated signaling.
Following the architecture of PMIPv6, rather entities of the network
infrastructure are dedicated to perform signaling to set up an
optimized route between an MN and a CN. In case of communication
between two nodes, which are attached to the PMIPv6 network
infrastructure and each node is registered with an LMA, data packets
between these two nodes will always traverse the responsible LMA(s).
At least some deployment would benefit from having such communication
localized, rather than traverse the core network to the LMA(s).
Localized routing is crucial at least for the following two reasons:
First, by limiting the communication to the access nodes, the data
traffic traversing the MAG - LMA path (network) can be reduced. This
is significant considering that the transport network between the
access and the core is often the bottleneck in terms of costs and
performance. And there are performance benefits in terms of delay
and packet loss, especially when the MNs are attached to the same
MAG. Even when the MNs are attached to different MAGs, there could
be benefits in limiting the communication to the access network only,
rather than traversing the transport network to the LMA. Hence,
providing the necessary protocol specification to enable localized
routing in PMIPv6 is necessary.
Several tasks need to be performed by the network infrastructure
components before relevant information for such direct communication
is discovered and associated states for localized routing can be set
up. The following list summarizes some key functions, which need to
be performed by the PMIPv6 enabled network infrastructure to
substitute mobile nodes in setting up an optimized route.
o Detection of the possibility to perform localized routing. This
function includes looking at data packets' source and destination
address.
o Initiation of a procedure, which sets up a localized routing path.
o Discovery of stateful entities (i.e. the LMA(s) and/or the
MAG(s)), which maintain and can provide relevant information
needed to set up a localized routing path. Such information may
include the routable address of an LMA or MAG, where one or both
mobile nodes are connected to and registered with.
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o Control in setting up and maintaining (e.g. during handover) the
localized routing path.
This problem statement focuses on local communication between PMIPv6
managed nodes within a single PMIPv6 domain. The following list
analyzes different use cases, which are limited to the communication
within a single PMIPv6 domain, but they consider the existence of
multiple LMAs. Figure 1 depicts the network of a PMIPv6 domain with
two mobility anchors.
Internet Backbone
: :
+------------------+
| | . . . . . .
+----+ +----+ ^
|LMA1| |LMA2| |
+----+ +----+ |
| | |
| | |PMIPv6
+----+------------------+-+ |domain
| | |
+----+ +----+ |
|MAG1| |MAG2| v
+----+ +----+ . . . .
: : :
+---+ +---+ +---+
|MN | |CN1| |CN2|
+---+ +---+ +---+
Figure 1: Reference architecture for localized routing in PMIPv6
All use cases A assume that both the MN and the CN are registered
with an LMA according to the PMIPv6 protocol. Whereas MAG1 is always
considered as the MN's current pCoA, the CN can be either connected
to the same or a different MAG or LMA as the MN. Accordingly, these
topological difference are denoted as follows:
A[number of MAGs][number of LMAs]
A11: MN and CN (CN1) connect to the same MAG (MAG1) and are
registered with the same LMA (LMA). The common MAG may forward
data packets between the MN and the CN directly without forwarding
any packet to the LMA. According to [RFC5213], such operation
should be enforced by the LMA and signaled in the PBU by means of
the EnableMAGLocalRouting flag.
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A12: MN and CN (CN1) connect to the same MAG (MAG1) and are
registered with different LMAs (LMA1 and LMA2) of the same PMIPv6
domain. The common MAG may forward data packets between the MN
and the CN directly without forwarding any packet to the LMAs.
Even though [RFC5213] indicates that localized routing should be
based on the MAG's policy, potential problems exist in case LMA1
and LMA2 differ in settings of the EnableMAGLocalRouting flag.
A21: The CN (CN2) connects to a different MAG (MAG2) as the MN
(MAG1), but MN and CN are registered with the same LMA (LMA1).
The result of localized routing should be the existence of routing
information at MAG1 and MAG2, which allows direct forwarding of
packets between the MN's MAG1 and the CN's MAG2. As LMA1 is the
common anchor for MN and CN and maintains location information for
both nodes, no major race condition and instability in updating
the states for localized routing is expected.
A22: The CN (CN2) connects to a different MAG (MAG2) and a different
LMA (LMA2) as the MN (MAG1, LMA1) in the same PMIPv6 domain. The
result of localized routing should be the existence of routing
information at MAG1 and MAG2, which allows direct forwarding of
packets between the MN's MAG1 and the CN's MAG2. As the location
information of the CN and the MN is maintained at different LMAs,
both LMAs need to be involved in the procedure to set up localized
routing. In case of a handover of MNs to a different MAG, not
synchronized control of updating the states for localized routing
may result in race conditions, superfluous signaling and packet
loss.
The following list summarizes general problems with setting up and
maintaining localized routing between an MN and a CN within a PMIPv6
domain. In the context of this problem statement, the MN and the CN
are always assumed to be registered at an LMA according to the PMIPv6
protocol [RFC5213].
o MNs do not participate in mobility management, hence cannot
perform binding registration at a CN on their own. Rather
entities in the network infrastructure must take over the role of
MNs to set up and maintain an optimized route. Accordingly, a
solution for localized routing in PMIPv6 must specify protocol
operation between relevant network components, such as between a
MAG and an LMA, to enable localized routing for data traffic
without traversing the MNs' LMA(s)
o In case the MN and the CN are both registered with different LMAs
according to the PMIPv6 protocol, relevant information for the set
up of a localized routing path, such as the current MAGs of the MN
and the CN, is distributed between these LMAs. This may
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complicate the set up and stable maintenance of states enabling
localized routing.
o In case localized routing between an MN and a CN has been
successfully set up and both nodes move and attach to a new access
router simultaneously, signaling the new location and maintenance
of states for localized routing at relevant routers may run into a
race condition situation. This can happen in case coordination of
signaling for localized routing and provisioning of relevant state
information is distributed between different network entities,
e.g. different LMAs.
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4. Security Considerations
Since network entities rather than MNs and CNs perform signaling to
set up localized routing, the MIPv6 return routability test [RFC3775]
is not suitable to authenticate associated signaling messages in
PMIPv6. Solutions for localized routing in PMIPv6 need to mitigate
or to provide sufficient defense against possible security threats.
When PMIPv6 participants are administered within the same domain,
infrastructure-based authorization mechanisms, such as IPsec, may be
usable to protect signaling for localized routing.
Existing security associations according to [RFC5213] can be re-used
to protect signaling for localized routing on the interface between a
MAG and an LMA. In case a protocol solution for localized routing in
PMIPv6 relies on protocol operation between MAGs, means for
protection of signaling between these MAGs must be provided. The
same applies for signaling on a possible protocol interface between
two LMAs of the same domain.
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5. Acknowledgments
Many aspects of the problem space for route optimization in PMIPv6
have been discussed in the context of a PMIPv6 Route Optimization
Design Goals document, which has been submitted to the NetLMM WG in
November 2007. This group of contributors includes Sangjin Jeong,
Christian Vogt, Ryuji Wakikawa, Behcet Sarikaya, Shinta Sugimoto,
Long Le, Alice Qinxia and Jaehwoon Lee. Many thanks also to Rajeev
Koodli for his comments about the structure and scope of this problem
statement.
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6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
6.2. Informative References
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
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Author's Address
Marco Liebsch
NEC Laboratories Europe
NEC Europe Ltd.
Kurfuersten-Anlage 36
69115 Heidelberg,
Germany
Phone: +49 6221 4342146
Email: liebsch@nw.neclab.eu
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