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Differences from draft-ohba-mobopts-mpa-framework-03.txt
MOBOPTS Research Group A. Dutta (Ed.)
Internet-Draft Telcordia
Expires: September 6, 2007 V. Fajardo
Y. Ohba
K. Taniuchi
TARI
H. Schulzrinne
Columbia Univ.
March 5, 2007
A Framework of Media-Independent Pre-Authentication (MPA)
draft-ohba-mobopts-mpa-framework-04
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Copyright Notice
Copyright (C) The IETF Trust (2007).
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Abstract
This document describes a framework of Media-independent Pre-
Authentication (MPA), a new handover optimization mechanism that
addresses the issues on existing mobility management protocols and
mobility optimization mechanisms. MPA is a mobile-assisted, secure
handover optimization scheme that works over any link-layer and with
any mobility management protocol. MPA's pre-authentication, pre-
configuration, and proactive handover techniques allow many of the
handoff related operations to take place before the mobile has moved
to the new network. We describe the details of all the associated
techniques and its applicability for different scenarios.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Performance Requirements . . . . . . . . . . . . . . . . . 6
2. Existing Work on Fast Handover . . . . . . . . . . . . . . . . 8
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 10
4. MPA Framework . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. Functional Elements . . . . . . . . . . . . . . . . . . . 13
4.3. Basic Communication Flow . . . . . . . . . . . . . . . . . 15
5. Detailed Issues . . . . . . . . . . . . . . . . . . . . . . . 19
5.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 19
5.2. Pre-authentication in multiple CTN environment . . . . . . 20
5.3. Proactive IP address acquisition . . . . . . . . . . . . . 21
5.3.1. PANA-assisted proactive IP address acquisition . . . . 21
5.3.2. IKEv2-assisted proactive IP address acquisition . . . 22
5.3.3. Proactive IP address acquisition using DHCP only . . . 22
5.3.4. Proactive IP address acquisition using stateless
autoconfiguration . . . . . . . . . . . . . . . . . . 23
5.4. Address resolution issues . . . . . . . . . . . . . . . . 24
5.4.1. Proactive duplicate address detection . . . . . . . . 24
5.4.2. Proactive address resolution update . . . . . . . . . 24
5.5. Tunnel management . . . . . . . . . . . . . . . . . . . . 25
5.6. Binding Update . . . . . . . . . . . . . . . . . . . . . . 26
5.7. Preventing packet loss . . . . . . . . . . . . . . . . . . 27
5.7.1. Packet loss prevention in single interface MPA . . . . 27
5.7.2. Preventing packet losses for multiple interfaces . . . 27
5.7.3. Reachability test . . . . . . . . . . . . . . . . . . 28
5.8. Considerations for failed switching and switch-back . . . 29
5.9. Authentication state management . . . . . . . . . . . . . 30
5.10. Pre-allocation of QoS resources . . . . . . . . . . . . . 31
5.11. Resource allocation issue during pre-authentication . . . 31
5.12. Link-layer security and mobility . . . . . . . . . . . . . 33
5.13. Authentication in initial network attachment . . . . . . . 34
5.14. Multicast mobility . . . . . . . . . . . . . . . . . . . . 34
5.15. IP layer security and mobility . . . . . . . . . . . . . . 36
5.16. Pre-authentication with FA-CoA . . . . . . . . . . . . . . 37
5.17. Pre-authentication with ProxyMIPv6 . . . . . . . . . . . . 38
5.18. MPA for FMIPv6 . . . . . . . . . . . . . . . . . . . . . . 42
6. Applicability of MPA . . . . . . . . . . . . . . . . . . . . 44
7. Security Considerations . . . . . . . . . . . . . . . . . . . 45
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 47
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 48
10.1. Normative References . . . . . . . . . . . . . . . . . . . 48
10.2. Informative References . . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52
Intellectual Property and Copyright Statements . . . . . . . . . . 54
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1. Introduction
As wireless technologies including cellular and wireless LAN are
beginning to get popular, supporting terminal handovers across
different types of access networks, such as from a wireless LAN to
CDMA or to GPRS is considered a clear challenge. On the other hand,
supporting terminal handovers between access networks of the same
type is still more challenging, especially when the handovers are
across IP subnets or administrative domains. To address those
challenges, it is important to provide terminal mobility that is
agnostic to link-layer technologies in an optimized and secure
fashion without incurring unreasonable complexity. In this document
we discuss terminal mobility that provides seamless handovers with
low latency and low loss. Seamless handovers are characterized in
terms of performance requirements as described in Section 1.1.
[I-D.ohba-mobopts-mpa-implementation] is an accompanying document
which shows two sets of implementation of MPA including performance
results to show how existing protocols could be leveraged to realize
the functionalities of MPA.
Terminal mobility is accomplished by a mobility management protocol
that maintains a binding between a locator and an identifier of a
mobile terminal, where the binding is referred to as the mobility
binding. The locator of the mobile node may dynamically change when
there is a movement of the mobile terminal. The movement that causes
a change of the locator may occur when there is a change in
attachment point due to physical movement or network change. A
mobility management protocol may be defined at any layer. In the
rest of this document, the term "mobility management protocol" refers
to a mobility management protocol which operates at the network layer
or higher.
There are several mobility management protocols at different layers.
Mobile IP [RFC3344] and Mobile IPv6 [RFC3775] are mobility management
protocols that operate at the network layer. Similarly, MOBIKE
(IKEv2 Mobility and Multihoming) [I-D.ietf-mobike-design] is an
extension to IKEv2 that provides the ability to deal with a change of
an IP address of an IKEv2 end-point. There are several ongoing
activities in the IETF to define mobility management protocols at
layers higher than network layer. HIP (the Host Identity Protocol)
[I-D.ietf-hip-base] defines a new protocol layer between network
layer and transport layer to provide terminal mobility in a way that
is transparent to both network layer and transport layer. Also, SIP-
based mobility is an extension to SIP to maintain the mobility
binding of a SIP user agent [SIPMM].
While mobility management protocols maintain mobility bindings, these
cannot provide seamless handover if used in their current form. An
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additional optimization mechanism that works in the visited network
of the mobile terminal to prevent loss of outstanding packets
transmitted while updating the mobility binding is needed to achieve
seamless handovers. Such a mechanism is referred to as a mobility
optimization mechanism. For example, mobility optimization
mechanisms [I-D.ietf-mobileip-lowlatency-handoffs-v4] and [RFC4068]
are defined for Mobile IPv4 and Mobile IPv6, respectively, by
allowing neighboring access routers to communicate and carry
information about mobile terminals. There are protocols that are
considered as "helpers" of mobility optimization mechanisms. The
CARD (Candidate Access Router Discovery Mechanism) protocol
[I-D.ietf-seamoby-card-protocol] is designed to discover neighboring
access routers. The CTP (Context Transfer Protocol)
[I-D.ietf-seamoby-ctp] is designed to carry state that is associated
with the services provided for the mobile terminal, or context, among
access routers.
There are several issues in existing mobility optimization
mechanisms. First, existing mobility optimization mechanisms are
tightly coupled with specific mobility management protocols. For
example, it is not possible to use mobility optimization mechanisms
designed for Mobile IPv4 or Mobile IPv6 for MOBIKE. What is strongly
desired is a single, unified mobility optimization mechanism that
works with any mobility management protocol. Second, there is no
existing mobility optimization mechanism that easily supports
handovers across administrative domains without assuming a pre-
established security association between administrative domains. A
mobility optimization mechanism should work across administrative
domains in a secure manner only based on a trust relationship between
a mobile node and each administrative domain. Third, a mobility
optimization mechanism needs to support not only multi-interface
terminals where multiple simultaneous connectivity through multiple
interfaces can be expected, but also single-interface terminals.
This document describes a framework of Media-independent Pre-
Authentication (MPA), a new handover optimization mechanism that
addresses all those issues. MPA is a mobile-assisted, secure
handover optimization scheme that works over any link-layer and with
any mobility management protocol including Mobile IPv4, Mobile IPv6,
MOBIKE, HIP, SIP mobility. In MPA, the notion of IEEE 802.11i pre-
authentication is extended to work at higher layer, with additional
mechanisms to perform early acquisition of IP address from a network
where the mobile terminal may move as well as proactive handover to
the network while the mobile terminal is still attached to the
current network. Since this document focuses on the MPA framework,
it is left to future work to choose the protocols for MPA and define
detailed operations. The accompanying document
[I-D.ohba-mobopts-mpa-implementation] provides one method that
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describes usage and interactions between existing protocols to
accomplish MPA functionality.
1.1. Performance Requirements
In order to provide desirable quality of service for interactive VoIP
and streaming traffic, one needs to limit the value of end-to-end
delay, jitter and packet loss to a certain threshold level. ITU-T
and ITU-E standards define the acceptable values for these
parameters. For example for one-way delay, ITU-T G.114 [RG98]
recommends 150 ms as the upper limit for most of the applications,
and 400 ms as generally unacceptable delay. One way delay tolerance
for video conferencing is in the range of 200 to 300 ms [ITU98].
Also if an out-of-order packet is received after a certain threshold,
it is considered lost. References [RFC2679], [RFC2680] and 2681
[RFC2681] describe some of the measurement techniques for delay and
jitter.
An end-to-end delay consists of several components, such as network
delay, operating system (OS) delay, codec delay and application
delay. Network delay consists of transmission delay, propagation
delay, queueing delay in the intermediate routers. Operating System
related delay consists of scheduling behavior of the operating system
in the sender and receiver. codec delay is generally caused due to
packetization and depacketization at the sender and receiver end.
Application delay is mainly attributed to playout delay that helps
compensate for delay variation within a network. End-to-end delay
and amount of jitter can be adjusted using proper value of the
playout buffer at the receiver end. In case of interactive VoIP
traffic, end-to-end delay affects the jitter value, and is an
important issue to consider. During a mobile's handover, transient
traffic cannot reach the mobile and this contributes to the jitter as
well. If the end system has a playout buffer, then this jitter is
subsumed by the playout buffer delay, but otherwise this adds to the
delay for interactive traffic. Packet loss is typically caused by
congestion, routing instability, link failure, lossy links such as
wireless links. During a mobile's handover a mobile is subjected to
packet loss because of its change in attachment to the network. Thus
for both streaming traffic and VoIP interactive traffic packet loss
will contribute to the service quality of the real-time application.
Number of packets lost is proportional to the delay during handover
and rate of traffic the mobile is receiving. Lost packets contribute
to congestion in case of TCP traffic because of re-transmission, but
it does not add to any congestion in case of streaming traffic that
is RTP/UDP based. Thus it is essential to reduce the packet loss and
effect of handover delay in any mobility management scheme. In
Section 2, we describe some of the fast-handover scheme that have
tried to reduce the handover delay.
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According to ETSI TR 101 [ETSI], a normal voice conversation can
tolerate up to 2% packet loss. If a mobile is subjected to handoff
during a conversation, each handoff will contribute to packet loss
for the period of handoff.
ITU-T and ITU-R standards define the acceptable values for these
parameters. For example for one-way delay, ITU-T G.114 recommends
150 ms as the upper limit for most of the applications, and 400 ms as
generally unacceptable delay. One way delay tolerance for video
conferencing is in the range of 200 to 300 ms. Also if an out-of-
order packet is received after a certain threshold it is considered
lost. References [RFC2679], [RFC2680] and 2681 [RFC2681] describe
some of the measurement techniques for delay and jitter.
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2. Existing Work on Fast Handover
While basic mobility management protocols such as Mobile IP
[RFC3344], Mobile IPv6 [RFC3775], SIP-Mobility [SIPMM] provide
continuity to TCP and RTP traffic, these are not optimized to reduce
the handover latency during mobile's movement between subnets and
domains. In general these mobility management protocols suffer from
handover delays incurred at several layers such as, layer 3 and
application layer for updating the mobile's mobility binding. These
protocols also get affected due to underlying layer 2 delay as well.
There have been several optimization techniques that apply to current
mobility management schemes that try to reduce handover delay and
packet loss during a mobile's movement between cells, subnets and
domain. Micro-mobility management schemes [CELLIP], [HAWAII], and
intra-domain mobility management schemes such as [IDMP],
[I-D.ietf-mobileip-reg-tunnel] and [RFC4140] provide fast-handover by
limiting the signaling updates within a domain. Fast Mobile IP
protocols for IPv4 and IPv6 networks
[I-D.ietf-mobileip-lowlatency-handoffs-v4], [RFC4068] utilize
mobility information made available by link layer triggers. Yokota
et al. [YOKOTA] propose joint use of access point and a dedicated
MAC bridge to provide fast-handover without altering the MIPv4
specification. Shin et al [MACD] propose a scheme reduces the delay
due to MAC layer handoff by providing a cache-based algorithm. In
this scheme, the mobile caches the neighboring channels that it has
already visited and thus uses a selective scanning method. This
helps to reduce the associated scanning time.
Some mobility management schemes use dual interfaces thus providing
make-before-break [SUM]. In a make-before-break situation,
communication usually continues with one interface, when the
secondary interface is in the process of getting connected. The IEEE
802.21 working group is discussing these scenarios in details
[802.21]. Providing fast-handover using a single interface needs
more careful design than for a client with multiple interfaces.
Dutta et al [SIPFAST] provide an optimized handover scheme for SIP-
based mobility management, where the transient traffic is forwarded
from the old subnet to the new one by using an application layer
forwarding scheme. [MITH] provides a fast handover scheme for the
single interface case that uses mobile-initiated tunneling between
the old foreign agent and new foreign agent. [MITH] defines two
types of handover schemes such as Pre-MIT (Mobile Initiated
Tunneling) and Post-MIT (Media Initiated Tunneling). The proposed
MPA scheme is very similar to MITH's predictive scheme where the
mobile communicates with the foreign agent before actually moving to
the new network. However, MPA scheme is not limited to MIP type
mobility protocol only and in addition this scheme takes care of
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movement between domains and performs pre-authentication in addition
to proactive handover. Thus, MPA reduces the overall delay to close
to link-layer handover delay.
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3. Terminology
Mobility Binding: A binding between a locator and an identifier of a
mobile terminal.
Mobility Management Protocol (MMP): A protocol that operates at
network layer or above to maintain a binding between a locator and
an identifier of a mobile terminal.
Binding Update: A procedure to update a mobility binding.
Media-independent Pre-Authentication Mobile Node (MN): A mobile
terminal of media-independent pre-authentication (MPA) which is a
mobile-assisted, secure handover optimization scheme that works
over any link-layer and with any mobility management protocol. An
MPA mobile node is an IP node. In this document, the term "mobile
node" or "MN" without a modifier refers to "MPA mobile node". An
MPA mobile node usually has a functionality of a mobile node of a
mobility management protocol as well.
Candidate Target Network (CTN):
A network to which the mobile may move in the near future.
Target Network (TN): The network to which the mobile has decided to
move. The target network is selected from one or more candidate
target network.
Proactive Handover Tunnel (PHT): A bidirectional IP tunnel [RFC1853]
that is established between the MPA mobile node and an access
router of a candidate target network. In this document, the term
"tunnel" without a modifier refers to "proactive handover tunnel.
Point of Attachment (PoA): A link-layer device (e.g., a switch, an
access point or a base station) that functions as a link-layer
attachment point for the MPA mobile node to a network.
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Care-of Address (CoA): An IP address used by a mobility management
protocol as a locator of the MPA mobile node.
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4. MPA Framework
4.1. Overview
Media-independent Pre-Authentication (MPA) is a mobile-assisted,
secure handover optimization scheme that works over any link layer
and with any mobility management protocol. With MPA, a mobile node
is not only able to securely obtain an IP address and other
configuration parameters for a CTN, but also able to send and receive
IP packets using the IP address obtained before it actually attaches
to the CTN. This makes it possible for the mobile node to complete
the binding update of any mobility management protocol and use the
new CoA before performing a handover at link-layer.
MPA provides four basic procedures to provide this functionality.
The first procedure is referred to as "pre-authentication", the
second procedure is referred to as "pre-configuration", the
combination of the third and fourth procedures are referred to as
"secure proactive handover". The security association established
through pre-authentication is referred to as an "MPA-SA".
This functionality is provided by allowing a mobile node which has
connectivity to the current network but is not yet attached to a CTN,
to (i) establish a security association with the CTN to secure the
subsequent protocol signaling, then (ii) securely execute a
configuration protocol to obtain an IP address and other parameters
from the CTN as well as a execute tunnel management protocol to
establish a PHT (Proactive Handover Tunnel) [RFC1853] between the
mobile node and an access router of the CTN, then (iii) send and
receive IP packets, including signaling messages for binding update
of an MMP and data packets transmitted after completion of binding
update, over the PHT using the obtained IP address as the tunnel
inner address, and finally (iv) deleting or disabling the PHT
immediately before attaching to the CTN when it becomes the target
network and then re-assigning the inner address of the deleted or
disabled tunnel to its physical interface immediately after the
mobile node is attached to the target network through the interface.
Instead of deleting or disabling the tunnel before attaching to the
the target network, the tunnel may be deleted or disabled immediately
after being attached to the target network.
Especially, the third procedure described above (i.e., binding update
procedure) makes it possible for the mobile to complete the higher-
layer handover before starting link-layer handover. This means that
the mobile is able to send and receive data packets transmitted after
completing the binding update over the tunnel, while data packets
transmitted before completion of binding update do not use the
tunnel.
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4.2. Functional Elements
In the MPA framework, the following functional elements are expected
to reside in each CTN to communicate with a mobile node:
Authentication Agent (AA), Configuration Agent (CA) and Access Router
(AR). These elements can reside in one more network devices.
An authentication agent is responsible for pre-authentication. An
authentication protocol is executed between the mobile node and the
authentication agent to establish an MPA-SA. The authentication
protocol MUST be able to derive a key between the mobile node and the
authentication agent and SHOULD be able to provide mutual
authentication. The authentication protocol SHOULD be able to
interact with a AAA protocol such as RADIUS and Diameter to carry
authentication credentials to an appropriate authentication server in
the AAA infrastructure. The derived key is used for further deriving
keys used for protecting message exchanges used for pre-configuration
and secure proactive handover. Other keys that are used for
bootstrapping link-layer and/or network-layer ciphers MAY also be
derived from the MPA-SA. A protocol that can carry EAP [RFC3748]
would be suitable as an authentication protocol for MPA.
A configuration agent is responsible for one part of pre-
configuration, namely securely executing a configuration protocol to
securely deliver an IP address and other configuration parameters to
the mobile node. The signaling messages of the configuration
protocol MUST be protected using a key derived from the key
corresponding to the MPA-SA.
An access router is a router that is responsible for the other part
of pre-configuration, i.e., securely executing a tunnel management
protocol to establish a proactive handover tunnel to the mobile node.
The signaling messages of the configuration protocol MUST be
protected using a key derived from the key corresponding to the
MPA-SA. IP packets transmitted over the proactive handover tunnel
SHOULD be protected using a key derived from the key corresponding to
the MPA-SA.
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+----+
| |
| CN |
*----+
//
/--------\ /
|// \\//
| Core / |
|\X Network \
/ \--------/ \\
/ \
/ \
/ \\
+-------------/-----------+ +--------\-------------+
| +-----+ | |+-----+ |
| | | +-----+ | || | +-----+ |
| | AA | |CA | | ||AA | | CA | |
| +--+--+ +--+--+ | |+--+--+ +--+--+ |
| | +------+ | | | | +-----+ | |
| | | pAR | | | | | |nAR | | |
| ---+---+ +---+-----+----+---+-+ +-----+ |
| +---+--+ | | +-----+ |
| | | | |
| | | | |
| | | | |
+------------+------------+ +--------|--------------+
Current | Candidate| Target Network
Network | |
| |
| |
| |
| |
---+-------- --------|-----
///// \\\\\///// \\\\\
// //\\ \\
| +-+----+ | | |
| oPoA | MN | | | |
| | | | | |
| +------+ \\ | //
\\ XX\\\ nPoA /////
\\\\\ ///// -------------
------------
Figure 1: MPA Functional Components
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4.3. Basic Communication Flow
Assume that the mobile node is already connected to a point of
attachment, say oPoA (old point of attachment), and assigned a
care-of address, say oCoA (old care-of address). The communication
flow of MPA is described as follows. Throughout the communication
flow, data packet loss should not occur except for the period during
the switching procedure in Step 5, and it is the responsibility of
link-layer handover to minimize packet loss during this period.
Step 1 (pre-authentication phase): The mobile node finds a CTN
through some discovery process and obtains the IP addresses of an
authentication agent, a configuration agent and an access router in
the CTN (Candidate Target Network) by some means. The mobile node
performs pre-authentication with the authentication agent. If the
pre-authentication is successful, an MPA-SA is created between the
mobile node and the authentication agent. Two keys are derived from
the MPA-SA, namely an MN-CA key and an MN-AR key, which are used to
protect subsequent signaling messages of a configuration protocol and
a tunnel management protocol, respectively. The MN-CA key and the
MN-AR key are then securely delivered to the configuration agent and
the access router, respectively.
Step 2 (pre-configuration phase): The mobile node realizes that its
point of attachment is likely to change from oPoA to a new one, say
nPoA (new point of attachment). It then performs pre-configuration,
with the configuration agent using the configuration protocol to
obtain an IP address, say nCoA (new care-of address), and other
configuration parameters from the CTN, and with the access router
using the tunnel management protocol to establish a proactive
handover tunnel. In the tunnel management protocol, the mobile node
registers oCoA and nCoA as the tunnel outer address and the tunnel
inner address, respectively. The signaling messages of the pre-
configuration protocol are protected using the MN-CA key and the
MN-AR key. When the configuration and the access router are co-
located in the same device, the two protocols may be integrated into
a single protocol like IKEv2. After completion of the tunnel
establishment, the mobile node is able to communicate using both oCoA
and nCoA by the end of Step 4.
Step 3 (secure proactive handover main phase): The mobile node
decides to switch to the new point of attachment by some means.
Before the mobile node switches to the new point of attachment, it
starts secure proactive handover by executing the binding update
operation of a mobility management protocol and transmitting
subsequent data traffic over the tunnel (main phase). In some cases,
it may cache multiple nCOA addresses and perform simultaneous binding
with the CH or HA.
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Step 4 (secure proactive handover pre-switching phase): The mobile
node completes the binding update and becomes ready to switch to the
new point of attachment. The mobile may execute the tunnel
management protocol to delete or disable the proactive handover
tunnel and cache nCoA after deletion or disabling of the tunnel. The
decision as to when the mobile node is ready to switch to the new
point of attachment depends on the handover policy.
Step 5 (switching): It is expected that a link-layer handover occurs
in this step.
Step 6 (secure proactive handover post-switching phase): The mobile
node executes the switching procedure. Upon successful completion of
the switching procedure, the mobile node immediately restores the
cached nCoA and assigns it to the physical interface attached to the
new point of attachment. If the proactive handover tunnel was not
deleted or disabled in Step 4, the tunnel is deleted or disabled as
well. After this, direct transmission of data packets using nCoA is
possible without using a proactive handover tunnel.
An example call flow for MPA is shown in Figure 2 and Figure 3.
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IP address(es)
Available for
Use by MN
|
+-----------------------------------+ |
| Candidate Target Network | |
| (Future Target Network) | |
MN oPoA | nPoA AA CA AR | |
| | | | | | | | |
| | +-----------------------------------+ |
| | | | | | .
+---------------+ | | | | | .
|(1) Found a CTN| | | | | | .
+---------------+ | | | | | |
| Pre-authentication | | | |
| [authentication protocol] | | |
|<--------+------------->|MN-CA key| | |
| | | |-------->|MN-AR key| |
+-----------------+ | | |------------------>| |
|(2) Increased | | | | | | [oCoA]
|chance to switch | | | | | | |
| to CTN | | | | | | |
+-----------------+ | | | | | |
| | | | | | |
| Pre-configuration | | | |
| [configuration protocol to get nCoA] | |
|<--------+----------------------->| | |
| Pre-configuration | | | |
| [tunnel management protocol to establish PHT] V
|<--------+--------------------------------->|
| | | | | | ^
+-----------------+ | | | | | |
|(3) Determined | | | | | | |
|to switch to CTN | | | | | | |
+-----------------+ | | | | | |
| | | | | | |
| Secure proactive handover main phase | |
| [execution of binding update of MMP and | |
| transmission of data packets through AR | [oCoA, nCoA]
| based on nCoA over the PHT] | | |
|<<=======+================================>+--->... |
. . . . . . .
. . . . . . .
. . . . . . .
Figure 2: Basic Communication Flow (1/2)
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| | | | | | |
+----------------+ | | | | | |
|(4) Completion | | | | | | |
|of MMP BU and | | | | | | |
|ready to switch | | | | | | |
+----------------+ | | | | | |
| Secure proactive handover pre-switching phase |
| [tunnel management protocol to delete PHT] V
|<--------+--------------------------------->|
+---------------+ | | | |
|(5)Switching | | | | |
+---------------+ | | | |
| | | | |
+---------------+ | | | |
|(6) Completion | | | | |
|of switching | | | | |
+---------------+ | | | |
o<- Secure proactive handover post-switching phase ^
| [Re-assignment of TIA to the physical I/F] |
| | | | | |
| Transmission of data packets through AR | [nCoA]
| based on nCoA| | | | |
|<---------------+---------------------------+-->... |
| | | | | .
Figure 3: Basic Communication Flow (2/2)
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5. Detailed Issues
In order to provide an optimized handover for a mobile experiencing
rapid subnet and domain handover, one needs to look into several
issues. These issues include discovery of neighboring networking
elements, choosing the right network to connect to based on certain
policy, changing the layer 2 point of attachment, obtaining an IP
address from a DHCP or PPP server, confirming the uniqueness of the
IP address, pre-authenticating with the authentication agent, sending
the binding update to the correspondent host and obtaining the
redirected streaming traffic to the new point of attachment, ping-
pong effect, probability of moving to more than one network and
associating with multiple target networks. We describe these issues
in details in the following paragraphs and describe how we have
optimized these in case of MPA-based secure proactive handover.
5.1. Discovery
Discovery of neighboring networking elements such as access points,
access routers, authentication servers help expedite the handover
process during a mobile's rapid movement between networks. After
discovering the network neighborhood with a desired set of
coordinates, capabilities and parameters the mobile can perform many
of the operation such as pre-authentication, proactive IP address
acquisition, proactive address resolution, and binding update while
in the previous network.
There are several ways a mobile can discover neighboring networks.
The Candidate Access Router Discovery protocol
[I-D.ietf-seamoby-card-protocol] helps discover the candidate access
routers in the neighboring networks. Given a certain network domain
SLP (Service Location Protocol) and DNS help provide addresses of the
networking components for a given set of services in the specific
domain. In some cases many of the network layer and upper layer
parameters may be sent over link layer management frames such as
beacons when the mobile approaches the vicinity of the neighboring
networks. IEEE 802.11u is considering issues such as discovering
neighborhood using information contained in link layer. However, if
the link-layer management frames are encrypted by some link layer
security mechanism, then the mobile node may not be able to obtain
the requisite information before establishing link layer connectivity
to the access point. In addition this may add burden to the
bandwidth constrained wireless medium. In such cases a higher layer
protocol is preferred to obtain the information regarding the
neighboring elements. There is some proposal such as [802.21] that
helps obtain these information about the neighboring networks from a
mobility server. When the mobile's movement is imminent, it starts
the discovery process by querying a specific server and obtains the
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required parameters such as the IP address of the access point, its
characteristics, routers, SIP servers or authentication servers of
the neighboring networks. In the event of multiple networks, it may
obtain the required parameters from more than one neighboring
networks and keep these in cache. At some point the mobile finds out
several CTN's out of many probable networks and starts the pre-
authentication process by communicating with the required entities in
the CTN's. Futher details of this scenario is in Section 5.2.
5.2. Pre-authentication in multiple CTN environment
In some cases, although a mobile decides a specific network to be the
target network, it may actually end up with moving into a neighboring
network other than the target network due to factors that are beyond
the mobile's control. Thus it may be useful to perform the pre-
authentication with a few probable candidate target networks and
establish time-bound tunnels with the respective access routers in
those networks. Thus, in the event of a mobile moving to a candidate
target network other than that was chosen as the target network, it
will not be subjected to packet loss due to authentication and IP
address acquisition delay that could incur if the mobile did not pre-
authenticate with that candidate target network. It may appear that
by pre-authenticating with a number of candidate target networks and
reserving the IP addresses, the mobile is provisioning resources that
could be used otherwise. But since this happens for a time-limited
period it should not be a big problem. However, it depends upon the
mobility pattern and duration. Mobile uses pre-authentication
procedure to obtain IP address proactively and set up the time bound
tunnels with the access routers of the candidate target networks.
Also, MN may hold some or all of the nCoAs for future movement.
The mobile may choose one of these addresses as the binding update
address and send it to the CN (Correspondent Node) or HA (Home
Agent), and will thus receive the tunneled traffic via the target
network while in the previous network. But in some instances, the
mobile may eventually end up moving to a network that is other than
the target network. Thus, there will be a disruption in traffic as
the mobile moves to the new network since the mobile has to go
through the process of assigning the new IP address and sending the
binding update again. Two solutions can take care of this problem.
The mobile can take advantage of the simultaneous mobility binding
and send multiple binding updates to the corresponsing host or HA.
Thus, the corresponsing host or HA forwards the traffic to multiple
IP addresses assigned to the virtual interfaces for a specific period
of time. This binding update gets refreshed at the CH after the
mobile moves to the new network, thus stopping the flow to the other
candidate networks. Wakikawa [I-D.wakikawa-mobileip-multiplecoa]
discusses different scenarios of mobility binding with multiple care-
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of-addresses. In case simultaneous binding is not supported in a
specific mobility scheme, forwarding of traffic from the previous
target network will help take care of the transient traffic until the
new binding update is sent from the new network.
5.3. Proactive IP address acquisition
In general a mobility management protocol works in conjunction with
the Foreign Agent or in co-located address mode. MPA approach can
use both co-located address mode and foreign agent address mode. We
discuss here the address assignment component that is used in co-
located address mode. There are several ways a mobile node can
obtain an IP address and configure itself. Most commonly a mobile
can configure itself statically in the absence of any configuration
element such as a server or router in the network. The IETF Zeroconf
working group defines auto-IP mechanism where a mobile is configured
in an ad-hoc manner and picks a unique address from a specified range
such as 169.254.x.x. In a LAN environment the mobile can obtain an
IP address from DHCP servers. In case of IPv6 networks, a mobile has
the option of obtaining the IP address using stateless auto-
configuration or DHCPv6. In a wide area networking environment, the
mobile uses PPP to obtain the IP address by communicating with a NAS.
Each of these processes takes of the order of few hundred
milliseconds to few seconds depending upon the type of IP address
acquisition process and operating system of the clients and servers.
Since IP address acquisition is part of the handover process, it adds
to the handover delay and thus it is desirable to reduce this delay
as much as possible. There are few optimized techniques such as DHCP
Rapid Commit [I-D.ietf-dhc-rapid-commit-opt], GPS-coordinate based IP
address [GPSIP] available that attempt to reduce the handover time
due to IP address acquisition time. However, in all these cases the
mobile also obtains the IP address after it moves to the new subnet
and incurs some delay because of the signaling handshake between the
mobile node and the DHCP server.
In the following paragraph we describe few ways a mobile node can
obtain the IP address proactively from the CTN and the associated
tunnel setup procedure. These can broadly be divided into four
categories such as PANA-assisted proactive IP address acquisition,
IKE-assisted proactive IP address acquisition, proactive IP address
acquisition using DHCP only and stateless autoconfiguration.
5.3.1. PANA-assisted proactive IP address acquisition
In case of PANA-assisted proactive IP address acquisition, the mobile
node obtains an IP address proactively from a CTN. The mobile node
makes use of PANA [I-D.ietf-pana-pana] messages to trigger the
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address acquisition process on the DHCP relay agent [RFC3046] that is
colocated with the PANA authentication agent in the access router in
the CTN. Upon receiving a PANA message from the mobile node, the
DHCP relay agent performs normal DHCP message exchanges to obtain the
IP address from the DHCP server in the CTN. This address is piggy-
backed in a PANA message and is delivered to the client. In case of
MIPv6 with stateless autoconfiguration, the router advertisement from
the new target network is passed to the client as part of PANA
message. Mobile uses this prefix and its MAC address to construct
the unique IPv6 address as it would have done in the new network.
Mobile IPv6 in stateful mode works very similar to DHCPv4.
5.3.2. IKEv2-assisted proactive IP address acquisition
IKEv2-assisted proactive IP address acquisition works when an IPsec
gateway and a DHCP relay agent are resident within each access router
in the CTN. In this case, the IPsec gateway and DHCP relay agent in
a CTN help the mobile node acquire the IP address from the DHCP
server in the CTN. The MN-AR key established during the pre-
authentication phase is used as the IKEv2 pre-shared secret needed to
run IKEv2 between the mobile node and the access router. The IP
address from the CTN is obtained as part of standard IKEv2 procedure,
with using the co-located DHCP relay agent for obtaining the IP
address from the DHCP server in the target network using standard
DHCP. The obtained IP address is sent back to the client in the
IKEv2 Configuration Payload exchange. In this case, IKEv2 is also
used as the tunnel management protocol for a proactive handover
tunnel (see Section 5.5). Alternatively VPN-GW can itself dispense
the IP address from its IP address pool.
5.3.3. Proactive IP address acquisition using DHCP only
As another alternative, DHCP may be used for proactively obtaining an
IP address from a CTN without relying on PANA or IKEv2-based
approaches by allowing direct DHCP communication between the mobile
node and the DHCP relay or DHCP server in the CTN. In this case, the
mobile node sends a unicast DHCP message to the DHCP relay agent or
DHCP server in the CTN requesting an address, while using the address
associated with the current physical interface as the source address
of the request.
When the message is sent to the DHCP relay agent, the DHCP relay
agent relays the DHCP messages back and forth between the mobile node
and the DHCP server. In the absence of a DHCP relay agent the mobile
can also directly communicate with the DHCP server in the target
network. The broadcast option in client's unicast DISCOVER message
should be set to 0 so that the relay agent or the DHCP server can
send the reply directly back to the mobile using the mobile node's
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source address. This mechanism also works for an IPv6 node using
stateful configuration.
In order to prevent malicious nodes from obtaining an IP address from
the DHCP server, DHCP authentication should be used or the access
router should install a filter to block unicast DHCP message sent to
the remote DHCP server from mobile nodes that are not pre-
authenticated. When DHCP authentication is used, the DHCP
authentication key may be derived from the MPA-SA established between
the mobile node and the authentication agent in the candidate target
network.
The proactively obtained IP address is not assigned to the mobile
node's physical interface until the mobile has moved to the new
network. The IP address thus obtained proactively from the target
network should not be assigned to the physical interface but rather
to a virtual interface of the client. Thus, such a proactively
acquired IP address via direct DHCP communication between the mobile
node and the DHCP relay or the DHCP server in the CTN may be carried
with additional information that is used to distinguish it from other
address as assigned to the physical interface.
Upon the mobile's entry to the new network, the mobile node can
perform DHCP over the physical interface to the new network to get
other configuration parameters such as SIP server, DNS server by
using DHCP INFORM. This should not affect the ongoing communication
between the mobile and correspondent host. Also, the mobile node can
perform DHCP over the physical interface to the new network to extend
the lease of the address that was proactively obtained before
entering the new network.
5.3.4. Proactive IP address acquisition using stateless
autoconfiguration
For IPv6, network address is configured either using DHCPv6 or
stateless autoconfiguration. In order to obtain the new IP address
proactively, the router advertisement of the next hop router can be
sent over the established tunnel, and a new IPv6 address is generated
based on the prefix and MAC address of the mobile. Generating a COA
from the new network will avoid the time needed to obtain an IP
address and perform Duplicate Address Detection.
In order to maintain the DHCP binding for the mobile node and keep
track of the dispensed IP address before and after the secure
proactive handover, the same DHCP client identifier needs to be used
for the mobile node for both DHCP for proactive IP address
acquisition and DHCP performed after the mobile node enters the
target network. The DHCP client identifier may be the MAC address of
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the mobile node or some other identifier. In case of stateless
autoconfiguration, the mobile checks to see the prefix of the router
advertisement in the new network and matches it with the prefix of
newly assigned IP address. If these turn out to be the same then the
mobile does not go through the IP address acquisition phase again.
5.4. Address resolution issues
5.4.1. Proactive duplicate address detection
When the DHCP server dispenses an IP address, it updates its lease
table, so that this same address is not given to another client for
that specific period of time. At the same time the client also keeps
a lease table locally so that it can renew when needed. In some
cases where a network consists of both DHCP and non-DHCP enabled
clients, there is a probability that another client in the LAN may
have been configured with an IP address from the DHCP address pool.
In such scenario the server detects a duplicate address based on ARP
(Address Resolution Protocol) or IPv6 Neighbor Discovery before
assigning the IP address. This detection procedure may take from 4
sec to 15 sec [MAGUIRE] and will thus contribute to a larger handover
delay. In case of proactive IP address acquisition process, this
detection is performed ahead of time and thus does not affect the
handover delay at all. By performing the duplicate address detection
ahead of time, we reduce the IP address acquisition time.
5.4.2. Proactive address resolution update
During the process of pre-configuration, the MAC address resolution
mappings needed by the mobile node to communicate with nodes in the
target network after attaching to the target network can also be
known, where the communicating nodes maybe the access router,
authentication agent, configuration agent and correspondent node.
There are several possible ways of performing such proactive MAC
address resolution.
o Use an information service mechanism [802.21] to resolve the MAC
addresses of the nodes. This might require each node in the
target network to be involved in the information service so that
the server of the information service can construct the database
for proactive MAC address resolution.
o Extend the authentication protocol used for pre-authentication or
the configuration protocol used for pre-configuration to support
proactive MAC address resolution. For example, if PANA is used as
the authentication protocol for pre-authentication, PANA messages
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may carry AVPs used for proactive address resolution. In this
case, the PANA authentication agent in the target network may
perform address resolution for on behalf of the mobile node.
o One can also make use of DNS to map the MAC address of the
specific interface associated with a specific IP address of the
network element in the target network. One may define a new DNS
resource record (RR) to proactively resolve the MAC addresses of
the nodes in the target network. But this approach may have its
own limitations since a MAC address is a resource that is bound to
an IP address, not directly to a domain name.
When the mobile node attaches to the target network, it installs the
proactively obtained address resolution mappings without necessarily
performing address resolution queries for the nodes in the target
network.
On the other hand, the nodes that reside in the target network and
are communicating with the mobile node should also update their
address resolution mappings for the mobile node as soon as the mobile
node attaches to the target network. The above proactive address
resolution methods could also be used for those nodes to proactively
resolve the MAC address of the mobile node before the mobile node
attaches to the target network. However, this is not useful since
those nodes need to detect the attachment of the mobile node to the
target network before adopting the proactively resolved address
resolution mapping. A better approach would be integration of
attachment detection and address resolution mapping update. This is
based on gratuitously performing address resolution [RFC3344],
[RFC3775] in which the mobile node sends an ARP Request or an ARP
Reply in the case of IPv4 or a Neighbor Advertisement in the case of
IPv6 immediately after the mobile node attaches to the new network so
that the nodes in the target network can quickly update the address
resolution mapping for the mobile node.
5.5. Tunnel management
After an IP address is proactively acquired from the DHCP server in a
CTN, a proactive handover tunnel is established between the mobile
node and the access router in the CTN. The mobile node uses the
acquired IP address as the tunnel's inner address.
The proactive handover tunnel is established using a tunnel
management protocol. When IKEv2 is used for proactive IP address
acquisition, IKEv2 is also used as the tunnel management protocol.
Alternatively, when PANA is used for proactive IP address
acquisition, PANA may be used as the secure tunnel management
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protocol.
Once the proactive handover tunnel is established between the mobile
node and the access router in the candidate target network, the
access router also needs to perform proxy address resolution (Proxy
ARP) on behalf of the mobile node so that it can capture any packets
destined to the mobile node's new address.
Since the mobile needs to be able to communicate with the
correspondent node while in the previous network some or all parts of
binding update and data from the correspondent node to mobile node
need to be sent back to the mobile node over a proactive handover
tunnel. Details of these binding update procedure are described in
Section 5.7.
In order for the traffic to be directed to the mobile node after the
mobile node attaches to the target network, the proactive handover
tunnel needs to be deleted or disabled. The tunnel management
protocol used for establishing the tunnel is used for this purpose.
Alternatively, when PANA is used as the authentication protocol the
tunnel deletion or disabling at the access router can be triggered by
means of PANA update mechanism as soon as the mobile moves to the
target network. A link-layer trigger ensures that the mobile node is
indeed connected to the target network and can also be used as the
trigger to delete or disable the tunnel.
5.6. Binding Update
There are several kinds of binding update mechanisms for different
mobility management schemes.
In case of Mobile IPv4 and Mobile IPv6, the mobile performs a binding
update with the home agent only, if route optimization is not used.
Otherwise, the mobile performs binding update with both the home
agent (HA) and corresponding node (CN).
In case of SIP-based terminal mobility, the mobile sends binding
update using INVITE to the correspondent node and REGISTER message to
the Registrar. Based on the distance between the mobile and the
correspondent node, the binding update may contribute to the handover
delay. SIP-fast handover [SIPFAST] provides several ways of reducing
the handover delay due to binding update. In case of secure
proactive handover using SIP-based mobility management we do not
encounter the delay due to binding update completely, as it takes
place in the previous network.
Thus, this scheme looks more attractive when the correspondent node
is too far from the communicating mobile node. Similarly, in case of
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Mobile IPv6, the mobile sends the newly acquired CoA from the target
network as the binding update to the HA and CN. Also all signaling
messages between MN and HA and between MN and CN are passed through
this proactive tunnel that is set up. These messages include Binding
Update (BU), Binding Acknowledgement (BA) and the associated return
routability messages such as Home Test Init (HoTI), Home Test (HoT),
Care-of Test Init (CoTI), Care-of Test (COT).
If the proactive handover tunnel is realized as an IPsec tunnel, it
will also protect these signaling messages between the tunnel end
points and will make the return routability test more secured. Any
subsequent data will also be tunneled through as long as the mobile
is in the previous network. The accompanying document
[I-D.ohba-mobopts-mpa-implementation] talks about the details of how
binding updates and signaling for return routability are sent over
the secured tunnel.
5.7. Preventing packet loss
5.7.1. Packet loss prevention in single interface MPA
For single interface MPA, there may be some transient packets during
link-layer handover that are directed to the mobile node at the old
point of attachment before the mobile node is able to attach to the
target network. Those transient packets can be lost. Buffering
these packets at the access router of the old point of attachment can
eliminate packet loss. Dynamic buffering signals that are signalled
from the MN can temporarily hold transient traffic during handover
and then these packets can be forwarded to the MN once it attaches to
the target network. A detailed analysis of buffering can technique
can be found in [PIMRC06].
An alternative method is to use bicasting. Bicasting helps to
forward the traffic to two destinations at the same time. However,
it does not eliminate packet loss if link-layer handover is not
seamlessly performed. On the other hand, buffering does not reduce
packet delay. While packet delay can be compensated by playout
buffer at the receiver side for streaming application, playout buffer
does not help much for interactive VoIP application that cannot
tolerate for large delay jitters. Thus it is still important to
optimize the link-layer handover anyway.
5.7.2. Preventing packet losses for multiple interfaces
MPA usage in multi-interface handover scenario involves preparing the
second interface for use via the current active interface. This
preparation involves pre-authentication and provisioning at a target
network where the second interface would be the eventual active
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interface. An example, during inter-technology handover from a Wi-Fi
to a CDMA network, pre-authentication at the CDMA network can be
performed via the Wi-Fi interface. Handover occurs when the CDMA
interface becomes the active interface for the MN.
In such scenario, if handover occurs while both interfaces are
active, there is generally no packet loss since transient packets
directed towards the old interface will still reach the MN. However,
if sudden disconnection of the current active interface is used to
initiate handover to the prepared interface then transient packets
for the disconnected interface will be lost while the MN attempts to
be reachable at the prepared interface. In such cases, a specialized
form of buffering can be used to eliminate packet loss where packets
are merely copied at an access router in the current active network
prior to disconnection. If sudden disconnection does occur, copied
packets can be forwarded to the MN once the prepared interface
becomes the active reachable interface. The copy-and-foward
mechanism is not limited to multi-interface handover.
A notable side-effect of this process is the possible duplication of
packets during forwarding to the new active interface. Several
approaches can be employed to minimize this effect. Relying on upper
layer protocols such as TCP to detect and eliminate duplicates is the
most common approach. Customized duplicate detection and handling
techniques can also be used. In general, packet duplication is a
well known issue that can also be handled locally by the MN.
If the mobile takes a longer amount of time to detect the
disconnection event of the current active interface, it can also have
an adverse effect on the length of the handover process. Thus it
becomes necessary to use an optimized scheme of detecting interface
disconnection in such scenarios.
5.7.3. Reachability test
In addition to previous techniques, the MN may also want to ensure
reachability of the new point of attachment before switching from the
old one. This can be done by exchanging link-layer management frames
with the new point of attachment. This reachability check should be
performed as quickly as possible. In order to prevent packet loss
during this reachability check, transmission of packets over the link
between the MN and old point of attachment should be suspended by
buffering the packets at the both ends of the link during the
reachability check. How to perform this buffering is out of scope of
this document. Some of the results using this buffering scheme are
explained in the accompanying implementation document.
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5.8. Considerations for failed switching and switch-back
The ping-Pong effect is one of the common problems found during
handover. The Ping-pong effect arises when a mobile is located at
the borderline of the cell or decision point and a handover procedure
is frequently executed. This results in higher call drop
probability, lower connection quality, increased signaling traffic
and waste of resources. All of these affect mobility optimization.
Handoff algorithms are the deciding factors for performing the
handoff between the networks. Traditionally these algorithms employ
a threshold to compare the values of different metrics to decide on
the handoff. These metrics include signal strength, path loss,
carrier-to-interference ratios (CIR), Signal to Interference Ratios
(SIR), Bit Error Rate (BER), power budget. In order to avoid the
ping-pong effect, some additional parameters are employed by the
decision algorithm such as hystereris margin, dwell timers, and
averaging window. For a vehicle moving with a high speed, other
parameters such as distance between the mobile node and the point of
attachment, velocity of the mobile, location of the mobile, traffic
and bandwidth characteristics are also taken into account to reduce
the ping-pong effect. Most recently there are other handoff
algorithms that help reduce the ping-pong effect in a heterogeneous
network environment that are based on techniques such as hypothesis
testing, dynamic programming and pattern recognition techniques.
While it is important to devise smart handoff algorithms to reduce
the ping-pong effect, it is also important to devise methods to
recover from these effect.
In the case of MPA framework, the ping-pong effect will result in the
back-and-forth movement of the mobile between the current network and
target network and between the candidate target networks. MPA in its
current form will be affected because of many number of tunnel setup,
number of binding updates and associated handoff latency resulting
out of ping-pong situation. Mobile's handoff rate may also
contribute to delay and packet loss. We propose several algorithms
that will help reduce the probability of ping-pong and propose
several methods for the MPA framework so that it can recover from the
packet loss resulting out of ping-pong effect.
The MPA framework can take advantage of the mobile's geo-location
with respect to APs in the neighboring networks using GPS. In order
to avoid the oscillation between the networks, a location-based
intelligent algorithm can be derived by using a co-relation between
user's location and cached data from the previous handover attempts.
In some cases only location may not be the only indicator for a
handoff decision. For example in Manhattan type grid networks,
although a mobile is close to an AP, it may not have enough SNR
(Signal to Noise Ration) to make a good connection. Thus knowledge
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of mobility pattern, dwell time in a call and path identification
will help avoid the ping-pong problem to a great extent.
In the absence of a good handoff algorithm that can avoid ping-pong
effect, it may be required to put in place a good recovery mechanism
so as to mitigate the effect of ping-pong. It may be necessary to
keep the established context in the current network for a period of
time, so that it can be quickly recovered when the mobile comes back
to the network where the context was last used. These context may
include security association, IP address used, tunnels established.
Bicasting the data to both previous network and new network for a
predefined period will also the mobile help take care of the lost
packets in case the mobile moves back and forth between the networks.
The mobile can also take certain action, after it determines that it
is in a stable state with respect to ping-pong situation.
When MPA framework takes advantage of a combination of IKEv2 and
MOBIKE, the ping-pong effect can be reduced further [mpa-mobike].
5.9. Authentication state management
In case of pre-authentication with multiple target networks, it is
useful to maintain the state in the authentication agent of each of
the neighboring networks for certain time. Thus if the mobile does
move back and forth between neighboring networks, already maintained
authentication state can be helpful. We provide some highlights on
multiple security association state management below.
A MN that has pre-authenticated to an authentication agent in a
candidate target network and has a MPA-SA, may need to continue to
keep the MPA-SA while it continues to stay in the current network or
even after it does handover to a network that is different from the
candidate target network.
When an MN that has been authenticated and authorized by an
authentication agent in the current network makes a handover to a
target network, it may want to hold the SA that has been established
between the MN and the authentication agent for a certain time period
so that it does not have to go through the entire authentication
signaling to create an SA from scratch in case it returns to the
previous network. Such an SA being held at the authentication agent
after the MN's handover to other network is considered as an MPA-SA.
In this case, the authentication agent should change the fully
authorized state for the MN to an unauthorized state. The
unauthorized state can be changed to the fully authorized state only
when the MN comes back to the network and provides a proof of
possession of a key associated with the MPA-SA.
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While an MPA-SA is being held at an authentication agent, the MN will
need to keep updating the authentication agent when an IP address of
the MN changes due to a handover to re-establish the new SA.
5.10. Pre-allocation of QoS resources
In the pre-configuration phase, it is also possible to pre-allocate
QoS resources that may be used by the mobile node not only after
handover but also before handover. When pre-allocated QoS resources
are used before handover, it is used for application traffic carried
over a proactive handover tunnel.
It is possible that QoS resources are pre-allocated in an end-to-end
fashion. One method to achieve this proactive end-to-end QoS
reservation is to execute NSLP [I-D.ietf-nsis-qos-nslp] or RSVP
[RFC2205] over a proactive handover tunnel where pre-authentication
can be used for bootstrapping a security association for the
proactive handover tunnel to protect the QoS signaling. In this
case, QoS resources are pre-allocated on the path between the
correspondent node and a target access router can be used
continuously before and after handover. On the other hand, duplicate
pre-allocation of QoS resources between the target access router and
the mobile node is necessary when using pre-allocated QoS resources
before handover due to difference in paths between the target access
router and the mobile node before and after handover. QoS resources
to be used for the path between the target access router and the
mobile node after handover may be pre-allocated by extending NSLP to
work for off-path signaling (Note: this path can be viewed as off-
path before handover) or by media-specific QoS signaling at layer 2.
5.11. Resource allocation issue during pre-authentication
In case of multiple CTNs, establishing multiple tunnels with the
neighboring target networks provides some additional benefits. But
it also contributes to some resource utilization issues as well.
Pre-authentication process with multiple candidate target networks
can happen in several ways.
The very basic scheme involves authenticating the mobile with the
multiple authentication agents in the neighboring networks, but
actual pre-configuration and binding update take place only after
layer 2 movement to a specific network is complete.
Similarly, in addition to pre-authentication, the mobile can also
complete the pre-configuration while in the previous network, but can
postpone the binding update until after the mobile has moved. Like
the previous case, in this case the mobile also does not need to set
up the pre-configured the tunnels. While pre-authentication process
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and part of pre-configuration process are taken care of before the
mobile has moved to the new network, binding update is actually done
after the mobile has moved.
The third type of multiple pre-authentication involves all the three
steps while the mobile is in the previous networks, such as
authentication, configuration and binding update. But, this specific
process utilizes the most amount of resources. Some of the resources
that get used during this process are as follows:
1)Additional signaling for pre-authentication in the neighboring
networks
2)Holding the IP address of the neighboring networks in mobiles cache
for certain amount of time. It needs additional processing in the
mobile for storing these IP addresses. In addition it also uses up
the temporary IP addresses from the neighboring routers.
3)There is an additional cost associated with setting up additional
transient tunnels with the target routers in the neighboring networks
and mobile.
4) In case of binding update with multiple IP addresses obtained from
the neighboring networks, multiple transient streams flow between the
CN and mobile using these transient tunnels.
When only pre-authentication and pre-configuration are done ahead of
time with multiple networks, the mobile sends one binding update to
the CN. In this case it is important to find out when to send the
binding update after the layer 2 handoff.
In case binding update with multiple contact addresses is sent,
multiple media streams stem out of CN using the transient tunnels.
But in that case one needs to send another Binding Update after the
handover with the contact address set to the new address (only one
address) where the mobile has moved. This way the mobile stops
sending media to other neighboring networks where the mobile did not
move.
The following is an illustration of this specific case that takes
care of multiple binding streams, when the mobile moves only to a
specific network, but sends multiple binding updates in the previous
network. MN sends a binding update to CH with multiple contact
addresses such as c1,c2, and c3 that were obtained from three
neighboring networks. This allows the CN to send transient multiple
streams to the mobile over the pre-setablished tunnels. After the
mobile moves to the actual network, it sends another binding update
to the CN with the care-of-address of the mobile in the network where
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the mobile has moved in. Some of the issues with multiple stream are
consumption of extra bandwidth for a small period of time.
Alternatively, one can apply the buffering technique at the target
access router or at the home agent. Transient data can be forwarded
to the mobile after it has moved in. Forwarding of data can be
triggered by the mobile either as part of Mobile IP registration or
as a separate buffering protocol.
5.12. Link-layer security and mobility
Using the MPA-SA established between the mobile node and the
authentication agent for a CTN, during the pre-authentication phase,
it is possible to bootstrap link-layer security in the CTN while the
mobile node is in the current network in the following way. Figure 4
shows the sequence of operation.
(1) The authentication agent and the mobile node derives a PMK (Pair-
wise Master Key) [I-D.ietf-eap-keying] using the MPA-SA that is
established as a result of successful pre-authentication. Successful
operation of EAP and an AAA protocol may be involved during pre-
authentication to establish the MPA-SA. From the PMK, distinct TSKs
(Transient Session Keys) [I-D.ietf-eap-keying] for the mobile node
are directly or indirectly derived for each point of attachment of
the CTN.
(2) The authentication agent may install the keys derived from the
PMK and used for secure association to points of attachment. The
derived keys may be TSKs or intermediary keys from which TSKs are
derived.
(3) After the mobile node chooses a CTN as the target network and
switches to a point of attachment in the target network (which now
becomes the new network for the mobile node), it executes a secure
association protocol such as the IEEE 802.11i 4-way handshake
[802.11] using the PMK in order to establish PTKs (Pair-wise
Transient Keys) and GTKs (Group Transient Keys) [I-D.ietf-eap-keying]
used for protecting link-layer packets between the mobile node and
the point of attachment. No additional execution of EAP
authentication is needed here.
(4) While the mobile node is roaming in the new network, the mobile
node only needs to perform a secure association protocol with its
point of attachment point and no additional execution of EAP
authentication is needed either. Integration of MPA with link-layer
handover optimization mechanisms such as 802.11r can be archived this
way.
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The mobile node may need to know the link-layer identities of the
point of attachments in the CTN to derive TSKs. If PANA is used as
the authentication protocol for pre-authentication, this is possible
by carrying Device-Id AVPs in the PANA-Bind-Request message sent from
the PAA [I-D.ietf-pana-pana], with each AVP containing the BSSID of a
distinct access point.
_________________ ____________________________
| Current Network | | CTN |
| ____ | | ____ |
| | | (1) pre-authentication | | |
| | MN |<------------------------------->| AA | |
| |____| | | |____| |
| . | | | |
| . | | | |
|____.____________| | | |
.movement | |(2) Keys |
____.___________________| | |
| _v__ _____ | |
| | |(3) secure assoc. | | | |
| | MN |<------------------>| AP1 |<-------+ |
| |____| |_____| | |
| . | |
| .movement | |
| . | |
| . | |
| _v__ _____ | |
| | |(4) secure assoc. | | | |
| | MN |<------------------>| AP2 |<-------+ |
| |____| |_____| |
|_____________________________________________________|
Figure 4: Bootstrapping Link-layer Security
5.13. Authentication in initial network attachment
When the mobile node initially attaches to a network, network access
authentication would occur regardless of the use of MPA. The
protocol used for network access authentication when MPA is used for
handover optimization can be a link-layer network access
authentication protocol such as IEEE 802.1X or a higher-layer network
access authentication protocol such as PANA.
5.14. Multicast mobility
A specific mobile can subscribe to one or more IP multicast group.
When a mobile moves to a new network multicast communication is
interrupted because of the associated join latency. This
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interruption can be minimized by reducing the join latency during the
mobile's movement. Multicast mobility can be home subscription-based
or remote subscription based. In home subscription-based approach
there is a multicast router in the home network, that joins on behalf
of the mobile. But all the data and control signal are tunneled
between the home agent and foreign agent or the mobile. Home
subscription based approach is not suitable for mobility protocols
other than MIPv4 or MIPv6 as it depends upon the multicast router at
the home network and the tunnel. On the other hand remote
subscription-based approach does not add any burden on the home agent
unlike the previous approach but communicates with the first hop
router in the remote network everytime it moves.
MPA can help to provide proactive multicast mobility support for both
the approaches. We first describe the remote subscription-based
approach in case of MPA. There are two ways to reduce the join
latency in case of MPA by joining the multicast tree proactively. In
MPA scenario, Next Access Router (NAR) can behave as the multicast
proxy when the mobile is about to move to the new network. During
the pre-configuration phase of the MPA process after the mobile has
been pre-authenticated, the mobile can pass on the information about
the multicast groups that it is currently subscribed to. As an
example, if PANA is used as the protocol to preconfigure the mobile
in the current network by interacting with the configuration server
in the next network, then it can also pass on the currently
subscribed group information to the PAA (Pana Authentication Agent)
as part of the PUR message. PAA in turn can communicate with the NAR
to trigger the multicast join to the upstream router. Thus during
the tunnel setup process between the mobile and NAR, NAR also joins
the multicast group on behalf of the mobile.
Alternatively the mobile can directly send the multicast join request
to the NAR using the tunnel created in the current network even
before the mobile has moved in. In this case the source address of
the multicast join request will be set to that of mobile's tunnel
end-point address, so that the NAR can figure out from which
interface the request has come in and assumes that there is a host
subscribed in that interface. In both the cases we assume that NAR
is configured as a multicast router as well. When the mobile is in
the current network, it can still receive the multicast traffic via
the PAR on its currently configured IP address. But as soon as the
mobile moves to the new network and deletes the tunnel, it starts
receiving the multicast traffic on the same group multicast address
with almost zero join latency. Since the mobile already has obtained
an address ahead of time it also does not need to spend any time to
configure its interface.
In case of home subscription based approach, MPA can provide the
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mobility support for multicast services the way it provides unicast
services for both MIPv4 and MIPv6. The data gets delivered to the
mobile in the previous network via the transient MPA tunnel between
the mobile and the next access router. This tunnel is usually a
tunnel within a tunnel. As the mobile moves to the new network,
regular MIP tunnel takes care of delivering the multicast traffic in
the new network. This mechanism provides fast delivery of multicast
stream, as the home agent has already started to send multicast
traffic destined to the new network.
5.15. IP layer security and mobility
IP layer security is typically maintained between the mobile and
first hop router or any other network element such as SIP proxy by
means of IPsec. This IPSec SA can be set up either in tunnel mode or
in ESP mode. However, as the mobile moves IP address of the router
and outbound proxy will change in the new network, mobile's IP
address may or may not change depending upon the mobility protocol
being used. This will warrant re-establishing a new security
association between the mobile and the desired network entity. In
some cases such as in 3GPP/3GPP2 IMS/MMD environment data traffic is
not allowed to pass through unless there is an IPsec SA established
between the mobile and outbound proxy. This will of course add
unreasonable delay to the existing real-time communication during
mobile's movement. In this scenario key exchange is done as part of
SIP registration that follows a key exchange procedure called AKA
(Authentication and Key Agreement).
MPA can be used to bootstrap this security association as part of
pre-authentication via the new outbound proxy. Prior to the movement
if the mobile can pre-register via the new outbound proxy in the
target network and completes the pre-authentication procedure, then
the new SA state between the mobile and new outbound proxy can be
established prior to the movement to the new network. A similar
approach can also be applied if a key exchange mechanism other than
AKA is used or the network element with which the security
association has to be established is different than an outbound
proxy.
By having the security association established ahead of time, the
mobile does not need to involve in any exchange to set up the new
security association after the movement. Any further key exchange
will be limited to renew the expiry time. This will also reduce the
delay for real-time communication as well.
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5.16. Pre-authentication with FA-CoA
In many of the deployment scenarios such as in IMS/MMD (IP Multimedia
Subsystem/Multimedia Domain) architecture using MIPv4 as the binding
protocol, IP address of the mobile does not change as the mobile
moves from one visited network to another. A typical example is when
the mobile uses MIPv4 and uses FA Care-of-Address and interacts with
the outbound SIP proxy. In such a situation the mobile has only its
Home Address (HoA) assigned to its interface. MPA mechanism in its
current form will give rise to routing loop, if the mobile uses HoA
as the outer address of the MPA proactive tunnel described
previously.
In this scenario while the mobile is still with pFA, if it sets up a
proactive tunnel with nFA using the HoA as the outer address and
sends the binding update with with nFA's care-of-address, then any
packet destined to mobile will first be routed to nFA and then
because of the associated tunnel, it will be sent back to the HA,
resulting in a routing loop.
In order to take care of this routing problem we propose different
ways of creating two tunnels such as forward proactive and reverse
proactive tunnels. Forward proactive tunnel helps tunnel the traffic
from nFA to MN whereas the packets from the mobile goes over the
reverse proactive tunnel. We propose to use p-FA's CoA as the tunnel
outer address of the MN for forward proactive tunnel and propose to
use mobile's HoA as the outer address of the reverse proactive
tunnel. Traffic destined to HoA when arrives at nFA will get routed
to pFA over proactive tunnel using the host based routing set up at
nFA. Figure 5 shows a scenario of assymmetric procative tunnel that
is needed to care of this routing loop.
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+------+ +----+
| +---------| |
|HA | |CN |
+-++---+ +----+
Forward Proactive ||
Handover Tunnel ||/ Mobile IP
||--------Forward and Reverse
| ||\ Tunnel
| ||
+------+ \|/ +--++--+
| +--------------+ |
|pFA +--------------+nFA |
| -+--------------+ |
+---+-++--------------+------+
| | /|\
| |/ |
| |--------Reverse Proactive
| |\ Handover Tunnel
+--+-+
|MN |
| |
+----+
Figure 5: MPA with FA-CoA Scenario
5.17. Pre-authentication with ProxyMIPv6
In this section, we describe how one can achieve fast handoff for
ProxyMIPv6 using Media-independent Pre-Authentication (MPA)
technique. PrxyMIPv6 is a network layer localized protocol being
discussed in NETLMM working group within IETF currently. The goals
and advantages for local mobility management have duly been
documented in the problem statement [I-D.kempf-netlmm-nohost-ps] and
no-host-requirement [I-D.kempf-netlmm-nohost-req] drafts.
Advantage of local mobility management is to optimize many of the
functions related to mobility and reduce the number of signaling
messages over the air. ProxyMIPv6 [I-D.sgundave-mipv6-proxymipv6] is
currently one of the candidate protocols that can take care of the
localized mobility management when the mobile's movement is limited
within a domain. It follows many of the goals and advantages that
have been discussed as part of the problem statement and no host-
requirement drafts. However, ProxyMIPv6 in its current form still
needs a mechanism to provide fast-handover. There are several
components within ProxyMIPv6 that contribute to the overall handoff
delay. These components include access authentication, profile
verification, home address reconfiguration, and binding update.
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However, things appear to be more complicated and handoff takes more
time for inter-domain case, as it involves two home agents in each
domain and the home prefix advertisement is different in each domain.
MPA-based fast-handover takes advantage of the pre-authentication
mechanism so that the mobile can perform the access authentication
and other related handover operations while under the previous proxy
mobility agent (PMA) domain. In this section, we describe how Media
Independent Pre-authentication techniques can be used to provide fast
handover for both intra-domain and inter-domain roaming involving
ProxyMIPv6. The draft [I-D.taniuchi-netlmm-mpa-proxymipv6] discusses
the details of MPA-assisted fast-handover techniques for ProxyMIPv6.
We only provide the highlights of MPA framework in the context of
ProxyMIPv6. In particular, we limit our discussion to the intra-
domain movement scenario only. The bootstrapping scenario remains
same independent of if the mobile is going to be subjected to intra-
domain or inter-domain handoff. Next, we discuss how pre-
authentication technique helps to achieve fast-handoff for intra-
domain handover scenario.
When the mobile is in the previous network, access authentication
takes place according to the standard proxyMIPv6 specification. In
case of intra-domain handoff, both the PMAs (Proxy Mobile Agents)
share the same home agent (HA). We consider the scenario where the
mobile moves from one PMA to another PMA within the same home agent
domain. We describe the steps associated with the pre-
authentication.
During the pre-authentication phase, the mobile can complete the
layer 3 and layer 2-based access authentication while still in the
previous network, thereby reducing the time due to pre-
authentication. Figure 6 shows an example of pre-authentication in
proxyMIPv6 case.
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+-----+ +-----+
| \ | AAA |
|CN |\\ | |
+-----+ \ *-+---+
\*-----+ /|\|
/\ | | |
/|HA | | |
/ *-----+ | |
/ / | |
/ / | |
/ / | |
+---|-*/ ++-+---+
|pPMA X------------+|nPMA |
|pPAA |\ ||nPAA |
|pAR-+-+-----------++nNAR |
+--\*-* +------+
\\ \
\\ \
\\ \
\\ \
\\ \ -----------
-------\\-\ /// \\\
/// \\\XX \\
|| +-\\+\+| |
| | | | | |
| | MN| | | |
|| +-----+| //
\\\ ///\\\ ///
---------- -----------
Figure 6: Pre-authentication phase
As part of the pre-authentication phase, a proactive tunnel is
created between pPMA and nPMA. After the tunnel is created between
the pPMA and nPMA during the authentication phase, nPMA sends a proxy
binding update on behalf of the mobile. During the proxy binding
update the the data still flows through the pPMA.
After the proxy-binding update is sent to the HA from nPMA on behalf
of the mobile, another tunnel is created between HA and nPMA. Figure
7 shows this procedure. However, while this tunnel is being created,
the data still flows through pPMA. Thus, data loss is avoided during
this tunnel creation. However, after the tunnel is created the new
data gets forwarded to oPoA via two tunnels - the tunnel between HA
and nPMA and the tunnel between nPMA and pPMA. The tunnel between HA
and pPMA can time-out, it does not need to be deleted specifically.
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+-----+
| | +-----+
| CN | |AAA |
+-----* | |
\ +-----+
\
\ +------+
\ | HA |
\ | \
\*-/---\+\
/ / \ \
/ / \ \
/ / \ \
+-------+/ / \+-------+
| pPMA / / |nPMA |
| pPAA |/ |nPAA |
| pAR +---------------+nAR |
| +---------------+ |
+----\--+ +-------+
\
\
-------\--- ------------
//// \ \\\\//// \\\\
|| *---+++| ||
| | | | | |
| |MN| | | |
|| +---+++| ||
\\\\ ////\\\\ ////
----------- ------------
Figure 7: Tunnel Creation between nPMA and HA
Since the tunnel between pPMA and nPMA should not be there when the
mobile is nPoA, this tunnel should be deleted by the mobile just
before it moves to the nPoA. Figure 8 shows the tunnel deletion
procedure. In some cases, it is advisable to keep the tunnel on to
avoid the ping-pong effect.
At a certain threshold, the mobile finally ends up moving to the
nPoA. Based on the RA from the NAR, the mobile realizes that it is
in a new network, and changes its default router. But, since pre-
authentication and binding update have already been taken care of
ahead of time, the mobile does not need to go through the process of
access authentication. This will reduce the effective handoff time
and eventually the packet loss as well. Once the HA detects that the
mobile is already within nPMA, it can always delete the tunnel
between pPMA and HA.
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+-------+ +------+
| CN | | |
| \ | AAA |
+-------+\ +------+
\
\
+\-----+
| HA |
| |
*--\-\-*
\ \
\ \
\ \
\ \
+-----+ *-\-\-+
|pPMA + +nPMA |
|pPAA +--------------+nPAA |
|pAR + +nAR |
+-----+ +-----*
/
/ Tunnel Delete
/
------------ ---/-------
//// XXX\ / \\\
// // X\ \\
| | +--/-+| |
| | |MN | | |
| | | | | |
| \\+----+| //
\\ \\\ // ///
\\\\ ///-----------
------------
Figure 8: Tunnel deletion between pPMA and nPMA
This preauthentication technique can also be applicable to inter-
domain handoff scenario, wherep PMA and nPMA are in two different
domains. Thus there is a different HA designed for each Proxy
Mobility Agent. Details of inter-domain handoff are described in the
draft [I-D.taniuchi-netlmm-mpa-proxymipv6].
5.18. MPA for FMIPv6
There are some similarities between the techniques associated with
MPA and other related fast-handoff mecahnisms such as proactive part
of FMIPv6. Experimental results from both of these handoff
techniques demonstrate that these results are bounded by layer 2
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delay. However if these could be augmented by IEEE 802.21 network
discovery mechanism, layer 2 handoff delay can also be optimized.
This has been demonstrated in the accompanying draft
[I-D.ohba-mobopts-mpa-implementation]. On the other hand, certain
features of MPA could also be used to enhance the functionality of
FMIPv6 [RFC4068]. In particular, MPA's pre-authentication feature
for both layer-2 and layer-3, and stateful pre-configuration feature
can also be used for FMIPv6.
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6. Applicability of MPA
MPA is categorized as a proactive handover optimization mechanism.
In other words, MPA is more applicable where an accurate prediction
of movement can be easily made. For other environments, a special
care must be taken to deal with issues such as pre-authentication to
multiple CTNs (Section 5.2) and failed switching and switching back
(Section 5.9), however, addressing those issues in actual deployments
may not be easier.
Even if accurate prediction of movement is easily made, effectiveness
of MPA may be relatively reduced if the network employs network-
controlled localized mobility management in which the MN does not
need to change its IP address while moving within the network.
Effectiveness of MPA may also be relatively reduced if signaling for
network access authentication is already optimized for movements
within the network, e.g., when simultaneous use of multiple
interfaces during handover is allowed.
In other words, MPA is most viable solution for inter-administrative
domain predictive handover without simultaneous use of multiple
interfaces.
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7. Security Considerations
This document describes a framework of a secure handover optimization
mechanism based on performing handover-related signaling between a
mobile node and one or more candidate target networks to which the
mobile node may move in the future. This framework involves
acquisition of the resources from the CTN as well as data packet
redirection from the CTN to the mobile node in the current network
before the mobile node physically connects to one of those CTN.
Acquisition of the resources from the candidate target networks must
accompany with appropriate authentication and authorization
procedures in order to prevent unauthorized mobile node from
obtaining the resources. For this reason, it is important for the
MPA framework to perform pre-authentication between the mobile node
and the candidate target networks. The MN-CA key and the MN-AR key
generated as a result of successful pre-authentication can protect
subsequent handover signaling packets and data packets exchanged
between the mobile node and the MPA functional elements in the CTN's.
The MPA framework also addresses security issues when the handover is
performed across multiple administrative domains. With MPA, it is
possible for handover signaling to be performed based on direct
communication between the mobile node and routers or mobility agents
in the candidate target networks. This eliminates the need for a
context transfer protocol for which known limitations exist in terms
of security and authorization. [I-D.ietf-eap-keying]. For this
reason, the MPA framework does not require trust relationship among
administrative domains or access routers, which makes the framework
more deployable in the Internet without compromising the security in
mobile environments.
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8. IANA Considerations
This document has no actions for IANA.
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9. Acknowledgments
We would like to thank Farooq Anjum and Raziq Yakub for their review
of this document, and Subir Das for standardization support in the
IEEE 802.21 WG.
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10. References
10.1. Normative References
[RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)",
RFC 3748, June 2004.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[I-D.ietf-mobileip-lowlatency-handoffs-v4]
Malki, K., "Low Latency Handoffs in Mobile IPv4",
draft-ietf-mobileip-lowlatency-handoffs-v4-11 (work in
progress), October 2005.
[RFC4140] Soliman, H., Castelluccia, C., El Malki, K., and L.
Bellier, "Hierarchical Mobile IPv6 Mobility Management
(HMIPv6)", RFC 4140, August 2005.
[RFC4068] Koodli, R., "Fast Handovers for Mobile IPv6", RFC 4068,
July 2005.
[I-D.ietf-seamoby-card-protocol]
Liebsch, M., "Candidate Access Router Discovery",
draft-ietf-seamoby-card-protocol-08 (work in progress),
September 2004.
[I-D.ietf-seamoby-ctp]
Loughney, J., "Context Transfer Protocol",
draft-ietf-seamoby-ctp-11 (work in progress), August 2004.
[I-D.ietf-eap-keying]
Aboba, B., "Extensible Authentication Protocol (EAP) Key
Management Framework", draft-ietf-eap-keying-18 (work in
progress), February 2007.
[I-D.ietf-pana-pana]
Forsberg, D., "Protocol for Carrying Authentication for
Network Access (PANA)", draft-ietf-pana-pana-13 (work in
progress), December 2006.
Dutta (Ed.), et al. Expires September 6, 2007 [Page 48]
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[I-D.taniuchi-netlmm-mpa-proxymipv6]
Taniuchi, K., "Media Independent Pre-authentication
supporting fast-handoff in PMIPv6",
draft-taniuchi-netlmm-mpa-proxymipv6-00 (work in
progress), March 2007.
[I-D.kempf-netlmm-nohost-ps]
Kempf, J., "Problem Statement for IP Local Mobility",
draft-kempf-netlmm-nohost-ps-01 (work in progress),
January 2006.
[I-D.kempf-netlmm-nohost-req]
Kempf, J., "Requirements and Gap Analysis for IP Local
Mobility", draft-kempf-netlmm-nohost-req-00 (work in
progress), July 2005.
[RG98] ITU-T, "General Characteristics of International Telephone
Connections and International Telephone Circuits: One-Way
Transmission Time", ITU-T Recommendation G.114 1998.
[ITU98] ITU-T, "The E-Model, a computational model for use in
transmission planning", ITU-T Recommendation G.107 1998.
[ETSI] ETSI, "Telecommunications and Internet Protocol
Harmonization Over Networks (TIPHON) Release 3: End-to-end
Quality of Service in TIPHON systems; Part 1: General
aspects of Quality of Service.", ETSI TR 101 329-6 V2.1.1.
10.2. Informative References
[I-D.ietf-mobike-design]
Kivinen, T. and H. Tschofenig, "Design of the MOBIKE
Protocol", draft-ietf-mobike-design-08 (work in progress),
March 2006.
[I-D.ietf-hip-base]
Moskowitz, R., "Host Identity Protocol",
draft-ietf-hip-base-07 (work in progress), February 2007.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999.
[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Packet Loss Metric for IPPM", RFC 2680, September 1999.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
Delay Metric for IPPM", RFC 2681, September 1999.
Dutta (Ed.), et al. Expires September 6, 2007 [Page 49]
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[RFC1853] Simpson, W., "IP in IP Tunneling", RFC 1853, October 1995.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001.
[I-D.ietf-dhc-rapid-commit-opt]
Kim, P., Volz, B., and S. Park, "Rapid Commit Option for
DHCPv4", draft-ietf-dhc-rapid-commit-opt-05 (work in
progress), June 2004.
[I-D.ohba-mobopts-mpa-implementation]
Ohba, Y., "Media-Independent Pre-Authentication (MPA)
Implementation Results",
draft-ohba-mobopts-mpa-implementation-03 (work in
progress), October 2006.
[I-D.wakikawa-mobileip-multiplecoa]
Wakikawa, R., "Multiple Care-of Addresses Registration",
draft-wakikawa-mobileip-multiplecoa-05 (work in progress),
March 2006.
[I-D.ietf-nsis-qos-nslp]
Manner, J., "NSLP for Quality-of-Service Signaling",
draft-ietf-nsis-qos-nslp-12 (work in progress),
October 2006.
[I-D.sgundave-mipv6-proxymipv6]
Gundavelli, S., "Proxy Mobile IPv6",
draft-sgundave-mipv6-proxymipv6-00 (work in progress),
October 2006.
[SIPMM] Schulzrinne, H. and E. Wedlund, "Application Layer
Mobility Using SIP", ACM MC2R.
[CELLIP] Cambell, A., Gomez, J., Kim, S., Valko, A., and C. Wan,
"Design, Implementation, and Evaluation of Cellular IP",
IEEE Personal communication Auguest 2000.
[HAWAII] Ramjee, R., Porta, T., Thuel, S., Varadhan, K., and S.
Wang, "HAWAII: A Domain-based Approach for Supporting
Mobility in Wide-area Wireless networks", International
Conference on Network Protocols ICNP'99.
[IDMP] Das, S., Dutta, A., Misra, A., and S. Das, "IDMP: An
Intra-Domain Mobility Management Protocol for Next
Generation Wireless Networks", IEEE Wireless Communication
Magazine October 2000.
Dutta (Ed.), et al. Expires September 6, 2007 [Page 50]
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[I-D.ietf-mobileip-reg-tunnel]
Calhoun, P., Montenegro, G., Perkins, C., and E.
Gustafsson, "Mobile IPv4 Regional Registration",
draft-ietf-mobileip-reg-tunnel-09 (work in progress),
July 2004.
[YOKOTA] Yokota, H., Idoue, A., and T. Hasegawa, "Link Layer
Assisted Mobile IP Fast Handoff Method over Wireless LAN
Networks", Proceedings of ACM Mobicom 2002.
[MACD] Shin, S., "Reducing MAC Layer Handoff Latency in IEEE
802.11 Wireless LANs", MOBIWAC Workshop .
[SUM] Dutta, A., Zhang, T., Madhani, S., Taniuchi, K., Ohba, Y.,
and H. Schulzrinne, "Secured Universal Mobility",
WMASH 2004.
[SIPFAST] Dutta, A., Madhani, S., and H. Schulzrinne, "Fast handoff
Schemes for Application Layer Mobility Management",
PIMRC 2004.
[PIMRC06] Dutta, A., Ohba, Y., and H. Schulzrinne, "Dynamic
Buffering Protocol for Mobile", PIMRC 2006.
[MITH] Gwon, Y., Fu, G., and R. Jain, "Fast Handoffs in Wireless
LAN Networks using Mobile initiated Tunneling Handoff
Protocol for IPv4 (MITHv4)", Wireless Communications and
Networking 2003, January 2005.
[802.21] "Draft IEEE Standard for Local and Metropolitan Area
Networks: Media Independent Handover Services, IEEE
P802.21/D00.01,", A contribution to IEEE 802.21 WG ,
July 2005.
[802.11] "IEEE Wireless LAN Edition A compilation based on IEEE Std
802.11-1999(R2003)", Institute of Electrical and
Electronics Engineers September 2003.
[GPSIP] Dutta, A., "GPS-IP based fast-handoff for Mobiles", IEEE
Sarnoff Symposium 2006.
[MAGUIRE] Vatn, J. and G. Maguire, "The effect of using co-located
care-of-address on macro handover latency", 14th Nordic
Teletraffic Seminar 1998.
[mpa-mobike]
Mghazli, Y. and J. Bournelle, "MPA using IKEv2 and
MOBIKE", draft-yacine-preauth-ipsec-00 IETF.
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Authors' Addresses
Ashutosh Dutta
Telcordia Technologies
1 Telcordia Drive
Piscataway, NJ 08854
USA
Phone: +1 732 699 3130
Email: adutta@research.telcordia.com
Victor Fajardo
Toshiba America Research, Inc.
1 Telcordia Drive
Piscataway, NJ 08854
USA
Phone: +1 732 699 5368
Email: vfajardo@tari.toshiba.com
Yoshihiro Ohba
Toshiba America Research, Inc.
1 Telcordia Drive
Piscataway, NJ 08854
USA
Phone: +1 732 699 5305
Email: yohba@tari.toshiba.com
Kenichi Taniuchi
Toshiba America Research, Inc.
1 Telcordia Drive
Piscataway, NJ 08854
USA
Phone: +1 732 699 5308
Email: ktaniuchi@tari.toshiba.com
Dutta (Ed.), et al. Expires September 6, 2007 [Page 52]
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Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
USA
Phone: +1 212 939 7004
Email: hgs@cs.columbia.edu
Dutta (Ed.), et al. Expires September 6, 2007 [Page 53]
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Dutta (Ed.), et al. Expires September 6, 2007 [Page 54]
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