Mobility Optimizations: MIPSHOP WG W. Haddad
Internet-Draft S. Krishnan
Expires: January 9, 2008 Ericsson Research
F. Dupont
CELAR
July 8, 2007
Mobility Signaling Delegation
draft-haddad-mipshop-mobisig-del-03
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Copyright (C) The IETF Trust (2007).
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Abstract
This memo describes a mechanism which delegates the exchange of
mobility signaling messages between the mobile and correspondent
nodes to the network infrastructure. Goals outlining the proposed
delegation are to further reduce the IP handoff latency and to
relieve the mobile node from exchanging a considerable amount of
signaling messages with correspondent nodes while retaining full
control on the critical ones.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Suggested Solution . . . . . . . . . . . . . . . . . . . . . . 7
5. New Options and Messages . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Introduction
Optimized Mobile IPv6 (OMIPv6) protocol (described in [OMIPv6])
provides a mechanism, which allows significant reduction in the
amount of signaling messages generated by the Mobile IPv6 protocol
([MIPv6]), a shorter handoff latency and a better overall security.
However, a care-of address (CoA) test exchange between the mobile
node (MN) and each correspondent node (CN) remains a compulsory step
prior to exchanging critical mobility signaling messages between
them, namely binding updates (BU) and acknowledgments (BA) messages.
The CoA reachability test involves two mobility signaling messages
(CoTI/CoT) and is unaffected by the optimization introduced by OMIPv6
protocol.
This memo describes a mechanism which delegates the exchange of
mobility signaling messages between the MN and CN(s) to the network
infrastructure, as part of the ongoing work on designing an
optimization to the IPv6 secure neighbor discovery (described in
[SeND]) protocol. Goals outlining the proposed delegation are to
further reduce the IP handoff latency and to relieve the MN from
exchanging a considerable amount of signaling messages with each CN
while retaining full control on the BU/BA messages.
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2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [TERM].
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3. Motivation
OMIPv6 protocol achieves three different goals: it alleviates the
mobility signaling messages load, improves the overall security and
reduces the IP handoff latency.
The latency reduction caused by OMIPv6 is mainly due to eliminating
the MN's home address reachability test, which requires a signaling
message exchange through the MN's Home Agent (HA). Another set of
factors (excluding the link layer), e.g., network detection, network
prefix discovery and IP address configuration are still among the
main contributors to the handoff latency. These factors remain
totally unaffected by using OMIPv6.
In addition, OMIPv6 still require a CoA reachability test with each
CN, prior to updating them with its new CoA (nCoA), i.e., exchanging
BU/BA messages. Consequently, such exchange guarantees a residual
latency and additional mobility signaling messages.
Furthermore, it is important to mention that a fast growing class of
mobile devices tend to have very limited battery power. Thus, the
available energy must be meticulously controlled and consumed, i.e.,
not to be wasted on exchanging non-critical signaling messages. Such
requirement becomes more challenging when the MN is talking to
different CNs at the same time (which may probably be a very common
case) while moving fast.
In fact, it has been shown that the wireless transmission of one bit
can require over 1000 times more energy than a single 32-bit
computation [EALDC]. Consequently, a fast moving MN communicating
with multiple CNs will have to dedicate a significant amount of its
available energy to exchange only mobility signaling messages with
the CNs.
OMIPv6 provides a credit-based Authorization (CBA) mechanism, which
aims to reduce further the latency caused by the care-of address test
exchange. However, such mechanism has two drawbacks: the CN may not
provide this feature, in which case the latency problem remains
unsolved, and it consumes battery power in both scenarios due to
exchanging signaling messages (i.e., as they get only delayed).
Note that the suggested protocol does not prevent both endpoints from
using the CBA mechanism on top of the suggested protocol.
On the other side, the Optimized Secure Neighbor Discovery protocol
(described in [OptiSeND]) is an ongoing work, which aims to better
adapt the requirements for securing the IPv6 neighbor discovery to
low computation and battery power devices (e.g., mobile devices and
sensors). OptiSeND enables fixed/mobile nodes to avoid using
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expensive RSA signatures to secure neighbor discovery messages
exchange by providing a mechanism to quickly share a long lifetime
symmetric key with the AR(s). On the infrastructure side, OptiSeND
enables ARs to use one-way hash chains to authenticate the Router
Advertisement (RtAdv) messages sent to the fixed/mobile node(s)
attached to the same link.
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4. Suggested Solution
Our proposal delegates the task of performing CoA reachability
test(s) to the network infrastructure, which in turn enables
eliminating the residual latency due to the CoA rechability test,
ensures that the messages exchanged are authenticated and optimizes
the battery power consumption by relieving the MN from performing CoA
reachability tests. In fact, our protocol adopts another approach to
perform reachability tests, which consists on testing the
reachability of the new MN's 64-bit subnet prefix only instead of
testing the reachability of the whole nCoA, and thus relies on two
new messages to perform such test.
For these purposes, the MN must securely send to the access network
infrastructure necessary information (called mobility package) to
enable performing the CoA reachability test(s) on its behalf and to
forward the mobility package to potential new ARs (nARs). To achieve
this goal, a new message called "Router Mobility Solicitation"
(RtMoSol) is used by the MN to send its mobility package to its
current AR(s). The RtMoSol message MUST carry all CNs'IPv6 addresses
and the MN's IPv6 home address(es) (HoAs) and MUST be authenticated
with the shared key obtained from OptiSeND.
Upon receiving a valid RtMoSol message, the selected AR SHOULD reply
with an authenticated unicast "Router Mobility Acknowledgment"
(RtMAck) message. The RtMoSol message content SHOULD be forwarded to
neighboring ARs and should be stored together with data obtained from
running OptiSeND protocol.
The RtMoSol message is also used by the MN to add or delete entries
from a mobility package stored in the AR cache memory. For example,
when the MN establishes a session with a new CN, it SHOULD send a
RtMoSol message to its current AR and SHOULD set a new bit (called
Add "A" bit) to request the AR to forward the new CN's IPv6 address
to potential new AR(s). Similarily, the MN MAY also set another bit
(called Suppress "S" bit) to request the AR(s) to remove an existing
CN's IPv6 address from its list.
In order to eliminate the residual latency due to performing the CoA
reachability test, the nAR SHOULD perform the test immediately after
receiving a first hint (e.g., on layer 2) indicating an attachment of
the MN (e.g., when using [FRD]) and SHOULD forward the message(s)
sent by the CN(s) to the MN after it attaches to the nAR. For this
purpose, the nAR SHOULD use its source address, which includes the
prefix advertised on the link and MUST authenticate the message with
a mobility signaling key (Kms). We call such message "Prefix Test
Init" (PreTI). In addition, the PreTI message MUST carry the MN's
HoA to allow the CN to fetch/generate the Kms associated with the
corresponding Binding Cache Entry (BCE) in order to validate the
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message authenticity.
Upon receiving a valid PreTI message, the CN computes a prefix keygen
(prekey) token from the prefix used in the IPv6 source address and
the long lifetime shared secret (i.e., kbmperm) generated from using
OMIPv6 protocol. After computing the token, the CN SHOULD send back
an acknowledgment message called "Prefix Test" (PreT), which carries
the prekey token to the same IPv6 source address carried in the PreTI
message. The PreT message MUST also carry the MN's HoA and MUST be
authenticated with Kms.
The Prekey token MUST be computed by the CN in the following way:
Prekey Token = First [64, SHA1 (SA_Prefix | nonce | SHA1 (Kbmperm))]
Where SA_Prefix is the 64-bit prefix included in the IPv6 source
address sent in the PreTI message and Kbmperm is the long lifetime
shared secret generated by the CN when running OMIPv6 protocol.
As mentioned above, the prefix reachability test SHOULD be
authenticated with Kms. In order to do so, Kms SHOULD be computed
from using the symmetric key generated from running OptiSeND protocol
and the MN's HoA, and MUST be send encrypted to each CN. One way to
achieve a confidential transmission of Kms is to send it encrypted in
the first BU message sent by the MN. In such scenario, the MN will
use its Kbm (computed from running the return routability procedure)
to encrypt Kms. Finally, Kms will be carried in a new option called
signaling delegation (SID).
Upon receiving a BU message carrying a SID option, the CN decrypts
Kms and stores it in the MN's corresponding BCE. All subsequent
reachability test messages SHOULD be sent by the MN's current AR on
behalf of the MN and SHOULD be authenticated with Kms.
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5. New Options and Messages
TBD
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6. Security Considerations
This draft proposes a scheme to delegate mobility signaling from the
mobile node to the network infrastructure. Since the network
infrastructure nodes are well known and trustworthy, it makes
firewalling easier at the administrative boundaries. Also, since the
network infrastructure nodes are likely to have more resources than
mobile nodes, this scheme will allow us to use higher strength crypto
to protect the signaling. This draft does not introduce any new
security holes into existing route optimization solutions.
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7. References
7.1. Normative References
[MIPv6] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[OMIPv6] Vogt, C., Arkko, J., and W. Haddad, "Enhanced Route
Optimization for Mobile IPv6", RFC 4866, June 2006.
[SeND] Arkko, J., Kempf, J., Sommerfield, B., Zill, B., and P.
Nikander, "Secure Neighbor Discovery (SeND)", RFC 3971,
March 2005.
[TERM] Bradner, S., "Key Words for Use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP , March 1997.
7.2. Informative References
[EALDC] Barr, K. and K. Asanovic, "Energy Aware Lossless Data
Compression", ACM Proceedings of MobiSys, May 2003.
[FRD] Choi, J., Shin, D., and W. Haddad, "Fast Router Discovery
with L2 Support", Internet
Draft, draft-ietf-dna-frd-01.txt, June 2006.
[OptiSeND]
Haddad, W., Krishnan, S., and J. Choi, "Secure Neighbor
Discovery (SeND) Optimization: The OptiSeND Protocol",
Internet Draft, draft-haddad-mipshop-optisend-03.txt,
July 2007.
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Authors' Addresses
Wassim Haddad
Ericsson Research
Torshamnsgatan 23
SE-164 80 Stockholm
Sweden
Phone: +46 8 4044079
Email: Wassim.Haddad@ericsson.com
Suresh Krishnan
Ericsson Research
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900
Email: Suresk.Krishnan@ericsson.com
Francis Dupont
CELAR
Email: Francis.Dupont@fdupont.fr
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