Network Working Group B. Lim
Internet-Draft C. Ng
Expires: August 23, 2008 K. Aso
Panasonic
February 20, 2008
Verification of Care-of Addresses in Multiple Bindings Registration
draft-lim-mext-multiple-coa-verify-01
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Abstract
Using multiple care-of address registration, there is a possibility
that a malicious mobile node could create multiple care-of address
bindings that does not belong to the mobile node at its home agent.
The home agent would accept these bindings without verifying them due
to the trust relationship it has with the mobile node. With these
bindings, the mobile node can launch attacks by asking the home agent
to flood the victims of these care-of addresses with useless packets.
To mitigate such a problem, this memo introduces a verification
mechanism that the home agent would use in order to verify the
care-of addresses for the mobile node before using them for packet
routing.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Scope . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Initiating the Attack . . . . . . . . . . . . . . . . . . 5
2.2. Launching the Attack . . . . . . . . . . . . . . . . . . . 6
3. Analysis: Possible Solution Approaches . . . . . . . . . . . . 8
4. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Applicable Scenario . . . . . . . . . . . . . . . . . 15
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 19
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1. Introduction
IP mobility allows a mobile node to maintain an ongoing communication
session regardless of where the mobile node roams in the Internet.
To achieve this constant connectivity, [1] permits the mobile node to
register a transient IP address (e.g. care-of address) at an
anchoring point (e.g. home agent). The mobile node sends a binding
update (BU) message to the home agent for registering its care-of
address. With this registration, the home agent could then forward
any packets addressed to the mobile node at the mobile node's care-of
address.
Security has always been a key consideration in user communications.
This is especially so in IP mobility where the mobile node frequently
changes its point of attachment. One such attack in IP mobility is
the registration of an invalid care-of address at the home agent.
Such registration allows the attacker to direct its traffic to other
nodes. Such an attack is previously ignored since the attacker can
only use one fake care-of address, thereby losing communications with
its home agent once the fake address is registered. However, [2]
permits the registration of multiple care-of addresses by means of
using an identification number called Binding Unique Identification
(BID) number to distinguish between multiple bindings to a home
address. Unless proper security methodologies are implemented, the
use of multiple care-of address registration heightens the chances of
allowing an invalid care-of address to be registered at the home
agent.
In Section 2, this document first expands on the problem briefly
described in [2] and [3] about the security threat with the binding
of fake care-of addresses. Next, possible approaches to mitigate
such threat is analyzed in Section 3.
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2. Problem Scope
For Mobile IPv6, it is assumed that the mobile node and its home
agent establish some form of mutual authentication such that the home
agent trusts the mobile node and will hence accept the registration
of any care-of address that the mobile node presents to the home
agent. This trust relationship is further strengthened when one
assume that ingress filtering is being used such that when the home
agent receives a binding update message from the mobile node stating
its care-of address as the source address, the home agent trusts that
the incoming packets do indeed originate from the specified source
address. In addition, the home agent also trusts the routing
infrastructure that packets forwarded by the home agent would be sent
to the intended destination.
However, such a trust is no longer valid when the mobile node
utilizes a single binding update message to register its multiple
care-of address at the home agent. This technique is explained in
[2] with the aim of introducing some optimization when registering
multiple care-of address for a mobile node. Such optimization
technique is useful in scenarios when resources (e.g. bandwidth) are
scarce on some of the mobile node's interfaces, since it allows the
mobile node to send a binding update message containing multiple
care-of address to the home agent from an interface that does not
have such resource constraint. Moreover, in Mobile IPv6, the use of
the alternate care-of address option permits the mobile node to
achieve the same effect of registering a care-of address for another
interface via a specific interface. This introduces the risk of
having fake care-of addresses registered at the home agent and
compromise the security of the network. One applicable sceanrio that
might encounter such a problem is the Long Term Evolution (LTE)
system that is being worked on by the Third Generation Partnership
Program (3GPP). Details on this scenario is shown in Appendix A.
There is a fundenmental difference between a mobile node using Mobile
IPv6 to flood a victim with useless packets and a mobile node using
Monami6 to flood a victim with useless packets. The difference lies
in that using Monami6, the mobile node can bind a real care-of
address at the home agent and use this care-of address to control the
flow of attacks to the victims (e.g. to increase the packet
transmission rate to the vicitm). In Mobile IPv6, the mobile node
loses this means of control as the mobile node can only refresh the
binding at the home agent. The example in Section 2.2 illustrates
the esclated threat of Monami6 in more details.
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2.1. Initiating the Attack
This problem is best understood through a specific example. Let us
assume that a malicious mobile node, MN, sends a binding update
message to its home agent, HA, to register multiple care-of
addresses. This is illustrated in the Figure 1 below.
[Start of packet header]
Source Address : CoA
Destination Address : HA's address
[Mobility Options]
Binding Unique Identifier: BID1
Binding Unique Identifier: BID2
Care-of Address : V1's address
Binding Unique Identifier: BID3
Care-of Address : V2's address
[End of packet header]
Figure 1: Binding Update Message for Multiple Care-of Addresses
Registration
CoA is a valid care-of address owned by MN. MN is attempting to bind
addresses of two victims, V1 and V2, at HA in order to launch an
attack towards the victims. The binding update message is secured
using an IPsec security association to protect the integrity and
authenticity.
When HA receives this binding update message, it will accept this
binding update message based on the following. First, the binding
update message is deemed authorized as the correct IPSec association
key is used for the message. Second, the trust relationship that HA
has with the routing infrastructure allows it to understand that this
binding update message is sent from MN. Finally, after the first two
checks have succeeded, the trust relationship that HA has with the MN
permits it to trust the care-of addresses that are specified in this
binding update message. Hence, the binding cache at HA will record
three bindings for MN tied to MN's home address (HoA) as shown in
Figure 2 below.
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Binding 1 [HoA, CoA , BID1]
Binding 2 [HoA, V1's address, BID2]
Binding 3 [HoA, V2's address, BID3]
Figure 2: Binding Cache at Home Agent
2.2. Launching the Attack
With the bindings created at HA, the malicious mobile node can now
attempt to flood the victims with useless packets. This type of
flooding can cause disruption of services at the victims' end as
their devices will be busy processing these packets for meaningless
data. This is illustrated in Figure 3.
+-----+
+----+ aaaa | |
| MN |------| I | +----+
+----+ | N | | CN |
| T | +----+
+----+ bbbb | E | a|b
| V1 |------| R | a|b
+----+ | N | aaaa +----+
| E |------| HA |
+----+ bbbb | T | bbbb +----+
| V2 |------| |
+----+ +-----+
Figure 3: Packet flooding attack scenario
The binding cache at HA contains MN's care-of address along with V1's
and V2's addresses. MN uses real-time transport protocol (RTP) and
real-time transport control protocol (RTCP) to initiate a video
stream from a streaming server (CN). Furthermore, MN could employ
flow filtering techniques to assist in the forwarding of packets from
HA. Such techniques are described in [4], [5] and [6].
Prior to starting the video flow, MN uses CoA to set filter rules at
HA. One of the filter rule would tell HA that the control packets
(shown as "a") for the video stream would be forwarded to BID1.
Another filter rule informs HA that the data packets (shown in "b")
for the video stream would be multicast to BID2 and BID3. When HA
receives packets from CN, it would adhere to the filter rules created
and forward the packets accordingly. This would cause V1 and V2 to
be flooded with unintended data packets. Furthermore, MN can utilize
care-of address1 to maintain the attack to V1 and V2 by sending
binding update message to constantly renew the lifetime of the
bindings. Likewise, MN can also use CoA1 to launch new attacks by
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binding more victim's addresses at HA and modifying the filter rule
to include them in the reception of the data packets.
Although both the home agent and the mobile node are mutually
authenticated, this does not stop an authenticated mobile node from
acting maliciously. Given time, the home agent might be able to
detect that the mobile node is acting maliciously and may then deny
mobility services to such a mobile node. One such way is when the
home agent starts receiving requests from those victims to stop
forwarding packets to it. With a substantial amount of such
requests, the home agent might launch an investigation to determine
if the mobile node was acting maliciously. Hence, we see that a home
agent might not be oblivious to such an attack.
However, even if the home agent bars a single identity, the attacker
may have multiple other identities available at his/her disposal.
Take for example an electronic mail (e-mail) account, an attacker can
create multiple e-mail accounts with same/different providers. Such
creation can be done at any location that provides terminals with
Internet connectivity (e.g. Internet cafe, Library) and does not
require the attacker to log-in his/her actual identity. Using these
multiple accounts, the attacker can start a spamming attack by
flooding victims with useless e-mails. The attacker knows that
eventually his/her account would get banned, but the attacker does
not care. The purpose of the attacker has been achieved and that is
to disrupt the services of those victims. Furthermore, the attacker
can continue to create more accounts to replace those accounts that
got banned. Thus, in this sense, having the identity known does not
hinder the above problem from occurring.
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3. Analysis: Possible Solution Approaches
Most of the soultions that will be described below assumes some form
of ingress filtering is performed on the source address of the packet
sent by the mobile node. Such assumption can be considered valid
when we take in account that most operators deploying the 4G cellular
networks would likely run ingress filtering within their networks as
a security precaution to reduce the chances of packet spoofing.
One obvious way to approach the problem described in Section 2 is for
the care-of addresses to be formed using the cryptographically
generated addresses (CGA) technique [7]. With CGA in place, it
permits the home agent to know if the mobile node actually owns that
particular care-of address listed in the binding update message.
Thus, the mobile node would be unable to bind fake care-of addresses
at the home agent. However, introducing cryptographically generated
care-of addresses increases the complexity of the mechanism to
achieve multiple bindings. It is unclear how a message can contain
multiple CGA signatures for each of the care-of addresses.
Furthermore, complexity is increased by the fact that additional
addresses are not found in the source address field but somewhere in
the extension header of the packet (i.e. mobility header). This
requires substantial integration between the CGA module and Mobility
Support module in a network stack implementation. Additionally, each
CGA Parameters structure which is at least 72 octets in length must
be added to the binding update message, further increasing its size.
Finally, the method of using CGA does not prevent the malicious
mobile node to launch a flooding attack against a subnet by
generating multiple non-existent care-of addresses in that subnet
using the mobile node's own public keys.
Another approach to the problem, as described in [8], is to use an
established symbiotic relationship between a mobile node and an
access router in order to permit the home agent to verify the care-of
address of the mobile node. The purpose of the symbiotic
relationship between the access router and the mobile node allows the
access router to act on behalf of the mobile node when it comes to
validating the care-of address that the mobile node is using to the
mobile node's home agent. The mobile node will tell its home agent
of such symbiotic relationship establishment by providing the IP
address of access router for the home agent to contact. This prompts
the home agent to contact the access router to verify the care-of
address that the mobile node claims to be using. Such message
exchanges between the mobile node, home agent and access router are
secured via public keys methodology which provides the proof to the
home agent regarding the mobile node's care-of address. However, the
requirement to include an access router role into such care-of
address validation adds complexity to the access router. This is
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especially so if the access router has a number of mobile nodes
associated to it that requires such validation services. This
implies that the access router would have to check and respond to the
respective home agents on behalf of all these mobile nodes. Such
action might significantly increase the processing load of the access
router where such processing capabilities could be channeled towards
more meaningful tasks such as packet routing, which is the primary
purpose of an access router.
Another way to reduce the effect of the problem is to introduce some
policy at the home agent to limit the amount of care-of addresses
that a mobile node can bind. This limitation typically restricts a
malcious mobile node from binding too many fake care-of addresses at
the home agent, thus cuts down on the number of victims that a mobile
node can affect. However, this approach does not stop the malcious
mobile node from binding fake care-of addresses at the home agent.
The intend of this approach is to control the after effect (e.g.
mobile node triggering re-direction attack to vicitms), thereby
isolating the problem to only a few victims rather than the whole
system. Hence, this approach does not solve the problem.
Another alternative to solve the problem could employ the credit-
based authorization (CBA) technique described in [9]. Here, the home
agent uses the credits associated to an unverified binding to forward
packets via that specific routing path. If that unverified binding
does not have enough credits left, the home agent would not forward
packets using that path as long as that binding remains unverified.
The binding is verified when the home agent receives a packet from
the mobile node using that care-of address as source. This technique
limits the problem of packet flooding to a victim as it restricts the
amount of data that can be transferred. For the home agent to fully
utilize an unverified care-of address for packet routing the home
agent would need to receive a packet from the unverified care-of
address. With the reception of a packet from the unverified care-of
address, this proves to the home agent that such a care-of address is
addressable. However, the packets that the home agent receives from
these unverified care-of address might not be sent by the mobile
node. For example, it is possible that a malicious mobile node uses
the Internet Control Message Protocol (ICMP) described in [10] to
send a request message via its home address to unverified care-of
address. If this unverified care-of address belongs to a victim, the
reception of an ICMP request might trigger a response from the
victim. Hence, the victim sends a response to the home address
which, would be received at the home agent. With the reception of a
packet from an unverified care-of address, the home agent would
assume that the packet is sent by the mobile node. Thus, this
verifies that care-of address for packet routing at the home agent.
Also, in situations where an interface of the mobile node has
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asymmetrical link characteristics (e.g. General Packet Radio
System), that particular interface might have resource constraint on
its upload path. Thus, such a constraint may make it costly for a
mobile node to send a packet to its home agent using that particular
interface.
Alternatively, the problem may be tackled by having the home agent
send some encrypted information to the mobile node via the unverified
care-of address and expects the mobile node to return the decrypted
version of the information. This technique is described in [11]
where the use of a cookie proves to the home agent that the mobile
node is addressable at the specified care-of address. However, the
optimization benefit of sending multiple care-of address within a
single binding update is greatly reduced as it would require the
mobile node to respond via all these care-of addresses. In this
case, the mobile node might as well send the binding update message
individually for each care-of address.
To optimize the inefficiency of using [11] for multiple care-of
addresses case, it is possible for the home agent to send a
notification to a mobile node via one unverified care-of address and
ask the mobile node to respond to the reception of the notification
via another care-of address. This utilizes the concept of multiple
care-of addresses whereby the mobile node need not respond back using
the same path as the reception of the request. Such a concept is
particularly useful in the event that the mobile node has several
unverified care-of addresses that needs to be tested. By asking the
mobile node to respond via another unverified care-of address, in one
round trip time, the home agent would be able to verify two care-of
addresses. Figure 4 illustrates this.
+-----+
| |
CoA1 ______| I |
/ | N |
Cellular/ | T |
+----+ CoA2 | E | +----+
| MN |------| R |----| HA |
+----+ GPRS | N | +----+
WLAN\ | E |
\_______| T |
CoA3 | |
+-----+
Figure 4: Operation of Home Agent
In Figure 4, the mobile node MN has three interfaces. A first
interface associates with the cellular system and uses a care-of
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address CoA1 for communication. A second interface connects to the
General Packet Radio System (GPRS) and uses a care-of address CoA2
for communication. A third interface associates with the 802.11
Wireless Local Area Network (WLAN) and uses a care-of address CoA3
for communication. MN sends a binding update message from CoA1 that
is attempting to register all its care-of addresses at its home
agent, HA. Thus, when HA receives the binding update message, it
binds CoA1 in its binding cache as a valid routing path to MN as it
has proven to HA that MN is using that care-of address. However, for
CoA2 and CoA3, HA would need to verify their addressability before
using them for packet routing. Hence, HA uses the notification to
verify both of these care-of addresses.
It is possible for the home agent to choose when to perform such
verification process for the mobile node's bindings. One way is to
have the home agent trigger the verification process immediately upon
the reception of binding update message registering multiple care-of
address from a mobile node. This is mostly helpful when it comes to
supporting the concept of registering multiple care-of addresses.
The purpose of having multiple care-of addresses is to allow the home
agent to route packets to the mobile node via any of the multiple
paths. Having the home agent perform the verification process
immediately permits the home agent to quickly utilize all of the
mobile node's care-of addresses for packet routing. For example,
when the home agent receives the binding update message on CoA1 that
specifies the binding of both CoA2 and CoA3, the home agent can
choose to immediately verify these care-of addresses in order to
start using them for packet routing to the mobile node.
Another way could be that the home agent triggers the verification
process just before it needs to use an unverified routing path to the
mobile node. This is especially so in the event that the mobile node
sets a filter rule at the home agent specifying the routing of
certain packets via the unverified routing path. When the home agent
receives packets that match the filter rule condition, the home agent
would trigger the verification process for the unverified path prior
to using it. An example would be that the mobile node specify in a
filter rule at the home agent that data packets would be routed via
CoA3. When the home agent receives such a packet, it notes that CoA3
has yet been verified. Thus, the home agent performs the
verification process to verify CoA3.
Also, the transmission path of the notification packet from the home
agent can vary based on how strict the security policy is enforced.
Strict security policy can forbid the home agent in using an
unverified care-of address for any packet routing. In this sense,
the home agent can only send the notification to the mobile node via
a verified care-of address. Such policies are beneficial in
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deterring any such flooding attacks being launch from the mobile
node. For example, since CoA1 is the only verified care-of address
to the mobile node, the home agent would send a message via CoA1 to
notify the mobile node to respond back via CoA2. This action will
cause the mobile node to understand that the home agent is trying to
verify CoA2. Hence, the mobile node would send a packet to the home
agent via CoA2, thereby proving to the home agent that it is
addressable at CoA2.
On the other hand, if the home agent employs techniques such as CBA,
it permits the home agent to route packets to the mobile node via an
unverified care-of address. These packets would be limited to the
amount of credits associated to that particular binding. The
advantage of using an unverified path to transmit the notification is
that it allows the home agent to verify at best two unverified
care-of addresses. This is especially useful in the event that the
mobile node has several unverified care-of addresses that needs to be
tested. An example would be that the home agent sends a message via
CoA2 to notify the mobile node to respond back via CoA3. This action
allows the mobile node to understand that the home agent is trying to
verify both CoA2 and CoA3. Hence, the mobile node would send a
packet to the home agent via CoA3, thereby proving to the home agent
that it is addressable at both CoA2 and CoA3.
Furthermore, it is possible that the home agent does not specify a
return unverified care-of address when it notifies the mobile node.
This would allow the mobile node to respond back to the home agent
via any of the mobile node's care-of address. By permitting the
mobile node to choose the respond path to the home agent, it supports
the situation where the uplink path maybe resource constraint (e.g.
limited uplink bandwidth). In the first place, this could be the
reason why the mobile node decides to send a single binding update
message to bind its multiple care-of address from a path that does
not limit its resources. For example, the home agent wants to verify
that CoA2 is addressable to the mobile node. Thus, the home agent
notifies the mobile node via CoA2 to verify this care-of address.
Since GPRS has limited uplink bandwidth, the mobile node decides to
send the respond via the cellular path (CoA1). Hence, upon receiving
the respond from the mobile node, the home agent is able to verify
that the mobile node is addressable at CoA2.
Finally, how the notification information is carried to the mobile
node may differ at the home agent. One possible way is that such
notification is carried using a dedicated message format. This makes
the notification packet small in size and easily recognized by the
mobile node. On the other hand, since the notification is specifying
just a care-of address that the mobile node should respond back by,
an optimization to this would be to have the notification to be
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tagged to packets that are being sent to the mobile node. One
example could be the binding acknowledgment message that the home
agent replies to the mobile node. Another example could be data
packets that are addressed to the mobile node. By tagging it to
existing packets, the home agent saves on the overhead incurred from
the transmission the notification packet to the mobile node.
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4. Conclusion
This draft explains that the use of multiple care-of address
registration breaks the trust relationship between a home agent and a
mobile node. With this relationship broken, it permits a malicious
mobile node to bind multiple victims' care-of addresses at the home
agent. With these bindings, the mobile node can launch attacks by
flooding the victims with useless packets. To reduce the chances of
having such a situation, we briefly analyse a few possible solutions
that would be able to solve the problem. Base on the result of the
analysis, we observed that a potential way to approach the problem in
the multiple care-of address scenario is for the home agent send a
message to the mobile node via one care-of address path and ask the
mobile node to respond via another care-of address path. This
technique not only allows the home agent to know that the mobile node
owns the care-of address, but it further optimize the the amount of
messages that the home agent needs to send in order to verify the
mobile node's care-of addresses.
5. Security Considerations
This draft mentions new security requirements when implementing
Multiple Care-of Address Registration [2].
6. IANA Considerations
TBD
7. References
7.1. Normative References
[1] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[2] Wakikawa, R., "Multiple Care-of Addresses Registration",
draft-ietf-monami6-multiplecoa-05 (work in progress),
January 2008.
7.2. Informative References
[3] Montavont, N., "Analysis of Multihoming in Mobile IPv6",
draft-ietf-monami6-mipv6-analysis-04 (work in progress),
July 2007.
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[4] Soliman, H., "Flow Bindings in Mobile IPv6 and Nemo Basic
Support", draft-soliman-monami6-flow-binding-04 (work in
progress), March 2007.
[5] Larsson, C., "A Filter Rule Mechanism for Multi-access Mobile
IPv6", draft-larsson-monami6-filter-rules-02 (work in
progress), March 2007.
[6] Mitsuya, K., "A Policy Data Set for Flow Distribution",
draft-mitsuya-monami6-flow-distribution-policy-04 (work in
progress), August 2007.
[7] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
[8] Haddad, W., "Care-of Address Test for MIPv6 using a State
Cookie", draft-haddad-mext-enhanced-reachability-test-00 (work
in progress), February 2008.
[9] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route
Optimization for Mobile IPv6", RFC 4866, May 2007.
[10] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, September 1981.
[11] Dupont, F. and J. Combes, "Care-of Address Test for MIPv6 using
a State Cookie", draft-dupont-mipv6-rrcookie-04 (work in
progress), January 2007.
Appendix A. Applicable Scenario
The shift in the cellular system to utilize the Internet Protocol
(IP) for communication and signaling implies the need for supporting
IP mobility. For cellular operators, it means that a home agent
would be located within their cellular system in order to support the
mobile IP signaling (e.g. binding update) to their subscribers'
mobile nodes. Within the cellular system, the establishment of a
trust relationship between the operator and subscribers allows
operators to provide services to subscribers. For example, the
network would trust that the user operating a mobile node is the
genuine subscriber and not someone who has stolen the subscriber's
identity. To strength this trust relationship, operators uses the
Authentication, Authorization, and Accounting (AAA) protocol within
their system to authenticate their subscribers before providing
services to them. Furthermore, a business contract (e.g. terms and
condition) between the operator and subscribers binds subscribers to
obey the rules dictated by the operator when using the services
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provided by the operator. Using the terms and conditions, an
operator is able to terminate services to a subscriber if the
operator deems that the subscriber is acting maliciously. Figure 5
below illustrates the cellular scenario.
+----+
| HA |
+----+
||
+=======+ +=======+
/ 3GPP \ / Non 3GPP\
\ Network / \ Network /
+=======+ +=======+
\ /
CoA.3G \ / CoA.Non-3G
+----+
| MN |
+----+
Figure 5: 3GPP scenario
In this scenario, a mobile node (MN) has two interfaces. A first
interface is associated to a 3GPP network (e.g. 3G cellular) and uses
CoA.3G for communication. A second interface is associated to a non-
3GPP network (e.g. Wireless Local Area Network) and uses CoA.Non-3G
for communication. The home agent in this scenario is part of the
3GPP network and might trust the validity of any packets sent with a
source address configured in the 3GPP network. Thus, if MN sends a
binding update message to HA with the source address as CoA.3G, HA
would accept this binding as a valid route to the MN. However, this
binding update message could further contain a request for HA to bind
CoA.Non-3G.As HA trusts the packet with a source address CoA.3G, this
implies that HA would trust its content, which in this case is the
binding request for CoA.Non-3G. Hence, HA would bind CoA.Non-3G as a
valid routing path to the MN even though the path has not been
verified. This might incur the problem of a malicious MN using the
HA to flood a victim with useless packets.
Similarly, in the event that the binding update message contains a
mixture of care-of addresses that are trusted and not trusted by the
home agent, the home agent could identify those trusted care-of
addresses and omit performing the verification process for such
addresses. When binding of a care-of address that is trusted by the
home agent, the verification process could be skipped and the state
of such a binding would immediately be set to the verified state.
The reason that the home agent trusts this care-of address could be
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that the home agent understands that the prefix used to create the
care-of address is unique to the mobile node. Another reason could
be that the care-of address is assigned by a trusted address
allocation server (e.g. DHCP server). To be able to distinguish
between trusted and non-trusted care-of addresses, policies could be
installed at the home agent to assist in such identification process.
If the home agent receives a binding update message that has a
mixture of care-of addresses that are trusted and not trusted by the
home agent, using the policy, the home agent would then be able to
identify which care-of address requires verification and which does
not. This reduces the chance of the home agent having to perform
redundant care-of address verification on those trusted care-of
address.
Appendix B. Change Log
o draft-lim-mext-multiple-coa-verify-01:
* Reference lastest MCoA draft that specify the problem.
* Added two more soultions (limiting care-of address binding at
HA and CoA test using 'symbiotic' relationship) for analysis in
Section 3.
o draft-lim-mext-multiple-coa-verify-00:
* Initial version.
Authors' Addresses
Benjamin Lim
Panasonic Singapore Laboratories Pte Ltd
Block 1022 Tai Seng Ave #06-3530
Tai Seng Industrial Estate
Singapore 534415
SG
Phone: +65 65505478
Email: benjamin.limck@sg.panasonic.com
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Chan-Wah Ng
Panasonic Singapore Laboratories Pte Ltd
Blk 1022 Tai Seng Ave #06-3530
Tai Seng Industrial Estate
Singapore 534415
SG
Phone: +65 65505420
Email: chanwah.ng@sg.panasonic.com
Keigo Aso
Matsushita Electric Industrial Co. Ltd. (Panasonic)
5-3 Hikarino-oka
Yokosuka, Kanagawa 239-0847
JP
Phone: +81 46 840 5123
Email: asou.keigo@jp.panasonic.com
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