NEMO Working Group C. Ng
Internet-Draft Panasonic Singapore Labs
Expires: January 5, 2006 P. Thubert
Cisco Systems
M. Watari
KDDI R&D Labs
F. Zhao
UC Davis
July 4, 2005
Network Mobility Route Optimization Problem Statement
draft-ietf-nemo-ro-problem-statement-00
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
With current Network Mobility (NEMO) Basic Support, all
communications to and from Mobile Network Nodes must go through the
bi-directional tunnel established between the Mobile Router and Home
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Agent when the mobile network is away. This results in various
inefficiencies associated with packet delivery. This document
investigates such inefficiencies, and provides for the motivation
behind Route Optimization (RO) for NEMO.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. NEMO Route Optimization Problem Statement . . . . . . . . . . 4
2.1 Sub-Optimality with NEMO Basic Support . . . . . . . . . . 4
2.2 Bottleneck in Home Network . . . . . . . . . . . . . . . . 6
2.3 Amplified Sub-Optimality in Nested Mobile Networks . . . . 6
2.4 Sub-Optimality with Combined Mobile IPv6 Route
Optimization . . . . . . . . . . . . . . . . . . . . . . . 8
2.5 Security Policy Prohibiting Traffic From Visiting Nodes . 8
2.6 Instability of Communications within a Nested Mobile
Network . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.7 Deadlock with a Home Agent Nested in a Mobile Network . . 10
3. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1 Normative Reference . . . . . . . . . . . . . . . . . . . 12
7.2 Informative Reference . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13
A. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 14
B. Various configurations involving Nested Mobile Networks . . . 15
B.1 CN located in the fixed infrastructure . . . . . . . . . . 15
B.1.1 Case A: LFN and standard IPv6 CN . . . . . . . . . . . 16
B.1.2 Case B: VMN and MIPv6 CN . . . . . . . . . . . . . . . 16
B.1.3 Case C: VMN and standard IPv6 CN . . . . . . . . . . . 16
B.2 CN located in distinct nested NEMOs . . . . . . . . . . . 17
B.2.1 Case D: LFN and standard IPv6 CN . . . . . . . . . . . 18
B.2.2 Case E: VMN and MIPv6 CN . . . . . . . . . . . . . . . 18
B.2.3 Case F: VMN and standard IPv6 CN . . . . . . . . . . . 18
B.3 CN and MNN located in the same nested NEMO . . . . . . . . 19
B.3.1 Case G: LFN and standard IPv6 CN . . . . . . . . . . . 20
B.3.2 Case H: VMN and MIPv6 CN . . . . . . . . . . . . . . . 21
B.3.3 Case I: VMN and standard IPv6 CN . . . . . . . . . . . 21
B.4 CN located behind the same nested MR . . . . . . . . . . . 22
B.4.1 Case J: LFN and standard IPv6 CN . . . . . . . . . . . 22
B.4.2 Case K: VMN and MIPv6 CN . . . . . . . . . . . . . . . 23
B.4.3 Case L: VMN and standard IPv6 CN . . . . . . . . . . . 23
Intellectual Property and Copyright Statements . . . . . . . . 24
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1. Introduction
With current Network Mobility (NEMO) Basic Support [1], all
communications to and from nodes in a mobile network must go through
the bi-directional tunnel established between the Mobile Router and
its Home Agent when the mobile network is away. Although such an
arrangement allows Mobile Network Nodes to reach and be reached by
any node on the Internet at all time, limitations associated to the
base protocol degrade overall performance of the network, and,
ultimately, can prevent all communications to and from the Mobile
Network Nodes.
Some of these concerns already exist with Mobile IPv6 [2] and were
addressed by the mechanism known as Route Optimization, which is part
of the base protocol. With Mobile IPv6, Route Optimization mostly
improves the end to end path between Mobile Node and Correspondent
Node, with an additional benefit of reducing the load of the Home
Network, thus its name.
NEMO Basic Support presents a number of additional issues, making the
problem more complex, so it was decided to address Route Optimization
separately. In that case, the expected benefits are more dramatic,
and a Route Optimization mechanism could enable connectivity that
would be broken otherwise. In that sense, Route Optimization is even
more important to NEMO Basic Support than it is to Mobile IPv6.
This document explores limitations inherent in NEMO Basic Support,
and their effects on communications between a Mobile Network Node and
its corresponding peer. This is detailed in Section 2. It is
expected for readers to be familiar with general terminologies
related to mobility in [2][3], NEMO related terms defined in [4], and
NEMO goals and requirements [5].
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2. NEMO Route Optimization Problem Statement
In essence, the goal of Route Optimization in NEMO is to reduce
limitations and sub-optimalities introduced by the bi-directional
tunnel between a Mobile Router and its Home Agent (also known as the
MRHA tunnel). In the following sub-sections, we will describe the
effects of sub-optimal routing with NEMO Basic Support, how it may
cause a bottleneck to be formed in the home network, and how these
get amplified with nesting of mobile networks. Closely related to
nesting, we will also look into the sub-optimality even when Mobile
IPv6 Route Optimization is used over NEMO Basic Support. This is
followed by a description of security policy in home network that may
forbid transit traffic from Visiting Mobile Nodes in mobile networks.
In addition, we will explore the impact of MRHA tunnel on
communications between two Mobile Network Nodes on different links of
the same mobile network. We will also provide additional motivations
for Route Optimization by considering the potential deadlock
situation when a Home Agent is part of a mobile network.
2.1 Sub-Optimality with NEMO Basic Support
With NEMO Basic Support, all packets sent between a Mobile Network
Node and its Correspondent Node are forwarded through the MRHA
tunnel, resulting in a sub-optimal path between the two nodes. This
sub-optimality has the following undesirable effects:
o Longer route leading to increased delay and additional
infrastructure load
Because a packet must transit from a mobile network to the Home
Agent then to the Correspondent Node, the transit time of the
packet is usually higher than if the packet were to go straight
from the mobile network to the Correspondent Node. In the best
case, where the Correspondent Node (or the mobile network) resides
near the Home Agent, the increase in packet delay is minimal. In
the worst case, where the mobile network and the Correspondent
Node are relatively near to one another but far away from the Home
Agent on the Internet, the increase in delay is tremendous.
Applications such as real-time multimedia streaming may not be
able to tolerate such increase in packet delay.
Moreover, by using a longer route, the total resource utilization
for the traffic would be much higher than if the packets were to
follow a direct path between the Mobile Network Node and
Correspondent Node. This would result in additional load in the
infrastructure.
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o Increased packets overhead
The encapsulation of packets in the MRHA tunnel results in
increased packet size due to addition of an outer header. This
reduces the bandwidth efficiency, as IPv6 header can be quite
substantial relative to the payload for applications such as voice
samples. For instance, consider a voice application using a 8kbps
algorithm (e.g. G.729) and taking a voice sample every 20ms (as
in RFC 1889). The packet transmission rate will be 50 packets per
second. IPv6/UDP/RTP header cause an overhead of 384 bits (i.e.
19200bps of overhead). Each additional IPv6 header is an extra
16kpbs, which is twice the actual payload.
o Increased processing delay
The encapsulation of packets in the MRHA tunnel also results in
increased processing delay at the points of encapsulation and
decapsulation. Such increased processing may include encryption/
decryption, topological correctness verifications, MTU
computation, fragmentation and reassembly.
o Increased chances of packet fragmentation
The augmentation in packet size due to packet encapsulation may
increase the chances of the packet being fragmented along the MRHA
tunnel. This can occur if there is no prior path MTU discovery
conducted, or if the MTU discovery mechanism did not take into
account the encapsulation of packets. Packets fragmentation will
result in a further increase in packet delays, and further
reduction of bandwidth efficiency.
o Increased susceptibility to link failure
Under the assumption that each link has the same probability of
link failure, a longer routing path would be more susceptibility
to link failure. Thus, packets routed through the MRHA tunnel may
be subjected to a higher probability of being lost or delayed due
to link failure, compared to packets that traverse directly
between the Mobile Network Node and its Correspondent Node.
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2.2 Bottleneck in Home Network
Apart from the increase in packet delay and infrastructure load,
forwarding packets through the Home Agent may also lead to either the
Home Agent or the Home Link becoming a bottleneck for the aggregated
traffic from/to all the Mobile Network Nodes. A congestion at home
would lead to additional packet delay, or even packet loss. In
addition, Home Agent operations such as security check, packet
interception and tunneling might not be as optimized in the Home
Agent software as plain packet forwarding. This could further limit
the Home Agent capacity for data traffic. Furthermore, with all
traffic having to pass through the Home Link, the Home Link becomes a
single point of failure for the mobile network.
Data packets that are delayed or discarded due to congestion at the
home network would cause additional performance degradation to
applications. Signaling packets, such as Binding Update messages,
that are delayed or discarded due to congestion at the home network,
may affect the establishment or update of bi-directional tunnels,
causing disruption of all traffic flow through these tunnels.
A NEMO Route Optimization mechanism that allows the Mobile Network
Nodes to communicate with their Correspondent Nodes via a path that
is different from the MRHA tunneling and thereby avoiding the Home
Agent, may alleviate or even prevent the congestion at the Home Agent
or Home Link.
2.3 Amplified Sub-Optimality in Nested Mobile Networks
By allowing other mobile nodes to join a mobile network, and in
particular mobile routers, it is possible to form arbitrary levels of
nesting of mobile networks. With such nesting, the use of NEMO Basic
Support further amplifies the sub-optimality of routing. We call
this the amplification effect of nesting, where the undesirable
effects of sub-optimal routing with NEMO Basic Support are amplified
with each level of nesting of mobile networks. This is best
illustrated by an example shown in Figure 1.
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+--------+ +--------+ +--------+ +--------+
| MR2_HA | | MR3_HA | | MR4_HA | | MR5_HA |
+------+-+ +---+----+ +---+----+ +-+------+
\ | | /
+--------+ +------------------------------+
| MR1_HA |----| Internet |-----CN1
+--------+ +------------------------------+
|
+---+---+
root-MR | MR1 |
+-------+
| |
+-------+ +-------+
sub-MR | MR2 | | MR4 |
+---+---+ +---+---+
| |
+---+---+ +---+---+
sub-MR | MR3 | | MR5 |
+---+---+ +---+---+
| |
----+---- ----+----
MNN CN2
Figure 1: An example of nested Mobile Network
Using NEMO Basic Support, the flow of packets between a Mobile
Network Node, MNN, and a Correspondent Node, CN1, would need to go
through three separate tunnels, illustrated in Figure 2 below.
----------.
---------/ /----------.
-------/ | | /-------
MNN -----( - - | - - - | - - - | - - - | - - (------ CN1
MR3-------\ | | \-------MR3_HA
MR2--------\ \----------MR2_HA
MR1---------MR1_HA
Figure 2: Nesting of Bi-Directional Tunnels
This leads to the following problems:
o Sub-optimal routing
Both inbound and outbound packets will flow via the Home Agents of
all the Mobile Routers on their paths within the mobile network,
with increased latency, less resilience and more bandwidth usage.
Appendix B illustrates in detail the packets routes under
different nesting configurations of the Mobile Network Nodes.
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o Increased Packet Size
An extra IPv6 header is added per level of nesting to all the
packets. The header compression suggested in [7] cannot be
applied because both the source and destination (the intermediate
Mobile Router and its Home Agent), are different hop to hop.
Nesting also amplifies the probability of congestion at the home
networks of the upstream Mobile Routers. In addition, the Home Link
of each upstream Mobile Router will also be a single point of failure
for the nested Mobile Router.
2.4 Sub-Optimality with Combined Mobile IPv6 Route Optimization
When a Mobile IPv6 host joins a mobile network, it becomes a Visiting
Mobile Node of the mobile network. Packets sent to and from the
Visiting Mobile Node will have to be routed not only via the Home
Agent of the Visiting Mobile Node, but also via the Home Agent of the
Mobile Router in the mobile network. This suffers the same
amplification effect of nested mobile network mentioned in
Section 2.3.
In addition, although Mobile IPv6 [2] allows a mobile host to perform
Route Optimization with its Correspondent Node in order to avoid
tunneling with its Home Agent, the "optimized" route is no longer
optimized when the mobile host is attached to a mobile network. This
is because the route between the mobile host and its Correspondent
Node is subjected to the sub-optimality introduced by the MRHA
tunnel. Interested readers may refer to Appendix B for examples of
how the routes will appear with nesting of Mobile IPv6 hosts in
mobile networks.
The readers should also note that the same sub-optimality would apply
when the mobile host is outside the mobile network and its
Correspondent Node is in the mobile network.
2.5 Security Policy Prohibiting Traffic From Visiting Nodes
The ability of Mobile Routers to attach to other Mobile Routers
allows the possibility for them to form a mesh that extends the
infrastructure dynamically, relaying each others packets to the
Internet. By providing reachability to one another, they cooperate
to improve the network availability for all parties. When Mobile
Routers have no prior knowledge of their peers (no Security
association, AAA, PKI etc...) it can still be mutually beneficial to
apply a form of reciprocal altruism based on anonymity and
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innocuousness. In particular, it is possible to adopt a tit for tat
(T4T) strategy and forward traffic unless the other party proves to
be uncooperative when it is solicited.
On the other hand, NEMO Basic Support requires all the traffic from a
visitor to be tunneled to the Mobile Router's Home Agent. This might
represent a breach in the security of the home network (some specific
attacks against the Mobile Router binding by rogue visitors have been
documented in [8][9]). As a consequence, it can be expected that in
many deployments, policies will be put in place to prevent untrusted
visitors from attaching to the Mobile Router. This will block T4T
nested NEMO for developing widely.
A Route Optimization mechanism that would prevent the multiple re-
encapsulation of the packets by nested Mobile Routers might as a side
effect alleviate this limitation and leave the way to a more open and
efficient model for the fringe of the Internet.
2.6 Instability of Communications within a Nested Mobile Network
Within a nested mobile network, two Mobile Network Nodes may
communicate with each other. Let us consider the previous example
illustrated in Figure 1 where MNN and CN2 are sharing a communication
session. With NEMO Basic Support, a packet sent from MNN to CN2 will
need to be forwarded to the Home Agent of each Mobile Router before
reaching CN2. Whereas, a packet following the direct path between
them need not even leave the mobile network. Readers are referred to
Appendix B.3 for detailed illustration of the resulting routing
paths.
Apart from the consequences of increased packet delay and packet size
which are discussed in previous sub-sections, there are two
additional effects that are undesirable:
o when the nested mobile network is disconnected from the Internet
(e.g. MR1 loses its egress connectivity), MNN and CN2 can no
longer communicate with each other, even though the direct path
from MNN to CN2 is unaffected;
o the egress link(s) of the root Mobile Router (i.e. MR1) becomes a
bottleneck for all the traffic that is coming in and out of the
nested mobile network.
A Route Optimization mechanism could allow traffic between two Mobile
Network Nodes nested within the same mobile network to follow a
direct path between them, without being routed out of the mobile
network. This may also off-load processing burden of the upstream
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Mobile Routers when the direct path between the two Mobile Network
Nodes does not traverse these Mobile Routers.
2.7 Deadlock with a Home Agent Nested in a Mobile Network
Several configurations for the Home Network are described in [6]. In
particular, there is a mobile home scenario where a (parent) Mobile
Router is also a Home Agent for its mobile network. In other words,
the mobile network is itself an aggregation, that is further
subnetted in Mobile Network Prefixes, that are assigned to (children)
Mobile Routers.
A deadlock has been documented in the case where the parent Mobile
Router visits one of its children. The child Mobile Router can not
find its Home Agent in the Internet and thus cannot establish its
MRHA tunnel and forward the visitors traffic. The traffic from the
parent is thus blocked from reaching the Internet and it will never
bind to its own (grand parent) Home Agent.
Then again, a Route Optimization mechanism that bypasses the nested
tunnel might enable the parent traffic to reach the Internet and let
it bind. At that point, the child Mobile Router would be able to
reach its parent and bind in turn. Additional nested Route
Optimization solutions might also enable the child to locate its Home
Agent in the nested structure and bind regardless of whether the
reach to the Internet is available at all.
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3. Conclusion
With current NEMO Basic Support, all communications to and from
Mobile Network Nodes must go through the MRHA tunnel when the mobile
network is away. This results in various inefficiencies associated
with packet delivery. This document investigates such
inefficiencies, and provides for the motivation behind Route
Optimization for NEMO.
We have described the effects of sub-optimal routing with NEMO Basic
Support, how it may cause a bottleneck to be formed in the home
network, and how they get amplified with nesting of mobile networks.
These effects will also be seen even when Mobile IPv6 Route
Optimization is used over NEMO Basic Support. In addition, other
issues concerning the nesting of mobile networks that might provide
additional motivation for a NEMO Route Optimization mechanism were
also explored, such as the prohibition of forwarding traffic from a
Visiting Mobile Node through a MRHA tunnel due to security concerns,
the impact of MRHA tunnel on communications between two Mobile
Network Nodes on different links of the same mobile network, and the
possibility of deadlock when Home Agents are nested within a mobile
network.
4. IANA Considerations
This is an informational document and does not require any IANA
action.
5. Security Considerations
This is an informational document that describes some limitations
with NEMO Basic Support and does not introduce any additional
security concerns. Please see RFC3963 [1] for security
considerations pertaining to the NEMO Basic Support protocol.
6. Acknowledgments
The authors wish to thank the co-authors of previous drafts from
which this draft is derived: Marco Molteni, Paik Eun-Kyoung, Hiroyuki
Ohnishi, Thierry Ernst, Felix Wu, and Souhwan Jung. In addition,
sincere appreciation is also extended to Greg Daley, Erik Nordmark,
T.J. Kniveton, Alexandru Petrescu, Hesham Soliman, Ryuji Wakikawa and
Patrick Wetterwald for their various contributions.
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7. References
7.1 Normative Reference
[1] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
"Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005.
[2] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[3] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004.
[4] Ernst, T. and H. Lach, "Network Mobility Support Terminology",
draft-ietf-nemo-terminology-03 (work in progress),
February 2005.
[5] Ernst, T., "Network Mobility Support Goals and Requirements",
draft-ietf-nemo-requirements-04 (work in progress),
February 2005.
[6] Thubert, P., "NEMO Home Network models",
draft-ietf-nemo-home-network-models-03 (work in progress),
March 2005.
7.2 Informative Reference
[7] Deering, S. and B. Zill, "Redundant Address Deletion when
Encapsulating IPv6 in IPv6",
draft-deering-ipv6-encap-addr-deletion-00 (work in progress),
November 2001.
[8] Petrescu, A., "Threats for Basic Network Mobility Support (NEMO
threats)", draft-petrescu-nemo-threats-01 (work in progress),
January 2004.
[9] Jung, S., "Threat Analysis on NEMO Basic Operations",
draft-jung-nemo-threat-analysis-02 (work in progress),
July 2004.
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Authors' Addresses
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
Pascal Thubert
Cisco Systems Technology Center
Village d'Entreprises Green Side
400, Avenue Roumanille
Biot - Sophia Antipolis 06410
FRANCE
Email: pthubert@cisco.com
Masafumi Watari
KDDI R&D Laboratories Inc.
2-1-15 Ohara
Kamifukuoka, Saitama 356-8502
JAPAN
Email: watari@kddilabs.jp
Fan Zhao
University of California Davis
One Shields Avenue
Davis, CA 95616
US
Phone: +1 530 752 3128
Email: fanzhao@ucdavis.edu
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Appendix A. Change Log
o draft-ietf-nemo-ro-problem-statement-00:
* Initial version adapted from Section 1 & 2 of
'draft-thubert-nemo-ro-taxonomy-04.txt'
* Added Section 2.2: Bottleneck in the Home Network
* Added Section 2.5: Security Policy Prohibiting Traffic From
Visiting Nodes
* Added Section 2.7: Deadlock with a Home Agent Nested in a
Mobile Network
* Appendix B extracted from 'draft-watari-nemo-nested-cn-01.txt'
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Appendix B. Various configurations involving Nested Mobile Networks
In the following sections, we try to describe different communication
models which involves a nested mobile network, and to clarify the
issues for each cases. We illustrate the path followed by packets if
we assume nodes only use Mobile IPv6 and NEMO Basic Support
mechanisms. Different cases are considered where a Correspondent
Node is located in the fixed infrastructure, in a distinct nested
mobile network as the Mobile Network Node, or in the same nested
mobile network as the Mobile Network Node. Additionally, cases where
Correspondent Nodes and Mobile Network Nodes are either standard IPv6
nodes or Mobile IPv6 nodes are considered. As defined in [4],
standard IPv6 nodes are nodes with no mobility functions whatsoever,
i.e. they are not Mobile IPv6 nor NEMO enabled. This mean that not
only can they not move around keeping open connections, but also they
cannot process Binding Updates sent by peers).
B.1 CN located in the fixed infrastructure
The most typical configuration is the case where a Mobile Network
Node communicates with a Correspondent Node attached in the fixed
infrastructure. Figure 3 below shows an example of such topology.
+--------+ +--------+ +--------+
| MR1_HA | | MR2_HA | | MR3_HA |
+---+----+ +---+----+ +---+----+
| | |
+-------------------------+
| Internet |----+ CN
+-------------------------+
| |
+---+---+ +--+-----+
root-MR | MR1 | | VMN_HA |
+---+---+ +--------+
|
+---+---+
sub-MR | MR2 |
+---+---+
|
+---+---+
sub-MR | MR3 |
+---+---+
|
----+----
MNN
Figure 3: CN located at the infrastructure
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B.1.1 Case A: LFN and standard IPv6 CN
The simplest case is where both MNN and CN are fixed nodes with no
mobility functions. That is, MNN is a Local Fixed Node, and CN is a
standard IPv6 node. Packets are encapsulated between each Mobile
Router and its respective Home Agent. As shown in Figure 4, in such
case, the path between the two nodes would go through:
1 2 3 4 3 2 1
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA --- CN
LFN IPv6 Node
The digits represent the number of IPv6 headers.
Figure 4: MNN and CN are standard IPv6 nodes
B.1.2 Case B: VMN and MIPv6 CN
In this second case, both end nodes are Mobile IPv6 enabled mobile
nodes, that is, MNN is a Visiting Mobile Node. Mobile IPv6 route
optimization may thus be initiated between the two and packets
wouldn't go through the Home Agent of the Visiting Mobile Node nor
the Home Agent of the Correspondent Node (not shown in the figure).
However, packets will still be tunneled between each Mobile Router
and its respective Home Agent, in both directions. As shown in
Figure 5, the path between MNN and CN would go through:
1 2 3 4 3 2 1
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA --- CN
VMN MIPv6
Figure 5: MNN and CN are MIPv6 mobile nodes
B.1.3 Case C: VMN and standard IPv6 CN
When the communication involves a Mobile IPv6 node either as a
Visiting Mobile Node or as a Correspondent Node, Mobile IPv6 route
optimization cannot be performed because the standard IPv6
Correspondent Node cannot process Mobile IPv6 signaling. Therefore,
MNN would establish a bi-directional tunnel with its HA, which causes
the flow to go out the nested NEMO. Packets between MNN and CN would
thus go through MNN's own Home Agent (VMN_HA). The path would
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therefore be as shown on Figure 6:
2 3 4 5 4
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA
VMN |
| 3
1 2 |
CN --- VMN_HA --- MR3_HA
IPv6 Node
Figure 6: MNN is a MIPv6 mobile node and CN is a standard IPv6 node
Providing Route Optimization involving a Mobile IPv6 node may require
optimization among the Mobile Routers and the Mobile IPv6 node.
B.2 CN located in distinct nested NEMOs
The Correspondent Node may be located in another nested mobile
network, different from the one MNN is attached to, as shown on
Figure 7. We define such configuration as ``distinct nested mobile
networks.''
+--------+ +--------+ +--------+ +--------+
| MR2_HA | | MR3_HA | | MR4_HA | | MR5_HA |
+------+-+ +---+----+ +---+----+ +-+------+
\ | | /
+--------+ +-------------------------+ +--------+
| MR1_HA |----| Internet |----| VMN_HA |
+--------+ +-------------------------+ +--------+
| |
+---+---+ +---+---+
root-MR | MR1 | | MR4 |
+---+---+ +---+---+
| |
+---+---+ +---+---+
sub-MR | MR2 | | MR5 |
+---+---+ +---+---+
| |
+---+---+ ----+----
sub-MR | MR3 | CN
+---+---+
|
----+----
MNN
Figure 7: MNN and CN located in distinct nested NEMOs
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B.2.1 Case D: LFN and standard IPv6 CN
Similar with Case A, we start off with the case where both end nodes
do not have any mobility functions. Packets are encapsulated at
every mobile router on the way out the nested mobile network,
decapsulated by the Home Agents and then encapsulated again on its
way down the nested mobile network.
1 2 3 4 3 2
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA
LFN |
| 1
1 2 3 2 |
CN --- MR5 --- MR4 --- MR4_HA --- MR5_HA
IPv6 Node
Figure 8: MNN and CN are standard IPv6 nodes
B.2.2 Case E: VMN and MIPv6 CN
Similar with Case B, when both end nodes are Mobile IPv6 nodes, the
two nodes may initiate Mobile IPv6 route optimization. Again,
packets will not go through the Home Agent of the MNN nor the Home
Agent of the Mobile IPv6 Correspondent Node (not shown in the
figure). However, packets will still be tunneled for each Mobile
Router to its Home Agent and vise versa. Therefore, the path between
MNN and CN would go through:
1 2 3 4 3 2
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA
VMN |
| 1
1 2 3 2 |
CN --- MR5 --- MR4 --- MR4_HA --- MR5_HA
MIPv6 Node
Figure 9: MNN and CN are MIPv6 mobile nodes
B.2.3 Case F: VMN and standard IPv6 CN
Similar to Case C, when the communication involves a Mobile IPv6 node
either as a Visiting Mobile Node or as a Correspondent Node, MIPv6
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route optimization can not be performed because the standard IPv6
Correspondent Node cannot process Mobile IPv6 signaling. MNN would
therefore establish a bi-directional tunnel with its Home Agent.
Packets between MNN and CN would thus go through MNN's own Home Agent
as shown on figure Figure 10:
2 3 4 5 4 3
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA
VMN |
| 2
1 2 3 2 1 |
CN --- MR5 --- MR4 --- MR4_HA --- MR5_HA --- VMN_HA
IPv6 Node
Figure 10: MNN is a MIPv6 mobile node and CN is a standard IPv6 node
B.3 CN and MNN located in the same nested NEMO
Figure 11 below shows the case where the two communicating nodes are
connected behind different Mobile Routers that are connected in the
same nested mobile network, and thus behind the same root Mobile
Router. Route optimization can avoid packets being tunneled outside
the nested mobile network.
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+--------+ +--------+ +--------+ +--------+
| MR2_HA | | MR3_HA | | MR4_HA | | MR5_HA |
+------+-+ +---+----+ +---+----+ +-+------+
\ | | /
+--------+ +-------------------------+ +--------+
| MR1_HA |----| Internet |----| VMN_HA |
+--------+ +-------------------------+ +--------+
|
+---+---+
root-MR | MR1 |
+-------+
| |
+-------+ +-------+
sub-MR | MR2 | | MR4 |
+---+---+ +---+---+
| |
+---+---+ +---+---+
sub-MR | MR3 | | MR5 |
+---+---+ +---+---+
| |
----+---- ----+----
MNN CN
Figure 11: CN and MNN located in the same nested NEMO
B.3.1 Case G: LFN and standard IPv6 CN
Again, we start off with the case where both end nodes do not have
any mobility functions. Packets are encapsulated at every Mobile
Router on the way out the nested mobile network via the root Mobile
Router, decapsulated and encapsulated by the Home Agents and then
make their way back to the nested mobile network through the same
root Mobile Router. Therefore, the path between MNN and CN would go
through:
1 2 3 4 3 2
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA
LFN |
| 1
1 2 3 4 3 2 |
CN --- MR5 --- MR4 --- MR1 --- MR1_HA --- MR4_HA --- MR5_HA
IPv6 Node
Figure 12: MNN and CN are standard IPv6 nodes
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B.3.2 Case H: VMN and MIPv6 CN
Similar with Case B and E, when both end nodes are Mobile IPv6 nodes,
the two nodes may initiate Mobile IPv6 route optimization which will
avoid the packets to go through the Home Agent of MNN nor the Home
Agent of the Mobile IPv6 CN (not shown in the figure). However,
packets will still be tunneled between each Mobile Router and its
respective Home Agent in both directions. Therefore, the path would
be the same with Case G and go through:
1 2 3 4 3 2
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA
LFN |
| 1
1 2 3 4 3 2 |
CN --- MR5 --- MR4 --- MR1 --- MR1_HA --- MR4_HA --- MR5_HA
MIPv6 Node
Figure 13: MNN and CN are MIPv6 mobile nodes
B.3.3 Case I: VMN and standard IPv6 CN
As for Case C and Case F, when the communication involves a Mobile
IPv6 node either as a Visiting Mobile Node or as a Correspondent
Node, Mobile IPv6 Route Optimization can not be performed.
Therefore, MNN will establish a bi-directional tunnel with its Home
Agent. Packets between MNN and CN would thus go through MNN's own
Home Agent. The path would therefore be as shown on Figure 14:
2 3 4 5 4 3
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA
VMN |
| 2
|
VMN_HA
|
| 1
1 2 3 4 3 2 |
CN --- MR5 --- MR4 --- MR1 --- MR1_HA --- MR4_HA --- MR5_HA
IPv6 Node
Figure 14: MNN is a MIPv6 mobile node and CN is a standard IPv6 node
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B.4 CN located behind the same nested MR
Figure 15 below shows the case where the two communicating nodes are
connected behind the same nested Mobile Router. The optimization is
required when the communication involves MIPv6-enabled nodes.
+--------+ +--------+ +--------+ +--------+
| MR2_HA | | MR3_HA | | MR4_HA | | MR5_HA |
+------+-+ +---+----+ +---+----+ +-+------+
\ | | /
+--------+ +-------------------------+ +--------+
| MR1_HA |----| Internet |----| VMN_HA |
+--------+ +-------------------------+ +--------+
|
+---+---+
root-MR | MR1 |
+---+---+
|
+-------+
sub-MR | MR2 |
+---+---+
|
+---+---+
sub-MR | MR3 |
+---+---+
|
-+--+--+-
MNN CN
Figure 15: MNN and CN located behind the same nested MR
B.4.1 Case J: LFN and standard IPv6 CN
If both end nodes are Local Fixed Nodes, no special function is
necessary for optimization of their communication. The path between
the two nodes would go through:
1
MNN --- CN
LFN IPv6 Node
Figure 16: MNN and CN are standard IPv6 nodes
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B.4.2 Case K: VMN and MIPv6 CN
Similar with Case H, when both end nodes are Mobile IPv6 nodes, the
two nodes may initiate Mobile IPv6 route optimization. Although few
packets would go out the nested mobile network for the Return
Routability initialization, however, unlike Case B and Case E,
packets will not get tunneled outside the nested mobile network.
Therefore, packets between MNN and CN would eventually go through:
1
MNN --- CN
VMN MIPv6 Node
Figure 17: MNN and CN are MIPv6 mobile nodes
If the root Mobile Router is disconnected while the nodes exchange
keys for the Return Routability procedure, they may not communicate
even though they are connected on the same link.
B.4.3 Case L: VMN and standard IPv6 CN
When the communication involves a Mobile IPv6 node either as a
Visiting Mobile Network Node or as a Correspondent Node, Mobile IPv6
Route Optimization cannot be performed. Therefore, even though the
two nodes are on the same link, MNN will establish a bi-directional
tunnel with it's Home Agent, which causes the flow to go out the
nested mobile network. Path between MNN and CN would require another
Home Agent (VMN_HA) to go through for this Mobile IPv6 node:
2 3 4 5 4 3
MNN --- MR3 --- MR2 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA
VMN |
| 2
|
VMN_HA
|
| 1
1 2 3 4 3 2 |
CN --- MR5 --- MR4 --- MR1 --- MR1_HA --- MR2_HA --- MR3_HA
IPv6 Node
Figure 18: MNN is a MIPv6 mobile node and CN is a standard IPv6 node
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