One document matched: draft-na-nemo-gen-ro-model-00.txt
NEMO Working Group Jongkeun Na
Internet Draft Seongho Cho
Expires: January 2005 Chongkwon Kim
Seoul National University
Changhoi Koo
Samsung Electronics
July 2004
Generic Route Optimization Model for NEMO Extended Support
draft-na-nemo-gen-ro-model-00
Status of this Memo
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Abstract
In this memo, we introduce the generic Route Optimization (RO)
model that can be used as a framework to evaluate the existing RO
models. Then, we analyze typical RO problems by virtue of that. And,
we discuss on the feasibility of achieving a unified RO in NEMO,
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and enumerate the issues that should be cleared for the purpose of
that.
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 RFC-2119.
Table of Contents
1. Introduction.................................................3
2. Generic Route Optimization Model.............................3
3. The Analysis of RO Problems in NEMO..........................5
3.1 RO in the infrastructure................................6
3.2 Nested Tunnels Optimization (NTO).......................7
4. Toward to a unified route optimization in NEMO...............8
5. Open Issues..................................................9
6. Security Considerations......................................9
References......................................................10
Acknowledgments.................................................11
Authors' Addresses..............................................11
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1. Introduction
NEMO Basic Support Protocol [15] would suppose to support the
transparent mobility to mobile network nodes (MNNs) in mobile
networks by using MR-HA bi-directional tunnel. However, inherently
due to the use of the bi-directional tunnel, there are some types
of route optimization problem [14] that need our attention.
RO problems have a common property that there is an optimized path,
but it cannot be used due to support the transparent mobility to
the IP terminals. While preserving the goals of Mobile IP [1] and
NEMO Basic [15], it is impossible to realize RO without introducing
the tunnel-based virtual path over IP routing through some
extensions or new functionalities of routing facilities. This is
the reason why the existing proposed solutions for RO at least use
tunnel-based packet redirection or re-routing mechanism in the
extended routing facilities such as Correspondent Router (CR).
As a requirement about RO, we argue that RO in NEMO should be
provided by a unified solution which can solve most of RO problems
by applying the same principle to the routing facilities such as HA,
MR, CR. If each different RO solution is used to solve each RO
problem, it will produce the protocol redundancy and complexity in
the routing facilities.
In this memo, we introduce the generic RO model that can be used as
a framework to evaluate the existing RO models. Then, we analyze
typical RO problems by virtue of the generic RO model. And, we
discuss on the feasibility of achieving a unified RO in NEMO, and
enumerate the issues that should be cleared for the purpose of that.
2. Generic Route Optimization Model
Route Optimization in NEMO means that one routing entity uses an IP
tunnel to redirect the original packets to the other routing entity
that is most closely located from the destination. To enable such a
route optimization, two routing entities must recognize each other,
in other words, anyone among them should feel the need of RO tunnel
and initiate the signaling procedure to make an IP tunnel between
them. We can define such an IP tunnel as `RO Tunnel (ROT)` in NEMO
context because it is established for the purpose of route
optimization in NEMO. This is like the basic principle of Mobile IP.
In Mobile IP, MN detects its movement and initiates BU to HA. Such
an analogy can be extended to RO problem in NEMO. In this point of
view, we can extract some of statements characterizing how to
achieve RO tunnel. For example, which routing facilities can
initiate RO tunnel? What information does trigger such a RO tunnel?
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How can the trigger information be delivered to the initiator of RO
tunnel? And so on. The answer to those of questions depends on the
problem spaces [14] and the proposed solutions [4][5][19][20] in
each problem space.
The attributes of RO tunnel can concretely well express the RO
context including the purpose of RO, the operation of RO, and the
effectiveness of RO.
TE[1] TS[0..n] TR[0..n] TE[1]
+--+---------+--+--------+--+--------+--+
====|XX|=========|XX|========|==|========|XX|====
+--+---------+--+--------+--+--------+--+
XX: Tunnel Processing (Encap./Decap.)
TE: Tunnel Endpoint
TS: Tunnel Switcher
TR: Tunnel Relay
Fig.1 Generic RO Tunnel (ROT) Model
Fig.1 shows the generalized ROT model. ROT can be made of at least
two TEs. In here, TE is a router or host which is allowed to
initiate or terminate the RO tunnel in the view of route
optimization. According to the type of ROT, ROT can include zero or
more TS for switching an incoming tunnel to an outgoing tunnel at
that point, zero or more TR for relaying the tunneled packets to
next intermediate point. As of TR, The difference is that it
operates a routing mechanism, such as Source Routing using RH0
header [10], based on the packet header information without the
knowledge of the end-to-end tunneling, while TS processes the
tunnel switching based on a given tunnel mapping information that
consistently maintained in that point by interacting with other
tunnel endpoints.
From the general ROT model, we can drive the following attributes
which can be exploited to characterize a specific RO model.
RO Initiator (ROI)
We need to identify which TE among two TEs can be the initiator
in making a RO tunnel. This parameter depends on the applied RO
scheme. In one RO scheme, MR is only the initiator, on the other
hand, HA and CR can be the initiator in the other RO scheme.
RO Responder (ROR)
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We need to identify which routing facilities can be the
responder in making a RO tunnel. This parameter also depends on
the applied RO scheme.
RO Trigger Source (ROTS)
The RO initiator (ROI) is recognized for the need of RO from
this information. For example, an explicit RO bit in the packet
header can be used to force the receiver to start the RO.
RO Responder Information (RORI)
This information is used for the RO initiator (ROI) to identify
the RO responder (ROR). It would include the address information
of the moving entity such as MR, or the address information of
the correspondent nodes.
RO Discovery Mechanism (RODM)
This mechanism describes that how RORI can be delivered to the
RO initiator (ROI). In other words, ROI can get RORI by using
this discovery mechanism. For example, if ROI itself try to find
its ROR using IPv6 anycast address, RORI becomes an address of
ROR and we can say that RODM is IPv6 anycasting mechanism.
RO Tunnel Type (ROTT)
ROTT can be classified as the followings: Simple ROT (SiROT),
Switched ROT (SwROT), Releyed ROT (ReROT). SiROT consists of
only two TEs. SwROT consists of one or more TS between two TEs.
ReROT consists of one or more TR between two TEs. For example,
we can say that RRH [4] uses ReROT as RO Tunnel Type, HMIPv6
uses SwROT.
More attributes to be defined.
3. The Analysis of RO Problems in NEMO
In this section, we analyze typical RO problems in NEMO using the
generic ROT model.
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3.1 RO in the infrastructure
TE[1] TE[1]
+--+---------------------------------+--+
====|XX|=================================|XX|====
+--+---------------------------------+--+
Fig.2 SiROT based RO in the infrastructure
Fig.2 shows the simple RO in the infrastructure. This RO model was
used in ORC [19]. According to the generic ROT model, the following
formulation is possible.
TE: Mobile Router (MR), Optimized Route Cache (ORC) Router
ROI: MR
ROR: ORC Router
ROTS: the packet sent from any CN via MR-HA default tunnel
RORI: the global IPv6 address of ORC Router
RODM: IPv6 anycast addressing
ROTT: SiROT
Above attributes compactly describes that this RO implements ROT
between MR and ORC Router, and MR initiates the signaling procedure
for ROT to ORC Router after getting the global IPv6 address of ORC
Router through IPv6 anycast addressing. This RO model also includes
some RO approaches, such as C-Side Router or Correspondent Router
(CR), mentioned in RO-Taxonomy [14]. To include those of RO
approaches, we can loosely redefine above attributes as follows:
TE: Mobile Router (MR), Optimized Route Cache (ORC) Router, C-Side
Router, Correspondent Router (CR)
ROI: MR
ROR: ORC Router, C-Side Router, CR
ROTS: the packet sent from any CN via MR-HA default tunnel
RORI: the global IPv6 address of ROR
RODM: IPv6 anycast addressing
ROTT: SiROT
TE[1] TS[1] TE[1]
+--+---------------------+--+--------+--+
====|XX|=====================|XX|========|XX|====
+--+---------------------+--+--------+--+
Fig.3 SwROT based RO in the infrastructure
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Fig.3 shows extended RO in the infrastructure. This RO model
includes one TS entity and two TEs. Distributed Anchor Routers
described in RO-Taxonomy [14] can be expressed as this model like
below.
TE: Mobile Router (MR), C-Side Anchor Router
TS: M-Side Anchor Router (a.k.a Mobility Anchor Point in HMIPv6)
ROI: Not mentioned
ROR: Not mentioned
ROTS: Not mentioned
RORI: Not mentioned
RODM: Not mentioned
ROTT: SwROT
In this case, most of attributes in the ROT model are not
determined, so it is required to deeply understand this RO problem
and derive its viable solution.
3.2 Nested Tunnels Optimization (NTO)
NTO can be modeled like Fig.4 by using the ROT model. For example,
the attributes of RRH [4] model are as follows:
TE[1] TR[1..n] TE[1]
+--+---------------------+--+--------+--+
====|XX|=====================|==|========|XX|====
+--+---------------------+--+--------+--+
Fig.4 ReROT based NTO
TE: Mobile Router (MR), Home Agent (HA)
TR: MR (via Source Routing)
ROI: MR
ROR: HA
ROTS: TIO option in RA [14]
RORI: Nested Path Information like MR3->MR2->MR1->HA3
RODM: Using Reverse Routing Header (RRH)
ROTT: ReROT
Similarly, ARO [5] can be expressed as follows:
TE: Mobile Router (MR), Home Agent (HA)
TR: MR (via Source Routing)
ROI: MR
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ROR: HA
ROTS: BU with ARO option, Recursive Binding Update by ancestor MRs
RORI: Nested Path Information like MR3->MR2->MR1->HA3
RODM: Using Access Router Option (ARO) & Recursive BU
ROTT: ReROT
4. Toward to a unified route optimization in NEMO
There are some efforts for Route Optimization (RO). For RO in the
routing infrastructure, some approaches such as VIP [17], ORC [19]
require a special router or the extension of the existing router
which can handle the packet redirection to gain RO effect. The RO
schemes belong to this category can be applied to both Mobile IP
and NEMO in IP routing infrastructure. On the other hand, There are
other kinds of the NEMO-specific RO problem. [14] well defines RO
problem spaces of NEMO and briefly analyzes the proposed interim
solutions. Typically, one of NEMO-specific RO problem is a nested
tunneling problem that can be formed due to the network mobility.
Most of proposed solutions are for solving that problem. As of now,
it's not easy to say how RO problems in NEMO can be best solved in
the reasonable manner. However, the sure thing is that current
proposed solutions can be applied only to one problem space of RO.
That is an uncomfortable and unnatural facet in supporting coherent
network mobility. We need a simple and effective, unified route
optimization scheme for network mobility.
With the help of the ROT model, we can evaluate whether or not
there is the feasibility of achieving a unified route optimization
in NEMO, and enumerate the issues that should be cleared for the
purpose of that. As a unified RO model, let us illustrate one
example as Fig.5. In here, TR can be zero. That is only difference
in comparing with Fig.4. However, this trivial difference in the
model implies that this model can support SiROT based RO in the
infrastructure as well as ReROT based NTO. PCH [20] approach
belongs to this model.
TE[1] TR[0..n] TE[1]
+--+---------------------+--+--------+--+
====|XX|=====================|==|========|XX|====
+--+---------------------+--+--------+--+
Fig.5 A unified RO supporting ReROT as well as SiROT
As an instance of a unified RO, The attributes of PCH [20] model
can be summarized as follows:
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TE: Mobile Router (MR), Home Agent (HA), Correspondent Router (CR)
TR: MR (via Source Routing)
ROI: CR, HA
ROR: MR
ROTS: Receiving the packet with Path Control Header (PCH)
RORI: Nested Path Information like MR1-MR2-MR3, contained in PCH
RODM: PCH Piggybacking by HA
ROTT: SiROT+ReROT
5. Open Issues
? Functional entities involving in RO
? Source routing in the inside of nested mobile network
? Considerations on RO in multi-homed mobile networks
? Performance / Evaluation Metric for RO
TBD
6. Security Considerations
TBD
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References
[1] Perkins, C., Johnson, D. and J. Arkko, "Mobility Support in
IPv6", draft-ietf-mobileip-ipv6-18 (work in progress), July
2002.
[2] Ernst, T. and H. Lach, "Network Mobility Support Terminology",
draft-ietf-nemo-terminology-00 (work in progress), May 2003.
[3] Ernst, T., Castelluccia, C., Bellier, L., Lach, H. and A.
Olivereau, "Mobile Networks Support in Mobile IPv6 (Prefix
Scope Binding Updates)", draft-ernst-mobileip-v6-network-03
(work in progress), March 2002.
[4] Thubert, P., and Molteni, M., "IPv6 Reverse Routing Header
and Its Application to Mobile Networks", Internet Draft:
draft-thubert-nemo-reverse-routing-header-01
(work in progress), Oct 2002.
[5] Chan-Wah Ng, and Takeshi Tanaka, "Securing Nested Tunnels
Optimization with Access Router Option", Internet Draft:draft
-ng-nemo-access-router-option-00(work in progress), Oct 2002.
[7] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[8] Kent, S. and R. Atkinson, "IP Authentication Header",
RFC 2402, November 1998.
[9] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload
(ESP)", RFC 2406, November 1998.
[10] Deering, S. and R. Hinden, "Internet Protocol,
Version 6 (IPv6) Specification", RFC 2460, December 1998.
[11] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998.
[12] Conta, A. and S. Deering, "Internet Control Message Protocol
(ICMPv6) for the Internet Protocol Version 6 (IPv6)
Specification", RFC 2463, December 1998.
[13] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by
an On-line Database", RFC 3232, January 2002.
[14] Thubert, P., and Molteni, M., "Taxonomy of Route Optimization
Models in the NEMO Context", Internet Draft: draft-thubert-
nemo-ro-taxonomy-00(work in progress), Oct 2002.
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[15] vijay, D., Ryuji, W., Alexandru, P., Pascal, T., "NEMO Basic
Support Protocol", draft-ietf-nemo-basic-support-00(work in
process), June 2003.
[16] A. Conta, S. Deering, "Generic Packet Tunneling in IPv6
Specificiation", RFC2473, December 1998.
[17] Fumio Teraoka, Keisuke Uehara, Hideki Sunahara, and Jun Murai,
``VIP : A Protocol Providing Host Mobility,`` Aug. 1994
[18] Weidong Chen, Eric Lin, ``Route Optimization and Location
Updates for Mobile Hosts,`` International Conference on
Distributed Computing Systems,1996
[19] Ryuji Wakikawa, Susumu Koshiba, Keisuke Uehara, Jun Murai,
``ORC: Optimized Route Cache Management Protocol for Network
Mobility,`` Proc. of ICT2003, Nov 2003.
[20] Jongkeun Na, et.al. ``Route Optimization Scheme based on Path
Control Header,`` draft-na-nemo-path-control-header-00(work
in process), April 2004.
Acknowledgments
Authors' Addresses
Jongkeun Na
Information Networking & Computing Lab.
School of Computer Science and Engineering,
Seoul National University, Seoul Korea
EMail: jkna@popeye.snu.ac.kr
Sungho Cho
Information Networking & Computing Lab.
School of Computer Science and Engineering,
Seoul National University, Seoul Korea
EMail: shcho@popeye.snu.ac.kr
Chongkwon Kim
Information Networking & Computing Lab.
School of Computer Science and Engineering,
Seoul National University, Seoul Korea
EMail: ckim@popeye.snu.ac.kr
Changhoi Koo
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Global Standards & Research Team
Telecommunication R&D Center,
Samsung Electronics, KOREA
Email : chkoo@samsung.com
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