Individual Submission
Internet Draft Jae-Hoon Jeong
Kyeong-Jin Lee
Jung-Soo Park
Hyoung-Jun Kim
<draft-jeong-nemo-ro-ndproxy-00.txt> ETRI
Expires: December 2003 7 June 2003
ND-Proxy based Route Optimization for Mobile Nodes in Mobile Network
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 except that the right to
produce derivative works is not granted [1].
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Abstract
This document specifies a mechanism for enabling mobile nodes in IPv6
mobile network to perform route optimization. The route optimization
is possible because mobile router provides the prefix of its care-of-
address for its mobile nodes by playing the role of ND-proxy.
Through binding updates associated with the network prefix of an
access network, the mobile nodes can perform route optimization.
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 [2].
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Table of Contents
1. Terminology...................................................2
2. Introduction..................................................2
3. Overview......................................................2
4. Mobile Router extension : Process of Prefix Information option
for Route Optimization (RO)...................................3
5. Neighbor Discovery extension..................................4
5.1 RO Prefix Information option format.......................4
5.2 Neighbor Solicitation (NS) message format.................5
6. Procedure of Route Optimization...............................6
6.1 Generation of a new CoA...................................6
6.2 DAD for the new CoA.......................................6
6.3 Return Routability and Binding Update.....................6
6.4 Delivery of Data Packets..................................6
7. Security Considerations.......................................7
8. References....................................................7
9. Acknowledgements..............................................7
10. Authors' Addresses...........................................8
1. Terminology
This document uses the terminology described in [3]-[6]. Especially
three important terms are as follows [5]:
Multilink Subnet (MS)
A collection of independent links, connected by routers, but
sharing a common subnet prefix.
ND-Proxy
A router proxying and relaying for all nodes on its router-mode
interfaces except proxy-mode interfaces among its network
interfaces.
Multilink-Subnet Router (MSR)
A router which has interfaces attached to different links in a
MS, and which plays the role of ND-Proxy.
2. Introduction
The basic support of mobile network (NEMO) enables mobile network
nodes and correspondent nodes to communicate through bi-directional
tunnels. Deeper multi-level network this NEMO gets, longer the delay
becomes by dog-legged routing. This document specifies how to
optimize the routes between mobile nodes and correspondent nodes.
3. Overview
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This route optimization is possible by a mobile router performing ND-
Proxy, which makes a care-of-address (CoA) with the prefix advertised
by access router and delivers the prefix of access network into the
NEMO. Each mobile node can make its new CoA with router
advertisement message including access network prefix and perform the
return routability and binding update procedure. As ND-Proxy, the
mobile router performs neighbor discovery instead of the mobile nodes
within its NEMO.
Like this, access network and NEMO are configured into a multilink
subnet through mobile router that performs ND-Proxy. Figure 1 shows
an example of a multilink subnet comprised of four links from Link1
to Link4. Three mobile routers from MR1 to MR3 relay the prefix
information of access network (AR1_P) that was sent by an access
router, AR1. The mobile nodes, MN1 and MN2, within the NEMO
controlled by MR1 can perform route optimization with the prefix
information relayed by its mobile router, MR1. Also, MN3 can
optimize the route through MR2. MN4 and MN5 can perform route
optimization through MR2 and MR3, too.
+---+
|AR1|
RA(AR1_P)| +-+-+
V |
----------+---------------+---------------+----------- Link1
|Proxy-mode |Proxy-mode
+-+-+ +-+-+
|MR1| |MR2|
RA(AR1_P)| +-+-+ RA(AR1_P)| +-+-+
V |Router-mode V |Router-mode
---+-----+-----+--- Link2 ---+------+-----+--- Link3
| | | Proxy-mode|
+-+-+ +-+-+ +-+-+ +-+-+
|MN1| |MN2| |MN3| |MR3|
+---+ +---+ +---+ +---+ | RA(AR1_P)
Router-mode| V
---+-----+-----+--- Link4
| |
+-+-+ +-+-+
|MN4| |MN5|
+-+-+ +-+-+
Figure 1. Multilink Subnet for Route Optimization
4. Mobile Router extension : Process of Prefix Information option for
Route Optimization (RO)
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Mobile router MUST perform the role of ND-Proxy and relay the prefix
information that is received from an access router. Before mobile
router advertises the prefix information through Router Advertisement
(RA) message, it MUST set route-optimization flag indicating that
this prefix can be used for route optimization of mobile nodes, which
are either local mobile nodes or visiting mobile nodes within the
mobile network.
If a mobile node within a mobile network receives the new prefix
information option through RA message and can recognize this option,
it MAY prefer this new prefix information option to the normal prefix
information option that contains the mobile network prefix assigned
by the mobile router's home network. By performing binding update
with the prefix of the access network, the mobile node can optimize
the routes between its correspondent nodes and itself.
5. Neighbor Discovery extension
5.1 RO Prefix Information option format
The mechanism of this document needs the addition of a new flag
within prefix information option for route optimization [3]. When
this flag is set, it indicates that the prefix included in the option
can be used by mobile nodes within a NEMO for the route optimization.
Figure 2 shows the format of the modified prefix information option,
RO Prefix Information option.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Prefix Length |L|A|O|Reserved1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preferred Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. Prefix Information Option Format for Route Optimization
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Field:
O 1-bit route-optimization flag. When set indicates
that this prefix can be used for the route
optimization of mobile nodes within NEMO.
The RO Prefix Information option provides a mobile node with the
network prefix of access network and allows it to autoconfigure its
new CoA through stateless address autoconfiguration and to perform
binding update. The Prefix Information option appears in RA message
and MUST be silently ignored for other messages. L (On-link) flag
MAY be either 0 or 1. Namely, this route optimization can be either
on-link or off-link model [5]. A (Autonomous address-configuration)
flag MUST be 1, indicating IPv6 stateless address autoconfiguration.
5.2 Neighbor Solicitation (NS) message format
NS message MUST be extended for Duplicate Address Detection (DAD) for
the address based on RO prefix of access network. Therefore, there
is a need to discriminate between the normal NS message and extended
NS message for route optimization [3]. Figure 3 shows the format of
the modified NS message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Target IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
Figure 3. Extended Neighbor Solicitation Message Format
Fields:
M 1-bit multi-hop flag. When set indicates
that this NS message SHOULD be relayed to the other
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links of multilink subnet.
Target IPv6 Address
The IPv6 address of the target of the solicitation
that will be used as CoA. It MUST NOT be a
multicast address.
6. Procedure of Route Optimization
6.1 Generation of a new CoA
Whenever a mobile node first receives RA message containing RO prefix
information option that includes a new network prefix of access
network, it makes a new CoA.
6.2 DAD for the new CoA
The mobile node performs DAD for the new CoA through the extended NS
message. The NS message of DAD for the new address is relayed by a
mobile router, acting as ND-Proxy, on the link where the mobile node
is placed [5]. The mobile router memorizes the DAD for returning NA
message to the sender of the extended NS message.
If there is no NA returned and the DAD is successful, the mobile node
configures the address as its new CoA in its network interface.
Notice that the DAD for the link-local addresses and global addresses
based on mobile network prefix assigned by home network is performed
through normal NS message only within a link and the DAD for the
global addresses based on access network prefix is performed through
extended NS message within a multilink subnet, which is relayed by
ND-Proxies.
6.3 Return Routability and Binding Update
After configuring the new CoA, the mobile node performs the return
routability and binding update procedure of Mobile IPv6 [7].
6.4 Delivery of Data Packets
After binding update, the data packets of correspondent nodes toward
the mobile node are delivered to the access network to which the NEMO
containing the mobile node is attached via optimal paths.
When the access router of the access network receives the data
packets, it multicasts normal Neighbor Solicitation (NS) message to
the solicited-node multicast address of the destination IPv6 address
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in order to find out the link-layer address of the destination node.
The mobile router, knowing the link-layer address of the target,
responds to the NS message by returning its own link-layer address in
a unicast Neighbor Advertisement (NA) message as ND-Proxy, which
knows the IPv6 addresses and link-layer addresses of mobile nodes
within its mobile network during the DAD of each CoA of each mobile
node.
When the access router knows the link-layer address to the
destination, it forwards the IPv6 data packets to the mobile router
corresponding to the link-layer address. The mobile router relays
the packets to the destination mobile node. In case that the NEMO
where the destination node is placed is multi-level, the packets may
be relayed to the destination node by more than one mobile router.
7. Security Considerations
The route optimization in this document does not add any other
security problems to the NEMO or Mobile IPv6.
8. References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] T. Narten, E. Nordmark and W. Simpson, "Neighbour Discovery for
IP version 6", RFC 2461.
[4] S. Thomson and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462.
[5] Dave Thaler and Chistian Huitema, "Multi-link Subnet Support in
IPv6", draft-ietf-ipv6-multilink-subnets-00.txt, June 2002.
[6] Thierry Ernst, "Network Mobility Support Terminology", draft-
ietf-nemo-terminology-00.txt, May 2003.
[7] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in IPv6",
draft-ietf-mobileip-ipv6-22.txt, May 2003.
9. Acknowledgements
The authors would like to acknowledge the previous contribution of
Dave Thaler and Christian Huitema.
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10. Authors' Addresses
Jae-Hoon Jeong
ETRI / PEC
161 Gajong-Dong, Yusong-Gu
Daejon 305-350
Korea
Phone: +82 42 860 1664
EMail: paul@etri.re.kr
Kyeong-Jin Lee
ETRI / PEC
161 Gajong-Dong, Yusong-Gu
Daejon 305-350
Korea
Phone: +82 42 860 6484
EMail: leekj@etri.re.kr
Jung-Soo Park
ETRI / PEC
161 Gajong-Dong, Yusong-Gu
Daejon 305-350
Korea
Phone: +82 42 860 6514
EMail: pjs@etri.re.kr
Hyoung-Jun Kim
ETRI / PEC
161 Gajong-Dong, Yusong-Gu
Daejon 305-350
Korea
Phone: +82 42 860 6576
EMail: khj@etri.re.kr
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