< draft-jeong-nemo-ro-ndproxy-01.txt   draft-jeong-nemo-ro-ndproxy-02.txt >
Individual Submission Internet Draft
Internet Draft Jaehoon Paul Jeong Jaehoon Paul Jeong
Kyeong-Jin Lee Kyeongjin Lee
Jung-Soo Park Jungsoo Park
Hyoung-Jun Kim Hyoungjun Kim
<draft-jeong-nemo-ro-ndproxy-01.txt> ETRI draft-jeong-nemo-ro-ndproxy-02.txt ETRI
Expires: April 2004 2 October 2003 Expires: August 2004 14 February 2004
ND-Proxy based Route and DNS Optimizations for ND-Proxy based Route and DNS Optimizations for
Mobile Nodes in Mobile Network Mobile Nodes in Mobile Network
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 except that the right to all provisions of Section 10 of RFC2026 except that the right to
produce derivative works is not granted [1]. produce derivative works is not granted [1].
skipping to change at page 1, line 39 skipping to change at page 1, line 39
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
This document specifies a mechanism for enabling mobile nodes in IPv6 This document specifies a mechanism for enabling mobile nodes in IPv6
mobile network to perform route optimization. The route optimization mobile network to perform route and DNS optimizations. The route
is possible because mobile router relays the prefix of its Care-of optimization is possible because mobile router relays the prefix of
address to its mobile nodes by playing the role of ND-proxy. its care-of address to its mobile nodes by playing the role of ND-
Through binding updates associated with the network prefix of an proxy. Through binding updates associated with the network prefix of
access network, the mobile nodes can perform route optimization. In an access network, the mobile nodes can perform route optimization.
addition, this document explains how mobile nodes can optimize its In addition, this document explains how mobile nodes can optimize its
DNS name resolution through RA-based DNS discovery. By announcing DNS name resolution through RA-based DNS discovery. By announcing
the address of local recursive DNS server, mobile router allows the address of local recursive DNS server, mobile router allows
mobile nodes to optimize their DNS name resolution. mobile nodes using the DNS server to optimize their DNS name
resolutions without additional overhead of finding DNS server.
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [2]. document are to be interpreted as described in RFC 2119 [2].
Table of Contents Table of Contents
1. Terminology...................................................2 1. Terminology...................................................2
2. Introduction..................................................3 2. Introduction..................................................3
3. Overview......................................................3 3. Overview......................................................4
4. Neighbor Discovery extension..................................4 4. Neighbor Discovery extension..................................5
4.1 RO Prefix Information option format.......................4 4.1 RO Prefix Information option format.......................5
4.2 Neighbor Solicitation (NS) message format.................5 4.2 Neighbor Solicitation (NS) message format.................6
4.3 DNS Server option format..................................6 4.3 DNS Server option format..................................7
5. Mobile Router.................................................8 5. Mobile Router.................................................8
5.1 Process of RO Prefix Information option...................8 5.1 Process of RO Prefix Information option...................8
5.2 Process of DNS Server option..............................8 5.2 Process of DNS Server option..............................9
5.3 Delivery of Data Packets..................................8 5.3 Delivery of Data Packets..................................9
6. Mobile Node...................................................9 5.4 Movement of Mobile Router.................................9
6.1 Procedure of Route Optimization...........................9 6. Mobile Node..................................................10
6.1.1 Generation of a new CoA.............................9 6.1 Procedure of Route Optimization..........................10
6.1.2 DAD for the new CoA.................................9 6.1.1 Generation of a new CoA............................10
6.1.3 Return Routability and Binding Update..............10 6.1.2 DAD for the new CoA................................10
6.2 Procedure of DNS Optimization............................10 6.1.3 Return Routability and Binding Update..............11
6.2.1 RDNSS Configuration................................10 6.2 Procedure of DNS Optimization............................11
6.2.2 RDNSS Selection....................................10
7. Security Considerations......................................11 7. Security Considerations......................................11
8. Copyright....................................................11 8. Copyright....................................................11
9. Normative References.........................................12 9. Normative References.........................................12
10. Informative References......................................12 10. Informative References......................................12
11. Acknowledgements............................................13 11. Acknowledgements............................................13
12. Authors' Addresses..........................................13 12. Authors' Addresses..........................................13
1. Terminology 1. Terminology
This document uses the terminology described in [3]-[7]. Especially This document uses the terminology described in [3]-[8]. Especially,
four important terms are as follows [5][7]: four important terms are defined as follows [6][8]:
Multilink Subnet (MS) Multilink Subnet (MS)
A collection of independent links, connected by routers, but A collection of independent links, connected by routers, but
sharing a common subnet prefix. sharing a common subnet prefix.
ND-Proxy ND-Proxy
A router proxying and relaying for all nodes on its router-mode A router proxying and relaying for all nodes on its router-mode
interfaces except proxy-mode interfaces among its network interfaces except proxy-mode interfaces among its network
interfaces. interfaces.
Multilink-Subnet Router (MSR) Multilink-Subnet Router (MSR)
A router which has interfaces attached to different links in a A router which has interfaces attached to different links in a
MS, and which plays the role of ND-Proxy. MS, and which plays the role of ND-Proxy.
Recursive DNS Server (RDNSS) Recursive DNS Server (RDNSS)
A Recursive DNS Server is a name server that offers the A Recursive DNS Server is a name server that offers the
recursive service of DNS name resolution. recursive service of DNS name resolution.
2. Introduction 2. Introduction
The basic support of mobile network (NEMO) enables mobile network Recently, the demand and necessity of network mobility (NEMO) [3] is
nodes and correspondent nodes to communicate through bi-directional increasing along with those of host mobility based on Mobile IPv6
tunnels. The deeper multi-level network this NEMO gets, the longer (MIPv6) [9]. The purpose of network mobility is to guarantee the
the delay becomes by dog-legged routing. This document specifies how continuity of the sessions of fixed nodes or mobile nodes (MN) within
to optimize the routes between mobile nodes and correspondent nodes. mobile networks, such as car, bus, subway train, airplane and
Also, this document provides a way to optimize DNS name resolution of submarine. The current solution is based on bi-directional tunnel
mobile nodes, through the autoconfiguration of recursive DNS server. between home agent (HA) and mobile router (MR) [3]. The basic
support protocol of NEMO enables mobile network node (MNN) [7] and
correspondent node (CN) to communicate through the bi-directional
tunnel. Data exchange between MNN and CN is performed not via
optimal routing path, but via the non-optimal path including bi-
directional tunnel. MR's HA intercepts all of packets destined to
the MNNs and tunnels them to the MR. Also, the MNNs' outbound
packets are tunneled in order to pass ingress filtering [3][9]. This
mechanism is very simple but it gives up a powerful feature of MIPv6,
route optimization (RO) without ingress filtering. In addition, when
the mobile network has multiple nested MRs, packet delay between MNN
and CN becomes longer because of dog-legged routing and also packet
size becomes bigger due to extra IPv6 header attached to packet per
level of nesting [10].
When we think over the applicability of NEMO in our daily life, we
can forecast that network mobility service will be provided in
vehicles, such as bus, subway train and airplane, because most
passengers in such vehicles will have hand-held PC or PDA as MN
rather than fixed node in near future. Therefore, it is necessary to
provide route optimization for such MNs. This document describes a
way of optimizing the routes between MNs and CNs, independently of
the level of nesting and without the extra IPv6 header. The route
optimization mechanism is based on the proxying function of MR, which
informs MNs within mobile network of the access network prefix to
make a care-of address (CoA) passing ingress filtering, and also
relays packets between access router and MN. This proxying for RO is
performed through IPv6 Neighbor Discovery (ND), which is called ND-
Proxy.
3. Overview 3. Overview
+---+ ******************* +---+ +---+ ******************* +---+
|CN1+---* Internet *---+CN2| |CN1+---* Internet *---+CN2|
+---+ ******************* +---+ +---+ ******************* +---+
| |
| |
+-+-+ +-+-+
|AR1| |AR1|
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+---+ +---+ +---+ +-+-+ | RA(AR1_P) +---+ +---+ +---+ +-+-+ | RA(AR1_P)
Router-mode| V Router-mode| V
---+-----+-----+--- Link4 ---+-----+-----+--- Link4
| | | |
+-+-+ +-+-+ +-+-+ +-+-+
|MN4| |MN5| |MN4| |MN5|
+---+ +---+ +---+ +---+
Figure 1. Multilink Subnet for Route Optimization Figure 1. Multilink Subnet for Route Optimization
The route optimization is possible by mobile router's performing ND- The route optimization is possible by MR's performing ND-Proxy, which
Proxy, which makes a Care-of Address (CoA) with the prefix advertised makes a CoA with the prefix advertised by access router and relays
by access router and delivers the prefix of access network into the the prefix of access network into the whole mobile network. Each MN
NEMO. Each mobile node can make its new CoA with router can make its new CoA with router advertisement message including
advertisement message including access network prefix and perform the access network prefix and perform the return routability and binding
return routability and binding update procedure. As ND-Proxy, the update procedure. As ND-Proxy, the MR performs neighbor discovery
mobile router performs neighbor discovery instead of the mobile nodes for the sake of the MNs within its mobile network. Like this,
within its NEMO. Like this, through mobile router that performs ND- through MR that performs ND-Proxy, access network and mobile network
Proxy, access network and NEMO are configured into a multilink subnet. are configured into a multilink subnet. Figure 1 shows an example of
Figure 1 shows an example of a multilink subnet comprised of four a multilink subnet comprised of four links from Link1 to Link4. Two
links from Link1 to Link4. Three mobile routers from MR1 to MR3 MRs, MR1 and MR2, receive the prefix information of access network
relay the prefix information of access network (AR1_P) that was sent (AR1_P) that was sent by an access router, AR1 as proxy-mode and
by an access router, AR1. Let's assume that the mobile nodes MN1 and relay it to their subnet link as router-mode [6]. Let's assume that
MN2 move into the mobile network managed by mobile router MR1 like the MNs, MN1 and MN2, move into the mobile network managed by MR1
Figure 1. Also, let's assume that these visiting mobile nodes like Figure 1. Also, let's assume that these visiting mobile nodes
communicate with the correspondent nodes, CN1 and CN2, respectively. (VMN) communicate with the correspondent nodes, CN1 and CN2,
If these visiting mobiles can get the prefix of access network and respectively. If these visiting mobiles can get the prefix of access
make their new CoA, through the binding update with their network and make their new CoA, through the binding update with their
correspondent node, they can communicate each other via optimized correspondent node, they can communicate each other via an optimized
path. This dissemination of access network's prefix is performed by path. This dissemination of access network's prefix is performed by
mobile router which becomes attached to a foreign access network, not MR which becomes attached to a foreign access network, not its home
its home network. Likewise, MN3 can optimize the route through MR2. network. Likewise, MN3 can optimize the route through MR2. MN4 and
MN4 and MN5 can perform route optimization through MR2 and MR3, too. MN5 can perform route optimization through MR2 and MR3, too.
The optimization of DNS name resolution is possible by mobile The optimization of DNS name resolution is possible by MR's
router's announcing the address of local recursive DNS server as well announcing the address of local recursive DNS server as well as the
as the prefix information of access network. In Figure 1, by DNS prefix information of access network. In Figure 1, by DNS Server
Server option included in RA message, MR1 announces the address of option included in RA message, MR1 announces the address of Recursive
Recursive DNS Server, RDNSS1, within its mobile network to its DNS Server, RDNSS1, within its mobile network to its router-mode link,
router-mode link, Link2. Therefore, mobile nodes within Link2, MN1 Link2. Therefore, MNs within Link2, MN1 and MN2, can optimize their
and MN2, can optimize their DNS name resolution by using local DNS DNS name resolution by using local DNS server, RDNSS1.
server, RDNSS1.
4. Neighbor Discovery extension 4. Neighbor Discovery extension
In order to support the route optimization, ND implementation in MR
and MN must be extended to process the prefix information option for
RO and that in Local Fixed Node (LFN) within mobile network, which
has no mechanism for MIPv6, need no change.
4.1 RO Prefix Information option format 4.1 RO Prefix Information option format
The mechanism of this document needs the addition of a new flag The mechanism of this document needs a new O (Route-optimization)
within prefix information option for route optimization [3]. When flag within prefix information option for route optimization [4].
this flag is set, it indicates that the prefix included in the option When this flag is set on, it indicates that the prefix included in
can be used by mobile nodes within a NEMO for the route optimization. the option can be used by MNs within a mobile network for route
Figure 2 shows the format of the modified prefix information option, optimization. Figure 2 shows the format of the modified prefix
RO Prefix Information option, which is included in RA message. information option, RO Prefix Information option, which is included
in RA message.
0 1 2 3 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 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| | Type | Length | Prefix Length |L|A|O|Reserved1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime | | Valid Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preferred Lifetime | | Preferred Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. Prefix Information Option Format for Route Optimization Figure 2. Prefix Information Option Format for Route Optimization
Field: Field:
O 1-bit route-optimization flag. When set indicates O 1-bit route-optimization flag. When set indicates
that this prefix can be used for the route that this prefix can be used for the route
optimization of mobile nodes within NEMO. optimization of MNs within a mobile network.
The RO Prefix Information option provides a mobile node with the The RO Prefix Information option provides an MN with the network
network prefix of access network and allows it to autoconfigure its prefix of access network and allows it to autoconfigure its new CoA
new CoA through stateless address autoconfiguration and to perform through stateless address autoconfiguration and to perform binding
binding update. The Prefix Information option appears in RA message update. The Prefix Information option appears in RA message and MUST
and MUST be silently ignored for other messages. L (On-link) flag be silently ignored for other messages. L (On-link) flag MAY be
MAY be either 0 or 1. Namely, this route optimization can be either either 0 or 1. Namely, this route optimization can be either on-link
on-link or off-link model [5]. A (Autonomous address-configuration) or off-link model [6]. A (Autonomous address-configuration) flag
flag MUST be 1, indicating IPv6 stateless address autoconfiguration. MUST be set on, indicating IPv6 stateless address autoconfiguration.
4.2 Neighbor Solicitation (NS) message format 4.2 Neighbor Solicitation (NS) message format
NS message MUST be extended for Duplicate Address Detection (DAD) for NS message MUST be extended for Duplicate Address Detection (DAD) for
the address based on RO prefix of access network. Therefore, there the address based on RO prefix to be performed in the whole mobile
is a need to discriminate between the normal NS message and extended network, not just within a link. Therefore, there is a need to
NS message for route optimization [3]. Figure 3 shows the format of discriminate between the normal NS message and extended NS message
the modified NS message. for route optimization [4]. Figure 3 shows the format of the
modified NS message.
0 1 2 3 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 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 | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M| Reserved | |M| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
skipping to change at page 6, line 22 skipping to change at page 7, line 4
| | | |
+ + + +
| | | |
+ Target IPv6 Address + + Target IPv6 Address +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ... | Options ...
+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-
Figure 3. Extended Neighbor Solicitation Message Format Figure 3. Extended Neighbor Solicitation Message Format
Fields: Fields:
M 1-bit multi-hop flag. When set indicates M 1-bit multi-hop flag. When set indicates
that this NS message SHOULD be relayed to the other that this NS message SHOULD be relayed to the other
links of multilink subnet. links of a multilink subnet.
Target IPv6 Address Target IPv6 Address
The IPv6 address of the target of the solicitation The IPv6 address of the target of the solicitation,
that will be used as CoA. It MUST NOT be a e.g., CoA. It MUST NOT be a multicast address.
multicast address.
4.3 DNS Server option format 4.3 DNS Server option format
DNS Server option contains the IPv6 address of the recursive DNS DNS Server option contains the IPv6 address of the recursive DNS
server. When more than one DNS Server option are advertised, as many server. When advertising more than one DNS Server option, an RA
DNS Server options as DNS servers are included in an RA message. message includes as many DNS Server options as DNS servers. Figure 4
Figure 4 shows the format of DNS Server option [7]. shows the format of DNS Server option [8].
0 1 2 3 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 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 | Pref | Reserved | | Type | Length | Pref | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime | | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
| | | |
+ IPv6 Address of DNS Server + + IPv6 Address of DNS Server +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 7, line 25 skipping to change at page 8, line 7
Fields: Fields:
Type 8-bit identifier of the option type (TBD: IANA) Type 8-bit identifier of the option type (TBD: IANA)
Option Name Type Option Name Type
DNS Server (TBD) DNS Server (TBD)
Length 8-bit unsigned integer. The length of the Length 8-bit unsigned integer. The length of the
option (including the type and length fields) option (including the type and length fields)
in units of 8 octets. The value 0 is invalid. in units of 8 octets SHOULD be 0x03 (3 x 8 = 24
Mobile nodes MUST silently discard a Neighbor octets).
Discovery (ND) packet that contains an option
with length zero.
Pref The preference of a DNS server. A 4-bit unsigned Pref The preference of a DNS server. A 4-bit unsigned
integer. A decimal value of 15 indicates the integer. A decimal value of 15 indicates the
highest preference. A decimal value of 0 highest preference. A decimal value of zero
indicates that the DNS server can not be used. means unspecified. The field can be used for
The field can be used for selecting an RDNSS load balancing of DNS queries with multiple
among multiple RDNSSes. RDNSSes according to local policy.
Valid Lifetime 32-bit unsigned integer. The maximum time, in Lifetime 32-bit unsigned integer. The maximum time, in
seconds, over which this DNS server is used for seconds, over which this DNS server is used for
name resolution. Mobile nodes should contact the name resolution. MNs should contact the
source of this information, mobile router, before source of this information, MR, before
expiry of this time interval. A value of all one expiry of this time interval. A value of all one
bits (0xffffffff) represents infinity. bits (0xffffffff) represents infinity. A value
of zero means that the DNS server must not be
used any more.
IPv6 Address of DNS Server IPv6 Address of DNS Server
Recursive DNS Server's address for DNS name Recursive DNS Server's address for DNS name
resolution. resolution.
"Pref"=0 SHOULD require a "Valid Lifetime"=0 because the
corresponding DNS server SHOULD not be used any more.
5. Mobile Router 5. Mobile Router
Mobile router MUST process Prefix Information option for Route MR MUST process Prefix Information option for Route Optimization and
Optimization (RO) and DNS Server option for DNS Optimization, which DNS Server option for DNS Optimization, which may be included in RA
are included in RA message. message.
5.1 Process of RO Prefix Information option 5.1 Process of RO Prefix Information option
Only if the prefix announced by an access router is different from Only if the prefix announced by an access router is different from
the prefix of a mobile router's Home Address (HoA), the mobile router the prefix of an MR's Home Address (HoA), the MR MUST perform the
MUST perform the role of ND-Proxy and relay the prefix information. role of ND-Proxy and relay the prefix information. Before MR
Before mobile router advertises the prefix information through Router advertises the prefix information through Router Advertisement (RA)
Advertisement (RA) message, it MUST set route-optimization flag message, it MUST set O flag indicating that this prefix can be used
indicating that this prefix can be used for route optimization of for route optimization of MNs, which are either local mobile nodes
mobile nodes, which are either local mobile nodes or visiting mobile (LMN) or VMNs within the mobile network.
nodes within the mobile network.
If a mobile node within a mobile network receives the new prefix If an MN within a mobile network receives the new prefix information
information option through RA message and can recognize this option, option through RA message and can recognize this option, it MAY
it MAY prefer this new prefix information option to the normal prefix prefer RO prefix information option to normal prefix information
information option that contains the mobile network prefix assigned option that contains the mobile network prefix assigned by the MR's
by the mobile router's home network. By performing binding update home network. By performing binding update with the prefix of the
with the prefix of the access network, the mobile node can optimize access network, the MN can optimize the routes between its
the routes between its correspondent nodes and itself. correspondent nodes and itself.
ND-Proxy MUST join the solicited-node multicast address(es) that ND-Proxy MUST join the solicited-node multicast addresses that
correspond to the IP address(es) assigned to the mobile node for correspond to the IPv6 addresses assigned to MNs for which it is
which it is proxying [3]. proxying for processing ND messages related to the MNs [4].
5.2 Process of DNS Server option 5.2 Process of DNS Server option
If mobile router has its own local RDNSS like MR1 and MR2 in Figure 1, If MR has its own local RDNSS like MR1 and MR2 in Figure 1, it SHOULD
it SHOULD announce the address of RDNSS to its router-mode link(s). announce the address of RDNSS to its router-mode link(s).
If mobile router receives DNS Server option from its proxy-mode If MR receives DNS Server option from its proxy-mode link(s), it
link(s), it SHOULD relay the option to its router-mode link(s) SHOULD relay the option to its router-mode link(s) through its RA
through its RA message. In case that mobile router has its own local message. In the case where MR has its own local RDNSS, it announces
RDNSS, it announces the DNS Server option of its RDNSS with higher the DNS Server option of its RDNSS with higher precedence than those
precedence than those of other RDNSSes. of other RDNSSes.
5.3 Delivery of Data Packets 5.3 Delivery of Data Packets
After a mobile node gets a new CoA within a mobile network and After an MN gets a new CoA within a mobile network and performs
performs binding update associated with the address, the data packets binding update associated with the address, the data packets of
of correspondent node toward the mobile node are delivered to the correspondent node toward the MN can be delivered to the access
access network to which the NEMO containing the mobile node is network to which the mobile network containing the MN is attached,
attached, via optimal path between the mobile and correspondent nodes. via optimal path between the mobile and correspondent nodes.
When the access router of the access network receives the data When the access router of the access network receives the data
packets, it multicasts normal Neighbor Solicitation (NS) message to packets toward an MN and there is no neighbor information for the MN,
the solicited-node multicast address of the destination IPv6 address it multicasts normal Neighbor Solicitation (NS) message to the
in order to find out the link-layer address of the destination mobile solicited-node multicast address of the destination IPv6 address in
node. The mobile router, knowing the link-layer address of the order to find out the link-layer address of the destination MN. The
target, responds to the NS message by returning its own link-layer MR, knowing the link-layer address of the target, responds to the NS
address in a unicast Neighbor Advertisement (NA) message as ND-Proxy, message by returning its own link-layer address in a unicast Neighbor
which knows the IPv6 addresses and link-layer addresses of mobile Advertisement (NA) message as ND-Proxy, which knows the IPv6
nodes within its mobile network during the DAD of each CoA of each addresses and link-layer addresses of MNs within its mobile network
mobile node. while forwarding their data packets along with neighbor discovery
related to each destination node.
When the access router knows the link-layer address to the When the access router knows the link-layer address of next-hop
destination, it forwards the IPv6 data packets to the mobile router toward the destination MN, it forwards the IPv6 data packets to the
corresponding to the link-layer address. The mobile router relays MR corresponding to the link-layer address. The packets are relayed
the packets to the destination mobile node. In case that the NEMO to next-hop toward the destination node by MR until the packets
where the destination node is placed is multi-level, the packets are arrive at the destination. Like this, in the case where the mobile
relayed to the destination node by more than one mobile router. network where the destination node is placed is multi-level, the
packets may be relayed to the destination node by more than one MR
according to the route information in each MR's destination and
neighbor caches.
5.4 Movement of Mobile Router
When an MR moves into another access network and detects its movement
by movement detection algorithm [9], it performs binding update with
its HA with a new CoA based on the new access network prefix, and
then relays the prefix for RO into its other router-mode interfaces.
This allows the MRs and nodes to perform route optimization based on
the new access network prefix. When the MR returns to its home
network, it deregisters with its HA and advertises RA message that
contains RO Prefix Information option for the previous access network
prefix with Valid Lifetime and Preferred Lifetime set to zeroes and O
flag set on, and also Prefix Information option for MR's mobile
network prefix. The RO Prefix Information option SHOULD be
advertised at least three times. This RA message allows the MRs and
MNs below the MR explicitly to release their current CoA and to use
the MR's mobile network prefix in order to configure their addresses
according to MIPv6 protocol [9].
6. Mobile Node 6. Mobile Node
Mobile node MUST process Prefix Information option for Route MN MUST process Prefix Information option for RO and DNS Server
Optimization (RO) and DNS Server option for DNS Optimization, which option for DNS Optimization, which are included in RA message.
are included in RA message.
6.1 Procedure of Route Optimization 6.1 Procedure of Route Optimization
For route optimization, mobile node generates a new CoA based on the For RO, MN generates a new CoA based on the access network prefix and
access network prefix and performs binding update for the CoA. performs binding update for the CoA.
6.1.1 Generation of a new CoA 6.1.1 Generation of a new CoA
Whenever a mobile node receives RA message containing RO prefix Whenever an MN receives RA message containing RO prefix information
information option that includes a new network prefix of access option that includes a new network prefix of access network, it makes
network, it makes a new CoA. a new CoA.
6.1.2 DAD for the new CoA 6.1.2 DAD for the new CoA
The mobile node performs DAD for the new CoA through the extended NS The MN performs DAD for the new CoA through the extended NS message.
message. The NS message of DAD for the new address is relayed to the The NS message of DAD for the new address is disseminated by MRs,
other links by a mobile router, acting as ND-Proxy, on the link where acting as ND-Proxy, in the entire mobile network where the MN is
the mobile node is placed [5]. The mobile router memorizes the DAD placed [6]. Each MR memorizes the DAD for returning NA message to
for returning NA message to the sender of the extended NS message. the originator or relayer of the extended NS message for a while.
If there is no NA returned and the DAD is successful, the mobile node If there is no NA returned after DAD timeout, the MN configures the
configures the verified address as its new CoA in its network address as its new CoA in its network interface.
interface.
Notice that the DAD for the link-local addresses and global addresses Therefore, the DAD for the link-local addresses and global addresses
based on mobile network prefix assigned by home network is performed based on mobile network prefix assigned by home network is performed
through normal NS message only within a link and the DAD for the through normal NS message only within a link and the DAD for the
global addresses based on access network prefix is performed through global addresses based on access network prefix is performed through
extended NS message within a multilink subnet, which is relayed by extended NS message within a multilink subnet, which is relayed by
ND-Proxies. ND-Proxies.
6.1.3 Return Routability and Binding Update 6.1.3 Return Routability and Binding Update
After configuring the new CoA, the mobile node performs the return After configuring the new CoA, the MN performs the return routability
routability and binding update procedure of Mobile IPv6 [8]. If the and binding update procedure of MIPv6 [9]. If the MN is VMN for the
mobile node is visiting mobile node (VMN) for the mobile network mobile network where it is present, or as LMN, moves into another
where it is present, or as local mobile node (LMN), moves into link of the mobile network to which its home link belongs, it SHOULD
another link of the mobile network to which its home link belongs to, perform binding updates with both its HA and CNs.
it SHOULD perform binding updates with both its home agent and
correspondent nodes. In case that as LMN, the mobile node is present
at home link and receives RO prefix information option, namely when
the mobile node's HoA and CoA belong to the same link, it SHOULD
perform not deregistration with its home agent which is its mobile
router simultaneously, but binding updates with both its home agent
and correspondent nodes.
6.2 Procedure of DNS Optimization 6.2 Procedure of DNS Optimization
The optimization of DNS name resolution is possible by mobile The optimization of DNS name resolution is possible by MR's
router's announcing the address of local recursive DNS server as well announcing the address of local RDNSS along with RO prefix
as RO prefix information through RA message [7]. The DNS server can information through RA message like in Section 5.2 [8]. The DNS
exist either within mobile network or within access network. The server can exist either within mobile network or within access
address of recursive DNS server is delivered to mobile nodes through network. The address of RDNSS is delivered to MNs through DNS Server
DNS Server option, one of RA options. Especially, visiting mobile option, one of RA options. Especially, VMNs can optimize their DNS
nodes will optimize their DNS name resolution effectively by using name resolutions effectively by using a local RDNSS.
local recursive DNS server.
6.2.1 RDNSS Configuration
The addresses of DNS servers are announced by DNS Server options in
RA message. These addresses can be used for recursive DNS service
providing DNS name resolution. If mobile node receives DNS Server
option, it SHOULD store RDNSS's address in the configuration file for
its DNS resolver; i.e., /etc/resolv.conf in UNIX.
6.2.2 RDNSS Selection
When mobile node perceives multiple RDNSSes through RA message, it
stores the RDNSS addresses in order into the configuration file which
its DNS resolver uses for DNS name resolution on the basis of the
value of "Pref" field in the DNS Server option. The following
algorithm is simply based on the rule of selecting an RDNSS in the
order from the most preferred RDNSS, provided that its preference
value is not zero. The processing of the DNS Server option received
in RA message by a mobile node is as follows:
For each DNS Server option:
Step (a) : Receive and parse all DNS Server options.
Step (b) : Arrange the addresses of RDNSSes in a descending order, in
the respect of preference value, namely starting with the
biggest value of "Pref" field of the DNS Server option and
store them in the configuration file used by resolver for
DNS name Resolution (DNS configuration).
Step (c) : For each DNS Server option, check the following: If the
Value of "Pref" or "Valid Lifetime" field is set to zero,
exclude the corresponding RDNSS entry from the list of
RDNSSes of DNS configuration in order to let the RDNSS not
used any more.
Whenever the DNS resolver on the mobile node performs the name
resolution, it refers to the address of RDNSS in order from the first
RDNSS stored in its DNS configuration. Like this, in case that there
are several mobile routers advertising RDNSS in a multilink subnet,
"Pref" field is used to select RDNSS.
7. Security Considerations 7. Security Considerations
The route optimization and DNS optimization in this document does not The route optimization and DNS optimization in this document does not
add any other security problems to the NEMO, Mobile IPv6, or Neighbor add any other security problems to the NEMO, MIPv6, or ND protocol.
Discovery (ND) protocols. Security issues regarding the ND protocol Security issues regarding the ND protocol are being discussed in IETF
are being discussed in IETF SEND (Securing Neighbor Discovery) SEND (Securing Neighbor Discovery) working group [11].
working group [9].
8. Copyright 8. Copyright
The following copyright notice is copied from RFC 2026 [Bradner, The following copyright notice is copied from RFC 2026 [Bradner,
1996], Section 10.4, and describes the applicable copyright for this 1996], Section 10.4, and describes the applicable copyright for this
document. document.
Copyright (C) The Internet Society July 12, 2001. All Rights Copyright (C) The Internet Society July 12, 2001. All Rights
Reserved. Reserved.
skipping to change at page 12, line 31 skipping to change at page 12, line 25
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
9. Normative References 9. Normative References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996. 9, RFC 2026, October 1996.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[3] T. Narten, E. Nordmark and W. Simpson, "Neighbour Discovery for [3] Vijay Devarapalli et al., "Nemo Basic Support Protocol", draft-
ietf-nemo-basic-support-02.txt, December 2003.
[4] T. Narten, E. Nordmark and W. Simpson, "Neighbour Discovery for
IP version 6", RFC 2461, December 1998. IP version 6", RFC 2461, December 1998.
[4] S. Thomson and T. Narten, "IPv6 Stateless Address [5] S. Thomson and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998. Autoconfiguration", RFC 2462, December 1998.
[5] Dave Thaler and Chistian Huitema, "Multi-link Subnet Support in [6] Dave Thaler and Chistian Huitema, "Multi-link Subnet Support in
IPv6", draft-ietf-ipv6-multilink-subnets-00.txt, June 2002. IPv6", draft-ietf-ipv6-multilink-subnets-00.txt, June 2002.
[6] Thierry Ernst, "Network Mobility Support Terminology", draft- [7] T. Ernst and H.-Y. Lach, "Network Mobility Support Terminology",
ietf-nemo-terminology-00.txt, May 2003. draft-ietf-nemo-terminology-00.txt, May 2003.
[7] Jaehoon Jeong, Soohong D. Park, Luc Beloeil and Syam Madanapalli, [8] Jaehoon Paul Jeong et al., "IPv6 DNS Discovery based on Router
"IPv6 DNS Discovery based on Router Advertisement", draft-jeong- Advertisement", draft-jeong-dnsop-ipv6-dns-discovery-01.txt,
dnsop-ipv6-dns-discovery-00.txt, July 2003. February 2004.
10. Informative References 10. Informative References
[8] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in IPv6", [9] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in IPv6",
draft-ietf-mobileip-ipv6-22.txt, May 2003. draft-ietf-mobileip-ipv6-24.txt, June 2003.
[9] J. Arkko, J. Kempf, B. Sommerfeld, B. Zill and P. Nikander, [10] Pascal Thubert and Marco Molteni, "IPv6 Reverse Routing Header
"SEcure Neighbor Discovery (SEND)", draft-ietf-send-ipsec-01.txt, and its application to Mobile Networks", draft-thubert-nemo-
June 2003. reverse-routing-header-03.txt, October 2003.
[11] J. Arkko et al., "SEcure Neighbor Discovery (SEND)", draft-ietf-
send-ndopt-03.txt, January 2004.
11. Acknowledgements 11. Acknowledgements
The authors would like to acknowledge the previous contribution of The authors would like to acknowledge the previous contribution of
Dave Thaler and Christian Huitema. Dave Thaler and Christian Huitema for ND-Proxy.
12. Authors' Addresses 12. Authors' Addresses
Jaehoon Paul Jeong Jaehoon Paul Jeong
ETRI / PEC ETRI / PEC
161 Gajong-Dong, Yusong-Gu 161 Gajeong-dong, Yuseong-gu
Daejon 305-350 Daejon 305-350
Korea Korea
Phone: +82 42 860 1664 Phone: +82 42 860 1664
EMail: paul@etri.re.kr EMail: paul@etri.re.kr
Kyeong-Jin Lee Kyeongjin Lee
ETRI / PEC ETRI / PEC
161 Gajong-Dong, Yusong-Gu 161 Gajeong-dong, Yuseong-gu
Daejon 305-350 Daejon 305-350
Korea Korea
Phone: +82 42 860 6484 Phone: +82 42 860 6484
EMail: leekj@etri.re.kr EMail: leekj@etri.re.kr
Jung-Soo Park Jungsoo Park
ETRI / PEC ETRI / PEC
161 Gajong-Dong, Yusong-Gu 161 Gajeong-dong, Yuseong-gu
Daejon 305-350 Daejon 305-350
Korea Korea
Phone: +82 42 860 6514 Phone: +82 42 860 6514
EMail: pjs@etri.re.kr EMail: pjs@etri.re.kr
Hyoung-Jun Kim Hyoungjun Kim
ETRI / PEC ETRI / PEC
161 Gajong-Dong, Yusong-Gu 161 Gajeong-dong, Yuseong-gu
Daejon 305-350 Daejon 305-350
Korea Korea
Phone: +82 42 860 6576 Phone: +82 42 860 6576
EMail: khj@etri.re.kr EMail: khj@etri.re.kr
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