MANET Autoconfiguration (AUTOCONF) Ilkyun Park
Internet-Draft ETRI
Expires: September 4, 2007 Younghan Kim
Namhi Kang
Soongsil University
Ho Young Song
ETRI
March 5, 2007
Address Autoconfiguration for Hybrid Mobile Ad Hoc Networks
draft-ikpark-autoconf-haa-03
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Copyright (C) The IETF Trust (2007).
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Abstract
Most of MANET address autoconfiguration mechanisms introduce
significant load like message flooding, or are dependent on the
underlying routing protocols. This document proposes a new mechanism
that is intended to minimize these drawbacks. It is also designed to
be applicable for hybrid MANET, where a MANET is connected to
Internet through one or more MANET border routers.
Table of Contents
1. Introduction 3
2. Terminology 4
3. IPv6 Address Autoconfiguration for Hybrid MANETs 6
3.1. Link-local DAD 6
3.2. Default Node Selection 6
3.3. HAA path 6
3.4. MANET-scope DAD and Global-scope Address Configuration 7
3.5. Autoconfiguration without MBR 8
4. HAA Message Formats 9
4.1. Default node option for RA message 9
4.2. Global Address Solicitation message 10
4.3. Node Address option for GS message 10
4.4. Global Address Advertisement message 11
4.5. Node confirm option for GA message 12
5. Security Considerations 14
6. Revision of the Draft 15
References 16
Author's Address 17
Intellectual Property Statement 18
Disclaimer of Validity 18
Copyright Statement 18
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1. Introduction
Mobile Ad Hoc Network (MANET) is a self-organized network by wireless
mobile nodes(MNs), without any pre-installed infrastructure. Its
topology is frequently changed due to the MNs' mobility. Therefore,
it is necessary to configure their addresses automatically.
"Hybrid MANET" is a mobile ad hoc network that has connectivity to
other networks, like the Internet. The connectivity is provided by
special MN called `MANET Border Router'. If MNs want to communicate
with nodes on the external networks, the configured addresses must be
globally unique.
Recently, several solutions have been proposed to autoconfigure
addresses to MNs [9]. Most of solutions exploit either an
independent algorithm and messages [5] or a mechanism combined with
underlying MANET routing protocol [6]. But they still have some
drawbacks. First, they introduce significant load like message full-
flooding over a MANET. Second, they are coupled with the routig
protocol and have more complex structure.
This document describes a mechanism of address autoconfiguration for
a hybrid MANET, called `Hybrid MANET Address Autoconfiguration'
(HAA). The mechanism is intended to minimize message full-flooding.
HAA autoconfigures IPv6 addresses to MNs by using IPv6 Neighbor
Discovery Protocol (NDP) [2-3] with some options and messages newly
defined here. After this autoconfiguration process, each MN has two
types of addresses: MANET-local address and global-scope address.
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2. Terminology
Some of the terminology was borrowed from MANET architecuture I-D
[13].
MANET Node (MN)
A MANET node includes a MANET router and zero or more hosts.
MANET Router (MR)
An entity that engages in a MANET routing protocol.
Duplicate Address Detection (DAD)
A process determining the uniqueness of an address to be
configured. If any MN has already used the same address, the MN
that has performed DAD process must select another address and
then execute DAD process again.
Hybrid MANET
A MANET with a connection to the Internet is refered to as a
hybrid MANET. Such a connectivity is provided by one or more
MANET Border Routers (MBRs). Every MN in hybrid MANET can have
multiple addresses to be accessible to variable scope of networks.
MANET-local Address
An address used in MANET-scope communications. MBRs do not
forward the packets that have MANET-local addresses as their
destination addresses. Unique local IPv6 unicast addresses (ULA)
[10] can be used easily as MANET-local addresses.
Global-scope Address
An address used in MANET- and global-scope communications. The
general format of IPv6 global-scope addresses is defined in IPv6
Address Architecture [11]. With this type of addresses, every MN
in hybrid MANET can access to another MN in the MANET and to any
host in the Internet.
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Hybrid MANET Address Autoconfiguration (HAA)
The mechanism that configures MANET-local address and global-scope
address to the MN in a MANET. Because each MN has the information
about MBR and the MBR maintains the information of MNs, MANET-wide
message broadcasting can be avoided.
MANET Border Router (MBR)
A router that participates in multiple routing domains. It
provides MANET with network connectivity to other networks, like
the Internet. MBR also performs MANET-scope DAD, and allocates
global-scope addresses to the MNs.
Default Node (DN)
If a MN has one or more HAA messages to be delivered to
corresponding MBR, the MN direct all messages to `Default Node'.
Only one of the MN's neighbors can be a default node. This DN
information is independent of any routing protocol.
HAA Path
If a MN wants to exchange address autoconfiguration messages with
its corresponding MBR, the MN sends the message to its default
node, one of its one-hop neighbors. The next hop MN then forwards
this message to its default node repeatedly. As a result, the
message is delivered to the MBR. `HAA path' is the chain of
default nodes among the MBR and the MNs. HAA path is regarded as a
tree path that has MBR as its root.
NDP Global Address Solicitation (GS)
This is a newly defined message here to deliver each MN's request
for the allocation of global-scope address and MANET-scope DAD.
NDP Global Address Advertisement (GA)
This is a newly defined message here to deliver MBR's response of
each MN's GS message. This contains the information about global-
scope address to be allocated, or an error if necessary.
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3. IPv6 Address Autoconfiguration for Hybrid MANETs
3.1. Link-local DAD
If a new MN A joins a MANET, the MN A makes its own link-local scope
address, and then determines the duplication of the address. To
detect address duplication, the MN A broadcasts NDP `Neighbor
Solicitation (NS)' message to all of 1-hop neighbors. If there is
not any NDP `Neighbor Advertisement (NA)' message for a period of
time, the MN A uses the link-local scope address to get a global-
scope address.
If there are one or more NDP NA messages, the MN A makes a new link-
local scope address with a 64-bit long random value as a MN ID
according to IPv6 Stateless Address Autoconfiguration (SAA) [3].
Then the MN A retries the link-local DAD by sending again a NDP NS
message containing the new link-local address.
3.2. Default Node Selection
If a newly joined MN A fixes its link-local address, then it tries to
get the information about the MBR and default node. For this, the MN
A sends NDP `Router Solicitation (RS)' message to all of 1-hop
neighbors.
Each neighbor that receives the MN A's RS message responses with NDP
`Router Advertisement (RA)' message like a router of wired networks.
In this RA message, a newly defined 'Default Node' option is
attached. This option containes the addresses of MBR and default
node (e.g. the sender of this message), the path length measured in
hop counts between the MBR and the default node, and the lifetime of
the information about default node.
The MN A then receives one or more RA messages. It selects one among
these messages by searching the address of MBR and hop counts. For
example, if MN B, C, and D send RA messages and the MN B's RA message
has the shortest hop counts to the corresponding MBR, the MN A
selects the RA message generated by the MN B.
If there is no RA message during a period of T_WAIT_RA seconds, then
the MN A retries to send RS message. If there is still no RS message
during N_RETRY_RS times retrial, then the MN A stops HAA process.
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3.3. HAA path
If the MN A gets the addresses of MBR and default node, it
participates in `HAA path'. At the begining of building a hybrid
MANET, there is one MN that is MBR as infrastructure providing
Internet connectivity. When there is not any MN except MBR, a newly
joined MN does DAD with MBR and gets the MBR's address as a default
node. As the following MNs are joined, each of MNs takes the former
MN's address as a default node. As a result, HAA path becomes a tree
path that has MBR as its root.
The HAA path is used for the porpose of address autoconfiguration
only. Each MN's path toward MBR is independent of any routing
protocol, but this HAA path infomation can be used by a routing
protocol if needed.
3.4. MANET-scope DAD and Global-scope Address Configuration
Once a MN A acquires the information about MBR and default node, it
can request the allocation of global-scope address by sending `Global
Solicitation (GS)' message to MBR. GS message is newly defined here
as an extension to IPv6 NDP. This message has the `Node Address'
option that contains the address of the MN A. GS message is
forwarded to the default node of each MN repeatedly, along the HAA
path.
If the HAA path contains the loop by the mobility of some MNs, GS
message will be silently dropped when its hop limit is decreased to
0. Then the MN can detect the loop, and change or remove the invalid
default node. If the loop is created in transient, the loop path is
fixed before the GS message's hop limit becomes 0.
If MBR receives the NDP GS message, then it performs MANET-scope DAD
by comparing the MN A's address contained in GS message to the
addresses from the list of registered MNs.
If there is no duplicate address used by the MN A's, then MBR sends
NDP `Global Advertisement (GA)' message. This message is defined as
an extension to NDP like GS message. It contains the global-scope
address to be allocated to the MN A, and the length of prefix of its
address. If the MN A receives the message, then the MN sets its
address to the global-scope address.
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If an address duplication is detected, then MBR sends the global-
scope address allocation error message instead. This message uses
the form of NDP GA message, but sets bit E to 1. If the MN A
receives that, it generates a new address and try again.
Both GS and GA messages traverse along HAA path and are unicast
messages. And message broadcasts are limited to 1-hop range, so the
message overhead due to the HAA mechanism is relatively low.
3.5. Autoconfiguration without MBR
A MANET can lose its MBR if all MNs of the MANET are moved out of the
radio range of the MBR. By the absence of the MBR, allocation of
global-scope address and its DAD procedure, and Internet connectivity
become unavailable. If any MN in the MANET cannot receive periodical
GA messages from the MBR, it stops the use of its global-scope
addresses and disconnects the sessions that were created using
global-scope addresses previously. In contrary, the MN keeps its own
MANET-local address. Abitrary MNs can join to and leave from MBR-
less MANET, so periodical DAD process for MANET-local address is
required. But MANET-local addresses use the format of Unique local
address (ULA), that is combined with pre-defined prefix for MANET and
interface identifier built from EUI-64. Hence, optimistic DAD [12]
can be used for the check of duplication of MANET-local addresses.
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4. HAA Message Formats
4.1. Default node option for RA 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 | Length | Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Default Node Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Default Node Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ MBR Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
TBD
Length
8-bit unsigned integer. The length of the option in unit of 8
octets. The value 0 is invalid.
Hop Count
16-bit unsigned integer. The number of hops between MBR and the
sender of this message.
Default Node Lifetime
32-bit unsigned integer and the length of time in seconds that
this default node option is valid. The default value is TBD.
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Default Node Address
An IPv6 address. This field contains the address of recommended
MN as a default node.
MBR Address
The IPv6 address of MBR of the MANET in which the MN is partici-
pated.
4.2. Global Address Solicitation 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
Type
TBD
Code
TBD
Checksum
The ICMP checksum.
Reserved
This field is unused.
4.3. Node Address option for GS 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 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
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+ +
| |
+ Node Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
TBD
Length
8-bit unsigned integer. The length of the option in unit of 8
octets. The value 0 is invalid.
Reserved
This field is unused.
Identifier
32-bit unsigned integer. This field separates one request of
global-scope address from the others. MBR generates the response
message for this message with the same identifier. The value is
randomly generated.
Node Address
IPv6 link-local address of the sender.
4.4. Global Address Advertisement 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | MBR Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
Type
TBD
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Code
TBD
Checksum
The ICMP checksum.
Reserved
This field is unused.
MBR Lifetime
32-bit unsigned integer and the length of time in seconds that the
global address contained in this message is valid. The default
value is TBD.
4.5. Node confirm option for GA 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 | Length |E| Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Node Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
TBD
Length
8-bit unsigned integer. The length of the option in unit of 8
octets. The value 0 is invalid.
E
1-bit field that represents if there is an error or not in the
request. E bit is set to 1 if duplicate address is detected.
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Prefix Length
16-bit unsigned integer. The length of global-scope prefix.
Identifier
32-bit unsigned integer. The field separates one request of
global-scope address from the others. MBR generates the response
message for this message with same identifier. The value is ran-
domly generated.
Node Address
IPv6 global-scope address to be allocated to the requester.
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5. Security Considerations
This document does not describe any security facility of the hybrid
address autoconfiguration. A malicious MN may block the process by
misdirecting some of the HAA messages, or make a newly joined MN con-
figure its address with invalid information.
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6. Revision of the Draft
Version 3 of the draft has been revised as follows.
- Section 2 `Terminology' was been updated.
- Terminology of MANET entities were been changed.
- New reference [13] was been added.
Version 2 of the draft has been revised as follows.
- Section 2 `Terminology' was been updated.
- Section 3.5 `Autoconfiguration without Internet Gateway' was been
updated.
Version 1 of the draft has been revised as follows.
- This section was beed appended.
- Section 3.5 `Autoconfiguration without Internet Gateway' was been
appended.
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References
[1] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels," RFC 2119, Internet Engineering Task Force, March 1997.
[2] T. Narten, E. Nordmark, and W. Simpson. "Neighbor Discovery for IP
Version 6 (IPv6)," RFC 2461, Internet Engineering Task Force,
December 1998.
[3] S. Thomson and T. Narten. "IPv6 Stateless Address Autoconfigura-
tion," RFC 2462, Internet Engineering Task Force, December 1998.
[4] R. Wakikawa, J. Malinen, C. Perkins, A. Nilsson, and A. Tuominen,
"Internet Connectivity for Mobile Ad hoc networks," Internet Draft,
draft-wakikawa-manet-globalv6-02.txt, November 2002.
[5] C. Perkins, J. Malinen, R. Wakikawa, E. Belding-Royer, and Y. Sun,
"IP Address Autoconfiguration for Ad Hoc Networks," Internet Draft,
draft-ietf-manet-autoconf-01.txt, Nov. 2001, work in progress.
[6] J. Jeong, "Ad Hoc IP Address Autoconfiguration," Internet Draft,
draft-jeong-adhoc-ip-addr-autoconf-00.txt, Nov. 2003, work in
progress.
[7] S. Ruffino, P. Stupar, and T. Clausen, "Autoconfiguration in a
MANET: connectivity scenarios and technical issues," Internet
Draft, draft-ruffino-manet-autoconf-scenarios-00.txt, October 2004,
work in progress.
[8] S. Singh, J. Kim, C. Perkins, P. Ruiz, and T. Clausen, "Ad Hoc Net-
work Autoconfiguration: Definition and Problem Statement," Internet
Draft, draft-singh-autoconf-adp-00.txt, Feb. 2005, work in
progress.
[9] C. Bernardos and M. Calderon, "Survey of IP address autoconfigura-
tion mechnisms for MANETs," Internet Draft, draft-bernardos-manet-
autoconf-survey-00.txt, July 2005, work in progress.
[10] R. Hinden and B. Haberman, "Unique Local IPv6 Unicast Addresses,"
RFC 4193, Internet Engineering Task Force, October 2005.
Park, et al., Expires September 4, 2007 [Page 16]
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[11] R. Hinden and S. Deering, "IP Version 6 Addressing Architecture,"
RFC 4291, Internet Engineering Task Force, February 2006.
[12] N. Moore, "Optimistic Duplicate Address Detection (DAD) for IPv6,"
RFC 4429, Internet Engineering Task Force, April 2006.
[13] I. Chakeres, J. Macker, and T. Clausen, "Mobile Ad hoc Network
Architecture," Internet Draft, draft-ietf-autoconf-
manetarch-00.txt, Feb. 2007, work in progress.
Author's Address
Ilkyun Park
Electronics and Telecommunications Research Institute, S. Korea
Phone: +82 62 970 6651
Email: ikpark@etri.re.kr
Younghan Kim
Soongsil University, S. Korea
Phone: +82 2 820 0904
Email: yhkim@dcn.ssu.ac.kr
Namhi Kang
Soongsil University, S. Korea
Phone: +82 2 820 0904
Email: nalnal@dcn.ssu.ac.kr
Ho Young Song
Electronics and Telecommunications Research Institute, S. Korea
Phone: +82 62 970 6720
Email: hsong@etri.re.kr
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