MANET Autoconfiguration (AUTOCONF) Ilkyun Park
Internet-Draft Younghan Kim
Expires: April 22, 2007 Namhi Kang
Soongsil University
October 23, 2006
Address Autoconfiguration for Hybrid Mobile Ad Hoc Networks
draft-ikpark-autoconf-haa-02
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Copyright (C) The Internet Society (2006).
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Abstract
Most of current address autoconfiguration mechanisms for MANET
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 Interet gateways.
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 Internet Gateway 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 15
6. Revision of the Draft 16
References 16
Author's Address 17
Intellectual Property Statement 17
Disclaimer of Validity 18
Copyright Statement 18
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1. Introduction
A Mobile Ad Hoc Network (MANET) is self-organized by wireless mobile
nodes, without any pre-installed infrastructures. Data packets are
delivered by multi-hop communication of nodes. A topology of MANET
is changed frequently due to the nodes' mobility. Therefore, it is
necessary to configure their addresses automatically.
"Hybrid MANET" is a mobile ad hoc network that has connectivity to
external networks. The connectivity is provided by special node
called `Internet gateway'. If MANET nodes 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 MANET nodes [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 MANET nodes by using IPv6
Neighbor Discovery Protocol (NDP) [2-3] with some options and
messages newly defined here. After this autoconfiguration process,
each mobile node has two types of addresses: MANET-local address and
global-scope address.
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2. Terminology
Duplicate Address Detection (DAD)
The process to determine the uniqueness of an address to be
configured. If any node has already used the same address, the
node 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
Internet Gateways. Every node 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. Internet gateways
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
node in hybrid MANET can access to another node in the MANET and
to any host in the Internet.
Hybrid MANET Address Autoconfiguration (HAA)
The mechanism that configures MANET-local address and global-scope
address to the nodes in a MANET. Because each node has the
information about Internet gateway and next hop toward the gateway
and Internet gateway maintains the information of MANET nodes,
MANET-wide message broadcasting can be avoided.
Internet Gateway (IG)
The relaying node that provides Internet connectivity with the
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MANET nodes. IG also performs MANET-scope DAD by maintaining the
list of its MANET nodes. In addition, IG allocates global-scope
addresses to the nodes in the MANET.
Default Node (DN)
If a node has one or more HAA messages to be delivered to
corresponding IG, the node direct all messages to `Default Node'.
Only one of the node's neighbors can be a default node. This DN
information is independent of any routing protocol.
HAA Path
If a node wants to exchange address autoconfiguration messages
with its corresponding IG, the node sends the message to its
default node, one of its one-hop neighbors. The next hop node
then forwards this message to its default node repeatedly. As a
result, the message is delivered to the IG. `HAA path' is the
chain of default nodes among the IG and the nodes. HAA path is
regarded as a tree path that has IG as its root.
NDP Global Address Solicitation (GS)
This is a newly defined message here to deliver each node'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 IG's response of
each node'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 node A joins a MANET, the node A makes its own link-local
scope address, and then determines the duplication of the address.
To detect address duplication, the node 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 node A uses the link-local scope address to get a global-
scope address.
If there are one or more NDP NA messages, the node A makes a new
link-local scope address with a 64-bit long random value as a node ID
according to IPv6 Stateless Address Autoconfiguration (SAA) [3].
Then the node 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 node A fixes its link-local address, then it tries
to get the information about the MANET's Internet gateway and default
node. For this, the node A sends NDP `Router Solicitation (RS)'
message to all of 1-hop neighbors.
Each neighbor that receives the node 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 Internet gateway
and default node (e.g. the sender of this message), the path length
measured in hop counts between the Internet gateway and the default
node, and the lifetime of the information about default node.
The node A then receives one or more RA messages. It selects one
among these messages by searching the address of Internet gateway and
hop counts. For example, if node B, C, and D send RA messages and
the node B's RA message has the shortest hop counts to the
corresponding IG, the node A selects the RA message generated by the
node B.
If there is no RA message during a period of T_WAIT_RA seconds, then
the node A retries to send RS message. If there is still no RS
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message during N_RETRY_RS times retrial, then the node A stops HAA
process.
3.3. HAA path
If the node A gets the addresses of Internet gateway and default
node, it participates in `HAA path'. At the begining of building a
hybrid MANET, there is one node that is Internet gateway as
infrastructure providing Internet connectivity. When there is not
any user node except Internet gateway, a newly joined node does DAD
with Internet gateway and gets the Internet gateway's address as a
default node. As the following nodes are joined, each of nodes takes
the former node's address as a default node. As a result, HAA path
becomes a tree path that has Internet gateway as its root.
The HAA path is used for the porpose of address autoconfiguration
only. Each node's path toward Internet gateway 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 node A acquires the information about Internet gateway and
default node, it can request the allocation of global-scope address
by sending `Global Solicitation (GS)' message to Internet gateway.
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 node A. GS message is forwarded to the default node of each node
repeatedly, along the HAA path.
If the HAA path contains the loop by the mobility of some nodes, GS
message will be silently dropped when its hop limit is decreased to
0. Then the node 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 Internet gateway receives the NDP GS message, then it performs
MANET-scope DAD by comparing the node A's address contained in GS
message to the addresses from the list of registered nodes.
If there is no duplicate address used by the node A's, then Internet
gateway sends NDP `Global Advertisement (GA)' message. This message
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is defined as an extension to NDP like GS message. It contains the
global-scope address to be allocated to the node A, and the length of
prefix of its address. If the node A receives the message, then the
node sets its address to the global-scope address.
If an address duplication is detected, then Internet gateway 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
node 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 Internet Gateway
A MANET can lose its gateway if all nodes of the MANET are moved out
of the radio range of the gateway. By the absence of the gateway,
allocation of global-scope address and its DAD procedure, and
Internet connectivity become unavailable. If any node in the MANET
cannot receive periodical GA messages from the gateway, it stops the
use of its global-scope addresses and disconnects the sessions that
were created using global-scope addresses previously. In contrary,
the node keeps its own MANET-local address. Abitrary nodes can join
to and leave from gateway-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 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Internet Gateway 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 Internet
gateway 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
node as a default node.
Internet Gateway Address
The IPv6 address of Internet gateway of the MANET in which the
node is participated.
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. Internet gateway 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 | Gateway Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
Type
TBD
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Code
TBD
Checksum
The ICMP checksum.
Reserved
This field is unused.
Gateway 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. Internet gateway generates
the response message for this message with same identifier. The
value is randomly 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 node may block the process by
misdirecting some of the HAA messages, or make a newly joined node
configure its address with invalid information.
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6. Revision of the Draft
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 April 22, 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.
Author's Address
Ilkyun Park
Soongsil University, S. Korea
Phone: +82 2 820 0904
Email: ikpark@dcn.ssu.ac.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
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