One document matched: draft-jeong-adhoc-ip-addr-autoconf-00.txt
Individual Submission
Internet Draft Jae-Hoon Jeong
Hyun-Wook Cha
Jung-Soo Park
Hyoung-Jun Kim
<draft-jeong-adhoc-ip-addr-autoconf-00.txt> ETRI
Expires: November 2003 27 May 2003
Ad Hoc IP Address Autoconfiguration
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].
Internet-Drafts are working documents of the Internet Engineering
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document specifies the steps a node in ad hoc network takes in
deciding how to autoconfigure its IPv4 or IPv6 address in network
interface. Because the ad hoc IP address autoconfiguration in this
document considers ad hoc network's partition and mergence, the
address duplication that can be caused by ad hoc network's mergence
can be resolved.
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..................................................3
3. Overview......................................................3
4. Message Format for Ad Hoc IP Address Autoconfiguration........4
4.1 Message Format for Ad Hoc IPv4 Address Autoconfiguration.4
4.2 Message Format for Ad Hoc IPv6 Address Autoconfiguration.5
5. Procedure of Ad Hoc IP Address Autoconfiguration..............6
5.1 Procedure of Ad Hoc IPv4 Address Autoconfiguration.......7
5.1.1 Procedure of Strong DAD............................7
5.1.2 Procedure of Weak DAD..............................7
5.2 Procedure of Ad Hoc IPv6 Address Autoconfiguration.......8
5.2.1 Procedure of Strong DAD............................9
5.2.2 Procedure of Weak DAD..............................9
6. Maintenance of Upper-layer Sessions under Address Duplication.9
7. Security Considerations......................................10
8. References...................................................10
9. Acknowledgements.............................................10
10.Authors' Addresses...........................................10
1. Terminology
This document uses the terminology described in [3][4]. In addition,
seven new terms are defined below:
Mobile Ad Hoc Network (MANET)
The network where mobile nodes can communicate with one another
without preexisting communication infrastructure, such as base
station or access point.
Duplicate Address Detection (DAD)
The process by which a node, which lacks an IP address,
determines address, determines whether a candidate address it
has selected is available. A node already equipped with an IP
address takes part in DAD in order to protect its IP address
from being accidentally used by another node.
Strong DAD
The timed-based DAD for the purpose of checking if there is
address duplication in a connected MANET partition within a
finite bounded time interval [5].
Weak DAD
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The DAD for the purpose of detecting address duplication during
ad hoc routing. Key is used for the purpose of detecting
duplicate IP addresses, which is selected to be unique by mobile
node. When mobile node receives a routing control packet, it
compares the pairs of address and key contained in the packet
with those in the routing table or cache [5].
Address Request (AREQ)
The message used during strong DAD for the purpose of checking
if there is another node having the requested address [6].
Address Reply (AREP)
The message used during strong DAD for the purpose of indicating
the requested address has already been utilized [6].
Address Error (AERR)
The message used during weak DAD for the purpose of indicating
that an address duplication happened or that the address of peer
node has been changed.
2. Introduction
IPv6 stateless address autoconfiguration [5] provides a way to
autoconfigure either fixed or mobile nodes with one or more IPv6
addresses and default routes. But this is not suitable for multi-hop
ad hoc networks that has dynamic network topology. Ad hoc networks
become partitioned and merged as intermediate nodes move. In this
environment, IPv6 stateless address autoconfiguration should be able
to process the address duplication not only within a connected ad hoc
partition, but also in the case that two partitions having duplicate
addresses respectively become merged. This document provides ad hoc
IP address autoconfiguration in IPv4 ad hoc network as well as in
IPv6 ad hoc network.
3. Overview
IPv4 or IPv6 unicast address of ad hoc node is autoconfigured by IP
address autoconfiguration for ad hoc networks. The configuration of
address is comprised of three steps; (a) selection of random address,
(b) verification of the uniqueness of the address and (c) assignment
of the address into network interface.
The duplication address detection (DAD) proposed in this document not
only check address duplication during the initialization of address
configuration, but also check and resolve address duplication during
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ad hoc routing by intermediate nodes. Also, during the resolution of
address conflict, the sessions using the conflicted address can be
maintained until the sessions are closed.
The DAD for ad hoc network in this document is a hybrid scheme
consisting of two phases; (a) Strong DAD phase and (b) Weak DAD phase.
Within a connected ad hoc partition, strong DAD checks if there is
any address duplication. During ad hoc routing, weak DAD checks if
address duplication has occurred when two or more MANET partitions
having duplicate addresses are merged.
4. Message Format for Ad Hoc IP Address Autoconfiguration
4.1 Message Format for Ad Hoc IPv4 Address Autoconfiguration
The mechanism of this document needs new ICMPv4 types for ad hoc IPv4
address autoconfiguration. Figure 1 shows the format of the messages
related to ad hoc address autoconfiguration.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator's IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Requested or Duplicate IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. Message Format for Ad Hoc IPv4 Address Autoconfiguration
Fields:
Type 8-bit identifier of the type of ICMPv4 message.
Message Name Type
AREQ (TBD)
AREP (TBD)
AERR (TBD)
Code 8-bit unsigned integer. As the code for message
type, the valid value is either 0 or 1. Code
value 1 in AERR message indicates that the peer
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node's address has been changed. In the other
cases, code value is always 0.
Checksum 16-bit unsigned integer. The checksum for the
ICMPv4 message and parts of the IPv4 header
Identifier 32-bit unsigned integer. The identifier for ad
hoc address autoconfiguration message is used to
prevent duplicate AREQ message from being flooded.
Originator's IPv4 Address
The IPv4 address of the sender of ad hoc address
autoconfiguration message.
Requested or Duplicate IPv4 Address
The requested IPv4 address in AREQ and AREP
messages, or the duplicate IPv4 address in AERR
message.
AREQ and AREP messages are used during strong DAD and AERR message
during weak DAD. Because AREQ message is forwarded by higher layer
than network layer through local broadcasting, "Identifier" field is
necessary.
4.2 Message Format for Ad Hoc IPv6 Address Autoconfiguration
The mechanism of this document needs new ICMPv6 types for ad hoc IPv6
address autoconfiguration. Figure 2 shows the format of the messages
related to ad hoc address autoconfiguration.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Originator's IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
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+ Requested or Duplicate IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. Message Format for Ad Hoc IPv6 Address Autoconfiguration
Fields:
Type 8-bit identifier of the type of ICMPv6 message.
Message Name Type
AREQ (TBD)
AREP (TBD)
AERR (TBD)
Code 8-bit unsigned integer. As the code for message
type, the valid value is either 0 or 1. Code
value 1 in AERR message indicates that the peer
node's address has been changed. In the other
cases, code value is always 0.
Checksum 16-bit unsigned integer. The checksum for the
ICMPv6 message and parts of the IPv6 header
Identifier 32-bit unsigned integer. The identifier for ad
hoc address autoconfiguration message is used to
prevent duplicate AREQ message from being flooded.
Originator's IPv6 Address
The IPv6 address of the sender of ad hoc address
autoconfiguration message.
Requested or Duplicate IPv6 Address
The requested IPv6 address in AREQ and AREP
messages, or the duplicate IPv6 address in AERR
message.
5. Procedure of Ad Hoc IP Address Autoconfiguration
The procedure of ad hoc IP address autoconfiguration in an ad hoc
node is comprised of two phases; (a) Strong DAD phase and (b) Weak
DAD phase.
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Because this document does not consider the global connectivity to
the Internet, it assumes that MANET is a temporary network isolated
from the Internet and the scope of addresses used in MANET is not
global, but local.
5.1 Procedure of Ad Hoc IPv4 Address Autoconfiguration
For IPv4 address, "169.254/16" is used as IPv4 MANET exclusive prefix,
IPV4_MANET_PREFIX [6]. Among IPV4_MANET_PREFIX, IPv4 addresses in the
range 1 ~ 2047 (TMP_ADDR) in the low-order 16 bits are used for
temporary IPv4 unicast address during strong DAD. The rest of
addresses in the range TMP_ADDR + 1 ~ 65534 in the low-order 16 bits
are used as tentative IPv4 address for actual IPv4 unicast address.
In the future, this prefix can be replaced with another one for ad
hoc network.
5.1.1 Procedure of Strong DAD
In the strong DAD phase, an ad hoc node autoconfigures a unique IPv4
address in its network interface as follows;
Step (a) : Node selects a temporary address and configures it in
network interface.
Step (b) : Node selects a tentative address and makes an AREQ message
for the address. Node initializes a variable for retransmission of
AREQ message, retrans_count, into 0.
Step (c) : Node broadcasts the AREQ message in IPv4 MANET broadcast
address, 255.255.255.255, and increases the count for transmission of
AREQ message, retrans_count by 1. It waits for AREP message until the
timer for strong DAD expires. If an AREP message for the sent AREQ
message arrives until the timer expires, node executes Step (e).
Otherwise, node executes Step (d).
Step (d) : If retrans_count is equal to 3, DAD_RETRIES, Node returns
to Step (f). Otherwise, it goes to Step (c).
Step (e) : If the received AREP message is associated with the sent
AREQ message, Node returns to Step (b).
Step (f) : Because the requested address that is tentative is unique
in the connected partition, node replaces the temporary address with
it as IPv4 unicast address of network interface.
5.1.2 Procedure of Weak DAD
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For weak DAD, virtual IP address is used, which is the combination of
IP address and key. In the weak DAD phase, ad hoc routing, an address
duplication is detected and resolved as follows;
Step (a) : Node is ready to receive address autoconfiguration message
or ad hoc routing control packet. Ad hoc routing protocol is either
proactive or reactive. If the received packet is address
autoconfiguration message, node executes Step (b). If the received
packet is ad hoc routing control packet, node executes Step (f).
Step (b) : If the address autoconfiguration message is AREQ, node
executes Step (c). If the message is AREP, node executes Step (d). If
the message is AERR, node executes Step (e).
Step (c) : If the message is what was received previously, node
discards the message. Otherwise, node compares its address with the
requested address in the message. If two addresses are the same, node
sends the originator node an AREP message indicating address
duplication. Otherwise, node floods the message to neighbors.
Step (d) : If the duplicate address in the AREP message is
corresponding to the address under tentative state during strong DAD,
node starts strong DAD procedure again. Otherwise, it discards the
message.
Step (e) : If the duplicate address in the AERR message is the same
as node's, node starts strong DAD procedure in order to autoconfigure
a new address again. Otherwise, it discards the message.
Step (f) : If the control packet is what was received previously,
node discards the packet. Otherwise, node investigates each virtual
IP address, consisting of IP address and key, contained in control
packet to see that there is the same pair in routing table or cache.
If there is the same pair, node sends an AERR message to the node
using duplicate address that is associated with a different key.
Otherwise, it executes the rest of the procedure related to
processing ad hoc routing control packets.
5.2 Procedure of Ad Hoc IPv6 Address Autoconfiguration
For IPv6 address, "fec0:0:0:ffff::/64" is used as IPv6 MANET
exclusive prefix, IPV6_MANET_PREFIX [6]. Among the IPV6_MANET_PREFIX,
"fec0:0:0:ffff::/96" is used as IPV6_MANET_INIT_PREFIX for temporary
unicast address during strong DAD. The low-order 32 bits of the
temporary address are configured with 32-bit pseudo random number.
IPV6_MANET_PREFIX except IPV6_MANET_INIT_PREFIX is used for actual
unicast address. The address is tentative address until the
uniqueness of it is verified by strong DAD.
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Recently, IPv6 site-local address has been deprecated by IPv6 working
group. Since IETF-56 meeting, IPv6 working group has been discussing
local prefix for local networks separated from the Internet, such as
ad hoc network [7]. If ad hoc prefix is determined by IPv6 working
group, IPV6_MANET_PREFIX will have the new one for ad hoc network.
5.2.1 Procedure of Strong DAD
In the strong DAD phase, an ad hoc node autoconfigures a unique IPv6
address in its network interface the same way as IPv4 Strong DAD
except that in Step (c), node sends the AREQ message by local
broadcast in IPv6 link-local scoped all-node multicast address,
ff02::1/64.
5.2.2 Procedure of Weak DAD
The IPv6 weak DAD phase is the same as the IPv4 weak DAD phase.
6. Maintenance of Upper-layer Sessions under Address Duplication
When address duplication happens and the duplicate address is
replaced with another, the sessions above network layer can be broken.
So, the survivability of upper-layer sessions using the duplicate
address SHOULD be guaranteed.
In order to allow data packets related to the sessions using the
duplicate address to be forwarded to destination nodes for a while,
after sending error message (i.e., AERR message) to the node related
to the duplicate address, the intermediate nodes that perceive
address duplication continue to forward data packets associated with
the sessions using the duplicate address until the route entry for
the duplicate address expires. The node that receives an AERR message
autoconfigures a new IPv6 address through strong DAD and makes the
new address used by the old upper-layer sessions that used the
duplicate address as well as new upper-layer sessions from this time
forward. The node informs the peer nodes of the change of address by
sending AERR messages with code 1. The "Originator's IP Address"
field contains the duplicate address and the "Requested IP Address"
field contains a new address to be used for the communication. After
receiving the AERR message, the peer node sends its packets to the
node through IP tunneling. The destination address in outer IP header
is the new IP address of the node that announced duplicate address
and that in inner IP header is the duplicate IP address of the node.
When the node receives tunneled packet from the peer node, it
decapsulates the packet and delivers the data in the packet to upper
layer. Both the node and peer nodes maintain the information of
duplicate address and use it for processing IP tunneling.
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7. Security Considerations
In order to provide secure ad hoc IP address autoconfiguration in ad
hoc network, we can use IPsec ESP with a null-transform to
authenticate ad hoc IP autoconfiguration messages or control packets,
which can be easily accomplished through the configuration of a group
pre-shared secret key for the trusted nodes.
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] Nitin H. Vaidya, "Weak Duplicate Address Detection in Mobile Ad
Hoc Networks", MobiHoc2002, June 2002.
[6] Charles E. Perkins, Jari T. Malinen, Ryuji Wakikawa, Elizabeth M.
Belding-Royer and Yuan Sun, "IP Address Autoconfiguration for Ad
Hoc Networks", draft-ietf-manet-autoconf-01.txt, November 2001.
[7] R. Hinden, "Globally Unique IPv6 Local Unicast Addresses", draft-
hinden-ipv6-global-local-addr-00.txt, May 2003.
9. Acknowledgements
The authors would like to acknowledge the previous contributions of
the following people; Charles E. Perkins, Jari T. Malinen, Ryuji
Wakikawa, Elizabeth M. Belding-Royer and Yuan Sun. In addition, the
important definitions (e.g., Strong DAD and Weak DAD) and mechanisms
for finding and resolving duplicate address have been derived from
Prof. Nitin H. Vaidya's work. Especially, we thank for his
contribution.
10. Authors' Addresses
Jae-Hoon Jeong
ETRI / PEC
161 Gajong-Dong, Yusong-Gu
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Daejon 305-350
Korea
Phone: +82 42 860 1664
EMail: paul@etri.re.kr
Hyun-Wook Cha
ETRI / PEC
161 Gajong-Dong, Yusong-Gu
Daejon 305-350
Korea
Phone: +82 42 860 1076
EMail: jafy@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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