autoconf Working Group Jaehwoon Lee
Internet-Draft Dongguk University
Intended status: Informational Sanghynn Ahn
Expires: August 27, 2010 University of Seoul
Younghan Kim
Soongsil University
February 28, 2010
Address Autoconfiguration for MANET with Multiple MBRs
draft-jaehwoon-autoconf-mmbr-02.txt
Abstract
In order to allow the subordinate MANET to be connected to the
external network, the MANET border router (MBR) has been defined. For
providing scalability and reliability to the subordinate MANET,
multiple MBRs may be deployed. One of the issues on the subordinate
MANET with multiple MBRs is which network prefixes are to be
advertised by MBRs. In the case when MBRs advertise different network
prefixes, if a MANET node changes its default MBR to a new one, the
node may have to transmit packets via non-optimal paths to keep using
the existing connection to the previous MBR, or change its address by
using the network prefix information from the new MBR.
In the former case, the MANET node may not communicate with the MBR
due to MANET partitioning. In the latter case, on-going sessions can
be terminated because of the address change. In this draft, we define
a PMIPv6 based address autoconfiguration mechanism that enables MANET
nodes to operate properly when all MBRs advertise the same network
prefix in the subordinate MANET.
Status of this Memo
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Internet-Draft Address Autoconfiguration for multiple MBRs Feb. 28, 2010
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Table of Contents
1. Introduction..................................................3
2. Terminology...................................................4
3. Message format................................................4
3.1 Registration Request message..............................4
3.2 Registration Confirmation message.........................4
4. Protocol operation............................................4
5. Security Considerations.......................................7
6. IANA Considerations...........................................7
References.......................................................7
Author's Addresses...............................................8
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1. Introduction
The mobile ad hoc network (MANET) enables mobile nodes to communicate
via multiple wireless hops without the need of any wired
infrastructure. In a MANET, two nodes not within transmission
range have to deliver data to each other through other intermediate
nodes. For forwarding packets destined to other nodes, each node must
have the routing capability, i.e., the mechanism for establishing
data delivery routes between any pair of source and destination
nodes. The IETF MANET working group has defined route setup
mechanisms for delivering data between MANET nodes. Especially for an
ad hoc network such as the MANET, the mechanism that can allow
nodes to configure their addresses autonomically is more desirable
than the static address configuration mechanism since the former has
less configuration and management overhead due to its omission of
manual intervention.
MANETs can be classified into the subordinate MANET or the
autonomous MANET depending on whether it is connected to the external
network or not [1]. The MANET border router (MBR) which is a gateway
device connecting the MANET with the external network has been
defined for the subordinate MANET. As the number of nodes in the
MANET increases, the amount of traffic between the MANET and the
Internet increases, so the MBR gets overloaded, resulting in the
overall network performance degradation. To overcome this problem,
multiple MBRs can be used for the Internet connectivity [2].
Mechanisms in which each MBR advertises a different network prefix
have been proposed for the MANET with multiple MBRs [3-4]. However,
in these mechanisms, if a node moves to another place, it sends
packets via non-optimal paths to maintain its connection to the
previous MBR, or it changes its address by using the network prefix
delivered from the new MBR. An on-going session may get terminated
because of MANET partitioning in the formal case or the address
change in the latter case.
In this draft, we define an address autoconfiguration mechanism for
the subordinate MANET with multiple MBRs which advertise the same
network prefix. In the proposed mechanism, since all MBRs advertise
the same network prefix, even a node moves it can still use its
preconfigured address. That means that no address reconfiguration
is needed in case of node movement, so the proposed mechanism has
the advantage of keeping on maintaining its existing session(s).
Furthermore, under node movement, a node can still find an optimized
path without changing its address because it can choose the MBR
that can be reached via the minimum number of hops.
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2. Terminology
TBD.
3. Message Format
3.1 Registration Request (RR) Message
TBD
3.2 Registration Confirmation (RC) Message
TBD
4. Protocol Operation
MN MBR1(MAG1) MBR2(MAG2) LMA (Internet) CN
| | | | |
|<----------| | | |
ICMP SERA message | | |
(Configure IPv6 address to MANET interface) | |
|<--------->| | | |
(DHCP with prefix delegation) | | |
|---------->| | | |
|RR message | | | |
| |---------------------------------->| |
| | PBU message (Create Binding Cache Entry) |
| |<----------------------------------| |
| | PBAck message | |
|<----------| | | |
|RC message | | | |
|<--------->|<=================================>|<------------>|
| Data packet transfer between MN and CN via MBR1 and LMA |
(MN changes its default gateway from MBR1 to MBR2) | |
|<---------------------------| | |
| ICMP SERA message | | |
|--------------------------->| | |
| RR message | | |
| | |----------------->| |
| | | PBU message | |
| | | (Update Binding Cache Entry |
| | |<-----------------| |
| | | PBAck message | |
|<---------------------------| | |
| RC message | | |
|<-------------------------->|<================>|<------------>|
| Data packet transfer between MN and CN via MBR2 and LMA |
| | | | |
Figure 1: Message exchange scenario
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The message exchange scenario considered in this draft is depicted
in figure 1. The network is composed of the external network such as
the global Internet, a PMIPv6 domain and a MANET. The operation of
the PMIPv6 protocol is defined in [5]. In the PMIPv6 domain, a local
mobility anchor (LMA) is located and acts as a kind of home agent
(HA). The MANET can be connected to the PMIPv6 domain through a
multiple number of mobility access gateways (MBRs) and an MBR
operates as a mobility access gateway (MAG) in the PMIPv6 domain.
One network prefix is assigned to the MANET, and each MBR
periodically advertises scope-extended Router Advertisement
(SERA) messages to the entire MANET [6]. The SERA message is defined
to resolve the duplicate packet reception problem which can occur in
a multi-hop wireless network such as the MANET. The network prefix
assigned to the MANET and the address of the MBR originating the
SERA message are included in the message. Even though the different
MBR address information is included in the SERA message sent by
different MBR, the network prefix that can be delived by subnet
masking the MBR address with the prefix length is the same. In other
words, the MBRs connecting the MANET and the global Internet
advertise the same network prefix.
When a MANET node (MN) connects to the MANET for the first
time, it waits for a SERA message from a MBR. Assume that the SERA
message from MBR1 arrives at the MN first. Then the MN configures
the IPv6 address of its MANET interface by utilizing the stateless
address autoconfiguration mechanism based on its MAC address and
the network prefix obtained from the MBR1 address and the network
prefix length [7]. After that, the MN sets the MBR1 address in the
SERA message as the address of its default gateway, and stores the
distance to MBR1 which can be calculated with
'255 - the Cur Hop Limit in the scope-extended RA message + 1'
in its routing table. In addition to that, the MN sets the value in
the source IP address field of the IP packet having the received
SERA message as the next-hop address to its default gateway and
records this information in its routing table. Then, the MN decreases
the Cur Hop Limit value in the received SERA message by 1 and
broadcasts the modified SERA message. Also, the MN sends a
Registration Request (RR) message to MBR1. Upon receiving the RR
message, MBR1 sends a Proxy Binding Update (PBU) message with the
MN address to the LMA. The LMA stores the binding information for
the MN and MBR1 and sends a Proxy Binding Acknowledgement (PBAck)
message to MBR1. After that, a tunnel between the LMA and MBR1 is
established for the MN. After receiving the PBAck message from the
LMA, MBR1 sends a Registration Confirmation (RC) message to the MN.
Now, MBR1 becomes the default gateway for the node and the MN can
communicate with any host in the global Internet. The MN uses the
IP-in-IP encapsulation or routing header in order for the traffic
sent from the MN to be delivered to the default gateway of the node.
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If MBR1 receives a packet from the MN, it transmits the packet to the
LMA via the established tunnel which, in turn, forwards it to the
destination host in the global Internet.
Since SERA messages are periodically advertised by each MBR, a node
can receive multiple SERA messages advertised by other MBRs even
after it has configured an IPv6 address of is interface. The
operation of a MN receiving a SERA message is as follow. Once a
MN receives a SERA message broadcasted by the neighbor node which is
set as the next-hop node to its default gateway, the MN updates its
corresponding routing table entry using the information in the
received SERA message. That is, the MN determines the distance to its
default gateway based on the Cur Hop Limit value in the SERA message.
If the MBR address (i.e., MBR2) in the SERA message is different from
its current default gateway, the MN sends a RR message to MBR2 and
broadcasts the SERA message throught the MANET. If the MN receives a
RC message from MBR2, it updates its routing table entry related to
the default gateway information.
If the MN receives a SERA message from another neighbor node which is
not the next-hop node to the default gateway, the MN compares the
distance to the MBR having sent the SERA message (which can be
computed from the CUR Hop Limit valued in the SERA message) and that
to its default gateway. If the fomer one is larger than or equal to
the latter, it discards the received SERA message. Otherwise, after
broadcasting the SERA message, it updates its corresponding routing
table entry based on the information in the received SERA mesage as
follows. At first, the MN checks the MBR address in the SERA message.
If the MBR address in the SERA message is the same as its current
default gateway, the MN changes the distance to the default gateway
to the distance value obtained from the SERA message and sets the
node sending the SERA message as the next-hop node to the default
gateway.
If the MBR address (i.e., MBR2) in the SERA message is different from
the address of its default gateway, the MN sends a RR message to
MBR2. If the MN receives a RC message for MBR2, it updates its
routing table entry related to the default gateway information. In
this case, even when the default gateway is changed, the network
prefix for the MANET is kept the same, so the MN can keep on
maintaining its on-going session(s) because it can still use its
IPv6 address configured on its MANET interface. Furthermore, even if
the MN changes its default gateway, the IPv6 address configured on
its MANET interface is kept the same. Thus, if the packets from a
host in the Internet arrive at the MBR chosen as its previous default
gateway before the registration process is completed, they can be
delivered to the MN via the previous default gateway, so no packet
loss due to address changes will happen.
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If the MN does not receive a SERA message from its next-hop node to
the default gateway for some time duration or it determines that the
next-hop node is no more its neighbor node, the MN deletes the
default gateway related entry from its routing table.
5. Security Consideration
TBD.
6. IANA Considerations
TBD.
References
[1] E. Baccelli et al., "Address Autoconfiguration for MANET:
Terminology and Problem Statement", draft-ietf-autoconf-
statement-04, Work in progress, Feb. 2008.
[2] S. Ruffino, P. Stupar and T. Clausen, "Autoconfiguration in a
MANET: connectivity scenarios and technical issues", draft-
ruffino-manet-autoconf-scenarios-00, work in progress, Oct. 2004.
[3] S. Ruffino and P. Stupar, "Automatic configuration of IPv6
addresses for MANET with multiple gateways (AMG)",
draft-ruffino-manet-autoconf-multigw-03, work in progress,
June 2006.
[4] C. Jelger, T. Noel and A. Frey, "Gateway and address
autoconfiguration for IPv6 adhoc networks", draft-jelger-manet-
gateway-autoconf-v6-02, work in progress, apr. 2004.
[5] S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury and
B. Patil, "Proxy Mobile IPv6", RFC 5213, Aug. 2008.
[6] J. H. Lee, S. Ahn, Y. Kim, Y. Kim and S. Kim, "Scope-Extended
Router Advertisement for Connected MANETs", draft-jaehwoon-
autoconf-sera-00, Work in progress, July 2008.
[7] S. Thomson and T. Narten, "IPv6 Stateless Address A
utoconfiguration", RFC 2462, Dec. 1998.
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Author's Addresses
Jaehwoon Lee
Dongguk University
26, 3-ga Pil-dong, Chung-gu
Seoul 100-715, KOREA
Email: jaehwoon@dongguk.edu
Sanghyun Ahn
University of Seoul
90, Cheonnong-dong, Tongdaemun-gu
Seoul 130-743, KOREA
Email: ahn@uos.ac.kr
Younghan Kim
Soongsil University
11F Hyungnam Engineering Bldg. 317, Sangdo-Dong,
Dongjak-Gu, Seoul 156-743 Korea
E-main: yhkim@dcn.ssu.ac.kr
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