IETF MANET Working Group Shubhranshu. Singh
Internet-Draft JH. Kim
Expires: December 10, 2004 YG. Choi
KL. kang
YS. Roh
SAMSUNG AIT
June 11, 2004
Mobile multi-gateway support for IPv6 mobile ad hoc networks
draft-singh-manet-mmg-00.txt
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Abstract
MANET (Mobile Ad-hoc NETwork) allows users to form a private wireless
network, without existing centralized administrator that support
multi-hop communication and low network establishment cost. Recently
some interesting work has been published to allow manet node access
to the Internet via internet gateway which is placed on the border of
manet and the Internet. The Internet gateway has an important role
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to support global connectivity. This document introduces the
management of internet gateway, routing policy and load balancing for
the scenario where multiple mobile gateways exist for an ad hoc
network.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Protocol operation . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Gateway selection . . . . . . . . . . . . . . . . . . . . 7
4.2 Routing policy . . . . . . . . . . . . . . . . . . . . . . 8
4.3 Load balancing . . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . 13
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1. Introduction
There are several routing protocols developed for ad hoc networks.
They typically provide solution for route discovery and maintenance
for the nodes within the manet. Nodes often need global connectivity
to communicate with the Internet. Wakikawa[1] provides a method for
manet node to acquire a global prefix from the gateway as well as how
this node can communicate with the Internet.
Use of fixed internet gateway is not suitable for ad hoc network
whose basic concept is infrastructureless and anywhere network formed
by nodes having random mobility. Hence in this draft we allow mobile
ad hoc node to act as internet gateway thus removing any service
range limitation and making very flexible as against when fixed
internet gateway is used. Also, it removes any concern about the use
of proactive or reactive routing protocols.
There are some signal exchanges between the internet gateway and
manet node for locating the gateway. In addition,The traffic between
manet node and the Internet must travel through the same internet
gateway in case of single gateway scenario.Simultaneous use of
internet gateway by several manet nodes results in heavy traffic
congestion around the gateway node. Thus there is a need to offload
the gateway. Also, Use of single gateway has the drawback of single
point of failure. All these problems can be solved by using multiple
gateways for a particular manet. The multiple internet gateway
scenario is easily made with mobile node internet gateway.
This document specifies the method for multiple gateway selection and
routing policy that can be used to forward packets between the
Internet and ad hoc network. Figure 1 shows the multiple gateways
scenario.
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------------
| INTERNET |
------------
|
|
|
|
----------
| Access |
----------- | Router | -------------
| ---------- |
| : |
| : |
| : |
------------ : ------------
| Internet| : | Internet|
| Gateway 1| ....... | Gateway n|
------------ ------------
| |
| |
| |
-----------------------------------------------------
| |
| MANET |
| |
-----------------------------------------------------
Fig. 1 MANET topology with multi-gateway
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL", and
"silently ignore" in this document are to be interpreted as described
in RFC 2119 [1].
The following terminology and abbreviations are used in this
document.
Mobile Internet gateway
- Mobile device located at the edge of the manet and provides
Internet connectivity to the manet nodes. They are part of
manet as well as the Internet.
Default Internet gateway
- The Internet gateway that uses the default route for traffic
forwarding between manet and the Internet. It need not use
tunneling or routing header to route packets between the
Internet and manet.
Candidate Internet gateway
- Internet gateways other than the default gateway are referred
to as candidate gateways.
Proxy routing header
- The routing header that candidate internet gateway may use for
forwarding manet node packets to the Internet.
Internet node
- A node located on the Internet.
Manet node
- A node located inside the manet.
Global address
- A nodeí¯s IPv6 address which is used for communication with the
Internet node.
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3. Limitations
For convenience and simplicity we assume in this draft that all manet
nodes within a particular ad hoc network use the same global IPv6
prefix. How manet nodes acquire the same IPv6 prefix from the access
router is out of scope of this document.
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4. Protocol operation
This section describes our protocol operation in detail.
4.1 Gateway selection
Any manet node that is one hop away from the Access Router, AR can
configure itself as gateway. Such nodes can receive router
advertisement messages periodically broadcasted by access router. At
any point of time there can be one default gateway and one or more
candidate gateways. In the absence of any default gateway, the node
configuring as a gateway should operate as default gateway. If the
default gateway is already present in the manet then the node should
configure itself as candidate gateway.
Only the default gateway periodically sends modified router
advertisement message. Default gateway also sends modified router
advertisement message in response to modified router solicitation
message. Modified router solicitation message format is shown in
figure2 and modified router advertisement message format is shown in
figure 3. Modified router solicitation and advertisement packet
formats are same as defined in [5] except the use of M and N bits
respectively (these formats are exactly same as used in [1]).
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
Fig. 2 Modified RS
Manet router solicitation flag (M)
A 1-bit manet router solicitation flag.
When set it indicates that the router solicitation
message can be sent over a multi-hop network.
The internet gateway must not forward this message
to the internet node.
Reserved
Reduced from a 32-bit field to 31-bit field to account
for the addition of manet router solicitation (M) flag.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O|N| Reserved | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
Fig. 3 Modified RA
Manet router advertisement flag (N)
1-bit manet router advertisement flag.
When set indicates that this message is only for manet
nodes and can be sent over multiple hop manet nodes.
Internet gateways must not forward this message to the
Internet node.
A node may learn about the presence or absence of another gateway in
the manet if:
- It does not receive any RA message from the gateway with N flag
set. The waiting time for RA should be at least the time
indicated by the í«new advertisement interval optioní¯. This router
advertisement interval option indicates the interval at which the
default gateway advertises unsolicited router advertisement [6].
- It sends gateway solicitation message or tests for neighbor
reachability, as explained in [5] and fails.
In the absence of any received RA message, a candidate gateway should
wait for random interval of time before configuring itself as default
gateway. This will prevent more than one gateway to configure itself
as default gateway at the same time. While operating as internet
gateway, the node should send gateway discovery reply messages.
4.2 Routing policy
Default gateway and candidate gateway routes packets between the
Internet and manet based on its own routing policy. In this document
we introduce proxy routing header and tunneling mechanism. Proxy
routing header and tunneling mechanism are used by candidate internet
gateways as they can not use the longest prefix matching routing.
We assume that the default gateway as well as the candidate gateways
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uses the same global IPv6 prefix. How to receive same prefix from
the access router is out of scope of this document. Use of multiple
prefixes results in serious flooding problem mainly due to periodic
RA message advertisement by each gateway with different prefix.
Also, if multiple prefixes are used then IPv6 manet node may attempt
to send frequent binding update message because each time it receives
router advertisement message with different prefix it assumes that it
has joined another network even though it has only changed its
location within the same manet.
Default gateway can route traffic originating from manet node and
whose destination is internet node using default route while the
candidate gateways should route such traffic either using proxy
routing header or tunneling mechanism. In proxy routing header
destination address of IPv6 header is set to the Internet access
router address while final destination address set to internet node
address and original source address set to routing header. Proxy
routing header indicates to internet node that the packet travel via
candidate internet gateway and access router. In response to this
received packet, internet node must use candidate internet gateway
and original source address in the routing header.
If manet node uses tunneling mechanism, candidate internet gateways
encapsulate packets to the internet node. Tunneling header has
source address as candidate internet gateway and destination address
as internet node. The internet node decapsulates the packet and
replies with tunneling header with source address as internet nodeí¯s
address and destination address as candidate internet gatewayí¯s
address.
4.3 Load balancing
For better traffic load sharing among each other, internet gateways
may use the traffic information option shown in figure 4. This
option is carried by the router advertisement message sent by
internet gateway. Traffic information field indicates the number of
active routes originating from a particular gateway.
These active routes include routes using proxy routing header,
tunneling as well as default routes. On receipt of solicited or
unsolicited router advertisement message carrying this option, manet
node learns about the traffic characteristics of the gateway and
accordingly decides to use it or opt for another gateway for
forwarding traffic to the internet node.
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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 | traffic information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig. 4 Traffic information option
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5. Security Considerations
This document does not specify any specific security measure. We
need more consideration for the secure tunneling and use of routing
header. These mechanisms should consider all the security measures
as taken by IPv6 networks as well as manet specific environment. We
couldní¯t mention about secure intra manet communication as at present
there in no extended security consideration for the manet.
6. References
[1] Ryuji Wakikawa et. el. Global connectivity for IPv6 Mobile
Ad Hoc Networks, IETF ídraft-wakikawa-manet-globalv6-03.txtí
[2] Pekka Pekken et. el. IPv6 addressing in a heterogeneous
MANET-network, IETFídraft-paakkonen-addressing-htr-manet-00.txtí
[3] C. Perkins et. el. IETF RFC: 3561,
íAd hoc On Demand Distance Vector (AODV) Routingí
[4] Kilian Weniger , Martina Zitterbart, Institute of Telematics,
University of Karlsruhe, Germany: íIPv6 Autoconfiguration in
Large Scale Mobile Ad-Hoc Networksí
[5] IETF RFC 2461, í Neighbor Discovery for IP version 6 (IPv6)í
[6] IETF draft, ídraft-ietf-mobileip-ipv6-24.txt í:
íMobility Support in IPv6í
[7] C. Perkins, E. Royer and S. Das. Ad hoc on demand distance
vector routing for IP version 6 (work in progress).
[8] S. Deering and R. Hinden. Internet protocol, version 6 (ipv6)
specification. Request for comments (proposed standard) 1883,
Internet engineering task force, December 1995
[9] A. Conta and S. Deering. Internet control message protocol
(ICMPv6) for the Internet protocol version 6 (ipv6) specification.
Request for comment (draft standard) 2463.
Internet Engineering task force, December 1998
Authors' Addresses
Shubhranshu Singh
SAMSUNG Advanced Institute of Technology
i-Networking Laboratory
San 14-1, Nongseo-ri, Giheung-eup
Yongin-si, Gyeonggi-do 449-712
KOREA
Phone: +82 31 280 9569
EMail: shubhranshu@samsung.com
Jae-Hoon Kim
SAMSUNG Advanced Institute of Technology
i-Networking Laboratory
San 14-1, Nongseo-ri, Giheung-eup
Yongin-si, Gyeonggi-do 449-712
KOREA
Phone: +82 31 280 9532
EMail: jaehoonk@samsung.com
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YoungGon Choi
SAMSUNG Advanced Institute of Technology
i-Networking Laboratory
San 14-1, Nongseo-ri, Giheung-eup
Yongin-si, Gyeonggi-do 449-712
KOREA
Phone: +82 31 280 9531
EMail: ygchoi@samsung.com
Kyunglim Kang
SAMSUNG Advanced Institute of Technology
i-Networking Laboratory
San 14-1, Nongseo-ri, Giheung-eup
Yongin-si, Gyeonggi-do 449-712
KOREA
Phone: +82 31 280 9532
EMail: klkang@samsung.com
Yongsung Roh
SAMSUNG Advanced Institute of Technology
i-Networking Laboratory
San 14-1, Nongseo-ri, Giheung-eup
Yongin-si, Gyeonggi-do 449-712
KOREA
Phone: +82 31 280 9532
EMail: yongsung.roh@samsung.com
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