Internet Engineering Task Force Fumio Teraoka
INTERNET DRAFT Sony CSL
Masahiro Ishiyama
Toshiba
Keisuke Uehara
Keio University
Mitsunobu Kunishi
Keio University
Hiroshi Esaki
University of Tokyo
8 December 2000
LIN6: Mobility Support in IPv6 based on End-to-End Communication Model
<draft-teraoka-mobility-lin6-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC 2026.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents, valid for a maximum of six months,
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as "work in progress."
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 describes the protocol specification of LIN6. LIN6
supports both macro and micro mobility in IPv6[RFC2460]. LIN6 has
several advantages in comparison with Mobile IPv6[MIPv6] as follows:
o LIN6 has no header overhead because it does not use any extension
headers of IPv6 while Mobile IPv6 uses the Destination Options
Header for the Home Address Option and the Routing Header.
o LIN6 is more fault tolerant than Mobile IPv6. In Mobile IPv6, the
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Home Agent cannot be replicated to the subnet other than the home
link of the mobile node. LIN6 introduces the Mapping Agent which
can be replicated anywhere in the Internet.
o LIN6 keeps end-to-end communication model, that is, LIN6 does not
use any packet intercepter/forwarder such as the Home Agent of
Mobile IPv6. There is no tunneling in LIN6.
1. Introduction
The following two functions must be provided to achieve transparent
mobility in the network layer such as IPv6.
o location independent paging: the correspondent node must be able
to send a packet by specifying the immutable address of the mobile
node regardless of the location of the mobile node.
o TCP connection continuity: TCP connections established between the
correspondent node and the mobile node must be preserved even if
the mobile node moves to another subnet.
In IETF, Mobile IPv6[ID-MIPv6] is being standardized to support
transparent mobility in IPv6. However, Mobile IPv6 has several
problems. First, since Mobile IPv6 makes use of extension headers of
IPv6, it has large header overhead. For example, the header overhead
becomes 48 bytes in size when two mobile nodes communicate with each
other. Second, the location of the Home Agent is restricted by the home
address of the mobile node, that is, the Home Agent must be put on the
home network of the mobile node. This restriction makes it difficult to
replicate the home agent on other subnets for fault tolerance. In
addition, the correspondent node cannot communicate with the mobile node
if the home agent is connected beyond the firewall. Third, Mobile IPv6
requires Security Association of IPsec[RFC2401] between the
correspondent node and the mobile node for optimal routing. It is very
difficult to Establish Security association between two nodes of any
combination. LIN6 does not require Security Association between the
mobile node and the correspondent node for optimal routing.
We propose LINA (Location Independent Network Architecture) to support
transparent mobility in the network layer by redesigning network
architecture such as address structure. LIN6 is an application of LINA
to IPv6. LIN6 has no header overhead because it uses no extension
headers. The Mapping Agent (see Section XX) can be put anywhere in the
Internet regardless of the address of the mobile node. This improves
fault tolerance. In a firewall environment, communication with the
mobile node is available if the correspondent node and the mobile node
are connected to the same region divided by the firewall.
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2. Terminology
This document uses the following terms.
node:
The node is the general term to specify the equipment that
understands IP in the Internet. The node includes hosts, mobile
terminals, routers, and so on.
LIN6 ID:
The LIN6 ID is assigned to the node and uniquely identifies the
node in the Internet. It is 64 bits in length.
LIN6 prefix:
The LIN6 prefix is a predefined constant value attached to the
head of the LIN6 ID to construct the LIN6 generalized ID.
LIN6 generalized ID:
The LIN6 generalized ID is the identifier of the node used in the
transport layer and the upper layers. It is 128 bits in length.
The higher 64 bits of the LIN6 generalized ID is the LIN6 prefix
and the lower 64 bits is the LIN6 ID. The LIN6 generalized ID is
assigned to the node, not to the network interface. Application
programs use the LIN6 generalized ID to indicate the target node.
TCP establishes the TCP connection between two LIN6 generalized
IDs. Note that the LIN6 generalized ID does not appear in the
IPv6 header on the link.
network prefix:
The network prefix indicates the subnet to which the node is
connected. It is attached to the head of the LIN6 ID to construct
the LIN6 address.
LIN6 address:
The LIN6 address is assigned to the network interface of the node.
The higher 64 bits of the LIN6 address is the network prefix and
the lower 64 bits is the LIN6 ID so that the LIN6 address
specifies the identifier of the node as well as the point of
attachment to the Internet of the node. Note that the LIN6
address appears in the IPv6 header on the link and is not passed
to the transport layer.
mapping:
The mapping is the relation between the LIN6 ID and the network
prefix.
Mapping Agent:
The Mapping Agent (MA) is the function that maintains the mapping
of the mobile node. Each mobile node is associated with one or
more Mapping Agents. The relation between the LIN6 ID of the
mobile node and the address of the Mapping Agent is registered
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with the DNS.
Mapping Cache:
The Mapping Cache is the cache for mapping in the node.
normal IPv6 address:
The aggregatable global unicast address.
3. Protocol Overview
3.1. Address
LIN6 uses two types of network addresses: the LIN6 generalized ID and
the LIN6 address. Figure 1 depicts their formats. The LIN6 generalized
ID is 128 bits in length and is used in the transport layer and the
upper layers. LIN6 generalized ID is the identifier of the node in the
transport layer and the upper layers and does not change even if the
node moves. The LIN6 address is also 128 bits in length and is used in
the network layer. The LIN6 address specifies both the location and the
identifier of the node. The network prefix part of the LIN6 address
changes when the node moves to anther subnet. The formats of the LIN6
generalized ID and the LIN6 address are the same as the format of IPv6
aggregatable global unicast address[RFC2374].
<-------- 64 bits --------> <-------- 64 bits ------->
LIN6 +---------------------------+--------------------------+
generalized | LIN6 prefix (constant) | LIN6-ID |
ID +---------------------------+--------------------------+
+---------------------------+--------------------------+
LIN6 address | network prefix | LIN6-ID |
+---------------------------+--------------------------+
aggregatable +--+------+---+------+------+--------------------------+
global unicast |FP|TLA ID|res|LNA ID|SLA ID| Interface ID |
address +--+------+---+------+------+--------------------------+
Figure 1: The LIN6 generalized ID and the LIN6 address
Both the LIN6 generalized ID and the LIN6 address consist of two fields:
the network prefix and the LIN6 ID. Both fields are 64 bits in length.
The LIN6 ID is the global unique identifier of the node. EUI-64[EUI64]
will be used as LIN6-ID. The network prefix of the LIN6 address
indicates the subnet to which the node is connected while that of the
LIN6 generalized ID is the constant value and is called the LIN6 prefix.
In other words, the LIN6 address indicates both the location and the
identifier of the node while the LIN6 generalized only identifies the
node. Thus, the LIN6 generalized ID is used in the transport layer and
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the upper layers to identify the node, and the LIN6 address is used in
the network layer to indicate both the location and the identifier of
the node. Note that the LIN6 ID and the LIN6 generalized ID are
assigned per node while the LIN6 address is assigned per network
interface. Also note that the normal IPv6 address, i.e., the
aggregatable global unicast address, is assigned to the network
interface of the node in addition to the LIN6 address.
3.2. Address Processing
Figure 2 shows the procedures of address creation. As mentioned above,
the LIN6 generalized ID consists of the LIN6 prefix and the LIN6 ID. In
packet transmission, the transport layer specifies the LIN6 generalized
ID of the destination node to the network layer. The network layer
obtains the network prefix, i.e., the current location, of the
destination node by some means (see Section 3.3). The network layer
concatenates the obtained network prefix and the LIN6 ID contained in
the LIN6 generalized ID to create the LIN6 address of the destination
node.
In packet reception, the source address field of the packet contains the
LIN6 address of the source node. The network layer concatenates the
LIN6 prefix and the LIN6 ID contained in the LIN6 address of the source
node to create the LIN6 generalized ID, and then the network layer
notifies the transport layer of the packet reception with the LIN6
generalized ID of the source node. Thus, from the transport layer's
viewpoint, communication is done between the two LIN6 generalized IDs.
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<Transmission> <Reception>
+--------------+--------------+ +--------------+--------------+
| LIN6 prefix | LIN6 ID | | LIN6 prefix | LIN6 ID |
+--------------+--------------+ +--------------+--------------+
transport | LIN6 generalized ID ^
layer | |
----------------|---------------------------------|----------------
network layer | |
v |
+--------------+--------------+ +--------------+--------------+
| LIN6 prefix | LIN6 ID | | LIN6 prefix | LIN6 ID |
+--------------+--------------+ +--------------+--------------+
| ^
+------------+ | |
| mapping | | +------>+<------+
v | v | |
+--------------+ +--------------+ +--------------+ +--------------+
|network prefix| | LIN6 ID | | LIN6 prefix | | LIN6 ID |
+--------------+ +--------------+ +--------------+ +--------------+
| | ^
+------>+<-------+ |
| |
v |
+--------------+--------------+ +--------------+--------------+
|network prefix| LIN6 ID | |network prefix| LIN6 ID |
+--------------+--------------+ +--------------+--------------+
| LIN6 address ^
| |
----------------|----------------------------------|----------------
data link v |
layer
Figure 2: Address processing
3.3. Mapping Agent
The relation between the LIN6 ID and the network prefix is called
mapping. LIN6 introduces the Mapping Agent (MA) to maintain the mapping
of the mobile node. The Mapping Agent maintains the mapping of the
mobile node and replies to queries about mapping. Each mobile node is
associated with one or more Mapping Agents. When the network prefix of
the mobile node changes, i.e., when the mobile node moves, the mobile
node registers the new network prefix with one of the Mapping Agents
that maintain the mapping of the mobile node. Consistency among the
databases on the Mapping Agents must be kept by some procedures. These
procedures are beyond of the scope of this document.
It can be assumed that the relation between the mobile node and its
Mapping Agent is almost static in contrast to the mapping of the mobile
node. LIN6 makes use of the Domain Name System (DNS) to maintain the
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relation between the mobile node and its Mapping Agents. A new DNS
record MA is introduced to register the address of the Mapping Agent of
the mobile node with the DNS database.
3.4. Communication Procedure
The LIN6 Communication procedure is shown in Figure 3. Assume that the
correspondent node (CN) wants to send a packet to the mobile node (MN)
and that the CN knows the domain name of the MN. For simplicity, the MN
is associated with only a single Mapping Agent (MA). The communication
procedure is as follows:
1. When the MN moves to a subnet and obtains a new network prefix, it
registers the new mapping with the MA.
2. The CN sends a query packet to the name server (NS) to obtain the
address of the MA of the MN by indicating the domain name of the
MN.
3. The NS returns the address of the MA.
4. The CN sends a query packet to the MA to obtain the network prefix
of the MN by indicating the LIN6 ID of the MN.
5. The MA returns the network prefix of the MN, and then the CN
caches the obtained network prefix of the MN.
6. The CN sends a packet to the MN.
7. The MN sends a packet to the CN.
NS: Name Server +----+ 1
MA: Mapping Agent | MA | <------------------+
CN: Correspondent node +----+ |
MN: Mobile Node ^ | |
4| |5 |
2 | v 6 |
+----+ <-------------- +----+ --------------> +----+
| NS | | CN | | MN |
+----+ --------------> +----+ <-------------- +----+
3 7
Figure 3: Communication procedures
4. Packet Formats
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4.1. Data Packet
LIN6 uses the normal IPv6 header in which the LIN6 addresses are used in
the source address field and the destination address field. Figure 4
shows the format of the normal IPv6 header.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|version| Traffic Class | Flow Label |
+-------+---------------+-------+---------------+---------------+
| Payload Length | Next Header | Hop Limit |
+-------------------------------+---------------+---------------+
| |
+ +
| Source Address |
+ (LIN6 Address) +
| |
+ +
| |
+---------------------------------------------------------------+
| |
+ +
| Destination Address |
+ (LIN6 Address) +
| |
+ +
| |
+---------------------------------------------------------------+
Figure 4: IPv6 (LIN6) header format
4.2. Mapping Update and Reply Messages
When a mobile node moves to another subnet, i.e., when the network
prefix of the mobile node changes, the mobile node sends the Mapping
Update Message to the Mapping Agent and the correspondent nodes. Upon
receiving the Mapping Update Message, the Mapping Agent or the
correspondent node returns the Mapping Reply Message to the mobile node.
The Mapping Update and Reply Messages are UDP packets. The
Authentication Header of IPv6 must be included in the Mapping Update
Message to avoid illegal mapping update. Figure 5 shows the formats of
the Mapping Update and Reply Messages.
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0 0 1 3
0 8 6 1
+-->+--------+--------+-----------------+
| | Type | code | Flags |
| +--------+--------+-----------------+
| | Sequence Number |
| +-----------------------------------+
| | |
| + Network Prefix +
| | |
+----------------------+ | +-----------------------------------+
| IPv6 Base Header | | | |
+----------------------+ | + LIN6 ID +
|Authentication Header | | | |
+----------------------+ | +-----------------------------------+
| UDP Header | | | Timestamp |
+----------------------+--+ +-----------------------------------+
|Mapping Update Request| | Lifetime |
+----------------------+----->+-----------------------------------+
(a) Mapping Update
Request Message
+----------------------+
| IPv6 Base Header |
+----------------------+ 0 0 1 3
|Authentication Header | 0 8 6 1
+----------------------+ +-->+--------+--------+-----------------+
| UDP Header | | | Type | Code | Flags |
+----------------------+--+ +--------+--------+-----------------+
| Mapping Update Reply | | Sequence Number |
+----------------------+----->+-----------------------------------+
(b) Mapping Update
Reply Message
Fig. 5 Mapping Update Request/Reply formats
Source Address: the LIN6 address of the source node.
Destination Address: the LIN6 address of the destination node.
Source Port: TBD.
Destination Port: TBD.
Type:
0x01: update request
0x02: update reply
Code:
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0x00: succeeded
0x01: authentication failed
0x02: ...
Flags: TBD
Sequence Number:
the source node of the Mapping Update Request Message assigns this
field a sequence number. This value is copied to this field of
the Mapping Update Reply Message.
LIN6 ID: the LIN6 ID of the source node.
Network Prefix: the current network prefix of the source node.
Timestamp: the current time.
Lifetime: the period of time in which this mapping is valid.
4.3. MA Query and Reply Messages
When a node wants to send a packet to a mobile node, the node sends the
MA Query Message to the Mapping Agent to obtain the current network
prefix of the mobile node. When the Mapping Agent receives the MA Query
Message, it returns the MA Reply Message to the node to notify the
network prefix of the mobile node. Figure 6 shows the format of the MA
Query and Reply Messages.
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0 0 1 3
0 8 6 1
+-->+--------+--------+-----------------+
| | Type | Code | Flags |
| +--------+--------+-----------------+
| | Sequence Number |
| +-----------------------------------+
| | |
| + Network Prefix +
| | |
| +-----------------------------------+
| | |
+----------------+ | + LIN6 ID +
|IPv6 Base Header| | | |
+----------------+ | +-----------------------------------+
| UDP Header | | | Timestamp |
+----------------+--+ +-----------------------------------+
| MA Query/Reply | | Lifetime |
+----------------+----->+-----------------------------------+
Fig.6 MA Query/Reply Message format
Source Address: the LIN6 address of the source node.
Destination Address: the LIN6 address of the destination node.
Source Port: TBD.
Destination Port: TBD.
Type:
0x01: query
0x02: reply
Code:
0x00: succeeded
0x01: no mapping exists
0x02: ...
Flags: TBD.
Sequence Number:
the source node of the MA Query Message assigns this field a
sequence number. This value is copied to this field of the MA
Reply Message.
LIN6 ID: the LIN6 ID of the target node.
Network Prefix: the current network prefix of the target node.
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Timestamp: the timestamp of this mapping.
Lifetime: the period of time in which this mapping is valid.
5. Processing on the Mobile Node
5.1. Bootstrap
When the mobile node is powered on, it obtains the network prefix of the
subnet to which it is connected by sending the Router Solicitation
Message[RFC2461] and receiving the Router Advertisement Message. Next,
the mobile node sends a DNS query packet to obtain the address of the
Mapping Agent that maintains the mapping of the mobile node. Next, the
mobile node establishes a security association of IPsecNext, the mobile
node sends the Mapping Update Request Message to the Mapping Agent to
register the current network prefix and receives the Mapping Update
Reply Message.
5.2. Processing on Movement
The mobile node detects the change of the point of attachment to the
Internet by some mechanisms, for example, 1) interrupt by hardware, 2)
upcall from the link layer, and 3) router advertisement message. When
the mobile node detects a location change, first, it sends the Router
Solicitation Message and receives the Router Advertisement Message to
obtain the network prefix of the subnet to which the mobile node is
connected. Next, the mobile node sends the Mapping Update Request
Message to the Mapping Agent and the correspondent nodes to notify the
current network prefix. The Mapping Update Request Message must include
the Authentication Header.
6. Processing on Mapping Agent
Upon receiving the Mapping Update Request Message from the mobile node,
first, the Mapping Agent makes it sure that the Authentication Header is
correct. If authentication fails, the Mapping Agent returns the Mapping
Update Reply Message with the error code Authentication Failed. If
authentication succeeds, the Mapping Agent updates the mapping of the
mobile node and returns the Mapping Update Reply Message to the mobile
node.
If the mobile node is associated with two or more Mapping Agents,
consistency among the databases on the Mapping Agents must be kept by
some procedures. These procedures are beyond of the scope of this
document.
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7. Packet Transmission and Reception
7.1. Packet Transmission
When the network layer receives a packet transmission request from the
transport layer, the network layer makes sure that the destination
address passed from the TCP/UDP is a LIN6 generalized ID or a normal
IPv6 address by checking the upper 64 bits of the destination address.
If the destination address is a normal IPv6 address, the network layer
executes the normal IPv6 transmission procedure. If the destination
address is a LIN6 generalized ID, the network layer executes the LIN6
procedure described below.
The network layer extracts the LIN6 ID from the LIN6 generalized ID and
searches the Mapping Cache for the network prefix by using the LIN6 ID
as the key. If the network prefix is found, the network layer
concatenates the network prefix and the LIN6 ID to create the LIN6
address of the destination node. After that, the network layer executes
the normal IPv6 transmission procedure.
If the network prefix of the destination node is not found in the
Mapping Cache, the node keeps the packet waiting for transmission, and
then sends the MA Query Message to the Mapping Agent to obtain the
network prefix. Upon receiving the MA Reply Message, the node creates
the LIN6 address of the destination node, and then executes the normal
IPv6 transmission procedure.
7.2. Packet Reception
When the network layer receives a packet from the link layer, first the
network layer makes sure that the source address of the IPv6 header is a
LIN address or a normal IPv6 address. Refer to the next subsection
about how to distinguish between the LIN6 address and the normal IPv6
address. If the source address is the normal IPv6 address, the network
layer executes the normal IPv6 reception procedure.
If the source address is the LIN6 address, the network layer removes the
network prefix part of the LIN6 address, and then attaches the LIN6
prefix to create the LIN6 generalized ID of the source node. After
that, the network layer executes the normal IPv6 reception procedure.
7.3. Distinction between the LIN6 Address and the Normal IPv6 Address
From the address format viewpoint, the LIN6 address is indistinguishable
from the normal IPv6 address. To distinguish the LIN6 address, Sony CSL
obtained the OUI value 0x00-01-4A of EUI-64[EUI64]. Thus, if the upper
24 bits of the lower 64 bits of the IPv6 address is 0x00-01-4A, the IPv6
address is the LIN6 address.
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8. Intellectual Property Right
This proposal includes patented mechanisms.
Author's Address
o Fumio Teraoka
Sony Computer Science Laboratories, Inc.
3-14-13 Higashigotanda, Shinagawa-ku, Tokyo 141-0022, Japan.
Phone: +81-3-5448-4380
Email: tera@SonyCSL.co.jp
o Masahiro Ishiyama
R&D Center, Toshiba.
1 Komukai Toshiba-Cho, Saiwai-Ku, Kawasaki, Kanagawa 212-8582, Japan.
Phone: +81-44-549-2238
Email: masahiro@isl.rdc.toshiba.co.jp
o Keisuke Uehara
Keio University.
5322 Endo, Fujisawa, Kanagawa 252-8520, Japan.
Phone: +81-466-49-1394
Email: kei@wide.ad.jp
o Mitsunobu Kunishi
Keio University
3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-0061, Japan.
Phone:
Email: kunishi@tokoro-lab.org
o Hiroshi Esaki
University of Tokyo
2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8658, Japan.
Phone: +81-3-5684-7303
Email: hiroshi@wide.ad.jp
References
[RFC2460] S. Deering and R. Hinden. Internet Protocol, Version 6 (IPv6)
Specification. RFC 2460, Dec. 1998.
[MIPv6] C. Perkins. Mobility Support in IPv6. Internet Draft draft-
ietf-mobileip-ipv6-13.txt, Nov. 2000.
[RFC2401] S. Kent and R. Atkinson. Security Architecture for the Internet
Protocol. RFC 2401, Nov. 1998.
[RFC2374] R. Hinden, M. O'Dell, and S. Deering. An IPv6 Aggregatable
Global Unicast Address Format. RFC 2374, Jul, 1998
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[EUI64] IEEE. Guidelines for 64-bit Global Identifier (EUI-64)
Registration Authority,
http://standards.ieee.org/regauth/oui/tutorials/EUI64.html, 1997.
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