Internet Engineering Task Force W. T. Teo
INTERNET DRAFT National Univ. of Singapore
Y. Li
Bay Networks, Inc.
1 March 1998
Mobile IP extension for Private Internets Support (MVPN)
draft-teoyli-mobileip-mvpn-00.txt
Status of this Memo
This document is a submission to the Mobile-IP Working Group of the
Internet Engineering Task Force (IETF). Comments should be submitted
to the mobile-ip@smallworks.com mailing list.
Distribution of this memo is unlimited.
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Abstract
This memo describes a scheme to enable the mobile node to move from
public to private domains or between private domains while it still
maintains internet connectivity. This extended mobility support does
not require that the private host have access to the global Internet.
This memo takes advantage of the PAID agent, a domain border agent,
specified in the private address identification (PAID) procotol. To
register a mobility binding, we introduce a mobile extension in the
regional registration messages with the PAID agent, and a private
extension to the global registration messages with the home agent.
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1. Introduction
1.1 Problem
Mobile IP base protocol [6] provides an efficient, scalable mechanism
for node mobility within the public Internet. However, it does not
support movement between private domains and between private domain
and public domain.
Private internets are defined in [9]. They differ from the existing
public internet in terms of address allocation. Private internets are
generally used to number hosts within an enterprise, organization or
a community. These hosts are not meant to be accessed from public
internet hosts outside the private internets. The problem arises when
a private host providing services to other clients in the private
networks moves to another private or public site.
Besides, the uniqueness of private IP address for each host cannot
be assumed. Since routers generally deliver datagrams based on their
destination IP address, the mechanism provided by the Mobile IP will
not work at all between different private internet communities.
1.2 MVPN
The protocol (MVPN) specified in this memo attempts to extend the
Mobile IP support to private internets, that is, to enable mobility
between private domains and from public to private domains.
The private address identification protocol (PAID) [4] proposes an
approach which facilitates the private extension of the mobility
support. It proposes to bind each private address, by regional
registration, to a public address of another node (called PAID agent
or domain border agent) and thus provides an unique identification of
a private host. This protocol also invents a PAID Encapsulation
mechanism. This approach enables the global communication between
private domains.
Taking advantage of the PAID agent, the MVPN introduces a private
extension to the global Registration Request and Registration Reply
messages as specified in the Mobile IP base protocol [6]. These
messages will then be forwarded between the mobile node and the home
agent by way of a foreign PAID agent and/or a home PAID agent.
The idea of regional registration was introduced by Perkins [8]. It
was meant to reduce the frequency of distant registrations with the
home agent. We extend this idea to the private domains. When a mobile
node moves to a private domain, it has to first register its private
care-of address with the public PAID agent. To perform this regional
registration, MVPN introduces a mobile PAID extension to the PAID
registration messages as specified in the PAID protocol [4].
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1.3. Applicability
MVPN is intended to enable nodes to move from a public domain to a
private domain, or to move between private domains. MVPN does not
support movement from a private domain to a public one.
With the support of MVPN, both the mobile node and the home agent can
be public or private nodes. The foreign agent can be a public node
only if the mobile node is in the same domain as the foreign agent or
both the mobile node and the home agent are public nodes. In a
private domain, MVPN does not require the foreign agent for
registration, but the mobile node still uses the Agent Advertisement
messages from the foreign agent to detect movement, from one subnet
to another or from a domain to another.
Although the corresponding node may not be able to access the private
domain which the mobile node is visiting, as long as it is able to
communicate with the mobile node's home network, the corresponding
node will be able to communicate with the mobile node with help of
the home agent, the home PAID agent, and the foreign PAID agent.
MVPN is compatible with the PAID protocol [4]. When the Internet
supports PAID partly or completely, the MVPN will even enable the
mobile node to move from a private domain to a public one.
1.4. Terminology and Definitions
Identification of Private Address (PAID)
The identification of a private address is a <public, private>
address pair. It is defined in [4]. We also call it as the binary
identification of the private address.
PAID Agent
A PAID agent is a node that provides private nodes with the public
portion of the binary identification. It is defined in [4].
Home PAID Agent
This is a PAID agent of the mobile node's home agent when the home
agent is private. It supports MVPN in the mobile node's home
domain. It does not process Registrtion Request and Registration
Reply messages but it forwards these messages. The home PAID agent
tunnels packets, including the registration messages, between the
home agent and the foreign PAID agent or the foreign agent.
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Foreign PAID Agent
This is a PAID agent of the mobile node's care-of address. It
supports MVPN in the mobile node's foreign domain. It processes
Registrtion Request and Registration Reply messages. It tunnels
packets between the home agent/the home PAID agent and the foreign
agent/the mobile node.
Mobile Node
The mobile node in MVPN is the same as that defined as in the
Mobile IP base protocol, except that the mobile node address can
be a public address, private address, or a <public, private>
address pair.
Home Agent
The home agent in MVPN is the same as that defined as in the
Mobile IP base protocol. Home agent address can be private or
public.
Foreign Agent
The foreign agent in MVPN is the same as that defined as in the
Mobile IP base protocol. Foreign agent address can be private or
public.
In MVPN, the foreign agent is less important since the mobile node
can obtain co-located care-of address by DHCP [1].
Care-of Address
The care-of address in MVPN is the same as that defined as in the
Mobile IP base protocol. It can be private or public. We refer as
private care-of address to the care-of address of the mobile node
when the care-of address is private.
Public Care-of Address
The public care-of address of the mobile node is referred to a
public address of the foreign PAID agent.
Mobility Binding
Similar to that in the Mobile IP base protocol, the mobility
binding in MVPN is the association of the binary identification
of the mobile node home address, the binary identification of the
care-of address, along with the lifetime of the association.
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2. Protocol Overview
When a home agent in MVPN moves to another private domain, it will
identify the mobile node's location by the binary identification of
the mobile node's care-of address, that is, the address pair <foraign
PAID agent, care-of address>. On the other hand, the mobile node will
identify the home agent by the binary identification of the home
agent, that is, the address pair <home PAID agent, home agent
address>.
2.1 Obtaining Care-of Address
The mobile node, when moving to a private network in another domain,
may attempt to obtain a private co-located care-of address by using
DHCP [1]. Since there are plenty of private addresses in each
enterprise network, using co-located care-of addresses is not
expensive.
2.2 Discovery of Foreign PAID Agent
After obtaining a care-of address, the mobile node may attempt to
register a binary identification with a foreign PAID agent.
The mobile node may discover the foreign PAID agent by the PAID agent
discovery protocol in [4]. Alternatively, a foreign agent may include
a PAID agent extension in the Agent Advertisement message, and thus
the mobile node is able to learn the PAID agent from the foreign
agent.
2.3 Regional Registration
The mobile node may register a binary identification with a foraign
PAID agent through exchange of a pair of PAID Registration Request
and Reply messages as specified in the PAID registration protocol
(see [4]).
To additionally regionally register a mobility binding with the
foreign PAID agent, the mobile node should include a Mobile PAID
Extension in the PAID Registration Request message. The foreign PAID
agent should associates the mobility binding regionally with itself
and include the Mobile PAID Extension in the reply.
This way the mobile node may not necessarily originate a home
registration as in section 2.4 unless it moves to another domain.
This is because the mobile node can be served by the same foreign
PAID agent while moving inside the domain.
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2.4 Home Registration
Using the binary identification of its care-of address, the mobile
node may register a mobility binding with its home agent, by
exchange of a pair of Registration Request and Reply messages, via
the foreign PAID agent and the home PAID agent. To register such a
mobility binding, both the request and the reply should contain a
Private Extension.
The private extension contains private mobile node address, and/or
private home agent address, and/or private care-of address. The
foreign agent, foreign PAID agent, or home agent will determine if
the Registration Request and reply messages supports MVPN by checking
the presence of the private extension.
2.5 Transit Registration
The mobile node may register a mobility binding with other foreign
PAID agents in domains it visited previously. These foreign PAID
agents will then redirect mobile traffic to the location where the
mobile node is currently visiting. Transit registration can be
performed in the same way as the home registration.
2.6 Movement Detection
The mobile node will take advantage of Agent Advertisement messages
to detect movement. In order to detect the movement from one domain
to another, both the home agent and foreign agent should advertise
all PAID agents in the domain as well as care-of addresses.
A mobile node should detect a change in location when it receives an
Agent Advertisement with a different set of care-of address. In
contrast, when the mobile node learns the message has a different set
of PAID agent addresses, it should be considered to have moved into
another domain.
2.7 Datagram Forwarding / Tunnelling
In general, IP Encapsulation within IP [7] or GRE [3] can be employed
for tunneling from the home agent to the mobile node. In the MVPN
case, it is difficult for a PAID agent to identify where the mobile
traffic is destined.
If the mobile node has register a binding with 'P' bit set, it means
all agents support PAID encapsulation [4]. In this case, the home
agent may tunnel packets to the private care-of address with PAID
encapsulation. If the mobile node is not able to register a binding
with the 'P' bit set, the PAID encapsulation should apply to the
tunnels between the mobile node and the foreign PAID agent or between
the home PAID agent and the home agent. Other tunnels may employ the
a regular tunneling mechanism other than the PAID encapsulation.
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A private mobile node should use reverse tunnel [5] when originating
packets to its home domain. This is because private hosts currently
do not support PAID and packets are not deliverable between two
private domains. If the PAID can be supported between the foreign
domain and the destination domain, the mobile node should build two
levels of PAID forwarding headers for packets origination.
2.8 Interoperability with Mobile IP Base Protocol
Interoperability with the Mobile IP base protocol is unidirectional.
When the mobile node moves from a public domain to a private domain,
if the mobile node and the private domain supports MVPN while the
public domain supports the base protocol, the mobile node will be
able to register a mobility binding with the home agent successfully.
In this case, to register a mobility binding, the mobile node should
send a Registration Request to the home agent via the foreign PAID
agent. This request should include a private extension which contains
only the private care-of address. Since the Registration Reply does
not include the care-of address field, the home agent does not
neccesarily include a private extension in the reply to the mobile
node.
Supporting movement from a private domain to a public domain is
difficult and unnecessary. It is difficult for a foreign agent to
identify a private mobile node since there may be two mobile nodes
that have the same private address. On the other hand, the Mobile IP
base protocol currently supports movement between public networks or
between networks in the same routing domain. Since more and more
enterprise networks have been configured with private addresses, only
movement to the private domain is realistic.
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3. Formats of Messages and Extensions
3.1 Registration Request Message
There is only one new bit 'P' in the Registration Request:
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 |S|B|D|M|G|V|T|P| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Public Home Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Public Home Agent Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Public Care-of Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ Identification +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
T If the 'T' bit is set, the mobile node asks its home
agent to accept a reverse tunnel from the care-of
address. Mobile nodes using a foreign agent care-of
address ask the foreign agent to reverse-tunnel its
packets.
P If the 'P' bit is set, the mobile node asks its home
agent to perform PAID encapsulation for packets destined
to the mobile node.
Public Home Address
The mobile node's home address if the mobile node is
public or otherwise the home PAID agent address.
Public Home Agent Address
The home agent address if the home agent is public
or otherwise the home PAID agent address.
Public Care-of Address
The care-of address if there is no foreign PAID agent
or otherwise the foriegn PAID agent address.
3.2 Registration Reply Message
MVPN does not introduce any new field in the Registration Reply
message except that it renames the home address field and the home
agent field as follows.
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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 | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Public Home Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Public Home Agent Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Identification +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extensions ...
+-+-+-+-+-+-+-+-
Public Home Address
The mobile node's home address if the mobile node is
public or otherwise the home PAID agent address.
Public Home Agent Address
The home agent address if the home agent is public
or otherwise the home PAID agent address.
3.3 PAID Agent Extension
This extension is included in the Agent Advertisement message. The
mobile node can use it to detect movement and find a foreign PAID
agent. The presence of this extension signifies the agent supports
MVPN.
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 | No. of Agents |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PAID Agent Addresses |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |B|H|F| Rsvd | Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 48
Reserved 0
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No. of Agents
The number of agents in this extension.
PAID Agent Addresses
A PAID agent address. It MUST be public.
Lifetime The longest lifetime (measured in seconds) that this
agent is willing to accept in any PAID Request.
A value of 0xffff indicates infinity.
B Busy. The PAID agent will not accept request from
additional private nodes.
H Home PAID agent. This agent offers service as a home
PAID agent.
F Foreign PAID agent. This agent offers service as a
foreign PAID agent.
Preference
This is for load balancing or other purposes.
0 means no service can be provided.
infinity 0xff means unlimited services.
3.4 Private Extension
This extension is included in Registration Request and Registration
Reply messages. This is to extend the mobile IP to private internets.
The presence of this extension signifies the mobile node supports
MVPN.
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 |M|H|F| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (If present) Private Home Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (If present) Private Home Agent Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (If present) Private Care-of Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M bit
If set, the private home address is present.
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H bit
If set, the private home agent address is present.
F bit
If set, the private care-of address is present.
In Registration Reply message, this bit SHOULD be set to 0
since the care-of address is not required.
3.5 Mobile PAID Extension
This extension is included in the PAID Registration Request and PAID
Registration Reply [4] messages. This is for the mobile node to
regionally register a mobility binding with a foreign PAID agent.
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 |P| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Public Home Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (If present) Private Home Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
P bit
If set, the private home address is present.
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4. Mobile Node Consideration
The mobile node supporting MVPN MUST always include the private
extension in the Registration Request messages.
4.1 Private Mobile Node
The discussion of movement from a private domain to a public domain
is beyond the scope of this document. Therefore, it is assumed that
the private mobile node moves to another private domain.
4.1.1 Regional Registration
When the private mobile node performs the regional registration, it
MUST include a mobile PAID extension in the PAID Registration Request
message. This extension MUST contain the private mobile home address.
When the mobile node receives a PAID Registration Reply, it SHOULD
verify the presence of the mobile PAID extension. This extension
SHOULD contain the private home address.
4.1.2 Home Registration
When the private mobile node performs the home registration, it MUST
include the private extension in the Registration Request and this
extension MUST contain the private home address, the private home
agent address, and the private care-of address.
When the mobile node receives a Registration Reply, it MUST verify
the presence of the private extension. The private extension MUST
contain the private home address and the private home agent address.
4.1.3 Datagram Originating and Receiving
The mobile node MUST employ the PAID encapsulation when it originates
packets to a corresponding node that is in a domain other than its
visiting domain. In this case, it SHOULD use reverse tunneling
method.
When receiving a packet tunneled by the foreign PAID agent, the
mobile node SHOULD decapsulate the packet using the relevant
encapsulation protocol as indicated in the packet.
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4.2 Public Mobile Node
The Mobile IP base protocol supports the scenary that a public mobile
node moves to another public domain. In this case, a foreign PAID
agent can also be deployed in this foreign domain so that the mobile
node just keeps registering with this PAID agent regionally instead
of frequently performing home registration. For the convenience of
description as below, even if the care-of address is public, we still
call the care-of address as "private care-of address".
4.2.1 Regional Registration
When the public mobile node performs the regional registration, it
MAY include a mobile PAID extension in the PAID Registration Request.
This extension only contains the public mobile home address.
When the mobile node receives a PAID Registration Reply, it SHOULD
verify the presence of the mobile PAID extension. This extension
SHOULD contain the public home address.
4.2.2 Home Registration
When the public mobile node performs the home registration, it
SHOULD include the private extension in the Registration Request.
The extension SHOULD contain the private care-of address.
When the mobile node receives a Registration Reply, it SHOULD not
verify the presence of the private extension since the home agent
probably does not support MVPN.
4.2.3 Datagram Originating and Receiving
The mobile node MAY apply the PAID encapsulation when it originates
packets to a corresponding node that is in a domain other than its
visiting domain. In this case, it SHOULD use reverse tunneling
method. If the visiting domain is public, the mobile node MAY use
other encapsulation protocols to originate packets.
When receiving a packet tunneled by the foreign PAID agent, the
mobile node SHOULD decapsulate the packet using the relevant
encapsulation protocol as indicated in the packet.
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5. Foreign Agent Consideration
The foreign agent MAY include the PAID agent extension in the Agent
Advertisement messages. This is to allow the mobile node to detect
the movement between different domains. The mobile node MAY also
learn from the PAID agent extension and initiate the regional
registration with a PAID agent.
In MVPN, the registration messages MAY bypass the foreign agent since
the mobile node MAY obtain co-located care-of address.
6. Foreign PAID Agent Consideration
6.1 Regional Registration
When the foreign PAID agent receives a PAID Registration Request
message with the mobile PAID extension included, if it can honour the
request, it SHOULD associate the binary identification of the mobile
node with the binary identification of the care-of address. It SHOULD
return a PAID Registration Reply message with the mobile PAID
extension.
6.2 Home Registration
6.2.1 Receiving Registration Request
When the foreign PAID agent receives a Registration Request message,
it SHOULD verify the reply is valid. The foreign PAID agent MUST
already have a regional mobility binding for the mobile node, and the
private extension MUST be present.
If the request is invalid, the PAID agent SHOULD deny the request and
respond with a Registration Reply message that contains a proper
error code.
If the request is valid, the PAID agent SHOULD associate the mobility
binding of the mobile node with the home agent or the binary
identification of the home agent.
If the home agent is private, the foreign PAID agent SHOULD tunnel
the request to the home PAID agent using PAID encapsulation.
Otherwise, the foreign PAID agent SHOULD simply forward the message
to the home agent.
6.2.2 Receiving Registration Reply
When the foreign PAID agent receives a Registration Reply message,
it SHOULD verify the reply is valid. If the mobile node is private,
the private extension MUST be present, and the private home address
and private home agent address MUST be present in the private
extension.
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If the reply is invalid, the PAID agent SHOULD drop it and log a
message.
If the reply is valid, the PAID agent SHOULD activate the mobility
binding for subsequent datagram forwarding, and then forwards the
message to the mobile node.
6.3 Datagram Forwarding
When the foreign PAID agent receives a packet destined for the mobile
node, it MUST employ the PAID encapsulation to tunnel the packet to
the mobile node.
When the PAID agent receives a packet from the mobile node, it SHOULD
verify it is PAID encapsulated. If the P bit was not set in the
home registration for the mobility binding, the PAID agent MAY tunnel
the packet to the home agent using IP within IP encapsulation.
Otherwise, PAID encapsulation SHOULD be used.
7. Home PAID Agent Consideration
The home PAID agent SHOULD forward Registration messages, as
specified in PAID [4], between the home agent and the foreign PAID
agent. It does not have to save any mobility binding.
8. Home Agent Consideration
8.1 Home Registration
When the home agent receives a Registration Request message, it
SHOULD verify the reply is valid. If the mobile node is private, the
private extension MUST be present.
If the request is invalid, the home agent SHOULD deny the request and
respond with a Registration Reply message that contains a proper
error code.
If the request is valid, the home agent SHOULD associate the mobility
binding of the mobile node with itself. The home agent SHOULD send a
Registration Reply message, which SHOULD contain the original private
extension in the request.
If the home agent is private, it SHOULD tunnel the reply to the home
PAID agent using PAID encapsulation. Otherwise, the home agent SHOULD
simply forward the message to the foreign PAID agent or the foreign
agent.
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8.2 Data Forwarding
When the home agent receives a packet destined for the mobile node,
if it is private, it MUST employ the PAID encapsulation to tunnel the
packet to the home PAID agent. Otherwise, the home agent MAY tunnel
the packet to the foreign PAID agent or the foreign agent using
IP within IP encapsulation.
When the home agent receives a packet originated from the mobile
node, it SHOULD simply forward it to the corresponding node.
9. Security
The security issue is beyond the scope of this document.
10. Acknowledgements
Many thanks to Dr. Y. C. Tay at the National University of Singapore
for supporting this joint work as well as for his valuable comments.
An implementation of MVPN is done by Wee Tuck Teo, one of the
authors, at the National University of Singapore.
References:
[1] R. Droms. Dynamic Host Configuration Protocol. RFC 2131, March
1997.
[2] K. Egevang, and P. Francis. The IP Network Address Translator,
RFC 1631, May 1994.
[3] S. Hanks, T. Li, D. Farinacci, and P. Traina. Generic Routing
Encapsulation (GRE). RFC 1701, October 1994.
[4] Y. Li and W. T. Teo. IP Private Address Identification, Internet
Draft, January 1998.
[5] G. Montenegro. Reverse Tunneling for Mobile IP, Internet Draft,
March 1997.
[6] C. Perkins. IP Mobility Support Version 2, Internet Drafts,
November 1997.
[7] C. Perkins. IP Encapsulation within IP. RFC 2003, May 1996.
[8] C. Perkins. Mobile-IP Local Registration with Hierarchical
Foreign Agents. February 1996.
[9] Y. Rekhter and et. al. Address allocation for Private Internets,
RFC 1918, February 1996.
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Author's Address
Questions about this memo can also be directed to the author:
W. T. Teo
Department of ISCS
National University of Singapore
Lower Kent Ridge Crescent
SINGAPORE 119260
E-mail: teoweetu@iscs.nus.edu.sg
Y. Li
Bay Networks, Inc.
BL60-304
600 Technology Park Drive
Billerica, MA 01821
Phone: 1-978-916-1130
Fax: 1-978-670-8760
E-mail: yli@BayNetworks.COM
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