Mobile IP Working Group F. Adrangi, Ed.
Internet-Draft intel
Expires: August 10, 2004 H. Levkowetz, Ed.
ipUnplugged
February 10, 2004
Problem Statement: Mobile IPv4 Traversal of VPN Gateways
<draft-ietf-mip4-vpn-problem-statement-01.a.txt>
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Abstract
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Internet-Draft MIPv4 VPN Traversal Problem Statement February 2004
Deploying Mobile-IP v4 in networks which are connected to the
Internet through a VPN (Virtual Private Network) gateway presents
some problems which do not currently have well-described solutions.
This document aims to describe and illustrate these problems, and
propose some guidelines for possible solutions.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Overview of the Problem . . . . . . . . . . . . . . . 3
1.2 Terminology . . . . . . . . . . . . . . . . . . . . . 4
2. MIP and VPN Deployment Scenarios . . . . . . . . . . . . . . 4
2.1 MIPv4 HA(s) Inside the Intranet behind a VPN Gateway . 5
2.2 VPN Gateway and MIPv4 HA(s) on the VPN domain border . 6
2.3 Combined VPN Gateway and MIPv4 HA . . . . . . . . . . 7
2.4 MIPv4 HA(s) Outside the VPN domain . . . . . . . . . . 7
2.5 Combined VPN Gateway and MIPv4 HA(s) on the Local Link 8
3. Deployment Scenarios Selection . . . . . . . . . . . . . . . 9
4. Problem statement . . . . . . . . . . . . . . . . . . . . . 10
4.1 Registering in co-located mode . . . . . . . . . . . . 11
4.2 Registering via an FA . . . . . . . . . . . . . . . . 12
4.3 Summary: MIP Incompatibilities with IPsec-VPN
Gateways . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5. Solution Guidelines . . . . . . . . . . . . . . . . . . . . 14
5.1 Preservation of Existing VPN Infrastructure . . . . . 14
5.2 Software Upgrades to Existing VPN Client and Gateways 14
5.3 IPsec Protocol . . . . . . . . . . . . . . . . . . . . 14
5.4 Multi-Vendor Interoperability . . . . . . . . . . . . 14
5.5 MIPv4 Protocol . . . . . . . . . . . . . . . . . . . . 14
5.6 Handoff Overhead . . . . . . . . . . . . . . . . . . . 15
5.7 Scalability, Availability, Reliability, and Performance 15
5.8 Functional Entities . . . . . . . . . . . . . . . . . 15
5.9 Implications of Intervening NAT Gateways . . . . . . . 15
5.10 Security Requirements . . . . . . . . . . . . . . . . 15
6. Security Considerations . . . . . . . . . . . . . . . . . . 15
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
Normative References . . . . . . . . . . . . . . . . . . . . 16
Informative References . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . 19
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1. Introduction
Mobile IP [1] agents are being deployed in enterprise networks to
enable mobility across wired and wireless LANs while roaming inside
the enterprise Intranet. With the growing deployment of IEEE 802.11
access points ("hot spots") in public places such as hotels,
airports, and convention centers, and wireless WAN data networks such
as GPRS, the need for enabling mobile users to maintain their
transport connections and constant reachability while connecting back
to their target "home" networks protected by Virtual Private
Network (VPN) technology is increasing. This implies that Mobile IP
and VPN technologies have to coexist and function together in order
to provide mobility and security to the enterprise mobile users.
The goal of this draft is to:
o Identify and describe practical deployment scenarios for Mobile IP
and VPN in enterprise and operator environments.
o Identify example usage scenarios for remote users roaming outside
the "home" network protected by a VPN gateway.
o Articulate the problems resulting from Mobile IP and VPN
coexistence. Specify a set of framework guidelines to evaluate
proposed solutions, supporting multi-vendor seamless IPv4 mobility
across IPsec-based VPN gateways.
1.1 Overview of the Problem
Real life networks typically consist of three different domains from
a corporate point of view. The first domain is the Internet (i.e.,
the untrusted external network). The second domain is the trusted
Intranet (also referred to as VPN Domain in this document).
The third domain is the DMZ, which is between the Internet and the
Intranet.
Access to the Intranet is typically guarded by both a firewall and a
VPN device. The Intranet can only be accessed by respecting the
security policies in the firewall and the VPN device.
When MIP is deployed in a corporate network behind a VPN device,
roaming between these two different domains (i.e., the untrusted
Internet and the trusted Intranet) becomes problematic. It would be
desirable to have seamless session mobility between the two domains,
because MIP was designed for session mobility regardless of the
network point of attachment. Unfortunately, the current MIP
standards fall short of this promise for an important customer
segment, corporate users behind VPN gateways.
Because current standards do not provide for session mobility across
these two domains the possibility of finding a solution to this
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problem has been investigated. The goal is to provide seamless
session mobility when the mobile node moves between these two domains
or between subnets in either domain.
From the beginning it was also assumed that VPNs and
firewalls were to be taken as more or less granted because they have
much wider deployments than MIP at the present. Therefore any
solutions would need to minimize impact on existing VPN and
firewall deployments, related standards and "de facto" standards.
1.2 Terminology
MIPv4 Mobile IP for IPv4 [1]
MIPv6 Mobile IP for IPv6
VPN Virtual Private Network
GW Gateway
VPN Domain
An Intranet protected by a VPN gateway.
DMZ
(Demilitarized Zone) A small network inserted as a "neutral
zone" between a company's private network and the outside
public network to prevent outside users from getting direct
access to the company's private network
Home Network
A network, possibly virtual, having a network prefix matching
that of a mobile node's home address.
Home Agent
A router on a mobile node's home network which tunnels
datagrams for delivery to the mobile node when it is away
from home, and maintains current location information for the
mobile node.
MIPv4 inside IPsec-ESP tunnel
MIPv4 packet is encapsulated in an IPsec-ESP tunnel
established between the Mobile Node and the VPN gateway.
IPsec-ESP inside MIPv4 tunnel
IPsec-ESP packet is encapsulated in an MIPv4 tunnel
established between the Mobile Node and the home agent.
2. MIP and VPN Deployment Scenarios
This section describes a set of deployment scenarios where MIP agents
and VPN gateways have to coexist to provide mobility and security.
The intention is to identify practical deployment scenarios for MIP
and VPNs where MIP technology might be extended to solve problems
resulting from the desire for co-existence.
In all scenarios, "MN" refers to a mobile node that runs both MIP and
IPsec-based VPN client software. The foreign network might or
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might not employ a foreign agent. And, the term "Intranet"
refers to a private network protected by a VPN gateway and perhaps a
layer-3 transparent or non-transparent firewall. Please note that
firewalls are purposely omitted from the following scenarios,
because they may be installed in a number of different ways, and the
fact that this draft's focus is the relationship between MIP and VPN.
Finally, the scenarios assume that encryption is not enforced inside
the VPN domain because 1) the VPN domain (Intranet) is viewed as a
trusted network, and users allowed inside the Intranet are also
trusted 2) it is a common VPN deployment practice where the VPN is
used to guard the Intranet resources from unauthorized users attached
to an untrusted network, and to provide a secure communication
channel for authorized users to access resources inside the Intranet
from outside.
The following sub-sections introduce five representative
combinations of MIPv4 HA and VPN gateway placement.
2.1 MIPv4 HA(s) Inside the Intranet behind a VPN Gateway
MIPv4 HAs are deployed inside the Intranet protected by a VPN
gateway, and are not directly reachable by the MNs outside the
Intranet.
..Foreign Network.. .....VPN Domain..(Intranet).....
. . . .
. +----+ +----+ . +----+ +-------+ +-------+ .
. |MNs | | FA | . | VPN| | Router| | HA | .
. |away| | | .<=========>| | | 1..n | | 1..n | .
. +----+ +----+ . | GW | +-------+ +-------+ .
. . +----+ .
................... . +-------+ +-------+ .
. | CN | | MNs | .
. | 1..n | | home | .
. +-------+ +-------+ .
. .
................................
Figure 1
Direct application of MIPv4 standards [1] is successfully used to
provide mobility for users inside the Intranet. However, mobile
users outside the Intranet can only access the Intranet resources
(e.g., MIP agents) through the VPN gateway, which will allow only
authenticated IPsec traffic inside. This implies that the MIPv4
traffic has to run inside IPsec, which leads to two distinct
problems:
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1. When the foreign network has an FA deployed (as in e.g. CDMA
2000), MIPv4 registration becomes impossible because the traffic
between MN and VPN gateway, which is what the FA sees, is
encrypted and the FA is not set up to decrypt it.
2. In co-located mode, successful registration is possible but the
VPN tunnel has to be re-negotiated every time the MN changes its
point of network attachment.
These problems are articulated in Section 4.
This deployment scenario may not be common yet, but it is practical
and becoming important as there is an increasing need for providing
corporate remote users with continuous access to the Intranet
resources.
2.2 VPN Gateway and MIPv4 HA(s) on the VPN domain border
A MIPv4 HA is deployed on the VPN domain border (e.g., in the DMZ)
together with the VPN gateway, and it is directly reachable by MNs
inside or outside the Intranet.
..Foreign Network.. .....VPN Domain..(Intranet).....
. . . .
. +----+ +----+ . +----+ +-------+ .
. |MNs | | FA | . | VPN| | Router| .
. |away| | | .<=========>| | | 1..n | .
. +----+ +----+ . /\ | GW | +-------+ .
. . || +----+ .
. . || +----+ +-------+ +-------+ .
. . ++====>| HA | | CN | | MNs | .
................... | | | 1..n | | home | .
+----+ +-------+ +-------+ .
. .
................................
Figure 2
The MIPv4 HA has a public interface connected to the Internet, and a
private interface attached to the Intranet. Mobile users will most
likely have a virtual home network associated with the MIPv4 HA's
private interface, so that the mobile users are always away from home
and hence registered with the MIPv4 HA. Furthermore, in deployments
where the VPN gateway and the HA are placed in a corporate DMZ, this
implies that MIPv4 traffic will always be routed through the
DMZ (regardless of whether MNs are located outside or inside the
Intranet), which may not be acceptable by IT departments in large
corporations.
This deployment can be used with two different configurations: "MIPv4
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inside IPsec-ESP tunnel" and "IPsec-ESP inside MIPv4 tunnel". The
"MIPv4 inside IPsec-ESP tunnel" has the same problems as the scenario
of Section 2.1 (namely, MIPv4 registration becomes impossible when
the registration is to be done via an FA and furthermore in
co-located mode, the VPN tunnel has to be re-negotiated every time
the MN changes its point of attachment). The "IPsec-ESP inside MIPv4
tunnel" does not have problems described in Section 2.1, however it
will require some modifications to the routing logic of the MIPv4 HA
or the VPN gateway.
2.3 Combined VPN Gateway and MIPv4 HA
This is similar to deployment scenario described in Section 2.2, with
the exception that the VPN gateway and MIPv4 HA are running on the
same physical machine.
..Foreign Network.. .....VPN Domain..(Intranet).....
. . . .
. +----+ +----+ . +----+ +-------+ .
. |MNs | | FA | . | VPN| | Router| .
. |away| | | .<==========| GW | | 1..n | .
. +----+ +----+ . | + | +-------+ .
. . | HA | .
................... +----+ +-------+ +-------+ .
. | CN | | MNs | .
. | 1..n | | home | .
. +-------+ +-------+ .
. .
................................
Figure 3
Running MIPv4 HA and VPN on the same machine resolves routing
related issues that exist in Section 2.2 when a "IPsec-ESP inside
MIPv4 tunnel" configuration is used. However, it does not promote
multi-vendor interoperability in environments where MIPv4 HA and VPN
technologies must be acquired from different vendors.
2.4 MIPv4 HA(s) Outside the VPN domain
In this scenario, MIPv4 HAs are deployed outside the Intranet (e.g.,
in an operator network), as depicted in Figure 4 below.
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..Foreign Network.. .....VPN Domain..(Intranet).....
. . . .
. +----+ +----+ . +----+ +-------+ .
. |MNs | | FA | . | VPN| | Router| .
. |away| | | .<==========| GW | | 1..n | .
. +----+ +----+ . /\ | | +-------+ .
. . || | | .
................... || | | +-------+ +-------+ .
|| | | | CN | | MNs | .
.....MIPv4 Home.... || | | | 1..n | | home | .
. .<===++ | | +-------+ +-------+ .
. +------+ . +----+ .
. | HAs | . . .
. | 1..n | . ................................
. +------+ .
...................
Figure 4
In this deployment scenario the goal is to provide remote users with
continuous access to the Intranet resources while they are roaming
outside the Intranet only (i.e., mobility is not supported inside the
Intranet). In this case it is most practical to run IPsec-ESP inside
a MIPv4 tunnel (i.e., MIPv4 tunnel end-points are the MN and the HA;
the IPsec-ESP packet from the MN and to the VPN gateway is
encapsulated in the MIPv4 tunnel) as the MNs can register with the HA
without establishing an IPsec tunnel to the VPN gateway. This should
work without any technical problems. The IPsec tunnel end-points
will be the MN and the VPN gateway. The 'home network' will be a
virtual home network, located at the HA, from which it is possible to
reach the Corporate Intranet through the VPN gateway.
2.5 Combined VPN Gateway and MIPv4 HA(s) on the Local Link
This is similar to the deployment scenario described in Section 2.3,
with the difference that the VPN gateway/HA is sitting on the local
link. In this the VPN gateway and HA would most naturally be
co-located in the same box, although this is in no way a requirement.
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..Foreign Network.. .....VPN Domain..(Intranet).....
. . . .
. +----+ +----+ . +------+ +-------+ +-------+ .
. |MNs | | FA | . | Fire | | Router| | VPN/HA| .
. |away| | | .<=======>| wall | | 1..n | | 1..n | .
. +----+ +----+ . | | +-------+ +-------+ .
. . | NAT | .
................... +------+ +-------+ +-------+ .
. | CN | | MNs | .
. | 1..n | | home | .
. +-------+ +-------+ .
. .
................................
Figure 5
This deployment works today without any technical problems with
IPsec-ESP running inside a MIPv4 tunnel. If however MIPv4 is run
inside the IPsec-ESP tunnel it has the same problems as in Section
2.1 (namely, MIPv4 registration becomes impossible when the
registration is to be done via an FA and furthermore in co-located
mode, the VPN tunnel has to be re-negotiated every time the MN
changes its point of attachment). This deployment is not common or
practical for large deployments (on the order of thousands of users)
because of the large and distributed security perimeter.
3. Deployment Scenarios Selection
The deployment scenarios described in Section 2 were evaluated to
identify the ones most in need of solving. The evaluation was done
based on two main criteria: 1) Is the deployment scenario common and
practical? and 2) Does the deployment scenario reveal any problems
resulting from MIPv4 and VPN coexistence?
There was a consensus about importance and practicality of the
scenario in Section 2.1 because of rising needs to provide corporate
remote users with continuous access to their Intranet resources.
After analyzing each scenario one realizes that problems occurring in
scenarios in Section 2.2 and Section 2.4 are either the same as or a
subset of those in the scenario in Section 2.1. Therefore, solving
the scenario in Section 2.1 will also solve the scenarios in Section
2.2 and Section 2.4. The scenarios in Section 2.3 and Section 2.5 do
not introduce functional problems resulting from MIPv4 and VPN
co-existence, hence there is no need to seek a solution. A solution
for the deployment scenario in Section 2.1 is therefore seen as
essential, and this in turn can also be applied to solve problems in
other scenarios. For the remainder of this draft, we will articulate
the roaming scenarios, the problems, and the solution guidelines
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relevant to the scenario in Section 2.1.
4. Problem statement
This section describes roaming scenarios corresponding to the
deployment scenario in Section 2.1 where an MN needs to have
continuous access to the Intranet resources regardless of whether it
is roaming inside or outside the Intranet, and their associated
problems. The scenarios are constructed based on a multi-subnetted,
MIPv4-enabled Intranet (hereafter, referred to as Intranet or VPN
domain) protected by an IPsec-based VPN gateway as depicted in Figure
6.
....Internet....... .....VPN Domain..(Intranet).....
. . . .
. +----+ . +----+ +-------+ +-------+ .
. |MNs | . | VPN| | Router| | VPN/HA| .
. |away| .<=========>| | | 1..n | | 1..n | .
. +----+ . | GW | +-------+ +-------+ .
. . +----+ .
................... . +-------+ +-------+ .
. | CN | | MNs | .
. | 1..n | | home | .
. +-------+ +-------+ .
. .
................................
Figure 6: Intranet protected by a VPN Gateway
The Intranet, depicted in Figure 6, may include both wired (IEEE
802.3) and IEEE 802.11 wireless LAN deployments. However, it is also
possible to see IEEE 802.11 deployments outside the Intranet due to
the perceived lack of current 802.11 security, as depicted in Figure
7.
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....Internet....... .....VPN Domain..(Intranet).....
. . . .
. +----+ . +----+ +-------+ +-------+ .
. |MNs | . | VPN| | Router| | VPN/HA| .
. |away| .<=========>| | | 1..n | | 1..n | .
. +----+ . | GW | +-------+ +-------+ .
. . | | .
................... | | +-------+ +-------+ .
| | | CN | | MNs | .
..802.11 Wireless.. <====>| | | 1..n | | home | .
. Network . +----+ +-------+ +-------+ .
. . . .
................... ................................
Figure 7: IEEE 802.11 Wireless deployment outside the home network
4.1 Registering in co-located mode
In co-located mode, the IPsec tunnel endpoints would be at the MN and
the VPN gateway, which (supposing we have the scenario described in
Section 2.1) results in the mobile-ip tunnel from MN to HA being
encapsulated inside the IPsec tunnel. See Figure 8 below. This
scenario is still possible, but has some major drawbacks.
....Internet....... .....VPN Domain..(Intranet).....
. . . .
. +----+ . +----+ +-------+ +-------+ .
. |MNs | . | VPN| | Router| | VPN/HA| .
. |away|<###################>| |-----| 1..n |->| 1..n | .
. +----+ . \ | GW | +-------+ +-------+ .
. . \ +----+ .
................... mip . +-------+ +-------+ .
inside . | CN | | MNs | .
IPsec . | 1..n | | home | .
. +-------+ +-------+ .
. .
................................
Figure 8
The MN obtains an address at its point of attachment (via DHCP[7] or
some other means), and then first sets up an IPsec tunnel to the VPN
gateway, after which it can successfully register with its HA through
the IPsec tunnel. The problem is that in an end-to-end security
model, an IPsec tunnel that terminates at the VPN gateway must
protect the IP traffic originating at the MN. As the MN's IPsec
tunnel address is the address obtained at the point of attachment, it
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will change during movement, and the VPN tunnel security association
must be refreshed after each IP subnet handoff. This could have
noticeable performance implications on real-time applications. In
effect, we don't have mobility support for the tunnel endpoint
changes associated with MN movements.
4.2 Registering via an FA
In the case where a mobile node is in a network where mobility
support is provided through the use of an FA, and no DHCP allocated
address and co-located mode is possible, we run into severe trouble.
Figure 9 below illustrates this:
..Foreign Network.. .....VPN Domain..(Intranet).....
. . . .
. +----+ +----+ . +----+ +-------+ +-------+ .
. |MNs | | FA | . | VPN| | Router| | VPN/HA| .
. |away|<??| |<###########>| |-----| 1..n |->| 1..n | .
. +----+ \ +----+ . \ | GW | +-------+ +-------+ .
. \ . \ +----+ .
...........\....... mip . +-------+ +-------+ .
\ inside . | CN | | MNs | .
MN expects IPsec . | 1..n | | home | .
IPsec traffic . +-------+ +-------+ .
. .
................................
Figure 9
The mobile node, when arriving at this network, may have a IPsec
session going with its VPN gateway. This session will not be passed
through the FA as long as the MN has not registered and a mip tunnel
has been set up. But the MN, which is secure inside the IPsec based
VPN, will not even hear the FA advertisements. And any IPsec traffic
from the Intranet (via the VPN gateway and IPsec tunnel) will not be
understood by the FA. Simply put, you could say that the FA needs to
see the mip tunnel outermost, while the VPN-GW needs to see the IPsec
tunnel outermost. Or in more details:
Firstly, the MN must have a IPsec tunnel established with the VPN-GW
in order to reach the HA, which places the IPsec tunnel outside the
mip traffic between MN and HA. The FA (which is likely in a
different administrative domain) cannot decrypt MIPv4 packets between
the MN and the VPN gateway, and will consequently be not able to
relay the MIPv4 packets. This is because the MIPv4 headers (which
the FA should be able to interpret) will be encrypted and protected
by IPsec.
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Secondly, when the MN is communicating with the VPN-GW, an explicit
bypass policy for MIP packets is required, so that the MN can hear FA
advertisements and send and receive MIP registration packets.
Although not a problem in principle, there may be practical problems
when VPN and MIP clients from different vendors are used.
The use of a 'trusted FA' has been suggested in this scenario;
meaning an FA which is actually a combined VPN GW and FA. The
scenario will work fine in this case; effectively we are then
operating within the VPN established between the two VPN gateways,
and the case is analogous to deploying mobile-ip within a corporate
Intranet which is not physically disjoint. See Figure 10 below.
However, we cannot expect that e.g. wireless hot-spots or CDMA 2000
FAs will have VPN gateways with security associations with any given
corporate network, so this is not particularly realistic in the
general mobility case.
..Foreign Network.. .....VPN Domain..(Intranet).....
. . . .
. +----+ +----+ . +----+ +-------+ +-------+ .
. | FA | | VPN| . | VPN| | Router| | VPN/HA| .
. | |<--| GW |<###########>| |-----| 1..n |->| 1..n | .
. +----+ +----+ . \ | GW | +-------+ +-------+ .
. | . \ +----+ .
. +----+ . mip . +-------+ +-------+ .
. |MNs | . inside . | CN | | MNs | .
. |away| . IPsec . | 1..n | | home | .
. +----+ . . +-------+ +-------+ .
................... . .
................................
Figure 10
Furthermore, this solution would leave the traffic between FA and MN
unprotected, and as this link in particular may be a wireless link,
this is clearly undesirable.
4.3 Summary: MIP Incompatibilities with IPsec-based VPN Gateways
An MN roaming outside the Intranet has to establish an IPsec tunnel
to its home VPN gateway first, in order to be able to register with
its home agent. This is because the MN cannot reach its HA (inside
the private protected network) directly from the outside. This
implies that the MIPv4 traffic from the MN to a node inside the
Intranet is forced to run inside an IPsec tunnel, and hence will not
be in the clear. This in turn leads to two distinct problems
depending on whether the MN uses co-located or non co-located modes
to register with its HA.
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5. Solution Guidelines
This section describes guidelines for a solution to MIPv4 traversal
across VPN gateways.
5.1 Preservation of Existing VPN Infrastructure
o The solution MUST preserve the investment in existing VPN
gateways.
o The solution MUST provide security which is not inferior to what
is already provided to existing "nomadic computing" remote access
users, i.e. for confidentiality, authentication, message
integrity, protection against replay attacks and related security
services.
5.2 Software Upgrades to Existing VPN Client and Gateways
o The solution SHOULD minimize changes to existing VPN client/
gateway software.
5.3 IPsec Protocol
o The solution SHOULD NOT require any changes to existing IPsec or
key exchange standard protocols implemented by VPN gateways.
o The solution SHOULD NOT require that the VPN gateway or the VPN
client implement any new protocols in addition to the existing
standard protocols.
5.4 Multi-Vendor Interoperability
o The solution MUST provide multi-vendor interoperability, where
MIPv4 mobility agents, mobility clients (MN), VPN server, and VPN
client solutions may come from four different vendors. This is
typical for medium and large enterprises which purchase and deploy
best-of-breed multi-vendor solutions for IP routing, VPNs,
firewalls etc.
5.5 MIPv4 Protocol
o The solution MUST adhere to MIPv4 protocol [1]. That is, the
solution MUST NOT impose any changes that violates MIPv4 protocol.
o The solution MAY introduce new extensions to MIPv4 nodes per
guidelines specified in the MIPv4 protocol [1]. However, it is
highly desirable to avoid any changes to MIPv4 mobility agents
such as the FA and HA in order to overcome barriers to
deployment.
o The solution MAY require more than one instance of MIPv4 running
in parallel (multiple encapsulation).
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5.6 Handoff Overhead
o It is imperative to keep the key management overhead down to a
minimum, in order to support fast handoffs across IP subnets.
Hence, the solution MUST propose a mechanism to avoid or minimize
IPsec tunnel SA renegotiation and IKE renegotiation as the MN
changes its current point of network attachment.
5.7 Scalability, Availability, Reliability, and Performance
o The solution complexity MUST increase at most linearly with the
number of MNs registered and accessing resources inside the
Intranet.
o The solution MAY introduce additional header or tunnelling
overhead if needed.
5.8 Functional Entities
o The solution MAY introduce new MIPv4 compliant functional
entities.
5.9 Implications of Intervening NAT Gateways
o The solution MUST be able to leverage the existing MIPv4 and IPsec
NAT traversal solutions [9][10][11].
5.10 Security Requirements
o The solution MUST NOT introduce any new vulnerabilities to the
MIPv4 or IPsec as specified in related RFCs.
6. Security Considerations
This document describes an existing problem and proposes guidelines
for possible solutions; as such its security implications are
indirect, through the guidelines it proposes for the solutions.
Section 5.10 gives the relevant security requirements.
7. Acknowledgements
The authors who contributed text to this document were in no
particular order: Farid Adrangi, Milind Kulkarni, Gopal Dommety, Eli
Gelasco, Qiang Zhang, Sami Vaarala, Dorothy Gellert, Nitsan Baider
and Henrik Levkowetz.
The authors would like to thank other contributors, especially
Prakash Iyer, Mike Andrews, Ranjit Narjala, Joe Lau, Kent Leung,
Alpesh Patel, Phil Roberts, Hans Sjostrand, Serge Tessier, Antti
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Internet-Draft MIPv4 VPN Traversal Problem Statement February 2004
Nuopponen, Alan O'neill, Gaetan Feige, Brijesh Kumar for their
continuous feedback and helping us improve this draft.
Normative References
[1] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August
2002.
Informative References
[2] Hanks, S., Li, T., Farinacci, D. and P. Traina, "Generic
Routing Encapsulation (GRE)", RFC 1701, October 1994.
[3] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and E.
Lear, "Address Allocation for Private Internets", BCP 5, RFC
1918, February 1996.
[4] Perkins, C., "Minimal Encapsulation within IP", RFC 2004,
October 1996.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[6] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[7] Srisuresh, P. and M. Holdrege, "IP Network Address Translator
(NAT) Terminology and Considerations", RFC 2663, August 1999.
[8] Montenegro, G., "Reverse Tunneling for Mobile IP, revised", RFC
3024, January 2001.
[9] Levkowetz, H. and S. Vaarala, "Mobile IP Traversal of Network
Address Translation (NAT) Devices", RFC 3519, May 2003.
[10] Aboba, B. and W. Dixon, "IPsec-NAT Compatibility Requirements",
draft-ietf-ipsec-nat-reqts-06 (work in progress), October 2003.
[11] Kivinen, T., "Negotiation of NAT-Traversal in the IKE",
draft-ietf-ipsec-nat-t-ike-07 (work in progress), September
2003.
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Authors' Addresses
Farid Adrangi
Intel Corporation
2111 N.E. 25th Avenue
Hillsboro OR
USA
Phone: +1 503-712-1791
EMail: farid.adrangi@intel.com
Henrik Levkowetz
ipUnplugged AB
Arenavagen 33
Stockholm S-121 28
SWEDEN
Phone: +46 8 725 9513
EMail: henrik@levkowetz.com
Milind Kulkarni
Cisco Systems
170 W. Tasman Drive
San Jose CA 95134
USA
Phone: +1 408-527-8382
EMail: mkulkarn@cisco.com
Gopal Dommety
Cisco Systems
170 W. Tasman Drive
San Jose CA 95134
USA
EMail: gdommety@cisco.com
Eli Gelasco
Cisco Systems
170 W. Tasman Drive
San Jose CA 95134
USA
EMail: egelasco@cisco.com
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Qiang Zhang
Liqwid Networks, Inc.
1000 Wilson Blvd, Suite 900
Arlington VA 22209
USA
Phone: +1 703-224-1120 -x 203
EMail: qzhang@liqwidnet.com
Sami Vaarala
Netseal
Niittykatu 6
Espoo 02201
FINLAND
Phone: +358 9 435 310
EMail: sami.vaarala@iki.fi
Dorothy Gellert
Nokia Corporation
EMail: dorothy.gellert@nokia.com
Nitsan Baider
Check Point Software Technologies, Inc.
EMail: nitsan@checkpoint.com
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Internet-Draft MIPv4 VPN Traversal Problem Statement February 2004
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