IPsecME Working Group S. Hanna
Internet-Draft Juniper
Intended status: Informational V. Manral
Expires: November 26, 2012 HP
May 25, 2012
Auto Discovery VPN Problem Statement
draft-ietf-ipsecme-p2p-vpn-problem-01
Abstract
This document describes the problem of enabling a large number of
systems to communicate directly using IPsec to protect the traffic
between them. Manual configuration of all possible tunnels is too
cumbersome in many such cases. In other cases the IP address of end
points change or the end points may be behind NAT gateways, making
static configuration impossible. The Auto Discovery VPN solution is
chartered to address these requirements.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 26, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Conventions Used in This Document . . . . . . . . . . . . 4
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Endpoint-to-Endpoint P2P VPN Use Case . . . . . . . . . . 5
2.2. Gateway-to-Gateway AD VPN Use Case . . . . . . . . . . . . 5
2.3. Endpoint-to-Gateway AD VPN Use Case . . . . . . . . . . . 6
3. Inadequacy of Existing Solutions . . . . . . . . . . . . . . . 7
3.1. Exhaustive Configuration . . . . . . . . . . . . . . . . . 7
3.2. Star Topology . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Proprietary Approaches . . . . . . . . . . . . . . . . . . 8
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
8. Normative References . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
IPsec [RFC4301] is used in several different cases, including tunnel-
mode site-to-site VPNs and Remote Access VPNs. Host to host
communication employing transport mode also exists, but is far less
commonly deployed.
The subject of this document is the problem presented by large scale
deployments of IPsec. These may be a large collection of VPN
gateways connecting various sites, a large number of remote endpoints
connecting to a number of gateways or to each other, or a mix of the
two. The gateways and endpoints may belong to a single
administrative domain or several domains with a trust relationship.
Section 4.4 of RFC 4301 describes the major IPsec databases needed
for IPsec processing. It requires an extensive configuration for
each tunnel, so manually configuring a system of many gateways and
endpoints becomes infeasible and inflexible.
The difficulty is that all the configuration mentioned in RFC 4301 is
not superfluous. IKE implementations need to know the identity and
credentials of all possible peer systems, as well as the addresses of
hosts and/or networks behind them. A simplified mechanism for
dynamically establishing point-to-point tunnels is needed. Section 2
contains several use cases that motivate this effort.
1.1. Terminology
Endpoint - A host that implements IPsec for its own traffic but does
not act as a gateway.
Gateway - A network device that implements IPsec to protect traffic
flowing through the device.
Point-to-Point - Direct communication between two parties without
active participation (e.g. encryption or decryption) by any other
parties.
Hub - The central point in a star topology, generally implemented in
a gateway
Spoke - The edge devices in a star topology, implemented in endpoints
or gateways
Security Association (SA) - Defined in [RFC4301].
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1.2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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2. Use Cases
This section presents the key use cases for large-scale point-to-
point VPN.
In all of these use cases, the participants (endpoints and gateways)
may be from a single organization or from multiple organizations with
an established trust relationship. When multiple organizations are
involved, products from multiple vendors are employed so open
standards are needed to provide interoperability. Establishing
communications between participants with no established trust
relationship is out of scope for this effort.
2.1. Endpoint-to-Endpoint P2P VPN Use Case
Two endpoints wish to communicate securely via a direct, point-to-
point SA.
The need for secure endpoint to endpoint communications is often
driven by a need to employ high-bandwidth, low latency local
connectivity instead of using slow, expensive links to remote
gateways. For example, two users in close proximity may wish to
place a direct, secure video or voice call without needing to send
the call through remote gateways, which would add latency to the
call, consume precious remote bandwidth, and increase overall costs.
Such a usecase also enables connectivity when both endpoints are
behind NAT gateways. Such usecase should allow for seamless
connectivity even as Endpoints roam, in behing or away from gateways.
In a hub and spoke topology when two end-points communicate, they
must use a mechanism for authentication, such that they do not expose
them to impersonation by the other spoke endpoint.
2.2. Gateway-to-Gateway AD VPN Use Case
A typical Enterprise traffic model is Hub and Spoke, with the
Gateways connecting to each other using IPsec tunnels.
However for the voice and other rich media traffic that occupies a
lot of bandwidth and the traffic tromboning to the Hub can create
traffic bottlenecks on the Hub and can lead to a increase cost. It
is for this purpose Spoke-to-Spoke tunnels are dynamically created
and torn-down.
The Spoke Gateways can themselves come up and down, getting different
IP addresses in the process, making th static configuration
impossible.
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Also for the reasons of cost and manual error reduction, it is
desired there be minimal or even no configuration on the Hub as a new
Spoke Router is added or removed.
In a hub and spoke topology when two spoke gateways communicate, they
must use a mechanism for authentication, such that they do not expose
them to impersonation by the other gateways spoke.
2.3. Endpoint-to-Gateway AD VPN Use Case
An endpoint should be able to use the most efficient gateway as it
roams in the internet.
A mobile user roaming on the Internet may connect to a gateway, which
because of roaming is no longer the most efficient gateway to use
(reasons could be cost/ efficiency/ latency or some other factor).
The mobile user should be able to discover and then connect to the
current most efficient gateway without having to reinitiate the
connection.
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3. Inadequacy of Existing Solutions
Several solutions exist for the problems described above. However,
none of these solutions is adequate, as described here.
3.1. Exhaustive Configuration
One simple solution is to configure all gateways and endpoints in
advance with all the information needed to determine which gateway or
endpoint is optimal and to establish an SA with that gateway or
endpoint. However, this solution does not scale in a large network
with hundreds of thousands of gateways and endpoints, especially when
multiple organizations are involved and things are rapidly changing
(e.g. mobile endpoints). Such a solution is also limited by the
smallest endpoint/ gateway, as the same exhaustive configuration is
to be applied on all endpoints/ gateways. A more dynamic, secure and
scalable system for establishing SAs between gateways is needed.
3.2. Star Topology
The most common way to address this problem today is to use what has
been termed a "star topology". In this case one or a few gateways
are defined as "Hub gateways", while the rest of the systems (whether
endpoints or gateways) are defined as "spokes". The spokes never
connect to other spokes. They only open tunnels with the core
gateways. Also for a large number of gateways in one administrative
domain, one gateway may be defined as the core, and the rest of the
gateways and remote access clients connect only to that gateway.
This solution however does not work when the spokes, get dynamic IP
address which the "core gateways" cannot be configured with. It is
also desired that there is minimal to no configuration on the Hub as
the number of spokes increases and new spokes are added and deleted
randomly.
Another problem with stars and trunks is that it creates a high load
on the core gateways as well as on the trunk connection. This load
is both in processing power and in network bandwidth. A single
packet in the trunk scenario can be encrypted and decrypted three
times. It would be much preferable if these gateways and clients
could initiate tunnels between them, bypassing the core gateways.
Additionally, the path bandwidth to these core gateways may be lower
than that of the path between the satellites. For example, two
remote access users may be in the same building with high-speed wifi
(for example, at an IETF meeting). Channeling their conversation
through the core gateways of their respective employers seems
extremely wasteful, as well as having lower bandwidth.
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The challenge is to build a large scale, IPsec protected networks
that can dynamically change with minimum administrative overhead.
3.3. Proprietary Approaches
Several vendors offer proprietary solutions to these problems.
However, these solutions offer no interoperability between equipment
from one vendor and another. This means that they are generally
restricted to use within one organization, and it is harder to move
off such solutions as the features are not standardized. Besides
multiple organizations cannot be expected to all choose the same
equipment vendor.
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4. Requirements
This section will be completed when the use cases are agreed upon.
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5. Security Considerations
The solution to the problems presented in this draft may involve
dynamic updates to databases defined by RFC 4301, such as the
Security Policy Database (SPD) or the Peer Authorization Database
(PAD).
RFC 4301 is silent about the way these databases are populated, and
it is implied that these databases are static and pre-configured by a
human. Allowing dynamic updates to these databases must be thought
out carefully, because it allows the protocol to alter the security
policy that the IPsec endpoints implement.
One obvious attack to watch out for is stealing traffic to a
particular site. The IP address for www.example.com is 192.0.2.10.
If we add an entry to an IPsec endpoint's SPD that says that traffic
to 192.0.2.10 is protected through peer Gw-Mallory, then this allows
Gw-Mallory to either pretend to be www.example.com or to proxy and
read all traffic to that site. Updates to this database requires a
clear trust model.
More to be added.
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6. IANA Considerations
No actions are required from IANA for this informational document.
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7. Acknowledgements
Many people have contributed to the development of this problem
statement and many more will probably do so before we are done with
it. While we cannot thank all contributors, some have played an
especially prominent role. Yoav Nir, Yaron Scheffer, Jorge Coronel
Mendoza, Chris Ulliott, and John Veizades wrote the document upon
which this draft was based. Geoffrey Huang, Suresh Melam, Praveen
Sathyanarayan, Andreas Steffen, and Brian Weis provided essential
input.
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8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
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Authors' Addresses
Steve Hanna
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: shanna@juniper.net
Vishwas Manral
Hewlett-Packard Co.
19111 Pruneridge Ave.
Cupertino, CA 95113
USA
Email: vishwas.manral@hp.com
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