IPsecME Working Group S. Hanna
Internet-Draft Juniper
Intended status: Informational March 5, 2012
Expires: September 6, 2012
Point to Point VPNs Problem Statement
draft-ietf-ipsecme-p2p-vpn-problem-00
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 such cases, so an automated method is needed.
Status of this Memo
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This Internet-Draft will expire on September 6, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Conventions Used in This Document . . . . . . . . . . . . 3
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Endpoint-to-Endpoint P2P VPN Use Case . . . . . . . . . . 4
2.2. Gateway-to-Gateway P2P VPN Use Case . . . . . . . . . . . 4
2.3. Endpoint-to-Gateway P2P VPN Use Case . . . . . . . . . . . 4
3. Inadequacy of Existing Solutions . . . . . . . . . . . . . . . 6
3.1. Exhaustive Configuration . . . . . . . . . . . . . . . . . 6
3.2. Star Topology . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Proprietary Approaches . . . . . . . . . . . . . . . . . . 7
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
8. Normative References . . . . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
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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.
Security Association (SA) - Defined in [RFC4301].
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.
2.2. Gateway-to-Gateway P2P VPN Use Case
Two gateways suddenly need to exchange a lot of data.
For example, a mobile worker from one government agency may sit down
in a shared remote office and start up his VOIP or video phone
software. He should rapidly get an efficient, secure, low latency
connection to his voice mail system and to anyone that he might call.
This user, his voice mail system, and other people that he calls will
probably be operating behind gateways but those gateways may have
little advance warning of the need to establish secure connectivity
between them.
2.3. Endpoint-to-Gateway P2P VPN Use Case
An endpoint wants to connect directly to the most efficient gateway
for accessing a particular service.
For example, a mobile user roaming on the Internet may need to open a
remote desktop connection to a virtual machine hosted on a particular
server or to a service provided by a variety of servers distributed
around the globe. The user should be able to establish a connection
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directly to the gateway closest to the service desired. If multiple
gateways can suffice, load balancing and failover across gateways may
be useful.
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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). A more dynamic system for securely and
scalably 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 "core gateways", while the rest of the systems
(whether endpoints or gateways) are defined as "satellites". The
satellites never connect to other satellites. They only open tunnels
with the core gateways.
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. If the packet
destination is behind another gateway, then the core gateway will re-
encrypt the traffic, and send it through the other tunnel. If we
have two collections of gateways under two administrative domains,
then each domain has its own core, and the administrators only need
to define an IPsec tunnel between the two cores. This tunnel is
often referred to as a "trunk".
One 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 how to build large scale, fully meshed 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. 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, 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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Author's Address
Steve Hanna
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: shanna@juniper.net
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