IPsecME Working Group S. Hanna Internet-Draft Juniper Intended status: Informational V. Manral Expires: February 22, 2013 HP August 21, 2012 Auto Discovery VPN Problem Statement and Requirements draft-ietf-ipsecme-ad-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. It then expands on the requirements, for such a solution. Manual configuration of all possible tunnels is too cumbersome in many such cases. In other cases the IP address of endpoints change or the endpoints 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. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on February 22, 2013. 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 Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of Hanna & Manral Expires February 22, 2013 [Page 1] Internet-Draft Auto Discovery VPN August 2012 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as 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 AD 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 4.1. Gateway and Endpoint Requirements . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 8. Normative References . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Hanna & Manral Expires February 22, 2013 [Page 2] Internet-Draft Auto Discovery VPN August 2012 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 and the requirements on a solution to address the problem. 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 device 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]. Hanna & Manral Expires February 22, 2013 [Page 3] Internet-Draft Auto Discovery VPN August 2012 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]. Hanna & Manral Expires February 22, 2013 [Page 4] Internet-Draft Auto Discovery VPN August 2012 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 AD VPN Use Case Two endpoints wish to communicate securely via a direct, point-to- point Security Association (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 use case also enables connectivity when both endpoints are behind NAT gateways. Such use case should allow for seamless connectivity even as endpoints roam, even if they are moving out from behind a gateway, from behind one gateway to behind another, or from a standalone position to behind a gateway. In a hub and spoke topology when two endpoints 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 Hanna & Manral Expires February 22, 2013 [Page 5] Internet-Draft Auto Discovery VPN August 2012 impossible. 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. Hanna & Manral Expires February 22, 2013 [Page 6] Internet-Draft Auto Discovery VPN August 2012 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 hub gateways. Also for a large number of gateways in one administrative domain, one gateway may be defined as the hub, 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 "hub 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 the star topology is that it creates a high load on the hub gateways as well as on the connection between the spokes and the hub. This load is both in processing power and in network bandwidth. A single packet in the hub-and-spoke 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 hub gateways. Additionally, the path bandwidth to these hub gateways may be lower than that of the path between the spokes. 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 hub gateways of their respective employers seems extremely wasteful, as well as having lower bandwidth. Hanna & Manral Expires February 22, 2013 [Page 7] Internet-Draft Auto Discovery VPN August 2012 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. Hanna & Manral Expires February 22, 2013 [Page 8] Internet-Draft Auto Discovery VPN August 2012 4. Requirements This section is currently being updated and hence under flux. 4.1. Gateway and Endpoint Requirements 1. For any network topology (whether hub-and-spoke or Full Mesh) gateways and endpoints MUST minimize configuration changes when a new gateway or endpoint is added, removed or changed. Specifically, when evaluating potential solutions, we will compare them by looking at how many endpoints or gateways must be reconfigured when a new gateway or endpoint is added, removed, or changed and how substantial this reconfiguration is. This requirement is driven by use cases 2.1 and 2.2 and by the scaling limitations pointed out in section 3.1. 2. Gateways and endpoints MUST allow IPsec Tunnels to be setup without any configuration changes, even when peer addresses get updated every time the device comes up. This implies that SPD entries or other configuration based on peer IP address will need to be automatically updated, avoided, or handled in some manner to avoid a need to manually update policy whenever an address changes. This requirement is driven by use cases 2.1 and 2.2 and by the scaling limitations pointed out in section 3.1. 3. Gateways MUST allow tunnel binding, such that applications like Routing using the tunnels can work seamlessly without any updates to the higher level application configuration i.e. OSPF configuration. 4. In a hub-and-spoke topology, spoke gateways and endpoints MUST allow for direct communication with other spoke gateways and endpoints. This requirement is driven by use cases 2.1 and 2.2 and by the limitations of a star topology pointed out in section 3.2. 5. One spoke MUST NOT be able to impersonate another spoke. This requirement is driven by use case 2.1. Endpoints become compromised fairly often. The compromise of one endpoint should not affect the security of other endpoints. 6. Gateways SHOULD allow for easy handoff of sessions in case endpoints are roaming, even if they cross policy boundaries. This means that TCP session breakage and packet loss should be avoided, when possible. Hanna & Manral Expires February 22, 2013 [Page 9] Internet-Draft Auto Discovery VPN August 2012 This requirement is driven by use case 2.1. Today's endpoints are mobile and transition often between different networks (from 4G to WiFi and among various WiFi networks). 7. Gateways SHOULD allow for easy handoff of a session to another gateway, to optimize latency, bandwidth, load balancing, availability, or other factors, based on policy. This requirement is driven by use case 2.3. 8. Gateways and endpoints MUST be able to work when they are behind NAT boxes. However, it is especially difficult to handle cases where gateways are behind NATs and where two endpoints are both behind separate NATs. In those cases, workarounds MAY be used such as port forwarding by the NAT or detecting when two spokes are behind uncooperative NATs and using a hub in that case. This requirement is driven by use cases 2.1 and 2.2. Endpoints are often behind NATs and gateways sometimes are. IPsec should continue to work seamlessly regardless, using AD VPN techniques whenever possible and providing graceful fallback to hub and spoke techniques as needed. 9. Changes such as establishing a new IPsec SA SHOULD be reportable and manageable. However, creating a MIB or other management technique is not within scope for this effort. This requirement is driven by manageability concerns for all the use cases, especially use case 2.2. As IPsec networks become more dynamic, management tools become more essential. 10. To support allied and federated environments, endpoints and gateways from different organizations SHOULD be able to connect to each other. This requirement is driven by demand for all the use cases in federated and allied environments. 11. The solution SHOULD allow administrators the ability to configure a variety of permissible topologies: full mesh, partial mesh, star, etc. They should be able to set different topologies for different types of traffic: voice, video, web, email, etc. This requirement is driven by counter-balancing requirements to log or control traffic of certain types (e.g. email) while ensuring efficient, low-latencies flows of other types (e.g. video). Hanna & Manral Expires February 22, 2013 [Page 10] Internet-Draft Auto Discovery VPN August 2012 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. Hanna & Manral Expires February 22, 2013 [Page 11] Internet-Draft Auto Discovery VPN August 2012 6. IANA Considerations No actions are required from IANA for this informational document. Hanna & Manral Expires February 22, 2013 [Page 12] Internet-Draft Auto Discovery VPN August 2012 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. Hanna & Manral Expires February 22, 2013 [Page 13] Internet-Draft Auto Discovery VPN August 2012 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. Hanna & Manral Expires February 22, 2013 [Page 14] Internet-Draft Auto Discovery VPN August 2012 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 Hanna & Manral Expires February 22, 2013 [Page 15]