IPsecME Working Group                                           S. Hanna
Internet-Draft                                                   Juniper
Intended status: Informational                                 V. Manral
Expires: June 10, 20, 2013                                                HP
                                                       December 7, 17, 2012

         Auto Discovery VPN Problem Statement and Requirements
                  draft-ietf-ipsecme-ad-vpn-problem-02
                  draft-ietf-ipsecme-ad-vpn-problem-03

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

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on June 10, 20, 2013.

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   document authors.  All rights reserved.

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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  . . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  Normative References . . . . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16

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/ dynamic full mesh
   topology, or one of the central points in the full mesh style VPN,
   i.e. gateway where multiple other hubs or spokes connect to.  The
   hubs usually forward traffic coming from encrypted links to other
   encrypted links, i.e. there is no devices connected to it in clear.

   Spoke - The edge devices in the a star topology/ dynamic full mesh
   topology, or gateway which forwards traffic from multiple cleartext
   devices to other hubs or spokes, and some of those other devices are
   connected to it in clear (i.e. it encrypt data coming from cleartext
   device and forwards it to the AD VPN).

   Star topology - This is the topology where there is direct
   connectivity only between the hub and spoke and communication between
   the 2 spokes happens through the hub.

   Full Mesh topology - This is the topology where there is a direct
   connectivity between every Spoke to every other Spoke directly,
   without the traffic between the spokes having to be redirected
   through an intermediate hub device.

   Dynamic Full Mesh topology - This is the topology where direct
   connections exist in a hub and spoke manner, but dynamic connections
   are created/ removed between the spokes on a need basis.

   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].

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 NAT gateway, from behind one NAT gateway to behind another,
   or from a standalone position to behind a NAT 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 follows a star topology, with the
   gateways connecting to each other using IPsec tunnels.

   However for the voice and other rich media traffic that requires a
   lot of bandwidth or is performance sensitive, the traffic tromboning
   to the hub can create traffic bottlenecks on the hub and can lead to
   an increase in cost.  A fully meshed solution is would make best use of
   the available network capacity and performance but the deployment of
   a fully meshed solution involves considerable configuration,
   especially when a large number of nodes are involved.  It is for this
   purpose spoke-to-spoke tunnels are dynamically created and torn-down.

   For the reasons of cost and manual error reduction, it is desired
   that there be minimal configuration on each gateway.

   The solution should work in cases where the endpoints are
   administrated by separate management domains, albeit, ones that have
   an existing trust relationship (for example two organisations who are
   collaborating on a project, they may wish to join their networks,
   whilst retaining independent control over configuration).  It is
   highly desirable that the solution works for the star, full mesh as
   well as dynamic full mesh topology.

   The solution should also address the case where gateways use dynamic
   IP addresses.

   Additionally, the routing implications of gateway-to-gateway
   communication must be addressed.  In the simple case, selectors
   provide sufficient information for a gateway to forward traffic
   appropriately.  In other cases, additional tunneling (e.g., GRE) and
   routing (e.g., OSPF) protocols are run over IPsec tunnels, and the
   configuration impact on those protocols must be considered.  There is
   also the case when L3VPNs operate over IPsec Tunnels.

   When two gateways communicate, they must use a mechanism for
   authentication, such that they do not expose themselves to the risk
   of impersonation by the other entities.

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.

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 a part of this 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 is complicated by the case when the spokes use
   dynamic IP addresses and DNS with dynamic updates must be used.  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 multiple 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.

   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.

4.  Requirements

   This sectiondefines section defines the requirements, on which the solution will be
   based.

4.1.  Gateway and Endpoint Requirements

   1.  For any network topology (star, full mesh and dynamic full mesh)
   gateways and endpoints MUST SHOULD minimize configuration changes when a
   new gateway or endpoint is added, removed or changed.  Adding or
   removing a spoke in the topology MUST NOT require configuration
   changes to the hubs other than where the spoke was connected to and
   SHOULD NOT require configuration changes to the hub the spoke was
   connected to.  The changes also MUST NOT require configuration
   changes in other spokes.

   Specifically, when evaluating potential proposals, 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, besides the
   amount of static configuration required.

   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.  In many cases additional tunneling protocols (e.g.  GRE) or
   Routing protocols (e.g.  OSPF) are run over the IPsec tunnels.
   Gateways MUST allow for the operation of tunneling and Routing
   protocols operating over spoke-to-spoke IPsec Tunnels with minimal or
   no, configuration impact.  The ADVPN solution SHOULD NOT increase the
   amount of information required to configure protocols running over
   IPsec tunnels.

   4.  In the full mesh and dynamic full mesh topology, Spokes MUST
   allow for direct communication with other spoke gateways and
   endpoints.  In the star topology mode, direct communication between
   spokes MUST be disallowed.

   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.  Spokes become
   compromised fairly often.  The compromise of one Spoke should not
   affect the security of other endpoints.

   6.  Gateways SHOULD allow for seamless handoff of sessions in case
   endpoints are roaming, even if they cross policy boundaries.  This
   would mean the data traffic is minimally affected even as the handoff
   happens.  External factors like firewall, NAT box will not be
   considered part of this solution.

   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 have the capability to work participate in
   an AD VPN even when they are located behind NAT boxes.  However, in
   some cases they may be deployed in such a way that they will not be
   fully reachable behind a NAT box.  It is especially difficult to
   handle cases where the Hub is behind a NAT box, such a requirement MAY be supported. box.  Where the two
   endpoints are both behind separate NATs, communication between these
   spokes SHOULD be supported.  In the cases, supported using 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.

   11.  The administrator of the ADVPN SHOULD allow for the
   configuration of a Star, Full mesh or a partial full mesh topology,
   based on which tunnels are allowed to be setup.

   This requirement is driven by demand for all the use cases in
   federated and allied environments.

   12.  The ADVPN solution SHOULD be able to scale for multicast
   traffic.

   This requirement is driven by the use case 2.2, where the amount of
   rich media multicast traffic is increasing.

   13.  The ADVPN solution SHOULD allow for easy monitoring, logging and
   reporting of the dynamic changes, to help for trouble shooting such
   environments.

   This requirement is driven by demand for all the use cases in
   federated and allied environments.

   14.  The ADVPN solution MUST support  There is also the case when L3VPNs operate over IPsec Tunnels,
   for example Provider Edge (PE) based VPN's.  An ADVPN MUST support
   L3VPN as an application protected by the IPsec Tunnels.

   This requirement is driven by demand for all the use cases in
   federated and allied environments.

5.  Security Considerations

   This is a Problem state and requirement document for the ADVPN
   solution, and in itself does not introduce any new security concerns.
   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.

6.  IANA Considerations

   No actions are required from IANA for this informational document.

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, Sheffer, 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, Brian Weis, and Lou Berger provided
   essential input.

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.

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