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Manral 5 Expires: May 30, 2013 HP 6 November 26, 2012 8 Auto Discovery VPN Problem Statement and Requirements 9 draft-ietf-ipsecme-ad-vpn-problem-01 11 Abstract 13 This document describes the problem of enabling a large number of 14 systems to communicate directly using IPsec to protect the traffic 15 between them. It then expands on the requirements, for such a 16 solution. 18 Manual configuration of all possible tunnels is too cumbersome in 19 many such cases. In other cases the IP address of endpoints change 20 or the endpoints may be behind NAT gateways, making static 21 configuration impossible. The Auto Discovery VPN solution is 22 chartered to address these requirements. 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on May 30, 2013. 41 Copyright Notice 43 Copyright (c) 2012 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 60 1.2. Conventions Used in This Document . . . . . . . . . . . . 4 61 2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5 62 2.1. Endpoint-to-Endpoint AD VPN Use Case . . . . . . . . . . . 5 63 2.2. Gateway-to-Gateway AD VPN Use Case . . . . . . . . . . . . 5 64 2.3. Endpoint-to-Gateway AD VPN Use Case . . . . . . . . . . . 6 65 3. Inadequacy of Existing Solutions . . . . . . . . . . . . . . . 7 66 3.1. Exhaustive Configuration . . . . . . . . . . . . . . . . . 7 67 3.2. Star Topology . . . . . . . . . . . . . . . . . . . . . . 7 68 3.3. Proprietary Approaches . . . . . . . . . . . . . . . . . . 8 69 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 9 70 4.1. Gateway and Endpoint Requirements . . . . . . . . . . . . 9 71 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 72 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 73 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 74 8. Normative References . . . . . . . . . . . . . . . . . . . . . 15 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 77 1. Introduction 79 IPsec [RFC4301] is used in several different cases, including tunnel- 80 mode site-to-site VPNs and Remote Access VPNs. Host to host 81 communication employing transport mode also exists, but is far less 82 commonly deployed. 84 The subject of this document is the problem presented by large scale 85 deployments of IPsec and the requirements on a solution to address 86 the problem. These may be a large collection of VPN gateways 87 connecting various sites, a large number of remote endpoints 88 connecting to a number of gateways or to each other, or a mix of the 89 two. The gateways and endpoints may belong to a single 90 administrative domain or several domains with a trust relationship. 92 Section 4.4 of RFC 4301 describes the major IPsec databases needed 93 for IPsec processing. It requires an extensive configuration for 94 each tunnel, so manually configuring a system of many gateways and 95 endpoints becomes infeasible and inflexible. 97 The difficulty is that all the configuration mentioned in RFC 4301 is 98 not superfluous. IKE implementations need to know the identity and 99 credentials of all possible peer systems, as well as the addresses of 100 hosts and/or networks behind them. A simplified mechanism for 101 dynamically establishing point-to-point tunnels is needed. Section 2 102 contains several use cases that motivate this effort. 104 1.1. Terminology 106 Endpoint - A device that implements IPsec for its own traffic but 107 does not act as a gateway. 109 Gateway - A network device that implements IPsec to protect traffic 110 flowing through the device. 112 Point-to-Point - Direct communication between two parties without 113 active participation (e.g. encryption or decryption) by any other 114 parties. 116 Hub - The central point in a star topology/ dynamic full mesh 117 topology, or one of the central points in the full mesh style VPN, 118 i.e. gateway where multiple other hubs or spokes connect to. The 119 hubs usually forward traffic coming from encrypted links to other 120 encrypted links, i.e. there is no devices connected to it in clear. 122 Spoke - The edge devices in the a star topology/ dynamic full mesh 123 topology, or gateway which forwards traffic from multiple cleartext 124 devices to other hubs or spokes, and some of those other devices are 125 connected to it in clear (i.e. it encrypt data coming from cleartext 126 device and forwards it to the AD VPN). 128 Star topology - This is the topology where there is direct 129 connectivity only between the hub and spoke and communication between 130 the 2 spokes happens through the hub. 132 Full Mesh topology - This is the topology where there is a direct 133 connectivity between every Spoke to every other Spoke directly, 134 without the traffic between the spokes having to be redirected 135 through an intermediate hub device. 137 Dynamic Full Mesh topology - This is the topology where direct 138 connections exist in a hub and spoke manner, but dynamic connections 139 are created/ removed between the spokes on a need basis. 141 Security Association (SA) - Defined in [RFC4301]. 143 1.2. Conventions Used in This Document 145 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 146 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 147 document are to be interpreted as described in [RFC2119]. 149 2. Use Cases 151 This section presents the key use cases for large-scale point-to- 152 point VPN. 154 In all of these use cases, the participants (endpoints and gateways) 155 may be from a single organization or from multiple organizations with 156 an established trust relationship. When multiple organizations are 157 involved, products from multiple vendors are employed so open 158 standards are needed to provide interoperability. Establishing 159 communications between participants with no established trust 160 relationship is out of scope for this effort. 162 2.1. Endpoint-to-Endpoint AD VPN Use Case 164 Two endpoints wish to communicate securely via a direct, point-to- 165 point Security Association (SA). 167 The need for secure endpoint to endpoint communications is often 168 driven by a need to employ high-bandwidth, low latency local 169 connectivity instead of using slow, expensive links to remote 170 gateways. For example, two users in close proximity may wish to 171 place a direct, secure video or voice call without needing to send 172 the call through remote gateways, which would add latency to the 173 call, consume precious remote bandwidth, and increase overall costs. 174 Such a use case also enables connectivity when both endpoints are 175 behind NAT gateways. Such use case should allow for seamless 176 connectivity even as endpoints roam, even if they are moving out from 177 behind a gateway, from behind one gateway to behind another, or from 178 a standalone position to behind a gateway. 180 In a hub and spoke topology when two endpoints communicate, they must 181 use a mechanism for authentication, such that they do not expose them 182 to impersonation by the other spoke endpoint. 184 2.2. Gateway-to-Gateway AD VPN Use Case 186 A typical Enterprise traffic model follows a star topology, with the 187 gateways connecting to each other using IPsec tunnels. 189 However for the voice and other rich media traffic that requires a 190 lot of bandwidth or is performance sensitive, the traffic tromboning 191 to the hub can create traffic bottlenecks on the hub and can lead to 192 an increase in cost. A fully meshed solution is would make best use 193 of the available network capacity and performance but the deployment 194 of a fully meshed solution involves considerable configuration, 195 especially when a large number of nodes are involved. For the 196 reasons of cost and manual error reduction, it is desired that there 197 be minimal configuration on each gateway. 199 The solution should work in cases where the endpoints are 200 administrated by separate management domains, albeit, ones that have 201 an existing trust relationship (for example two organisations who are 202 collaborating on a project, they may wish to join their networks, 203 whilst retaining independent control over configuration)It is for 204 this purpose spoke-to-spoke tunnels are dynamically created and torn- 205 down. It is highly desirable that the solution works for the star, 206 full mesh as well as dynamic full mesh topology. 208 The gateways can themselves come up and down, getting different IP 209 addresses in the process, making static configuration impossible. 211 When two gateways communicate, they must use a mechanism for 212 authentication, such that they do not expose themselves to the risk 213 of impersonation by the other entities. 215 2.3. Endpoint-to-Gateway AD VPN Use Case 217 An endpoint should be able to use the most efficient gateway as it 218 roams in the internet. 220 A mobile user roaming on the Internet may connect to a gateway, which 221 because of roaming is no longer the most efficient gateway to use 222 (reasons could be cost/ efficiency/ latency or some other factor). 223 The mobile user should be able to discover and then connect to the 224 current most efficient gateway without having to reinitiate the 225 connection. 227 3. Inadequacy of Existing Solutions 229 Several solutions exist for the problems described above. However, 230 none of these solutions is adequate, as described here. 232 3.1. Exhaustive Configuration 234 One simple solution is to configure all gateways and endpoints in 235 advance with all the information needed to determine which gateway or 236 endpoint is optimal and to establish an SA with that gateway or 237 endpoint. However, this solution does not scale in a large network 238 with hundreds of thousands of gateways and endpoints, especially when 239 multiple organizations are involved and things are rapidly changing 240 (e.g. mobile endpoints). Such a solution is also limited by the 241 smallest endpoint/ gateway, as the same exhaustive configuration is 242 to be applied on all endpoints/ gateways. A more dynamic, secure and 243 scalable system for establishing SAs between gateways is needed. 245 3.2. Star Topology 247 The most common way to address a part of this this problem today is 248 to use what has been termed a "star topology". In this case one or a 249 few gateways are defined as "hub gateways", while the rest of the 250 systems (whether endpoints or gateways) are defined as "spokes". The 251 spokes never connect to other spokes. They only open tunnels with 252 the hub gateways. Also for a large number of gateways in one 253 administrative domain, one gateway may be defined as the hub, and the 254 rest of the gateways and remote access clients connect only to that 255 gateway. 257 This solution however does not work when the spokes get dynamic IP 258 address which the "hub gateways" cannot be configured with. It is 259 also desired that there is minimal to no configuration on the hub as 260 the number of spokes increases and new spokes are added and deleted 261 randomly. 263 Another problem with the star topology is that it creates a high load 264 on the hub gateways as well as on the connection between the spokes 265 and the hub. This load is both in processing power and in network 266 bandwidth. A single packet in the hub-and-spoke scenario can be 267 encrypted and decrypted multiple times. It would be much preferable 268 if these gateways and clients could initiate tunnels between them, 269 bypassing the hub gateways. Additionally, the path bandwidth to 270 these hub gateways may be lower than that of the path between the 271 spokes. For example, two remote access users may be in the same 272 building with high-speed wifi (for example, at an IETF meeting). 273 Channeling their conversation through the hub gateways of their 274 respective employers seems extremely wasteful, as well as having 275 lower bandwidth. 277 The challenge is to build a large scale, IPsec protected networks 278 that can dynamically change with minimum administrative overhead. 280 3.3. Proprietary Approaches 282 Several vendors offer proprietary solutions to these problems. 283 However, these solutions offer no interoperability between equipment 284 from one vendor and another. This means that they are generally 285 restricted to use within one organization, and it is harder to move 286 off such solutions as the features are not standardized. Besides 287 multiple organizations cannot be expected to all choose the same 288 equipment vendor. 290 4. Requirements 292 This sectiondefines the requirements, on which the solution will be 293 based. 295 4.1. Gateway and Endpoint Requirements 297 1. For any network topology (star, full mesh and dynamic full mesh) 298 gateways and endpoints MUST minimize configuration changes when a new 299 gateway or endpoint is added, removed or changed. Adding or removing 300 a spoke in the topology MUST NOT require configuration changes to the 301 hubs other than where the spoke was connected to and SHOULD NOT 302 require configuration changes to the hub the spoke was connected to. 303 The changes also MUST NOT require configuration changes in other 304 spokes. 306 Specifically, when evaluating potential proposals, we will compare 307 them by looking at how many endpoints or gateways must be 308 reconfigured when a new gateway or endpoint is added, removed, or 309 changed and how substantial this reconfiguration is, besides the 310 amount of static configuration required. 312 This requirement is driven by use cases 2.1 and 2.2 and by the 313 scaling limitations pointed out in section 3.1. 315 2. Gateways and endpoints MUST allow IPsec Tunnels to be setup 316 without any configuration changes, even when peer addresses get 317 updated every time the device comes up. This implies that SPD 318 entries or other configuration based on peer IP address will need to 319 be automatically updated, avoided, or handled in some manner to avoid 320 a need to manually update policy whenever an address changes. 322 This requirement is driven by use cases 2.1 and 2.2 and by the 323 scaling limitations pointed out in section 3.1. 325 3. In many cases additional tunneling protocols (i.e. GRE) or 326 Routing protocols (i.e. OSPF) are run over the IPsec tunnels. 327 Gateways MUST allow for the operation of tunneling and Routing 328 protocols operating over spoke-to-spoke IPsec Tunnels with minimal or 329 no, configuration impact. Routing using the tunnels can work 330 seamlessly without any updates to the higher level application 331 configuration i.e. OSPF configuration, when the tunnel parameter 332 changes. 334 4. In the full mesh and dynamic full mesh topology, Spokes MUST 335 allow for direct communication with other spoke gateways and 336 endpoints. In the star topology mode, direct communication between 337 spokes MUST be disallowed. 339 This requirement is driven by use cases 2.1 and 2.2 and by the 340 limitations of a star topology pointed out in section 3.2. 342 5. One spoke MUST NOT be able to impersonate another spoke. 344 This requirement is driven by use case 2.1. Spokes become 345 compromised fairly often. The compromise of one Spoke should not 346 affect the security of other endpoints. 348 6. Gateways SHOULD allow for seamless handoff of sessions in case 349 endpoints are roaming, even if they cross policy boundaries. This 350 would mean the data traffic is minimally affected even as the handoff 351 happens. External factors like firewall, NAT box will not be 352 considered part of this solution. 354 This requirement is driven by use case 2.1. Today's endpoints are 355 mobile and transition often between different networks (from 4G to 356 WiFi and among various WiFi networks). 358 7. Gateways SHOULD allow for easy handoff of a session to another 359 gateway, to optimize latency, bandwidth, load balancing, 360 availability, or other factors, based on policy. 362 This requirement is driven by use case 2.3. 364 8. Gateways and endpoints MUST be able to work when they are behind 365 NAT boxes. It is especially difficult to handle cases where the Hub 366 is behind a NAT box, such a requirement MAY be supported. Where the 367 two endpoints are both behind separate NATs, communication between 368 these spokes SHOULD be supported. In the cases, workarounds MAY be 369 used such as port forwarding by the NAT or detecting when two spokes 370 are behind uncooperative NATs and using a hub in that case. 372 This requirement is driven by use cases 2.1 and 2.2. Endpoints are 373 often behind NATs and gateways sometimes are. IPsec should continue 374 to work seamlessly regardless, using AD VPN techniques whenever 375 possible and providing graceful fallback to hub and spoke techniques 376 as needed. 378 9. Changes such as establishing a new IPsec SA SHOULD be reportable 379 and manageable. However, creating a MIB or other management 380 technique is not within scope for this effort. 382 This requirement is driven by manageability concerns for all the use 383 cases, especially use case 2.2. As IPsec networks become more 384 dynamic, management tools become more essential. 386 10. To support allied and federated environments, endpoints and 387 gateways from different organizations SHOULD be able to connect to 388 each other. 390 11. The administrator of the ADVPN SHOULD allow for the 391 configuration of a Star, Full mesh or a partial full mesh topology, 392 based on which tunnels are allowed to be setup. 394 This requirement is driven by demand for all the use cases in 395 federated and allied environments. 397 12. The ADVPN solution SHOULD be able to scale for multicast 398 traffic. 400 This requirement is driven by the use case 2.2, where the amount of 401 rich media multicast traffic is increasing. 403 13. The ADVPN solution SHOULD allow for easy monitoring, logging and 404 reporting of the dynamic changes, to help for trouble shooting such 405 environments. 407 This requirement is driven by demand for all the use cases in 408 federated and allied environments. 410 14. The ADVPN solution MUST support Provider Edge (PE) based VPN's. 412 This requirement is driven by demand for all the use cases in 413 federated and allied environments. 415 5. Security Considerations 417 The solution to the problems presented in this draft may involve 418 dynamic updates to databases defined by RFC 4301, such as the 419 Security Policy Database (SPD) or the Peer Authorization Database 420 (PAD). 422 RFC 4301 is silent about the way these databases are populated, and 423 it is implied that these databases are static and pre-configured by a 424 human. Allowing dynamic updates to these databases must be thought 425 out carefully, because it allows the protocol to alter the security 426 policy that the IPsec endpoints implement. 428 One obvious attack to watch out for is stealing traffic to a 429 particular site. The IP address for www.example.com is 192.0.2.10. 430 If we add an entry to an IPsec endpoint's SPD that says that traffic 431 to 192.0.2.10 is protected through peer Gw-Mallory, then this allows 432 Gw-Mallory to either pretend to be www.example.com or to proxy and 433 read all traffic to that site. Updates to this database requires a 434 clear trust model. 436 More to be added. 438 6. IANA Considerations 440 No actions are required from IANA for this informational document. 442 7. Acknowledgements 444 Many people have contributed to the development of this problem 445 statement and many more will probably do so before we are done with 446 it. While we cannot thank all contributors, some have played an 447 especially prominent role. Yoav Nir, Yaron Scheffer, Jorge Coronel 448 Mendoza, Chris Ulliott, and John Veizades wrote the document upon 449 which this draft was based. Geoffrey Huang, Suresh Melam, Praveen 450 Sathyanarayan, Andreas Steffen, and Brian Weis provided essential 451 input. 453 8. Normative References 455 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 456 Requirement Levels", BCP 14, RFC 2119, March 1997. 458 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 459 Internet Protocol", RFC 4301, December 2005. 461 Authors' Addresses 463 Steve Hanna 464 Juniper Networks, Inc. 465 1194 N. Mathilda Ave. 466 Sunnyvale, CA 94089 467 USA 469 Email: shanna@juniper.net 471 Vishwas Manral 472 Hewlett-Packard Co. 473 19111 Pruneridge Ave. 474 Cupertino, CA 95113 475 USA 477 Email: vishwas.manral@hp.com