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Manral 5 Expires: December 05, 2013 HP 6 June 03, 2013 8 Auto Discovery VPN Problem Statement and Requirements 9 draft-ietf-ipsecme-ad-vpn-problem-07 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 will 22 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 December 05, 2013. 41 Copyright Notice 43 Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 59 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 60 1.2. Conventions Used in This Document . . . . . . . . . . . . 4 61 2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4 62 2.1. Endpoint-to-Endpoint ADVPN Use Case . . . . . . . . . . . 4 63 2.2. Gateway-to-Gateway ADVPN Use Case . . . . . . . . . . . . 5 64 2.3. Endpoint-to-Gateway ADVPN Use Case . . . . . . . . . . . 5 65 3. Inadequacy of Existing Solutions . . . . . . . . . . . . . . 6 66 3.1. Exhaustive Configuration . . . . . . . . . . . . . . . . 6 67 3.2. Star Topology . . . . . . . . . . . . . . . . . . . . . . 6 68 3.3. Proprietary Approaches . . . . . . . . . . . . . . . . . 7 69 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7 70 4.1. Gateway and Endpoint Requirements . . . . . . . . . . . . 7 71 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 72 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 73 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 74 8. Normative References . . . . . . . . . . . . . . . . . . . . 11 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 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 ADVPN - Auto Discovery Virtual Private Network (ADVPN) is VPN 107 solution that enables a large number of systems to communicate 108 directly, with minimal configuration and operator intervention using 109 IPsec to protect communication between them. 111 Endpoint - A device that implements IPsec for its own traffic but 112 does not act as a gateway. 114 Gateway - A network device that implements IPsec to protect traffic 115 flowing through the device. 117 Point-to-Point - Communication between two parties without active 118 participation (e.g. encryption or decryption) by any other parties. 120 Hub - The central point in a star topology/ dynamic full mesh 121 topology, or one of the central points in the full mesh style VPN, 122 i.e. gateway where multiple other hubs or spokes connect to. The 123 hubs usually forward traffic coming from encrypted links to other 124 encrypted links, i.e. there are no devices connected to it in clear. 126 Spoke - The endpoint in a star topology/ dynamic full mesh topology, 127 or gateway which forwards traffic from multiple cleartext devices to 128 other hubs or spokes, and some of those other devices are connected 129 to it in clear (i.e. it encrypts data coming from cleartext devices 130 and forwards it to the ADVPN). 132 ADVPN Peer - any member of an ADVPN including gateways, endpoints, 133 hub or spoke. 135 Star topology - This is the topology where there is direct 136 connectivity only between the hub and spoke and communication between 137 the 2 spokes happens through the hub. 139 Allied and Federated Environments - Environments where we have 140 multiple different organizations that have close association and need 141 to connect to each other. 143 Full Mesh topology - This is the topology where there is a direct 144 connectivity between every Spoke to every other Spoke directly, 145 without the traffic between the spokes having to be redirected 146 through an intermediate hub device. 148 Dynamic Full Mesh topology - This is the topology where direct 149 connections exist in a hub and spoke manner, but dynamic connections 150 are created/ removed between the spokes on a need basis. 152 Security Association (SA) - Defined in [RFC4301]. 154 1.2. Conventions Used in This Document 156 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 157 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 158 document are to be interpreted as described in [RFC2119]. 160 2. Use Cases 162 This section presents the key use cases for large-scale point-to- 163 point VPN. 165 In all of these use cases, the participants (endpoints and gateways) 166 may be from a single organization (administrative domain) or from 167 multiple organizations with an established trust relationship. When 168 multiple organizations are involved, products from multiple vendors 169 are employed so open standards are needed to provide 170 interoperability. Establishing communications between participants 171 with no established trust relationship is out of scope for this 172 effort. 174 2.1. Endpoint-to-Endpoint ADVPN Use Case 176 Two endpoints wish to communicate securely via a point-to-point 177 Security Association (SA). 179 The need for secure endpoint to endpoint communications is often 180 driven by a need to employ high-bandwidth, low latency local 181 connectivity instead of using slow, expensive links to remote 182 gateways. For example, two users in close proximity may wish to 183 place a direct, secure video or voice call without needing to send 184 the call through remote gateways, which would add latency to the 185 call, consume precious remote bandwidth, and increase overall costs. 186 Such a use case also enables connectivity when both behind NAT 187 gateways. Such a use case ought to allow for seamless connectivity 188 even as endpoints roam, even if they are moving out from behind a NAT 189 gateway, from behind one NAT gateway to behind another, or from a 190 standalone position to behind a NAT gateway. 192 In a star topology when two endpoints communicate, they need a 193 mechanism for authentication, such that they do not expose themselves 194 to impersonation by the other spoke endpoint. 196 2.2. Gateway-to-Gateway ADVPN Use Case 198 A typical Enterprise traffic model follows a star topology, with the 199 gateways connecting to each other using IPsec tunnels. 201 However for voice and other rich media traffic that requires a lot of 202 bandwidth or is performance sensitive, the traffic tromboning to the 203 hub can create traffic bottlenecks on the hub and can lead to an 204 increase in cost. A fully meshed solution would make best use of the 205 available network capacity and performance but the deployment of a 206 fully meshed solution involves considerable configuration, especially 207 when a large number of nodes are involved. It is for this purpose 208 spoke-to-spoke tunnels are dynamically created and torn-down. For 209 the reasons of cost and manual error reduction, it is desired that 210 there be minimal configuration on each gateway. 212 The solution ought to work in cases where the endpoints are in 213 different administrative domains, albeit, ones that have an existing 214 trust relationship (for example two organisations who are 215 collaborating on a project, they may wish to join their networks, 216 whilst retaining independent control over configuration). It is 217 highly desirable that the solution works for the star, full mesh as 218 well as dynamic full mesh topology. 220 The solution ought to also address the case where gateways use 221 dynamic IP addresses. 223 Additionally, the routing implications of gateway-to-gateway 224 communication need to be addressed. In the simple case, selectors 225 provide sufficient information for a gateway to forward traffic 226 appropriately. In other cases, additional tunneling (e.g., Generic 227 Routing Encapsulation - GRE) and routing (e.g., Open Shortest Path 228 First - OSPF) protocols are run over IPsec tunnels, and the 229 configuration impact on those protocols needs to be considered. 230 There is also the case when Layer-3 Virtual Private Networks (L3VPNs) 231 operate over IPsec Tunnels. 233 When two gateways communicate, they need to use a mechanism for 234 authentication, such that they do not expose themselves to the risk 235 of impersonation by the other entities. 237 2.3. Endpoint-to-Gateway ADVPN Use Case 238 An endpoint ought to be able to use the most efficient gateway as it 239 roams in the internet. 241 A mobile user roaming on the Internet may connect to a gateway, which 242 because of roaming is no longer the most efficient gateway to use 243 (reasons could be cost/ efficiency/ latency or some other factor). 244 The mobile user ought to be able to discover and then connect to the 245 current most efficient gateway without having to reinitiate the 246 connection. 248 3. Inadequacy of Existing Solutions 250 Several solutions exist for the problems described above. However, 251 none of these solutions is adequate, as described here. 253 3.1. Exhaustive Configuration 255 One simple solution is to configure all gateways and endpoints in 256 advance with all the information needed to determine which gateway or 257 endpoint is optimal and to establish an SA with that gateway or 258 endpoint. However, this solution does not scale in a large network 259 with hundreds of thousands of gateways and endpoints, especially when 260 multiple administrative domains are involved and things are rapidly 261 changing (e.g. mobile endpoints). Such a solution is also limited 262 by the smallest endpoint/ gateway, as the same exhaustive 263 configuration is to be applied on all endpoints/ gateways. A more 264 dynamic, secure and scalable system for establishing SAs between 265 gateways is needed. 267 3.2. Star Topology 269 The most common way to address a part of this this problem today is 270 to use what has been termed a "star topology". In this case one or a 271 few gateways are defined as "hub gateways", while the rest of the 272 systems (whether endpoints or gateways) are defined as "spokes". The 273 spokes never connect to other spokes. They only open tunnels with 274 the hub gateways. Also for a large number of gateways in one 275 administrative domain, one gateway may be defined as the hub, and the 276 rest of the gateways and remote access clients connect only to that 277 gateway. 279 This solution however is complicated by the case when the spokes use 280 dynamic IP addresses and DNS with dynamic updates needs to be used. 281 It is also desired that there is minimal to no configuration on the 282 hub as the number of spokes increases and new spokes are added and 283 deleted randomly. 285 Another problem with the star topology is that it creates a high load 286 on the hub gateways as well as on the connection between the spokes 287 and the hub. This load is both in processing power and in network 288 bandwidth. A single packet in the hub-and-spoke scenario can be 289 encrypted and decrypted multiple times. It would be much preferable 290 if these gateways and clients could initiate tunnels between them, 291 bypassing the hub gateways. Additionally, the path bandwidth to 292 these hub gateways may be lower than that of the path between the 293 spokes. For example, two remote access users may be in the same 294 building with high-speed wifi (for example, at an IETF meeting). 295 Channeling their conversation through the hub gateways of their 296 respective employers seems extremely wasteful, as well as having 297 lower bandwidth. 299 The challenge is to build a large scale, IPsec protected networks 300 that can dynamically change with minimum administrative overhead. 302 3.3. Proprietary Approaches 304 Several vendors offer proprietary solutions to these problems. 305 However, these solutions offer no interoperability between equipment 306 from one vendor and another. This means that they are generally 307 restricted to use within one organization, and it is harder to move 308 off such solutions as the features are not standardized. Besides 309 multiple organizations cannot be expected to all choose the same 310 equipment vendor. 312 4. Requirements 314 This section defines the requirements, on which the solution will be 315 based. 317 4.1. Gateway and Endpoint Requirements 319 1. For any network topology (star, full mesh and dynamic full mesh) 320 gateways and endpoints SHOULD minimize configuration changes when a 321 new gateway or endpoint is added, removed or changed. Adding or 322 removing a spoke in the topology MUST NOT require configuration 323 changes to the hubs other than where the spoke was connected to and 324 SHOULD NOT require configuration changes to the hub the spoke was 325 connected to. The changes also MUST NOT require configuration 326 changes in other spokes. 328 Specifically, when evaluating potential proposals, we will compare 329 them by looking at how many endpoints or gateways must be 330 reconfigured when a new gateway or endpoint is added, removed, or 331 changed and how substantial this reconfiguration is, besides the 332 amount of static configuration required. 334 This requirement is driven by use cases 2.1 and 2.2 and by the 335 scaling limitations pointed out in section 3.1. 337 2. ADVPN peers MUST allow IPsec Tunnels to be setup with other 338 members of the ADVPN without any configuration changes, even when 339 peer addresses get updated every time the device comes up. This 340 implies that SPD entries or other configuration based on peer IP 341 address will need to be automatically updated, avoided, or handled in 342 some manner to avoid a need to manually update policy whenever an 343 address changes. 345 3. In many cases additional tunneling protocols (e.g. GRE) or 346 Routing protocols (e.g. OSPF) are run over the IPsec tunnels. 347 Gateways MUST allow for the operation of tunneling and Routing 348 protocols operating over spoke-to-spoke IPsec Tunnels with minimal or 349 no, configuration impact. The ADVPN solution SHOULD NOT increase the 350 amount of information required to configure protocols running over 351 IPsec tunnels. 353 4. In the full mesh and dynamic full mesh topology, Spokes MUST 354 allow for direct communication with other spoke gateways and 355 endpoints. In the star topology mode, direct communication between 356 spokes MUST be disallowed. 358 This requirement is driven by use cases 2.1 and 2.2 and by the 359 limitations of a star topology pointed out in section 3.2. 361 5. Any of the ADVPN Peers MUST NOT have a way to get the long term 362 authentication credentials for any other ADVPN Peers. The compromise 363 of an Endpoint MUST NOT affect the security of communications between 364 other ADVPN Peers. The compromise of a Gateway SHOULD NOT affect the 365 security of the communications between ADVPN Peers not associated 366 with that Gateway. 368 This requirement is driven by use case 2.1. ADVPN Peers (especially 369 Spokes) become compromised fairly often. The compromise of one ADVPN 370 Peer SHOULD NOT affect the security of other unrelated ADVPN Peers. 372 6. Gateways SHOULD allow for seamless handoff of sessions in case 373 endpoints are roaming, even if they cross policy boundaries. This 374 would mean the data traffic is minimally affected even as the handoff 375 happens. External factors like firewall, NAT boxes will not be 376 considered part of this solution. 378 Such endpoint roaming may affect not only the endpoint-to-endpoint SA 379 but also the relationship between the endpoints and gateways (such as 380 when an endpoint roams to a new network that is handled by a 381 different gateway). 383 This requirement is driven by use case 2.1. Today's endpoints are 384 mobile and transition often between different networks (from 4G to 385 WiFi and among various WiFi networks). 387 7. Gateways SHOULD allow for easy handoff of a session to another 388 gateway, to optimize latency, bandwidth, load balancing, 389 availability, or other factors, based on policy. 391 This ability to migrate traffic from one gateway to another applies 392 regardless of whether the gateways in question are hubs or spokes. 393 It even applies in the case where a gateway (hub or spoke) moves in 394 the network, as may happen with a vehicle-based network. 396 This requirement is driven by use case 2.3. 398 8. Gateways and endpoints MUST have the capability to participate in 399 an ADVPN even when they are located behind NAT boxes. However, in 400 some cases they may be deployed in such a way that they will not be 401 fully reachable behind a NAT box. It is especially difficult to 402 handle cases where the Hub is behind a NAT box. Where the two 403 endpoints are both behind separate NATs, communication between these 404 spokes SHOULD be supported using workarounds such as port forwarding 405 by the NAT or detecting when two spokes are behind uncooperative NATs 406 and using a hub in that case. 408 This requirement is driven by use cases 2.1 and 2.2. Endpoints are 409 often behind NATs and gateways sometimes are. IPsec SHOULD continue 410 to work seamlessly regardless, using ADVPN techniques whenever 411 possible and providing graceful fallback to hub and spoke techniques 412 as needed. 414 9. Changes such as establishing a new IPsec SA SHOULD be reportable 415 and manageable. However, creating a MIB or other management 416 technique is not within scope for this effort. 418 This requirement is driven by manageability concerns for all the use 419 cases, especially use case 2.2. As IPsec networks become more 420 dynamic, management tools become more essential. 422 10. To support allied and federated environments, endpoints and 423 gateways from different organizations SHOULD be able to connect to 424 each other. 426 This requirement is driven by demand for all the use cases in 427 federated and allied environments. 429 11. The administrator of the ADVPN SHOULD allow for the 430 configuration of a Star, Full mesh or a partial full mesh topology, 431 based on which tunnels are allowed to be setup. 433 This requirement is driven by demand for all the use cases in 434 federated and allied environments. 436 12. The ADVPN solution SHOULD be able to scale for multicast 437 traffic. 439 This requirement is driven by the use case 2.2, where the amount of 440 rich media multicast traffic is increasing. 442 13. The ADVPN solution SHOULD allow for easy monitoring, logging and 443 reporting of the dynamic changes, to help for trouble shooting such 444 environments. 446 This requirement is driven by demand for all the use cases in 447 federated and allied environments. 449 14. There is also the case when L3VPNs operate over IPsec Tunnels, 450 for example Provider Edge (PE) based VPN's. An ADVPN MUST support 451 L3VPN as an application protected by the IPsec Tunnels. 453 This requirement is driven by demand for all the use cases in 454 federated and allied environments. 456 15. There ADVPN solution SHOULD allow the enforcement of per peer 457 QoS in both the Star as well as the Full Mesh topology. 459 This requirement is driven by demand for all the use cases in 460 federated and allied environments. 462 5. Security Considerations 464 This is a Problem statement and requirement document for the ADVPN 465 solution, and in itself does not introduce any new security concerns. 466 The solution to the problems presented in this draft may involve 467 dynamic updates to databases defined by RFC 4301, such as the 468 Security Policy Database (SPD) or the Peer Authorization Database 469 (PAD). 471 RFC 4301 is silent about the way these databases are populated, and 472 it is implied that these databases are static and pre-configured by a 473 human. Allowing dynamic updates to these databases must be thought 474 out carefully, because it allows the protocol to alter the security 475 policy that the IPsec endpoints implement. 477 One obvious attack to watch out for is stealing traffic to a 478 particular site. The IP address for www.example.com is 192.0.2.10. 479 If we add an entry to an IPsec endpoint's SPD that says that traffic 480 to 192.0.2.10 is protected through peer Gw-Mallory, then this allows 481 Gw-Mallory to either pretend to be www.example.com or to proxy and 482 read all traffic to that site. Updates to this database requires a 483 clear trust model. 485 6. IANA Considerations 487 No actions are required from IANA for this informational document. 489 7. Acknowledgements 491 Many people have contributed to the development of this problem 492 statement and many more will probably do so before we are done with 493 it. While we cannot thank all contributors, some have played an 494 especially prominent role. Yoav Nir, Yaron Sheffer, Jorge Coronel 495 Mendoza, Chris Ulliott, and John Veizades wrote the document upon 496 which this draft was based. Geoffrey Huang, Suresh Melam, Praveen 497 Sathyanarayan, Andreas Steffen, Brian Weis, and Lou Berger provided 498 essential input. 500 8. Normative References 502 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 503 Requirement Levels", BCP 14, RFC 2119, March 1997. 505 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 506 Internet Protocol", RFC 4301, December 2005. 508 Authors' Addresses 510 Steve Hanna 511 Juniper Networks, Inc. 512 1194 N. Mathilda Ave. 513 Sunnyvale, CA 94089 514 USA 516 Email: shanna@juniper.net 517 Vishwas Manral 518 Hewlett-Packard Co. 519 19111 Pruneridge Ave. 520 Cupertino, CA 95113 521 USA 523 Email: vishwas.manral@hp.com