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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 4, 2013) is 3849 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'RFC2119' is defined on line 441, but no explicit reference was found in the text Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Quinn 3 Internet-Draft J. Guichard 4 Intended status: Informational S. Kumar 5 Expires: April 7, 2014 Cisco Systems, Inc. 6 P. Agarwal 7 R. Manur 8 Broadcom 9 A. Chauhan 10 Citrix 11 N. Leymann 12 Deutsche Telekom 13 M. Boucadair 14 C. Jacquenet 15 France Telecom 16 M. Smith 17 N. Yadav 18 Insieme Networks 19 T. Nadeau 20 K. Gray 21 Juniper Networks 22 B. McConnell 23 Rackspace 24 K. Glavin 25 Riverbed 26 October 4, 2013 28 Service Function Chaining Problem Statement 29 draft-quinn-sfc-problem-statement-00.txt 31 Abstract 33 This document provides an overview of the issues associated with the 34 deployment of services functions (such as firewalls, load balancers) 35 in large-scale environments. The term service function chaining is 36 used to describe the deployment of such service functions, and the 37 ability of a network operator to specify an ordered list of service 38 functions that should be applied to a deterministic set of traffic 39 flows. Such service function chains require integration of service 40 policy alongside the deployment of applications, while allowing for 41 the optimal utilization of network resources. 43 Status of this Memo 45 This Internet-Draft is submitted in full conformance with the 46 provisions of BCP 78 and BCP 79. 48 Internet-Drafts are working documents of the Internet Engineering 49 Task Force (IETF). Note that other groups may also distribute 50 working documents as Internet-Drafts. The list of current Internet- 51 Drafts is at http://datatracker.ietf.org/drafts/current/. 53 Internet-Drafts are draft documents valid for a maximum of six months 54 and may be updated, replaced, or obsoleted by other documents at any 55 time. It is inappropriate to use Internet-Drafts as reference 56 material or to cite them other than as "work in progress." 58 This Internet-Draft will expire on April 7, 2014. 60 Copyright Notice 62 Copyright (c) 2013 IETF Trust and the persons identified as the 63 document authors. All rights reserved. 65 This document is subject to BCP 78 and the IETF Trust's Legal 66 Provisions Relating to IETF Documents 67 (http://trustee.ietf.org/license-info) in effect on the date of 68 publication of this document. Please review these documents 69 carefully, as they describe your rights and restrictions with respect 70 to this document. Code Components extracted from this document must 71 include Simplified BSD License text as described in Section 4.e of 72 the Trust Legal Provisions and are provided without warranty as 73 described in the Simplified BSD License. 75 Table of Contents 77 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 78 1.1. Definition of Terms . . . . . . . . . . . . . . . . . . . 4 79 2. Problem Areas . . . . . . . . . . . . . . . . . . . . . . . . 6 80 3. Service Function Chaining . . . . . . . . . . . . . . . . . . 9 81 4. Service Function Chaining Use Cases . . . . . . . . . . . . . 11 82 4.1. Enterprise Data Center Service Chaining . . . . . . . . . 11 83 4.2. Mobility Service Chaining . . . . . . . . . . . . . . . . 11 84 5. Related IETF Work . . . . . . . . . . . . . . . . . . . . . . 12 85 6. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 86 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 87 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 88 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 89 9.1. Normative References . . . . . . . . . . . . . . . . . . . 16 90 9.2. Informative References . . . . . . . . . . . . . . . . . . 16 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 93 1. Introduction 95 Services that are composed of service functions require more flexible 96 service function deployment models than those typically available in 97 networks today. Such services may utilize traditional network 98 service functions (for example firewalls and server load balancers), 99 as well as higher layer applications and features. Services may be 100 delivered within a specific context so that isolated user groups 101 attached to a common network may be formed. Such user groups may 102 require unique capabilities with the ability to tailor service 103 characteristics on a per-tenant/per-subscriber/per-VPN basis that 104 must not affect other user groups 106 Current service function deployment models are relatively static in 107 that they are bound to fixed network topologies and resources. At 108 present, these deployments are not easily manipulated (i.e.: moved, 109 created or destroyed) even when virtualized elements are deployed. 110 This poses a problem in highly elastic service environments that 111 require relatively rapid creation, destruction or movement of real or 112 virtual service functions or network elements. Additionally, the 113 transition to virtual platforms requires an agile service insertion 114 model that supports elastic and very granular service delivery, and 115 post-facto modification; supports the movement of service functions 116 and application workloads in the existing network, all the while 117 retaining the network and service policies and the ability to easily 118 bind service policy to granular information such as per-subscriber 119 state. 121 This document outlines the problems encountered with existing service 122 deployment models for service function chaining (often referred to 123 simply as service chaining; in this document the terms will be used 124 interchangeably), as well as the problems of service chain creation/ 125 deletion, policy integration with service chains, and policy 126 enforcement within the network infrastructure. 128 1.1. Definition of Terms 130 Classification: Locally instantiated policy and customer/network/ 131 service profile matching of traffic flows for identification of 132 appropriate outbound forwarding actions. 134 Network Overlay: Logical network built on top of existing network 135 (the underlay). Packets are encapsulated or tunneled to create 136 the overlay network topology. 138 Service Chain: A service chain defines the required functions and 139 associated order (service-function1 --> service-function 2) that 140 must be applied to packets and/or frames. A service chain does 141 not specify the network location or specific instance of service 142 functions (e.g. firewall1 vs. firewall2). 144 Service Function: A network or application based packet treatment, 145 application, compute or storage resource, used singularly or in 146 concert with other service functions within a service chain to 147 enable a service offered by a network operator. 149 A non-exhaustive list of Service Functions includes: firewalls, 150 WAN and application acceleration, Deep Packet Inspection (DPI), 151 server load balancers, NAT44 [RFC3022], NAT64 [RFC6146], HOST_ID 152 injection, HTTP Header Enrichment functions, TCP optimizer, etc. 154 The generic term "L4-L7 services" is often used to describe many 155 service functions. 157 Service Node: Physical or virtual element providing one or more 158 service functions. 160 Network Service: An externally visible service offered by a network 161 operator; a service may consist of a single service function or a 162 composite built from several service functions executed in one or 163 more pre-determined sequences and delivered by one or more service 164 nodes. 166 2. Problem Areas 168 The following points describe aspects of existing service deployment 169 that are problematic, and are being addressed by the network service 170 chaining effort. 172 1. Topological Dependencies: Network service deployments are often 173 coupled to the physical network topology creating constraints on 174 service delivery and potentially inhibiting the network operator 175 from optimally utilizing service resources. This limits scale, 176 capacity, and redundancy across network resources. 178 These topologies serve only to "insert" the service function 179 (i.e. ensure that traffic traverse a service function); they are 180 not required from a native packet delivery perspective. For 181 example, firewalls often require an "in" and "out" layer-2 182 segment and adding a new firewall requires changing the topology 183 (i.e. adding new L2 segments). 185 As more service functions are required - often with strict 186 ordering - topology changes are needed before and after each 187 service function resulting in complex network changes and device 188 configuration. In such topologies, all traffic, whether a 189 service function needs to be applied or not, often passes 190 through the same strict order. 192 A common example is web servers using a server load balancer as 193 the default gateway. When the web service responds to non-load 194 balanced traffic (e.g. administrative or backup operations) all 195 traffic from the server must traverse the load balancer forcing 196 network administrators to create complex routing schemes or 197 create additional interfaces to provide an alternate topology. 199 2. Configuration complexity: A direct consequence of topological 200 dependencies is the complexity of the entire configuration, 201 specifically in deploying service chains. Simple actions such 202 as changing the order of the service functions in a service 203 chain require changes to the topology. Changes to the topology 204 are avoided by the network operator once installed, configured 205 and deployed in production environments fearing misconfiguration 206 and downtime. All of this leads to very static service delivery 207 models. Furthermore, the speed at which these topological 208 changes can be made is not rapid or dynamic enough as it often 209 requires manual intervention, or use of slow provisioning 210 systems. 212 The service itself can contribute to complexity: it may require 213 an intricate combination of very different capabilities, 214 regardless of the underlying topology. QoS-based, resilient VPN 215 service offerings are a typical example of such complexity. 217 3. Constrained High Availability: An effect of topological 218 dependency is constrained service function high availability. 219 Worse, when modified, inadvertent non-high availability can 220 result. 222 Since traffic reaches service functions based on network 223 topology, alternate, or redundant service functions must be 224 placed in the same topology as the primary service. 226 4. Consistent Ordering of Service Functions: Service functions are 227 typically independent; service function_1 (SF1)...service 228 function_n (SFn) are unrelated and there is no notion at the 229 service layer that SF1 occurs before SF2. However, to an 230 administrator many service functions have a strict ordering that 231 must be in place, yet the administrator has no consistent way to 232 impose and verify the ordering of the functions that used to 233 deliver a given service. 235 5. Service Chain Construction: Service chains today are most 236 typically built through manual configuration processes. These 237 are slow and error prone. With the advent of newer service 238 deployment models the control / management planes will provide 239 not only connectivity state, but will also be increasingly 240 utilized for the formation of services. Such a control / 241 management plane could be centrally controlled and managed, or 242 be distributed between a subset of end-systems. 244 6. Application of Service Policy: Service functions rely on 245 topology information such as VLANs or packet (re) classification 246 to determine service policy selection, i.e. the service function 247 specific action taken. Topology information is increasingly 248 less viable due to scaling, tenancy and complexity reasons. The 249 topological information is often stale, providing the operator 250 with inaccurate placement that can result in suboptimal resource 251 utilization. Per-service function packet classification is 252 inefficient and prone to errors, duplicating functionality 253 across service functions. Furthermore packet classification is 254 often too coarse lacking the ability to determine class of 255 traffic with enough detail. 257 7. Transport Dependence: Service functions can and will be deployed 258 in networks with a range of transports, including under and 259 overlays. The coupling of service functions to topology 260 requires service functions to support many transports or for a 261 transport gateway function to be present. 263 8. Elastic Service Delivery: Given the current state of the art for 264 adding/removing service functions largely centers around VLANs 265 and routing changes, rapid changes to the service layer can be 266 hard to realize due to the risk and complexity of such changes. 268 9. Traffic Selection Criteria: Traffic selection is coarse, that 269 is, all traffic on a particular segment traverse service 270 functions whether the traffic requires service enforcement or 271 not. This lack of traffic selection is largely due to the 272 topological nature of service deployment since the forwarding 273 topology dictates how (and what) data traverses service 274 function(s). In some deployments, more granular traffic 275 selection is achieved using policy routing or access control 276 filtering. This results in operationally complex configurations 277 and is still relatively inflexible. 279 10. Limited End-to-End Service Visibility: Troubleshooting service 280 related issues is a complex process that involve network and 281 service expertise. This is especially the case when service 282 chains span multiple DCs, or across administrative boundaries 283 such as externally consumable service chain components. 284 Furthermore, the physical and virtual environments (network and 285 service), can be highly divergent in terms of topology and that 286 topological variance adds to these challenges. 288 11. Per-Service (re)Classification: Classification occurs at each 289 service, independent from previously applied service functions. 290 These unrelated classification events consume resources per 291 service. More importantly, the classification functionality 292 often differs per service function and service function cannot 293 leverage the results from other deployed network or service. 295 12. Symmetric Traffic Flows: Service chains may be unidirectional or 296 bidirectional; unidirectional is one where traffic is passed 297 through a set of service functions in one forwarding direction 298 only. Bidirectional is one where traffic is passed through a 299 set of service functions in both forwarding directions. 300 Existing service deployment models provide a static approach to 301 realizing forward and reverse service chain association most 302 often requiring complex configuration of each network device 303 throughout the forwarding path. 305 13. Multi-vendor Service Functions: Deploying service functions from 306 multiple vendors often requires per-vendor expertise: insertion 307 models differ, there are limited common attributes and inter- 308 vendor service functions do not share information. 310 3. Service Function Chaining 312 Service chaining provides a framework to address the aforementioned 313 problems associated with service deployments: 315 1. Service Overlay: Service chaining utilizes a service specific 316 overlay that creates the service topology: the overlay creates a 317 path between service nodes. The service overlay is independent 318 of the network topology and allows operators to use whatever 319 overlay or underlay they prefer and to locate service functions 320 in the network as needed. 322 Within the service topology, service functions can be viewed as 323 resources for consumption and an arbitrary topology constructed 324 to connect those resources in a required order. Adding new 325 service functions to the topology is easily accomplished, and no 326 underlying network changes are required. Furthermore, additional 327 service instances, for redundancy or load distribution, can be 328 added or removed to the service topology as required. 330 Lastly, the service overlay can provide service specific 331 information needed for troubleshooting service-related issues. 333 2. Generic Service Control Plane (GSCP): GSCP provides information 334 about the available service functions on a network. The 335 information provided by the control plane includes service 336 network location (for topology creation), service type (e.g. 337 firewall, load balancer, etc.) and, optionally, administrative 338 information about the service functions such as load, capacity 339 and operating status. GSCP allows for the formulation of service 340 chains and disseminates the service chains to the network. 342 3. Service Classification: Classification is used to select which 343 traffic enters a service overlay. The granularity of the 344 classification varies based on device capabilities, customer 345 requirements, and service functionality. Initial classification 346 is used to start the service chain. Subsequent classification 347 can be used within a given service chain to alter the sequence of 348 service functions applied. Symmetric classification ensures that 349 forward and reverse chains are in place. 351 4. Dataplane Metadata: Dataplane metadata provides the ability to 352 exchange information between the network and service functions, 353 service functions and service functions and service functions and 354 the network. Metadata can include the result of antecedent 355 classification, information from external sources or forwarding 356 related data. For example, service functions utilize metadata, 357 as required, for localized policy decision. A common approach to 358 service metadata creates a common foundation for interoperability 359 between service functions, regardless of vendor. 361 4. Service Function Chaining Use Cases 363 The following sections provide high level overviews of several common 364 service chaining deployments. 366 4.1. Enterprise Data Center Service Chaining 368 TBD 370 4.2. Mobility Service Chaining 372 TBD 374 5. Related IETF Work 376 The following subsections discuss related IETF work and are provided 377 for reference. This section is not exhaustive, rather it provides an 378 overview of the various initiatives and how they relate to network 379 service chaining. 381 1. L3VPN[L3VPN]: The L3VPN working group is responsible for 382 defining, specifying and extending BGP/MPLS IP VPNs solutions. 383 Although BGP/MPLS IP VPNs can be used as transport for service 384 chaining deployments, the service chaining WG focuses on the 385 service specific protocols, not the general case of VPNs. 386 Furthermore, BGP/MPLS IP VPNs do not address the requirements for 387 service chaining. 389 2. LISP[LISP]: LISP provides locator and ID separation. LISP can be 390 used as an L3 overlay to transport service chaining data but does 391 not address the specific service chaining problems highlighted in 392 this document. 394 3. NVO3[NVO3]: The NVO3 working group is chartered with creation of 395 problem statement and requirements documents for multi-tenant 396 network overlays. NVO3 WG does not address service chaining 397 protocols. 399 4. ALTO[ALTO]: The Application Layer Traffic Optimization Working 400 Group is chartered to provide topological information at a higher 401 abstraction layer, which can be based upon network policy, and 402 with application-relevant service functions located in it. The 403 mechanism for ALTO obtaining the topology can vary and policy can 404 apply to what is provided or abstracted. This work could be 405 leveraged and extended to address the need for services 406 discovery. 408 5. I2RS[I2RS]: The Interface to the Routing System Working Group is 409 chartered to investigate the rapid programming of a device's 410 routing system, as well as the service of a generalized, multi- 411 layered network topology. This work could be leveraged and 412 extended to address some of the needs for service chaining in the 413 topology and device programming areas. 415 6. Summary 417 This document highlights problems associated with network service 418 deployment today and identifies several key areas that will be 419 addressed by the service chaining working group. Furthermore, this 420 document identifies four components that are the basis for serice 421 chaining. These components will form the areas of focus for the 422 working group. 424 7. Security Considerations 426 Security considerations are not addressed in this problem statement 427 only document. Given the scope of service chaining, and the 428 implications on data and control planes, security considerations are 429 clearly important and will be addressed in the specific protocol and 430 deployment documents created by the service chaining working group. 432 8. Acknowledgments 434 The authors would like to thank David Ward, Rex Fernando and Jim 435 French for their contributions. 437 9. References 439 9.1. Normative References 441 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 442 Requirement Levels", BCP 14, RFC 2119, March 1997. 444 9.2. Informative References 446 [ALTO] "Application-Layer Traffic Optimization (alto)", 447 . 449 [I2RS] "Interface to the Routing System (i2rs)", 450 . 452 [L3VPN] "Layer 3 Virtual Private Networks (l3vpn)", 453 . 455 [LISP] "Locator/ID Separation Protocol (lisp)", 456 . 458 [NVO3] "Network Virtualization Overlays (nvo3)", 459 . 461 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 462 Address Translator (Traditional NAT)", RFC 3022, 463 January 2001. 465 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful 466 NAT64: Network Address and Protocol Translation from IPv6 467 Clients to IPv4 Servers", RFC 6146, April 2011. 469 Authors' Addresses 471 Paul Quinn 472 Cisco Systems, Inc. 474 Email: paulq@cisco.com 476 Jim Guichard 477 Cisco Systems, Inc. 479 Email: jguichar@cisco.com 481 Surendra Kumar 482 Cisco Systems, Inc. 484 Email: smkumar@cisco.com 486 Puneet Agarwal 487 Broadcom 489 Email: pagarwal@broadcom.com 491 Rajeev Manur 492 Broadcom 494 Email: rmanur@broadcom.com 496 Abhishek Chauhan 497 Citrix 499 Email: Abhishek.Chauhan@citrix.com 501 Nic Leymann 502 Deutsche Telekom 504 Email: n.leymann@telekom.de 505 Mohamed Boucadair 506 France Telecom 508 Email: mohamed.boucadair@orange.com 510 Christian Jacquenet 511 France Telecom 513 Email: christian.jacquenet@orange.com 515 Michael Smith 516 Insieme Networks 518 Email: michsmit@insiemenetworks.com 520 Navindra Yadav 521 Insieme Networks 523 Email: nyadav@insiemenetworks.com 525 Thomas Nadeau 526 Juniper Networks 528 Email: tnadeau@juniper.net 530 Ken Gray 531 Juniper Networks 533 Email: kgray@juniper.net 535 Brad McConnell 536 Rackspace 538 Email: bmcconne@rackspace.com 540 Kevin Glavin 541 Riverbed 543 Email: Kevin.Glavin@riverbed.com