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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 (July 13, 2013) is 3933 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'RFC2119' is defined on line 399, 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: January 14, 2014 Cisco Systems, Inc. 6 A. Chauhan 7 Citrix 8 N. Leymann 9 Deutsche Telekom 10 M. Boucadair 11 C. Jacquenet 12 France Telecom 13 M. Smith 14 N. Yadav 15 Insieme Networks 16 T. Nadeau 17 K. Gray 18 Juniper Networks 19 B. McConnell 20 Rackspace 21 July 13, 2013 23 Network Service Chaining Problem Statement 24 draft-quinn-nsc-problem-statement-01.txt 26 Abstract 28 This document provides an overview of the issues associated with the 29 deployment of network services functions (such as firewalls, load 30 balancers) in large-scale environments. The term service chaining is 31 used to describe the deployment of such services, and the ability of 32 a network operator to specify an ordered list of services that should 33 be applied to a deterministic set of traffic flows. Such service 34 chains require integration of service policy alongside the deployment 35 of applications, while allowing for the optimal utilization of 36 network resources. 38 Status of this Memo 40 This Internet-Draft is submitted in full conformance with the 41 provisions of BCP 78 and BCP 79. 43 Internet-Drafts are working documents of the Internet Engineering 44 Task Force (IETF). Note that other groups may also distribute 45 working documents as Internet-Drafts. The list of current Internet- 46 Drafts is at http://datatracker.ietf.org/drafts/current/. 48 Internet-Drafts are draft documents valid for a maximum of six months 49 and may be updated, replaced, or obsoleted by other documents at any 50 time. It is inappropriate to use Internet-Drafts as reference 51 material or to cite them other than as "work in progress." 53 This Internet-Draft will expire on January 14, 2014. 55 Copyright Notice 57 Copyright (c) 2013 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (http://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with respect 65 to this document. Code Components extracted from this document must 66 include Simplified BSD License text as described in Section 4.e of 67 the Trust Legal Provisions and are provided without warranty as 68 described in the Simplified BSD License. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 73 1.1. Definition of Terms . . . . . . . . . . . . . . . . . . . 4 74 2. Problem Areas . . . . . . . . . . . . . . . . . . . . . . . . 6 75 3. Service Function Chaining for Adding Network Services . . . . 9 76 4. Related IETF Work . . . . . . . . . . . . . . . . . . . . . . 10 77 5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 78 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 79 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 80 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 81 8.1. Normative References . . . . . . . . . . . . . . . . . . . 14 82 8.2. Informative References . . . . . . . . . . . . . . . . . . 14 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 85 1. Introduction 87 New data center (DC) networks, mobile networks, Internet cloud 88 architectures and existing networks require more flexible deployment 89 models that are able to support many different forms of applications 90 and related network services. Network services include but are not 91 limited to, traditional services such as firewalls and server load 92 balancers, as well as applications and features that operate on 93 network data. Additionally, these services must be delivered in the 94 context of multi-tenancy where each individual tenant is an isolated 95 user group attached to a common data center. These isolated tenants 96 may require unique capabilities with the ability to tailor service 97 characteristics on a per-tenant basis that should not affect other 98 contexts. Similarly, in other deployments, service feature 99 deployments might be associated with subscribers (e.g. activated at 100 the GI interface), or within the scope of a VPN offering. 102 The current network service deployment models are relatively static 103 in that they are bound to relatively fixed topology as well as 104 relatively static resources. At present, these models are not easily 105 manipulated (i.e.: moved, created or destroyed) even when virtualized 106 elements are deployed. This poses a problem in highly elastic 107 service environments that require relatively rapid creation, 108 destruction or movement of real or virtual services or network 109 elements. Additionally, the transition to virtual platforms requires 110 an agile service insertion model that supports elastic and very 111 granular service delivery, and post-facto modification; supports the 112 movement of service functions and application workloads in the 113 existing network, all the while retaining the network and service 114 policies and the ability to easily bind service policy to granular 115 information such as per-subscriber state. 117 This document outlines the problems encountered with existing service 118 deployment models for service chaining, as well as the problems of 119 service chain creation/deletion, policy selection integration with 120 service chains, and policy enforcement within the network 121 infrastructure. 123 1.1. Definition of Terms 125 Classification: Locally instantiated policy and customer/network/ 126 service profile matching of traffic flows for identification of 127 appropriate outbound forwarding actions. 129 Network Overlay: Logical network built on top of existing network 130 (the underlay). Packets are encapsulated or tunneled to create 131 the overlay network topology. 133 Service Chain: A service chain defines the services required 134 (e.g.FW), and their order (service1 --> service2) that must be 135 applied to packets and/or frames. 137 Service Function: A L4-L7 service function (NAT, FW, DPI, IDS, 138 application based packet treatment), application, compute 139 resource, storage, or content used singularly or in collaboration 140 with other service functions to enable a service offered by a 141 network operator. 143 Service Node: Physical or virtual element providing one or more 144 service functions. 146 Network Service: An externally visible service offered by a network 147 operator; a service may consist of a single service function or a 148 composite built from several service functions executed in one or 149 more pre-determined sequences and delivered by one or more service 150 nodes. 152 2. Problem Areas 154 The following points describe aspects of existing service deployment 155 that are problematic, and are being addressed by the network service 156 chaining effort. 158 1. Topological Dependencies: Network service deployments are often 159 coupled to the physical network topology creating constraints on 160 service delivery and potentially inhibiting the network operator 161 from optimally utilizing service resources. This limits scale, 162 capacity, and redundancy across network resources. 164 These topologies serve only to "insert" the service function 165 (i.e. ensure that traffic traverse a service function); they are 166 not required from a native packet delivery perspective. For 167 example, firewalls often require an "in" and "out" layer-2 168 segment and adding a new firewall requires changing the topology 169 (i.e. adding new L2 segments). 171 As more service functions are required - often with strict 172 ordering - topology changes are needed before and after each 173 service function resulting in complex network changes and device 174 configuration. In such topologies, all traffic, whether a 175 service function needs to be applied or not, often passes 176 through the same strict order. 178 A common example is web servers using a server load balancer as 179 the default gateway. When the web service responds to non-load 180 balanced traffic (e.g. administrative or backup operations) all 181 traffic from the server must traverse the load balancer forcing 182 network administrators to create complex routing schemes or 183 create additional interfaces to provide an alternate topology. 185 2. Configuration complexity: A direct consequence of topological 186 dependencies is the complexity of the entire configuration, 187 specifically in deploying service chains. Simple actions such 188 as changing the order of the service functions in a service 189 chain require changes to the topology. Changes to the topology 190 are avoided by the network operator once installed, configured 191 and deployed in production environments fearing misconfiguration 192 and downtime. All of this leads to very static service delivery 193 models. Furthermore, the speed at which these topological 194 changes can be made is not rapid or dynamic enough as it often 195 requires manual intervention, or use of slow provisioning 196 systems. 198 The service itself can contribute to complexity: it may require 199 an intricate combination of very different capabilities, 200 regardless of the underlying topology. QoS-based, resilient VPN 201 service offerings are a typical example of such complexity. 203 3. Constrained High Availability: An effect of topological 204 dependency is constrained service function high availability. 205 Worse, when modified, inadvertent non-high availability can 206 result. 208 Since traffic reaches services based on network topology, 209 alternate, or redundant service functions must be placed in the 210 same topology as the primary service. 212 4. Consistent Ordering of Service Functions: Service functions are 213 typically independent; service function_1 (SF1)...service 214 function_n (SFn) are unrelated and there is no notion at the 215 service layer that SF1 occurs before SF2. However, to an 216 administrator many service functions have a strict ordering that 217 must be in place, yet the administrator has no consistent way to 218 impose and verify the ordering of the functions that used to 219 deliver a given service. 221 5. Service Chain Construction: Service chains today are most 222 typically built through manual configuration processes. These 223 are slow and error prone. With the advent of newer service 224 deployment models the control / management planes will provide 225 not only connectivity state, but will also be increasingly 226 utilized for the formation of services. Such a control / 227 management plane could be centrally controlled and managed, or 228 be distributed between a subset of end-systems. 230 6. Application of Service Policy: Service functions rely on 231 topology information such as VLANs or packet (re) classification 232 to determine service policy selection, i.e. the service function 233 specific action taken. Topology information is increasingly 234 less viable due to scaling, tenancy and complexity reasons. The 235 topological information is often stale, providing the operator 236 with inaccurate placement that can result in suboptimal resource 237 utilization. Per-service function packet classification is 238 inefficient and prone to errors, duplicating functionality 239 across services. Furthermore packet classification is often too 240 coarse lacking the ability to determine class of traffic with 241 enough detail. 243 7. Transport Dependence: Services can and will be deployed in 244 networks with a range of transports, including under and 245 overlays. The coupling of services to topology requires 246 services to support many transports or for a transport gateway 247 function to be present. 249 8. Elastic Service Delivery: Given the current state of the art for 250 adding/removing services largely centers around VLANs and 251 routing changes, rapid changes to the service layer can be hard 252 to realize due to the risk and complexity of such changes. 254 9. Traffic Selection Criteria: Traffic selection is coarse, that 255 is, all traffic on a particular segment traverse service 256 functions whether the traffic requires service enforcement or 257 not. This lack of traffic selection is largely due to the 258 topological nature of service deployment since the forwarding 259 topology dictates how (and what) data traverses service 260 function(s). In some deployments, more granular traffic 261 selection is achieved using policy routing or access control 262 filtering. This results in operationally complex configurations 263 and is still relatively inflexible. 265 10. Limited End-to-End Service Visibility: Troubleshooting service 266 related issues is a complex process that involve network and 267 service expertise. This is especially the case when service 268 chains span multiple DCs, or across administrative boundaries 269 such as externally consumable service chain components. 271 11. Per-Service (re)Classification: Classification occurs at each 272 service, independent from previously applied service functions. 273 These unrelated classification events consume resources per 274 service. More importantly, the classification functionality 275 often differs per service and services cannot leverage the 276 results from other deployed network or service. 278 12. Symmetric Traffic Flows: Service chains may be unidirectional or 279 bidirectional; unidirectional is one where traffic is passed 280 through a set of service functions in one forwarding direction 281 only. Bidirectional is one where traffic is passed through a 282 set of service functions in both forwarding directions. 283 Existing service deployment models provide a static approach to 284 realizing forward and reverse service chain association most 285 often requiring complex configuration of each network device 286 throughout the forwarding path. 288 3. Service Function Chaining for Adding Network Services 290 Service chaining provides a framework to address the aforementioned 291 problems associated with service deployments: 293 1. Service Overlay: Service chaining utilizes a service specific 294 overlay that creates the service topology: the overlay creates a 295 path between service nodes. The service overlay is independent 296 of the network topology and allows operators to use whatever 297 overlay or underlay they prefer and to locate service functions 298 in the network as needed. Within the service topology, services 299 can be viewed as resources for consumption and an arbitrary 300 topology constructed to connect those resources in a required 301 order. Furthermore, additional service instances, for redundancy 302 or load distribution, can be added or removed to the service 303 topology as required. Lastly, the service overlay can provide 304 service specific information needed for troubleshooting service- 305 related issues. 307 2. Generic Service Control Plane (GSCP): GSCP provides information 308 about the available services on a network. The information 309 provided by the control plane includes service network location 310 (for topology creation), service type (e.g. firewall, load 311 balancer, etc.) and, optionally, administrative information about 312 the services such as load, capacity and operating status. GSCP 313 allows for the formulation of service chains and disseminates the 314 service chains to the network. 316 3. Service Classification: Classification is used to select which 317 traffic enters a service overlay. The granularity of the 318 classification varies based on device capabilities, customer 319 requirements, and service functionality. Initial classification 320 is used to start the service chain. Subsequent classification 321 can be used within a given service chain to alter the sequence of 322 services applied. Symmetric classification ensures that forward 323 and reverse chains are in place. 325 4. Dataplane Metadata: Dataplane metadata provides the ability to 326 exchange information between the network and services, services 327 and services and services and the network. Metadata can include 328 the result of antecedent classification, information from 329 external sources or forwarding related data. For example, 330 services utilize metadata, as required, for localized policy 331 decision. 333 4. Related IETF Work 335 The following subsections discuss related IETF work and are provided 336 for reference. This section is not exhaustive, rather it provides an 337 overview of the various initiatives and how they relate to network 338 service chaining. 340 1. L3VPN[L3VPN]: The L3VPN working group is responsible for 341 defining, specifying and extending BGP/MPLS IP VPNs solutions. 342 Although BGP/MPLS IP VPNs can be used as transport for service 343 chaining deployments, the service chaining WG focuses on the 344 service specific protocols, not the general case of VPNs. 345 Furthermore, BGP/MPLS IP VPNs do not address the requirements for 346 service chaining. 348 2. LISP[LISP]: LISP provides locator and ID separation. LISP can be 349 used as an L3 overlay to transport service chaining data but does 350 not address the specific service chaining problems highlighted in 351 this document. 353 3. NVO3[NVO3]: The NVO3 working group is chartered with creation of 354 problem statement and requirements documents for multi-tenant 355 network overlays. NVO3 WG does not address service chaining 356 protocols. 358 4. ALTO[ALTO]: The Application Layer Traffic Optimization Working 359 Group is chartered to provide topological information at a higher 360 abstraction layer, which can be based upon network policy, and 361 with application-relevant services located in it. The mechanism 362 for ALTO obtaining the topology can vary and policy can apply to 363 what is provided or abstracted. This work could be leveraged and 364 extended to address the need for services discovery. 366 5. I2RS[I2RS]: The Interface to the Routing System Working Group is 367 chartered to investigate the rapid programming of a device's 368 routing system, as well as the service of a generalized, multi- 369 layered network topology. This work could be leveraged and 370 extended to address some of the needs for service chaining in the 371 topology and device programming areas. 373 5. Summary 375 This document highlights problems associated with network service 376 deployment today and identifies several key areas that will be 377 addressed by the service chaining working group. Furthermore, this 378 document identifies four components that are the basis for serice 379 chaining. These components will form the areas of focus for the 380 working group. 382 6. Security Considerations 384 Security considerations are not addressed in this problem statement 385 only document. Given the scope of service chaining, and the 386 implications on data and control planes, security considerations are 387 clearly important and will be addressed in the specific protocol and 388 deployment documents created by the service chaining working group. 390 7. Acknowledgments 392 The authors would like to thank David Ward, Rex Fernando and Jim 393 French for their contributions. 395 8. References 397 8.1. Normative References 399 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 400 Requirement Levels", BCP 14, RFC 2119, March 1997. 402 8.2. Informative References 404 [ALTO] "Application-Layer Traffic Optimization (alto)", 405 . 407 [I2RS] "Interface to the Routing System (i2rs)", 408 . 410 [L3VPN] "Layer 3 Virtual Private Networks (l3vpn)", 411 . 413 [LISP] "Locator/ID Separation Protocol (lisp)", 414 . 416 [NVO3] "Network Virtualization Overlays (nvo3)", 417 . 419 Authors' Addresses 421 Paul Quinn 422 Cisco Systems, Inc. 424 Email: paulq@cisco.com 426 Jim Guichard 427 Cisco Systems, Inc. 429 Email: jguichar@cisco.com 431 Surendra Kumar 432 Cisco Systems, Inc. 434 Email: smkumar@cisco.com 436 Abhishek Chauhan 437 Citrix 439 Email: Abhishek.Chauhan@citrix.com 441 Nic Leymann 442 Deutsche Telekom 444 Email: n.leymann@telekom.de 446 Mohamed Boucadair 447 France Telecom 449 Email: mohamed.boucadair@orange.com 451 Christian Jacquenet 452 France Telecom 454 Email: christian.jacquenet@orange.com 455 Michael Smith 456 Insieme Networks 458 Email: michsmit@insiemenetworks.com 460 Navindra Yadav 461 Insieme Networks 463 Email: nyadav@insiemenetworks.com 465 Thomas Nadeau 466 Juniper Networks 468 Email: tnadeau@juniper.net 470 Ken Gray 471 Juniper Networks 473 Email: kgray@juniper.net 475 Brad McConnell 476 Rackspace 478 Email: bmcconne@rackspace.com