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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC6146' is defined on line 365, but no explicit reference was found in the text ** Obsolete normative reference: RFC 2629 (Obsoleted by RFC 7749) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force A. Wang 3 Internet-Draft China Telecom 4 Intended status: Standards Track S. Jiang 5 Expires: April 24, 2015 Huawei Technologies Co., Ltd 6 October 21, 2014 8 IPv6 Flow Label Reflection 9 draft-wang-6man-flow-label-reflection-00 11 Abstract 13 The current definition of the IPv6 Flow Label focuses mainly on how 14 the packet source forms the value of this field and how the forwarder 15 in-path treats it. In network operations, there are needs to 16 correlate an upstream session and the corresponding downstream 17 session together. This document propose a flow label reflection 18 mechanism that network devices copy the flow label value from 19 received packets to the corresponding flow label field in return 20 packets. This mechanism could simplify the network traffic 21 recognition process in network operations and make the policy for 22 both directions of traffic of one session consistent. 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 April 24, 2015. 41 Copyright Notice 43 Copyright (c) 2014 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. Summary of the current usage for IPv6 Flow Label . . . . 3 60 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 61 3. Potential Benefit of Flow Label Reflection . . . . . . . . . 4 62 4. Flow Label Reflection Behaviors on Network Devices . . . . . 4 63 5. Applicable Scenarios . . . . . . . . . . . . . . . . . . . . 5 64 5.1. Flow Label Reflection on CP servers . . . . . . . . . . . 5 65 5.2. Flow Label Reflection for Bi-direction Tunnels . . . . . 6 66 5.3. Flow Label Reflection on edge devices . . . . . . . . . . 6 67 6. Deployment Consideration . . . . . . . . . . . . . . . . . . 7 68 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 69 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 70 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 71 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 72 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 73 10.2. Informative References . . . . . . . . . . . . . . . . . 8 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 76 1. Introduction 78 The IPv6 flow label [RFC6437] in the fixed IPv6 header is designed to 79 differentiate the various flow session of IPv6 traffic; it can 80 accelerate the clarification and treatment of IPv6 traffic by the 81 network devices in its forwarding path. In practice, many current 82 implementations use the 5-tuple {dest addr, source addr, protocol, 83 dest port, source port} as the identifier of network flows. However, 84 transport-layer information, such as the port numbers, is not always 85 in a fixed position, since it follows any IPv6 extension headers that 86 may be present; in contrast, the flow label is at a fixed position in 87 every IPv6 packet and easier to access. In fact, the logic of 88 finding the transport header is always more complex for IPv6 than for 89 IPv4, due to the absence of an Internet Header Length field in IPv6. 90 Additionally, if packets are fragmented, the flow label will be 91 present in all fragments, but the transport header will only be in 92 one packet. Therefore, within the lifetime of a given transport- 93 layer connection, the flow label can be a more convenient "handle" 94 than the port number for identifying that particular connection. 96 The usages of IPv6 flow label, so far as briefly summarized in 97 Section 1.1, only exploit the characteristic of IPv6 flow label in 98 one direction. 100 In current practice, an application session is often recognized as 101 two separated IP traffics, in two opposite directions. However, from 102 the point view of a service provider, the upstream and downstream of 103 one session should be handled together, particularly, when 104 application-aware operations are placed in the network. A ubiquitous 105 example is that end user initiates a request, with small-scale data 106 transmitted, towards a content server, then the server responds with 107 a large set of follow-up packets. The bi-directional flows should be 108 correlated together and handled with the same policy. Ideally, the 109 request embeds a flow recognition identifier that is accessible and 110 the follow-up response packets carry the same identifier. The flow 111 label is a good choice for the flow recognition identifier. 113 This document proposes a flow label reflection mechanism so that 114 network devices copy the flow label value from received packets to 115 the corresponding flow label field in return packets. By having the 116 same flow label value in the downstream and upstream of one IPv6 117 traffic session, the network traffic recognition process and the 118 traffic policy deployment in network operations could be simplified. 119 It may also increase the accuracy of network traffic recognition. 121 Several applicable scenarios of the IPv6 flow label reflection are 122 also given, in Section 5. For now, this document only considers the 123 scenario in a single administrative domain, although the IPv6 flow 124 label reflection mechanism may also bring benefits into cross domain 125 scenarios. 127 1.1. Summary of the current usage for IPv6 Flow Label 129 [RFC6438] describe the usage of IPv6 Flow Label for ECMP and link 130 aggregation in Tunnels; it mainly utilizes the random distribution 131 characteristic of IPv6 flow label. [RFC7098] also describes similar 132 usage in server farms. 134 All these usage scenarios consider only the usage of IPv6 flow label 135 in one direction, while many bi-directional network traffics need to 136 be treated together. 138 2. Requirements Language 140 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 141 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 142 "OPTIONAL" in this document are to be interpreted as described in 143 [RFC2119] when they appear in ALL CAPS. When these words are not in 144 ALL CAPS (such as "should" or "Should"), they have their usual 145 English meanings, and are not to be interpreted as [RFC2119] key 146 words. 148 Flow Label Reflection A mechanism/behavior so that a network device 149 copies the value of flow label from a IPv6 flow into a 150 corresponding return IPv6 flow. 152 Flow Label Reflection Device A network device that applies the flow 153 label reflection mechanism. It is the end of an IPv6 flow and the 154 initiation node of the corresponding return IPv6 flow. 156 3. Potential Benefit of Flow Label Reflection 158 With flow label reflection mechanism, the IPv6 Flow Label could be 159 used to correlate the upstream and downstream packets of bi- 160 directional traffics: 162 o It makes the downstream and upstream of one session be easily 163 recognized. It makes the correlation of traffic and then the 164 recognition of various traffics easier. 166 o The network operator can easily apply the same policy to the bi- 167 directional traffic of one interested session 169 o The traffic analyzer can also easily correlate the upstream and 170 downstream of one session to find the symptoms of various internet 171 protocols. 173 4. Flow Label Reflection Behaviors on Network Devices 175 To fulfill the flow label reflection mechanism, the below proposed 176 behaviors on network devices: 178 o The generation method of IPv6 flow label in source IPv6 node 179 SHOULD follow the guidelines in [RFC6437], that is the IPv6 flow 180 label should be generated randomly and distributed enough. 182 o On the Flow Label Reflection Device, the value of IPv6 Flow Label 183 from received packets SHOULD be copied into the corresponding flow 184 label field in return packets by the flow label reflection 185 devices. 187 o The forwarding nodes within the management domain SHOULD follow 188 the specification in [RFC6437], that is the IPv6 flow label SHOULD 189 NOT be modified in the path, unless flow label value in arriving 190 packets is zero. The forwarding nodes MAY follow the 191 specification in [RFC6438] when using the flow label for load 192 balancing by equal cost multipath (ECMP) routing and for link 193 aggregation, particularly for IPv6-in-IPv6 tunneled traffic. 195 o The network traffic recognition devices, or devices that may have 196 differentiated operations per flow, SHOULD recognize and analyze 197 network traffics based on 3-tuple of {dest addr, source addr, 198 flowlabel}. It SHOULD consider the traffics that have same flow 199 label value and reversed source/dest addr as upstream and 200 downstream of the same flow, match them together to accomplish the 201 traffic recognition process. 203 o Other network operations MAY also be based on 3-tuple of {dest 204 addr, source addr, flowlabel}. 206 5. Applicable Scenarios 208 This section describes some applicable scenarios, which network 209 operators can benefit from deploying the flow label reflection 210 mechanism. It is not a complete enumeration. More scenarios may be 211 introduced in the future. 213 5.1. Flow Label Reflection on CP servers 215 There is rapidly increasing requirement from service providers (SP) 216 to cooperate with the content providers (CP) to provide more accurate 217 services and charging policies based on accurate traffic recognition. 218 The service providers need to recognize the CP/SP's bi-directional 219 traffics at the access edge devices of the network, such as 220 BRAS/PDSN/P-GW devices. 222 Normally, the burden for these edge devices to recognize the 223 subscriber's upstream traffic is light, because request messages are 224 typically small. But they often need more resource to recognize 225 downstream traffics, which normally contain large data. With flow 226 label reflection on CP servers, recognition based on the 3-tuple of 227 {dest addr, source addr, flowlabel} would reduce the consumption of 228 recognition and make the correlation process much easier. 230 In this scenario, the CP servers would be the Flow Label Reflection 231 Devices. They copy the flow label value from received upstream user 232 request packets to the corresponding flow label field in return 233 downstream packets. 235 The access edge devices of service provider scrutinize the 236 subscriber's upstream IPv6 traffic and record the binding of 3-tuple 237 and traffic-specific policy. If the flow label is zero, the access 238 edge devices must rewrite the flow label value according to local 239 policy. With the recorded binding information, the access edge 240 devices can easily recognize and match the downstream packet to the 241 previous recognized upstream packet, by just accessing 3-tuple. The 242 edge devices can then apply the corresponding traffic policy to the 243 upstream/downstream of the session to the cooperated CP. 245 Note: this mechanism may not reliable when the CP servers are not 246 directly connected to the service provider, because there is no 247 guarantee the flow label would not be changed by intermediate devices 248 in other administrative domains. 250 5.2. Flow Label Reflection for Bi-direction Tunnels 252 Tunnel is ubiquitous within service provider networks. It is very 253 difficult (important if the tunnel is encrypted) for intermediate 254 network devices to recognize the inner encapsulated packet, although 255 such recognition could be very helpful in some scenarios, such as 256 traffic statistics, network diagnoses, etc. Furthermore, such 257 recognition normally requires to correlate bi-direction traffic 258 together. The flow label reflection mechanism could provide help in 259 such requirement scenarios. 261 In this scenario, the tunnel end devices would be the Flow Label 262 Reflection Devices. They record the flow label value from received 263 tunnel packets, and copy it to the corresponding flow label field in 264 return packets, which can be recognized by 5-tuple or 3-tuple of the 265 inner packet at the tunnel end devices. 267 The tunnel initiating devices should generate different flow label 268 values for different inner flow traffics based on their 5-tuple or 269 3-tuple in accordance with [RFC6437]. Note: if the inner flow is 270 encryption in ESP model [RFC4303], the transport-layer port numbers 271 are inaccessiable. In such case, 5-tuple is not available. 273 Then the intermediate network device can easily distinguish the 274 different flow within the same tunnel transport link and correlate 275 bi-direction traffics of same flow together. This can also increase 276 the service provider's traffic control capabilities. 278 This mechanism can also work when the encapsulated traffics are IPv4 279 traffics, such as DS-Lite scenario [RFC6333]. The IPv4 5-tuple may 280 be used as the input for the flow label generation. 282 5.3. Flow Label Reflection on edge devices 284 If the flow label reflection mechanisms have been applied on peer 285 host, the service provider could always use it for bi-directional 286 traffic recognition. However, there is no guarantee the flow label 287 would not be changed by intermediate devices in other administrative 288 domains. Therefore, to make the flow label value trustful, the edge 289 devices need to validate the flow label reflection. 291 In this scenario, the edge devices would be the (backup) Flow Label 292 Reflection Devices. They record the flow label value from the 293 packets that leave the domain. When the corresponding flow label 294 field in return packets are recognized by 5-tuple or 3-tuple at the 295 edge devices, the edge devices should check the flow label as below: 297 o if the flow label matches the record value, it remains; 299 o if the flow label is zero, the edge devices copy the record value 300 into it; 302 o if the flow label is non-zero, but does not matches the record 303 value, the edge devices can decide the flow label are modified by 304 other intermediate devices (with the assumption the peer host has 305 reflect the original flow label), then restore the flow label 306 using the record value. 308 Then the network recognition devices located anywhere within the 309 service provider network could easily correlate bi-directional 310 traffics together, and apply traffic-specific policy accordingly. 312 6. Deployment Consideration 314 The IPv6 flow label reflection mechanism requires the "Flow Label 315 Reflection Device" to be stateful, store the flow label value and 316 copy it to the corresponding return packet. Such change cannot be 317 accomplished within a short term, and therefore the deployment of 318 this mechanism will be accomplished gradually. During the 319 incremental deployment period, the traditional recognition 320 mechanisms, which are more expensive, would coexist. The traffics 321 that could not be recognized by 3-tuple of {dest addr, source addr, 322 flowlabel} could fall back to the traditional process or be skipped 323 over by advanced services. The more devices support the flow label 324 reflection mechanism, the less consumption for traffic recognition 325 from the network management perspective, or the better coverage of 326 advanced services that are based on the traffic recognition. 328 7. Security Considerations 330 Security aspects of the flow label are discussed in [RFC6437]. A 331 malicious source or man-in-the-middle could disturb the traffic 332 recognition by manipulating flow labels. However, the worst case is 333 that fall back to the current practice that an application session is 334 often recognized as two separated IP traffics. The flow label does 335 not significantly alter this situation. 337 Specifically, the IPv6 flow label specification [RFC6437] states that 338 "stateless classifiers should not use the flow label alone to control 339 load distribution." This is answered by also using the source and 340 destination addresses with flow label. 342 8. IANA Considerations 344 This draft does not request any IANA action. 346 9. Acknowledgements 348 The authors would like to thanks Brian Carpenter, who gave many 349 useful advices. The authors would also like to thanks the valuable 350 comments made by Fred Baker, Lee Howard and other members of V6OPS 351 WG. 353 This document was produced using the xml2rfc tool [RFC2629]. 355 10. References 357 10.1. Normative References 359 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 360 Requirement Levels", BCP 14, RFC 2119, March 1997. 362 [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, 363 June 1999. 365 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful 366 NAT64: Network Address and Protocol Translation from IPv6 367 Clients to IPv4 Servers", RFC 6146, April 2011. 369 [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, 370 "IPv6 Flow Label Specification", RFC 6437, November 2011. 372 [RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label 373 for Equal Cost Multipath Routing and Link Aggregation in 374 Tunnels", RFC 6438, November 2011. 376 10.2. Informative References 378 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 379 4303, December 2005. 381 [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- 382 Stack Lite Broadband Deployments Following IPv4 383 Exhaustion", RFC 6333, August 2011. 385 [RFC7098] Carpenter, B., Jiang, S., and W. Tarreau, "Using the IPv6 386 Flow Label for Load Balancing in Server Farms", RFC 7098, 387 January 2014. 389 Authors' Addresses 391 Aijun Wang 392 China Telecom 393 Beijing Research Institute, China Telecom Cooperation Limited 394 No.118, Xizhimenneidajie, Xicheng District, Beijing 100035 395 China 397 Phone: 86-10-58552347 398 Email: wangaj@ctbri.com.cn 400 Sheng Jiang 401 Huawei Technologies Co., Ltd 402 Q14, Huawei Campus, No.156 Beiqing Road 403 Hai-Dian District, Beijing, 100095 404 P.R. China 406 Email: jiangsheng@huawei.com