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Dreibholz 3 Internet-Draft Simula Research Laboratory 4 Intended status: Standards Track January 23, 2017 5 Expires: July 27, 2017 7 An IPv4 Flowlabel Option 8 draft-dreibholz-ipv4-flowlabel-25.txt 10 Abstract 12 This draft defines an IPv4 option containing a flowlabel that is 13 compatible to IPv6. It is required for simplified usage of IntServ 14 and interoperability with IPv6. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on July 27, 2017. 33 Copyright Notice 35 Copyright (c) 2017 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 52 1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 2 53 1.3. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3 54 2. A Flow Label Option for IPv4 . . . . . . . . . . . . . . . . 3 55 2.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 56 2.1.1. The Flow Label Field of IPv6 . . . . . . . . . . . . 3 57 2.1.2. The Limitations of IntServ via IPv4 . . . . . . . . . 4 58 2.2. Definition of the Flow Label Option . . . . . . . . . . . 5 59 3. Translation between IPv6 and IPv4 . . . . . . . . . . . . . . 6 60 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 61 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 62 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 63 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 64 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 65 7.2. Informative References . . . . . . . . . . . . . . . . . 7 66 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 68 1. Introduction 70 1.1. Terminology 72 This document uses the following terms: 74 o IntServ (Integrated Services): Reservation of network resources 75 (bandwidth) on a per-flow basis. See [RFC1633], [RFC2205], 76 [RFC2208], [RFC2209], [RFC2210], [RFC2211] and [RFC2212] for 77 details. 79 o Flow: An IntServ reservation between two endpoints. 81 o Flow Label: The Flow Label field of the IPv6 header and the IPv4 82 option header defined in this draft. It is used for marking a 83 packet to use a specific IntServ reservation. See [RFC6437], 84 [RFC6436] for detailed descriptions. 86 1.2. Abbreviations 88 o RSVP: ReSource Reservation Protocol 90 o SCTP: Stream Control Transmission Protocol 92 o TCP: Transmission Control Protocol 94 o QoS: Quality of Service 95 o UDP: User Datagram Protocol 97 1.3. Conventions 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 101 document are to be interpreted as described in [RFC2119]. 103 2. A Flow Label Option for IPv4 105 2.1. Motivation 107 This section describes the motivation to add a flow label option to 108 the IPv4 protocol. 110 2.1.1. The Flow Label Field of IPv6 112 The Flow Label field (see [RFC6436] and [RFC6437]) of the IPv6 header 113 (see [RFC2460]) is a 20-bit number. All packets from the same source 114 address having the same flow label MUST contain the same destination 115 address. Therefore, the flow label combined with the source address 116 is a network- unique identification for a specific packet flow. The 117 idea behind the flow label is marking specific flows for IntServ. 118 That is, the routers on the path from source to destination keep e.g. 119 reservation states for the flows. The flow label provides easy 120 identification and utilizes efficient lookup, e.g. using a hash 121 function on the 3-tuple (source address, destination address, flow 122 label). 124 Using the IPv6 flow label, packets can be mapped easily to specific 125 flows, with the following features: 127 o Transport Layer Protocol Independence: Since the mapping is 128 directly specified in the IP header, all possible layer 4 129 protocols are supported, even protocols to be specified in a far 130 future. 132 o Support for Network Layer Encryption: The mapping is independent 133 of payload encryption (e.g. by IPsec). 135 o Support for Fragmentation: If fragmentation of a large IP packet 136 is necessary, all fragments contain the same flow label. 137 Therefore, fragmentation does not cause any flow-marking problem. 139 o Flow Sharing: By marking packets with a flow label, it is possible 140 to share a single flow (IntServ reservation) with several 141 communication associations from host A to host B. For example, a 142 video stream via UDP and a HTTP download via TCP could share a 143 single reservation. For the user, flow sharing has the advantage 144 that if one of its communication associations temporarily requires 145 lower bandwidth than expected, other associations sharing the same 146 flow may use the remaining bandwidth. That is, his possibly 147 expensive reservation is fully utilized. Flow sharing also helps 148 keeping the total number of reservations a router has to handle 149 small, reducing their CPU and memory requirements and therefore 150 cost. 152 o Multi-Flow Connections: One communication association can divide 153 up its packets to several flows, simply by marking packets with 154 different flow labels. This technique can be used for layered 155 transmission. That is, a stream (e.g. a video) is divided up into 156 several parts (called layers). For example, the first layer (base 157 layer) of a video contains a low-quality version, the second (1st 158 enhancement layer) the data to generate a higher-quality version, 159 etc.. Now, the first layer can be mapped to a high-quality 160 reservation (guaranteed bandwidth, low loss rate) at higher cost, 161 but the following layers can be mapped to lower-quality 162 reservations (e.g. higher loss rate) or even best effort at lower 163 cost. Research shows that the total transmission cost can be 164 highly reduced using layered transmission (see [Dre2001], 165 [IJMUE2009] for details). 167 2.1.2. The Limitations of IntServ via IPv4 169 Using IntServ with IPv4, there are several problems that can only be 170 solved with high management effort: 172 o No Transport Layer Protocol Independence: It is necessary to mark 173 the packets within the layer 4 protocol header. For example, the 174 TCP, UDP or SCTP port numbers can be used to mark flows (with 175 limitations, see below). But for new protocols (e.g. 176 experimental, new standards, proprietary), software updates for 177 *all* IntServ routers are necessary to recognize the packet flow! 179 o No Support for Network Layer Encryption: Since it is necessary to 180 read fields of the layer 4 protocol header, it may not be 181 encrypted. Therefore, e.g. the usage of IPsec is impossible. 183 o Support for Fragmentation: Only the first fragment of a large 184 packet contains the layer 4 header necessary to map the packet to 185 a flow. Mapping other fragments would require the hops to 186 remember packet identities and try to map fragments to packet 187 identities. Due to the management effort and memory requirements, 188 this is not realistic for high-bandwidth backbone routers; 189 especially when packet reordering must be considered. 191 Furthermore, load sharing or traffic distribution would be 192 impossible. 194 o No Flow Sharing: It is usually impossible for two different 195 communication associations to share the same flow, e.g. if TCP 196 flows are recognized using port numbers. This makes it necessary 197 to reserve an IntServ flow for each communication association. 198 This implies an increased number of flow states for routers to 199 keep and maintain. Furthermore, if one association temporarily 200 uses a lower bandwidth, the free bandwidth of its flow cannot 201 easily be borrowed to another association. 203 o No Multi-Flow Connections: To use layered transmission, e.g. a 204 video via UDP, the transmission of every layer would require own 205 port numbers. In the case of connection-oriented transmission 206 protocols (e.g. TCP, SCTP), every layer would even require its 207 own connection setup and management. Depending on the transport 208 protocol, the number of communication associations and the number 209 of flows, much more work is necessary compared to IPv6 using flow 210 labels. 212 All in all, using IntServ flows with IPv4 requires much more work 213 compared to IPv6, where simply the flow label can be used. It is 214 therefore useful to add such a field to IPv4, too. An appropriate 215 place to add such a field is an IPv4 option header. 217 2.2. Definition of the Flow Label Option 219 IPv4 (see [RFC0791]) already defines an option header for a 16-bit 220 SATNET stream identifier. Since this identifier would be 221 incompatible to the 20-bit IPv6 flow label, reuse of this existing 222 option header is inappropriate. Therefore, a new one is defined as 223 follows. 225 Flow Label Option 227 0 1 2 3 228 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 229 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 230 | Type | Length |0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0| 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 |0 0 0 0 0 0 0 0|0 0 0 0| Flow Label | 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 235 o Type: 143 237 o Length: 8 octets 238 o Flow Label: The 20-bit flow label. All definitions of [RFC6437] 239 and [RFC6436] for the IPv6 flow label are also valid for this 240 field. A value of zero denotes that no flow label is used. In 241 this case, the flow label option is in fact unnecessary. 243 The Flow Label option SHOULD be copied on fragmentation. It MUST be 244 the first option of the IP header and therefore MUST NOT appear more 245 than once per IPv4 packet. The Router Alert option SHOULD NOT be 246 used to mark the necessity for routers to examine the options. 247 Placing the Flow Label option as first option allows for easy 248 processing in hardware. 250 3. Translation between IPv6 and IPv4 252 Since the new IPv4 flow label is fully compatible to the IPv6 flow 253 label, the field MAY be translated in the other protocol's one during 254 protocol translation. That is, a router can translate an IPv6 packet 255 set from an IPv6-only host to an IPv4-mapped address of an IPv4-only 256 host and the flow label may simply be copied. The same may also be 257 applied in the backwards direction. 259 Note, that copying the flow label during protocol translation is not 260 mandatory. There may be IntServ reservation reasons for not copying 261 but setting the flow label to zero. But a router MUST NOT set the 262 flow label to another value than the copy or 0, since the source is 263 responsible to ensure that the source address combined with the flow 264 label is network-unique 266 4. Security Considerations 268 Security considerations are similar to the IPv6 flow label, see 269 [RFC6437]. 271 5. IANA Considerations 273 This document introduces no additional considerations for IANA. 275 6. Acknowledgments 277 The author would like to thank Brian E. Carpenter, Wes George, Perry 278 Lorier, Christoph Reichert and Michael Tuexen for their comments. 280 7. References 281 7.1. Normative References 283 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 284 DOI 10.17487/RFC0791, September 1981, 285 . 287 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 288 Requirement Levels", BCP 14, RFC 2119, 289 DOI 10.17487/RFC2119, March 1997, 290 . 292 [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S. 293 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 294 Functional Specification", RFC 2205, DOI 10.17487/RFC2205, 295 September 1997, . 297 [RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated 298 Services", RFC 2210, DOI 10.17487/RFC2210, September 1997, 299 . 301 [RFC2211] Wroclawski, J., "Specification of the Controlled-Load 302 Network Element Service", RFC 2211, DOI 10.17487/RFC2211, 303 September 1997, . 305 [RFC2212] Shenker, S., Partridge, C., and R. Guerin, "Specification 306 of Guaranteed Quality of Service", RFC 2212, 307 DOI 10.17487/RFC2212, September 1997, 308 . 310 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 311 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 312 December 1998, . 314 [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, 315 "IPv6 Flow Label Specification", RFC 6437, 316 DOI 10.17487/RFC6437, November 2011, 317 . 319 7.2. Informative References 321 [RFC1633] Braden, R., Clark, D., and S. Shenker, "Integrated 322 Services in the Internet Architecture: an Overview", 323 RFC 1633, DOI 10.17487/RFC1633, June 1994, 324 . 326 [RFC2208] Mankin, A., Ed., Baker, F., Braden, B., Bradner, S., 327 O'Dell, M., Romanow, A., Weinrib, A., and L. Zhang, 328 "Resource ReSerVation Protocol (RSVP) -- Version 1 329 Applicability Statement Some Guidelines on Deployment", 330 RFC 2208, DOI 10.17487/RFC2208, September 1997, 331 . 333 [RFC2209] Braden, R. and L. Zhang, "Resource ReSerVation Protocol 334 (RSVP) -- Version 1 Message Processing Rules", RFC 2209, 335 DOI 10.17487/RFC2209, September 1997, 336 . 338 [RFC6436] Amante, S., Carpenter, B., and S. Jiang, "Rationale for 339 Update to the IPv6 Flow Label Specification", RFC 6436, 340 DOI 10.17487/RFC6436, November 2011, 341 . 343 [Dre2001] Dreibholz, T., "Management of Layered Variable Bitrate 344 Multimedia Streams over DiffServ with Apriori Knowledge", 345 Masters Thesis, February 2001, . 349 [IJMUE2009] 350 Zhu, W., Dreibholz, T., Rathgeb, E., and X. Zhou, "A 351 Scalable QoS Device for Broadband Access to Multimedia 352 Services", SERSC International Journal of Multimedia and 353 Ubiquitous Engineering (IJMUE) Number 2, Volume 4, Pages 354 157-172, ISSN 1975-0080, May 2009, 355 . 358 Author's Address 360 Thomas Dreibholz 361 Simula Research Laboratory, Network Systems Group 362 Martin Linges vei 17 363 1364 Fornebu, Akershus 364 Norway 366 Phone: +47-6782-8200 367 Fax: +47-6782-8201 368 Email: dreibh@simula.no 369 URI: http://www.iem.uni-due.de/~dreibh/