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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-04) exists of draft-mglt-ipsecme-implicit-iv-01 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ipsecme D. Migault, Ed. 3 Internet-Draft Ericsson 4 Intended status: Standards Track T. Guggemos, Ed. 5 Expires: May 19, 2017 LMU Munich 6 C. Bormann 7 Universitaet Bremen TZI 8 November 15, 2016 10 ESP Header Compression and Diet-ESP 11 draft-mglt-ipsecme-diet-esp-03.txt 13 Abstract 15 ESP Header Compression (EHC) defines a flexible framework to compress 16 communications protected with IPsec/ESP. Compression and 17 decompression is defined by EHC Rules orchestrated by EHC Strategies. 19 The document specifies the Diet-ESP EHC Strategy and associated EHC 20 Rules. Diet-ESP compresses up to 32 bytes per packet for traditional 21 IPv6 VPN and up to 66 bytes for IPv6 VPN set over a single TCP or UDP 22 session. 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 May 19, 2017. 41 Copyright Notice 43 Copyright (c) 2016 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. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 59 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 60 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4 62 5. Diet-ESP EHC Context . . . . . . . . . . . . . . . . . . . . 5 63 5.1. Diet-ESP Context Parameters for ESP . . . . . . . . . . . 6 64 5.2. Diet-ESP Context Parameters for Inner IP . . . . . . . . 6 65 5.3. Diet-ESP Context Parameters for Transport Protocol . . . 7 66 6. Diet-ESP EHC Rules . . . . . . . . . . . . . . . . . . . . . 8 67 6.1. EHC Rules for ESP . . . . . . . . . . . . . . . . . . . . 10 68 6.2. EHC Rules for inner IPv4 . . . . . . . . . . . . . . . . 12 69 6.3. EHC Rules for inner IPv6 . . . . . . . . . . . . . . . . 14 70 6.4. EHC Rules for UDP . . . . . . . . . . . . . . . . . . . . 15 71 6.5. EHC Rules for UDP-Lite . . . . . . . . . . . . . . . . . 16 72 6.6. EHC Rules for TCP . . . . . . . . . . . . . . . . . . . . 17 73 7. Diet-ESP EHC Strategy . . . . . . . . . . . . . . . . . . . . 19 74 7.1. Outbound Packet Processing . . . . . . . . . . . . . . . 19 75 7.2. Inbound Packet Processing . . . . . . . . . . . . . . . . 21 76 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 77 9. Security Considerations . . . . . . . . . . . . . . . . . . . 24 78 10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 25 79 11. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 25 80 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 81 12.1. Normative References . . . . . . . . . . . . . . . . . . 26 82 12.2. Informational References . . . . . . . . . . . . . . . . 27 83 Appendix A. Illustrative Examples . . . . . . . . . . . . . . . 27 84 A.1. Single UDP Session IoT VPN . . . . . . . . . . . . . . . 27 85 A.2. Single TCP session IoT VPN . . . . . . . . . . . . . . . 29 86 A.3. Traditional VPN . . . . . . . . . . . . . . . . . . . . . 32 87 Appendix B. EHC Classification (Informative) . . . . . . . . . . 35 88 B.1. ESP . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 89 B.2. IPv6 (Inner) . . . . . . . . . . . . . . . . . . . . . . 36 90 B.3. IPv4 (Inner) . . . . . . . . . . . . . . . . . . . . . . 37 91 B.4. UDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 92 B.5. UDP-Lite . . . . . . . . . . . . . . . . . . . . . . . . 39 93 B.6. TCP . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 94 Appendix C. Document Change Log . . . . . . . . . . . . . . . . 40 95 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 97 1. Requirements notation 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. Introduction 105 IPsec/ESP [RFC4303] secures communications either using end-to-end 106 security or by building a VPN where the traffic is carried to a 107 secure domain via the security gateway. 109 IPsec/ESP was not designed to reduce the networking overhead of the 110 communications. In fact, reducing bandwidth often adds computational 111 overhead that may negatively impact large infrastructures in which 112 bandwidth usage is not a constraint. On the other hand, IoT devices 113 have completely different constraints. In IoT communications, 114 sending any extra bytes can significantly impact the battery life of 115 devices. These devices are also often expected to be sleeping nodes, 116 for which IPsec sessions have a very different meaning. 118 This document defines ESP Header Compression (EHC), a framework that 119 compresses ESP protected communications. EHC is highly flexible to 120 address any use case where compression is necessary. EHC takes 121 advantage of the negotiation between the communication endpoint to 122 agree on the cryptographic parameters. In some cases, the agreement 123 already includes parameters that remain constant during the 124 communications (like port value, or IP address value). EHC takes 125 advantage of these already agreed parameters, and defines addition 126 parameters that could be agreed for the purpose of compression. 127 Similarly, EHC also defines EHC Rules which define how fields may be 128 compressed and decompressed given the provided parameters. Finally, 129 EHC defines EHC Strategy which defines how a set of EHC Rule is 130 coordinated. 132 The document specifies the Diet-ESP EHC Strategy and associated EHC 133 Rules. Diet-ESP compresses up to 32 bytes per packet for traditional 134 VPN and up to 66 bytes for VPN set over a single TCP or UDP session. 136 3. Terminology 138 This document uses the following terminology: 140 - IoT Internet of Things 141 - IP If not stated otherwise, IP means IPv6. 142 - LSB Least Significant Bytes 143 - MSB Most Significant Bytes 144 - SAD IPsec Security Association Database 145 - SA IPsec Security Association 146 - SPD IPsec Security Policy Database 147 - TS IPsec Traffic Selector 148 - SPI ESP Security Parameter Index 149 - SN ESP Sequence Number 150 - PAD ESP Padding 151 - PL ESP Pad Length 152 - NH Next Header 153 - IV Initialization Vector 154 - IIV Implicit Initialization Vector 155 - ICV Integrity Check Value 156 - VPN Virtual Private Network 158 4. Protocol Overview 160 ESP Header Compression (EHC) compresses IPsec ESP packets, thus 161 reducing the size of the packet sent on the wire, while carrying an 162 equivalent level of information with an equivalent level of security. 164 The primarily motivation for payload size reduction was IoT were the 165 cost of sending extra bytes largely overcomes additional computations 166 and thus considerably reduces the life time of battery powered 167 devices. As a result, IoT communication rather favor expensive 168 compression over additional bandwidth. Standard IPsec VPN may also 169 consider reduction of their bandwidth, but on the other hand, the 170 acceptable computation overhead must remain very low. The ESP Header 171 Compression designated in this document as Diet-ESP attempts to reach 172 theses two goals. 174 ESP Header Compression compresses the standard ESP payload by 175 compressing different fields with a specific compression rules 176 performed in the ESP stack. Concerned fields include fields of the 177 ESP protocol, as well as other protocols in the ESP payload such as 178 the IP header when the tunnel mode is used, the UDP or the TCP 179 header. In fact non ESP fields may be compressed by ESP under 180 certain circumstances, and ESP Header Compression is not intended to 181 provide a generic way, outside of ESP to compress these protocols. 182 Further compression of the ESP payload may be performed by generic 183 mechanism and outside ESP with more generic mechanisms such as for 184 example ROHCoverIPsec [RFC5858] or SCHC 185 [I-D.toutain-6lpwa-ipv6-static-context-hc] which are orthogonal to 186 ESP Header Compression. 188 As depicted in Figure 1, in order to compress the ESP packets, the 189 two peers are expected to agree on the EHC Strategy - Diet-ESP in our 190 case - as well as some extra parameters needed to derive the EHC 191 Rules and EHC Context. 193 EHC Strategy, EHC Strategy, 194 EHC Context <==================> EHC Context 195 | | 196 EHC Rules | EHC Rules | 197 | | | | 198 v v v v 199 +====================+ +====================+ 200 | ESP | | ESP | 201 +====================+ +====================+ 202 | < pre-esp > | | < pre-esp > | 203 +--------------------+ +--------------------+ 204 | < clear text esp > | | < clear text esp > | 205 +--------------------+ +--------------------+ 206 | < encryption > | | < encryption > | 207 +--------------------+ +--------------------+ 208 | < post-esp > | | < post-esp > | 209 +--------------------+ +--------------------+ 211 Figure 1: ESP Header Compression Overview 213 In Figure 1, the ESP stack is represented by various sub layers 214 describing the packet processing inside the ESP. The "pre-esp" layer 215 represents treatment performed to a non ESP packet, i.e. before ESP 216 encapsulation or decapsulation is being proceeded. "clear text esp" 217 designates the ESP encapsulation / decapsulation processing performed 218 on an non encrypted ESP packet. "encryption" designates the 219 encryption/decryption phase and "post-esp" the processing performed 220 on an ESP encrypted packet. EHC Rules may be processed at any of 221 these layers - except for "encryption" layer, and thus impact 222 differently the standard ESP. More specifically, EHC Rules performed 223 at the "pre-esp" or "post-esp" layer does not require the current ESP 224 stack to be updated and can simply be appended to the current ESP 225 stack. On the other hand, EHC Rules at the "clear text esp" may 226 require modification of the current ESP stack. 228 The set of EHC rules described in this document as well as the EHC 229 Strategies may be extended in the future. There is nothing to 230 prevent such EHC Rules and Strategies to be updated. 232 5. Diet-ESP EHC Context 234 The EHC Context provides the necessary information so the two peers 235 can proceed to the appropriated compression and decompression defined 236 by the EHC Strategy. As this document is limited to the Diet-ESP 237 strategy, the EHC Context in this section is also designated as Diet- 238 ESP Context and is used by the Diet-ESP Strategy to activate specific 239 EHC Rules as well as to execute the EHC Rule by providing the 240 necessary parameters.. 242 The Diet-ESP Context is defined on a per-SA basis. It is composed of 243 attributes that are not Diet-ESP specific, as well as attributes that 244 are Diet-ESP specific. Attributes that are not Diet-ESP specific are 245 already stored in some form in the SA. Such attributes are 246 designated by "Yes" in the "In SA" column. Diet-ESP specific 247 attributes may need to be specified so Diet-ESP can be executed 248 properly. 250 5.1. Diet-ESP Context Parameters for ESP 252 +-------------------+-------+--------------------------+ 253 | Context Attribute | In SA | Possible Values | 254 +-------------------+-------+--------------------------+ 255 | esp_mode | Yes | "Tunnel" or "Transport" | 256 | outer_version | Yes | "IPv4" "IPv6" | 257 | esp_spi | Yes | ESP SPI | 258 | esp_spi_lsb | No | 0, 1, 2, 3, 4 | 259 | esp_sn | Yes | ESP Sequence Number | 260 | esp_sn_lsb | No | 0, 1, 2, 3, 4 | 261 | esp_sn_gen | No | "Time", "Incremental" | 262 | esp_align | No | 8, 16, 24, 32 | 263 | esp_encr | Yes | ESP Encryption Algorithm | 264 +-------------------+-------+--------------------------+ 266 5.2. Diet-ESP Context Parameters for Inner IP 268 Parameters associated to the Inner IP addresses are only specified 269 when the SA has been configured with the tunnel mode. As a result 270 when esp_mode is set to "Transport" the parameters below MUST NOT be 271 considered and are considered as "Undefined" 273 +-------------------+-------+-----------------+ 274 | Context Attribute | In SA | Possible Values | 275 +-------------------+-------+-----------------+ 276 | ip_version | Yes | "IPv4" "IPv6" | 277 +-------------------+-------+-----------------+ 279 5.2.1. Diet-ESP Context Parameters for inner IPv6 281 +-------------------+-------+------------------------------+ 282 | Context Attribute | In SA | Possible Values | 283 +-------------------+-------+------------------------------+ 284 | ip6_tcfl_comp | No | "Outer", "Value", "UnComp" | 285 | ip6_tc | No | IPv6 Traffic Class | 286 | ip6_fl | No | IPv6 Flow Label | 287 | ip6_hl_comp | No | "Outer", "Value", "UnComp" | 288 | ip6_hl | No | Hop Limit Value | 289 | ip6_src | Yes | IPv6 Source Address | 290 | ip6_dst | Yes | IPv6 Destination Address | 291 +-------------------+-------+------------------------------+ 293 ip6_tcfl_comp indicates how Traffic Class and Flow Label fields of 294 the inner IP Header are expected to be compressed. When set to 295 "UnComp", or "Outer", values associated to ip6_tc and ip6_fl MUST NOT 296 be considered and are considered as "Undefined". Values associated 297 to ip6_tc and ip6_fl are only considered when ip6_tcfl_comp is set to 298 "Provide Values". 300 ip6_hl_comp indicates how Hop Limit field of the inner IP Header is 301 not expected to be compressed. When set to "Outer" or "UnComp", 302 values associated to ip6_hl MUST NOT be considered and is considered 303 as "Undefined". ip6_hl is only considered when ip6_hl_comp is set to 304 "Value". 306 ip6_dst designates the Destination IPv6 Address of the inner IP 307 header. The IP address is provided by the TS, and can be defined as 308 a range of IP addresses. Compression is only considered when ip6_dst 309 indicates a single IP Address. When the TS defines more than a 310 single IP address ip6_dst is considered as "Unspecified" and its 311 value MUST NOT be considered for compression. 313 5.2.2. Diet-ESP Context Parameters for inner IPv4 315 +---------------------+-------+------------------------------+ 316 | Context Attribute | In SA | Possible Values | 317 +---------------------+-------+------------------------------+ 318 | ip4_options | No | "Options", "No_Options" | 319 | ip4_id | No | IPv4 Identification | 320 | ip4_id_lsb | No | 0,1,2 | 321 | ip4_ttl_compression | No | "Outer", "Value", "UnComp" | 322 | ip4_ttl | No | IPv4 Time To Live | 323 | ip4_src | yes | IPv4 Source Address | 324 | ip4_dst | yes | IPv4 Destination Address | 325 | ip4_frag_enable | No | "True", "False" | 326 +---------------------+-------+------------------------------+ 328 5.3. Diet-ESP Context Parameters for Transport Protocol 330 The following parameters are provided by the SA but the SA may 331 specify single value or a range of values. When the SA specifies a 332 range of values, these parameters MUST NOT be considered and are 333 considered as Unspecified. 335 +-------------------+-------+------------------------------------+ 336 | Context Attribute | In SA | Possible Values | 337 +-------------------+-------+------------------------------------+ 338 | l4_proto | Yes | IPv6/ESP Next Header,IPv4 Protocol | 339 | l4_src | Yes | UDP/UDP-Lite/TCP Source Port | 340 | l4_dst | Yes | UDP/UDP-Lite/TCP Destination Port | 341 +-------------------+-------+------------------------------------+ 343 5.3.1. Diet-ESP Context Parameters for UDP-Lite 345 +-------------------+-------+-----------------------------+ 346 | Context Attribute | In SA | Possible Values | 347 +-------------------+-------+-----------------------------+ 348 | udplite_coverage | No | 8-16535, "Length", "UnComp" | 349 +-------------------+-------+-----------------------------+ 351 5.3.2. Diet-ESP Context Parameters for TCP 353 +-------------------+-------+---------------------------+ 354 | Context Attribute | In SA | Possible Values | 355 +-------------------+-------+---------------------------+ 356 | tcp_sn | No | TCP Sequence Number | 357 | tcp_ack | No | TCP Acknowledgment Number | 358 | tcp_lsb | No | 0, 1, 2, 3, 4 | 359 | tcp_options | No | "True" "False" | 360 | tcp_urgent | No | "True" "False" | 361 +-------------------+-------+---------------------------+ 363 6. Diet-ESP EHC Rules 365 This section describes the EHC Rules involved in Diet-ESP. The EHC 366 Rules defined by Diet-ESP may be used in the future by EHC Strategies 367 other than Diet-ESP, so they are described in an independent way. 369 EHC Rule defines the compression and decompression of one or more 370 fields and EHC Rules are represented this way: 372 +---------------+-------+---------+----------------+ 373 | EHC Rule | Field | Action | Parameters | 374 +---------------+-------+---------+----------------+ 375 | | f1 | a1 | p1_1, ... p1_n | 376 | +-------+---------+----------------+ 377 | EHC_RULE_NAME ~ ... ~ 378 | +-------+---------+----------------+ 379 | | fm | am | pm_1, ... pm_n | 380 +---------------+-------+---------+----------------+ 382 Figure 2: EHC Rules 384 The EHC Rule is designated by a name (EHC_RULE_NAME) which indicates 385 the concerned Fields (f1, ..., fm). Each field compression and 386 decompression is represented by an Action (a1, ..., am). Parameters 387 indicates the necessary parameters for the action to be completed, 388 i.e, to perform both the compression and the decompression. 390 The table below provides a high level description of the Actions used 391 by Diet-ESP. As these Action may take different arguments and may 392 operate differently for each field a compete description is provided 393 in the next sections as part of the EHC Rule description. 395 +-----------------+-----------------+----------------------+ 396 | Function | Compression | Decompression | 397 +-----------------+-----------------+----------------------+ 398 | send-value | No | No | 399 | elided | Not send | Get from EHC Context | 400 | lsb(_lsb_size) | Sent LSB | Get from EHC Context | 401 | lower | Not send | Get from lower layer | 402 | checksum | Not send | Compute checksum. | 403 | padding(_align) | Compute padding | Get padding | 404 +-----------------+-----------------+----------------------+ 406 a. send-value designates an action that does not perform any 407 compression or decompression of a field. 408 b. elided designates an action where both peers have a local value 409 of the field. The compression of the field consists in removing 410 the field, and the decompression consists in retrieving the field 411 value from a known local value. The local value may be stored in 412 a EHC Context or defined by the EHC Rule (like a zero value for 413 example). 414 c. lsb designates an action where both peers have a local value of 415 the field, but the compression consists in sending only the LSB 416 bytes instead of the whole field. The decompression consists in 417 retrieving the field from the LSB sent as well as some other 418 additional local values. 419 d. lower designates an action where the compression consists in not 420 sending the field. The decompression consists in retrieving the 421 field from the lower layers of the packet. A typical example is 422 when both IP and UDP carry the length of the payload, then the 423 length of the UDP payload can be inferred from the one of the IP 424 layer. 425 e. checksum designates an action where the compression consists in 426 not sending a checksum field. The decompression consists in re- 427 computing the checksum. ESP provides an integrity-check based on 428 signature of the ESP payload (ICV). This makes removing checksum 429 possible, without harming the checksum mechanism. 430 f. padding designates an action that computes the padding of the ESP 431 packet. The function is specific to the ESP. 433 For all actions, the function can be performed only when the 434 appropriated parameters and fields are provided. When a field or a 435 parameters does not have an appropriated value its value is 436 designated as "Unspecified". Specifically some fields such as inner 437 IP addresses, ports or transport protocols are agreed during the SA 438 negotiation and are specified by the SA. Their value in the SA may 439 take various values that are not appropriated to enable a 440 compression. For example, when these fields are defined as a range 441 of values, or by selectors such as OPAQUE or ANY these fields cannot 442 be retrieved from a local value. Instead, when they are defined as a 443 "Single" value (i.e a single IP address, or a single port number or a 444 single transport protocol number) compression and decompression can 445 be performed. These SA related fields are considered as 446 "Unspecified" when not limited to a "Single" value. 448 When a field or a parameter is "Unspecified", the EHC Rule MUST NOT 449 be activated. This is the purpose of the EHC Strategy to avoid 450 ending in such case. In any case, when one of these condition is not 451 met, the EHC Rule MUST NOT perform any compression or decompression 452 action and the packet MUST be discarded. When possible, an error 453 SHOULD be raised and logged. 455 6.1. EHC Rules for ESP 457 This section describes the EHC Rules for ESP which are summed up in 458 the table below. 460 +-------------+----------------+-----------+------------------------+ 461 | EHC Rule | Field | Action | Parameters | 462 +-------------+----------------+-----------+------------------------+ 463 | ESP_SPI | SPI | lsb | esp_spi_lsb, esp_spi | 464 | ESP_SN | Sequence | lsb | esp_sn_lsb, | 465 | | Number | | esp_sn_gen, esp_sn | 466 | ESP_NH | Next Header | elided | l4_proto, ipsec_mode | 467 | ESP_PAD | Pad Length, | padding | esp_align, esp_encr | 468 | | Padding | | | 469 +-------------+----------------+-----------+------------------------+ 471 ESP_SPI designates the EHC Rule compressing / decompressing the SPI. 472 ESP_SPI is performed in the "post-esp" phase. The SPI is compressed 473 using "lsb". The sending peer only places the LSB bytes of the SPI 474 and the receiving peer retrieve the SPI from the LSB bytes carried in 475 the packets as well as from the SPI value stored in the SA. The SPI 476 MUST be retrieved as its full value is included in the signature 477 check. The two peers MUST agree on the number of LSB bytes to be 478 sent: "esp_spi_lsb". Upon agreeing on "esp_spi_lsb", the receiving 479 peer MUST NOT agree on a value not carrying sufficient information to 480 retrieve the full SPI. 482 ESP_SN designates the EHC Rule compressing / decompressing the ESP 483 Sequence Number. ESP_SN is performed in the "post-esp" phase. 484 ESP_SN is only activated if the SN ("esp_sn"), the LSB significant 485 bytes ("esp_sn_lsb") and the method used to generate the SN 486 ("esp_sn_gen") are defined. The Sequence Number is compressed using 487 "lsb". Similarly to the SPI, the Sequence Number MUST be retrieved 488 in order to complete the signature check of the ESP packet. Unlike 489 the SPI, the Sequence Number is not agreed by the peers, but is 490 changing for every packet. As a result, in order to retrieve the 491 Sequence Number from the LSB "esp_sn_lsb", the peers MUST agree on 492 generating Sequence Number in a similar way. This is negotiated with 493 "esp_sn_gen" and the receiver MUST ensure that "esp_sn_lsb" is big 494 enough to absorb minor packet losses or time differences between the 495 peers. 497 ESP_NH designates the EHC Rule compressing / decompressing the ESP 498 Next Header. ESP_NH is performed in the "clear text esp" phase. 499 ESP_NH is only activated if the Next Header is specified. The Next 500 Header can be specified as IP (IPv4 or IPv6) when the IPsec tunnel 501 mode is used ("esp_mode" set to "Tunnel") or when the transport mode 502 is used when the Traffic Selectors defines a "Single" Protocol ID 503 ("l4_proto"). The Next Header, is compressed using "elided". The 504 Next Header indicates the Header in the Payload Data. When the 505 Tunnel mode is chosen, the type of the header is known to be an IP 506 header. Similarly, the TS may also hold transport layer protocol, 507 which specifies the Next Header value for Transport mode. The Next 508 Header value is only there to provide sufficient information for 509 decapsulating ESP. In other words decompressing this fields would 510 occur in the "clear text esp" phase and striped but directly removed 511 again by the ESP stack. For these reasons, implementation may simply 512 omit decompressing this field. 514 ESP_PAD designates the EHC Rule compressing / decompressing the Pad 515 Length and Padding fields. ESP_PAD is performed in the "clear text 516 exp" phase. Pad Length and Padding define the padding. The purpose 517 of padding is to respect a 32 bit alignment for ESP or block sizes of 518 the used cryptographic suite. As the ESP trailer is encrypted, 519 Padding and Pad Length MUST to be performed by ESP and not by the 520 encryption algorithm. Thus, ESP_PAD always needs to respect the 521 cipher alignment ("esp_encr"), if applicable. Compression may be 522 performed especially when device support alignment smaller than 32 523 bit. Such alignment is designated as "esp_align" and the padding 524 bytes are the necessary bytes so the ESP packet has a length that is 525 a multiple of "esp_align". 527 When "esp_align" is set to an 8-bit alignment padding bytes are not 528 necessary, and Padding as well as Pad Length are removed. For values 529 that are different from 8-bit alignment, padding bytes needs to be 530 computed according to the ESP packet length why ESP_PAD MUST be the 531 last action of "clear text esp". The resulting number of padding 532 byte is then expressed in Padding and Pad Length fields with Pad 533 Length set to padding bytes number - 1 and Padding is generated as 534 described in [RFC4303]. 536 Combining the Pad Length and Padding fields could potentially add an 537 overhead on fixed size padding. In fact some applications may only 538 send the same type of fixed size data, in which case the Pad Length 539 would not be necessary to be specified. However, the only corner 540 case Pad Length fields would actually add an overhead is when padding 541 is expected to be of zero size. In this case, specifying an 8-bit 542 alignment solve this issue. 544 6.2. EHC Rules for inner IPv4 546 All IPv4 EHC Rules MUST be performed during the "clear text esp" 547 phase. The EHC Rules are only defined for compressing the inner IPv4 548 header and thus can only be used when the SA is using the Tunnel 549 mode. 551 +---------------+-----------------+----------+--------------------+ 552 | EHC Rule | Field | Action | Parameters | 553 +---------------+-----------------+----------+--------------------+ 554 | IP4_OPT_DIS | Version | elided | ip_version | 555 | | Header Length | elided | | 556 | IP4_LENGTH | Total Length | lower | | 557 | IP4_ID | Identification | lsb | ip4_id, ip4_id_lsb | 558 | IP4_FRAG_DIS | Flags | elided | | 559 | | Fragment Offset | elided | | 560 | IP4_TTL_OUTER | Time To Live | elided | ip4-ttl | 561 | IP4_TTL_VALUE | Time To Live | elided | ip4-ttl | 562 | IP4_PROT | Protocol | elided | l4_proto | 563 | IP4_CHECK | Header Checksum | checksum | | 564 | IP4_SRC | Source Address | elided | ipv4-source | 565 | IP4_DST | Dest. Address | elided | ipv4-dest | 566 +---------------+-----------------+----------+--------------------+ 568 IP4_OPT_DIS designates that the IPv4 header does not include any 569 options and indicates if the first byte of the IPv4 header - 570 consisting of IP version and IPv4 Header Length, are compressed. The 571 Version "ip_version" is defined by the SA and is thus compressed 572 using "elided". The Header Length is static, if the header does not 573 contain any options, thus it is compressed with "elided" and 574 decompressed "20", the default length of the IPv4 header. 576 IP4_LENGTH designates the EHC Rule compressing / decompressing the 577 Total Length Field of the inner IPv4 header. The Total Length is 578 compressed by the sender and not sent. The receiver decompresses it 579 by recomputing the Total Length from the outer IP header. The outer 580 IP header can be IPv4 or IPv6 and IP4_LENGTH MUST support both 581 versions if both versions are supported by the device. Note that the 582 length of the inner IP payload may also be subject to updates if 583 decompression of the upper layers occurs. 585 IP4_ID designates the EHC Rule compressing / decompressing the 586 Identification Field. IP4_ID is only activated if the ID ("ip4_id"), 587 the LSB significant bytes ("ip4_id_lsb") are defined. Upon agreeing 588 on "ip4_id_lsb", the receiving peer MUST NOT agree on a value not 589 carrying sufficient information to retrieve the full IP 590 Identification. Note also that unlike the ESP SN, the IPv4 591 Identification is not part of the SA. As a result, when the ID is 592 compressed, its value MUST be stored in the EHC Context. The 593 reserved attribute for that is "ip4_id" 595 IP4_FRAG_DIS designates that the inner IPv4 header does not support 596 fragmentation. If activated, IP4_FRAG_DIS indicates compression of 597 Flags and Fragment Offset field in the IPv4 header which consists of 598 2 bytes. Both fields are compressed with "elided" and decompressed 599 with their default value according to [RFC0791], which is 0b010 for 600 Flags and 0 for Fragment Offset. 602 IP4_TTL_OUTER designates an EHC Rule compressing / decompressing the 603 Time To Live field of the inner IP header. IP4_TTL_OUTER is only 604 activated when both the outer and inner IP header are IPv6 header. 605 The Time To Live field is compressed / decompressed using the 606 "lower". More specifically, the field is not sent. The receiver 607 decompresses them by reading their value from the outer IPv4 header. 609 IP4_TTL_VALUE designates an EHC Rule compressing / decompressing the 610 Time To Live field of the inner IP header. IP4_TTL_VALUE is only 611 activated when the Hop Limit ("ip4_ttl") has been agreed. Time To 612 Live is compressed / decompressed using the "elided" method. 614 IP4_PROTO designates the EHC Rule compressing / decompressing the 615 Protocol field of the inner IPv4 header. IP4_PROTO is only activated 616 if the Protocol is specified, that is when the Traffic Selectors 617 defines a "Single" Protocol ID ("l4_proto"). When the Protocol ID 618 identified by the SA has a "Single" value, the Protocol is compressed 619 and decompressed using the "elided" method. 621 IP4_CHECK designates the EHC rule compressing / decompressing the 622 Header Checksum field of the inner IPv4 header. The IPv4 header 623 checksum is not sent by the sender and the receiver computes from the 624 decompressed inner IPv4 header. IP4_CHECK MUST compute the checksum 625 and not fill the checksum field with zeros. As a result, IP4_CHECK 626 is the last decompressing EHC Rule to be performed on the 627 decompressed IPv4 header. 629 IP4_SRC compresses the source IP address of the inner IPv4 header. 630 IP4_SRC_IP is only be activated when the Traffic Selectors agreed by 631 the SA defines a "Single" source IP address ("ip4_src"). The Source 632 IP address is compressed / decompressed using the "elided" method. 634 IP4_DST works in a similar way as IP4_SRC_IP but for the destination 635 IP address ("ip4_dst") 637 6.3. EHC Rules for inner IPv6 639 All IPv6 EHC Rules MUST be performed during the "clear text esp" 640 phase. The EHC Rules are only defined for compressing the inner IPv6 641 header and thus can only be used when the SA is using the Tunnel 642 mode. 644 +--------------+----------------+--------+------------+ 645 | EHC Rule | Field | Action | Parameters | 646 +--------------+----------------+--------+------------+ 647 | IP6_OUTER | Version | elided | ip_version | 648 | | Traffic Class | lower | | 649 | | Flow Label | lower | | 650 | IP6_VALUE | Version | elided | ip_version | 651 | | Traffic Class | elided | ip6_tc | 652 | | Flow Label | elided | ip6_fl | 653 | IP6_LENGTH | Payload Length | lower | | 654 | IP6_NH | Next Header | elided | l4_proto | 655 | IP6_HL_OUTER | Hop Limit | lower | | 656 | IP6_HL_VALUE | Hop Limit | elided | ip6_hl | 657 | IP6_SRC | Source Address | elided | ip6_source | 658 | IP6_DST | Dest. Address | elided | ip6_dest | 659 +--------------+----------------+--------+------------+ 661 IP6_OUTER designates an EHC Rule for compressing / decompressing the 662 first 32 bits of the inner IPv6 header formed by the Version, Traffic 663 Class and Flow Label. IP6_OUTER is only activated when both the 664 outer and inner IP header are IPv6 header. The Version "ip_version" 665 is defined by the SA and is thus compressed using "elided". The 666 other parameters Traffic Class and Flow Label are compressed using 667 "lower". More specifically, the fields are not sent. The receiver 668 decompresses them by reading their value from the outer IPv6 header. 670 IP6_VALUE designates an EHC Rule for compressing / decompressing the 671 first 32 bits of the inner IPv6 header formed by the Version, Traffic 672 Class and Flow Label. IP6_VALUE is only activated if the Version of 673 the inner IP header agreed by the SA is set to "Version 6" 674 ("ip_version" set to "Version 6") and the specific values of the 675 Traffic Class ("ip6_tc") and the Flow Label ("ip6_fl") are specified. 676 With IP6_VALUE all fields are compressed and decompressed using 677 "elided". Version is provided by the SA ("ip_version") while other 678 fields are explicitly provided (ip6_tc, ip6_fl. 680 IP6_LENGTH designates the EHC Rule compressing / decompressing the 681 Payload Length Field of the inner IPv6 header. The Payload Length is 682 compressed by the sender and is not sent. The receiver decompress it 683 by recomputing the Payload Length from the outer IP header. The IP 684 header can be IPv4 or IPv6 and IP6_LENGTH MUST support both versions 685 if both versions are supported by the device. Note that the length 686 of the inner IP payload may also be subject to updates if 687 decompression of the upper layers occurs. 689 IP6_NH designates the EHC Rule compressing / decompressing the Next 690 Header field of the inner IPv6 header. IP6_NH is only activated if 691 the Next Header is specified, that is when the Traffic Selectors 692 defines a "Single" Protocol ID ("l4_proto"). When the Protocol ID 693 identified by the SA has a "Single" value, the Next Header is 694 compressed and decompressed using the "elided" method. 696 IP6_HL_OUTER designates an EHC Rule compressing / decompressing the 697 Hop Limit field of the inner IP header. IP6_HL_OUTER is only 698 activated when both the outer and inner IP header are IPv6 header. 699 The Hop Limit field is compressed / decompressed using the "lower". 700 More specifically, the fields are not sent. The receiver 701 decompresses them by reading their value from the outer IPv6 header. 703 IP6_HL_VALUE designates an EHC Rule compressing / decompressing the 704 Hop Limit field of the inner IP header. IP6_HL_VALUE is only 705 activated when the Hop Limit ("ip6_hl") has been agreed. The Hop 706 Limit is compressed / decompressed using the "elided" method. 708 IP6_SRC compresses the source IP address of the inner IP header. 709 IP6_SRC_IP is only be activated when the Traffic Selectors agreed by 710 the SA defines a "Single" source IP address ("ip6_src"). The Source 711 IP address is compressed / decompressed using the "elided" method. 713 IP6_DST works in a similar way as IP6_SRC_IP but for the destination 714 IP address ("ip6_dst") 716 6.4. EHC Rules for UDP 718 All UDP EHC Rules MUST be performed during the "pre-esp" phase. The 719 EHC Rules are only defined when the Traffic Selectors agreed during 720 the SA negotiation results in "Single" Protocol ID ("l4_proto") which 721 is set to UDP (17). 723 +------------+--------------+----------+------------+ 724 | EHC Rule | Field | Action | Parameters | 725 +------------+--------------+----------+------------+ 726 | UDP_SRC | Source Port | elided | l4_source | 727 | UDP_DST | Dest. Port | elided | l4_dest | 728 | UDP_LENGTH | Length | lower | | 729 | UDP_CHECK | UDP Checksum | checksum | | 730 +------------+--------------+----------+------------+ 732 UDP_SRC designates the EHC Rule that compresses / decompresses the 733 UDP Source Port. UDP_SRC is only activated when the Source Port 734 agreed by the SA negotiation ("l4_src") is "Single". The Source Port 735 is then compressed / decompressed using the "elided" method. 737 UDP_DST works in a similar way as UDP_SRC but for the Destination 738 Port ("l4_dst"). 740 UDP_LENGTH designates the EHC Rule compressing / decompressing the 741 Length Field of the UDP header. The length is compressed by the 742 sender and is not sent. The receiver decompresses it by recomputing 743 the Length from the IP address header. The IP address can be IPv4 or 744 IPv6 and UDP_LENGTH MUST support both versions if both versions are 745 supported by the device. 747 UDP_CHECK designates the EHC Rule compressing / decompressing the UDP 748 Checksum. The UDP Checksum is not sent by the sender and the 749 receiver computes from the decompressed UDP payload. UDP_CHECK MUST 750 compute the checksum and not fill the checksum field with zeros. As 751 a result, UDP_CHECK is the last decompressing EHC Rule to be 752 performed on the decompressed UDP Payload. 754 6.5. EHC Rules for UDP-Lite 756 All UDP-lite EHC Rules MUST be performed during the "pre-esp" phase. 757 The EHC Rules are only defined when the Traffic Selectors agreed 758 during the SA negotiation results in a "Single" Protocol ID 759 ("l4_proto") which is set to UDPLite (136). 761 +---------------------+------------+-----------+--------------------+ 762 | EHC Rule | Field | Action | Parameters | 763 +---------------------+------------+-----------+--------------------+ 764 | UDP-LITE_SRC | Source | elided | l4_source | 765 | | Port | | | 766 | UDP-LITE_DST | Dest. Port | elided | l4_dest | 767 | UDP-LITE_COVERAGE | Checksum | elided | udplite_coverage | 768 | | Coverage | | | 769 | UDP-LITE_CHECK | UDP-Lite | checksum | | 770 | | Checksum | | | 771 +---------------------+------------+-----------+--------------------+ 773 UDP-LITE_SRC works similarly to UDP_SRC 775 UDP-LITE_DST works similarly to UDP_DST 777 UDP-LITE_COVERAGE designates the EHC Rule compressing / decompressing 778 the UDP-Lite Coverage field. UDP-LITE_COVERAGE is only activated 779 when the Coverage ("udplite_coverage") has been agreed with a valid 780 value. The Coverage is compressed / decompressed using the "elided" 781 method. 783 UDP-LITE_CHECK designates the EHC Rule compressing / decompressing 784 the UDP-Lite checksum. UDP-LITE_CHECK is only activated if the 785 Coverage is defined either elided or sent. UDP-LITE_CHECK computes 786 the checksum using "checksum" according to the uncompressed UDP 787 packet and the value of the Coverage. 789 6.6. EHC Rules for TCP 791 All TCP EHC Rules MUST be performed during the "pre-esp" phase. The 792 EHC Rules are only defined when the Traffic Selectors agreed during 793 the SA negotiation results in a"Single" Protocol ID ("l4_proto") 794 which is set to TCP (6). 796 +---------------+--------------------+--------------+---------------+ 797 | EHC Rule | Field | Action | Parameters | 798 +---------------+--------------------+--------------+---------------+ 799 | TCP_SRC | Source Port | elided | l4_source | 800 | TCP_DST | Dest. Port | elided | l4_dest | 801 | TCP_SN | Sequence Number | lsb | tcp_sn, | 802 | | | | tcp_ls | 803 | TCP_ACK | Acknowledgment | lsb | tcp_ack, | 804 | | Number | | tcp_lsb | 805 | TCP_OPTIONS | Data Offset | elided | tcp_options | 806 | | Reserved Bits | elided | | 807 | TCP_CHECK | TCP Checksum | checksum | | 808 | TCP_URGENT | elided | tcp_urgent | 809 +---------------+--------------------+--------------+---------------+ 811 TCP_SRC works similarly to UDP_SRC. 813 TCP_DST works similarly to UDP_DST. 815 TCP_SN designates the EHC Rule compressing / decompressing the TCP 816 Sequence Number. TCP_SN is only activated if the SN ("tcp_sn") and 817 the LSB significant bytes ("tcp_lsb") are defined. The TCP SN is 818 compressed using "lsb". The sending peer only places the LSB bytes 819 of the TCP SN ("tcp_sn") and the receiving peer retrieve the TCP SN 820 from the LSB bytes carried in the packets as well as from the TCP SN 821 value stored in EHC Context ("tcp_sn"). The two peers MUST agree on 822 the number of LSB bytes to be sent: "tcp_lsb". Upon agreeing on 823 "tcp_lsb", the receiving peer MUST NOT agree on a value not carrying 824 sufficient information to retrieve the full TCP SN. Note also that 825 unlike the ESP SN, the TCP SN is not part of the SA. As a result, 826 when the SN is compressed, the value of the TCP SN MUST be stored in 827 the EHC Context. The reserved attribute for that is "tcp_sn" 829 TCP_ACK designates the EHC Rule compressing / decompressing the TCP 830 Acknowledgment Number and works similarly to TCP SN. Note that 831 "tcp_lsb" is agreed for both TCP SN and TCP Acknowledgment. 832 Similarly the value of the complete TCP Acknowledgment Number MUST be 833 stored in the "tcp_ack" attribute of the EHC Context. 835 TCP_OPTIONS designates the EHC Rule compressing / decompressing TCP 836 options related fields such as Data Offset and Reserved Bits. 837 TCP_OPTION can only be activated when the TCP Option ("tcp_options") 838 is defined. When "tcp_options" is set to "False" and indicates there 839 are no TCP Options, the Data Offsets and Reserved Bits are compressed 840 / decompressed using the "elided" method with Data Offset and 841 Reserved Bits set to zero. 843 TCP_CHECK designates the EHC Rule compressing / decompressing the TCP 844 Checksum. TCP_CHECK works similarly as UDP_CHECK. 846 TCP_URGENT designates the EHC Rule compressing / decompressing the 847 urgent related information. When "tcp_urgent" is set to "False" and 848 indicates there are no TCP Urgent related information, the Urgent 849 Pointer is then "elided" and filled with zeros. 851 7. Diet-ESP EHC Strategy 853 From the attributes of the EHC Context, Diet-ESP, defines as an EHC 854 Strategy which EHC Rules to apply. The EHC Strategy is defined both 855 for outbound packets which compresses the packet as well as for 856 inbound packet where the decompression occurs. 858 Implementation may differ from the description below. However, the 859 outcome MUST remain the same. 861 7.1. Outbound Packet Processing 863 Diet-ESP compression is defined as follows: 865 1. In phase "pre-esp": Match the inbound packet with the SA and 866 determine if the Diet-ESP EHC Strategy has been activated. If 867 the Diet-ESP HEC Strategy has been activated proceed to next 868 step, otherwise skip all steps associated to Diet-ESP and proceed 869 to the standard ESP as defined in [RFC4303] 870 2. In phase "pre-esp": If "l4_proto" designates a "Single" Protocol 871 ID (UDP, TCP or UDP-Lite), proceed to the compression of the 872 specific layer. Otherwise, the transport layer is not 873 compressed. 874 3. In phase "clear text esp": If "esp_mode" is set to "Tunnel" mode, 875 determine "ip_version" the IP version of the inner IP addresses 876 and proceed to the appropriated inner IP address compression. 877 4. In phase "clear text esp" and "post-esp": Proceed to the ESP 878 compression. 880 UDP compression is defined as below: 882 1. If the "l4_src" designates a "Single" Source Port, apply UDP_SRC 883 to compress the Source Port. 884 2. If the "l4_dst" designates a "Single" Destination Port, apply 885 UDP_DST to compress the Destination Port. 886 3. Apply UDP_CHECK to compress the Checksum. 887 4. Apply UDP_LENGTH to compress the Length. 889 UDP-lite compression is defined as below: 891 1. If the "l4_src" designates a "Single" Source Port, apply the UDP- 892 LITE_SRC to compress the Source Port. 893 2. If the "l4_dst" designates a "Single" Destination Port, apply the 894 UDP-LITE_DST, to compress the Destination Port. 895 3. If "udplite_coverage" is specified, apply the UDP-LITE_COVERAGE, 896 to compress the Coverage. 897 4. Apply UDP-LITE_CHECK to compress the Checksum. 899 TCP compression is defined as below: 901 1. If the "l4_src" designates a "Single" Source Port than apply the 902 TCP_SRC to compress the Source Port. 903 2. If the "l4_dst" designates a "Single" Destination Port than apply 904 the TCP_DST to compress the Destination Port. 905 3. If "tcp_lsb" is lower than 4, then "tcp_sn" "tcp_ack" attributes 906 of the Diet-ESP Context are updated with the value provided from 907 the packet before applying the TCP_SN and the TCP_ACK EHC Rules. 908 4. If "tcp_options" is set to "False" apply the TCP_OPTIONS EHC 909 Rule. 910 5. If "tcp_urgent" is set to "False" apply the TCP_URGENT EHC Rule. 911 6. Apply TCP_CHECK to compress the Checksum. 913 Inner IPv6 Header compression is defined as below: 915 1. If the "ip6_src" designates a "Single" Source IP address, apply 916 the IP6_SRC to compress the IPv6 Source Address. 917 2. If the "ip6_dst" designates a "Single" Destination IP address, 918 apply the IP6_DST to decompress the IPv6 Destination Address. 919 3. Hop Limit compression is performed as follows: 921 1. If "outer_version" is set to "IPv6" and "ip6_hl_comp" is set 922 to "Outer" apply IP6_HL_OUTER. 923 2. If "outer_version" is set to "IPv4" and "ip6_hl_comp" is set 924 to "Outer" raise an error and discard the packet. 925 3. If "ip6_hl_comp" is set to "Value" apply IP6_HL_VALUE. 926 4. If "l4_proto" designates a "Single" Protocol ID (UDP, TCP or UDP- 927 Lite), apply IP6_NH to compress the Next Header. 928 5. Apply, IP6_LENGTH to compress the Length. 929 6. Version, Traffic Class and Flow Label are compressed as follows: 931 1. If "outer_version" is set to "IPv6" and "ip6_tcfl_comp" is 932 set to "Outer" apply IP6_OUTER. 933 2. If "outer_version" is set to "IPv4" and "ip6_tcfl_comp" is 934 set to "Outer" raise an error and discard the packet. 935 3. If "ip6_tcfl_comp" is set to "Value" apply IP6_VALUE. 937 ESP compression is defined as below: 939 1. In phase "clear text esp": If "esp_mode" is set to "Tunnel" or 940 "l4_proto" is set to a "Single value - eventually different from 941 TCP, UDP or UDP-Lite, apply ESP_NH, to compress the Next Header. 942 2. In phase "clear text esp": If "esp_encr" specify an encryption 943 algorithm that does not provide padding, then apply ESP_ALIGN to 944 compress the Pad Length and Padding. 945 3. Proceed to the ESP encryption as defined in [RFC4303]. 946 4. In phase "post-esp: If "esp_sn_lsb" is different from 4, then 947 apply ESP_SN. To compress the ESP SN. 948 5. In phase "post-esp": If "esp_spi_lsb" is different from 4, then 949 apply ESP_SPI to compress the SPI. 951 7.2. Inbound Packet Processing 953 Diet-ESP decompression is defined as follows: 955 1. Match the inbound packet with the SA and determine if the Diet- 956 ESP EHC Strategy has been activated. When Diet-ESP is activated 957 this means that the "esp_spi_lsb" are sufficient to index the SA 958 and proceed to next step, otherwise skip all steps associated to 959 Diet-ESP and proceed to the standard ESP as defined in [RFC4303] 960 2. In phase "clear text esp" and "post-esp": Proceed to the ESP 961 decompression. 962 3. In phase "clear text esp": If "esp_mode" is set to "Tunnel" mode, 963 determine "ip_version" the IP version of the inner IP addresses 964 and proceed to the appropriated inner IP address decompression, 965 except for the computation of the checksums and length. 966 4. In phase "pre-esp": If "l4_proto" designates a "Single" Protocol 967 ID (UDP, TCP or UDP-Lite), proceed to the decompression of the 968 specific layer, except for the computation of the checksums and 969 length replaced by zero fields. 970 5. In phase "pre-esp": Proceed to the decompression of the checksums 971 and length. 973 ESP decompression is defined as follows: 975 1. In phase "post-esp": If "esp_spi_lsb" is different from 4, then 976 apply ESP_SPI to decompress the SPI. 977 2. In phase "post-esp: If "esp_sn_lsb" is different from 4, then 978 apply ESP_SN. To decompress the ESP SN. 979 3. Proceed to the ESP signature validation and decryption as defined 980 in [RFC4303]. 981 4. In phase "clear text esp": If "esp_mode" is set to "Tunnel" or 982 "l4_proto" is set to a "Single value - eventually different from 983 TCP, UDP or UDP-Lite, apply ESP_NH, to decompress the Next 984 Header. 986 5. In phase "clear text esp": If "esp_encr" specify an encryption 987 algorithm that does not provide padding, then apply ESP_ALIGN to 988 compress the Pad Length and Padding. 989 6. Extract the ESP Data Payload and apply decompression EHC Rule to 990 the ESP Data Payload. 992 Inner IPv6 decompression is defined as follows: 994 1. Version, Traffic Class and Flow Label are decompressed as 995 follows: 997 1. If "outer_version" is set to "IPv6" and "ip6_tcfl_comp" is 998 set to "Outer" apply IP6_OUTER to decompress Version, Traffic 999 Class and Flow Label. 1000 2. If "outer_version" is set to "IPv4" and "ip6_tcfl_comp" is 1001 set to "Outer" raise an error and discard the packet. 1002 3. If "ip6_tcfl_comp" is set to "Value" apply IP6_VALUE to 1003 Version, Traffic Class and Flow Label. 1004 4. If "ip6_tcfl_comp" is set to "UnComp", Version, Traffic Class 1005 and Flow Label are already provided in the packet. 1006 2. Set the Length to zero. 1007 3. If "l4_proto" designates a "Single" Protocol ID (UDP, TCP or UDP- 1008 Lite), apply IP6_NH to decompress the Next Header. 1009 4. Hop Limit decompression is performed as follows: 1011 1. If "outer_version" is set to "IPv6" and "ip6_hl_comp" is set 1012 to "Outer" apply IP6_HL_OUTER to decompress Hop Limit. 1013 2. If "outer_version" is set to "IPv4" and "ip6_hl_comp" is set 1014 to "Outer" raise an error and discard the packet. 1015 3. If "ip6_hl_comp" is set to "Value" apply IP6_HL_VALUE to 1016 decompress the Hop Limit. 1017 4. If "ip6_hl_comp" is set to "UnComp", Hop Limit is already 1018 provided in the packet. 1019 5. If the "ip6_src" designates a "Single" Source IP address, apply 1020 the IP6_SRC to de compress the IPv6 Source Address. 1021 6. If the "ip6_dst" designates a "Single" Destination IP address 1022 than apply the IP6_DST to decompress the IPv6 Destination 1023 Address. 1024 7. Apply, IP6_LENGTH to provide the replace the zero length value by 1025 its appropriated appropriated value. The Length value considers 1026 the length provided by the lower layers to which are added the 1027 additional bytes due to the decompression, minus the length of 1028 the inner IP6 Header. The value computed from the lower layer 1029 will have to be overwritten in case further decompression occurs. 1031 UDP decompression is defined as follows: 1033 1. If the "l4_src" designates a "Single" Source Port, apply UDP_SRC 1034 to decompress the Source Port. 1035 2. If the "l4_dst" designates a "Single" Destination Port, apply 1036 UDP_DST to decompress the Destination Port. 1037 3. Apply UDP_LENGTH to compress the Length. The length value is 1038 computed from the length provided by the lower layer, with the 1039 additional added bytes during the UDP decompression including the 1040 length size. 1041 4. Apply UDP_CHECK to decompress the Checksum. 1042 5. Update the Length of the lower layers: 1044 1. If "esp_mode" is set to "Transport" mode, update the Length 1045 of the outer IP header (IPv4 or IPv6). The Length is 1046 incremented by the number of bytes generated by the 1047 decompression of the transport layer. 1048 2. If "esp_mode" is set to "Tunnel" mode, update the Length of 1049 the inner IP address (IPv4 or IPv6) as well as the outer IP 1050 header (IPv4 or IPv6). The Length is incremented by the 1051 number of bytes generated by the decompression of the 1052 transport layer. 1054 UDP-Lite decompression is defined as follows: 1056 1. If the "l4_src" designates a "Single" Source Port, apply the UDP- 1057 LITE_SRC to decompress the Source Port. 1058 2. If the "l4_dst" designates a "Single" Destination Port, apply the 1059 UDP-LITE_DST, to decompress the Destination Port. 1060 3. If "udplite_coverage" is specified, apply the UDP-LITE_COVERAGE, 1061 to decompress the Coverage. 1062 4. Apply UDP-LITE_CHECK to compress the Checksum. 1063 5. Update the Length of the lower layers as defined in UDP. 1065 TCP decompression is defined as follows: 1067 1. If the "l4_src" designates a "Single" Source Port than apply the 1068 TCP_SRC to decompress the Source Port. 1069 2. If the "l4_dst" designates a "Single" Destination Port than apply 1070 the TCP_DST to decompress the Destination Port. 1071 3. If "tcp_lsb" is lower than 4, apply TCP_SN and the TCP_ACK to 1072 decompress the TCP Sequence Number and the TCP Acknowledgment 1073 Number. 1074 4. If "tcp_options" is set to "False" apply TCP_OPTIONS to 1075 decompress Data Offset and Reserved Bits. 1076 5. If "tcp_urgent" is set to "False" apply the TCP_URGENT to 1077 decompress the Urgent Pointer. 1078 6. Apply TCP_CHECK to decompress the Checksum. 1080 8. IANA Considerations 1082 There are no IANA consideration for this document. 1084 9. Security Considerations 1086 This section lists security considerations related to the Diet-ESP 1087 protocol. 1089 Security Parameter Index (SPI): 1090 The Security Parameter Index (SPI) is used by the receiver to 1091 index the Security Association that contains appropriated 1092 cryptographic material. If the SPI is not found, the packet is 1093 rejected as no further checks can be performed. In EHC, the value 1094 of the SPI is not reduced, but compressed why the SPI value may 1095 not be fully provided between the compressor and the de- 1096 compressor. On the other hand, its uncompressed value is provided 1097 to the ESP-procession and no weakness is introduced to ESP itself. 1098 On an implementation perspective, it is strongly recommended that 1099 decompression is deterministic. Compression and decompression 1100 adds some additional treatment to the ESP packet, which might be 1101 used by an attacker. In order to minimize the load associated to 1102 decompression, decompression is expected to be deterministic. The 1103 incoming compressed SPI with the associated IP addresses should 1104 output a single and unique uncompressed SPI value. If an 1105 uncompressed SPI values have to be considered, then the receiver 1106 could end in n signature checks which may be used by an attacker 1107 for a DoS attack. 1108 Sequence Numer (SN): 1109 The Sequence Number (SN) is used as an anti-replay attack 1110 mechanism. Compression and decompression of the SN is already 1111 part of the standard ESP namely the Extended Sequence Number 1112 (ESN). The SN in a standard ESP packet is 32 bit long, whether 1113 EHC enables to reduce it to 0 bytes and the main limitation to the 1114 compression a deterministic decompression. SN compression 1115 consists in indicating the least significant bits of the 1116 uncompressed SN on the wire. The size of the compressed SN must 1117 consider the maximum reordering index such that the probability 1118 that a later sent packet arrives before an earlier one. In 1119 addition the size of SN should also consider maximum consecutive 1120 packets lost during transmission. In the case of ESP, this number 1121 is set to 2^32 which is, in most real world case, largely over- 1122 provisioned. When the compression of the SN is not appropriately 1123 provisioned, the most significant bit value may be de-synchronized 1124 between the sending and receiving parties. Although IKEv2 1125 provides some re-synchronization mechanisms, in case of IoT the 1126 de-synchronization will most likely result in a renegotiation and 1127 thus DoS possibilities. Note that IoT communication may also use 1128 some external parameters, i.e. other than the compressed SN, to 1129 define whether a packet be considered or not and eventually derive 1130 the SN. One such scenario may be the use of time windows. 1131 Suppose a device is expected to send some information every hour 1132 or every week. In this case, for example, the SN may be 1133 compressed to zero bytes. Instead the SN may be derived by 1134 incrementing the SN every hour after the last received valid 1135 packet. Considering the time the packet is received make it 1136 possible to consider the time derivation of the sensor clock. If 1137 TIME is used as the method to generate the SN, the receiver MUST 1138 ensure that the esp_sn_lsb is big enough to resist time 1139 differences between the nodes. Note also that the anti-replay 1140 mechanism needs to define the size of the anti-replay 1141 window.[RFC4303] provides guidance to set the window size and are 1142 similar to those used to define the size of the compressed SN. 1144 10. Privacy Considerations 1146 Security Parameter Index (SPI): 1147 Until Diet-ESP is not deployed outside the scope of IoT and small 1148 devices, the use of a compressed SPI may provide an indication 1149 that one of the endpoint is a sensor. Such information may be 1150 used, for example, to evaluate the number of appliances deployed, 1151 or - in addition with other information, such as the time 1152 interval, the geographic location - be used to derive the type of 1153 data transmitted. 1154 Sequence Number (SN): If incremented for each ESP packet, the SN may 1155 leak some information like the amount of transmitted data or the 1156 age of the sensor. The age of the sensor may be correlated with 1157 the software used and the potential bugs. On the other hand, re- 1158 keying will re-initialize the SN, but the cost of a re-keying may 1159 not be negligible and thus, frequent re-keying can be considered. 1160 In addition to the re-key operation, the SN may be generated in 1161 order to reduce the accuracy of the information leaked. In fact, 1162 the SN does not have to be incremented by one for each packet it 1163 just has to be an increasing function. Using a function such as a 1164 TIME may prevent characterizing the age or the use of the sensor. 1165 Note that the use of such function may also impact the compression 1166 efficiency and result in larger compressed SN. 1168 11. Acknowledgment 1169 We thank Orange and Universitee Pierre et Marie Curie for initiating 1170 the work on Diet-ESP. We Would like to thank Sylvain Killian for 1171 implementing an open source Diet-ESP on Contiki and testing it on the 1172 FIT IoT-LAB [fit-iot-lab] funded by the French Ministry of Higher 1173 Education and Research. We thank the IoT-Lab Team and the INRIA for 1174 maintaining the FIT IoT-LAB platform and for providing feed backs in 1175 an efficient way. 1177 We would like to thank Rob Moskowitz for not copyrighting Diet HIP. 1178 The "Diet" terminology is from him. 1180 We woudl like to thank those we received many useful feed backs among 1181 others: Dominique Bartel, Anna Minaburo, Suresh Krishnan, Samita 1182 Chakrabarti, Michael Richarson, Tero Kivinen. 1184 12. References 1186 12.1. Normative References 1188 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 1189 10.17487/RFC0791, September 1981, 1190 . 1192 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1193 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 1194 RFC2119, March 1997, 1195 . 1197 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 1198 4303, DOI 10.17487/RFC4303, December 2005, 1199 . 1201 [RFC4309] Housley, R., "Using Advanced Encryption Standard (AES) CCM 1202 Mode with IPsec Encapsulating Security Payload (ESP)", RFC 1203 4309, DOI 10.17487/RFC4309, December 2005, 1204 . 1206 [RFC5225] Pelletier, G. and K. Sandlund, "RObust Header Compression 1207 Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and 1208 UDP-Lite", RFC 5225, DOI 10.17487/RFC5225, April 2008, 1209 . 1211 [RFC5858] Ertekin, E., Christou, C., and C. Bormann, "IPsec 1212 Extensions to Support Robust Header Compression over 1213 IPsec", RFC 5858, DOI 10.17487/RFC5858, May 2010, 1214 . 1216 12.2. Informational References 1218 [I-D.toutain-6lpwa-ipv6-static-context-hc] 1219 Minaburo, A. and L. Toutain, "6LPWA Static Context Header 1220 Compression (SCHC) for IPV6 and UDP", draft-toutain-6lpwa- 1221 ipv6-static-context-hc-01 (work in progress), June 2016. 1223 [I-D.mglt-ipsecme-implicit-iv] 1224 Migault, D., Guggemos, T., and Y. Nir, "Implicit IV for 1225 Counter-based Ciphers in IPsec", draft-mglt-ipsecme- 1226 implicit-iv-01 (work in progress), October 2016. 1228 [fit-iot-lab] 1229 , "Future Internet of Things (FIT) IoT-LAB", . 1232 Appendix A. Illustrative Examples 1234 A.1. Single UDP Session IoT VPN 1236 This section considers a IoT IPv6 probe hosting a UDP application. 1237 The probe is dedicated to a single application and establishes a 1238 single UDP session. As a result, inner IP addresses and UDP Ports 1239 have a "Single" value and can be easily compressed. The probes sets 1240 an IPsec VPN using IPv6 addresses in order to connect its secure 1241 domain - typically a Home Gateway. The use of IPv6 for inner and 1242 outer IP addresses, enables to infer inner IP fields from the outer 1243 IP address. The probes encrypts with AES-CCM_8 [RFC4309]. AES-CCM 1244 does not have padding, so the padding is performed by ESP. The 1245 probes uses an 8 bit alignment which enables to fully compress the 1246 ESP Trailer. In addition, as the probe SA is indexed using the outer 1247 IP addresses (or eventually the radio identifiers) which enables to 1248 fully compress the SPI. As the probe provides information every 1249 hour, the Sequence Number using time can be derived from the received 1250 time, which enables to fully compress the SN. 1252 Figure 3 represents the original UDP packet and Figure 4 represents 1253 the corresponding packet compressed with Diet-ESP. The compression 1254 with Diet-ESP results in a reduction of 61 bytes overhead. With IPv4 1255 inner IP addressed Diet-ESP results in an 45 byte overhead reduction. 1257 Further compression may be done for example by using an implicit IV 1258 [I-D.mglt-ipsecme-implicit-iv] and by compressing the outer IP 1259 addresses (not represented) on the figure. In addition, application 1260 data may also be compressed with mechanisms outside of the scope of 1261 Diet-ESP. 1263 0 1 2 3 1264 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 1265 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--- 1266 E| Security Parameters Index (SPI) | ^ 1267 S+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1268 P| Sequence Number (SN) | | 1269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1270 | | | 1271 | IV | | 1272 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- | 1273 I|version| traffic class | flow label |^ | 1274 P+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1275 v| payload length | next header | hop limit || | 1276 6+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1277 | || a 1278 | inner source IP || u 1279 | |e t 1280 | |n h 1281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+c e 1282 | |r n 1283 | inner destination IP |y t 1284 | |p i 1285 | |t c 1286 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+e a 1287 U| source port | dest port |d t 1288 D+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| e 1289 P| length | checksum || d 1290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1291 | || | 1292 ~ APPLICATION DATA ~| | 1293 | || | 1294 -| +-+-+-+-+-+-+-+-+| | 1295 E| | Padding || | 1296 S+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1297 P| Padding (continue) | Pad Length | Next Header |v v 1298 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--- 1299 | Integrity Check Value-ICV (variable) | 1300 | | 1301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1303 Figure 3: Standard ESP VPN Packet Description 1305 0 1 2 3 1306 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 1307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- 1308 | | ^ 1309 | IV | | 1310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ aut 1311 | | hen 1312 ~ APPLICATION DATA ~ tic 1313 | (encrypted) | ate 1314 | +-+-+-+-+-+-+-+-+ | 1315 | | | V 1316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |-- 1317 | Integrity Check Value-ICV (variable) | 1318 | +-+-+-+-+-+-+-+-+ 1319 | | 1320 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1322 Figure 4: Diet-ESP Single UDP Session IoT VPN Packet Description 1324 The following table illustrates the activated rules and the 1325 attributes of the Diet-ESP Context that needs an explicit agreement 1326 to achieve the compression. All other attributes used by the rules 1327 are part of the SA agreement. Parameters of not activated rules are 1328 left "Unspecified". 1330 +--------------+-------------------+---------------+ 1331 | EHC Rule | Context Attribute | Value | 1332 +--------------+-------------------+---------------+ 1333 | ESP_SPI | esp_spi_lsb | 0 | 1334 | ESP_SN | esp_sn_lsb | 0 | 1335 | | esp_sn_gen | "Incremental" | 1336 | ESP_NH | | | 1337 | ESP_PAD | esp_align | 8 | 1338 | | | | 1339 | IP6_OUTER | ip6_tcfl_comp | "Outer" | 1340 | | ip6_hl_comp | "Outer" | 1341 | IP6_LENGTH | | | 1342 | IP6_NH | | | 1343 | IP6_HL_OUTER | | | 1344 | IP6_SRC | | | 1345 | IP6_DST | | | 1346 | | | | 1347 | UDP_SRC | | | 1348 | UDP_DST | | | 1349 | UDP_LENGTH | | | 1350 | UDP_CHECK | | | 1351 +--------------+-------------------+---------------+ 1353 A.2. Single TCP session IoT VPN 1354 This section considers the same probe as described in Appendix A.1 1355 but instead of using UDP as a transport layer, the probe uses TCP. 1356 In this case TCP is used with no options, no urgent pointers and the 1357 SN and ACK Number are compressed to 2 bytes as the throughput is 1358 expected to be low. 1360 Figure 5 represents the original TCP packet and Figure 6 represents 1361 the corresponding packet compressed with Diet-ESP. The compression 1362 with Diet-ESP results in a reduction of 66 bytes overhead. With IPv4 1363 inner address Diet-ESP results in a 50 byte overhead reduction. 1365 0 1 2 3 1366 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 1367 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--- 1368 E| Security Parameters Index (SPI) | ^ 1369 S+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1370 P| Sequence Number (SN) | | 1371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1372 | | | 1373 | IV | | 1374 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- | 1375 I|version| traffic class | flow label |^ | 1376 P+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1377 v| payload length | next header | hop limit || | 1378 6+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1379 | || a 1380 | inner source IP || u 1381 | |e t 1382 | |n h 1383 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+c e 1384 | |r n 1385 | inner destination IP |y t 1386 | |p i 1387 | |t c 1388 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+e a 1389 T| source port | dest port |d t 1390 C+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| e 1391 P| Sequence Number (SN) || d 1392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1393 | ACK Sequence Number || | 1394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1395 |Off. | Rserv | Flags | Window Size || | 1396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1397 | Checksum | Urgent Pointer || | 1398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1399 | || | 1400 ~ APPLICATION DATA ~| | 1401 | || | 1402 | +-+-+-+-+-+-+-+-+| | 1403 E| | Padding || | 1404 S+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1405 P| Padding (continue) | Pad Length | Next Header |V V 1406 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--- 1407 | Integrity Check Value-ICV (variable) | 1408 | | 1409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1411 Figure 5: Standard IoT Single TCP Session VPN Packet Description 1413 0 1 2 3 1414 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 1415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---a 1416 | | ^u 1417 | IV | |t 1418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--|h 1419 | Sequence Number (SN) | ACK Sequence Number |^e|e 1420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|n|n 1421 | Flags | Window Size | ||c|t 1422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ||r|i 1423 | ~|y|c 1424 ~ APPLICATION DATA ||p|a 1425 | ||t|t 1426 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|e|e 1427 | | |vdvd 1428 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |--- 1429 | Integrity Check Value-ICV (variable) | 1430 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1431 | | 1432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1434 Figure 6: Diet-ESP Single TCP Session IoT VPN Packet Description 1436 The following table illustrates the activated rules and the 1437 attributes of the Diet-ESP Context that needs an explicit agreement 1438 to achieve the compression. All other attributes used by the rules 1439 are part of the SA agreement. Parameters of not activated rules are 1440 left "Unspecified". Note for simplicity, tcp_sn and tcp_ack are 1441 negotiated to start with 0, but it could be any other value as well. 1443 +--------------+-------------------+---------------+ 1444 | EHC Rule | Context Attribute | Value | 1445 +--------------+-------------------+---------------+ 1446 | ESP_SPI | esp_spi_lsb | 0 | 1447 | ESP_SN | esp_sn_lsb | 0 | 1448 | | esp_sn_gen | "Incremental" | 1449 | ESP_NH | | | 1450 | ESP_PAD | esp_align | 8 | 1451 | | | | 1452 | IP6_OUTER | ip6_tcfl_comp | "Outer" | 1453 | | ip6_hl_comp | "Outer" | 1454 | IP6_LENGTH | | | 1455 | IP6_NH | | | 1456 | IP6_HL_OUTER | | | 1457 | IP6_SRC | | | 1458 | IP6_DST | | | 1459 | | | | 1460 | TCP_SRC | | | 1461 | TCP_DST | | | 1462 | TCP_SN | tcp_lsb | 2 | 1463 | | tcp_sn | 0 | 1464 | TCP_ACK | tcp_lsb | 2 | 1465 | | tcp_ack | 0 | 1466 | TCP_OPTIONS | tcp_options | "False" | 1467 | TCP_CHECK | | | 1468 | TCP_URGENT | tcp_urgent | "False" | 1469 +--------------+-------------------+---------------+ 1471 A.3. Traditional VPN 1473 This section illustrates the case of an company VPN. The VPN is 1474 typically set by a remote host that forwards all its traffic to the 1475 security gateway. As transport protocols are "Unspecified", 1476 compression is limited to ESP and the inner IP header. For the inner 1477 IP header, the Destination IP address is "Unspecified" so the 1478 compression of the inner IP address excludes the Destination IP 1479 address. Similarly, the inner IP Next Header cannot be compressed as 1480 the transport layer is not specified. For ESP, the security gateway 1481 may only have a sufficiently low number of remote users with 1482 relatively low throughput in which case SPI and SN can be compressed 1483 to 2 bytes. As throughput remains relatively low, the alignment may 1484 also set to 8 bits. 1486 Figure 7 represents the original TCP packet with IPv6 inner IP 1487 addresses and Figure 8 represents the corresponding packet compressed 1488 with Diet-ESP. The compression with Diet-ESP results in a reduction 1489 of 32 bytes overhead. For IPv4 compression results in a 24 byte 1490 overhead compression. 1492 0 1 2 3 1493 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 1494 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--- 1495 E| Security Parameters Index (SPI) | ^ 1496 S+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1497 P| Sequence Number (SN) | | 1498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1499 | | | 1500 | IV | | 1501 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- | 1502 I|version| traffic class | flow label |^ | 1503 P+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1504 v| payload length | next header | hop limit || | 1505 6+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1506 | || a 1507 | inner source IP || u 1508 | |e t 1509 | |n h 1510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+c e 1511 | |r n 1512 | inner destination IP |y t 1513 | |p i 1514 | |t c 1515 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+e a 1516 T| source port | dest port |d t 1517 C+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| e 1518 P| Sequence Number (SN) || d 1519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1520 | ACK Sequence Number || | 1521 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1522 |Off. | Rserv | Flags | Window Size || | 1523 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1524 | Checksum | Urgent Pointer || | 1525 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1526 | || | 1527 ~ APPLICATION DATA ~| | 1528 | || | 1529 -| +-+-+-+-+-+-+-+-+| | 1530 E| | Padding || | 1531 S+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| | 1532 P| Padding (continue) | Pad Length | Next Header |V V 1533 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--- 1534 | Integrity Check Value-ICV (variable) | 1535 | | 1536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1538 Figure 7: Standard ESP VPN Packet Description 1540 0 1 2 3 1541 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 1542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--- 1543 | SPI | SN | ^ 1544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1545 | | | 1546 | IV | | 1547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--| 1548 | Next Header | |^ | 1549 +-+-+-+-+-+-+-+-+ || | 1550 | || | 1551 | inner destination IP || | 1552 | || |a 1553 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| |u 1554 | | source port | dest. port ~|e|t 1555 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|n|h 1556 ~ (continue) | TCP Sequence Number (SN) ~|c|e 1557 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|r|n 1558 ~ (continue) | Sequence Number (SN) ~|y|t 1559 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|p|i 1560 ~ (continue) |Off. | Rserv | Flags | Window Size ~|t|c 1561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|e|a 1562 ~ (continue) | Checksum | Urgent ~|d|t 1563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| |e 1564 ~ Pointer | || |d 1565 +-+-+-+-+-+-+-+-+ || | 1566 ~ APPLICATION DATA ~| | 1567 | || | 1568 | |v v 1569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--- 1570 | Integrity Check Value-ICV (variable) | 1571 | | 1572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1574 Figure 8: Diet-ESP VPN Packet Description 1576 The following table illustrates the activated rules and the 1577 attributes of the Diet-ESP Context that needs an explicit agreement 1578 to achieve the compression. All other attributes used by the rules 1579 are part of the SA agreement. Parameters of not activated rules are 1580 left "Unspecified". 1582 +--------------+-------------------+---------------+ 1583 | EHC Rule | Context Attribute | Value | 1584 +--------------+-------------------+---------------+ 1585 | ESP_SPI | esp_spi_lsb | 2 | 1586 | ESP_SN | esp_sn_lsb | 2 | 1587 | | esp_sn_gen | "Incremental" | 1588 | ESP_NH | | | 1589 | ESP_PAD | esp_align | 8 | 1590 | | | | 1591 | IP6_OUTER | ip6_tcfl_comp | "Outer" | 1592 | | ip6_hl_comp | "Outer" | 1593 | IP6_LENGTH | | | 1594 | IP6_HL_OUTER | | | 1595 | IP6_SRC | | | 1596 +--------------+-------------------+---------------+ 1598 Appendix B. EHC Classification (Informative) 1600 EHC Rules for Header fields depends on the property of the given 1601 field. The complete classification for all supported protocols is 1602 provided in Appendix B The current classification is based on the 1603 classification provided by ROHC (see Appendix A of [RFC5225]). 1604 However, as EHC agrees on a context out of band, not all 1605 classifications provided by ROHC are necessary and classification may 1606 end up differently. 1608 A key difference between ROHC and ESP Header Compression is that ESP 1609 needs an explicit agreement between the peers, whereas ROHC does not 1610 proceed to any out-of-band agreement. Instead ROHC learns some 1611 values by reading them from an initial packet. This learning phase 1612 is not anymore needed with ESP Header Compression as these fields can 1613 be agreed. For that reason fields classified as STATIC-DEF by ROHC 1614 becomes classified as STATIC-KNOWN for ESP Header Compression. In 1615 addition, the EHC classification also differs from the ROHC 1616 classification as EHC may be able to segment classes according to the 1617 ESP context. In that sense, EHC does not consider a single class - 1618 which is the one with the least constraints, as ROHC does. Instead, 1619 the EHC classification intends to associate the different classes to 1620 the ESP context. 1622 EHC requires these four classes, in order to classify the different 1623 header fields: 1625 STATIC-KNOWN These fields are expected to remain constant throughout 1626 the lifetime of the flow. As a result, they can be negotiated 1627 out of band and stored in a context. 1628 INFERRED These fields contain values that can be inferred from other 1629 values, for example the size of the frame carrying the packet, 1630 and thus do not have to be included in compressed packets. 1631 PATTERN These are fields that change between each packet, but change 1632 in a predictable pattern. 1633 IRREGULAR These are the fields for which no useful change pattern 1634 can be identified and should be transmitted uncompressed in all 1635 compressed packets. 1637 This section details the classification for the currently supported 1638 protocol fields. Bbeing ESP encapsulated, a given field may end up 1639 with a different classification than without encapsulation. In order 1640 to point out these differences, this section also provides for 1641 information the classification provided by ROHC. In addition, given 1642 the context associated to ESP, a given field may be classified 1643 differently. In that case, the multiple classifications are 1644 mentioned. 1646 B.1. ESP 1648 This section provides a EHC classification for the fields of the ESP 1649 protocol. 1651 +-----------------------+---------------------------+------------+ 1652 | Field | EHC Class | ROHC class | 1653 +-----------------------+---------------------------+------------+ 1654 | Security Policy Index | STATIC-KNOWN | STATIC-DEF | 1655 | Sequence Number | PATTERN | PATTERN | 1656 | Padding | INFERRED / STATIC-KNOWN | | 1657 | Pad Length | INFERRED / STATIC-KNOWN | | 1658 | Next Header | STATIC-KNOWN / IRREGULAR | | 1659 +-----------------------+---------------------------+------------+ 1661 Fields Padding, Pad Length, Next Header were not classified by ROHC 1662 because, they could not be compressed by either ROHCoverIPsec or 1663 ROHC. ROHCoverIPsec compresses protocols encapsulated by ESP. These 1664 fields are part of ESP and so cannot be compressed by ROHCoverIPsec. 1665 ROHC compresses fields sent on the wire but these fields are 1666 encrypted by ESP and so cannot be compressed by ROHC. 1668 In EHC, when present, Padding and Pad Length are INFERRED from the 1669 necessary protocol alignment, the cipher alignment and the ESP packet 1670 length before the encryption occurs. For packet with fixed size, 1671 these values will not changed during the session and as a result, may 1672 be classified as STATIC-KNOWN. Similarly, for some specific 1673 alignment values, such as 8 bit alignment, these fields may also have 1674 fixed values and thus may be classified as STATIC-KNOWN too. 1676 Next Header is STATIC-KNOWN when it is part of the TS, in which case 1677 it has been agreed between the peers. Otherwise, NH is IRREGULAR and 1678 thus cannot be compressed. 1680 B.2. IPv6 (Inner) 1682 This section provides a EHC classification for the fields of the IPv6 1683 protocol. The IPv6 address only considers the inner IP header when 1684 used in conjunction of the tunnel mode. 1686 +-------------------+--------------------------+--------------------+ 1687 | Field | EHC Class | ROHC class | 1688 +-------------------+--------------------------+--------------------+ 1689 | Version | STATIC-KNOWN | STATIC-KNOWN | 1690 | Traffic Class | STATIC-KNOWN / INFERRED | RACH | 1691 | | / IRREGULAR | | 1692 | Flow Label | STATIC-KNOWN / INFERRED | STATIC-DEF | 1693 | | / IRREGULAR | | 1694 | Payload Length | INFERRED | INFERRED | 1695 | Next Header | STATIC-KNOWN / IRREGULAR | STATIC-DEF | 1696 | Hop Limit | STATIC-KNOWN / INFERRED | RACH | 1697 | Source Address | STATIC-KNOWN | STATIC-DEF | 1698 | Destination | STATIC-KNOWN | STATIC-DEF | 1699 | Address | | | 1700 +-------------------+--------------------------+--------------------+ 1702 Traffic Class, Flow Label, Hop Limit are STATIC-KNOWN when part of 1703 the TS, in which case it has been agreed between the peers in the EHC 1704 context. Alternatively, the inner IPv6 header is INFERRED from the 1705 outer IP header if the outer IP header is an IPv6 header. In any 1706 other cases, these fields are IRREGULAR. 1708 Next Header is STATIC-KNOWN when it is part of the TS, in which case 1709 it has been agreed between the peers. Otherwise, NH is IRREGULAR and 1710 thus cannot be compressed. 1712 B.3. IPv4 (Inner) 1714 This section provides a EHC classification for the fields of the IPv6 1715 protocol. The IPv6 address only considers the inner IP header when 1716 used in conjunction of the tunnel mode. 1718 +---------------------+--------------------------+--------------+ 1719 | Field | EHC Class | ROHC class | 1720 +---------------------+--------------------------+--------------+ 1721 | Version | STATIC-KNOWN | STATIC-KNOWN | 1722 | Header Length | | | 1723 | . Options enabled | IRREGULAR | RACH | 1724 | . Options disabled | STATIC-KNOWN | STATIC-KNOWN | 1725 | Type of Service | STATIC-KNOWN | RACH | 1726 | Total Length | INFERRED | INFERRED | 1727 | Identification | | | 1728 | . Sequential | PATTERN | PATTERN | 1729 | . Seq. swap | PATTERN | PATTERN | 1730 | . Random | IRREGULAR | IRREGULAR | 1731 | . Zero | STATIC-KNOWN | STATIC-KNOWN | 1732 | Flags | STATIC-KNOWN / IRREGULAR | | 1733 | . Reserved | | STATIC-KNOWN | 1734 | . Don't Fragment | | RACH | 1735 | . More Fragment | | STATIC-KNOWN | 1736 | Fragment offset | STATIC-KNOWN / IRREGULAR | STATIC-KNOWN | 1737 | Time To Live | STATIC-KNOWN / INFERRED | INFERRED | 1738 | Protocol | STATIC-KNOWN / IRREGULAR | STATIC-DEF | 1739 | Header Checksum | INFERRED | INFERRED | 1740 | Source Address | STATIC-KNOWN | STATIC-DEF | 1741 | Destination Address | STATIC-KNOWN | STATIC-DEF | 1742 | Options | IRREGULAR | | 1743 | Padding | IRREGULAR | | 1744 +---------------------+--------------------------+--------------+ 1746 Version, Source and Destination Address and Protocol STATIC-KNOWN 1747 when part of the TS, in which case it has been agreed between the 1748 peers in the EHC context. Otherwise, they are IRREGULAR and thus 1749 cannot be compressed. 1751 Traffic Class, Flow Label, Time To Live and Flags are STATIC-KNOWN if 1752 agreed between the two peers. Otherwise the inner IPv4 header may 1753 also be inferred from the outer IP header if the outer IP header is 1754 an IPv4 header. In any other cases, these fields are IRREGULAR. 1756 Header Length depends on the options, thus when peers agree on 1757 disabling options, the Header Length becomes STATIC-KNOWN and 1758 IRREGULAR otherwise. 1760 Type of Service (DSCP and ECN) are optional and may be disabled in 1761 which case they can be classified as STATIC-KNOWN. 1763 Identification, Flags and Fragment Offset are used to deal with 1764 fragmentation. When fragmentation is disabled, these fields may be 1765 classified as STATIC-KNOWN. When fragmentation is actived, 1766 Identification may be classified as PATTERN or IRREGULAR. Flags or 1767 Fragment offset may be classified as IRREGULAR. 1769 Type of Service, Options and Padding cannot be compressed in a static 1770 way without in-band signalling, thus they are classified as 1771 IRREGULAR. 1773 B.4. UDP 1775 This section provides an EHC classification for the fields of the UDP 1776 header. 1778 +------------------+--------------------------+-------------------+ 1779 | Field | EHC Class | ROHC class | 1780 +------------------+--------------------------+-------------------+ 1781 | Source Port | STATIC-KNOWN / IRREGULAR | STATIC-DEF | 1782 | Destination Port | STATIC-KNOWN / IRREGULAR | STATIC-DEF | 1783 | Length | INFERRED | INFERRED | 1784 | Checksum | STATIC-KNOWN / INFERRED | STATIC, IRREGULAR | 1785 +------------------+--------------------------+-------------------+ 1787 Source and Destination Port are STATIC-KNOWN when part of the TS, in 1788 which case it has been agreed between the peers. Otherwise, they are 1789 IRREGULAR and thus cannot be compressed. 1791 When peers have agreed to disable UDP checksum, the checksum is 1792 always zero and so its value is STATIC-KNOWN. Otherwise the checksum 1793 needs to be computed once the packet has been decompressed. UDP 1794 checksum can be computed as ESP provides an integrity check, thus the 1795 received packet is believed to be unchanged. Note also that 1796 integrity check does not enable error correction which CRC does, but 1797 in case of a bit error encryption will fail, thus this case is 1798 considered as irrelevant. 1800 B.5. UDP-Lite 1802 This section provides an EHC classification for the fields of the 1803 UDP-Lite header. 1805 +---------------------+----------------------------+----------------+ 1806 | Field | EHC Class | ROHC class | 1807 +---------------------+----------------------------+----------------+ 1808 | Source Port | STATIC-KNOWN | STATIC-DEF | 1809 | Destination Port | STATIC-KNOWN | STATIC-DEF | 1810 | Checksum Coverage | STATIC-KNOWN / INFERRED / | IRREGULAR | 1811 | | IRREGULAR | | 1812 | Checksum | INFERRED | IRREGULAR | 1813 +---------------------+----------------------------+----------------+ 1815 See Appendix B.4 for classification of Source and Destination Port. 1817 The Checksum Coverage is the part of the UDP-Lite packet, and 1818 indicates the number of bytes covered by the checksum. The minimal 1819 value is 8, which is the UDP-Lite Header. The maximum value is the 1820 size of the UDP-Lite packet, which means that the checksum is the 1821 same as in UDP. The Coverage can be agreed to be a fixed value or a 1822 value that is function of the total length o fthe UDP packet. In 1823 these cases, Coverage can be classified as STATIC-KNOWN or INFERRED. 1824 Otherwise it is classified as IRREGULAR. 1826 In UDP-Lite the checksum cannot be disabled, but its coverage 1827 changes. Thus it will never appear as zero, but it can be INFERRED 1828 in every case, according to the value of Checksum Coverage. 1830 B.6. TCP 1832 This section provides an EHC classification for the fields of the TCP 1833 header. 1835 +------------------------+--------------+---------------------+ 1836 | Field | EHC Class | ROHC class RFC4413 | 1837 +------------------------+--------------+---------------------+ 1838 | Source Port | STATIC-KNOWN | STATIC-DEF | 1839 | Destination Port | STATIC-KNOWN | STATIC-DEF | 1840 | Sequence Number | PATTERN | CHANGING | 1841 | Acknowledgement Number | PATTERN | CHANGING | 1842 | Data Offset | | INFERRED | 1843 | . Options enabled | IRREGULAR | | 1844 | . Options disabled | STATIC-KNOWN | | 1845 | Reserved Bits | IRREGULAR | CHANGING | 1846 | Flags | IRREGULAR | CHANGING | 1847 | Window | IRREGULAR | CHANGING | 1848 | Checksum | | | 1849 | . Disabled | STATIC-KNOWN | STATIC | 1850 | . Enabled | INFERRED | IRREGULAR | 1851 | Urgent Pointer | IRREGULAR | CHANGING | 1852 | Options | IRREGULAR | CHANGING | 1853 +------------------------+--------------+---------------------+ 1855 See Appendix B.4 for classification of Source and Destination Port. 1857 The TCP Sequence and Acknowledgement Number increase in a PATTERN but 1858 caused by the different TCP-Flags the increase is not performed in 1859 every packet. 1861 Data Offset contains the length of the TCP header including the 1862 options. If options are agreed to be disabled it is STATIC-KNOWN. 1863 If Options are enabled it cannot be decompressed without in-band 1864 signalling, thus it is classified as IRREGULAR in that case. 1866 See Appendix B.4 for the checksum classification. 1868 Flags, Windows, Urgent Pointer and Options cannot be compressed 1869 without in-band signalling, thus classified as IRREGULAR in every 1870 case. 1872 Appendix C. Document Change Log 1874 [draft-mglt-6lo-diet-esp-00.txt]: 1875 Changing affiliation 1877 [draft-mglt-6lo-diet-esp-00.txt]: 1879 Updating references 1881 [draft-mglt-ipsecme-diet-esp-01.txt]: 1882 Diet ESP described in the ROHC framework 1883 ESP is not modified. 1885 [draft-mglt-ipsecme-diet-esp-00.txt]: 1886 NAT consideration added. 1887 Comparison actualized to new Version of 6LoWPAN ESP. 1889 [draft-mglt-dice-diet-esp-00.txt]: First version published. 1891 Authors' Addresses 1893 Daniel Migault (editor) 1894 Ericsson 1895 8400 boulevard Decarie 1896 Montreal, QC H4P 2N2 1897 Canada 1899 Email: daniel.migault@ericsson.com 1901 Tobias Guggemos (editor) 1902 LMU Munich 1903 Oettingenstr. 67 1904 80538 Munchen, Bavaria 1905 Germany 1907 Email: guggemos@mnm-team.org 1908 URI: http://www.mnm-team.org/~guggemos 1910 Carsten Bormann 1911 Universitaet Bremen TZI 1912 Postfach 330440 1913 Bremen D-28359 1914 Germany 1916 Phone: +49-421-218-63921 1917 Email: cabo@tzi.org