idnits 2.17.1 draft-ietf-conex-destopt-05.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document seems to lack the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords -- however, there's a paragraph with a matching beginning. Boilerplate error? (The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: A ConEx sender SHOULD set the reserved bits in the CDO to zero. Other nodes SHOULD not interpret these bits. -- The document date (October 21, 2013) is 3833 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'RFCXXXX' is mentioned on line 271, but not defined -- No information found for draft-ietf-ConEx-abstract-mech - is the name correct? -- Possible downref: Normative reference to a draft: ref. 'CAM' ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ConEx Working Group S. Krishnan 3 Internet-Draft Ericsson 4 Intended status: Standards Track M. Kuehlewind 5 Expires: April 24, 2014 IKR University of Stuttgart 6 C. Ucendo 7 Telefonica 8 October 21, 2013 10 IPv6 Destination Option for ConEx 11 draft-ietf-conex-destopt-05 13 Abstract 15 ConEx is a mechanism by which senders inform the network about the 16 congestion encountered by packets earlier in the same flow. This 17 document specifies an IPv6 destination option that is capable of 18 carrying ConEx markings in IPv6 datagrams. 20 Status of this Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on April 24, 2014. 37 Copyright Notice 39 Copyright (c) 2013 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 2. Conventions used in this document . . . . . . . . . . . . . . . 3 56 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 4. Requirements for the coding of ConEx in IPv6 . . . . . . . . . 3 58 5. ConEx Destination Option (CDO) . . . . . . . . . . . . . . . . 4 59 6. Implementation in the fast path of ConEx-aware routers . . . . 6 60 7. Compatibility with use of IPsec . . . . . . . . . . . . . . . . 7 61 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 62 9. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 63 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 64 11. Normative References . . . . . . . . . . . . . . . . . . . . . 8 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 67 1. Introduction 69 ConEx [CAM] is a mechanism by which senders inform the network about 70 the congestion encountered by packets earlier in the same flow. This 71 document specifies an IPv6 destination option [RFC2460] that can be 72 used for performing ConEx markings in IPv6 datagrams. 74 The ConEx information can be used by any network element on the path 75 to e.g. do traffic management or egress policing. Additionally this 76 information will potentially be used by an audit function that checks 77 the integrity of the sender's signaling. 79 2. Conventions used in this document 81 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT", 82 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 83 document are to be interpreted as described in [RFC2119]. 85 3. Background 87 The ConEx working group came up with a list of requirements that had 88 to be met by any ConEx coding. It then considered several 89 alternative mechanisms in Ipv6 and evaluated their suitability for 90 ConEx marking. There were no mechanisms found that were completely 91 suitable, but the only mechanism that came close to meeting the 92 requirements was IPv6 destination options. The analysis of the 93 different alternatives can be found in [draft-krishnan-conex-ipv6]. 95 4. Requirements for the coding of ConEx in IPv6 97 R-1: The marking mechanism needs to be visible to all ConEx-capable 98 nodes on the path. 100 R-2: The mechanism needs to be able to traverse nodes that do not 101 understand the markings. This is required to ensure that ConEx can 102 be incrementally deployed over the Internet. 104 R-3: The presence of the marking mechanism should not significantly 105 alter the processing of the packet. This is required to ensure that 106 ConEx marked packets do not face any undue delays or drops due to a 107 badly chosen mechanism. 109 R-4: The markings should be immutable once set by the sender. At the 110 very least, any tampering should be detectable. 112 Based on these requirements four solutions to implement the ConEx 113 information in the IPv6 header have been investigated: hop-by-hop 114 options, destination options, using IPv6 header bits (from the flow 115 label), and new extension headers. After evaluating the different 116 solutions, the wg concluded that only the use of a destination option 117 would fulfil the requirements. 119 5. ConEx Destination Option (CDO) 121 The ConEx Destination Option (CDO) is a destination option that can 122 be included in IPv6 datagrams that are sent by ConEx-aware senders in 123 order to inform ConEx-aware nodes on the path about the congestion 124 encountered by packets earlier in the same flow. The CDO has an 125 alignment requirement of (none). 127 0 1 2 3 128 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 1 129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 | Option Type | Option Length | 131 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 |X|L|E|C| Reserved | 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 Figure 1: ConEx Destination Option Layout 137 Option Type 139 8-bit identifier of the type of option. The option identifier 140 for the ConEx destination option will be allocated by the IANA. 142 Option Length 144 8-bit unsigned integer. The length of the option (excluding 145 the Option Type and Option Length fields). This field MUST be 146 set to the value 4. 148 X Bit 150 When this bit is set, the transport sender is using ConEx with 151 this packet. If it is not set, the sender is not using ConEx with 152 this packet. 154 L Bit 156 When this bit is set, the transport sender has experienced a loss. 158 E Bit 160 When this bit is set, the transport sender has experienced 161 ECN-signaled congestion. 163 C Bit 165 When this bit is set, the transport sender is building up 166 congestion credit in the audit. 168 Reserved 170 These bits are not used in the current specification. They 171 are set to zero on the sender and are ignored on the receiver. 173 All packets sent over a ConEx-capable connection MUST carry the CDO. 174 The CDO is immutable. Network devices SHOULD only read the flags. 175 IPSeC Authentication Header (AH) may be used to verify that the CDO 176 has not been modified. 178 If the X bit is zero all other three bits are undefined and thus 179 should be ignored. The X bit set to zero means that the connection 180 is ConEx-capable but this packet SHOULD NOT be accounted to determine 181 ConEx information in an audit function. This can be the case for 182 e.g. pure control packets not carrying any user data. As an example 183 in TCP pure ACKs are usually not ECN-capable and TCP does not have an 184 mechanism to announce the lost of a pure ACK to the sender. Thus 185 congestion information about ACKs are not available at the sender. 187 If the X bit is set, all three other bit (L, E, C) MAY be set. 188 Whenever one of these bits is set, the number of bytes carried by 189 this IP packet (including the IP header) SHOULD be accounted for 190 determining congestion or credit information. In IPv6 the number of 191 bytes can easily be calculated by adding the number 40 (length of the 192 IPv6 header in bytes) to the value present in the Payload Length 193 field in the IPv6 header. 195 Credits are sent previous to the occurence of congestion (loss or 196 ECN-CE marks) and the amount of credits should cover the congestion 197 risk. Note, the maximum congestion risk is that all packets in 198 flight get lost or ECN marked. 200 If the L or E bit is set, a congestion signal in form of loss or, 201 respectively, an ECN mark was previously expirienced by the same 202 connection. 204 In principle all of these three bits (L, E, C) MAY be set in the same 205 packet. In this case the packet size MUST be accounted more than 206 once for each respective ConEx information counter. 208 If a network node extracts the ConEx information from a connection, 209 this node is usually supposed to hold this information byte-wise, 210 e.g. comparing the total number of bytes sent with the number of 211 bytes sent with ConEx congestion mark (L, E) to determine the current 212 whole path congestion level. For ConEx-aware node processing, the 213 CDO MUST use the Payload length field of the preceding IPv6 header 214 for byte-based accounting. When equally sized packets can be 215 assumed, the accounting of the number of packets (instead the number 216 of bytes) should deliver the same result. But a network node must be 217 aware that this estimation can be quite wrong, if e.g. different 218 sized packed are send, and thus is not reliable. 220 A ConEx sender SHOULD set the reserved bits in the CDO to zero. 221 Other nodes SHOULD not interpret these bits. 223 ToDo: Preferential drop of not ConEx-marked packets... 225 6. Implementation in the fast path of ConEx-aware routers 227 The ConEx information is being encoded into a destination option so 228 that it does not impact forwarding performance in the non-ConEx-aware 229 nodes on the path. Since destination options are not usually 230 processed by routers, the existence of the CDO does not affect the 231 fast path processing of the datagram on non-ConEx-aware routers. i.e. 233 They are not pushed into the slow path towards the control plane for 234 exception processing. 236 The ConEx-aware nodes still need to process the CDO without severely 237 affecting forwarding. For this to be possible, the ConEx-aware 238 routers need to quickly ascertain the presence of the CDO and process 239 the option if it is present. To efficiently perform this, the CDO 240 needs to be placed in a fairly deterministic location. In order to 241 facilitate forwarding on ConEx-aware routers, ConEx-aware senders who 242 send IPv6 datagrams with the CDO MUST place the CDO as the first 243 destination option in the destination options header. 245 7. Compatibility with use of IPsec 247 In IPsec transport mode no action needs to be taken as the CDO is 248 visible to the network. When accounting ConEx information the size 249 of the Authentication Header (AH) SHOULD NOT be accounted as this 250 information has been added later. In the IPsec Tunnel model the CDO 251 SHOULD be copied to the outer IP header as this information is end- 252 to-end. Only the payload of the outer IP header minus the AH SHOULD 253 be accounted. 255 8. Acknowledgements 257 The authors would like to thank Marcelo Bagnulo, Bob Briscoe, Ingemar 258 Johansson, Joel Halpern and John Leslie for the discussions that led 259 to this document. 261 9. Security Considerations 263 This document does not bring up any new security issues. 265 10. IANA Considerations 267 This document defines a new IPv6 destination option for carrying 268 ConEx markings. IANA is requested to assign a new destination option 269 type in the Destination Options registry maintained at 270 http://www.iana.org/assignments/ipv6-parameters ConEx 271 Destination Option [RFCXXXX] The act bits for this option need to be 272 10 and the chg bit needs to be 0. 274 11. Normative References 276 [CAM] Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx) 277 Concepts and Abstract Mechanism", 278 draft-ietf-ConEx-abstract-mech-05 (work in progress), 279 July 2011. 281 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 282 Requirement Levels", BCP 14, RFC 2119, March 1997. 284 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 285 (IPv6) Specification", RFC 2460, December 1998. 287 Authors' Addresses 289 Suresh Krishnan 290 Ericsson 291 8400 Blvd Decarie 292 Town of Mount Royal, Quebec 293 Canada 295 Email: suresh.krishnan@ericsson.com 297 Mirja Kuehlewind 298 IKR University of Stuttgart 300 Email: mirja.kuehlewind@ikr.uni-stuttgart.de 302 Carlos Ralli Ucendo 303 Telefonica 305 Email: ralli@tid.es