idnits 2.17.1 draft-ietf-conex-destopt-03.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 (September 24, 2012) is 4222 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 258, 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: March 28, 2013 IKR University of Stuttgart 6 C. Ucendo 7 Telefonica 8 September 24, 2012 10 IPv6 Destination Option for ConEx 11 draft-ietf-conex-destopt-03 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 March 28, 2013. 37 Copyright Notice 39 Copyright (c) 2012 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 marking IPv6 packets . . . . . . . . . . . . . 4 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 . . . . . . . . . . . . . . . . . . . . . 7 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 2. Conventions used in this document 76 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT", 77 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 78 document are to be interpreted as described in [RFC2119]. 80 3. Background 82 The ConEx working group came up with a list of requirements that had 83 to be met by any marking mechanism. It then considered several 84 alternative mechanisms and evaluated their suitability for ConEx 85 marking. There were no mechanisms found that were completely 86 suitable, but the only mechanism that came close to meeting the 87 requirements was IPv6 destination options. The analysis of the 88 different alternatives can be found in [draft-krishnan-conex-ipv6]. 90 4. Requirements for marking IPv6 packets 92 R-1: The marking mechanism needs to be visible to all ConEx-capable 93 nodes on the path. 95 R-2: The mechanism needs to be able to traverse nodes that do not 96 understand the markings. This is required to ensure that ConEx can 97 be incrementally deployed over the Internet. 99 R-3: The presence of the marking mechanism should not significantly 100 alter the processing of the packet. This is required to ensure that 101 ConEx marked packets do not face any undue delays or drops due to a 102 badly chosen mechanism. 104 R-4: The markings should be immutable once set by the sender. At the 105 very least, any tampering should be detectable. 107 Based on these requirements four solutions to implement the ConEx 108 information in the IPv6 header have been investigated: hop-by-hop 109 options, destination options, using IPv6 header bits (from the flow 110 label), and new extension headers. After evaluating the different 111 solutions, the wg concluded that only the use of a destination option 112 would fulfil the requirements. 114 5. ConEx Destination Option (CDO) 116 The ConEx Destination Option (CDO) is a destination option that can 117 be included in IPv6 datagrams that are sent by ConEx-aware senders in 118 order to inform ConEx-aware nodes on the path about the congestion 119 encountered by packets earlier in the same flow. The CDO has an 120 alignment requirement of (none). 122 0 1 2 3 123 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 1 124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 125 | Option Type | Option Length | 126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 127 |X|L|E|C| Reserved | 128 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 Figure 1: ConEx Destination Option Layout 132 Option Type 134 8-bit identifier of the type of option. The option identifier 135 for the ConEx destination option will be allocated by the IANA. 137 Option Length 139 8-bit unsigned integer. The length of the option (excluding 140 the Option Type and Option Length fields). This field MUST be 141 set to the value 4. 143 X Bit 145 When this bit is set, the transport sender is using ConEx with 146 this packet. If it is not set, the sender is not using ConEx with 147 this packet. 149 L Bit 151 When this bit is set, the transport sender has experienced a loss. 152 If it is not set, the sender has not experienced a loss. 154 E Bit 156 When this bit is set, the transport sender has experienced 157 ECN-signaled congestion. If it is not set, the sender has not 158 experienced ECN-signaled congestion. 160 C Bit 162 When this bit is set, the transport sender is building up 163 congestion credit. Otherwise it is not. 165 Reserved 167 These bits are not used in the current specification. They 168 are set to zero on the sender and are ignored on the receiver. 170 All packets sent over a ConEx-capable connection MUST carry the CDO. 172 If the X bit is the zero all other three bits are undefined. If the 173 X bit is zero that means that the connection is ConEx-capable but 174 this packet SHOULD NOT be accounted to determine ConEx information in 175 an audit function. This can be the case for e.g. pure control 176 packets not carrying any user data. As an example in TCP pure ACKs 177 are usually not ECN-capable and TCP does not have an mechanism to 178 announce the lost of a pure ACK to the sender. Thus congestion 179 information about the ACKs are not available at the sender. 181 If the X bit is set, all three other bit (L, E, C) MAY be set. When 182 ever one of this bits is set, the number of bytes carried by this IP 183 packet (including the IP header) SHOULD be accounted for determining 184 congestion or credit information. In IPv6 the number of bytes can 185 easily be calculated by adding the number 40 (length of the IPv6 186 header in bytes) to the value present in the Payload Length field in 187 the IPv6 header. 189 In principle all of these three bits (L, E, C) MAY be set in the same 190 packet. In this case the packet size MUST be accounted more than 191 once for each respective ConEx information counter. In many cases if 192 congestion occurs the sender will not sent additional credit, but if 193 e.g. a sender assumes losses because of an audit function or needs to 194 maintain a certain sending rate to make an application layer service 195 work, the occurrence of credit bits (c) in parallel to congestion 196 exposure bit (L, E) is reasonable. 198 If a network node extracts the ConEx information from a connection, 199 this node is usually supposed to hold this information byte-wise, 200 e.g. comparing the total number of bytes sent with the number of 201 bytes sent with ConEx congestion mark (L, E) to determine the current 202 whole path congestion level. For ConEx-aware node processing, the 203 CDO MUST use the Payload length field of the preceding IPv6 header 204 for byte-based accounting. When equally sized packets can be 205 assumed, the accounting of the number of packets (instead the number 206 of bytes) should deliver the same result. But a network node must be 207 aware that this estimation can be quite wrong, if e.g. different 208 sized packed are send, and thus is not reliable. 210 A ConEx sender SHOULD set the reserved bits in the CDO to zero. 211 Other nodes SHOULD not interpret these bits. 213 6. Implementation in the fast path of ConEx-aware routers 215 The ConEx information is being encoded into a destination option so 216 that it does not impact forwarding performance in the non-ConEx-aware 217 nodes on the path. Since destination options are not usually 218 processed by routers, the existence of the CDO does not affect the 219 fast path processing of the datagram on non-ConEx-aware routers. i.e. 220 They are not pushed into the slow path towards the control plane for 221 exception processing. 223 The ConEx-aware nodes still need to process the CDO without severely 224 affecting forwarding. For this to be possible, the ConEx-aware 225 routers need to quickly ascertain the presence of the CDO and process 226 the option if it is present. To efficiently perform this, the CDO 227 needs to be placed in a fairly deterministic location. In order to 228 facilitate forwarding on ConEx-aware routers, ConEx-aware senders who 229 send IPv6 datagrams with the CDO MUST place the CDO as the first 230 destination option in the destination options header. 232 7. Compatibility with use of IPsec 234 In IPsec transport mode no action needs to be taken as the CDO is 235 visible to the network. When accounting ConEx information the size 236 of the Authentication Header (AH) SHOULD NOT be accounted as this 237 information has been added later. In the IPsec Tunnel model the CDO 238 SHOULD be copied to the outer IP header as this information is end- 239 to-end. Only the payload of the outer IP header minus the AH SHOULD 240 be accounted. 242 8. Acknowledgements 244 The authors would like to thank Marcelo Bagnulo, Bob Briscoe, Ingemar 245 Johansson, Joel Halpern and John Leslie for the discussions that led 246 to this document. 248 9. Security Considerations 250 This document does not bring up any new security issues. 252 10. IANA Considerations 254 This document defines a new IPv6 destination option for carrying 255 ConEx markings. IANA is requested to assign a new destination option 256 type in the Destination Options registry maintained at 257 http://www.iana.org/assignments/ipv6-parameters ConEx 258 Destination Option [RFCXXXX] The act bits for this option need to be 259 10 and the chg bit needs to be 0. 261 11. Normative References 263 [CAM] Mathis, M. and B. Briscoe, "Congestion Exposure (ConEx) 264 Concepts and Abstract Mechanism", 265 draft-ietf-ConEx-abstract-mech-05 (work in progress), 266 July 2011. 268 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 269 Requirement Levels", BCP 14, RFC 2119, March 1997. 271 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 272 (IPv6) Specification", RFC 2460, December 1998. 274 Authors' Addresses 276 Suresh Krishnan 277 Ericsson 278 8400 Blvd Decarie 279 Town of Mount Royal, Quebec 280 Canada 282 Email: suresh.krishnan@ericsson.com 284 Mirja Kuehlewind 285 IKR University of Stuttgart 287 Email: mirja.kuehlewind@ikr.uni-stuttgart.de 289 Carlos Ralli Ucendo 290 Telefonica 292 Email: ralli@tid.es