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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-18) exists of draft-ietf-mptcp-rfc6824bis-05 ** Obsolete normative reference: RFC 6824 (Obsoleted by RFC 8684) == Outdated reference: A later version (-07) exists of draft-ietf-mptcp-experience-04 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Boucadair 3 Internet-Draft C. Jacquenet 4 Intended status: Experimental Orange 5 Expires: December 2, 2016 May 31, 2016 7 Negotiating the Maximum Number of Multipath TCP (MPTCP) Subflows 8 draft-boucadair-mptcp-max-subflow-02 10 Abstract 12 This document specifies an experimental Multipath TCP (MPTCP) option 13 that is meant to negotiate the maximum number of subflows that can be 14 established and maintained for a given MPTCP connection. The purpose 15 is to minimize any possible performance degradation that can be 16 induced by a possibly large number of establishment requests for 17 additional subflows if the remote endpoint is not appropriately 18 dimensioned to handle such requests. 20 Requirements Language 22 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 23 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 24 document are to be interpreted as described in RFC 2119 [RFC2119]. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on December 2, 2016. 43 Copyright Notice 45 Copyright (c) 2016 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 1.1. Experiment Goals . . . . . . . . . . . . . . . . . . . . 3 62 2. Maximum Subflows MPTCP Option (MP_MAXSUBFLOW) . . . . . . . . 3 63 3. Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 65 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 66 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 67 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 68 6.2. Informative References . . . . . . . . . . . . . . . . . 5 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 71 1. Introduction 73 This document specifies a Multipath TCP (MPTCP) [RFC6824] option that 74 is meant to indicate to a remote peer the maximum number of subflows 75 that can be established within a single MPTCP connection. If the 76 remote peer honors the indication provided in this option, any 77 performance degradation induced by a possibly abusive setup of 78 additional subflows that exceed the said maximum becomes unlikely. 80 This option mainly targets MPTCP deployments within a single 81 administrative domain such as those MPTCP designs meant to achieve 82 load-balancing, for example. The use of this option contributes to 83 the harmonization of node configuration within an administrative 84 domain, so that an optimal number of subflows is maintained by 85 involved nodes independently of their actual performance 86 capabilities. This option can be used in other deployment scenarios. 87 It is out of scope of this document to identify what are such 88 scenarios. 90 Section 3.4 of [I-D.ietf-mptcp-experience] includes a discussion on 91 the MPTCP session manager issues. 93 1.1. Experiment Goals 95 Experiments based upon the MPTCP option described in this document 96 are meant to help operators optimize their MPTCP design and 97 operational procedures, by tweaking some MPTCP parameters such as the 98 number of subflows to be associated with a given MPTCP connection. 99 Experimenting with this MPTCP option should also help assess whether 100 this option can be used to propagate MPTCP-related optimization 101 parameters (derived from the number of concurrent subflows associated 102 to each MPTCP connection) that can be configured in a node that is 103 responsible for aggregating MPTCP connections established with 104 upstream nodes. 106 2. Maximum Subflows MPTCP Option (MP_MAXSUBFLOW) 108 The MP_MAXSUBFLOW option (Figure 1) follows the shared experimental 109 format defined in [I-D.ietf-mptcp-rfc6824bis]. 111 1 2 3 112 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 1 113 +---------------+---------------+-------+-----------------------+ 114 | Kind | Length |Subtype| Flags | Experiment Id | 115 +---------------+---------------+-------+-------+---------------+ 116 | Maximum Subflows | 117 +---------------+-----------------------------------------------+ 119 Figure 1: Option Format 121 The meaning of "Kind", "Length", "Subtype", and "Flags" (especially 122 'S' and 'U' flags) are exactly the same as defined in Section 3.7 of 123 [I-D.ietf-mptcp-rfc6824bis]. 125 Experiment ID MUST be set to 0xAA (see Section 5). 127 The "Maximum Subflows" field indicates the maximum number of 128 concurrent subflows that can be maintained by a given MPTCP endpoint 129 for each MPTCP connection established by or with this endpoint. The 130 value of this field MUST be strictly greater than zero. 132 3. Behavior 134 The MP_MAXSUBFLOW option may be used by a TCP endpoint to indicate to 135 its corresponding peer the maximum number of subflows that it can 136 maintain per MPTCP connection. 138 How an MPTCP endpoint determines the maximum number of concurrent 139 subflows it supports (i.e., the value it indicates in an 140 MP_MAXSUBFLOW option) is implementation-specific. For example, an 141 implementation may support a configuration parameter and/or use a 142 default value. 144 If two peers (T1 and T2) indicate the maximum number of concurrent 145 subflows per connection they can maintain, then they MUST NOT 146 maintain more than "MIN(MAX_SUBFLOW(T1), MAX_SUBFLOW(T2))" concurrent 147 subflows. 149 The absence of the MP_MAXSUBFLOW option in an MPTCP control message 150 issued by a MPTCP endpoint is an indication that this endpoint can 151 instantiate any number of subflows per MPTCP connection. 153 4. Security Considerations 155 MPTCP-related security considerations are documented in [RFC6824] and 156 [RFC7430]. 158 Establishing a large number of subflows may exhaust the resources of 159 an MPTCP implementation (especially, MPTCP servers). MPTCP 160 implementations SHOULD rate-limit the number of concurrent subflows 161 per MPTCP connection. This policy is meant to prevent DoS attacks 162 that would result in creating additional subflows to exhaust the 163 remote peer resources (typically, an MPTCP server). 165 5. IANA Considerations 167 This document uses the experiment Id (0xAA). This Id is not 168 registered yet given that no registry is maintained by IANA for this 169 purpose. 171 6. References 173 6.1. Normative References 175 [I-D.ietf-mptcp-rfc6824bis] 176 Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C. 177 Paasch, "TCP Extensions for Multipath Operation with 178 Multiple Addresses", draft-ietf-mptcp-rfc6824bis-05 (work 179 in progress), January 2016. 181 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 182 Requirement Levels", BCP 14, RFC 2119, 183 DOI 10.17487/RFC2119, March 1997, 184 . 186 [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, 187 "TCP Extensions for Multipath Operation with Multiple 188 Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013, 189 . 191 6.2. Informative References 193 [I-D.ietf-mptcp-experience] 194 Bonaventure, O., Paasch, C., and G. Detal, "Use Cases and 195 Operational Experience with Multipath TCP", draft-ietf- 196 mptcp-experience-04 (work in progress), April 2016. 198 [RFC7430] Bagnulo, M., Paasch, C., Gont, F., Bonaventure, O., and C. 199 Raiciu, "Analysis of Residual Threats and Possible Fixes 200 for Multipath TCP (MPTCP)", RFC 7430, 201 DOI 10.17487/RFC7430, July 2015, 202 . 204 Authors' Addresses 206 Mohamed Boucadair 207 Orange 208 Rennes 35000 209 France 211 Email: mohamed.boucadair@orange.com 213 Christian Jacquenet 214 Orange 215 Rennes 35000 216 France 218 Email: christian.jacquenet@orange.com