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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) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPv6 Maintenance S. Krishnan 3 Internet-Draft Ericsson 4 Updates: 4861 (if approved) J. Korhonen 5 Intended status: Standards Track Broadcom 6 Expires: January 9, 2017 S. Chakrabarti 7 Ericsson 8 E. Nordmark 9 Arista Networks 10 A. Yourtchenko 11 cisco 12 July 8, 2016 14 Support for adjustable maximum router lifetimes per-link 15 draft-ietf-6man-maxra-01 17 Abstract 19 The neighbor discovery protocol specifies the maximum time allowed 20 between sending unsolicited multicast Router Advertisements from a 21 router interface as well as the maximum router lifetime. It also 22 allows the limits to be overridden by link-layer specific documents. 23 This document allows for overriding these values on a per-link basis. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on January 9, 2017. 42 Copyright Notice 44 Copyright (c) 2016 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 3. Relationship between AdvDefaultLifetime and MaxRtrAdvInterval 3 62 4. Updates to RFC4861 . . . . . . . . . . . . . . . . . . . . . 4 63 5. Host Behavior . . . . . . . . . . . . . . . . . . . . . . . . 4 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 65 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 66 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 67 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 9.1. Normative References . . . . . . . . . . . . . . . . . . 4 69 9.2. Informative References . . . . . . . . . . . . . . . . . 5 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 72 1. Introduction 74 IPv6 Neighbor Discovery relies on IP multicast with the expectation 75 to be efficient with respect to available bandwidth and to avoid 76 generating interrupts in the network nodes. On some datalink-layer 77 network, for example IEEE 802.11 WiFi, this is not the case because 78 of limitations in the services offered by the datalink-layer network 79 [draft-vyncke-6man-mcast-not-efficient-01]. On such links any 80 possible reduction of multicast traffic will be highly beneficial. 81 Unfortunately, due to the fixed protocol constants specified in 82 [RFC4861] it is difficult to relax the multicast timers for neighbor 83 discovery. There are already link technology specific clarifications 84 how to tune protocol constants for certain system with the 85 expectation to reduce excess Neighbor Discovery Protocol (NDP) 86 traffic. 3GPP cellular links are one existing example 87 [RFC6459][RFC7066]. 89 This document specifies updates to the IPv6 Neighbor Discovery 90 Protocol [RFC4861] for relaxing the the maximum time allowed between 91 sending unsolicited multicast Router Advertisements (RA) from a 92 router interface as well as for the maximum router lifetime. 94 2. Terminology 96 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 97 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 98 document are to be interpreted as described in [RFC2119]. 100 3. Relationship between AdvDefaultLifetime and MaxRtrAdvInterval 102 MaxRtrAdvInterval is an upper bound on the time between the two 103 successive Router Advertisement messages are sent, therefore one 104 might reason about the relationship between these two values in terms 105 of the ratio K=AdvDefaultLifetime/MaxRtrAdvInterval, which expresses 106 how many Router Advertisements will be guaranteed to be sent before 107 the router lifetime expiry. 109 Assuming unicast Solicited Router Advertisements or a perfectly 110 stable network, on a theoretically perfect link with no losses, it 111 would have been sufficient to have K just above 1 - so that the sent 112 Router Advertisement refreshes the router entry just before it 113 expires. On the real links which allow for some loss, one would need 114 to use K>2 in order to minimize the chances of a single router 115 advertisement loss causing a loss of the router entry. 117 The exact calculation will depend on the packet loss probability. An 118 example: if we take a ballpark value of 1% probability of a packet 119 loss, then K=2 will give 0.01% percent chance of an outage due to a 120 packet loss, K=3 will give 0.0001% chance of an outage, and so forth. 121 To reverse the numbers, with these parameters, K~=1 gives 99% 122 reliability, K~=2 gives 99.99% reliability, and K~=3 gives 99.9999% 123 reliability - the latter should be good enough for a lot of 124 scenarios. 126 In a network with higher packet loss or if the higher reliability is 127 desired, the K might be chosen to be even higher. On the other hand, 128 some of the data link layers provide reliable delivery at layer 2 - 129 so there one might even consider using the "theoretical" value of K 130 just above 1. Since the choice of these two parameters does not 131 impact the interoperability per se, this document does not impose any 132 specific constraints on their values other than providing the 133 guidelines in this section, therefore each individual link can 134 optimize accordingly to its use case. 136 Also AdvDefaultLifetime MUST be set to a value greater than or equal 137 to the selected MaxRtrAdvInterval. Otherwise, a router lifetime is 138 guaranteed to expire before the new Router Advertisement has a chance 139 to be sent, thereby creating an outage. 141 4. Updates to RFC4861 143 This document updates Section 6.2.1. of [RFC4861] to update the 144 following router configuration variables. MaxRtrAdvInterval MUST be 145 no greater than 65535. AdvDefaultLifetime MUST be between 146 MaxRtrAdvInterval and 65535. 148 5. Host Behavior 150 Legacy hosts on a link with updated routers may have issues with a 151 Router Lifetime of more than 9000 seconds. In the few 152 implementations we have tested with general purpose operating 153 systems, there does not seem to be any issues with setting this field 154 to more than 9000, but there might be implementations that 155 incorrectly (since RFC4861 requires receivers to handle any value) 156 reject such RAs. 158 6. Security Considerations 160 On a link where router advertisements are few and far between, the 161 attack window for a rogue router to send an unsolicited RA is greatly 162 increased. These attacks can easily be prevented by using SeND 163 [RFC3971] 165 7. IANA Considerations 167 This document does not require any IANA action. 169 8. Acknowledgements 171 The authors would like to thank the members of the 6man efficient ND 172 design team for their comments that led to the creation of this 173 draft. The authors would also like to thank Lorenzo Colitti, Erik 174 Kline, Jeena Rachel John and Brian Carpenter for their comments and 175 suggestions that improved this document. 177 9. References 179 9.1. Normative References 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 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 187 "SEcure Neighbor Discovery (SEND)", RFC 3971, 188 DOI 10.17487/RFC3971, March 2005, 189 . 191 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 192 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 193 DOI 10.17487/RFC4861, September 2007, 194 . 196 9.2. Informative References 198 [RFC6459] Korhonen, J., Ed., Soininen, J., Patil, B., Savolainen, 199 T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation 200 Partnership Project (3GPP) Evolved Packet System (EPS)", 201 RFC 6459, DOI 10.17487/RFC6459, January 2012, 202 . 204 [RFC7066] Korhonen, J., Ed., Arkko, J., Ed., Savolainen, T., and S. 205 Krishnan, "IPv6 for Third Generation Partnership Project 206 (3GPP) Cellular Hosts", RFC 7066, DOI 10.17487/RFC7066, 207 November 2013, . 209 Authors' Addresses 211 Suresh Krishnan 212 Ericsson 213 8400 Decarie Blvd. 214 Town of Mount Royal, QC 215 Canada 217 Phone: +1 514 345 7900 x42871 218 Email: suresh.krishnan@ericsson.com 220 Jouni Korhonen 221 Broadcom 222 Porkkalankatu 24 223 FIN-00180 Helsinki 224 Finland 226 Email: jouni.nospam@gmail.com 227 Samita Chakrabarti 228 Ericsson 229 USA 231 Email: samita.chakrabarti@ericsson.com 233 Erik Nordmark 234 Arista Networks 235 Santa Clara, CA 236 USA 238 Email: nordmark@acm.org 240 Andrew Yourtchenko 241 cisco 242 6b de Kleetlaan 243 Diegem 1831 244 Belgium 246 Email: ayourtch@cisco.com