idnits 2.17.1 draft-ietf-6man-resilient-rs-04.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 : ---------------------------------------------------------------------------- == The 'Updates: ' line in the draft header should list only the _numbers_ of the RFCs which will be updated by this document (if approved); it should not include the word 'RFC' in the list. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 14, 2014) is 3481 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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) == Outdated reference: A later version (-03) exists of draft-droms-dhc-dhcpv6-solmaxrt-update-02 -- Possible downref: Normative reference to a draft: ref. 'SOLMAXRT' Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6man Working Group S. Krishnan 3 Internet-Draft Ericsson 4 Updates: RFC4861 (if approved) D. Anipko 5 Intended status: Standards Track Unaffiliated 6 Expires: April 17, 2015 D. Thaler 7 Microsoft 8 October 14, 2014 10 Packet loss resiliency for Router Solicitations 11 draft-ietf-6man-resilient-rs-04 13 Abstract 15 When an interface on a host is initialized, the host transmits Router 16 Solicitations in order to minimize the amount of time it needs to 17 wait until the next unsolicited multicast Router Advertisement is 18 received. In certain scenarios, these router solicitations 19 transmitted by the host might be lost. This document specifies a 20 mechanism for hosts to cope with the loss of the initial Router 21 Solicitations. Furthermore, on some links, unsolicited multicast 22 Router Advertisements are never sent and the mechanism in this 23 document is intended to work even in such scenarios. 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 April 17, 2015. 42 Copyright Notice 44 Copyright (c) 2014 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 1.1. Conventions used in this document . . . . . . . . . . . . 3 61 2. Proposed algorithm . . . . . . . . . . . . . . . . . . . . . 4 62 2.1. Stopping the retransmissions . . . . . . . . . . . . . . 4 63 3. Configuring the use of retransmissions . . . . . . . . . . . 5 64 4. Known Limitations . . . . . . . . . . . . . . . . . . . . . . 5 65 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 66 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 67 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 68 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 69 8.1. Normative References . . . . . . . . . . . . . . . . . . 5 70 8.2. Informative References . . . . . . . . . . . . . . . . . 6 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 73 1. Introduction 75 As specified in [RFC4861], when an interface on a host is 76 initialized, in order to obtain Router Advertisements quickly, a host 77 transmits up to MAX_RTR_SOLICITATIONS (3) Router Solicitation 78 messages, each separated by at least RTR_SOLICITATION_INTERVAL (4) 79 seconds. In certain scenarios, these router solicitations 80 transmitted by the host might be lost. e.g. The host is connected to 81 a bridged residential gateway over Ethernet or WiFi. LAN 82 connectivity is achieved at interface initialization, but the 83 upstream WAN connectivity is not active yet. In this case, the host 84 just gives up after the initial RS retransmits. 86 Once the initial RSs are lost, the host gives up and assumes that 87 there are no routers on the link as specified in Section 6.3.7 of 88 [RFC4861]. The host will not have any form of Internet connectivity 89 until the next unsolicited multicast Router Advertisement is 90 received. These Router Advertisements are transmitted at most 91 MaxRtrAdvInterval seconds apart (maximum value 1800 seconds). Thus 92 in the worst case scenario a host would be without any connectivity 93 for 30 minutes. In general, the delay may be unacceptable in some 94 scenarios. 96 1.1. Conventions used in this document 98 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 99 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 100 document are to be interpreted as described in [RFC2119]. 102 2. Proposed algorithm 104 To achieve resiliency to packet loss, the host needs to continue 105 retransmitting the Router Solicitations until it receives a Router 106 Advertisement, or until it is willing to accept that no router 107 exists. If the host continues retransmitting the RSs at 108 RTR_SOLICITATION_INTERVAL second intervals, it may cause excessive 109 network traffic if a large number of such hosts exists. To achieve 110 resiliency while keeping the aggregate network traffic low, the host 111 can use some form of exponential backoff algorithm to retransmit the 112 RSs. 114 Hosts complying to this specification MUST use the exponential 115 backoff algorithm for retransmits that is described in Section 14 of 116 [RFC3315] in order to continuously retransmit the Router 117 Solicitations until a Router Advertisement is received. The hosts 118 SHOULD use the following variables as input to the retransmission 119 algorithm: 121 IRT 4 seconds 123 MRT 3600 seconds 125 MRC 0 127 MRD 0 129 The initial value IRT was chosen to be in line with the current 130 retransmission interval (RTR_SOLICITATION_INTERVAL) that is specified 131 by [RFC4861] and the maximum retransmission time MRT was chosen to be 132 in line with the new value of SOL_MAX_RT as specified by [SOLMAXRT]. 133 This is to ensure that the short term behavior of the RSs is similar 134 to what is experienced in current networks, and longer term 135 persistent retransmission behavior trends towards being similar to 136 that of DHCPv6 [RFC3315] [SOLMAXRT]. 138 2.1. Stopping the retransmissions 140 On multicast-capable links, the hosts following this specification 141 SHOULD stop retransmitting the RSs when Router Discovery is 142 successful (i.e. an RA with a non-zero Router Lifetime that results 143 in a default route is received). If an RA is recieved from a router 144 and it does not result in a default route (i.e. Router Lifetime is 145 zero) the host MUST continue retransmitting the RSs. 147 On non-multicast links, the hosts following this specification MUST 148 continue retransmitting the RSs even after an RA that results in a 149 default route is received. This is required because, in such links, 150 sending an RA can only be triggered by an RS. Please note that such 151 links have special mechanisms for sending RSes as well. e.g. The 152 mechanism specified in Section 8.3.4. of ISATAP [RFC5214] unicasts 153 the RSes to specific routers. 155 3. Configuring the use of retransmissions 157 Implementations of this specification MAY provide a configuration 158 option to enable or disable the use of such potentially infinite 159 retransmissions. If the implementation provides such a configuration 160 option, it MUST be able to enable/disable retransmissions on a per- 161 interface basis. 163 4. Known Limitations 165 When an IPv6-capable host attaches to a network that does not have 166 IPv6 enabled, it transmits 3 (MAX_RTR_SOLICITATIONS) Router 167 Solicitations as specified in [RFC4861]. If it receives no Router 168 Advertisements, it assumes that there are no routers present on the 169 link and it ceases to send further RSs. With the mechanism specified 170 in this document, the host will continue to retransmit RSs 171 indefinitely at the rate of approximately 1 RS per hour. It is 172 unclear how to differentiate between such a network with no IPv6 173 routers and a link where an IPv6 router is temporarily unreachable 174 but could become reachable in the future. 176 5. IANA Considerations 178 This document does not require any IANA actions. 180 6. Security Considerations 182 This document does not present any additional security issues beyond 183 those discussed in [RFC4861]. 185 7. Acknowledgements 187 The authors would like to thank Steve Baillargeon, Erik Kline, Andrew 188 Yourtchenko, Ole Troan, Erik Nordmark, Lorenzo Colitti, Thomas Narten 189 and Ran Atkinson for their reviews and suggestions that made this 190 document better. 192 8. References 194 8.1. Normative References 196 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 197 Requirement Levels", BCP 14, RFC 2119, March 1997. 199 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 200 and M. Carney, "Dynamic Host Configuration Protocol for 201 IPv6 (DHCPv6)", RFC 3315, July 2003. 203 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 204 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 205 September 2007. 207 [SOLMAXRT] 208 Droms, R., "Modification to Default Value of SOL_MAX_RT", 209 draft-droms-dhc-dhcpv6-solmaxrt-update-02 (work in 210 progress), January 2012. 212 8.2. Informative References 214 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 215 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 216 March 2008. 218 Authors' Addresses 220 Suresh Krishnan 221 Ericsson 222 8400 Decarie Blvd. 223 Town of Mount Royal, QC 224 Canada 226 Phone: +1 514 345 7900 x42871 227 Email: suresh.krishnan@ericsson.com 229 Dmitry Anipko 230 Unaffiliated 232 Phone: +1 425 442 6356 233 Email: dmitry.anipko@gmail.com 235 Dave Thaler 236 Microsoft 237 One Microsoft Way 238 Redmond, WA 239 USA 241 Email: dthaler@microsoft.com