idnits 2.17.1 draft-ietf-6man-resilient-rs-01.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 date (May 6, 2013) is 4008 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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) == Outdated reference: A later version (-03) exists of draft-droms-dhc-dhcpv6-solmaxrt-update-02 -- Possible downref: Normative reference to a draft: ref.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 (~~), 2 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 Intended status: Standards Track D. Anipko 5 Expires: November 7, 2013 D. Thaler 6 Microsoft 7 May 6, 2013 9 Packet loss resiliency for Router Solicitations 10 draft-ietf-6man-resilient-rs-01 12 Abstract 14 When an interface on a host is initialized, the host transmits Router 15 Solicitations in order to minimize the amount of time it needs to 16 wait until the next unsolicited multicast Router Advertisement is 17 received. In certain scenarios, these router solicitations 18 transmitted by the host might be lost. This document specifies a 19 mechanism for hosts to cope with the loss of the initial Router 20 Solicitations. Furthermore, on some links, unsolicited multicast 21 Router Advertisements are never sent and the mechanism in this 22 document is intended to work even in such scenarios. 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on November 7, 2013. 41 Copyright Notice 43 Copyright (c) 2013 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 1.1. Conventions used in this document . . . . . . . . . . . . . 3 60 2. Proposed algorithm . . . . . . . . . . . . . . . . . . . . . . 4 61 2.1. Stopping the retransmissions . . . . . . . . . . . . . . . 4 62 3. Configuring the use of retransmissions . . . . . . . . . . . . 5 63 4. Known Limitations . . . . . . . . . . . . . . . . . . . . . . . 5 64 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 65 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 66 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 67 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 68 8.1. Normative References . . . . . . . . . . . . . . . . . . . 5 69 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 72 1. Introduction 74 As specified in [RFC4861], when an interface on a host is 75 initialized, in order to obtain Router Advertisements quickly, a host 76 transmits up to MAX_RTR_SOLICITATIONS (3) Router Solicitation 77 messages, each separated by at least RTR_SOLICITATION_INTERVAL (4) 78 seconds. In certain scenarios, these router solicitations 79 transmitted by the host might be lost. 81 The generic scenario is that the interface on the host comes up 82 before it gets access to a router. Examples include: 84 a. The host is connected to a bridged residential gateway over 85 Ethernet or WiFi. LAN connectivity is achieved at interface 86 initialization, but the upstream WAN connectivity is not active 87 yet. In this case, the host just gives up after the initial RS 88 retransmits. 89 b. Access networks/links that turn off periodic RAs and only send 90 RAs in response to RSs. In this case, if the link between the AP 91 and the host comes up before the link between the AP and the 92 Controller/Router, the host will never be able to connect. 93 c. Links that are not multicast capable. In this case, sending an 94 RA can only be triggered by an RS (as is the case, for instance, 95 on ISATAP [RFC5214] links). 97 Once the initial RSs are lost, the host gives up and assumes that 98 there are no routers on the link as specified in Section 6.3.7 of 99 [RFC4861]. The host will not have any form of Internet connectivity 100 until the next unsolicited multicast Router Advertisement is 101 received. These Router Advertisements are transmitted at most 102 MaxRtrAdvInterval seconds apart (maximum value 1800 seconds). Thus 103 in the worst case scenario a host would be without any connectivity 104 for 30 minutes. In general, the delay may be unacceptable in some 105 scenarios. 107 1.1. Conventions used in this document 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 111 document are to be interpreted as described in [RFC2119]. 113 2. Proposed algorithm 115 To achieve resiliency to packet loss, the host needs to continue 116 retransmitting the Router Solicitations until it receives a Router 117 Advertisement, or until it is willing to accept that no router 118 exists. If the host continues retransmitting the RSs at 119 RTR_SOLICITATION_INTERVAL second intervals, it may cause excessive 120 network traffic if a large number of such hosts exists. To achieve 121 resiliency while keeping the aggregate network traffic low, the host 122 can use some form of exponential backoff algorithm to retransmit the 123 RSs. 125 Hosts complying to this specification MUST use the exponential 126 backoff algorithm for retransmits that is described in Section 14 of 127 [RFC3315] in order to continuously retransmit the Router 128 Solicitations until a Router Advertisement is received. The hosts 129 SHOULD use the following variables as input to the retransmission 130 algorithm: 132 IRT 4 seconds 133 MRT 3600 seconds 134 MRC 0 135 MRD 0 137 The initial value IRT was chosen to be in line with the current 138 retransmission interval (RTR_SOLICITATION_INTERVAL) that is specified 139 by [RFC4861] and the maximum retransmission time MRT was chosen to be 140 in line with the new value of SOL_MAX_RT as specified by [SOLMAXRT]. 141 This is to ensure that the short term behavior of the RSs is similar 142 to what is experienced in current networks, and longer term 143 persistent retransmission behavior trends towards being similar to 144 that of DHCPv6 [RFC3315] [SOLMAXRT]. 146 2.1. Stopping the retransmissions 148 On multicast-capable links, the hosts following this specification 149 MUST stop retransmitting the RSs when an RA that results in a default 150 route is received. If an RA is recieved from a router and it does 151 not result in a default route the host MUST continue retransmitting 152 the RSs. 154 On non-multicast links, the hosts following this specification MUST 155 continue retransmitting the RSs even after an RA that results in a 156 default route is received. This is required because, in such links, 157 sending an RA can only be triggered by an RS. 159 3. Configuring the use of retransmissions 161 Implementations of this specification MAY provide a configuration 162 option to enable or disable the use of such potentially infinite 163 retransmissions. If the implementation provides such a configuration 164 option, it MUST be able to enable/disable retransmissions on a per- 165 interface basis. 167 4. Known Limitations 169 When an IPv6-capable host attaches to a network that does not have 170 IPv6 enabled, it transmits 3 (MAX_RTR_SOLICITATIONS) Router 171 Solicitations as specified in [RFC4861]. If it receives no Router 172 Advertisements, it assumes that there are no routers present on the 173 link and it ceases to send further RSs. With the mechanism specified 174 in this document, the host will continue to retransmit RSs 175 indefinitely at the rate of approximately 1 RS per hour. It is 176 unclear how to differentiate between such a network with no IPv6 177 routers and a link where an IPv6 router is temporarily unreachable 178 but could become reachable in the future. 180 5. IANA Considerations 182 This document does not require any IANA actions. 184 6. Security Considerations 186 This document does not present any additional security issues beyond 187 those discussed in [RFC4861]. 189 7. Acknowledgements 191 The author would like to thank Steve Baillargeon, and Erik Kline for 192 their reviews and suggestions that made this document better. 194 8. References 196 8.1. Normative References 198 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 199 Requirement Levels", BCP 14, RFC 2119, March 1997. 201 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 202 and M. Carney, "Dynamic Host Configuration Protocol for 203 IPv6 (DHCPv6)", RFC 3315, July 2003. 205 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 206 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 207 September 2007. 209 [SOLMAXRT] 210 Droms, R., "Modification to Default Value of SOL_MAX_RT", 211 draft-droms-dhc-dhcpv6-solmaxrt-update-02 (work in 212 progress), January 2012. 214 8.2. Informative References 216 [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site 217 Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, 218 March 2008. 220 Authors' Addresses 222 Suresh Krishnan 223 Ericsson 224 8400 Decarie Blvd. 225 Town of Mount Royal, QC 226 Canada 228 Phone: +1 514 345 7900 x42871 229 Email: suresh.krishnan@ericsson.com 231 Dmitry Anipko 232 Microsoft 233 One Microsoft Way 234 Redmond, WA 235 USA 237 Phone: +1 425 703 7070 238 Email: danipko@microsoft.com 239 Dave Thaler 240 Microsoft 241 One Microsoft Way 242 Redmond, WA 243 USA 245 Email: dthaler@microsoft.com