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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'RFC8200' is defined on line 259, but no explicit reference was found in the text ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3633 (Obsoleted by RFC 8415) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group F. Templin, Ed. 3 Internet-Draft Boeing Research & Technology 4 Intended status: Informational November 20, 2017 5 Expires: May 24, 2018 7 The DHCPv6 Option for IPv6 Neighbor Discovery 8 draft-templin-6man-dhcpv6-ndopt-00.txt 10 Abstract 12 IPv6 Neighbor Discovery (IPv6ND) specifies a control message set for 13 nodes to discover neighbors, routers, prefixes and other services on 14 the link. It also supports a manner of StateLess Address 15 AutoConfiguration (SLAAC). The Dynamic Host Configuration Protocol 16 for IPv6 (DHCPv6) specifies a service for the stateful delegation of 17 addresses and prefixes. 19 Currently, at least two round-trip message exchanges are necessary in 20 order to perform the IPv6ND router discovery and DHCPv6 address/ 21 prefix delegation functions. This document presents a protocol for 22 combining these two round trips into a single round trip by joining 23 the two services into a single unified service. 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 https://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 May 24, 2018. 42 Copyright Notice 44 Copyright (c) 2017 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 (https://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. The DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 3 61 3. DHCPv6 Option Usage . . . . . . . . . . . . . . . . . . . . . 3 62 4. Implementation Considerations . . . . . . . . . . . . . . . . 4 63 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 65 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 66 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 67 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 68 8.2. Informative References . . . . . . . . . . . . . . . . . 6 69 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 71 1. Introduction 73 IPv6 Neighbor Discovery (IPv6ND) [RFC4861] specifies a control 74 message set for nodes to discover neighbors, routers, prefixes and 75 other services on the link. It also supports a manner of StateLess 76 Address AutoConfiguration (SLAAC). The Dynamic Host Configuration 77 Protocol for IPv6 (DHCPv6) specifies a service for the stateful 78 delegation of addresses and prefixes [RFC3315][RFC3633]. 80 Currently, at least two round-trip message exchanges are necessary in 81 order to perform the IPv6ND router discovery and DHCPv6 address/ 82 prefix delegation functions. This document presents a protocol for 83 combining these two round trips into a single round trip by joining 84 the two services into a single unified service. 86 When a node first comes onto the link, it sends a Router Solicitation 87 (RS) message to elicit a Router Advertisement (RA) message from one 88 or more routers for the link. If the node also needs to acquire 89 managed addresses and prefixes (and, if the 'M' bit is set in the RA 90 message) it then sends a DHCPv6 Solicit message to elicit a Reply 91 message from a DHCPv6 server that is authoritative for the link 92 (assuming DHCPv6 Rapid Commit). This two round-trip message exchange 93 can add delay as well as waste critical link bandwidth on low-end 94 links (e.g., VHF wireless). 96 This document proposes a new IPv6 ND option called the "DHCPv6 97 Option" that marries the IPv6 ND router discovery and DHCPv6 managed 98 address/prefix acquisition processes into a single round trip message 99 exchange. Nodes include the DHCPv6 option in RS messages to solicit 100 an RA message with a DHCPv6 option in return. This allows the IPv6 101 ND and DHCPv6 functions to work together to supply the client with 102 all needed configuration information in a single message exchange 103 instead of multiple. 105 The following sections present considerations for nodes that employ 106 the IPv6 ND DHCPv6 option. 108 2. The DHCPv6 Option 110 The DHCPv6 option is a new IPv6 ND option that simply embeds a 111 standard DHCPv6 message per section 6 of [RFC3315], beginning with 112 the msg-type followed by the transaction-id and all DHCPv6 options. 113 The format of the option is as follows: 115 0 1 2 3 116 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 1 117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 | Type = TBD | Length | Reserved | 119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 | msg-type | transaction-id | 121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 122 | | 123 . options . 124 . (variable) . 125 | | 126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 128 Figure 1: IPv6 ND DHCPv6 Option Format 130 In this format, Type and Length are exactly as defined in Section 4.6 131 of [RFC4861], a two-octet Reserved field is included for alignment 132 and potential future use, and the rest of the option is exactly as 133 defined in Section 6 of [RFC3315] (in the above, the field labeled 134 "options" refers to DHCPv6 options, i.e., and not additional IPv6 ND 135 options). The length of the full DHCPv6 message itself is determined 136 by the Length field in the IPv6 ND option header. 138 3. DHCPv6 Option Usage 140 When a node first comes onto the link, it creates a Router 141 Solicitation (RS) message containing a DHCPv6 option that embeds a 142 DHCPv6 Solicit message. The node then sends the RS message either to 143 the unicast address of a specific router on the link, or to the All- 144 Routers multicast address. 146 When a router receives an RS message with a DHCPv6 option, if it does 147 not recognize the option and/or does not employ a DHCPv6 relay agent 148 or server, it returns a Router Advertisement (RA) message as normal 149 and without including a DHCPv6 option. By receiving the RA message 150 with no DHCPv6 option, the node can determine that router does not 151 recognize the option an/or does not support a DHCPv6 relay/server 152 function. In this way, no harm will have come from the node 153 including the DHCPv6 option in the RS, and the function is fully 154 backwards compatible. 156 When a router receives an RS message with a DHCPv6 option, if it 157 recognizes the option and employs a DHCPv6 relay agent or server, it 158 extracts the DHCPv6 message from the RS message and forwards the 159 message to the DHCPv6 relay agent or server. When the DHCPv6 message 160 reaches a DHCPv6 server, the server processes the DHCPv6 Solicit 161 message and prepares a DHCPv6 Reply message containing any delegated 162 addresses, prefixes and/or any other information the server is 163 configured to send. The server then returns the Reply message to the 164 router. 166 When the router receives the DHCPv6 Reply message, it creates a 167 Router Advertisement (RA) message that includes any autoconfiguration 168 information necessary for the link and also embeds the Reply message 169 in a DHCPv6 option within the body of the RA. The router then 170 returns the RA as a unicast message reply to the node that sent the 171 RS. 173 At any time after the initial RS/RA exchange, the node may need to 174 issue a DHCPv6 Renew, Release or Rebind message, e.g., to extend 175 address/prefix lifetimes. In that case, the node prepares a DHCPv6 176 message option and inserts it in an RS message which it then sends 177 via unicast to the router. The router in turn processes the message 178 the same as for DHCPv6 Solicit/Reply. 180 At any time after the initial RS/RA exchange, the DHCPv6 server may 181 need to issue a DHCPv6 Reconfigure message. In that case, when the 182 router receives the DHCPv6 Reconfigure message it prepares a unicast 183 RA message with a DHCPv6 option that encodes the Reconfigure and 184 sends the RA as an unsolicited unicast message to the node. 186 4. Implementation Considerations 188 The IPv6ND function and DHCPv6 function are typically implemented in 189 separate router modules. In that case, the IPv6 ND function extracts 190 the DHCPv6 message from the option included in the RS message and 191 wraps it in IP/UDP headers. The source address in the IP header is 192 set to one of the router's unicast addresses, and the source port in 193 the UDP header is set to the port number associated with the IPv6 ND 194 function. The IPv6 ND function then acts as a Lightweight DHCPv6 195 Relay Agent (LDRA) [RFC6221] to forward the message to the DHCPv6 196 relay or server function on-board the router. 198 The forwarded DHCPv6 message then traverses any additional relays on 199 the reverse path until it reaches the DHCPv6 server. When the DHCPv6 200 server processes the message, it delegates any necessary resources 201 and sends a Reply via the same relay agent path as had occurred on 202 the reverse path so that the Reply will eventually arrive back at the 203 IPv6 ND function. The IPv6 ND function then prepares an RA message 204 with any autoconfiguration information associated with the link, 205 embeds the DHCPv6 message body in an IPv6 ND DHCPv6 option, and 206 returns the message via unicast to the node that sent the RS. 208 In a preferred implementation, however, the IPv6ND and DHCPv6 209 functions could be co-located in the same module on the router. In 210 that way the two functions would be coupled as though they were in 211 fact a single unified function without the need for any IP/UDP 212 encapsulation or LDRA processing. 214 5. IANA Considerations 216 The IANA is instructed to assign an IPv6 ND option Type value TBD for 217 the DHCPv6 option. 219 6. Security Considerations 221 Security considerations for IPv6 Neighbor Discovery [RFC4861] and 222 DHCPv6 [RFC3315][RFC3633] apply to this document. 224 . 226 7. Acknowledgements 228 This work was motivated by discussions on the 6man and v6ops list. 230 This work is aligned with the NASA Safe Autonomous Systems Operation 231 (SASO) program under NASA contract number NNA16BD84C. 233 This work is aligned with the FAA as per the SE2025 contract number 234 DTFAWA-15-D-00030. 236 This work is aligned with the Boeing Information Technology (BIT) 237 MobileNet program and the Boeing Research & Technology (BR&T) 238 enterprise autonomy program. 240 8. References 242 8.1. Normative References 244 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 245 C., and M. Carney, "Dynamic Host Configuration Protocol 246 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 247 2003, . 249 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 250 Host Configuration Protocol (DHCP) version 6", RFC 3633, 251 DOI 10.17487/RFC3633, December 2003, 252 . 254 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 255 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 256 DOI 10.17487/RFC4861, September 2007, 257 . 259 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 260 (IPv6) Specification", STD 86, RFC 8200, 261 DOI 10.17487/RFC8200, July 2017, 262 . 264 8.2. Informative References 266 [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. 267 Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221, 268 DOI 10.17487/RFC6221, May 2011, 269 . 271 Author's Address 273 Fred L. Templin (editor) 274 Boeing Research & Technology 275 P.O. Box 3707 276 Seattle, WA 98124 277 USA 279 Email: fltemplin@acm.org