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Droms 3 Internet-Draft Cisco Systems 4 Updates: 3315 (if approved) September 14, 2013 5 Intended status: Standards Track 6 Expires: March 18, 2014 8 Modification to Default Values of SOL_MAX_RT and INF_MAX_RT 9 draft-ietf-dhc-dhcpv6-solmaxrt-update-05 11 Abstract 13 This document updates RFC 3315 by redefining the default values for 14 SOL_MAX_RT and INF_MAX_RT, and defining options through which a 15 DHCPv6 server can override the client's default value for SOL_MAX_RT 16 and INF_MAX_RT with new values. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on March 18, 2014. 35 Copyright Notice 37 Copyright (c) 2013 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 54 3. Updates to SOL_MAX_RT and INF_MAX_RT in RFC 3315 . . . . . . 2 55 4. SOL_MAX_RT option . . . . . . . . . . . . . . . . . . . . . . 3 56 5. INF_MAX_RT option . . . . . . . . . . . . . . . . . . . . . . 4 57 6. Updates for SOL_MAX_RT and INF_MAX_RT options to RFC 3315 . . 5 58 7. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . 6 59 8. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . 6 60 9. DHCPv6 Relay Agent Behavior Text . . . . . . . . . . . . . . 7 61 10. Security Considerations . . . . . . . . . . . . . . . . . . . 7 62 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 63 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 64 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 65 13.1. Normative References . . . . . . . . . . . . . . . . . . 8 66 13.2. Informative References . . . . . . . . . . . . . . . . . 8 67 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 69 1. Introduction 71 Section 5.5 of the DHCPv6 specification [RFC3315] defines the default 72 values of SOL_MAX_RT and INF_MAX_RT to be 120 seconds. In some 73 circumstances, these defaults will lead to an unacceptably high 74 volume of aggregated traffic at a DHCPv6 server. 76 The change to SOL_MAX_RT is in response to DHCPv6 message rates 77 observed at a DHCPv6 server in a deployment in which many DHCPv6 78 clients are sending Solicit messages but the DHCPv6 server has been 79 configured not to respond to those Solicit messages. While no 80 explicit observations of traffic due to INF_MAX_RT have been 81 conducted, this document updates INF_MAX_RT for consistency with 82 SOL_MAX_RT. 84 2. Requirements Language 86 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 87 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 88 document are to be interpreted as described in RFC 2119 [RFC2119]. 90 3. Updates to SOL_MAX_RT and INF_MAX_RT in RFC 3315 92 This document changes section 5.5 of RFC 3315 as follows: 94 OLD: 95 SOL_MAX_RT 120 secs Max Solicit timeout value 97 NEW: 99 SOL_MAX_RT 3600 secs Max Solicit timeout value 101 OLD: 102 INF_MAX_RT 120 secs Max Information-request timeout value 104 NEW: 105 SOL_MAX_RT 3600 secs Max Information-request timeout value 107 With this change, a DHCPv6 client that does not receive a 108 satisfactory response will send Solicit or Information-request 109 messages with the same initial frequency and exponential backoff as 110 specified in sections 17.1.2 and 18.1.5 of RFC 3315. However, the 111 long term behavior of these DHCPv6 clients will be to send a Solicit 112 or Information-request message every 3600 seconds rather than every 113 120 seconds, significantly reducing the aggregated traffic at the 114 DHCPv6 server. 116 4. SOL_MAX_RT option 118 A DHCPv6 server sends the SOL_MAX_RT option to a client to override 119 the default value of SOL_MAX_RT. The value of SOL_MAX_RT in the 120 option replaces the default value defined in Section 3. One use for 121 the SOL_MAX_RT option is to set a longer value for SOL_MAX_RT, which 122 reduces the Solicit traffic from a client that has not received a 123 response to its Solicit messages. 125 The format of the SOL_MAX_RT option is: 127 0 1 2 3 128 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 1 129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 | option-code | option-len | 131 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 | SOL_MAX_RT value | 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 option-code OPTION_SOL_MAX_RT (TBD). 137 option-len 4. 139 SOL_MAX_RT value Overriding value for SOL_MAX_RT 140 in seconds; MUST be in range: 141 60 <= "value" <= 86400 (1 day) 143 Figure 1: SOL_MAX_RT option format 145 5. INF_MAX_RT option 147 A DHCPv6 server sends the INF_MAX_RT option to a client to override 148 the default value of INF_MAX_RT. The value of INF_MAX_RT in the 149 option replaces the default value defined in Section 3. One use for 150 the INF_MAX_RT option is to set a longer value for INF_MAX_RT, which 151 reduces the Information-Request traffic from a client that has not 152 received a response to its Information-Request messages. 154 The format of the INF_MAX_RT option is: 156 0 1 2 3 157 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 1 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 159 | option-code | option-len | 160 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 161 | INF_MAX_RT value | 162 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 164 option-code OPTION_INF_MAX_RT (TBD). 166 option-len 4. 168 INF_MAX_RT value Overriding value for INF_MAX_RT 169 in seconds; MUST be in range: 170 60 <= "value" <= 86400 (1 day) 172 Figure 2: INF_MAX_RT option format 174 6. Updates for SOL_MAX_RT and INF_MAX_RT options to RFC 3315 176 Update to RFC 3315, section 17.1.3: 178 OLD: 180 The client MUST ignore any Advertise message that includes a Status 181 Code option containing the value NoAddrsAvail, with the exception 182 that the client MAY display the associated status message to the 183 user. 185 NEW: 187 The client MUST ignore any Advertise message that includes a Status 188 Code option containing the value NoAddrsAvail, with the exception 189 that the client MUST process an included SOL_MAX_RT option and MUST 190 process an included INF_MAX_RT option and MAY display the associated 191 status message to the user. 193 Update to RFC 3315, section 17.2.2: 195 OLD: 197 If the server will not assign any addresses to any IAs in a 198 subsequent Request from the client, the server MUST send an 199 Advertise message to the client that includes only a Status Code 200 option with code NoAddrsAvail and a status message for the user, a 201 Server Identifier option with the server's DUID, and a Client 202 Identifier option with the client's DUID. 204 NEW: 206 If the server will not assign any addresses to any IAs in a 207 subsequent Request from the client, the server MUST send an 208 Advertise message to the client that includes only a Status Code 209 option with code NoAddrsAvail and a status message for the user, a 210 Server Identifier option with the server's DUID, a Client 211 Identifier option with the client's DUID and (optionally) 212 SOL_MAX_RT and/or INF_MAX_RT options. 214 Add text to the end of section 14, clarifying client behavior while 215 waiting for a response from a server: 217 NEW: 219 A client is not expected to listen for a response during the entire 220 period between transmission of Solicit or Information-Request 221 messages. 223 7. DHCPv6 Client Behavior 225 A DHCPv6 client MUST include the SOL_MAX_RT option code in any Option 226 Request option [RFC3315] it sends as required by RFC 3315. 228 A DHCPv6 client MUST include the INF_MAX_RT option code in any Option 229 Request option it sends as required by RFC 3315. 231 A DHCPv6 client MUST silently ignore any SOL_MAX_RT or INF_MAX_RT 232 option values that are less than 60 or more than 86400. 234 If a DHCPv6 client receives a message containing a SOL_MAX_RT option 235 containing a valid value for SOL_MAX_RT, the client MUST set its 236 internal SOL_MAX_RT parameter to the value contained in the 237 SOL_MAX_RT option. This value of SOL_MAX_RT is then used by the 238 retransmission mechanism defined in sections 17.1.2 and 14 of RFC 239 3315. 241 If a DHCPv6 client receives a message containing a INF_MAX_RT option 242 containing a valid value for INF_MAX_RT, the client MUST set its 243 internal INF_MAX_RT parameter to the value contained in the 244 INF_MAX_RT option. This value of INF_MAX_RT is then used by the 245 retransmission mechanism defined in sections 18.1.5 and 14 of RFC 246 3315. 248 8. DHCPv6 Server Behavior 250 Sections 17.2.2 and 18.2 of RFC 3315 govern server operation in 251 regards to option assignment. As a convenience to the reader, we 252 mention here that the server will send option SOL_MAX_RT and 253 INF_MAX_RT only if configured with specific values for them and the 254 client requested those options using Option Request Option. 256 The DHCPv6 server MAY include the SOL_MAX_RT option in any response 257 it sends to a client that has included the SOL_MAX_RT option code in 258 an Option Request option. The SOL_MAX_RT option is sent in the main 259 body of the message to client, not as a encapsulated option in, e.g., 260 an IA_NA, IA_TA [RFC3315] or IA_PD [RFC3633] option. 262 The DHCPv6 server MAY include the INF_MAX_RT option in any response 263 it sends to a client that has included the INF_MAX_RT option code in 264 an Option Request option. The INF_MAX_RT option is sent in the main 265 body of the message to client, not as a encapsulated option in, e.g., 266 an IA_NA, IA_TA or IA_PD option. 268 9. DHCPv6 Relay Agent Behavior Text 270 There are no additional requirements for relays. 272 10. Security Considerations 274 This document introduces one security consideration beyond those 275 described in RFC 3315. A malicious DHCPv6 server might cause a 276 client to set its SOL_MAX_RT and INF_MAX_RT parameters to an 277 arbitrarily high value with the SOL_MAX_RT and INF_MAX_RT options, 278 which may cause an undue delay in a client completing its DHCPv6 279 protocol transaction in the case no other valid response is received. 280 Assuming the client also receives a response from a valid DHCPv6 281 server, large values for SOL_MAX_RT and INF_MAX_RT will not have any 282 effect. 284 11. Acknowledgments 286 Tomek Mrugalski edited the text for compliance with draft-ietf-dhc- 287 option-guidelines [I-D.ietf-dhc-option-guidelines] and added 288 important details to the Security Considerations section. 290 12. IANA Considerations 292 IANA is requested to assign one option code each for 293 OPTION_SOL_MAX_RT and OPTION_INF_MAX_RT from the "DHCP Option Codes" 294 table of the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) 295 Registry. 297 13. References 298 13.1. Normative References 300 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 301 Requirement Levels", BCP 14, RFC 2119, March 1997. 303 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 304 and M. Carney, "Dynamic Host Configuration Protocol for 305 IPv6 (DHCPv6)", RFC 3315, July 2003. 307 13.2. Informative References 309 [I-D.ietf-dhc-option-guidelines] 310 Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and 311 S. Krishnan, "Guidelines for Creating New DHCPv6 Options", 312 draft-ietf-dhc-option-guidelines-13 (work in progress), 313 July 2013. 315 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 316 Host Configuration Protocol (DHCP) version 6", RFC 3633, 317 December 2003. 319 Author's Address 321 Ralph Droms 322 Cisco Systems 323 1414 Massachusetts Avenue 324 Boxborough, MA 01719 325 USA 327 Phone: +1 978 936 1674 328 Email: rdroms@cisco.com