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Droms 3 Internet-Draft Cisco Systems 4 Updates: 3315 (if approved) August 20, 2013 5 Intended status: Standards Track 6 Expires: February 21, 2014 8 Modification to Default Values of SOL_MAX_RT and INF_MAX_RT 9 draft-ietf-dhc-dhcpv6-solmaxrt-update-03 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 a new value. 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 February 21, 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 1. Introduction 52 Section 5.5 of the DHCPv6 specification [RFC3315] defines the default 53 values of SOL_MAX_RT and INF_MAX_RT to be 120 seconds. In some 54 circumstances, these defaults will lead to an unacceptably high 55 volume of aggregated traffic at a DHCPv6 server. 57 The change to SOL_MAX_RT is in response to DHCPv6 message rates 58 observed at a DHCPv6 server in a deployment in which many DHCPv6 59 clients are sending Solicit messages but the DHCPv6 server has been 60 configured not to respond to those Solicit messages. While no 61 explicit observations of traffic due to INF_MAX_RT have been 62 conducted, this document updates INF_MAX_RT for consistency with 63 SOL_MAX_RT. 65 2. Requirements Language 67 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 68 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 69 document are to be interpreted as described in RFC 2119 [RFC2119]. 71 3. Updates to SOL_MAX_RT and INF_MAX_RT in RFC 3315 73 This document changes section 5.5 of RFC 3315 [RFC3315] as follows: 75 OLD: 76 SOL_MAX_RT 120 secs Max Solicit timeout value 78 NEW: 79 SOL_MAX_RT 3600 secs Max Solicit timeout value 81 OLD: 82 INF_MAX_RT 120 secs Max Information-request timeout value 84 NEW: 85 SOL_MAX_RT 3600 secs Max Information-request timeout value 87 With this change, a DHCPv6 client that does not receive a 88 satisfactory response will send Solicit or Information-request 89 messages with the same initial frequency and exponential backoff as 90 specified in sections 17.1.2 and 18.1.5 of RFC 3315 [RFC3315]. 91 However, the long term behavior of these DHCPv6 clients will be to 92 send a Solicit or Information-request message every 3600 seconds 93 rather than every 120 seconds, significantly reducing the aggregated 94 traffic at the DHCPv6 server. 96 4. SOL_MAX_RT option 98 A DHCPv6 server sends the SOL_MAX_RT option to a client to override 99 the default value of SOL_MAX_RT. The value of SOL_MAX_RT in the 100 option replaces the default value defined in Section 3. One use for 101 the SOL_MAX_RT option is to set a longer value for SOL_MAX_RT, which 102 reduces the Solicit traffic from a client that has not received a 103 response to its Solicit messages. 105 The format of the SOL_MAX_RT option is: 107 0 1 2 3 108 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 1 109 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 110 | option-code | option-len | 111 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 112 | SOL_MAX_RT value | 113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 115 option-code OPTION_SOL_MAX_RT (TBD). 117 option-len 4. 119 SOL_MAX_RT value Overriding value for SOL_MAX_RT 120 in seconds; MUST be in range: 121 60 <= "value" <= 86400 (1 day) 123 Figure 1 125 5. INF_MAX_RT option 127 A DHCPv6 server sends the INF_MAX_RT option to a client to override 128 the default value of INF_MAX_RT. The value of INF_MAX_RT in the 129 option replaces the default value defined in Section 3. One use for 130 the INF_MAX_RT option is to set a longer value for INF_MAX_RT, which 131 reduces the Information-Request traffic from a client that has not 132 received a response to its Information-Request messages. 134 The format of the INF_MAX_RT option is: 136 0 1 2 3 137 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 1 138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 139 | option-code | option-len | 140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 141 | INF_MAX_RT value | 142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 144 option-code OPTION_INF_MAX_RT (TBD). 146 option-len 4. 148 INF_MAX_RT value Overriding value for INF_MAX_RT 149 in seconds; MUST be in range: 150 60 <= "value" <= 86400 (1 day) 152 Figure 2: INF_MAX_RT option format 154 6. Updates for SOL_MAX_RT and INF_MAX_RT options to RFC 3315 156 Update to RFC 3315 [RFC3315], section 17.1.3: 158 OLD: 160 The client MUST ignore any Advertise message that includes a Status 161 Code option containing the value NoAddrsAvail, with the exception 162 that the client MAY display the associated status message to the 163 user. 165 NEW: 167 The client MUST ignore any Advertise message that includes a Status 168 Code option containing the value NoAddrsAvail, with the exception 169 that the client MUST process an included SOL_MAX_RT option and/or an 170 included INF_MAX_RT option and MAY display the associated status 171 message to the user. 173 Update to RFC 3315 [RFC3315], section 17.2.2: 175 OLD: 177 If the server will not assign any addresses to any IAs in a 178 subsequent Request from the client, the server MUST send an 179 Advertise message to the client that includes only a Status Code 180 option with code NoAddrsAvail and a status message for the user, a 181 Server Identifier option with the server's DUID, and a Client 182 Identifier option with the client's DUID. 184 NEW: 186 If the server will not assign any addresses to any IAs in a 187 subsequent Request from the client, the server MUST send an 188 Advertise message to the client that includes only a Status Code 189 option with code NoAddrsAvail and a status message for the user, a 190 Server Identifier option with the server's DUID, a Client 191 Identifier option with the client's DUID and (optionally) 192 SOL_MAX_RT and/or INF_MAX_RT options. 194 Add text to the end of section 14, clarifying client behavior while 195 waiting for a response from a server: 197 NEW: 199 A client is not expected to listen for a response during the entire 200 period between transmission of Solicit or Information-Request 201 messages. 203 7. DHCPv6 Client Behavior 205 A DHCPv6 client MUST include the SOL_MAX_RT option code in an Option 206 Request option [RFC3315] in any message it sends. 208 A DHCPv6 client MUST include the INF_MAX_RT option code in an Option 209 Request option [RFC3315] in any message it sends. 211 a DHCPv6 client MUST silently ignore any SOL_MAX_RT or INF_MAX_RT 212 values that are less than 60 or more than 86400. 214 If a DHCPv6 client receives a message containing a SOL_MAX_RT option 215 containing a valid value for SOL_MAX_RT, the client MUST set its 216 internal SOL_MAX_RT parameter to the value contained in the 217 SOL_MAX_RT option. This value of SOL_MAX_RT is then used by the 218 retransmission mechanism defined in sections 17.1.2 and 14 of RFC 219 3315 [RFC3315]. 221 If a DHCPv6 client receives a message containing a INF_MAX_RT option 222 containing a valid value for INF_MAX_RT, the client MUST set its 223 internal INF_MAX_RT parameter to the value contained in the 224 INF_MAX_RT option. This value of INF_MAX_RT is then used by the 225 retransmission mechanism defined in sections 18.1.5 and 14 of RFC 226 3315 [RFC3315]. 228 8. DHCPv6 Server Behavior 230 Sections 17.2.2 and 18.2 of [RFC3315] govern server operation in 231 regards to option assignment. As a convenience to the reader, we 232 mention here that the server will send option SOL_MAX_RT and 233 INF_MAX_RT only if configured with specific values for them and the 234 client requested those options using Option Request Option. 236 The DHCPv6 server MAY include the SOL_MAX_RT option in any response 237 it sends to a client that has included the SOL_MAX_RT option code in 238 an Option Request option. The SOL_MAX_RT option is sent in the main 239 body of the message to client, not as a encapsulated option in, e.g., 240 an IA_NA, IA_TA [RFC3315] or IA_PD [RFC3633] option. 242 The DHCPv6 server MAY include the INF_MAX_RT option in any response 243 it sends to a client that has included the INF_MAX_RT option code in 244 an Option Request option. The INF_MAX_RT option is sent in the main 245 body of the message to client, not as a encapsulated option in, e.g., 246 an IA_NA, IA_TA [RFC3315] or IA_PD [RFC3633] option. 248 9. DHCPv6 Relay Agent Behavior Text 250 There are no additional requirements for relays. 252 10. Security Considerations 254 This document introduces one security consideration beyond those 255 described in RFC 3315 [RFC3315]. A malicious DHCPv6 server might 256 cause a client to set its SOL_MAX_RT and INF_MAX_RT parameters to an 257 arbitrarily high value with the SOL_MAX_RT and INF_MAX_RT options. 258 Assuming the client also receives a response from a valid DHCPv6 259 server, large values for SOL_MAX_RT and INF_MAX_RT will not have any 260 effect. 262 11. Acknowledgments 263 Tomek Mrugalski edited the text for compliance with draft-ietf-dhc- 264 option-guidelines [I-D.ietf-dhc-option-guidelines] and added 265 important detail to the Security Considerations section. 267 12. IANA Considerations 269 IANA is requested to assign one option code each for 270 OPTION_SOL_MAX_RT and OPTION_INF_MAX_RT from the "DHCP Option Codes" 271 table of the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) 272 Registry. 274 13. References 276 13.1. Normative References 278 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 279 Requirement Levels", BCP 14, RFC 2119, March 1997. 281 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 282 and M. Carney, "Dynamic Host Configuration Protocol for 283 IPv6 (DHCPv6)", RFC 3315, July 2003. 285 13.2. Informative References 287 [I-D.ietf-dhc-option-guidelines] 288 Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and 289 S. Krishnan, "Guidelines for Creating New DHCPv6 Options", 290 draft-ietf-dhc-option-guidelines-13 (work in progress), 291 July 2013. 293 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 294 Host Configuration Protocol (DHCP) version 6", RFC 3633, 295 December 2003. 297 Author's Address 299 Ralph Droms 300 Cisco Systems 301 1414 Massachusetts Avenue 302 Boxborough, MA 01719 303 USA 305 Phone: +1 978 936 1674 306 Email: rdroms@cisco.com