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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) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 dhc Working Group R. Droms 3 Internet-Draft R. Penno 4 Intended status: Standards Track Cisco Systems, Inc. 5 Expires: June 20, 2013 December 17, 2012 7 Container Option for Server Configuration 8 draft-ietf-dhc-container-opt-06.txt 10 Abstract 12 In some DHCP service deployments, it is desirable for a DHCP server 13 in one administrative domain to pass configuration options to a DHCP 14 server in a different administrative domain. This DHCP option 15 carries a set of DHCP options that can be used by another DHCP 16 server. 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 June 20, 2013. 35 Copyright Notice 37 Copyright (c) 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 3. Problem statement and requirements for RG DHCP 55 server configuration . . . . . . . . . . . . . . . . . . . . . 4 56 4. Design alternatives . . . . . . . . . . . . . . . . . . . . . . 5 57 5. Semantics and syntax of the Container option . . . . . . . . . 6 58 5.1. DHCPv4 Container option . . . . . . . . . . . . . . . . . . 6 59 5.2. DHCPv6 Container option . . . . . . . . . . . . . . . . . . 6 60 5.3. SP server behavior . . . . . . . . . . . . . . . . . . . . 7 61 5.4. RG client behavior . . . . . . . . . . . . . . . . . . . . 7 62 5.5. RG server behavior . . . . . . . . . . . . . . . . . . . . 7 63 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 64 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 65 8. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 8 66 8.1. Revision -02 . . . . . . . . . . . . . . . . . . . . . . . 8 67 8.2. Revision -03 . . . . . . . . . . . . . . . . . . . . . . . 9 68 8.3. Revision -04 . . . . . . . . . . . . . . . . . . . . . . . 9 69 9. Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 9 70 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 71 10.1. Normative References . . . . . . . . . . . . . . . . . . . 9 72 10.2. Informative References . . . . . . . . . . . . . . . . . . 9 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 75 1. Introduction 77 In some DHCP service deployments, it is desirable to pass 78 configuration options from a DHCP server in one administrative domain 79 to another DHCP server in a different administrative domain. In one 80 example of such a deployment, an IPTV service provider (SP) may need 81 to provide certain SP domain-specific information to IPTV device(s) 82 located in the consumer domain. This information is sent from the 83 IPTV SP DHCP server to the consumer DHCP server located in the 84 Residential Gateway (RG), which can then be passed along to IPTV 85 device(s) in the subscriber network. 87 Existing RGs may pass some configuration information received by the 88 RG DHCP client to the RG server for configuration of devices attached 89 to the consumer network. There are several motivations for this 90 option: 92 o The devices attached to the consumer network may require different 93 configuration information than the DHCP options provided to the 94 RG. 96 o Existing RG DHCP clients are typically not coded to process new 97 DHCP options and, therefore, will be unable to pass those new 98 options to the RG DHCP server. 100 o Existing RG DHCP clients are typically coded to pass only a fixed 101 list of DHCP options to the RG DHCP server and, therefore, will be 102 unable to pass newly defined options to the RG DHCP server. 104 The DHCP Container option defined in this document provides a 105 mechanism through which the RG DHCP client can pass DHCP options to 106 the RG DHCP server without explicit knowledge of the semantics of 107 those options. With this option, the SP DHCP server can pass both 108 current and future DHCP options to the RG DHCP server. 110 The DHCP Container option does not carry IP addresses, IPv6 prefixes 111 or other information about leases. It carries other configuration 112 information. 114 2. Terminology 116 The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, 117 SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL in this document are to be 118 interpreted as described in RFC2119 [RFC2119]. 120 The following terms and acronyms are used in this document: 122 DHCPv4 "Dynamic Host Configuration Protocol" [RFC2131] 124 DHCPv6 "Dynamic Host Configuration Protocol for IPv6" 125 [RFC3315] 127 DHCP DHCPv4 and/or DHCPv6 129 RG "residential gateway"; the device through which 130 the consumer network connects to the broadband 131 WAN; typically a layer 3 forwarding device 133 RG DHCP client (or "RG client") the DHCP client in the RG 135 RG DHCP server (or "RG server") the DHCP server in the RG 137 SP DHCP server (or "SP server") the DHCP server managed by the 138 service provider (SP) 140 This document uses other terminology for DHCPv4 and DHCPv6 as defined 141 in RFC 2131 and RFC 3315, respectively. 143 3. Problem statement and requirements for RG DHCP server 144 configuration 146 The following diagram shows the components in a network deployment 147 using the DHCP Container option: 149 Client host -+ +---------+ +------+ 150 | | RG | | SP | 151 Client host -+ | Client+--- ... ---+ DHCP | 152 +--+Server | |server| 153 Client host -+ +---------+ +------+ 155 In this diagram, the RG client engages in DHCP message exchanges with 156 the SP server to obtain its IP address and other configuration 157 information. 159 The problem under consideration in this document is to transmit 160 configuration information from the SP DHCP server to hosts, such as 161 computers and set-top boxes, attached to the consumer network. The 162 problem solution has the following requirements: 164 o The SP server MUST be able to transmit different configuration 165 information to the consumer devices than the DHCP options provided 166 to the RG. 168 o The SP server MUST be able to control which DHCP options are 169 transmitted to the consumer device. 171 o There MUST be a way for the SP server to pass DHCP options to be 172 defined in the future to consumer devices. 174 4. Design alternatives 176 The following three designs meet the solution requirements: 178 o SP server passes container option to RG client, which forwards 179 contents to RG server; this alternative is the preferred solution 181 o RG server does direct DHCP info request to SP server; this 182 alternative is not preferred because it: 184 * requires that the RG server include a DHCP client, 186 * requires that the SP server be able to differentiate between RG 187 client and server requests, and it 189 * does not scale well, as it at least doubles the load on the SP 190 server. 192 o RG server passes device requests to SP DHCP server; this 193 alternative is not preferred because it: 195 * requires that the RG also function as a DHCP relay, 197 * requires that the RG relay function be configured with the IP 198 addresses of the SP DHCP server(s), and it 200 * requires that the RG relay function differentiate between DHCP 201 messages that are processed by the RG server and DHCP messages 202 that are processes by the SP server, which does not scale well. 204 A variant on the preferred design would allow the inclusion of 205 multiple sets of DHCP options intended for different classes of 206 devices in the consumer network; e.g., the design would allow for one 207 set of options for video set-top boxes and a second set of options 208 for VoIP MTAs. The variant would require the specification of rules 209 to be provided by the SP server through which the RG server would 210 differentiate its clients and send the appropriate set of options to 211 each device. At present, there is no requirement for differential 212 configuration of consumer devices and this alternative is not defined 213 in this document. 215 5. Semantics and syntax of the Container option 217 Along with configuration information intended for the RG, the SP 218 server can include the DHCP Container option. When the RG client 219 receives the DHCP Container option, it passes the contents of the 220 option to the RG server. The means through which the information is 221 passed between the RG client and the RG server is out of the scope of 222 this document and left unspecified. 224 The DHCP options in this container are carried in DHCP message format 225 (option-code/length/value). In this format, the contained options 226 can be passed through a DHCP client to a co-located DHCP server 227 without specific knowledge on the part of the client or the server of 228 the semantics of the options. 230 5.1. DHCPv4 Container option 232 The DHCPv4 Container option has the following format: 234 0 1 2 3 235 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 1 236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 237 | Code | len | DHCP Options for RG server | 238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . 239 . . 240 . . 241 . . 242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 244 Code OPTION_CONTAINER_V4 (TBDv4) 246 len Length of options for RG server, in octets 248 5.2. DHCPv6 Container option 250 The DHCPv6 Container option has the following format: 252 0 1 2 3 253 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 1 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 | OPTION_CONTAINER_V6 | option-len | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | DHCP Options for RG server | 258 . . 259 . . 260 . . 261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 option-code OPTION_CONTAINER_V6 (TBDv6). 265 option-len Length of options for RG server, in octets 267 5.3. SP server behavior 269 The SP server MAY include the Container option in any DHCP message 270 sent to an RG client. 272 The policy through which the SP server is instructed to include a 273 Container option for an RG client, and the policy determining the 274 contents of the Container object are out of scope of this document 275 and left unspecified. 277 5.4. RG client behavior 279 The RG client MUST pass the contents of the received Container option 280 to the RG server without alteration. The details of the 281 implementation through which the RG client parses the content of the 282 Container option and passes the options to the RG server are out of 283 scope for this document and left unspecified. 285 5.5. RG server behavior 287 The RG server MUST discard any options related to IP address 288 assignment, IPv6 prefix delegation or operation of the DHCP protocol 289 itself. 291 The Container option provides a mechanism through which the SP might 292 be able to unilaterally control the configuration settings passed 293 from a RG DHCP server to a host in the subscriber network. This 294 configuration channel must be handled with some care if the 295 subscriber is to retain desired control over the host configurations. 296 The following behaviors limit the degree to which the SP can control 297 host configuration: 299 o The RG server MAY discard any undesired options, as determined by 300 policy in the RG. 302 o The RG server MUST return to any DHCP client only those options 303 requested by the DHCP client in a Parameter Request List option 304 (DHCPv4 option code 55) or an Option Request option (DHCPv6 option 305 code 6). 307 6. Security Considerations 309 A rogue server can use this option to pass invalid information to the 310 RG client, which would then be passed to the Client hosts. This 311 invalid information could be used to mount a denial of service attack 312 or a man-in-the-middle attack against some applications. 314 Authentication of DHCP messages (RFC 3118 [RFC3118] and section 20 of 315 RFC 3315 [RFC3315]) can be used to ensure that the contents of this 316 option are not altered in transit between the DHCP server and client. 318 7. IANA Considerations 320 When this document is published, IANA is asked to assign an option 321 tag from the "BOOTP Vendor Extensions and DHCP Options" registry for 322 OPTION_CONTAINER_V4 (TBDv4). 324 When this document is published, IANA is asked to assign an option 325 code from the "DHCPv6 Option Codes" registry for OPTION_CONTAINER_V6 326 (TBDv6). 328 8. Change Log 330 If this document is accepted for publication as an RFC, this change 331 log is to be removed before publication. 333 8.1. Revision -02 335 o Corrected a cut-and-paste error in section "DHCPv6 Container 336 option": The Time Protocol Servers option -> The DHCPv4 Container 337 option 339 o Added text to section "RG Server Behavior" to address policy 340 management concerns 342 8.2. Revision -03 344 Corrected several typos (thanks to Alfred Hoenes for his review). 346 8.3. Revision -04 348 Corrected additional typos (again, thanks to Alfred Hoenes for his 349 review). 351 Added pointer to "CableLabs' DHCP Options Registry" as background for 352 this option. 354 9. Related Work 356 The Container option is based on the CableLabs eRouter DHCP Container 357 vendor-identifying vendor-specific option, as defined in "CableLabs' 358 DHCP Options Registry" [eRouter]. 360 10. References 362 10.1. Normative References 364 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 365 Requirement Levels", BCP 14, RFC 2119, March 1997. 367 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 368 RFC 2131, March 1997. 370 [RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP 371 Messages", RFC 3118, June 2001. 373 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 374 and M. Carney, "Dynamic Host Configuration Protocol for 375 IPv6 (DHCPv6)", RFC 3315, July 2003. 377 10.2. Informative References 379 [eRouter] CableLabs, "CableLabs' DHCP Options Registry (CL-SP-CANN- 380 DHCP-Reg-I02-080306)", March 2008. 382 Authors' Addresses 384 Ralph Droms 385 Cisco Systems, Inc. 386 1414 Massachusetts Avenue 387 Boxborough, MA 01719 388 USA 390 Phone: +1 978.936.1674 391 Email: rdroms@cisco.com 393 Reinaldo Penno 394 Cisco Systems, Inc. 395 170 West Tasman Drive 396 San Jose, CA 95134 397 USA 399 Email: repenno@cisco.com