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RFC 2119 keyword, line 184: '... of such options MUST be prepared to d...' RFC 2119 keyword, line 186: '... The receiver MUST NOT...' RFC 2119 keyword, line 191: '...equent to this document MUST contain a...' RFC 2119 keyword, line 261: '... the subnet mask option MUST be first....' (65 more instances...) -- The draft header indicates that this document obsoletes draft-ietf-dhc-options-1533update-04.txt, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- -- No information found for rfcdraft-ietf-dhc-options-1533update-04.txt - is the name correct? -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (May 1997) is 9840 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 1531 (ref. '1') (Obsoleted by RFC 1541) ** Obsolete normative reference: RFC 1497 (ref. '2') (Obsoleted by RFC 1533) -- Possible downref: Non-RFC (?) normative reference: ref. '7' ** Downref: Normative reference to an Informational RFC: RFC 1179 (ref. '10') ** Downref: Normative reference to an Experimental RFC: RFC 887 (ref. '11') ** Downref: Normative reference to an Unknown state RFC: RFC 893 (ref. '14') -- Possible downref: Non-RFC (?) normative reference: ref. '17' ** Obsolete normative reference: RFC 1305 (ref. '18') (Obsoleted by RFC 5905) ** Downref: Normative reference to an Informational RFC: RFC 1198 (ref. '21') ** Obsolete normative reference: RFC 1700 (ref. '22') (Obsoleted by RFC 3232) Summary: 19 errors (**), 0 flaws (~~), 2 warnings (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group S. Alexander 2 INTERNET DRAFT Silicon Graphics, Inc. 3 Obsoletes: draft-ietf-dhc-options-1533update-04.txt R. Droms 4 Bucknell University 5 November 1996 6 Expires May 1997 8 DHCP Options and BOOTP Vendor Extensions 9 11 Status of this memo 13 This document is an Internet-Draft. Internet-Drafts are working 14 documents of the Internet Engineering Task Force (IETF), its areas, 15 and its working groups. Note that other groups may also distribute 16 working documents as Internet-Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six months 19 and may be updated, replaced, or obsoleted by other documents at any 20 time. It is inappropriate to use Internet-Drafts as reference 21 material or to cite them other than as ``work in progress.'' 23 To learn the current status of any Internet-Draft, please check the 24 ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow 25 Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), 26 munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or 27 ftp.isi.edu (US West Coast). 29 Abstract 31 The Dynamic Host Configuration Protocol (DHCP) [1] provides a 32 framework for passing configuration information to hosts on a TCP/IP 33 network. Configuration parameters and other control information are 34 carried in tagged data items that are stored in the 'options' field 35 of the DHCP message. The data items themselves are also called 36 "options." 38 This document specifies the current set of DHCP options. Future 39 options will be specified in separate RFCs. The current list of 40 valid options is also available in ftp://ftp.isi.edu/in- 41 notes/iana/assignments [22]. 43 All of the vendor information extensions defined in RFC 1497 [2] may 44 be used as DHCP options. The definitions given in RFC 1497 are 45 included in this document, which supersedes RFC 1497. All of the 46 DHCP options defined in this document, except for those specific to 47 DHCP as defined in section 9, may be used as BOOTP vendor information 49 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 51 extensions. 53 Table of Contents 55 1. Introduction .............................................. 2 56 2. BOOTP Extension/DHCP Option Field Format .................. 4 57 3. RFC 1497 Vendor Extensions ................................ 5 58 4. IP Layer Parameters per Host .............................. 12 59 5. IP Layer Parameters per Interface ........................ 15 60 6. Link Layer Parameters per Interface ....................... 19 61 7. TCP Parameters ............................................ 20 62 8. Application and Service Parameters ........................ 21 63 9. DHCP Extensions ........................................... 29 64 10. Defining new extensions ................................... 35 65 11. Acknowledgements .......................................... 35 66 12. References ................................................ 36 67 13. Security Considerations ................................... 37 68 14. Authors' Addresses ........................................ 37 70 1. Introduction 72 This document specifies options for use with both the Dynamic Host 73 Configuration Protocol and the Bootstrap Protocol. 75 The full description of DHCP packet formats may be found in the DHCP 76 specification document [1], and the full description of BOOTP packet 77 formats may be found in the BOOTP specification document [3]. This 78 document defines the format of information in the last field of DHCP 79 packets ('options') and of BOOTP packets ('vend'). The remainder of 80 this section defines a generalized use of this area for giving 81 information useful to a wide class of machines, operating systems and 82 configurations. Sites with a single DHCP or BOOTP server that is 83 shared among heterogeneous clients may choose to define other, site- 84 specific formats for the use of the 'options' field. 86 Section 2 of this memo describes the formats of DHCP options and 87 BOOTP vendor extensions. Section 3 describes options defined in 88 previous documents for use with BOOTP (all may also be used with 89 DHCP). Sections 4-8 define new options intended for use with both 90 DHCP and BOOTP. Section 9 defines options used only in DHCP. 92 References further describing most of the options defined in sections 93 2-6 can be found in section 12. The use of the options defined in 94 section 9 is described in the DHCP specification [1]. 96 Information on registering new options is contained in section 10. 98 This document updates the definition of DHCP/BOOTP options that 100 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 102 appears in RFC1533. The classing mechanism has been extended to 103 include vendor classes as described in section 8.4 and 9.13. The new 104 procedure for defining new DHCP/BOOTP options in described in section 105 10. Several new options, including NIS+ domain and servers, Mobile 106 IP home agent, SMTP server, TFTP server and Bootfile server, have 107 been added. Text giving definitions used throughout the document has 108 been added in section 1.1. Text emphasizing the need for uniqueness 109 of client-identifiers has been added to section 9.14. 111 1.1 Requirements 113 Throughout this document, the words that are used to define the 114 significance of particular requirements are capitalized. These words 115 are: 117 o "MUST" 119 This word or the adjective "REQUIRED" means that the 120 item is an absolute requirement of this specification. 122 o "MUST NOT" 124 This phrase means that the item is an absolute prohibition 125 of this specification. 127 o "SHOULD" 129 This word or the adjective "RECOMMENDED" means that there 130 may exist valid reasons in particular circumstances to ignore 131 this item, but the full implications should be understood and 132 the case carefully weighed before choosing a different course. 134 o "SHOULD NOT" 136 This phrase means that there may exist valid reasons in 137 particular circumstances when the listed behavior is acceptable 138 or even useful, but the full implications should be understood 139 and the case carefully weighed before implementing any behavior 140 described with this label. 142 o "MAY" 144 This word or the adjective "OPTIONAL" means that this item is 145 truly optional. One vendor may choose to include the item 146 because a particular marketplace requires it or because it 147 enhances the product, for example; another vendor may omit the 148 same item. 150 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 152 1.2 Terminology 154 This document uses the following terms: 156 o "DHCP client" 158 A DHCP client or "client" is an Internet host using DHCP to obtain 159 configuration parameters such as a network address. 161 o "DHCP server" 163 A DHCP server of "server"is an Internet host that returns 164 configuration parameters to DHCP clients. 166 o "binding" 168 A binding is a collection of configuration parameters, including 169 at least an IP address, associated with or "bound to" a DHCP 170 client. Bindings are managed by DHCP servers. 172 2. BOOTP Extension/DHCP Option Field Format 174 DHCP options have the same format as the BOOTP 'vendor extensions' 175 defined in RFC 1497 [2]. Options may be fixed length or variable 176 length. All options begin with a tag octet, which uniquely 177 identifies the option. Fixed-length options without data consist of 178 only a tag octet. Only options 0 and 255 are fixed length. All 179 other options are variable-length with a length octet following the 180 tag octet. The value of the length octet does not include the two 181 octets specifying the tag and length. The length octet is followed 182 by "length" octets of data. 183 Options containing NVT ASCII data SHOULD NOT include a trailing NULL; 184 however, the receiver of such options MUST be prepared to delete 185 trailing nulls if they exist. 186 The receiver MUST NOT 187 require that a trailing null be included in the data. In the case 188 of some variable-length 189 options the length field is a constant but must still be specified. 191 Any options defined subsequent to this document MUST contain a 192 length octet even if the length is fixed or zero. 194 All multi-octet quantities are in network byte-order. 196 When used with BOOTP, the first four octets of the vendor information 197 field have been assigned to the "magic cookie" (as suggested in RFC 198 951). This field identifies the mode in which the succeeding data is 199 to be interpreted. The value of the magic cookie is the 4 octet 201 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 203 dotted decimal 99.130.83.99 (or hexadecimal number 63.82.53.63) in 204 network byte order. 206 All of the "vendor extensions" defined in RFC 1497 are also DHCP 207 options. 209 Option codes 128 to 254 (decimal) are reserved for site-specific 210 options. 212 Except for the options in section 9, all options may be used with 213 either DHCP or BOOTP. 215 Many of these options have their default values specified in other 216 documents. In particular, RFC 1122 [4] specifies default values for 217 most IP and TCP configuration parameters. 219 Many options supply one or more 32-bit IP address. Use of IP 220 addresses rather than fully-qualified Domain Names (FQDNs) may make 221 future renumbering of IP hosts more difficult. Use of these addresses 222 is discouraged at sites that may require renumbering. 224 3. RFC 1497 Vendor Extensions 226 This section lists the vendor extensions as defined in RFC 227 1497. They are defined here for completeness. 229 3.1. Pad Option 231 The pad option can be used to cause subsequent fields to align on 232 word boundaries. 234 The code for the pad option is 0, and its length is 1 octet. 236 Code 237 +-----+ 238 | 0 | 239 +-----+ 241 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 243 3.2. End Option 245 The end option marks the end of valid information in the vendor 246 field. Subsequent octets should be filled with pad options. 248 The code for the end option is 255, and its length is 1 octet. 250 Code 251 +-----+ 252 | 255 | 253 +-----+ 255 3.3. Subnet Mask 257 The subnet mask option specifies the client's subnet mask as per RFC 258 950 [5]. 260 If both the subnet mask and the router option are specified in a DHCP 261 reply, the subnet mask option MUST be first. 263 The code for the subnet mask option is 1, and its length is 4 octets. 265 Code Len Subnet Mask 266 +-----+-----+-----+-----+-----+-----+ 267 | 1 | 4 | m1 | m2 | m3 | m4 | 268 +-----+-----+-----+-----+-----+-----+ 270 3.4. Time Offset 272 The time offset field specifies the offset of the client's subnet in 273 seconds from Coordinated Universal Time (UTC). The offset is 274 expressed as a two's complement 32-bit integer. A positive offset 275 indicates a location east of the zero meridian and a negative offset 276 indicates a location west of the zero meridian. 278 The code for the time offset option is 2, and its length is 4 octets. 280 Code Len Time Offset 281 +-----+-----+-----+-----+-----+-----+ 282 | 2 | 4 | n1 | n2 | n3 | n4 | 283 +-----+-----+-----+-----+-----+-----+ 285 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 287 3.5. Router Option 289 The router option specifies a list of IP addresses for routers on the 290 client's subnet. Routers SHOULD be listed in order of preference. 292 The code for the router option is 3. The minimum length for the 293 router option is 4 octets, and the length MUST always be a multiple 294 of 4. 296 Code Len Address 1 Address 2 297 +-----+-----+-----+-----+-----+-----+-----+-----+-- 298 | 3 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 299 +-----+-----+-----+-----+-----+-----+-----+-----+-- 301 3.6. Time Server Option 303 The time server option specifies a list of RFC 868 [6] time servers 304 available to the client. Servers SHOULD be listed in order of 305 preference. 307 The code for the time server option is 4. The minimum length for 308 this option is 4 octets, and the length MUST always be a multiple of 309 4. 311 Code Len Address 1 Address 2 312 +-----+-----+-----+-----+-----+-----+-----+-----+-- 313 | 4 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 314 +-----+-----+-----+-----+-----+-----+-----+-----+-- 316 3.7. Name Server Option 318 The name server option specifies a list of IEN 116 [7] name servers 319 available to the client. Servers SHOULD be listed in order of 320 preference. 322 The code for the name server option is 5. The minimum length for 323 this option is 4 octets, and the length MUST always be a multiple of 324 4. 326 Code Len Address 1 Address 2 327 +-----+-----+-----+-----+-----+-----+-----+-----+-- 328 | 5 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 329 +-----+-----+-----+-----+-----+-----+-----+-----+-- 331 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 333 3.8. Domain Name Server Option 335 The domain name server option specifies a list of Domain Name System 336 (STD 13, RFC 1035 [8]) name servers available to the client. Servers 337 SHOULD be listed in order of preference. 339 The code for the domain name server option is 6. The minimum length 340 for this option is 4 octets, and the length MUST always be a multiple 341 of 4. 343 Code Len Address 1 Address 2 344 +-----+-----+-----+-----+-----+-----+-----+-----+-- 345 | 6 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 346 +-----+-----+-----+-----+-----+-----+-----+-----+-- 348 3.9. Log Server Option 350 The log server option specifies a list of MIT-LCS UDP log servers 351 available to the client. Servers SHOULD be listed in order of 352 preference. 354 The code for the log server option is 7. The minimum length for this 355 option is 4 octets, and the length MUST always be a multiple of 4. 357 Code Len Address 1 Address 2 358 +-----+-----+-----+-----+-----+-----+-----+-----+-- 359 | 7 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 360 +-----+-----+-----+-----+-----+-----+-----+-----+-- 362 3.10. Cookie Server Option 364 The cookie server option specifies a list of RFC 865 [9] cookie 365 servers available to the client. Servers SHOULD be listed in order 366 of preference. 368 The code for the log server option is 8. The minimum length for this 369 option is 4 octets, and the length MUST always be a multiple of 4. 371 Code Len Address 1 Address 2 372 +-----+-----+-----+-----+-----+-----+-----+-----+-- 373 | 8 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 374 +-----+-----+-----+-----+-----+-----+-----+-----+-- 376 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 378 3.11. LPR Server Option 380 The LPR server option specifies a list of RFC 1179 [10] line printer 381 servers available to the client. Servers SHOULD be listed in order 382 of preference. 384 The code for the LPR server option is 9. The minimum length for this 385 option is 4 octets, and the length MUST always be a multiple of 4. 387 Code Len Address 1 Address 2 388 +-----+-----+-----+-----+-----+-----+-----+-----+-- 389 | 9 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 390 +-----+-----+-----+-----+-----+-----+-----+-----+-- 392 3.12. Impress Server Option 394 The Impress server option specifies a list of Imagen Impress servers 395 available to the client. Servers SHOULD be listed in order of 396 preference. 398 The code for the Impress server option is 10. The minimum length for 399 this option is 4 octets, and the length MUST always be a multiple of 400 4. 402 Code Len Address 1 Address 2 403 +-----+-----+-----+-----+-----+-----+-----+-----+-- 404 | 10 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 405 +-----+-----+-----+-----+-----+-----+-----+-----+-- 407 3.13. Resource Location Server Option 409 This option specifies a list of RFC 887 [11] Resource Location 410 servers available to the client. Servers SHOULD be listed in order 411 of preference. 413 The code for this option is 11. The minimum length for this option 414 is 4 octets, and the length MUST always be a multiple of 4. 416 Code Len Address 1 Address 2 417 +-----+-----+-----+-----+-----+-----+-----+-----+-- 418 | 11 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 419 +-----+-----+-----+-----+-----+-----+-----+-----+-- 421 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 423 3.14. Host Name Option 425 This option specifies the name of the client. The name may or may 426 not be qualified with the local domain name (see section 3.17 for the 427 preferred way to retrieve the domain name). See RFC 1035 for 428 character set restrictions. 430 The code for this option is 12, and its minimum length is 1. 432 Code Len Host Name 433 +-----+-----+-----+-----+-----+-----+-----+-----+-- 434 | 12 | n | h1 | h2 | h3 | h4 | h5 | h6 | ... 435 +-----+-----+-----+-----+-----+-----+-----+-----+-- 437 3.15. Boot File Size Option 439 This option specifies the length in 512-octet blocks of the default 440 boot image for the client. The file length is specified as an 441 unsigned 16-bit integer. 443 The code for this option is 13, and its length is 2. 445 Code Len File Size 446 +-----+-----+-----+-----+ 447 | 13 | 2 | l1 | l2 | 448 +-----+-----+-----+-----+ 450 3.16. Merit Dump File 452 This option specifies the path-name of a file to which the client's 453 core image should be dumped in the event the client crashes. The 454 path is formatted as a character string consisting of characters from 455 the NVT ASCII character set. 457 The code for this option is 14. Its minimum length is 1. 459 Code Len Dump File Pathname 460 +-----+-----+-----+-----+-----+-----+--- 461 | 14 | n | n1 | n2 | n3 | n4 | ... 462 +-----+-----+-----+-----+-----+-----+--- 464 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 466 3.17. Domain Name 468 This option specifies the domain name that client should use when 469 resolving hostnames via the Domain Name System. 471 The code for this option is 15. Its minimum length is 1. 473 Code Len Domain Name 474 +-----+-----+-----+-----+-----+-----+-- 475 | 15 | n | d1 | d2 | d3 | d4 | ... 476 +-----+-----+-----+-----+-----+-----+-- 478 3.18. Swap Server 480 This specifies the IP address of the client's swap server. 482 The code for this option is 16 and its length is 4. 484 Code Len Swap Server Address 485 +-----+-----+-----+-----+-----+-----+ 486 | 16 | n | a1 | a2 | a3 | a4 | 487 +-----+-----+-----+-----+-----+-----+ 489 3.19. Root Path 491 This option specifies the path-name that contains the client's root 492 disk. The path is formatted as a character string consisting of 493 characters from the NVT ASCII character set. 495 The code for this option is 17. Its minimum length is 1. 497 Code Len Root Disk Pathname 498 +-----+-----+-----+-----+-----+-----+--- 499 | 17 | n | n1 | n2 | n3 | n4 | ... 500 +-----+-----+-----+-----+-----+-----+--- 502 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 504 3.20. Extensions Path 506 A string to specify a file, retrievable via TFTP, which contains 507 information which can be interpreted in the same way as the 64-octet 508 vendor-extension field within the BOOTP response, with the following 509 exceptions: 511 - the length of the file is unconstrained; 512 - all references to Tag 18 (i.e., instances of the 513 BOOTP Extensions Path field) within the file are 514 ignored. 516 The code for this option is 18. Its minimum length is 1. 518 Code Len Extensions Pathname 519 +-----+-----+-----+-----+-----+-----+--- 520 | 18 | n | n1 | n2 | n3 | n4 | ... 521 +-----+-----+-----+-----+-----+-----+--- 523 4. IP Layer Parameters per Host 525 This section details the options that affect the operation of the IP 526 layer on a per-host basis. 528 4.1. IP Forwarding Enable/Disable Option 530 This option specifies whether the client should configure its IP 531 layer for packet forwarding. A value of 0 means disable IP 532 forwarding, and a value of 1 means enable IP forwarding. 534 The code for this option is 19, and its length is 1. 536 Code Len Value 537 +-----+-----+-----+ 538 | 19 | 1 | 0/1 | 539 +-----+-----+-----+ 541 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 543 4.2. Non-Local Source Routing Enable/Disable Option 545 This option specifies whether the client should configure its IP 546 layer to allow forwarding of datagrams with non-local source routes 547 (see Section 3.3.5 of [4] for a discussion of this topic). A value 548 of 0 means disallow forwarding of such datagrams, and a value of 1 549 means allow forwarding. 551 The code for this option is 20, and its length is 1. 553 Code Len Value 554 +-----+-----+-----+ 555 | 20 | 1 | 0/1 | 556 +-----+-----+-----+ 558 4.3. Policy Filter Option 560 This option specifies policy filters for non-local source routing. 561 The filters consist of a list of IP addresses and masks which specify 562 destination/mask pairs with which to filter incoming source routes. 564 Any source routed datagram whose next-hop address does not match one 565 of the filters should be discarded by the client. 567 See [4] for further information. 569 The code for this option is 21. The minimum length of this option is 570 8, and the length MUST be a multiple of 8. 572 Code Len Address 1 Mask 1 573 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ 574 | 21 | n | a1 | a2 | a3 | a4 | m1 | m2 | m3 | m4 | 575 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ 576 Address 2 Mask 2 577 +-----+-----+-----+-----+-----+-----+-----+-----+--- 578 | a1 | a2 | a3 | a4 | m1 | m2 | m3 | m4 | ... 579 +-----+-----+-----+-----+-----+-----+-----+-----+--- 581 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 583 4.4. Maximum Datagram Reassembly Size 585 This option specifies the maximum size datagram that the client 586 should be prepared to reassemble. The size is specified as a 16-bit 587 unsigned integer. The minimum value legal value is 576. 589 The code for this option is 22, and its length is 2. 591 Code Len Size 592 +-----+-----+-----+-----+ 593 | 22 | 2 | s1 | s2 | 594 +-----+-----+-----+-----+ 596 4.5. Default IP Time-to-live 598 This option specifies the default time-to-live that the client should 599 use on outgoing datagrams. The TTL is specified as an octet with a 600 value between 1 and 255. 602 The code for this option is 23, and its length is 1. 604 Code Len TTL 605 +-----+-----+-----+ 606 | 23 | 1 | ttl | 607 +-----+-----+-----+ 609 4.6. Path MTU Aging Timeout Option 611 This option specifies the timeout (in seconds) to use when aging Path 612 MTU values discovered by the mechanism defined in RFC 1191 [12]. The 613 timeout is specified as a 32-bit unsigned integer. 615 The code for this option is 24, and its length is 4. 617 Code Len Timeout 618 +-----+-----+-----+-----+-----+-----+ 619 | 24 | 4 | t1 | t2 | t3 | t4 | 620 +-----+-----+-----+-----+-----+-----+ 622 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 624 4.7. Path MTU Plateau Table Option 626 This option specifies a table of MTU sizes to use when performing 627 Path MTU Discovery as defined in RFC 1191. The table is formatted as 628 a list of 16-bit unsigned integers, ordered from smallest to largest. 629 The minimum MTU value cannot be smaller than 68. 631 The code for this option is 25. Its minimum length is 2, and the 632 length MUST be a multiple of 2. 634 Code Len Size 1 Size 2 635 +-----+-----+-----+-----+-----+-----+--- 636 | 25 | n | s1 | s2 | s1 | s2 | ... 637 +-----+-----+-----+-----+-----+-----+--- 639 5. IP Layer Parameters per Interface 641 This section details the options that affect the operation of the IP 642 layer on a per-interface basis. It is expected that a client can 643 issue multiple requests, one per interface, in order to configure 644 interfaces with their specific parameters. 646 5.1. Interface MTU Option 648 This option specifies the MTU to use on this interface. The MTU is 649 specified as a 16-bit unsigned integer. The minimum legal value for 650 the MTU is 68. 652 The code for this option is 26, and its length is 2. 654 Code Len MTU 655 +-----+-----+-----+-----+ 656 | 26 | 2 | m1 | m2 | 657 +-----+-----+-----+-----+ 659 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 661 5.2. All Subnets are Local Option 663 This option specifies whether or not the client may assume that all 664 subnets of the IP network to which the client is connected use the 665 same MTU as the subnet of that network to which the client is 666 directly connected. A value of 1 indicates that all subnets share 667 the same MTU. A value of 0 means that the client should assume that 668 some subnets of the directly connected network may have smaller MTUs. 670 The code for this option is 27, and its length is 1. 672 Code Len Value 673 +-----+-----+-----+ 674 | 27 | 1 | 0/1 | 675 +-----+-----+-----+ 677 5.3. Broadcast Address Option 679 This option specifies the broadcast address in use on the client's 680 subnet. Legal values for broadcast addresses are specified in 681 section 3.2.1.3 of [4]. 683 The code for this option is 28, and its length is 4. 685 Code Len Broadcast Address 686 +-----+-----+-----+-----+-----+-----+ 687 | 28 | 4 | b1 | b2 | b3 | b4 | 688 +-----+-----+-----+-----+-----+-----+ 690 5.4. Perform Mask Discovery Option 692 This option specifies whether or not the client should perform subnet 693 mask discovery using ICMP. A value of 0 indicates that the client 694 should not perform mask discovery. A value of 1 means that the 695 client should perform mask discovery. 697 The code for this option is 29, and its length is 1. 699 Code Len Value 700 +-----+-----+-----+ 701 | 29 | 1 | 0/1 | 702 +-----+-----+-----+ 704 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 706 5.5. Mask Supplier Option 708 This option specifies whether or not the client should respond to 709 subnet mask requests using ICMP. A value of 0 indicates that the 710 client should not respond. A value of 1 means that the client should 711 respond. 713 The code for this option is 30, and its length is 1. 715 Code Len Value 716 +-----+-----+-----+ 717 | 30 | 1 | 0/1 | 718 +-----+-----+-----+ 720 5.6. Perform Router Discovery Option 722 This option specifies whether or not the client should solicit 723 routers using the Router Discovery mechanism defined in RFC 1256 724 [13]. A value of 0 indicates that the client should not perform 725 router discovery. A value of 1 means that the client should perform 726 router discovery. 728 The code for this option is 31, and its length is 1. 730 Code Len Value 731 +-----+-----+-----+ 732 | 31 | 1 | 0/1 | 733 +-----+-----+-----+ 735 5.7. Router Solicitation Address Option 737 This option specifies the address to which the client should transmit 738 router solicitation requests. 740 The code for this option is 32, and its length is 4. 742 Code Len Address 743 +-----+-----+-----+-----+-----+-----+ 744 | 32 | 4 | a1 | a2 | a3 | a4 | 745 +-----+-----+-----+-----+-----+-----+ 747 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 749 5.8. Static Route Option 751 This option specifies a list of static routes that the client should 752 install in its routing cache. If multiple routes to the same 753 destination are specified, they are listed in descending order of 754 priority. 756 The routes consist of a list of IP address pairs. The first address 757 is the destination address, and the second address is the router for 758 the destination. 760 The default route (0.0.0.0) is an illegal destination for a static 761 route. See section 3.5 for information about the router option. 763 The code for this option is 33. The minimum length of this option is 764 8, and the length MUST be a multiple of 8. 766 Code Len Destination 1 Router 1 767 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ 768 | 33 | n | d1 | d2 | d3 | d4 | r1 | r2 | r3 | r4 | 769 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ 770 Destination 2 Router 2 771 +-----+-----+-----+-----+-----+-----+-----+-----+--- 772 | d1 | d2 | d3 | d4 | r1 | r2 | r3 | r4 | ... 773 +-----+-----+-----+-----+-----+-----+-----+-----+--- 775 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 777 6. Link Layer Parameters per Interface 779 This section lists the options that affect the operation of the data 780 link layer on a per-interface basis. 782 6.1. Trailer Encapsulation Option 784 This option specifies whether or not the client should negotiate the 785 use of trailers (RFC 893 [14]) when using the ARP protocol. A value 786 of 0 indicates that the client should not attempt to use trailers. A 787 value of 1 means that the client should attempt to use trailers. 789 The code for this option is 34, and its length is 1. 791 Code Len Value 792 +-----+-----+-----+ 793 | 34 | 1 | 0/1 | 794 +-----+-----+-----+ 796 6.2. ARP Cache Timeout Option 798 This option specifies the timeout in seconds for ARP cache entries. 799 The time is specified as a 32-bit unsigned integer. 801 The code for this option is 35, and its length is 4. 803 Code Len Time 804 +-----+-----+-----+-----+-----+-----+ 805 | 35 | 4 | t1 | t2 | t3 | t4 | 806 +-----+-----+-----+-----+-----+-----+ 808 6.3. Ethernet Encapsulation Option 810 This option specifies whether or not the client should use Ethernet 811 Version 2 (RFC 894 [15]) or IEEE 802.3 (RFC 1042 [16]) encapsulation 812 if the interface is an Ethernet. A value of 0 indicates that the 813 client should use RFC 894 encapsulation. A value of 1 means that the 814 client should use RFC 1042 encapsulation. 816 The code for this option is 36, and its length is 1. 818 Code Len Value 819 +-----+-----+-----+ 820 | 36 | 1 | 0/1 | 821 +-----+-----+-----+ 823 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 825 7. TCP Parameters 827 This section lists the options that affect the operation of the TCP 828 layer on a per-interface basis. 830 7.1. TCP Default TTL Option 832 This option specifies the default TTL that the client should use when 833 sending TCP segments. The value is represented as an 8-bit unsigned 834 integer. The minimum value is 1. 836 The code for this option is 37, and its length is 1. 838 Code Len TTL 839 +-----+-----+-----+ 840 | 37 | 1 | n | 841 +-----+-----+-----+ 843 7.2. TCP Keepalive Interval Option 845 This option specifies the interval (in seconds) that the client TCP 846 should wait before sending a keepalive message on a TCP connection. 847 The time is specified as a 32-bit unsigned integer. A value of zero 848 indicates that the client should not generate keepalive messages on 849 connections unless specifically requested by an application. 851 The code for this option is 38, and its length is 4. 853 Code Len Time 854 +-----+-----+-----+-----+-----+-----+ 855 | 38 | 4 | t1 | t2 | t3 | t4 | 856 +-----+-----+-----+-----+-----+-----+ 858 7.3. TCP Keepalive Garbage Option 860 This option specifies the whether or not the client should send TCP 861 keepalive messages with a octet of garbage for compatibility with 862 older implementations. A value of 0 indicates that a garbage octet 863 should not be sent. A value of 1 indicates that a garbage octet 864 should be sent. 866 The code for this option is 39, and its length is 1. 868 Code Len Value 869 +-----+-----+-----+ 870 | 39 | 1 | 0/1 | 871 +-----+-----+-----+ 873 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 875 8. Application and Service Parameters 877 This section details some miscellaneous options used to configure 878 miscellaneous applications and services. 880 8.1. Network Information Service Domain Option 882 This option specifies the name of the client's NIS [17] domain. The 883 domain is formatted as a character string consisting of characters 884 from the NVT ASCII character set. 886 The code for this option is 40. Its minimum length is 1. 888 Code Len NIS Domain Name 889 +-----+-----+-----+-----+-----+-----+--- 890 | 40 | n | n1 | n2 | n3 | n4 | ... 891 +-----+-----+-----+-----+-----+-----+--- 893 8.2. Network Information Servers Option 895 This option specifies a list of IP addresses indicating NIS servers 896 available to the client. Servers SHOULD be listed in order of 897 preference. 899 The code for this option is 41. Its minimum length is 4, and the 900 length MUST be a multiple of 4. 902 Code Len Address 1 Address 2 903 +-----+-----+-----+-----+-----+-----+-----+-----+-- 904 | 41 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 905 +-----+-----+-----+-----+-----+-----+-----+-----+-- 907 8.3. Network Time Protocol Servers Option 909 This option specifies a list of IP addresses indicating NTP [18] 910 servers available to the client. Servers SHOULD be listed in order 911 of preference. 913 The code for this option is 42. Its minimum length is 4, and the 914 length MUST be a multiple of 4. 916 Code Len Address 1 Address 2 917 +-----+-----+-----+-----+-----+-----+-----+-----+-- 918 | 42 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 919 +-----+-----+-----+-----+-----+-----+-----+-----+-- 921 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 923 8.4. Vendor Specific Information 925 This option is used by clients and servers to exchange vendor- 926 specific information. The information is an opaque object of n 927 octets, presumably interpreted by vendor-specific code on the clients 928 and servers. The definition of this information is vendor specific. 929 The vendor is indicated in the vendor class identifier option. 930 Servers not equipped to interpret the vendor-specific information 931 sent by a client MUST ignore it (although it may be reported). 932 Clients which do not receive desired vendor-specific information 933 SHOULD make an attempt to operate without it, although they may do so 934 (and announce they are doing so) in a degraded mode. 936 If a vendor potentially encodes more than one item of information in 937 this option, then the vendor SHOULD encode the option using 938 "Encapsulated vendor-specific options" as described below: 940 The Encapsulated vendor-specific options field SHOULD be encoded as a 941 sequence of code/length/value fields of identical syntax to the DHCP 942 options field with the following exceptions: 944 1) There SHOULD NOT be a "magic cookie" field in the encapsulated 945 vendor-specific extensions field. 947 2) Codes other than 0 or 255 MAY be redefined by the vendor within 948 the encapsulated vendor-specific extensions field, but SHOULD 949 conform to the tag-length-value syntax defined in section 2. 951 3) Code 255 (END), if present, signifies the end of the 952 encapsulated vendor extensions, not the end of the vendor 953 extensions field. If no code 255 is present, then the end of 954 the enclosing vendor-specific information field is taken as the 955 end of the encapsulated vendor-specific extensions field. 957 The code for this option is 43 and its minimum length is 1. 959 Code Len Vendor-specific information 960 +-----+-----+-----+-----+--- 961 | 43 | n | i1 | i2 | ... 962 +-----+-----+-----+-----+--- 964 When encapsulated vendor-specific extensions are used, the 965 information bytes 1-n have the following format: 967 Code Len Data item Code Len Data item Code 968 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ 969 | T1 | n | d1 | d2 | ... | T2 | n | D1 | D2 | ... | ... | 970 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ 972 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 974 8.5. NetBIOS over TCP/IP Name Server Option 976 The NetBIOS name server (NBNS) option specifies a list of RFC 977 1001/1002 [19] [20] NBNS name servers listed in order of preference. 979 The code for this option is 44. The minimum length of the option is 980 4 octets, and the length must always be a multiple of 4. 982 Code Len Address 1 Address 2 983 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+---- 984 | 44 | n | a1 | a2 | a3 | a4 | b1 | b2 | b3 | b4 | ... 985 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+---- 987 8.6. NetBIOS over TCP/IP Datagram Distribution Server Option 989 The NetBIOS datagram distribution server (NBDD) option specifies a 990 list of RFC 1001/1002 NBDD servers listed in order of preference. The 991 code for this option is 45. The minimum length of the option is 4 992 octets, and the length must always be a multiple of 4. 994 Code Len Address 1 Address 2 995 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+---- 996 | 45 | n | a1 | a2 | a3 | a4 | b1 | b2 | b3 | b4 | ... 997 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+---- 999 8.7. NetBIOS over TCP/IP Node Type Option 1001 The NetBIOS node type option allows NetBIOS over TCP/IP clients which 1002 are configurable to be configured as described in RFC 1001/1002. The 1003 value is specified as a single octet which identifies the client type 1004 as follows: 1006 Value Node Type 1007 ----- --------- 1008 0x1 B-node 1009 0x2 P-node 1010 0x4 M-node 1011 0x8 H-node 1013 In the above chart, the notation '0x' indicates a number in base-16 1014 (hexadecimal). 1016 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1018 The code for this option is 46. The length of this option is always 1019 1. 1021 Code Len Node Type 1022 +-----+-----+-----------+ 1023 | 46 | 1 | see above | 1024 +-----+-----+-----------+ 1026 8.8. NetBIOS over TCP/IP Scope Option 1028 The NetBIOS scope option specifies the NetBIOS over TCP/IP scope 1029 parameter for the client as specified in RFC 1001/1002. See [19], 1030 [20], and [8] for character-set restrictions. 1032 The code for this option is 47. The minimum length of this option is 1033 1. 1035 Code Len NetBIOS Scope 1036 +-----+-----+-----+-----+-----+-----+---- 1037 | 47 | n | s1 | s2 | s3 | s4 | ... 1038 +-----+-----+-----+-----+-----+-----+---- 1040 8.9. X Window System Font Server Option 1042 This option specifies a list of X Window System [21] Font servers 1043 available to the client. Servers SHOULD be listed in order of 1044 preference. 1046 The code for this option is 48. The minimum length of this option is 1047 4 octets, and the length MUST be a multiple of 4. 1049 Code Len Address 1 Address 2 1050 +-----+-----+-----+-----+-----+-----+-----+-----+--- 1051 | 48 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1052 +-----+-----+-----+-----+-----+-----+-----+-----+--- 1054 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1056 8.10. X Window System Display Manager Option 1058 This option specifies a list of IP addresses of systems that are 1059 running the X Window System Display Manager and are available to the 1060 client. 1062 Addresses SHOULD be listed in order of preference. 1064 The code for the this option is 49. The minimum length of this option 1065 is 4, and the length MUST be a multiple of 4. 1067 Code Len Address 1 Address 2 1069 +-----+-----+-----+-----+-----+-----+-----+-----+--- 1070 | 49 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1071 +-----+-----+-----+-----+-----+-----+-----+-----+--- 1073 8.11. Network Information Service+ Domain Option 1075 This option specifies the name of the client's NIS+ [17] domain. The 1076 domain is formatted as a character string consisting of characters 1077 from the NVT ASCII character set. 1079 The code for this option is 64. Its minimum length is 1. 1081 Code Len NIS Client Domain Name 1082 +-----+-----+-----+-----+-----+-----+--- 1083 | 64 | n | n1 | n2 | n3 | n4 | ... 1084 +-----+-----+-----+-----+-----+-----+--- 1086 8.12. Network Information Service+ Servers Option 1088 This option specifies a list of IP addresses indicating NIS+ servers 1089 available to the client. Servers SHOULD be listed in order of 1090 preference. 1092 The code for this option is 65. Its minimum length is 4, and the 1093 length MUST be a multiple of 4. 1095 Code Len Address 1 Address 2 1096 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1097 | 65 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1098 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1100 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1102 8.13. Mobile IP Home Agent option 1104 This option specifies a list of IP addresses indicating mobile IP 1105 home agents available to the client. Agents SHOULD be listed in 1106 order of preference. 1108 The code for this option is 68. Its minimum length is 0 (indicating 1109 no home agents are available) and the length MUST be a multiple of 4. 1110 It is expected that the usual length will be four octets, containing 1111 a single home agent's address. 1113 Code Len Home Agent Addresses (zero or more) 1114 +-----+-----+-----+-----+-----+-----+-- 1115 | 68 | n | a1 | a2 | a3 | a4 | ... 1116 +-----+-----+-----+-----+-----+-----+-- 1118 8.14. Simple Mail Transport Protocol (SMTP) Server Option 1120 The SMTP server option specifies a list of SMTP servers available to 1121 the client. Servers SHOULD be listed in order of preference. 1123 The code for the SMTP server option is 69. The minimum length for 1124 this option is 4 octets, and the length MUST always be a multiple of 1125 4. 1127 Code Len Address 1 Address 2 1128 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1129 | 69 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1130 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1132 8.15. Post Office Protocol (POP3) Server Option 1134 The POP3 server option specifies a list of POP3 available to the 1135 client. Servers SHOULD be listed in order of preference. 1137 The code for the POP3 server option is 70. The minimum length for 1138 this option is 4 octets, and the length MUST always be a multiple of 1139 4. 1141 Code Len Address 1 Address 2 1142 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1143 | 70 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1144 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1146 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1148 8.16. Network News Transport Protocol (NNTP) Server Option 1150 The NNTP server option specifies a list of NNTP available to the 1151 client. Servers SHOULD be listed in order of preference. 1153 The code for the NNTP server option is 71. The minimum length for 1154 this option is 4 octets, and the length MUST always be a multiple of 1155 4. 1157 Code Len Address 1 Address 2 1158 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1159 | 71 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1160 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1162 8.17. Default World Wide Web (WWW) Server Option 1164 The WWW server option specifies a list of WWW available to the 1165 client. Servers SHOULD be listed in order of preference. 1167 The code for the WWW server option is 72. The minimum length for 1168 this option is 4 octets, and the length MUST always be a multiple of 1169 4. 1171 Code Len Address 1 Address 2 1172 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1173 | 72 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1174 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1176 8.18. Default Finger Server Option 1178 The Finger server option specifies a list of Finger available to the 1179 client. Servers SHOULD be listed in order of preference. 1181 The code for the Finger server option is 73. The minimum length for 1182 this option is 4 octets, and the length MUST always be a multiple of 1183 4. 1185 Code Len Address 1 Address 2 1186 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1187 | 73 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1188 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1190 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1192 8.19. Default Internet Relay Chat (IRC) Server Option 1194 The IRC server option specifies a list of IRC available to the 1195 client. Servers SHOULD be listed in order of preference. 1197 The code for the IRC server option is 74. The minimum length for 1198 this option is 4 octets, and the length MUST always be a multiple of 1199 4. 1201 Code Len Address 1 Address 2 1202 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1203 | 74 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1204 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1206 8.20. StreetTalk Server Option 1208 The StreetTalk server option specifies a list of StreetTalk servers 1209 available to the client. Servers SHOULD be listed in order of 1210 preference. 1212 The code for the StreetTalk server option is 75. The minimum length 1213 for this option is 4 octets, and the length MUST always be a multiple 1214 of 4. 1216 Code Len Address 1 Address 2 1217 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1218 | 75 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1219 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1221 8.21. StreetTalk Directory Assistance (STDA) Server Option 1223 The StreetTalk Directory Assistance (STDA) server option specifies a 1224 list of STDA servers available to the client. Servers SHOULD be 1225 listed in order of preference. 1227 The code for the StreetTalk Directory Assistance server option is 76. 1228 The minimum length for this option is 4 octets, and the length MUST 1229 always be a multiple of 4. 1231 Code Len Address 1 Address 2 1232 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1233 | 76 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... 1234 +-----+-----+-----+-----+-----+-----+-----+-----+-- 1236 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1238 9. DHCP Extensions 1240 This section details the options that are specific to DHCP. 1242 9.1. Requested IP Address 1244 This option is used in a client request (DHCPDISCOVER) to allow the 1245 client to request that a particular IP address be assigned. 1247 The code for this option is 50, and its length is 4. 1249 Code Len Address 1250 +-----+-----+-----+-----+-----+-----+ 1251 | 50 | 4 | a1 | a2 | a3 | a4 | 1252 +-----+-----+-----+-----+-----+-----+ 1254 9.2. IP Address Lease Time 1256 This option is used in a client request (DHCPDISCOVER or DHCPREQUEST) 1257 to allow the client to request a lease time for the IP address. In a 1258 server reply (DHCPOFFER), a DHCP server uses this option to specify 1259 the lease time it is willing to offer. 1261 The time is in units of seconds, and is specified as a 32-bit 1262 unsigned integer. 1264 The code for this option is 51, and its length is 4. 1266 Code Len Lease Time 1267 +-----+-----+-----+-----+-----+-----+ 1268 | 51 | 4 | t1 | t2 | t3 | t4 | 1269 +-----+-----+-----+-----+-----+-----+ 1271 9.3. Option Overload 1273 This option is used to indicate that the DHCP 'sname' or 'file' 1274 fields are being overloaded by using them to carry DHCP options. A 1275 DHCP server inserts this option if the returned parameters will 1276 exceed the usual space allotted for options. 1278 If this option is present, the client interprets the specified 1279 additional fields after it concludes interpretation of the standard 1280 option fields. 1282 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1284 The code for this option is 52, and its length is 1. Legal values 1285 for this option are: 1287 Value Meaning 1288 ----- -------- 1289 1 the 'file' field is used to hold options 1290 2 the 'sname' field is used to hold options 1291 3 both fields are used to hold options 1293 Code Len Value 1294 +-----+-----+-----+ 1295 | 52 | 1 |1/2/3| 1296 +-----+-----+-----+ 1298 9.4 TFTP server name 1300 This option is used to identify a TFTP server when the 'sname' 1301 field in the DHCP header has been used for DHCP options. 1303 The code for this option is 66, and its minimum length is 1. 1305 Code Len TFTP server 1306 +-----+-----+-----+-----+-----+--- 1307 | 66 | n | c1 | c2 | c3 | ... 1308 +-----+-----+-----+-----+-----+--- 1310 9.5 Bootfile name 1312 This option is used to identify a bootfile when the 'file' field in 1313 the DHCP header has been used for DHCP options. 1315 The code for this option is 67, and its minimum length is 1. 1317 Code Len Bootfile name 1318 +-----+-----+-----+-----+-----+--- 1319 | 67 | n | c1 | c2 | c3 | ... 1320 +-----+-----+-----+-----+-----+--- 1322 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1324 9.6. DHCP Message Type 1326 This option is used to convey the type of the DHCP message. The code 1327 for this option is 53, and its length is 1. Legal values for this 1328 option are: 1330 Value Message Type 1331 ----- ------------ 1332 1 DHCPDISCOVER 1333 2 DHCPOFFER 1334 3 DHCPREQUEST 1335 4 DHCPDECLINE 1336 5 DHCPACK 1337 6 DHCPNAK 1338 7 DHCPRELEASE 1339 8 DHCPINFORM 1341 Code Len Type 1342 +-----+-----+-----+ 1343 | 53 | 1 | 1-9 | 1344 +-----+-----+-----+ 1346 9.7. Server Identifier 1348 This option is used in DHCPOFFER and DHCPREQUEST messages, and may 1349 optionally be included in the DHCPACK and DHCPNAK messages. DHCP 1350 servers include this option in the DHCPOFFER in order to allow the 1351 client to distinguish between lease offers. DHCP clients indicate 1352 which of several lease offers is being accepted by including this 1353 option in a DHCPREQUEST message. 1355 The identifier is the IP address of the selected server. 1357 The code for this option is 54, and its length is 4. 1359 Code Len Address 1360 +-----+-----+-----+-----+-----+-----+ 1361 | 54 | 4 | a1 | a2 | a3 | a4 | 1362 +-----+-----+-----+-----+-----+-----+ 1364 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1366 9.8. Parameter Request List 1368 This option is used by a DHCP client to request values for specified 1369 configuration parameters. The list of requested parameters is 1370 specified as n octets, where each octet is a valid DHCP option code 1371 as defined in this document. 1373 The client MAY list the options in order of preference. The DHCP 1374 server is not required to return the options in the requested order, 1375 but MUST try to insert the requested options in the order requested 1376 by the client. 1378 The code for this option is 55. Its minimum length is 1. 1380 Code Len Option Codes 1381 +-----+-----+-----+-----+--- 1382 | 55 | n | c1 | c2 | ... 1383 +-----+-----+-----+-----+--- 1385 9.9. Message 1387 This option is used by a DHCP server to provide an error message to a 1388 DHCP client in a DHCPNAK message in the event of a failure. A client 1389 may use this option in a DHCPDECLINE message to indicate the why the 1390 client declined the offered parameters. The message consists of n 1391 octets of NVT ASCII text, which the client may display on an 1392 available output device. 1394 The code for this option is 56 and its minimum length is 1. 1396 Code Len Text 1397 +-----+-----+-----+-----+--- 1398 | 56 | n | c1 | c2 | ... 1399 +-----+-----+-----+-----+--- 1401 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1403 9.10. Maximum DHCP Message Size 1405 This option specifies the maximum length DHCP message that it is 1406 willing to accept. The length is specified as an unsigned 16-bit 1407 integer. A client may use the maximum DHCP message size option in 1408 DHCPDISCOVER or DHCPREQUEST messages, but should not use the option 1409 in DHCPDECLINE messages. 1411 The code for this option is 57, and its length is 2. The minimum 1412 legal value is 576 octets. 1414 Code Len Length 1415 +-----+-----+-----+-----+ 1416 | 57 | 2 | l1 | l2 | 1417 +-----+-----+-----+-----+ 1419 9.11. Renewal (T1) Time Value 1421 This option specifies the time interval from address assignment until 1422 the client transitions to the RENEWING state. 1424 The value is in units of seconds, and is specified as a 32-bit 1425 unsigned integer. 1427 The code for this option is 58, and its length is 4. 1429 Code Len T1 Interval 1430 +-----+-----+-----+-----+-----+-----+ 1431 | 58 | 4 | t1 | t2 | t3 | t4 | 1432 +-----+-----+-----+-----+-----+-----+ 1434 9.12. Rebinding (T2) Time Value 1436 This option specifies the time interval from address assignment until 1437 the client transitions to the REBINDING state. 1439 The value is in units of seconds, and is specified as a 32-bit 1440 unsigned integer. 1442 The code for this option is 59, and its length is 4. 1444 Code Len T2 Interval 1445 +-----+-----+-----+-----+-----+-----+ 1446 | 59 | 4 | t1 | t2 | t3 | t4 | 1447 +-----+-----+-----+-----+-----+-----+ 1449 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1451 9.13. Vendor class identifier 1453 This option is used by DHCP clients to optionally identify the vendor 1454 type and configuration of a DHCP client. The information is a string 1455 of n octets, interpreted by servers. Vendors may choose to define 1456 specific vendor class identifiers to convey particular configuration 1457 or other identification information about a client. For example, the 1458 identifier may encode the client's hardware configuration. Servers 1459 not equipped to interpret the class-specific information sent by a 1460 client MUST ignore it (although it may be reported). Servers that 1461 respond SHOULD only use option 43 to return the vendor-specific 1462 information to the client. 1464 The code for this option is 60, and its minimum length is 1. 1466 Code Len Vendor class Identifier 1467 +-----+-----+-----+-----+--- 1468 | 60 | n | i1 | i2 | ... 1469 +-----+-----+-----+-----+--- 1471 9.14. Client-identifier 1473 This option is used by DHCP clients to specify their unique 1474 identifier. DHCP servers use this value to index their database of 1475 address bindings. This value is expected to be unique for all 1476 clients in an administrative domain. 1478 Identifiers SHOULD be treated as opaque objects by DHCP servers. 1480 The client identifier MAY consist of type-value pairs similar to the 1481 'htype'/'chaddr' fields defined in [3]. For instance, it MAY consist 1482 of a hardware type and hardware address. In this case the type field 1483 SHOULD be one of the ARP hardware types defined in STD2 [22]. A 1484 hardware type of 0 (zero) should be used when the value field 1485 contains an identifier other than a hardware address (e.g. a fully 1486 qualified domain name). 1488 For correct identification of clients, each client's client- 1489 identifier MUST be unique among the client-identifiers used on the 1490 subnet to which the client is attached. Vendors and system 1491 administrators are responsible for choosing client-identifiers that 1492 meet this requirement for uniqueness. 1494 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1496 The code for this option is 61, and its minimum length is 2. 1498 Code Len Type Client-Identifier 1499 +-----+-----+-----+-----+-----+--- 1500 | 61 | n | t1 | i1 | i2 | ... 1501 +-----+-----+-----+-----+-----+--- 1503 10. Defining new extensions 1505 The author of a new DHCP option will follow these steps to obtain 1506 acceptance of the option as a part of the DHCP Internet Standard: 1508 1. The author devises the new option. 1509 2. The author requests a number for the new option from IANA by 1510 contacting: 1511 Internet Assigned Numbers Authority (IANA) 1512 USC/Information Sciences Institute 1513 4676 Admiralty Way 1514 Marina del Rey, California 90292-6695 1516 or by email as: iana@isi.edu 1518 3. The author documents the new option, using the newly obtained 1519 option number, as an Internet Draft. 1520 4. The author submits the Internet Draft for review through the IETF 1521 standards process as defined in "Internet Official Protocol 1522 Standards" (STD 1). The new option will be submitted for eventual 1523 acceptance as an Internet Standard. 1524 5. The new option progresses through the IETF standards process; the 1525 new option will be reviewed by the Dynamic Host Configuration 1526 Working Group (if that group still exists), or as an Internet 1527 Draft not submitted by an IETF working group. 1528 6. If the new option fails to gain acceptance as an Internet 1529 Standard, the assigned option number will be returned to IANA for 1530 reassignment. 1532 This procedure for defining new extensions will ensure that: 1534 * allocation of new option numbers is coordinated from a single 1535 authority, 1536 * new options are reviewed for technical correctness and 1537 appropriateness, and 1538 * documentation for new options is complete and published. 1540 11. Acknowledgements 1542 The author thanks the many (and too numerous to mention!) 1544 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1546 members of the DHC WG for their tireless and ongoing efforts in 1547 the development of DHCP and this document. 1549 The efforts of J Allard, Mike Carney, Dave Lapp, Fred Lien and 1550 John Mendonca in organizing DHCP interoperability testing 1551 sessions are gratefully acknowledged. 1553 The development of this document was supported in part by grants 1554 from the Corporation for National Research Initiatives (CNRI), 1555 Bucknell University and Sun Microsystems. 1557 12. References 1559 [1] Droms, R., "Dynamic Host Configuration Protocol", RFC 1531, 1560 Bucknell University, October 1993. 1562 [2] Reynolds, J., "BOOTP Vendor Information Extensions", RFC 1497, 1563 USC/Information Sciences Institute, August 1993. 1565 [3] Croft, W., and J. Gilmore, "Bootstrap Protocol", RFC 951, 1566 Stanford University and Sun Microsystems, September 1985. 1568 [4] Braden, R., Editor, "Requirements for Internet Hosts - 1569 Communication Layers", STD 3, RFC 1122, USC/Information Sciences 1570 Institute, October 1989. 1572 [5] Mogul, J., and J. Postel, "Internet Standard Subnetting 1573 Procedure", STD 5, RFC 950, USC/Information Sciences Institute, 1574 August 1985. 1576 [6] Postel, J., and K. Harrenstien, "Time Protocol", STD 26, RFC 1577 868, USC/Information Sciences Institute, SRI, May 1983. 1579 [7] Postel, J., "Name Server", IEN 116, USC/Information Sciences 1580 Institute, August 1979. 1582 [8] Mockapetris, P., "Domain Names - Implementation and 1583 Specification", STD 13, RFC 1035, USC/Information Sciences 1584 Institute, November 1987. 1586 [9] Postel, J., "Quote of the Day Protocol", STD 23, RFC 865, 1587 USC/Information Sciences Institute, May 1983. 1589 [10] McLaughlin, L., "Line Printer Daemon Protocol", RFC 1179, The 1590 Wollongong Group, August 1990. 1592 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1594 [11] Accetta, M., "Resource Location Protocol", RFC 887, CMU, 1595 December 1983. 1597 [12] Mogul, J. and S. Deering, "Path MTU Discovery", RFC 1191, 1598 DECWRL, Stanford University, November 1990. 1600 [13] Deering, S., "ICMP Router Discovery Messages", RFC 1256, 1601 Xerox PARC, September 1991. 1603 [14] Leffler, S. and M. Karels, "Trailer Encapsulations", RFC 893, 1604 U. C. Berkeley, April 1984. 1606 [15] Hornig, C., "Standard for the Transmission of IP Datagrams over 1607 Ethernet Networks", RFC 894, Symbolics, April 1984. 1609 [16] Postel, J. and J. Reynolds, "Standard for the Transmission of 1610 IP Datagrams Over IEEE 802 Networks", RFC 1042, USC/Information 1611 Sciences Institute, February 1988. 1613 [17] Sun Microsystems, "System and Network Administration", March 1614 1990. 1616 [18] Mills, D., "Internet Time Synchronization: The Network Time 1617 Protocol", RFC 1305, UDEL, March 1992. 1619 [19] NetBIOS Working Group, "Protocol Standard for a NetBIOS Service 1620 on a TCP/UDP transport: Concepts and Methods", STD 19, RFC 1001, 1621 March 1987. 1623 [20] NetBIOS Working Group, "Protocol Standard for a NetBIOS Service 1624 on a TCP/UDP transport: Detailed Specifications", STD 19, RFC 1625 1002, March 1987. 1627 [21] Scheifler, R., "FYI On the X Window System", FYI 6, RFC 1198, 1628 MIT Laboratory for Computer Science, January 1991. 1630 [22] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1700, 1631 USC/Information Sciences Institute, July 1992. 1633 13. Security Considerations 1635 Security issues are not discussed in this memo. 1637 14. Authors' Addresses 1639 Steve Alexander 1640 Silicon Graphics, Inc. 1641 2011 N. Shoreline Boulevard 1643 DRAFT DHCP Options and BOOTP Vendor Extensions November 1996 1645 Mailstop 510 1646 Mountain View, CA 94043-1389 1648 Phone: (415) 933-6172 1649 EMail: sca@engr.sgi.com 1651 Ralph Droms 1652 Bucknell University 1653 Lewisburg, PA 17837 1655 Phone: (717) 524-1145 1656 EMail: droms@bucknell.edu