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Network Working Group Internet Engineering Task Force Internet-Draft S. Alexander Lachman Technology, Inc. R. Droms Bucknell University January 1993 DHCP Options and BOOTP Vendor Extensions Status of this Memo This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress." Please check the 1id-abstracts.txt listing contained in the internet-drafts Shadow Directories on nic.ddn.mil, nnsc.nsf.net, nic.nordu.net, ftp.nisc.sri.com, or munnari.oz.au to learn the current status of any Internet Draft. Distribution of this memo is unlimited. Abstract The Dynamic Host Configuration Protocol (DHCP) [1] provides a framework for passing configuration information to hosts on a TCP/IP network. Configuration parameters and other control information are carried in tagged data items that are stored in the "options" field of the DHCP message. The data items themselves are also called "options." This document specifies the current set of DHCP options. This document will be periodically updated as new options are defined. Each superseding document will include the entire current list of valid options. Table of Contents 1. DHCP Option Fields ........................................ 2 S. Alexander, R. Droms Expires July 1993 [Page 1] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 2. RFC 1084 Vendor Extensions ................................ 2 3. IP Layer Parameters per Host .............................. 7 4. IP Layer Parameters per Interface ......................... 9 5. Link Layer Parameters per Interface ....................... 11 6. TCP Parameters ............................................ 12 7. DHCP Extensions ........................................... 13 8. Security Considerations ................................... 18 9. References ................................................ 18 10. Authors' Addresses ........................................ 19 1. DHCP Option Fields DHCP options have the same format as the BOOTP "vendor extensions" defined in RFC 1084 [2]. Options may be fixed length or variable length. All options begin with a tag octet, which uniquely identifies the option. Fixed length options without data consist of only a tag octet. For fixed length options with data, the data immediately follows the tag octet. For variable length options, a length octet follows the tag octet. The length octet is followed by length octets of data. All multi-octet quantities are in network byte-order. All of the "vendor extensions" defined in RFC 1084 are also DHCP options. Option codes 128 to 254 (decimal) are reserved for site-specific options. Except for the options in section 7, all options may be used with either DHCP or BOOTP. Many of these options have their default values specified in other documents. In particular, RFC 1122 [3] specifies default values for most IP and TCP configuration parameters. 2. RFC 1084 Vendor Extensions This section lists the vendor extensions as defined in RFC 1084. They are defined here for completeness. 2.1. Pad Option The pad option can be used to cause subsequent fields to align on word boundaries. The code for the pad option is 0, and its length is 1 octet. S. Alexander, R. Droms Expires July 1993 [Page 2] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 Code +-----+ | 0 | +-----+ 2.2. End Option The end option marks the end of valid information in the vendor field. Subsequent octets should be filled with pad options. The code for the end option is 255, and its length is 1 octet. Code +-----+ | 255 | +-----+ 2.3. Subnet Mask The subnet mask option specifies the local subnet mask as per RFC 950 [4]. The code for the subnet mask option is 1, and its length is 4 octets. If both the subnet mask and the router option are specified in a DHCP reply, the subnet mask option MUST be first. Code Len Subnet Mask +-----+-----+-----+-----+-----+-----+ | 1 | 4 | m1 | m2 | m3 | m4 | +-----+-----+-----+-----+-----+-----+ 2.4. Time Offset The time offset field specifies the offset of the local subnet in seconds from Coordinated Universal Time (UTC). The offset is expressed as a signed 32-bit integer. The code for the time offset option is 2, and its length is 4 octets. Code Len Time Offset +-----+-----+-----+-----+-----+-----+ | 2 | 4 | n1 | n2 | n3 | n4 | +-----+-----+-----+-----+-----+-----+ 2.5. Router Option The router option specifies a list of IP addresses for routers on the local subnet. Routers SHOULD be listed in order of preference. The code for the router option is 3. The minimum length for the router option is 4 octets, and the length MUST always be a multiple of 4. S. Alexander, R. Droms Expires July 1993 [Page 3] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 3 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.6. Time Server Option The time server option specifies a list of RFC 868 [5] time servers on the local subnet. Servers SHOULD be listed in order of preference. The code for the time server option is 4. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 4 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.7. Name Server Option The name server option specifies a list of IEN 116 [6] name servers on the local subnet. Servers SHOULD be listed in order of preference. The code for the name server option is 5. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 5 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.8. Domain Name Server Option The domain name server option specifies a list of Domain Name System (RFC 1035 [7]) name servers on the local subnet. Servers SHOULD be listed in order of preference. The code for the domain name server option is 6. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 6 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.9. Log Server Option The log server option specifies a list of MIT-LCS UDP log servers on the local subnet. Servers SHOULD be listed in order of preference. The code for the log server option is 7. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4. S. Alexander, R. Droms Expires July 1993 [Page 4] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 7 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.10. Cookie Server Option The cookie server option specifies a list of RFC 865 [8] cookie servers on the local subnet. Servers SHOULD be listed in order of preference. The code for the log server option is 8. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 8 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.11. LPR Server Option The LPR server option specifies a list of RFC 1179 [9] line printer servers on the local subnet. Servers SHOULD be listed in order of preference. The code for the LPR server option is 9. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 9 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.12. Impress Server Option The Impress server option specifies a list of Imagen Impress servers on the local subnet. Servers SHOULD be listed in order of preference. The code for the Impress server option is 10. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 10 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.13. Resource Location Server Option This option specifies a list of RFC 887 [10] Resource Location servers on the local subnet. Servers SHOULD be listed in order of preference. The code for this option is 11. The minimum length for this option is 4 octets, and the length MUST always be a multiple of S. Alexander, R. Droms Expires July 1993 [Page 5] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 4. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 11 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.14. Host Name Option This option specifies the name of the DHCP client. The name may or may not be qualified with the local domain name. See RFC 1035 for character set restrictions. The code for this option is 12, and its minimum length is 1. Code Len Host Name +-----+-----+-----+-----+-----+-----+-----+-----+-- | 12 | n | h1 | h2 | h3 | h4 | h5 | h6 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.15. Boot File Size Option This option specifies the length in 512-octet blocks of the default boot image for the DHCP client. The file length is specified as an unsigned 16-bit integer. The code for this option is 13, and its length is 2. Code Len File Size +-----+-----+-----+-----+ | 13 | 2 | l1 | l2 | +-----+-----+-----+-----+ 2.16. Network Information Service Domain Option This option specifies the name of the client's NIS [11] domain. The domain is formatted as a character string consisting of characters from the NVT ASCII character set. The code for this option is 14. Its minimum length is 1. Code Len NIS Domain Name +-----+-----+-----+-----+-----+-----+--- | 14 | n | n1 | n2 | n3 | n4 | ... +-----+-----+-----+-----+-----+-----+--- 2.17. Network Information Servers Option This option specifies a list of IP addresses indicating NIS servers on the local subnet. Servers SHOULD be listed in order of preference. The code for this option is 15. Its minimum length is 4, and the S. Alexander, R. Droms Expires July 1993 [Page 6] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 length MUST be a multiple of 4.. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 15 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 2.18. Network Time Protocol Servers Option This option specifies a list of IP addresses indicating NTP [12] servers on the local subnet. Servers SHOULD be listed in order of preference. The code for this option is 16. Its minimum length is 4, and the length MUST be a multiple of 4. Code Len Address 1 Address 2 +-----+-----+-----+-----+-----+-----+-----+-----+-- | 16 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- 3. IP Layer Parameters per Host This section details the options that affect the operation of the IP layer on a per-host basis. 3.1. IP Forwarding Enable/Disable Option This option specifies whether the DHCP client should configure its IP layer for packet forwarding. A value of 0 means disable IP forwarding, and a value of 1 means enable IP forwarding. The code for this option is 17, and its length is 1. Code Len Value +-----+-----+-----+ | 17 | 1 | 0/1 | +-----+-----+-----+ 3.2. Non-Local Source Routing Enable/Disable Option This option specifies whether the DHCP client should configure its IP layer to allow forwarding of datagrams with non-local source routes. A value of 0 means disallow forwarding of such datagrams, and a value of 1 means allow forwarding. The code for this option is 18, and its length is 1. Code Len Value +-----+-----+-----+ | 18 | 1 | 0/1 | +-----+-----+-----+ 3.3. Policy Filter Option S. Alexander, R. Droms Expires July 1993 [Page 7] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 This option specifies policy filters for non-local source routing. The filters consist of a list of IP addresses and masks which specify destination/mask pairs with which to filter incoming source routes. See RFC 1009 [13] for details. The code for this option is 19. The minimum length of this option is 8, and the length MUST be a multiple of 8. Code Len Address 1 Mask 1 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | 19 | n | a1 | a2 | a3 | a4 | m1 | m2 | m3 | m4 | +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ Address 2 Mask 2 +-----+-----+-----+-----+-----+-----+-----+-----+--- | a1 | a2 | a3 | a4 | m1 | m2 | m3 | m4 | ... +-----+-----+-----+-----+-----+-----+-----+-----+--- 3.4. Maximum Datagram Reassembly Size This option specifies the maximum size datagram that the client should be prepared to reassemble. The size is specified as a 16-bit unsigned integer. The minimum value legal value is 576. The code for this option is 20, and its length is 2. Code Len Size +-----+-----+-----+-----+ | 20 | 2 | s1 | s2 | +-----+-----+-----+-----+ 3.5. Default IP Time-to-live This option specifies the default time-to-live that the client should use on outgoing datagrams. The TTL is specified as an octet with a value between 1 and 255. The code for this option is 21, and its length is 1. Code Len TTL +-----+-----+-----+ | 21 | 1 | ttl | +-----+-----+-----+ 3.6. Path MTU Aging Timeout Option This option specifies the timeout (in seconds) to use when aging Path MTU values discovered by the mechanism defined in RFC 1191 [14]. The timeout is specified as a 32-bit unsigned integer. The code for this option is 22, and its length is 4. S. Alexander, R. Droms Expires July 1993 [Page 8] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 Code Len Timeout +-----+-----+-----+-----+-----+-----+ | 22 | 4 | t1 | t2 | t3 | t4 | +-----+-----+-----+-----+-----+-----+ 3.7. Path MTU Plateau Table Option This option specifies a table of MTU sizes to use when performing Path MTU Discovery as defined in RFC 1191. The table is formatted as a list of 16-bit unsigned integers, ordered from smallest to largest. The minimum MTU value cannot be smaller than 68. The code for this option is 23. Its minimum length is 2, and the length MUST be a multiple of 2. Code Len Size 1 Size 2 +-----+-----+-----+-----+-----+-----+--- | 23 | n | s1 | s2 | s1 | s2 | ... +-----+-----+-----+-----+-----+-----+--- 4. IP Layer Parameters per Interface This section details the options that affect the operation of the IP layer on a per-interface basis. It is expected that a DHCP client can issue multiple requests, one per interface, in order to configure interfaces with their specific parameters. 4.1. Interface MTU Option This option specifies the MTU to use on this interface. The MTU is specified as a 16-bit unsigned integer. The minimum legal value for the MTU is 68. The code for this option is 24, and its length is 2. Code Len MTU +-----+-----+-----+-----+ | 24 | 2 | m1 | m2 | +-----+-----+-----+-----+ 4.2. All Subnets are Local Option This option specifies whether or not the client can treat all subnets as having the local MTU. A value of 0 indicates that the client should not treat subnets as being local for purposes of MTU computation. A value of 1 means that the client may treat all subnets as being local. The code for this option is 25, and its length is 1. S. Alexander, R. Droms Expires July 1993 [Page 9] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 Code Len Value +-----+-----+-----+ | 25 | 1 | 0/1 | +-----+-----+-----+ 4.3. Broadcast Address Option This option specifies whether or not the host portion of the broadcast address for this interface should be all ones or all zeroes. A value of 0 indicates that the client should use zeroes (e.g. 128.212.0.0). A value of 1 means that the client should use ones (e.g. 128.212.255.255). The code for this option is 26, and its length is 1. Code Len Value +-----+-----+-----+ | 26 | 1 | 0/1 | +-----+-----+-----+ 4.4. Perform Mask Discovery Option This option specifies whether or not the client should perform subnet mask discovery using ICMP. A value of 0 indicates that the client should not perform mask discovery. A value of 1 means that the client should perform mask discovery. The code for this option is 27, and its length is 1. Code Len Value +-----+-----+-----+ | 27 | 1 | 0/1 | +-----+-----+-----+ 4.5. Mask Supplier Option This option specifies whether or not the client should respond to subnet mask requests using ICMP. A value of 0 indicates that the client should not respond. A value of 1 means that the client should respond. The code for this option is 28, and its length is 1. Code Len Value +-----+-----+-----+ | 28 | 1 | 0/1 | +-----+-----+-----+ 4.6. Perform Router Discovery Option This option specifies whether or not the client should solicit routers using the Router Discovery mechanism defined in RFC 1256 [15]. A value of 0 indicates that the client should not perform S. Alexander, R. Droms Expires July 1993 [Page 10] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 router discovery. A value of 1 means that the client should perform router discovery. The code for this option is 29, and its length is 1. Code Len Value +-----+-----+-----+ | 29 | 1 | 0/1 | +-----+-----+-----+ 4.7. Router Solicitation Address Option This option specifies the address to which the client should transmit router solicitation requests. The code for this option is 30, and its length is 4. Code Len Address +-----+-----+-----+-----+-----+-----+ | 30 | 4 | a1 | a2 | a3 | a4 | +-----+-----+-----+-----+-----+-----+ 4.8. Static Route Option This option specifies a list of static routes that the client should install in its routing cache. If multiple routes to the same destination are specified, they are listed in descending order of priority. The routes consist of a list of IP address pairs. The first address is the destination address, and the second address is the router for the destination. The code for this option is 31. The minimum length of this option is 8, and the length MUST be a multiple of 8. Code Len Destination 1 Router 1 +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | 31 | n | d1 | d2 | d3 | d4 | r1 | r2 | r3 | r4 | +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ Destination 2 Router 2 +-----+-----+-----+-----+-----+-----+-----+-----+--- | d1 | d2 | d3 | d4 | r1 | r2 | r3 | r4 | ... +-----+-----+-----+-----+-----+-----+-----+-----+--- 5. Link Layer Parameters per Interface This section lists the options that affect the operation of the data link layer on a per-interface basis. 5.1. Trailer Encapsulation Option S. Alexander, R. Droms Expires July 1993 [Page 11] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 This option specifies whether or not the client should negotiate the use of trailers [16] when using the ARP protocol. A value of 0 indicates that the client should not attempt to use trailers. A value of 1 means that the client should attempt to use trailers. The code for this option is 32, and its length is 1. Code Len Value +-----+-----+-----+ | 32 | 1 | 0/1 | +-----+-----+-----+ 5.2. ARP Cache Timeout Option This option specifies the timeout in seconds for ARP cache entries. The time is specified as a 32-bit unsigned integer. The code for this option is 33, and its length is 4. Code Len Time +-----+-----+-----+-----+-----+-----+ | 33 | 4 | t1 | t2 | t3 | t4 | +-----+-----+-----+-----+-----+-----+ 5.3. Ethernet Encapsulation Option This option specifies whether or not the client should use Ethernet Version 2 (RFC 894 [17]) or IEEE 802.3 (RFC 1042 [18]) encapsulation if the interface is an Ethernet. A value of 0 indicates that the client should use RFC 894 encapsulation. A value of 1 means that the client should use RFC 1042 encapsulation. The code for this option is 34, and its length is 1. Code Len Value +-----+-----+-----+ | 34 | 1 | 0/1 | +-----+-----+-----+ 6. TCP Parameters This section lists the options that affect the operation of the TCP layer on a per-interface basis. 6.1. TCP Default TTL Option This option specifies the default TTL that the client should use when sending TCP segments. The value is represented as an 8-bit unsigned integer. The minimum value is 1. The code for this option is 35, and its length is 1. S. Alexander, R. Droms Expires July 1993 [Page 12] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 Code Len TTL +-----+-----+-----+ | 35 | 1 | n | +-----+-----+-----+ 6.2. TCP Keepalive Interval Option This option specifies the interval (in seconds) that the client TCP should wait before sending a keepalive message on a TCP connection. The time is specified as a 32-bit unsigned integer. A value of zero indicates that the client should not generate keepalive messages on connections unless specifically requested by an application. The code for this option is 36, and its length is 4. Code Len Time +-----+-----+-----+-----+-----+-----+ | 36 | 4 | t1 | t2 | t3 | t4 | +-----+-----+-----+-----+-----+-----+ 6.3. TCP Keepalive Garbage Option This option specifies the whether or not the client should send TCP keepalive messages with a octet of garbage for compatibility with older implementations. A value of 0 indicates that a garbage octet should not be sent. A value of 1 indicates that a garbage octet should be sent. The code for this option is 37, and its length is 1. Code Len Value +-----+-----+-----+ | 37 | 1 | 0/1 | +-----+-----+-----+ 7. DHCP Extensions This section details the options that are specific to DHCP. 7.1. Requested IP Address This option is used in a client request (DHCPDISCOVER) to allow the client to request that a particular IP address be assigned. In a server reply (DHCPOFFER), this option indicates the IP address that the server is willing to offer. The code for this option is 38, and its length is 4. Code Len Address +-----+-----+-----+-----+-----+-----+ | 38 | 4 | a1 | a2 | a3 | a4 | +-----+-----+-----+-----+-----+-----+ S. Alexander, R. Droms Expires July 1993 [Page 13] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 7.2. IP Address Lease Time This option is used in a client request (DHCPDISCOVER or DHCPREQUEST) to allow the client to request a lease time for the IP address. In a server reply (DHCPOFFER), a DHCP server uses this option to specify the lease time it is willing to offer. The time is in units of seconds, and is specified as a 32-bit unsigned integer. The code for this option is 39, and its length is 4. Code Len Lease Time +-----+-----+-----+-----+-----+-----+ | 39 | 4 | t1 | t2 | t3 | t4 | +-----+-----+-----+-----+-----+-----+ 7.3. Option Overload This option is used to indicate that the DHCP "sname" or "file" fields are being overloaded by using them to carry DHCP options. A DHCP server inserts this option if the returned parameters will exceed the usual space allotted for options. If this option is present, the DHCP client interprets the specified additional fields after it concludes interpretation of the standard option fields. The code for this option is 40, and its length is 1. Legal values for this option are: Value Meaning ----- -------- 1 use the "file" field to hold options 2 use the "sname" field to hold options 3 use both fields to hold options Code Len Value +-----+-----+-----+ | 40 | 1 |1/2/3| +-----+-----+-----+ 7.4. DHCP Message Type This option is used to convey the type of the DHCP message. The code for this option is 41, and its length is 1. Legal values for this option are: S. Alexander, R. Droms Expires July 1993 [Page 14] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 Value Message Type ----- ------------ 1 DHCPDISCOVER 2 DHCPOFFER 3 DHCPREQUEST 4 DHCPDECLINE 5 DHCPACK 6 DHCPNAK 7 DHCPRELEASE Code Len Type +-----+-----+-----+ | 41 | 1 | 1-7 | +-----+-----+-----+ 7.5. Lease Identifier Cookie This option is used by a DHCP server to indicate the unique identifier for an address lease. The cookie is an opaque object of n octets. The cookie is used by the client to identify the lease in future protocol transactions. The code for this option is 42. Code Len Cookie Data +-----+-----+-----+-----+--- | 42 | n | c1 | c2 | ... +-----+-----+-----+-----+--- 7.6. Server Identifier This option is used by a DHCP client to indicate which of several lease offers it is accepting. The identifier is the IP address of the selected server. The code for this option is 43, and its length is 4. Code Len Address +-----+-----+-----+-----+-----+-----+ | 43 | 4 | a1 | a2 | a3 | a4 | +-----+-----+-----+-----+-----+-----+ 7.7. Parameter Request Vector This option is used by a DHCP client to request values for specified configuration parameters. The options are specified as a 32-octet bit vector, where each bit that is set indicates the the client is requesting a parameter for that option. The order of bits in the vector is big-endian within octets. This means that the bit for parameter code 0 is the left-most bit of the first octet. The code for this option is 44, and its length is 32. S. Alexander, R. Droms Expires July 1993 [Page 15] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 Code Len Bit Vector +-----+-----+-----+-----+--- | 44 | 32 | c1 | c2 | ... 30 more octets ... +-----+-----+-----+-----+--- 7.8. Parameter Request List This option is used by a DHCP client to request values for specified configuration parameters. The list of requested parameters is specified as n octets, where each octet is a valid DHCP option code as defined in this document. The client may order the option codes as it desires. The DHCP server is not required to return the options in the requested order. The code for this option is 45. Code Len Option Codes +-----+-----+-----+-----+--- | 45 | n | c1 | c2 | ... +-----+-----+-----+-----+--- 7.9. Message This option is used by a DHCP server to provide an error message to a DHCP client in the event of a failure. The message consists of n octets of NVT ASCII text, which the client may display on an available output device. The code for this option is 46. Code Len Text +-----+-----+-----+-----+--- | 46 | n | c1 | c2 | ... +-----+-----+-----+-----+--- 7.10. Maximum DHCP Message Size This option specifies the maximum length DHCP message that it is willing to accept. The length is specified as an unsigned 16-bit integer. The code for this option is 47, and its length is 2. The minimum legal value is 267 octets (264 octets for the DHCP header + 3 octets for the DHCP message type). Code Len Length +-----+-----+-----+-----+ | 47 | 2 | l1 | l2 | +-----+-----+-----+-----+ 7.11. Renewal (T1) Time Value This option specifies the time interval from address assignment until the client transitions to the RENEWING state. S. Alexander, R. Droms Expires July 1993 [Page 16] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 The value is in units of seconds, and is specified as a 32-bit unsigned integer. The code for this option is 48, and its length is 4. Code Len T1 Interval +-----+-----+-----+-----+-----+-----+ | 48 | 4 | t1 | t2 | t3 | t4 | +-----+-----+-----+-----+-----+-----+ 7.12. Rebinding (T2) Time Value This option specifies the time interval from address assignment until the client transitions to the REBINDING state. The value is in units of seconds, and is specified as a 32-bit unsigned integer. The code for this option is 49, and its length is 4. Code Len T2 Interval +-----+-----+-----+-----+-----+-----+ | 49 | 4 | t1 | t2 | t3 | t4 | +-----+-----+-----+-----+-----+-----+ 7.13. Client-type This option is used by DHCP clients to optionally identify the type and configuration of a DHCP client. The information is a string of n octets, interpreted by servers. The definition of this information is vendor specific. Servers not equipped to interpret the vendor- specific information sent by a client MUST ignore it (although it may be reported). The code for this option is 50. Code Len Client-type +-----+-----+-----+-----+--- | 50 | n | i1 | i2 | ... +-----+-----+-----+-----+--- 7.14. Vendor Specific Information This option is used by DHCP clients and servers to exchange vendor- specific information. The information is an opaque object of n octets, presumably interpreted by vendor-specific code on the clients and servers. The definition of this information is vendor specific. The vendor is indicated in the client-type option. Servers not equipped to interpret the vendor-specific information sent by a client MUST ignore it (although it may be reported). Clients which do not receive desired vendor-specific information SHOULD make an attempt to operate without it, although they may do so (and announce they are doing so) in a degraded mode. S. Alexander, R. Droms Expires July 1993 [Page 17] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 The code for this option is 64. Code Len Vendor-specific information +-----+-----+-----+-----+--- | 64 | n | i1 | i2 | ... +-----+-----+-----+-----+--- 8. Security Considerations Security considerations are not addressed in this memo. 9. References [1] Droms, R., "Dynamic Host Configuration Protocol", Internet Draft, January 1993. [2] Reynolds, J.K., "BOOTP Vendor Information Extensions", RFC 1084, December 1988. [3] Braden, R.T., "Requirements for Internet Hosts - Communication Layers", RFC 1122, October 1989. [4] Mogul, J., "Internet Standard Subnetting Procedure", RFC 950, August 1985. [5] Postel, J.B., and K. Harrenstien, "Time Protocol", RFC 868, May 1983. [6] Postel, J.B., "Name Server", IEN 116, August 1979. [7] Mockapetris, P.V., "Domain Names - Implementation and Specification", RFC 1035, November 1987. [8] Postel, J.B., "Quote of the Day Protocol", RFC 865, May 1983. [9] McLaughlin, L., "Line Printer Daemon Protocol", RFC 1179, August 1990. [10] Accetta, M., "Resource Location Protocol", RFC 887, December 1983. [11] Sun Microsystems, "System and Network Administration", March 1990. [12] Mills, D.L., "Internet Time Synchronization: The Network Time Protocol", RFC 1129, October 1989. [13] Braden, R.T. and J.B. Postel, "Requirements for Internet Gateways", RFC 1009, June 1987. [14] Mogul, J. and S. Deering, "Path MTU Discovery", RFC 1191, S. Alexander, R. Droms Expires July 1993 [Page 18] Internet-Draft DHCP Options and BOOTP Vendor Extensions January 1993 November 1990. [15] Deering, S.E., "ICMP Router Discovery Messages", RFC 1256, September 1991. [16] Leffler, S. and M.J. Karels, "Trailer Encapsulations", RFC 893, April 1984. [17] Hornig, C, "Standard for the Transmission of IP Datagrams over Ethernet Networks", RFC 894, April 1984. [18] Postel, J.B. and J.K. Reynolds, "Standard for the Transmission of IP Datagrams Over IEEE 802 Networks", RFC 1042, February 1988. 10. Authors' Addresses Steve Alexander Lachman Technology, Inc. 1901 North Naper Boulevard Naperville, IL 60563-8895 Phone: (708) 505-9555 x256 EMail: stevea@isc.com Ralph Droms Computer Science Department 323 Dana Engineering Bucknell University Lewisburg, PA 17837 Phone: (717) 524-1145 EMail: droms@bucknell.edu S. Alexander, R. Droms Expires July 1993 [Page 19]