rfc2132.txt

DHCP服务器源码

   as defined in this document.

   The client MAY list the options in order of preference.  The DHCP
   server is not required to return the options in the requested order,
   but MUST try to insert the requested options in the order requested
   by the client.

   The code for this option is 55.  Its minimum length is 1.

    Code   Len   Option Codes
   +-----+-----+-----+-----+---
   |  55 |  n  |  c1 |  c2 | ...
   +-----+-----+-----+-----+---

9.9. Message

   This option is used by a DHCP server to provide an error message to a
   DHCP client in a DHCPNAK message in the event of a failure. A client
   may use this option in a DHCPDECLINE message to indicate the why the
   client declined the offered parameters.  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 56 and its minimum length is 1.

    Code   Len     Text
   +-----+-----+-----+-----+---
   |  56 |  n  |  c1 |  c2 | ...
   +-----+-----+-----+-----+---

9.10. 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.  A client may use the maximum DHCP message size option in
   DHCPDISCOVER or DHCPREQUEST messages, but should not use the option
   in DHCPDECLINE messages.




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RFC 2132        DHCP Options and BOOTP Vendor Extensions      March 1997


   The code for this option is 57, and its length is 2.  The minimum
   legal value is 576 octets.

    Code   Len     Length
   +-----+-----+-----+-----+
   |  57 |  2  |  l1 |  l2 |
   +-----+-----+-----+-----+

9.11. Renewal (T1) Time Value

   This option specifies the time interval from address assignment until
   the client transitions to the RENEWING state.

   The value is in units of seconds, and is specified as a 32-bit
   unsigned integer.

   The code for this option is 58, and its length is 4.

    Code   Len         T1 Interval
   +-----+-----+-----+-----+-----+-----+
   |  58 |  4  |  t1 |  t2 |  t3 |  t4 |
   +-----+-----+-----+-----+-----+-----+

9.12. 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 59, and its length is 4.

    Code   Len         T2 Interval
   +-----+-----+-----+-----+-----+-----+
   |  59 |  4  |  t1 |  t2 |  t3 |  t4 |
   +-----+-----+-----+-----+-----+-----+

9.13. Vendor class identifier

   This option is used by DHCP clients to optionally identify the vendor
   type and configuration of a DHCP client.  The information is a string
   of n octets, interpreted by servers.  Vendors may choose to define
   specific vendor class identifiers to convey particular configuration
   or other identification information about a client.  For example, the
   identifier may encode the client's hardware configuration.  Servers
   not equipped to interpret the class-specific information sent by a
   client MUST ignore it (although it may be reported). Servers that



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   respond SHOULD only use option 43 to return the vendor-specific
   information to the client.

   The code for this option is 60, and its minimum length is 1.

   Code   Len   Vendor class Identifier
   +-----+-----+-----+-----+---
   |  60 |  n  |  i1 |  i2 | ...
   +-----+-----+-----+-----+---

9.14. Client-identifier

   This option is used by DHCP clients to specify their unique
   identifier.  DHCP servers use this value to index their database of
   address bindings.  This value is expected to be unique for all
   clients in an administrative domain.

   Identifiers SHOULD be treated as opaque objects by DHCP servers.

   The client identifier MAY consist of type-value pairs similar to the
   'htype'/'chaddr' fields defined in [3]. For instance, it MAY consist
   of a hardware type and hardware address. In this case the type field
   SHOULD be one of the ARP hardware types defined in STD2 [22].  A
   hardware type of 0 (zero) should be used when the value field
   contains an identifier other than a hardware address (e.g. a fully
   qualified domain name).

   For correct identification of clients, each client's client-
   identifier MUST be unique among the client-identifiers used on the
   subnet to which the client is attached.  Vendors and system
   administrators are responsible for choosing client-identifiers that
   meet this requirement for uniqueness.

   The code for this option is 61, and its minimum length is 2.

   Code   Len   Type  Client-Identifier
   +-----+-----+-----+-----+-----+---
   |  61 |  n  |  t1 |  i1 |  i2 | ...
   +-----+-----+-----+-----+-----+---












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10. Defining new extensions

   The author of a new DHCP option will follow these steps to obtain
   acceptance of the option as a part of the DHCP Internet Standard:

   1. The author devises the new option.
   2. The author requests a number for the new option from IANA by
      contacting:
      Internet Assigned Numbers Authority (IANA)
      USC/Information Sciences Institute
      4676 Admiralty Way
      Marina del Rey, California  90292-6695

      or by email as: [e-mail]

   3. The author documents the new option, using the newly obtained
      option number, as an Internet Draft.
   4. The author submits the Internet Draft for review through the IETF
      standards process as defined in "Internet Official Protocol
      Standards" (STD 1).  The new option will be submitted for eventual
      acceptance as an Internet Standard.
   5. The new option progresses through the IETF standards process; the
      new option will be reviewed by the Dynamic Host Configuration
      Working Group (if that group still exists), or as an Internet
      Draft not submitted by an IETF working group.
   6. If the new option fails to gain acceptance as an Internet
      Standard, the assigned option number will be returned to IANA for
      reassignment.

      This procedure for defining new extensions will ensure that:

      * allocation of new option numbers is coordinated from a single
        authority,
      * new options are reviewed for technical correctness and
        appropriateness, and
      * documentation for new options is complete and published.

11. Acknowledgements

   The author thanks the many (and too numerous to mention!) members of
   the DHC WG for their tireless and ongoing efforts in the development
   of DHCP and this document.

   The efforts of J Allard, Mike Carney, Dave Lapp, Fred Lien and John
   Mendonca in organizing DHCP interoperability testing sessions are
   gratefully acknowledged.





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RFC 2132        DHCP Options and BOOTP Vendor Extensions      March 1997


   The development of this document was supported in part by grants from
   the Corporation for National Research Initiatives (CNRI), Bucknell
   University and Sun Microsystems.

12. References

   [1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
       Bucknell University, March 1997.

   [2] Reynolds, J., "BOOTP Vendor Information Extensions", RFC 1497,
       USC/Information Sciences Institute, August 1993.

   [3] Croft, W., and J. Gilmore, "Bootstrap Protocol", RFC 951,
       Stanford University and Sun Microsystems, September 1985.

   [4] Braden, R., Editor, "Requirements for Internet Hosts -
       Communication Layers", STD 3, RFC 1122, USC/Information Sciences
       Institute, October 1989.

   [5] Mogul, J., and J. Postel, "Internet Standard Subnetting
       Procedure", STD 5, RFC 950, USC/Information Sciences Institute,
       August 1985.

   [6] Postel, J., and K. Harrenstien, "Time Protocol", STD 26, RFC
       868, USC/Information Sciences Institute, SRI, May 1983.

   [7] Postel, J., "Name Server", IEN 116, USC/Information Sciences
       Institute, August 1979.

   [8] Mockapetris, P., "Domain Names - Implementation and
       Specification", STD 13, RFC 1035, USC/Information Sciences
       Institute, November 1987.

   [9] Postel, J., "Quote of the Day Protocol", STD 23, RFC 865,
       USC/Information Sciences Institute, May 1983.

   [10] McLaughlin, L., "Line Printer Daemon Protocol", RFC 1179, The
        Wollongong Group, August 1990.

   [11] Accetta, M., "Resource Location Protocol", RFC 887, CMU,
        December 1983.

   [12] Mogul, J. and S. Deering, "Path MTU Discovery", RFC 1191,
        DECWRL,  Stanford University, November 1990.

   [13] Deering, S., "ICMP Router Discovery Messages", RFC 1256,
        Xerox PARC, September 1991.




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RFC 2132        DHCP Options and BOOTP Vendor Extensions      March 1997


   [14] Leffler, S. and M. Karels, "Trailer Encapsulations", RFC 893,
        U. C. Berkeley, April 1984.

   [15] Hornig, C., "Standard for the Transmission of IP Datagrams over
        Ethernet Networks", RFC 894, Symbolics, April 1984.

   [16] Postel, J. and J. Reynolds, "Standard for the Transmission of
        IP Datagrams Over IEEE 802 Networks", RFC 1042,  USC/Information
        Sciences Institute, February 1988.

   [17] Sun Microsystems, "System and Network Administration", March
        1990.

   [18] Mills, D., "Internet Time Synchronization: The Network Time
        Protocol", RFC 1305, UDEL, March 1992.

   [19] NetBIOS Working Group, "Protocol Standard for a NetBIOS Service
        on a TCP/UDP transport: Concepts and Methods", STD 19, RFC 1001,
        March 1987.

   [20] NetBIOS Working Group, "Protocol Standard for a NetBIOS Service
        on a TCP/UDP transport: Detailed Specifications", STD 19, RFC
        1002, March 1987.

   [21] Scheifler, R., "FYI On the X Window System", FYI 6, RFC 1198,
        MIT Laboratory for Computer Science, January 1991.

   [22] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
        USC/Information Sciences Institute, July 1992.

13. Security Considerations

   Security issues are not discussed in this memo.


















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14. Authors' Addresses

   Steve Alexander
   Silicon Graphics, Inc.
   2011 N. Shoreline Boulevard
   Mailstop 510
   Mountain View, CA 94043-1389

   Phone: [phone]
   EMail: [e-mail]


   Ralph Droms
   Bucknell University
   Lewisburg, PA 17837

   Phone: [phone]
   EMail: [e-mail]

































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