Internet DRAFT - draft-droms-dhc-dhcpv6-rfc868-servers
draft-droms-dhc-dhcpv6-rfc868-servers
IPv6 Group R. Droms
Internet-Draft Cisco Systems, Inc.
Expires: March 5, 2006 D. Evans
ARRIS International, Inc.
September 2005
Time Protocol Servers and Time Offset Options for IPv6 DHCP
draft-droms-dhc-dhcpv6-rfc868-servers-02.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
The Time Protocol Servers option for IPv6 DHCP (RFC 3315) carries the
IPv6 addresses of servers that a host should use for the Time
Protocol (RFC 868). The Time Offset option carries the offset in
seconds from Coordinated Universal Time (UTC) that a client may use
to determine its local time.
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1. Introduction
The Time Protocol [1] can be used to obtain the current time from a
server. The Time Protocol Servers option defined in this document
provides an option to provide the IPv6 addresses of Time Protocol
servers to a host through DHCP [2].
The Time Offset option defined in this document provides an option to
provide an offset in seconds from UTC that a client can use to
determine its local time. This option is only meaningful if the
server has knowledge of the physical location of the client.
The options defined in this document are based on the IPv4 DHCP [3]
Time Server and Time Offset options [4]. This document has no effect
on IPv4 DHCP, which will continue to use the Time Server option to
provide the IPv4 addresses of RFC 868 Time Protocol servers and the
Time Offset option to provide the offset between UTC and local time
to clients.
2. Terminology
The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL in this document are to be
interpreted as described in RFC2119 [5].
Throughout this document, unless indicated otherwise for clarity, the
acronym "DHCP" refers to "Dynamic Host Configuration Protocol for
IPv6" [2].
3. Format of the Time Protocol Servers option
The Time Protocol Servers option defines a list of Time Protocol
servers available to the DHCP client. The IPv6 address of each
server is included in the option. The addresses SHOULD be listed in
order of preference. The addresses MUST be unicast or anycast
addresses.
The Time Protocol Servers option has the following format:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_RFC868_SERVER | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| server-address1 |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| server-address2 |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| server-addressN |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_RFC868_SERVERS (TBD).
option-len 16 * N.
server-address1-N The IPv6 addresses of the Time Protocol servers.
4. Time Offset option
The Time Offset option specifies the offset in seconds from
Coordinated Universal Time (UTC) that the client should use to
determine its local time. The offset is expressed as a two's
complement 32-bit integer. A positive offset indicates a location
east of the zero meridian and a negative offset indicates a location
west of the zero meridian. It is recommended that this option be
used only when the concept of local time based on a 24-hour day is
known to be meaningful.
The Time Offset option has the following format:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_TIME_OFFSET | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| time_offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_TIME_OFFSET (TBD).
option-len 4.
server-address1-N Offset in seconds from UTC.
5. Security Considerations
A server could use this option to return invalid or incorrect
addresses or valid addresses of malicious Time Protocol servers to
the client. A server could use this option to return incorrect or
inappropriate time offset values to the client.
Authentication of DHCP messages [2] can be used to ensure that the
contents of this option are not altered in transit between the DHCP
server and client.
6. IANA Considerations
IANA is requested to assign an option code from the IPv6 DHCP options
registry to OPTION_RFC868_SERVER and OPTION_TIME_OFFSET.
7. Normative References
[1] Postel, J. and K. Harrenstien, "Time Protocol", STD 26, RFC 868,
May 1983.
[2] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 3315, July 2003.
[3] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[4] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
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Authors' Addresses
Ralph Droms
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Phone: +1 978.936.1674
Email: rdroms@cisco.com
D. R. Evans
ARRIS International, Inc.
7912 Fairview Road
Boulder, CO 80303
USA
Phone: +1 303.494.0394
Email: N7DR@arrisi.com
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