draft-ietf-dhc-dhcpv6-opt-timeconfig-01.txt   draft-ietf-dhc-dhcpv6-opt-timeconfig-02.txt 
Network Working Group A.K. Vijayabhaskar Network Working Group A.K. Vijayabhaskar
Internet-Draft Hewlett-Packard Internet-Draft Hewlett-Packard
Expires: November 10, 2002 10 May 2002 Expires: August 26, 2003 26 Feb 2003
Time Configuration Options for DHCPv6 Time Configuration Options for DHCPv6
draft-ietf-dhc-dhcpv6-opt-timeconfig-01.txt draft-ietf-dhc-dhcpv6-opt-timeconfig-02.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This document describes the options for Time related configuration This document describes the options for Time related configuration
information in DHCPv6: NTP Servers and IEEE 1003.1 POSIX Timezone information in DHCPv6: NTP Servers and Timezone specifier.
specifier.
1. Introduction 1. Introduction
This document describes the options for time related configuration This document describes the options for time related configuration
information in DHCPv6 [4]. information in DHCPv6 [1].
2. Requirements 2. Requirements
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in RFC 2119 [1] document, are to be interpreted as described in RFC 2119 [4]
3. Terminology 3. Terminology
This document uses terminology specific to IPv6 and DHCPv6 as defined This document uses terminology specific to IPv6 and DHCPv6 as defined
in section "Terminology" of the DHCP specification. in section "Terminology" of the DHCP specification.
4. Network Time Protocol (NTP) Servers option 4. Network Time Protocol (NTP) Servers option
The Network Time Protocol Servers option provides a list of one or The Network Time Protocol Servers option provides a list of one or
more IP addresses of NTP [2] servers available to the client. The more IP addresses of NTP [2] servers available to the client. The
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| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: OPTION_NTP_SERVERS (tbd) option-code: OPTION_NTP_SERVERS (tbd)
option-len: Length of the 'NTP server' fields in octets; It must be option-len: Length of the 'NTP server' fields in octets; It must be
a multiple of 16 a multiple of 16
NTP server: IP address of NTP server NTP server: IP address of NTP server
5. IEEE 1003.1 POSIX Timezone option 5. Timezone option
The IEEE 1003.1 POSIX Timezone option is used by the server to The Timezone option is used by the server to convey client's timezone
convey client's timezone information to the client. information to the client.
The format of the IEEE 1003.1 POSIX Timezone option is: The format of the Timezone option is:
0 1 2 3 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 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_ZONE | option-len | | OPTION_TIME_ZONE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| time-zone | | time-zone |
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: OPTION_TIME_ZONE (tbd) option-code: OPTION_TIME_ZONE (tbd)
option-len: Length of the 'time-zone' field in octets option-len: Length of the 'time-zone' field in octets
time-zone: Time zone of the client in IEEE 1003.1 POSIX Timezone time-zone: Time zone of the client in the format as explained below.
format [3].
The format of the IEEE 1003.1 POSIX timezone string is specified as
follows:
StdOffset[Dst[Offset],[Start[/Time],End[/Time]]] Std[Offset[Dst[Offset],[Start[/Time],End[/Time]]]]
where '[' and ']' enclose optional fields, '|' indicates choice where '[' and ']' enclose optional fields, '|' indicates choice
of exactly one of the alternatives, ',' and '/' represent literal of exactly one of the alternatives, ',' and '/' represent literal
characters present in the string. characters present in the string.
If "Offset" is specified, then the time-zone is represented in the
IEEE 1003.1 POSIX timezone format [3].
Std Three or more octets for the standard timezone (Std). Std Three or more octets for the standard timezone (Std).
Any character (or case) except a leading colon, digits, Any character (or case) except a leading colon, digits,
comma, minus or plus sign is allowed. comma, minus or plus sign is allowed. If the time-zone
is not represented in IEEE 1003.1 POSIX timezone format [3],
then Std is treated as the index to the timezone database,
for example, a file name, from where additional information
about the timezone may be obtained.
Offset Indicates the value one must add to local time to Offset Indicates the value one must add to local time to
arrive at UTC, of the form: [+|-]hh[:mm[:ss]]. Offset arrive at UTC, of the form: [+|-]hh[:mm[:ss]]. Offset
following Std is required. Digits are always interpreted following Std is required, if the timezone is represented
as decimal number. If preceded by a '-', the timezone is in IEEE 1003.1 POSIX timezone format. Digits are always
east of the Prime Meridian, otherwise it is west ('+' is interpreted as decimal number. If preceded by a '-', the
optional) The permissible values for hh[:mm[:ss]] are as timezone is east of the Prime Meridian, otherwise it is west
follows: ('+' is optional) The permissible values for hh[:mm[:ss]] are
as follows:
hh 0 <= hh <= 23 hh 0 <= hh <= 23
mm 0 <= mm <= 60 mm 0 <= mm <= 60
ss 0 <= ss <= 60 ss 0 <= ss <= 60
Offset has no default value.
Dst Three or more octets for the daylight savings timezone. Dst Three or more octets for the daylight savings timezone.
If Dst is missing, then daylight savings time does not If Dst is missing, then daylight savings time does not
apply in this locale. If no Offset follows Dst, then apply in this locale. If no Offset follows Dst, then
Dst is assumed to be one hour ahead of standard time. Dst is assumed to be one hour ahead of standard time.
Any character (or case) except a leading colon, digits, Any character (or case) except a leading colon, digits,
comma, minus or plus sign is allowed. comma, minus or plus sign is allowed.
Start Indicates the day of the year, in one of the formats Start Indicates the day of the year, in one of the formats
indicated below, when to change to daylight savings time. indicated below, when to change to daylight savings time.
The ``Time'' field (which follows immediately after a The ``Time'' field (which follows immediately after a
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Jn The julian day n, (1 <= n <= 365). Leap days are not Jn The julian day n, (1 <= n <= 365). Leap days are not
counted. counted.
n Zero-based julian day, (0 <= n <= 365). Leap days are n Zero-based julian day, (0 <= n <= 365). Leap days are
counted so it is possible to refer to Feb 29. counted so it is possible to refer to Feb 29.
Mm.n.d The ``d''th day, (0 <= d <= 6) of week ``n'' of month Mm.n.d The ``d''th day, (0 <= d <= 6) of week ``n'' of month
``m'' of the year (1 <= n <= 5, 1 <= m <= 12, where week ``m'' of the year (1 <= n <= 5, 1 <= m <= 12, where week
5 means last ``d'' day in month ``m'' which may occur in 5 means last ``d'' day in month ``m'' which may occur in
either the fourth or the fifth week. Week ``1'' is the either the fourth or the fifth week. Week ``1'' is the
first week in which the ``d'' day occurs. first week in which the ``d'' day occurs. Day ``0'' refers
Sunday, day ``1'' refers Monday and so on.
An Example: Examples:
For Eastern USA time zone, 1986, the Posix timezone string is as i) Indian Standard Time zone is represented as:
shown below:
IST-5:30
Here, ``IST'' refers the standard timezone and ``-5:30'' is the offset.
`-' sign in the offset says that the timezone is 5 hours and 30 minutes
ahead of UTC. Absence of ``Dst'' says that daylight savings doesn't apply
to this locale.
ii) For Eastern USA time zone, 1986, the timezone string is as shown below:
EST5EDT4,116/02:00:00,298/02:00:00 EST5EDT4,116/02:00:00,298/02:00:00
In this case, ``5'' is the Offset for Std, and ``4'' is the Offset It says:
for Dst. Start is the 116th day at 2am, and End is 298th day at 2am.
The standard time zone is in 5 hours behind UTC. The Daylight Savings
Timezone is 4 hours behind UTC. Day light savings starts at 116 day, i.e.,
April 27 02:00 AM standard time and ends at 298th day, i.e., October 26
02:00 AM daylight time.
It can also represented as:
EST5EDT,116/02:00:00,298/02:00:00
Since no offset follows the ``Dst'', daylight savings time is 1 hour
ahead of standard time, thus, it is 4 hours behind UTC.
iii) Representing ii) in the non POSIX standard way is:
America/New-York
It says that the locale belongs to New-York timezone in America, which
will be used as the index in to a timezone database to get more
information of the timezone.
6. Appearance of these option 6. Appearance of these option
The NTP servers and IEEE 1003.1 POSIX Timezone options MUST appear The NTP servers and Timezone options MUST appear only in the following
only in the following messages: Solicit, Advertise, Request, messages: Solicit, Advertise, Request, Confirm, Renew, Rebind,
Confirm, Renew, Rebind, Information-Request, Reply. Information-Request and Reply.
The option number for these options MAY appear in the Option Request
Option [1] in the following messages: Solicit, Request, Confirm, Renew,
Rebind, Information-Request and Reconfigure.
7. Security Considerations 7. Security Considerations
The NTP servers option may be used by an intruder DHCP server to The NTP servers option may be used by an intruder DHCP server to
cause DHCP clients to contact an intruder NTP server, resulting in cause DHCP clients to contact an intruder NTP server, resulting in
invalid synchronization of time in client and finally leading to invalid synchronization of time in client and finally leading to
time critical applications running inaccurately in client machine. time critical applications running inaccurately in client machine.
The time accuracy can be crucial to some security algorithms. For
example, it may cause expired certificates to gain a new life, making
the application less secured.
The IEEE 1003.1 POSIX Timezone option may be used by an intruder The Timezone option may be used by an intruder DHCP server to assign
DHCP server to assign invalid time zones, leading to timing issues invalid time zones, leading to timing issues for the applications running
for the applications running on the client machine. on the client machine.
To avoid attacks through these options, the DHCP client SHOULD use To avoid attacks through these options, the DHCP client SHOULD use
authenticated DHCP (see section "Authentication of DHCP messages" authenticated DHCP (see section "Authentication of DHCP messages"
in the DHCPv6 specification [4]). in the DHCPv6 specification [1]).
8. IANA Considerations 8. IANA Considerations
IANA is requested to assign an option code to these options from the IANA is requested to assign an option code to these options from the
option-code space defined in section "DHCPv6 Options" of the DHCPv6 option-code space defined in section "DHCPv6 Options" of the DHCPv6
specification [4]. specification [1].
References 9. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bound, J., Carney, M., Perkins, C., Lemon, T., Volz, B. and R.
Levels", BCP 14, RFC 2119, March 1997. Droms (ed.), "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", draft-ietf-dhc-dhcpv6-28 (work in progress), November
2002.
10. Informative References
[2] D. Mills. Simple Network Time Protocol (SNTP) Version 4 for [2] D. Mills. Simple Network Time Protocol (SNTP) Version 4 for
IPv4, IPv6 and OSI. Request for Comments (Informational) 2030, IPv4, IPv6 and OSI. Request for Comments (Informational) 2030,
Internet Engineering Task Force, October 1996. Internet Engineering Task Force, October 1996.
[3] IEEE, "1003.1 POSIX Timezone Specification", 1988. [3] IEEE, "1003.1 POSIX Timezone Specification", 1988.
[4] Bound, J., Carney, M., Perkins, C., Lemon, T., Volz, B. and R. [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Droms (ed.), "Dynamic Host Configuration Protocol for IPv6 Levels", BCP 14, RFC 2119, March 1997.
(DHCPv6)", draft-ietf-dhc-dhcpv6-23 (work in progress), February
2002.
Author's Addresses Author's Addresses
Vijayabhaskar A K Vijayabhaskar A K
Hewlett-Packard ESD-I Hewlett-Packard ESD-I
29, Cunningham Road 29, Cunningham Road
Bangalore - 560052 Bangalore - 560052
India India
Phone: +91-80-2051424 Phone: +91-80-2053085
E-Mail: vijayak@india.hp.com E-Mail: vijayak@india.hp.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
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included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
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Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
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"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement Acknowledgement
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Thanks to the DHC Working Group for their time and Internet Society. Thanks to the DHC Working Group for their time and
input into the specification. In particular, thanks to Jim Bound and input into the specification. In particular, thanks to (in alphabetical
Ralph Droms for their thorough review. Thanks to Mike Carney for his order) Bernie Volz, Jim Bound, Ralph Droms, Robert Elz for their thorough
abstract on Time Zone option. review. Special thanks to Robert Elz for his suggestions and help in
making this document more readable. Thanks to Mike Carney for his abstract
on Time Zone option.
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