draft-ietf-dhc-dhcpv6-opt-timeconfig-02.txt   draft-ietf-dhc-dhcpv6-opt-timeconfig-03.txt 
Network Working Group A.K. Vijayabhaskar Network Working Group A.K. Vijayabhaskar
Internet-Draft Hewlett-Packard Internet-Draft Hewlett-Packard
Expires: August 26, 2003 26 Feb 2003 Expires: April 16, 2004 15 Oct 2003
Time Configuration Options for DHCPv6 Time Configuration Options for DHCPv6
draft-ietf-dhc-dhcpv6-opt-timeconfig-02.txt draft-ietf-dhc-dhcpv6-opt-timeconfig-03.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). 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 Timezone specifier. information in DHCPv6: SNTP Server addresses - using which the clients
can synchronize their system time to that of the standard time
servers; Timezone specifier - used to set the timezone of the clients.
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 [1]. 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 [4] 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 "Terminology" section of the DHCPv6 specification.
4. Network Time Protocol (NTP) Servers option 4. Simple Network Time Protocol (SNTP) Servers option
The Network Time Protocol Servers option provides a list of one or The Simple Network Time Protocol Servers option provides a list of
more IP addresses of NTP [2] servers available to the client. The one or more IPv6 addresses of SNTP [2] servers available to the
NTP servers SHOULD be listed in the order of preference. client for synchronization. The SNTP servers SHOULD be listed in
the order of preference.
The format of the Network Time Protocol Servers option is as shown The format of the Simple Network Time Protocol Servers option is as
below: shown below:
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_NTP_SERVERS | option-len | | OPTION_SNTP_SERVERS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| NTP server (IP address) | | SNTP server (IPv6 address) |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| NTP server (IP address) | | SNTP server (IPv6 address) |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: OPTION_NTP_SERVERS (tbd) option-code: OPTION_SNTP_SERVERS (tbd)
option-len: Length of the 'NTP server' fields in octets; It must be option-len: Length of the 'SNTP server' fields in octets; It must be
a multiple of 16 a multiple of 16
NTP server: IP address of NTP server SNTP server: IPv6 address of SNTP server
5. Timezone option 5. Timezone option
The Timezone option is used by the server to convey client's timezone The Timezone option is used by the server to convey the timezone
information to the client. in which the client resides. The client is expected to set the
timezone in its system on receiving this option from the server.
The format of the 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 |
| ... | | ... |
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The format of the 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 the format as explained below. time-zone: Time zone of the client in the NVT-ASCII string format.
The format of this string is explained below:
Std[Offset[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 If "Offset" is specified, then the time-zone is represented in the
IEEE 1003.1 POSIX timezone format [3]. 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. If the time-zone comma, minus or plus sign is allowed. If there is no
is not represented in IEEE 1003.1 POSIX timezone format [3], Offset followed by the Std, then the timezone is not
then Std is treated as the index to the timezone database, represented in IEEE 1003.1 format. In this case, the
for example, a file name, from where additional information 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. 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, if the timezone is represented following Std is required, if the timezone is represented
in IEEE 1003.1 POSIX timezone format. Digits are always in IEEE 1003.1 POSIX timezone format. Digits are always
interpreted as decimal number. If preceded by a '-', the interpreted as decimal number. If preceded by a '-', the
timezone is east of the Prime Meridian, otherwise it is west timezone is east of the Prime Meridian, otherwise it is
('+' is optional) The permissible values for hh[:mm[:ss]] are west ('+' is optional) The permissible values for
as follows: 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
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
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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. Day ``0'' refers first week in which the ``d'' day occurs. Day ``0'' refers
Sunday, day ``1'' refers Monday and so on. Sunday, day ``1'' refers Monday and so on.
Examples: Examples:
i) Indian Standard Time zone is represented as: i) Indian Standard Time zone is represented as:
IST-5:30 IST-5:30
Here, ``IST'' refers the standard timezone and ``-5:30'' is the offset. Here, ``IST'' refers the standard timezone and ``-5:30'' is the
`-' sign in the offset says that the timezone is 5 hours and 30 minutes offset. `-' sign in the offset says that the timezone is 5 hours and
ahead of UTC. Absence of ``Dst'' says that daylight savings doesn't apply 30 minutes ahead of UTC. Absence of ``Dst'' says that daylight savings
to this locale. doesn't apply to this locale.
ii) For Eastern USA time zone, 1986, the timezone string is as shown below: 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
It says: It says:
The standard time zone is in 5 hours behind UTC. The Daylight Savings 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., Timezone is 4 hours behind UTC. Day light savings starts at 116 day,
April 27 02:00 AM standard time and ends at 298th day, i.e., October 26 i.e., April 27 02:00 AM standard time and ends at 298th day, i.e.,
02:00 AM daylight time. October 26 02:00 AM daylight time.
It can also represented as: It can also represented as:
EST5EDT,116/02:00:00,298/02:00:00 EST5EDT,116/02:00:00,298/02:00:00
Since no offset follows the ``Dst'', daylight savings time is 1 hour Since no offset follows the ``Dst'', daylight savings time is 1 hour
ahead of standard time, thus, it is 4 hours behind UTC. ahead of standard time, thus, it is 4 hours behind UTC.
iii) Representing ii) in the non POSIX standard way is: iii) Representing ii) in the non POSIX standard way is:
America/New-York America/New-York
It says that the locale belongs to New-York timezone in America, which It says that the locale belongs to New-York timezone in America,
will be used as the index in to a timezone database to get more which will be used as the index in to a timezone database to get
information of the timezone. more information of the timezone.
6. Appearance of these option 6. Usage of Timezone option
The NTP servers and Timezone options MUST appear only in the following The Timezone option has the flexibility of providing timezone
messages: Solicit, Advertise, Request, Confirm, Renew, Rebind, information in formats other than POSIX timezone, because
some vendor specific databases can provide more information than
POSIX Timezone string. The server SHOULD be configurable to send any
of the format specified in Section 5.
The timezone option can be used along with the Vendor Class
Option [1] to make sure that the client and server agree upon the
meaning of the string. For example, the clients running in different
OS expect the string in different formats. Here, the Vendor Class
Option [1] sent by clients can be used by the server to distinguish
between the clients to return the proper timezone string.
If the client is not able to interpret the timezone option sent
by the server, then it SHOULD ignore the option. It MAY contact
alternative DHCPv6 servers to obtain the timezone information.
7. Appearance of these options
The SNTP servers and Timezone options MUST NOT appear in other than
the following messages: Solicit, Advertise, Request, Renew, Rebind,
Information-Request and Reply. Information-Request and Reply.
The option number for these options MAY appear in the Option Request The option number for these options MAY appear in the Option Request
Option [1] in the following messages: Solicit, Request, Confirm, Renew, Option [1] in the following messages: Solicit, Request, Renew, Rebind,
Rebind, Information-Request and Reconfigure. Information-Request and Reconfigure.
7. Security Considerations 8. Security Considerations
The NTP servers option may be used by an intruder DHCP server to The SNTP servers option may be used by an intruder DHCPv6 server to
cause DHCP clients to contact an intruder NTP server, resulting in cause DHCPv6 clients to contact a rogue SNTP 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 The time accuracy can be crucial to some security algorithms. For
example, it may cause expired certificates to gain a new life, making example, it may cause expired certificates to gain a new life, making
the application less secured. the applications running on the client machine less secure. It can
even cause clients to set their time incorrectly, making them
vulnerable to replay attacks in protocols that use time stamps to
detect replays.
The Timezone option may be used by an intruder DHCP server to assign The Timezone option may be used by an intruder DHCPv6 server to
invalid time zones, leading to timing issues for the applications running assign invalid time zones, leading to timing issues for the
on the client machine. applications running on the client machine. For example, because of
wrongly configured timezone, there is a possibility that some critical
applications, which are supposed to start at a particular time don't
get started at that time. A delayed start of OS security update will
leave the client's machine vulnerable to security attacks.
To avoid attacks through these options, the DHCP client SHOULD use To avoid attacks through these options, the DHCPv6 client SHOULD use
authenticated DHCP (see section "Authentication of DHCP messages" authenticated DHCPv6 (see "Authentication of DHCP messages" section
in the DHCPv6 specification [1]). in the DHCPv6 specification [1]).
8. IANA Considerations 9. IANA Considerations
IANA is requested to assign an option code to these options from the IANA is requested to assign an option code to the following options
option-code space defined in section "DHCPv6 Options" of the DHCPv6 from the option-code space defined in "DHCPv6 Options" section of the
specification [1]. DHCPv6 specification [1].
9. Normative References Option Name Value Described in
OPTION_SNTP_SERVERS tbd Section 4.
OPTION_TIME_ZONE tbd Section 5.
10. Normative References
[1] Bound, J., Carney, M., Perkins, C., Lemon, T., Volz, B. and R. [1] Bound, J., Carney, M., Perkins, C., Lemon, T., Volz, B. and R.
Droms (ed.), "Dynamic Host Configuration Protocol for IPv6 Droms (ed.), "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", draft-ietf-dhc-dhcpv6-28 (work in progress), November (DHCPv6)", RFC 3315, July 2003.
2002.
10. Informative References 11. 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] Bradner, S., "Key words for use in RFCs to Indicate Requirement [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
Author's Addresses Author's Addresses
Vijayabhaskar A K Vijayabhaskar A K
Hewlett-Packard ESD-I Hewlett-Packard STSD-I
29, Cunningham Road 29, Cunningham Road
Bangalore - 560052 Bangalore - 560052
India India
Phone: +91-80-2053085 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 (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
skipping to change at page 7, line 37 skipping to change at page 8, line 37
"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 (in alphabetical input into the specification. In particular, thanks to (in
order) Bernie Volz, Jim Bound, Ralph Droms, Robert Elz for their thorough alphabetical order) Bernie Volz, Jim Bound, Margaret Wasserman, Ralph
review. Special thanks to Robert Elz for his suggestions and help in Droms, Robert Elz and Thomas Narten for their thorough review. Special
making this document more readable. Thanks to Mike Carney for his abstract thanks to Robert Elz for his suggestions and help in making this
on Time Zone option. document more readable. Thanks to Mike Carney for his abstract
on Timezone option.
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