draft-ietf-ntp-dhcpv6-ntp-opt-00.txt   draft-ietf-ntp-dhcpv6-ntp-opt-01.txt 
Network Working Group R. Gayraud Network Working Group R. Gayraud
Internet-Draft B. Lourdelet Internet-Draft B. Lourdelet
Intended status: Standards Track Cisco Systems, Inc. Intended status: Standards Track Cisco Systems, Inc.
Expires: November 15, 2008 May 14, 2008 Expires: January 5, 2009 July 4, 2008
Network Time Protocol (NTP) Server Option for DHCPv6 Network Time Protocol (NTP) Server Option for DHCPv6
draft-ietf-ntp-dhcpv6-ntp-opt-00.txt draft-ietf-ntp-dhcpv6-ntp-opt-01.txt
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Abstract Abstract
The NTP Server Option for DHCPv6 provides NTP (Network Time Protocol The NTP Server Option for DHCPv6 provides NTP (Network Time Protocol
version 4) configuration information to DHCPv6 hosts. version 4) configuration information to DHCPv6 hosts.
Table of Contents Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Related Work and Usage Model . . . . . . . . . . . . . . . 3 2.1. Related Work and Usage Model . . . . . . . . . . . . . . . 3
3. NTP Server Option for DHCPv6 . . . . . . . . . . . . . . . . . 4 3. NTP Server Option for DHCPv6 . . . . . . . . . . . . . . . . . 4
4. NTP Server Address Suboption . . . . . . . . . . . . . . . . . 5 3.1. NTP Server Address Suboption . . . . . . . . . . . . . . . 5
5. NTP Server FQDN Suboption . . . . . . . . . . . . . . . . . . 5 3.2. NTP Multicast Address Suboption . . . . . . . . . . . . . 6
6. Examples of use . . . . . . . . . . . . . . . . . . . . . . . 6 3.3. NTP Server FQDN Suboption . . . . . . . . . . . . . . . . 6
7. Appearance of this Option . . . . . . . . . . . . . . . . . . 7 4. Examples of use . . . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. Appearance of this Option . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . . 10
Intellectual Property and Copyright Statements . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
Intellectual Property and Copyright Statements . . . . . . . . . . 11
1. Requirements notation 1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Introduction 2. Introduction
This document defines a DHCPv6 option and associated suboptions to This document defines a DHCPv6 option and associated suboptions to
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3. NTP Server Option for DHCPv6 3. NTP Server Option for DHCPv6
This option serves as a container for all the information related to This option serves as a container for all the information related to
one NTP server. This option can appear multiple times in a DHCPv6 one NTP server. This option can appear multiple times in a DHCPv6
message. Each instance of this option is to be considered by the NTP message. Each instance of this option is to be considered by the NTP
client as a server to include in its configuration. client as a server to include in its configuration.
The option itself does not contain any value. Instead, it contains The option itself does not contain any value. Instead, it contains
one or several suboptions that carry NTP server configuration one or several suboptions that carry NTP server configuration
information. The first suboption in this option MUST be either information. The first suboption in this option MUST be
NTP_OPTION_SRV_ADDR or NTP_OPTION_SRV_FQDN. It carries the NTP NTP_OPTION_SRV_ADDR, NTP_OPTION_SRV_MC_ADDR or NTP_OPTION_SRV_FQDN.
server location, as an IPv6 address or as an NTP server FQDN. It carries the NTP server location, as a unicast or multicast IPv6
address or as an NTP server FQDN. While the FQDN option offers the
most deployment flexibility, resiliency as well as security, the IP
address options are defined to cover cases where a dependancy to DNS
is not desirable.
If the NTP server location is an IPv6 multicast address, the client If the NTP server location is an IPv6 multicast address, the client
SHOULD use this address as an NTP multicast group address and listen SHOULD use this address as an NTP multicast group address and listen
to messages sent to this group in order to synchronize its clock. to messages sent to this group in order to synchronize its clock.
The format of the NTP Server Option is: The format of the NTP Server 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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option-len: Total length of the included suboptions. option-len: Total length of the included suboptions.
A client that receives this option SHOULD use the specified NTP A client that receives this option SHOULD use the specified NTP
server to synchronize its clock. server to synchronize its clock.
This document does not define any priority between the client's This document does not define any priority between the client's
embedded configuration and the NTP servers discovered via this embedded configuration and the NTP servers discovered via this
option. In particular, the client is allowed to simultaneously use option. In particular, the client is allowed to simultaneously use
its own configured NTP servers and the servers discovered via DHCP. its own configured NTP servers and the servers discovered via DHCP.
4. NTP Server Address Suboption 3.1. NTP Server Address Suboption
This suboption is intended to appear inside the OPTION_NTP_SERVER This suboption is intended to appear inside the OPTION_NTP_SERVER
option. It specifies the IPv6 address of an NTP server available to option. It specifies the IPv6 unicast address of an NTP server
the client. An example of use is present in Section 6. available to the client. An example of use is present in Section 4.
This suboption can also be used to carry the IPv6 multicast group
address used by NTP on the local network.
The format of the NTP Server Address Suboption is: The format of the NTP Server Address Suboption 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP_SUBOPTION_SRV_ADDR | suboption-len = 16 | | NTP_SUBOPTION_SRV_ADDR | suboption-len = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| | | |
| IPv6 address of NTP server | | IPv6 address of NTP server |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
suboption-code: NTP_SUBOPTION_SRV_ADDR (1), suboption-code: NTP_SUBOPTION_SRV_ADDR (1),
suboption-len: 16. suboption-len: 16.
5. NTP Server FQDN Suboption 3.2. NTP Multicast Address Suboption
This suboption is intended to appear inside the OPTION_NTP_SERVER
option. It specifies the IPv6 address of the IPv6 multicast group
address used by NTP on the local network. An example of use is
present in Section 4.
The format of the NTP Multicast Address Suboption is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP_SUBOPTION_MC_ADDR | suboption-len = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
| Multicast IPv6 address |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
suboption-code: NTP_SUBOPTION_MC_ADDR (2),
suboption-len: 16.
3.3. NTP Server FQDN Suboption
This suboption is intended to appear inside the OPTION_NTP_SERVER This suboption is intended to appear inside the OPTION_NTP_SERVER
option. It specifies the FQDN of an NTP server available to the option. It specifies the FQDN of an NTP server available to the
client. client.
The format of the NTP Server FQDN Suboption is: The format of the NTP Server FQDN Suboption 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP_SUBOPTION_SRV_FQDN | suboption-len | | NTP_SUBOPTION_SRV_FQDN | suboption-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| FQDN of NTP server | | FQDN of NTP server |
: : : :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
suboption-code: NTP_SUBOPTION_SRV_FQDN (2), suboption-code: NTP_SUBOPTION_SRV_FQDN (3),
suboption-len: Length of the included FQDN field, suboption-len: Length of the included FQDN field,
FQDN: Fully Qualidied Domain Name of the NTP server. This FQDN: Fully Qualidied Domain Name of the NTP server. This
field MUST be encoded as described in [RFC3315], field MUST be encoded as described in [RFC3315],
section 8. section 8.
6. Examples of use 4. Examples of use
To instruct a client to use an NTP server located at address 2001: To instruct a client to use an NTP server located at address 2001:
db8::1, a DHCP server shall use the following format: db8::1, a DHCP server shall use the following format:
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_SERVER | option-len = 20 | | OPTION_NTP_SERVER | option-len = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP_SUBOPTION_SRV_ADDR | suboption-len = 16 | | NTP_SUBOPTION_SRV_ADDR | suboption-len = 16 |
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+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
To instruct a client to join the FF05::101 NTP multicast group, a To instruct a client to join the FF05::101 NTP multicast group, a
DHCP server shall use the following format: DHCP server shall use the following format:
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_SERVER | option-len = 20 | | OPTION_NTP_SERVER | option-len = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP_SUBOPTION_SRV_ADDR | suboption-len = 16 | | NTP_SUBOPTION_MC_ADDR | suboption-len = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| IPv6 address = FF05::101 | | IPv6 address = FF05::101 |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7. Appearance of this Option 5. Appearance of this Option
The OPTION_NTP_SERVER option can appear multiple times in a DHCPv6 The OPTION_NTP_SERVER option can appear multiple times in a DHCPv6
message. The order in which these options appear is not significant. message. The order in which these options appear is not significant.
The client uses its usual algorithms to determine which server(s) or The client uses its usual algorithms to determine which server(s) or
multicast group(s) should be prefered to synchronize its clock. multicast group(s) should be prefered to synchronize its clock.
The OPTION_NTP_SERVER option MUST NOT appear in messages other than The OPTION_NTP_SERVER option MUST NOT appear in messages other than
the following: Solicit, Advertise, Request, Renew, Rebind, the following: Solicit, Advertise, Request, Renew, Rebind,
Information-Request, and Reply. If this option appears in messages Information-Request, and Reply. If this option appears in messages
other than those specified above, the receiver SHOULD ignore it. other than those specified above, the receiver SHOULD ignore it.
The option number for this option MAY appear in the "Option Request" The option number for this option MAY appear in the "Option Request"
option [RFC3315] in the following messages: Solicit, Request, Renew, option [RFC3315] in the following messages: Solicit, Request, Renew,
Rebind, Information-Request, and Reconfigure. If this option number Rebind, Information-Request, and Reconfigure. If this option number
appears in the "Option Request" option in messages other than those appears in the "Option Request" option in messages other than those
specified above, the receiver SHOULD ignore it. specified above, the receiver SHOULD ignore it.
8. Security Considerations 6. Security Considerations
This option could be used by an intruder to advertise the address of This option could be used by an intruder to advertise the address of
a malicious NTP server and adversely affect the clock of clients on a malicious NTP server and adversely affect the clock of clients on
the network. The consequences of such an attack can be critical, the network. The consequences of such an attack can be critical,
because many security protocols depend on time synchronization to run because many security protocols depend on time synchronization to run
their algorithms. As an example, an attacker could break their algorithms. As an example, an attacker could break
connectivity between SEND-enabled nodes [RFC3971], simply by connectivity between SEND-enabled nodes [RFC3971], simply by
affecting the clock on these nodes. affecting the clock on these nodes.
To prevent these attacks, it is strongly advisable to secure the use To prevent these attacks, it is strongly advisable to secure the use
of this option either by: of this option either by:
- using the NTPv4 Autokey public key authentication, as defined - using the NTPv4 Autokey public key authentication, as defined
in [draft-autokey] or, in [draft-autokey] or,
- using authenticated DHCP as described in [RFC3315] section 21. - using authenticated DHCP as described in [RFC3315] section 21.
9. IANA Considerations 7. IANA Considerations
When this document is published, the IANA is requested to assign an When this document is published, the IANA is requested to assign an
option code from the "DHCPv6 Options Codes" registry for option code from the "DHCPv6 Options Codes" registry for
OPTION_NTP_SERVER. OPTION_NTP_SERVER.
10. References 8. References
10.1. Normative References 8.1. Normative References
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003. IPv6 (DHCPv6)", RFC 3315, July 2003.
[draft-ntpv4] [draft-ntpv4]
Burbank, J., Kasch, W., Martin, J., and D. Mills, "Network Burbank, J., Kasch, W., Martin, J., and D. Mills, "Network
Time Protocol Version 4 Protocol And Algorithms Time Protocol Version 4 Protocol And Algorithms
Specification", draft-ietf-ntp-ntpv4-proto-08 (work in Specification", draft-ietf-ntp-ntpv4-proto-08 (work in
progress), November 2007. progress), November 2007.
[draft-autokey] [draft-autokey]
Haberman, B. and D. Mills, "Network Time Protocol Version Haberman, B. and D. Mills, "Network Time Protocol Version
4 Autokey Specification", draft-ietf-ntp-autokey-00 (work 4 Autokey Specification", draft-ietf-ntp-autokey-00 (work
in progress), September 2007. in progress), September 2007.
10.2. Informative References 8.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005. Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC4075] Kalusivalingam, V., "Simple Network Time Protocol (SNTP) [RFC4075] Kalusivalingam, V., "Simple Network Time Protocol (SNTP)
Configuration Option for DHCPv6", RFC 4075, May 2005. Configuration Option for DHCPv6", RFC 4075, May 2005.
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