draft-ietf-dhc-v6exts-04.txt   draft-ietf-dhc-v6exts-05.txt 
Internet Engineering Task Force C. Perkins Internet Engineering Task Force C. Perkins
INTERNET DRAFT IBM INTERNET DRAFT Sun Microsystems
22 November 1996 27 February 1997
Extensions for DHCPv6 Extensions for DHCPv6
draft-ietf-dhc-v6exts-04.txt draft-ietf-dhc-v6exts-05.txt
Status of This Memo Status of This Memo
This document is a submission to the Dynamic Host Configuration This document is a submission to the Dynamic Host Configuration
Working Group of the Internet Engineering Task Force (IETF). Comments Working Group of the Internet Engineering Task Force (IETF). Comments
should be submitted to the dhcp-v6@bucknell.edu mailing list. should be submitted to the dhcp-v6@bucknell.edu mailing list.
Distribution of this memo is unlimited. Distribution of this memo is unlimited.
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
skipping to change at page 1, line 56 skipping to change at page 1, line 56
valid extensions. valid extensions.
Contents Contents
Status of This Memo i Status of This Memo i
Abstract i Abstract i
1. Introduction 1 1. Introduction 1
2. DHCPv6 Extension Field Format 1 2. DHCPv6 Extension Field Format 2
2.1. Character Encoding and String Issues . . . . . . . . . . 2
3. Padding and End extension specifications 2 3. Padding and End extension specifications 3
3.1. Pad Extension . . . . . . . . . . . . . . . . . . . . . . 2 3.1. Pad Extension . . . . . . . . . . . . . . . . . . . . . . 3
3.2. End Extension . . . . . . . . . . . . . . . . . . . . . . 2 3.2. End Extension . . . . . . . . . . . . . . . . . . . . . . 3
4. IPv6 Address Extension 2 4. IPv6 Address Extension 3
4.1. Client Considerations for the IPv6 Address extension . . 4 4.1. Client Considerations for the IPv6 Address extension . . 6
4.1.1. Address Lifetimes . . . . . . . . . . . . . . . . 4 4.1.1. Address Lifetimes . . . . . . . . . . . . . . . . 6
4.1.2. Use with the DHCP Request message . . . . . . . . 5 4.1.2. Use with the DHCP Request message . . . . . . . . 6
4.1.3. Use with the DHCP Release message . . . . . . . . 6 4.1.3. Receiving as part of the DHCP Reply message . . . 7
4.2. Server Considerations for the IPv6 Address extension . . 6 4.1.4. Use with the DHCP Release message . . . . . . . . 7
4.2.1. Use with the DHCP Advertise message . . . . . . . 6 4.2. Server Considerations for the IPv6 Address extension . . 8
4.2.1. Use with the DHCP Advertise message . . . . . . . 8
4.2.2. Receiving a DHCP Request with the IPv6 Address 4.2.2. Receiving a DHCP Request with the IPv6 Address
Extension . . . . . . . . . . . . . . . . 6 Extension . . . . . . . . . . . . . . . . 8
4.2.3. Use with the DHCP Reply message . . . . . . . . . 7 4.2.3. Use with the DHCP Reply message . . . . . . . . . 8
4.2.4. Use with the DHCP Reconfigure message . . . . . . 7 4.2.4. Use with the DHCP Reconfigure message . . . . . . 9
4.3. DHCP Relay Considerations . . . . . . . . . . . . . . . . 7 4.3. DHCP Relay Considerations . . . . . . . . . . . . . . . . 9
5. General Extensions 8
5.1. Time Offset . . . . . . . . . . . . . . . . . . . . . . . 8
5.2. Domain Name Server Extension . . . . . . . . . . . . . . 8
5.3. Domain Name . . . . . . . . . . . . . . . . . . . . . . . 8
6. Service Location Extensions 9 5. General Extensions 9
6.1. Directory Agent Extension . . . . . . . . . . . . . . . . 9 5.1. Time Offset . . . . . . . . . . . . . . . . . . . . . . . 10
6.2. Service Scope Extension . . . . . . . . . . . . . . . . . 10 5.2. Domain Name Server Extension . . . . . . . . . . . . . . 10
5.3. Domain Name . . . . . . . . . . . . . . . . . . . . . . . 11
7. IP Layer Parameters per Interface 10 6. Service Location Extensions 11
7.1. Static Route Extension . . . . . . . . . . . . . . . . . 10 6.1. Directory Agent Extension . . . . . . . . . . . . . . . . 11
6.2. Service Scope Extension . . . . . . . . . . . . . . . . . 12
8. TCP Parameters 11 7. IP Layer Parameters per Interface 13
8.1. TCP Keepalive Interval Extension . . . . . . . . . . . . 11 7.1. Static Route Extension . . . . . . . . . . . . . . . . . 13
9. Vendor Specific Information 11 8. TCP Parameters 14
8.1. TCP Keepalive Interval Extension . . . . . . . . . . . . 14
9. Vendor Specific Information 14
10. DHCPv6 Extensions 12 10. DHCPv6 Extensions 16
10.1. Maximum DHCPv6 Message Size Extension . . . . . . . . . . 12 10.1. Maximum DHCPv6 Message Size Extension . . . . . . . . . . 16
10.2. Class Identifier . . . . . . . . . . . . . . . . . . . . 13 10.2. Class Identifier . . . . . . . . . . . . . . . . . . . . 16
10.3. Reconfigure Multicast Address . . . . . . . . . . . . . . 13 10.3. Reconfigure Multicast Address . . . . . . . . . . . . . . 17
10.4. Renumber DHCPv6 Server Address . . . . . . . . . . . . . 14 10.4. Renumber DHCPv6 Server Address . . . . . . . . . . . . . 17
10.5. Client-Server Authentication Extension . . . . . . . . . 14 10.5. Client-Server Authentication Extension . . . . . . . . . 18
11. Security Considerations 15 11. Security Considerations 19
11.1. Replay Protection . . . . . . . . . . . . . . . . . . . . 15 11.1. Replay Protection . . . . . . . . . . . . . . . . . . . . 19
11.2. Default Authentication Algorithm . . . . . . . . . . . . 15 11.2. Default Authentication Algorithm . . . . . . . . . . . . 19
12. New Extensions 16 12. New Extensions 20
13. Acknowledgements 16 13. Acknowledgements 20
Chair's Address 18 Chair's Address 22
Author's Address 18 Author's Address 22
1. Introduction 1. Introduction
This document specifies extensions for use with the Dynamic This document specifies extensions for use with the Dynamic
Host Configuration Protocol for IP version 6, DHVPv6. The full Host Configuration Protocol for IP version 6, DHVPv6. The full
description of DHCPv6 message formats may be found in the DHCPv6 description of DHCPv6 message formats may be found in the DHCPv6
specification document [3]. specification document [3].
This document defines the format of information in the last field This document defines the format of information in the last field
of DHCPv6 messages ('extensions'). The extensions defined within of DHCPv6 messages ('extensions'). The extensions defined within
this document specify a generalized use of this area for giving this document specify a generalized use of this area for giving
information useful to a wide class of machines, operating systems information useful to a wide class of machines, operating systems
and configurations. Sites with a single DHCPv6 server that is and configurations. Sites with a single DHCPv6 server that is
shared among heterogeneous clients may choose to define other, site- shared among heterogeneous clients may choose to define other, site-
specific formats for the use of the 'extensions' field. specific formats for the use of the 'extensions' field.
Section 2 of this memo describes the formats of DHCPv6 extensions. Section 2 of this memo describes the formats of DHCPv6 extensions.
Information on registering new extensions is contained in section 12. Information on registering new extensions is contained in section 12.
Although extension numbers in this document correspond closely to the The other sections organize the format descriptions of various
analogous numbers in the options specification for IPv4 [1], there is extensions according to their general type, as follows:
no requirement to keep numbering future extensions in any consistent
manner except purely as a matter of editorial and cross-referencing - IP Address extension
convenience.
- Miscellaneous host configuration
- Service Location configuration
- Miscellaneous network layer
- TCP
- Vendor Specific
- DHCPv6
Future applications will make extensive use of an ever-increasing Future applications will make extensive use of an ever-increasing
number and variety of network services. It is expected that client number and variety of network services. It is expected that client
needs for creating connections with these future network services needs for creating connections with these future network services
will be satisfied by the Service Location Protocol [10], and not will be satisfied by the Service Location Protocol [12], and not
DHCPv6. DHCP is expected to be used for the kinds of configuration DHCPv6. DHCP is expected to be used for the kinds of configuration
that enable clients to become fully functional as self-contained that enable clients to become fully functional as self-contained
network entities, but not the kinds of configuration that might be network entities, but not the kinds of configuration that might be
required by applications running above the network or transport layer required by applications running above the network or transport layer
protocol levels. protocol levels.
2. DHCPv6 Extension Field Format 2. DHCPv6 Extension Field Format
DHCPv6 extensions have the same format as the BOOTP "vendor DHCPv6 extensions have the same format as the BOOTP "vendor
extensions" defined in RFC 1497 [8]. Extensions may be fixed length extensions" defined in RFC 1497 [9]. Extensions may be fixed length
or variable length. All extensions except for the pad extension or variable length. All extensions except for the pad extension
begin with a type field which is two octets long, which uniquely begin with a type field which is two octets long, which uniquely
identifies the extension. Fixed-length extensions without data identifies the extension. Fixed length extensions without data
consist of only the two octet type field. Only extensions 0 and consist of only the two octet type field. Only extensions 0 and
65535 are fixed length. All other extensions are variable-length 65535 are fixed length. All other extensions are variable length
with a two octet length field following the type octets. The value with a two octet length field following the type octets. The value
of the length octets does not include the two octets specifying the of the length octets does not include the two octets specifying the
type and length. The length octet is followed by "length" octets type and length. The length octet is followed by "length" octets
of data. In the case of some variable-length extensions the length of data. In the case of some variable length extensions the length
field is a constant but must still be specified. field is a constant but must still be specified.
Any extensions defined subsequent to this document should contain a Any extensions defined subsequent to this document should contain a
length field of two octets in length even if the length is fixed or length field of two octets in length even if the length is fixed or
zero. Unknown options MAY be skipped by ignoring the number of bytes zero. Unknown options MAY be skipped by ignoring the number of bytes
specified in the length octets. All multi-octet quantities are in specified in the length octets. All multi-octet quantities are in
network byte-order. network byte-order.
Extension types 32768 to 65534 (decimal) are reserved for Extension types 32768 to 65534 (decimal) are reserved for
site-specific extensions. site-specific extensions.
All of the extensions described in this document will also have their All of the extensions described in this document will also have their
default values specified, if any. default values specified, if any.
2.1. Character Encoding and String Issues
Values for character encoding can be found in the Internet Assigned
Numbers Authority's (IANA) database
http://www.isi.edu/in-notes/iana/assignments/character-sets
and have the values referred by the MIBEnum value.
The encoding will determine the interpretation of all character data
in the corresponding fields of particular extensions. There is no
way to mix ASCII and UNICODE, for example. All responses must be in
the character set of the request or use US-ASCII. If a request is
sent to a DHCP server, which is unable to manipulate or store the
character set of the incoming message, the request will fail. The
server returns a CHARSET_NOT_UNDERSTOOD error (24) in a DHCP Reply
message in this case. Requests using US-ASCII (MIBEnum value == 3)
will never fail for this reason, since all DHCP entities must be able
to accept this character set. All DNS-related strings are presumed
to be encoded in US-ASCII.
3. Padding and End extension specifications 3. Padding and End extension specifications
3.1. Pad Extension 3.1. Pad Extension
The pad extension can be used to cause subsequent fields to align on The pad extension can be used to cause subsequent fields to align on
word boundaries. word boundaries.
The type code for the pad extension is 0, and its length is 1 octet. The Type for the pad extension is 0, and its length is 1 octet.
Type Type
+-----+ +-----+
| 0 | | 0 |
+-----+ +-----+
3.2. End Extension 3.2. End Extension
The end extension marks the end of valid information in the vendor The end extension marks the end of valid information in the vendor
field. Subsequent octets should be filled with pad extensions. field. Subsequent octets should be filled with pad extensions.
The type for the end extension is 65535, and its length is 2 octets. The Type for the end extension is 65535, and its length is 2 octets.
Type Type
+-----+-----+ +-----+-----+
| 65535 | | 65535 |
+-----+-----+ +-----+-----+
4. IPv6 Address Extension 4. IPv6 Address Extension
The IPv6 Address extension is the most essential of all the DHCPv6 The IPv6 Address extension is the most essential of all the DHCPv6
extensions. It is relatively complex and and can be used by both extensions. It can be used by both client and server in various
client and server in various ways. Since the IPv6 Address option ways. Since the IPv6 Address option can be used more than once in
can be used more than once in the same DHCP message, all information the same DHCP message, all information relevant to a particular IPv6
relevant to a particular IPv6 allocation has to be collected together allocation has to be collected together in the same extension. Some
in the same extension, hence the added complexity. Some of this of the fields within the IPv6 Address extension can specify how
added complexity also derives from various possible ways that DNS [13] may be updated.
updating DNS may be specified within the IPv6 Address extension.
An IPv6 Address Extension can contain at most one IPv6 address. To An IPv6 Address Extension can contain at most one IPv6 address. To
specify more than one IPv6 address, multiple extensions are used. specify more than one IPv6 address, multiple extensions are used.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ext-type | ext-length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C|L|Q|A|P| reserved | pfx-size | | pfx-size | error-code |C|L|Q|A|P| reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (if present) | | (if present) |
| client address (16 octets) | | client address (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (if present) preferred lifetime (4 octets) | | (if present) preferred lifetime (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (if present) valid lifetime (4 octets) | | (if present) valid lifetime (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (if present) DNS name (variable length) ... | (if present) DNS name (variable length) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ext-type 1 Type 1
ext-length Length (variable) The length of the Extension.
The length of the Extension.
pfx-size
If the client address is present (the 'C' bit is set),
a nonzero pfx-size indicates the length of the routing
prefix, counting the number of leading 1 bits to be
applied to the client's IPv6 address to get the routing
prefix. Otherwise, if the 'C' bit is not set, pfx-size
MUST be zero.
error-code
If the server is unable to honor the client's request,
the reason is indicated in the error-code. Current
values are as follows:
0 request granted, no errors
16 dynDNS Not Available at this time
17 dynDNS Not Implemented
18 Authentication failed for this client
19 Authoritative DNS Server could not be found
20 Resource AAAA Record Parameter Problem
21 Resource PTR Record Parameter Problem
22 Unable to honor required extension parameters
23 DNS name string error
C If the 'C' bit is set, the field containing the IPv6 C If the 'C' bit is set, the field containing the IPv6
address for the client is present in the extension. address for the client is present in the extension.
L If the 'L' bit is set, the preferred and valid lifetimes L If the 'L' bit is set, the preferred and valid lifetimes
are present in the extension. are present in the extension.
Q If the 'Q' bit is set, the fields included by the client Q If the 'Q' bit is set, the fields included by the client
are required, and must be made available by the server or are required, and must be made available by the server or
else the extension must be rejected. else the extension must be rejected.
A If the 'A' bit is set, the server MUST ensure that the A If the 'A' bit is set, the server MUST ensure that the
DNS is updated with a new AAAA record, as specified DNS is updated with a new AAAA record, as specified
by the client's FQDN, before responding with the by the client's FQDN, before responding with the
corresponding DHCP Reply. corresponding DHCP Reply.
P If the 'P' bit is set, the server MUST ensure that the P If the 'P' bit is set, the server MUST ensure that the
DNS is updated with a new PTR record, as specified by the DNS is updated with a new PTR record, as specified by the
client's FQDN, before responding with the corresponding client's FQDN, before responding with the corresponding
DHCP Reply. DHCP Reply.
rsv MUST be zero. reserved MUST be zero.
pfx-size
If the client address is present (the 'C' bit is set),
then the pfx-size indicates the length of the routing
prefix, counting the number of leading 1 bits to be
applied to the client's IPv6 address to get the routing
prefix. Otherwise, if the 'C' bit is not set, pfx-size
MUST be zero. NOTE: the pfx-size field is only 7 bits
long.
client address client address
The IPv6 address to be allocated by the server for use by The IPv6 address to be allocated by the server for use by
the client (16 octets long). the client (16 octets long).
preferred lifetime preferred lifetime
The preferred lifetime of the IPv6 address in seconds The preferred lifetime of the IPv6 address in seconds
valid lifetime valid lifetime
The valid lifetime of the IPv6 address in seconds The valid lifetime of the IPv6 address in seconds
DNS name DNS name
The DNS name (a zero-terminated string of ASCII octets) The DNS name (a zero-terminated string of ASCII octets)
to be used by the client (variable length). to be used by the client (variable length).
The DNS name can be a host name, which does not contain the '.' The DNS name can be a host name, which does not contain the '.'
ASCII character as a separator between DNS hierarchy components. Any ASCII character as a separator between DNS hierarchy components. Any
name containing the '.' is treated as a Fully Qualified Domain Name name containing the '.' is treated as a Fully Qualified Domain Name
(FQDN). The length of the DNS name may be determined by subtracting, (FQDN). The length of the DNS name may be determined by subtracting,
from the ext-length, the length of those fixed-length fields which from the Length, the length of those fixed length fields which are
are present. If the last byte of the DNS name is not zero, the IPv6 present. If the last byte of the DNS name is not zero, the IPv6
Address Extension MUST be rejected. Address Extension MUST be rejected, with error code 23.
4.1. Client Considerations for the IPv6 Address extension 4.1. Client Considerations for the IPv6 Address extension
4.1.1. Address Lifetimes 4.1.1. Address Lifetimes
An IPv6 address returned to a client has a preferred and valid An IPv6 address returned to a client has a preferred and valid
lifetime. The lifetimes represent the lease for addresses provided lifetime. The lifetimes represent the lease for addresses provided
to the client, from the server. to the client, from the server.
The DHCPv6 philosophy is that the client has the responsibility to The DHCPv6 philosophy is that the client has the responsibility to
skipping to change at page 6, line 13 skipping to change at page 7, line 26
Request, by specifying the 'Q' (Required) bit. Request, by specifying the 'Q' (Required) bit.
When a client requests an IP address, it MUST maintain a record for When a client requests an IP address, it MUST maintain a record for
the server which allocates that address, so that the client can (if the server which allocates that address, so that the client can (if
necessary) in the future necessary) in the future
- Renew the lifetime with the same server, or - Renew the lifetime with the same server, or
- Release the address, using DHCP Release. - Release the address, using DHCP Release.
Upon reception of a new IP address, the client must perform Duplicate 4.1.3. Receiving as part of the DHCP Reply message
Address Detection (DAD) [7]; however, if the address has already been
allocated to the client and it is merely renewing the lifetime of the
address, the client does not have to perform DAD each time.
4.1.3. Use with the DHCP Release message When the client receives an IP address extension as part of a DHCP
Reply which it accepts (see [3]), it first inspects the error-code
to see whether the requested information has been granted. If the
error-code is nonzero, the client should log the error, display
the error condition for action by the user and/or the network
administrator. Nonzero error-codes almost always indicate that the
client will be unable to use DHCP services until the client's request
can be modified, or until the DHCP server can be given updated
configuration information for the client.
Upon reception of a new IP address with a lifetime, the client must
perform Duplicate Address Detection (DAD) [11]; however, if the
address has already been allocated to the client and it is merely
renewing the lifetime of the address, the client does not have to
perform DAD each time. If the client receives a new IP address with
zero valid lifetime, the client MUST immediately discontinue using
that IP address.
4.1.4. Use with the DHCP Release message
In DHCP Release (for each address extension): In DHCP Release (for each address extension):
- Client can include an IPv6 address and/or name and/or FQDN. - Client can include an IPv6 address and/or name and/or FQDN.
- Server MUST update DNS to delete the AAAA record if the server - Server MUST update DNS to delete the AAAA record if the server
originally updated DNS when the address was allocated to the originally updated DNS when the address was allocated to the
client. Likewise for the PTR record. client. Likewise for the PTR record.
- If the client, on the other hand, took charge of the DNS updates, - If the client, on the other hand, took charge of the DNS updates,
skipping to change at page 7, line 18 skipping to change at page 8, line 47
4.2.3. Use with the DHCP Reply message 4.2.3. Use with the DHCP Reply message
In a DHCP Reply message (for each address extension) the server MUST In a DHCP Reply message (for each address extension) the server MUST
indicate indicate
- the preferred lifetime - the preferred lifetime
- the valid lifetime - the valid lifetime
- the status of the request
If the Reply is a response to a DHCP Release, the lifetimes MUST both If the Reply is a response to a DHCP Release, the lifetimes MUST both
be zero. be zero.
In a DHCP Reply message (for each address extension) the server MAY In a DHCP Reply message (for each address extension) the server MAY
indicate indicate
- the DNS name - the DNS name
- whether AAAA has been DNS updated - whether AAAA has been DNS updated (by setting the 'A' bit)
- whether PTR has been DNS updated - whether PTR has been DNS updated (by setting the 'P' bit)
If the client requests updates, and sets the 'Q' bit, the server MUST If the client requests updates, and sets the 'Q' bit, the server MUST
NOT issue the DHCP Reply until after receiving positive indication NOT issue the DHCP Reply until after receiving positive indication
that the DNS update has indeed been performed. that the DNS update has indeed been performed. If the 'Q' bit has
been set, and the server cannot honor the IP address extension, it
MUST return a DHCP reply with the error code 22.
Subsequently, the client can update DNS if needed (i.e., the server Otherwise, the client can subsequently update DNS if needed (i.e.,
didn't do it). the server didn't do it).
If the server receives a DHCP Request from one of its clients
whose address it wishes to invalidate, it can cause the client to
discontinue use of the old address by including valid and preferred
lifetimes with a value of zero.
To perform renumbering, the server will include two IP address
extensions, one to invalidate the old address, and another to give
the client its new address.
4.2.4. Use with the DHCP Reconfigure message 4.2.4. Use with the DHCP Reconfigure message
In DHCP Reconfigure (for each address extension) the server MAY In DHCP Reconfigure (for each address extension) the server MAY
indicate the DNS name. indicate the DNS name.
4.3. DHCP Relay Considerations 4.3. DHCP Relay Considerations
The DHCP Relay MUST NOT change any information in any DHCPv6 The DHCP Relay MUST NOT change any information in any DHCPv6
Extension fields. All Extension information flows between DHCPv6 Extension fields. All Extension information flows between DHCPv6
Server and DHCPv6 Client without modification by any Relay. Server and DHCPv6 Client without modification by any Relay.
5. General Extensions 5. General Extensions
The following extensions are important for many DHCPv6 clients, and The following extensions are important for many DHCPv6 clients, and
are not specific to any upper-level protocol. are not specific to any upper-level protocol.
5.1. Time Offset 5.1. Time Offset
The time offset field specifies the offset of the client's subnet 0 1 2 3
in seconds from Coordinated Universal Time (UTC). The offset is 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
expressed as a signed 32-bit integer. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
The type for the time offset extension is 2, and its length is 4 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
octets. | Time Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Length Time Offset The Type for the time offset extension is 2, and its length is 4
+-----+-----+-----+-----+-----+-----+-----+-----+ octets. The time offset field specifies the offset of the client's
| 8 | 4 | n1 | n2 | n3 | n4 | subnet in seconds from Coordinated Universal Time (UTC). The offset
+-----+-----+-----+-----+-----+-----+-----+-----+ is expressed as a signed 32-bit integer.
5.2. Domain Name Server Extension 5.2. Domain Name Server Extension
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain Name System server addresses |
| (16 octets each) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The domain name server extension specifies a list of Domain Name The domain name server extension specifies a list of Domain Name
System (STD 13, RFC 1035 [6]) name servers available to the client. System (STD 13, RFC 1035 [8]) name servers available to the client.
Servers SHOULD be listed in order of preference. Servers SHOULD be listed in order of preference.
The type for the domain name server extension is 6. The minimum The Type for the domain name server extension is 6. The minimum
length for this extension is 16 octets, and the length MUST always be length for this extension is 16 octets, and the length MUST always be
a multiple of 16. a multiple of 16.
Type Length Address 1 Address 2
+-----+-----+-----+-----+-----+-----+---+-----+-----+-----+---+-----+---
| 9 | n | a1 | a2 |...| a16 | a1 | a2 |...| a16 |...
+-----+-----+-----+-----+-----+-----+---+-----+-----+-----+---+-----+---
5.3. Domain Name 5.3. Domain Name
This extension specifies the domain name that client should use when This extension specifies the domain name that client should use when
resolving hostnames via the Domain Name System. resolving hostnames via the Domain Name System.
The type for this extension is 10. Its minimum length is 1. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain Name (variable length) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Length Domain Name The Type for this extension is 10. Its minimum length is 1.
+-----+-----+-----+-----+-----+-----+-----+-----+--
| 10 | n | d1 | d2 | d3 | d4 | ... The domain name is a null-terminated ASCII string, length octets in
+-----+-----+-----+-----+-----+-----+-----+-----+-- size, including the terminating zero octet.
The domain name is a null-terminated ASCII string, of length 'n'
octets including the terminating null octet.
If the Domain Name extension is not specified, and the IPv6 Address If the Domain Name extension is not specified, and the IPv6 Address
extension received by a client contains a FQDN, then the client may extension received by a client contains a FQDN, then the client may
take the part of the FQDN after the first '.' octet as the Domain take the part of the FQDN after the first '.' octet as the Domain
Name. Name.
6. Service Location Extensions 6. Service Location Extensions
6.1. Directory Agent Extension 6.1. Directory Agent Extension
This extension specifies a Directory Agent (DA) [10], along with zero This extension specifies a Directory Agent (DA) [12], along with
or more scopes supported by that DA. zero or more scopes supported by that DA. A scope, in the Service
Location Protocol, is a way of restricting the accessibility of
service entries (URLs) to User Agents or Service Agents who belong to
a particular class. For instance, in an academic institution, the
math department may decide to allow their Directory Agents to provide
service only for agents with the "math" scope.
The type for this extension is 16. Each scope MUST be a The Type for this extension is 16. Each scope MUST be a
null-terminated string of ASCII octets. The lengths of the strings null-terminated string of ASCII octets. The lengths of the strings
(measured in octets) are only indicated implicitly by their null (measured in octets) are only indicated implicitly by their null
termination and the overall length of the extension. termination and the overall length of the extension.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| scope count |D|M| reserved | | Char Encoding | scope count |D|M| reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (if present) | | (if present) |
| Directory Agent address (16 octets) | | Directory Agent address (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| scope list ... | scope list ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 16 Type 16
Length variable Length (variable) The length of the Extension.
Character Encoding
The characters making up strings within the remainder of
the message may be encoded in any standardized encoding
(see section 2.1).
D If the 'D' bit is set, the Directory Agent address is D If the 'D' bit is set, the Directory Agent address is
present. present.
M If the 'M' bit is set, the Directory Agent address is M If the 'M' bit is set, the Directory Agent address is
the only one that may be used, and multicast methods for the only one that may be used, and multicast methods for
discovering Directory Agents MUST NOT be used. discovering Directory Agents MUST NOT be used.
scope count scope count
The number of scopes indicated by strings in the scope The number of scopes indicated by strings in the scope
skipping to change at page 10, line 17 skipping to change at page 12, line 42
Note that more than one Directory Agent extension may be present in Note that more than one Directory Agent extension may be present in
a DHCP message. Each such extension may have the same or different a DHCP message. Each such extension may have the same or different
lists of scopes. The client may request a Directory Agent with a lists of scopes. The client may request a Directory Agent with a
particular scope, by including the Directory Agent extension in a particular scope, by including the Directory Agent extension in a
DHCP Request message with no Directory Agent address included (the DHCP Request message with no Directory Agent address included (the
'D' bit set to zero), and the appropriate strings in the scope list. 'D' bit set to zero), and the appropriate strings in the scope list.
6.2. Service Scope Extension 6.2. Service Scope Extension
This extension indicates a scope that should be used by a Service 0 1 2 3
Agent (SA) [10], when responding to Service Request messages as 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
specified by the Service Location Protocol. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Char Encoding | scope ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Length Type 17
+-----+-----+-----+-----+-----+----- Length (variable) The length of the Extension.
| 17 | n | Scope ...
+-----+-----+-----+-----+-----+-----
Scope is a null-terminated ASCII string, of length 'n' octets Character Encoding
including the terminating null octet. The characters making up strings within the remainder of
the message may be encoded in any standardized encoding
(see section 2.1).
scope Scope is a zero-terminated string in the specified
character encoding, of length 'Length - 2' octets
including the terminating zero octet.
This extension indicates a scope that should be used by a Service
Agent (SA) [12], when responding to Service Request messages as
specified by the Service Location Protocol.
7. IP Layer Parameters per Interface 7. IP Layer Parameters per Interface
This section details the extensions that affect the operation of the This section details the extensions that affect the operation of the
IP layer on a per-interface basis. It is expected that a client can IP layer on a per-interface basis. It is expected that a client can
issue multiple requests, one per interface, in order to configure issue multiple requests, one per interface, in order to configure
interfaces with their specific parameters. interfaces with their specific parameters.
7.1. Static Route Extension 7.1. Static Route Extension
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination address 1 |
| (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router address 1 |
| (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination address 2 |
| (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router address 2 |
| (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|additional Destination/Router address pairs (32 octets each) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This extension specifies a list of static routes that the client This extension specifies a list of static routes that the client
should install in its routing cache. If multiple routes to the same should install in its routing cache. If multiple routes to the same
destination are specified, they are listed in the order in which the destination are specified, they are listed in the order in which the
client should make use of them. client should make use of them.
The routes consist of a list of IP address pairs. The first address The routes consist of a list of IP address pairs. The first address
is the destination address, and the second address is the router for is the destination address, and the second address is the router for
the destination. the destination.
Link-local addresses are illegal destinations for a static route. Link-local addresses are illegal destinations for a static route.
The type for this extension is 24. The minimum length of this The Type for this extension is 24. The minimum length of this
extension is 24, and the length MUST be a multiple of 16. extension is 24, and the length MUST be a multiple of 32.
Type Length Destination 1 Router 1
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 24 | n | d1 | d2 | ... | d16 | r1 | r2 | ... | r16 |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
Destination 2 Router 2
+-----+-----+-----+-----+-----+-----+-----+-----+---
| d1 | d2 | ... | d16 | r1 | r2 | ... | r16 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+---
8. TCP Parameters 8. TCP Parameters
This section lists the extensions that affect the operation of the This section lists the extensions that affect the operation of the
TCP layer on a per-interface basis. TCP layer on a per-interface basis.
8.1. TCP Keepalive Interval Extension 8.1. TCP Keepalive Interval Extension
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Keepalive Time Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This extension specifies the interval (in seconds) that the This extension specifies the interval (in seconds) that the
client TCP should wait before sending a keepalive message on a TCP client TCP should wait before sending a keepalive message on a TCP
connection. The time is specified as a 32-bit unsigned integer. connection. The time is specified as a 32-bit unsigned integer.
A value of zero indicates that the client should not generate A value of zero indicates that the client should not generate
keepalive messages on connections unless specifically requested by an keepalive messages on connections unless specifically requested by an
application. application.
The type for this extension is 32, and its length is 4. The Type for this extension is 32, and its length is 4.
Type Length Time
+-----+-----+-----+-----+-----+-----+-----+-----+
| 32 | 4 | t1 | t2 | t3 | t4 |
+-----+-----+-----+-----+-----+-----+-----+-----+
9. Vendor Specific Information 9. Vendor Specific Information
This extension is used by clients and servers to exchange vendor- This extension is used by clients and servers to exchange vendor-
specific information. The information is an opaque object of n specific information. The information is an opaque object of n
octets, presumably interpreted by vendor-specific code on the clients octets, presumably interpreted by vendor-specific code on the clients
and servers. The definition of this information is vendor specific. and servers. The definition of this information is vendor specific.
The vendor is indicated in the class-identifier extension. Servers The vendor is indicated in the class-identifier extension. Servers
not equipped to interpret the vendor-specific information sent by a not equipped to interpret the vendor-specific information sent by a
client MUST ignore it (although it may be reported). Clients which client MUST ignore it (although it may be reported). Clients which
skipping to change at page 12, line 24 skipping to change at page 15, line 27
within the encapsulated vendor-specific extensions field, but within the encapsulated vendor-specific extensions field, but
SHOULD conform to the type-length-value syntax defined in SHOULD conform to the type-length-value syntax defined in
section 2. section 2.
- Code 255 (END), if present, signifies the end of the - Code 255 (END), if present, signifies the end of the
encapsulated vendor extensions, not the end of the vendor encapsulated vendor extensions, not the end of the vendor
extensions field. If no code 255 is present, then the end of extensions field. If no code 255 is present, then the end of
the enclosing vendor-specific information field is taken as the enclosing vendor-specific information field is taken as
the end of the encapsulated vendor-specific extensions field. the end of the encapsulated vendor-specific extensions field.
The type for this extension is 40 and its minimum length is 1. The Type for this extension is 40 and its minimum length is 1.
Type Length Vendor-specific information 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
| 40 | n | i1 | i2 | ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-----+-----+-----+-----+-----+-----+--- | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-specific information ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
When encapsulated vendor-specific extensions are used, the When encapsulated vendor-specific extensions are used, the
information bytes 1-n have the following format: information bytes 1-n have the following format:
Type Len Data item Type Len Data item Type Type Len Data item Type Len Data item Type
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| T1 | n | d1 | d2 | ... | T2 | n | D1 | D2 | ... | ... | | T1 | n | d1 | d2 | ... | T2 | n | D1 | D2 | ... | ... |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
In other words, all vendor-specific extensions are encoded in
Type-Length-Value (TLV) format. More than one vendor-specific
extension can, therefore, be included in the same DHCP "Vendor
Specific Information" extension.
10. DHCPv6 Extensions 10. DHCPv6 Extensions
This section details the extensions that are specific to DHCPv6. This section details the extensions that are specific to DHCPv6.
10.1. Maximum DHCPv6 Message Size Extension 10.1. Maximum DHCPv6 Message Size Extension
This extension specifies the maximum size in octets of any DHCPv6 This extension specifies the maximum size in octets of any DHCPv6
message that the sender of the extension is willing to accept. The message that the sender of the extension is willing to accept. The
size is specified as an unsigned 16-bit integer. A client may use size is specified as an unsigned 16-bit integer. A client may use
the maximum DHCPv6 message size extension in DHCP Request messages, the maximum DHCPv6 message size extension in DHCP Request messages,
but SHOULD NOT use the extension in DHCP Solicit messages(see [3]), but SHOULD NOT use the extension in DHCP Solicit messages(see [3]),
and MUST NOT use the extension in other DHCP messages. and MUST NOT use the extension in other DHCP messages.
The type for this extension is 64, and its length is 2. The minimum 0 1 2 3
legal value is 1500. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max DHCPv6 Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Length Size The Type for this extension is 64, and its length is 2. The minimum
+-----+-----+-----+-----+-----+-----+ legal value is 1500.
| 64 | 2 | l1 | l2 |
+-----+-----+-----+-----+-----+-----+
10.2. Class Identifier 10.2. Class Identifier
This extension is used by a DHCP client to optionally identify the This extension is used by a DHCP client to optionally identify the
type or category of user or applications it represents. The class type or category of user or applications it represents.
identifier is a null-terminated NVT ASCII string, of length 'n'
octets including the terminating null octet, that represents the user
class of which the client is a member.
DHCP administrators may define specific user class identifiers to DHCP administrators may define specific user class identifiers to
convey information about a client's software configuration or about convey information about a client's software configuration or about
its user's preferences. For example, an identifier may specify its user's preferences. For example, an identifier may specify
that a particular DHCP client is a member of the class "accounting that a particular DHCP client is a member of the class "accounting
auditors", which have special service needs such as a particular auditors", which have special service needs such as a particular
database server. Alternatively, the identifier may encode the database server. Alternatively, the identifier may encode the
client's hardware configuration. client's hardware configuration.
Servers not equipped to interpret the user class specified by a Servers not equipped to interpret the user class specified by a
client MUST ignore it (although it may be reported). Otherwise, client MUST ignore it (although it may be reported). Otherwise,
servers SHOULD respond with the set of extensions corresponding to servers SHOULD respond with the set of extensions corresponding to
the user class specified by the client. Further, if the server the user class specified by the client. Further, if the server
responds with the set of extensions corresponding to the given user responds with the set of extensions corresponding to the given user
class, it MUST return this extension (with the given user class class, it MUST return this extension (with the given user class
value) to the client. value) to the client.
The type for this extension is 65, and its minimum length is 1. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Char Encoding | Class Identifier ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Length Class-Identifier The class identifier is a zero-terminated string of characters in the
+-----+-----+-----+-----+-----+-----+--- character set specified by the Char Encoding field (see section 2.1),
| 65 | n | i1 | i2 | ... of length 'n' octets including the terminating null octet. The class
+-----+-----+-----+-----+-----+-----+--- identifier represents the user class of which the client is a member.
10.3. Reconfigure Multicast Address 10.3. Reconfigure Multicast Address
A DHCPv6 server can instruct its clients to join a multicast group A DHCPv6 server can instruct its clients to join a multicast group
for the purposes of receiving DHCPv6 Reconfigure messages. This will for the purposes of receiving DHCPv6 Reconfigure messages. This will
allow a server to reconfigure all of its clients at once; such a allow a server to reconfigure all of its clients at once; such a
feature will be useful when renumbering becomes necessary. feature will be useful when renumbering becomes necessary.
Type Length IPv6 Multicast Address 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
| 66 | 16 | a1 | a2 | ... | a16 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-----+-----+-----+-----+-----+-----+-----+-----+ | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reconfigure Multicast Address |
| (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Type of the Reconfigure Multicast Address is 66, and the length
is 16.
10.4. Renumber DHCPv6 Server Address 10.4. Renumber DHCPv6 Server Address
A DHCPv6 server can instruct its clients to change their internal A DHCPv6 server can instruct its clients to change their internal
records to reflect the server's newly renumbered IPv6 address, by records to reflect the server's newly renumbered IPv6 address, by
using the "Renumber DHCPv6 Server Address" extension. This extension using the "Renumber DHCPv6 Server Address" extension. This extension
may be sent with the DHCP Reconfigure message, and thus can be may be sent with the DHCP Reconfigure message, and thus can be
multicast to all of the server's clients instead of being unicast to multicast to all of the server's clients instead of being unicast to
each one individually. each one individually.
Type Length New IPv6 Server Address 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
| 67 | 16 | a1 | a2 | ... | a16 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-----+-----+-----+-----+-----+-----+ | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New DHCPv6 Server Address |
| (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Type of the Renumber DHCPv6 Server Address is 67, and the length
is 16.
10.5. Client-Server Authentication Extension 10.5. Client-Server Authentication Extension
Exactly one Client-Server Authentication Extension MAY be present Exactly one Client-Server Authentication Extension MAY be present
in any DHCPv6 message transmitted between a client and server in any DHCPv6 message transmitted between a client and server (or
(or vice-versa). If present, it MUST be placed after every other vice-versa). If present, it MUST be the last extension, except
extension. possibly for the Pad extension 3.
Type Length Security Parameter ndx replay protect 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
| 80 | 12+x | sp1 | sp2 | sp3 | sp4 | rp1 |...| rp8 |Auth +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-----+------+-----+-----+-----+-----+-----+-----+-----+---+-----+---+- | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Security Parameters Index (SPI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Replay Protection |
| (8 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authenticator (variable length) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 84 Type 84
Length 4 for the SPI, plus 8 for the replay protection, plus the Length 4 for the SPI, plus 8 for the replay protection, plus the
number of bytes in the Authenticator. number of bytes in the Authenticator.
SPI A Security Parameters index [2] identifying a security SPI A Security Parameters index [2] identifying a security
context between a pair of nodes among the contexts context between a pair of nodes among the contexts
available in the security association defined between available in the security association defined between
the DHCPv6 client and server. SPI values 0 through 255 the DHCPv6 client and server. SPI values 0 through 255
are reserved and MUST NOT be used in any Client-Server are reserved and, if used, MUST conform to the security
Authentication Extension. context defined by that value as defined in the most
recent Assigned Numbers RFC (e.g., [5]).
Replay Protection Replay Protection
A 64-bit timestamp (in Network Time Protocol [5](NTP) A 64-bit timestamp (in Network Time Protocol [7](NTP)
format) (see section 11.1). format) (see section 11.1).
Authenticator Authenticator
(variable length) (See Section 11.2.) (variable length) (See Section 11.2.)
This authentication extension remedies the inability of IPsec to This authentication extension remedies the inability of IPsec to
provide for non end-to-end authentication, since authentication is provide for non end-to-end authentication, since authentication is
needed even when the client needs has no valid IPv6 address. The needed even when the client needs has no valid IPv6 address. The
extension can be originated by either the DHCPv6 Client or DHCPv6 extension can be originated by either the DHCPv6 Client or DHCPv6
server to authenticate the rest of the data in the DHCPv6 message. server to authenticate the rest of the data in the DHCPv6 message.
The default authentication algorithm is defined in section 11.2.
11. Security Considerations 11. Security Considerations
There is an urgent need to define some security protocol for use There is an urgent need to define some security protocol for use
with DHCPv6, since otherwise malicious parties could create numerous with DHCPv6, since otherwise malicious parties could create numerous
denial-of-service style attacks based on depleting available server denial-of-service style attacks based on depleting available server
resources or providing corrupted or infected data to unsuspecting resources or providing corrupted or infected data to unsuspecting
clients. The following sections discuss aspects of security relevant clients. The following sections discuss aspects of security relevant
for users of the Client-Server Authentication extension 10.5. for users of the Client-Server Authentication extension 10.5.
11.1. Replay Protection 11.1. Replay Protection
A 64-bit timestamp, in Network Time Protocol [5](NTP) format, is A 64-bit timestamp, in Network Time Protocol [7](NTP) format, is
used to protect against replay of previous authenticated messages used to protect against replay of previous authenticated messages
by malicious agents. The NTP timestamp value used in the extension by malicious agents. The NTP timestamp value used in the extension
MUST be chosen, and verified, to be larger than values used by the MUST be chosen, and verified, to be larger than values used by the
originator in previous Client-Server Authentication extensions. originator in previous Client-Server Authentication extensions.
On the other hand, the timestamp value MUST also be chosen (and On the other hand, the timestamp value MUST also be chosen (and
verified) to be no greater than one year more than the last known verified) to be no greater than one year more than the last known
value (if any) used by the originator. value (if any) used by the originator.
11.2. Default Authentication Algorithm 11.2. Default Authentication Algorithm
The default authentication algorithm uses keyed-MD5 [9] in The default authentication algorithm is HMAC [6], using
"prefix+suffix" mode to compute a 128-bit "message digest" of the keyed-MD5 [10]. Given a secret key K, and "data" the information to
registration message. The default authenticator is a 128-bit value be authenticated, HMAC_result is computed as follows:
computed as the MD5 checksum over the the following stream of bytes:
- the shared secret defined by the security association between 1. opad := 0x36363636363636363636363636363636 (128 bits)
the client and server and by the SPI value specified in the
Authentication Extension, followed by
- all previous fields in the DHCPv6 message and extensions, 2. ipad := 0x5C5C5C5C5C5C5C5C5C5C5C5C5C5C5C5C (128 bits)
followed by
- the shared secret again. 3. zero_extended_key := K extended by zeroes to be 128 bits long
4. opadded_key := zero_extended_key XOR opad
5. ipadded_key := zero_extended_key XOR ipad
6. HMAC_result := MD5 (opadded_key , MD5 (ipadded_key, data))
The key K is the shared secret defined by the security association
between the client and server and by the SPI value specified in
the Authentication Extension. The "data" is the stream of bytes
in all previous fields in the DHCPv6 message and extensions. The
authenticator is the 128-bit value HMAC_result.
12. New Extensions 12. New Extensions
Additional generic data fields may be registered by contacting: Additional extensions may be registered by contacting:
Internet Assigned Numbers Authority (IANA) Internet Assigned Numbers Authority (IANA)
USC/Information Sciences Institute USC/Information Sciences Institute
4676 Admiralty Way 4676 Admiralty Way
Marina del Rey, California 90292-6695 Marina del Rey, California 90292-6695
or by email as: iana@isi.edu or by email as: iana@isi.edu
Implementation specific use of undefined generic types (including Implementation specific use of undefined extensions (including those
those in the range 72-127) may conflict with other implementations, in the range 85-32767) may conflict with other implementations, and
and registration is required. registration is required.
DISCUSSION: Need to read Ralph's new draft and incorporate
those ideas here.
13. Acknowledgements 13. Acknowledgements
Thanks to Jim Bound for his frequent review, helpful suggestions, Thanks to Jim Bound for his frequent review, helpful suggestions,
and design assistance. The original form of this internet draft was and design assistance. The original form of this internet draft was
copied directly from RFC1533 [1], written by Steve Alexander and copied directly from RFC1533 [1], written by Steve Alexander and
Ralph Droms, to whom thanks are again due. Ralph Droms, to whom thanks are again due.
References References
[1] S. Alexander and R. Droms. DHCP Options and BOOTP Vendor [1] S. Alexander and R. Droms. DHCP Options and BOOTP Vendor
Extensions. RFC 1533, October 1993. Extensions. RFC 1533, October 1993.
[2] R. Atkinson. IP Authentication Header. RFC 1826, August 1995. [2] R. Atkinson. IP Authentication Header. RFC 1826, August 1995.
[3] J. Bound and C. Perkins. Dynamic Host Configuration Protocol [3] J. Bound and C. Perkins. Dynamic Host Configuration Protocol
for IPv6. draft-ietf-dhc-dhcpv6-05.txt -- work in progress, for IPv6. draft-ietf-dhc-dhcpv6-09.txt, February 1997. (work
June 1996. in progress).
[4] S. Deering and R. Hinden. Internet Protocol, Version 6 (IPv6) [4] S. Deering and R. Hinden. Internet Protocol, Version 6 (IPv6)
Specification. RFC 1883, December 1995. Specification. RFC 1883, December 1995.
[5] David L. Mills. Network Time Protocol (Version 3): [5] Stan Hanks, Tony Li, Dino Farinacci, and Paul Traina. Generic
Routing Encapsulation (GRE). RFC 1701, October 1994.
[6] H. Krawczyk, M. Bellare, and R. Cannetti. HMAC: Keyed-Hashing
for Message Authentication. RFC 2104, February 1997.
[7] David L. Mills. Network Time Protocol (Version 3):
Specification, Implementation and Analysis. RFC 1305, March Specification, Implementation and Analysis. RFC 1305, March
1992. 1992.
[6] P. Mockapetris. DOMAIN NAMES - IMPLEMENTATION AND [8] P. Mockapetris. DOMAIN NAMES - IMPLEMENTATION AND
SPECIFICATION. RFC 1035, November 1987. SPECIFICATION. RFC 1035, November 1987.
[7] T. Narten, E. Nordmark, and W. Simpson. Neighbor Discovery for [9] J. Reynolds. BOOTP Vendor Information Extensions. RFC 1497,
IP Version 6 (IPv6). draft-ietf-ipngwg-discovery-06.txt -- work
in progress, March 1996.
[8] J. Reynolds. BOOTP Vendor Information Extensions. RFC 1497,
August 1993. August 1993.
[9] Ronald L. Rivest. The MD5 Message-Digest Algorithm. RFC 1321, [10] Ronald L. Rivest. The MD5 Message-Digest Algorithm. RFC 1321,
April 1992. April 1992.
[10] J. Veizades, E. Guttman, C. Perkins, and S. Kaplan. Service [11] S. Thomson and T. Narten. IPv6 stateless address
Location Protocol. draft-ietf-svrloc-protocol-14.txt - work in autoconfiguration. RFC 1971, August 1996.
progress, June 1996.
[12] J. Veizades, E. Guttman, C. Perkins, and S. Kaplan. Service
Location Protocol. draft-ietf-svrloc-protocol-15.txt, November
1996. (work in progress).
[13] P. Vixie, S. Thomson, Y. Rekhter, and J. Bound.
Dynamic Updates in the Domain Name System (DNS).
draft-ietf-dnsind-dynDNS-11.txt, November 1996. (work
in progress).
Chair's Addresses Chair's Addresses
The working group can be contacted via the current chair: The working group can be contacted via the current chair:
Ralph Droms Ralph Droms
Computer Science Department Computer Science Department
323 Dana Engineering 323 Dana Engineering
Bucknell University Bucknell University
Lewisburg, PA 17837 Lewisburg, PA 17837
Phone: (717) 524-1145 Phone: (717) 524-1145
EMail: droms@bucknell.edu EMail: droms@bucknell.edu
Author's Address Author's Address
Questions about this memo can be directed to: Questions about this memo can be directed to:
Charles Perkins Charles Perkins
Room H3-D34 Mail Stop UPAL01-550
T. J. Watson Research Center Netcentricity Group
IBM Corporation Sun Microsystems, Inc.
30 Saw Mill River Rd. 2550 Garcia Avenue
Hawthorne, NY 10532 Mountain View, CA 94043
Work: +1-914-784-7350 Work: +1-415-336-7153
Fax: +1-914-784-6205 Fax: +1-415-336-0673
E-mail: perk@watson.ibm.com E-mail: cperkins@corp.sun.com
 End of changes. 

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