Internet Engineering Task Force S. Kumar
Internet-Draft Samsung India Software Operations
Expires: September 4, 2006 L. Morand
France Telecom R&D
A. Yegin
Samsung Advanced Institute of
Technology
S. Madanapalli
Samsung India Software Operations
March 3, 2006
DHCP option for PANA Authentication Agents
draft-ietf-dhc-paa-option-01.txt
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document defines new Dynamic Host Configuration Protocol options
that contain a list of domain names or IP addresses that can be
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mapped to one or more of PANA Authentication Agents (PAA). This is
one of the many methods that a PANA Client (PaC) can use to locate
PANA Authentication Agents (PAA).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. DHCP specification dependency . . . . . . . . . . . . . . . . 6
5. PANA Authentication Agent DHCPv4 Option . . . . . . . . . . . 7
5.1. PANA Authentication Agent Domain Name List . . . . . . . . 7
5.2. PANA Authentication Agent IPv4 Address List . . . . . . . 8
6. PANA Authentication Agent DHCPv6 Options . . . . . . . . . . . 10
6.1. PANA Authentication Agent Domain Name List . . . . . . . . 10
6.2. PANA Authentication Agent IPv6 Address List . . . . . . . 11
7. Client Operation . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. DHCPv4 Client . . . . . . . . . . . . . . . . . . . . . . 13
7.2. DHCPv6 Client . . . . . . . . . . . . . . . . . . . . . . 13
8. DHCP Server Operation . . . . . . . . . . . . . . . . . . . . 14
8.1. DHCPv4 Server . . . . . . . . . . . . . . . . . . . . . . 14
8.2. DHCPv6 Server . . . . . . . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. Normative References . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18
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1. Introduction
The Protocol for carrying Authentication for Network Access (PANA)
[1] defines a new Extensible Authentication Protocol (EAP) lower
layer that uses IP between the protocol end points.
The PANA protocol is run between a PANA Client (PaC) and a PANA
Authentication Agent (PAA) in order to perform authentication and
authorization for the network access service.
This document specifies DHCPv4 option [2] and DHCPv6 option [7] that
allow PANA client (PaC) to discover PANA Authentication Agents (PAA).
This is one of the many methods for locating PAAs: manual
configuration is an example of another one.
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2. Terminology
This document uses the PANA terminology defined in [1].
This document uses the DHCP terminology defined in [2] , [3] and[7].
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3. Requirements
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [4].
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4. DHCP specification dependency
This document describes new options for DHCPv4 and DHCPv6 for
obtaining a list of domain names or IP addresses to locate a PANA
Authentication Agent.
This document should be read in conjunction with the DHCPv4
specifications [2] , [3] and DHCPv6 specification [7].
Definitions for terms and acronyms not specifically defined in this
document are defined in [2] , [3] and DHCPv6 specification [7].
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5. PANA Authentication Agent DHCPv4 Option
This document defines a DHCPv4 option that carries either a 32-bit
(binary) IPv4 address list or, preferably, a domain name list to be
used by the PANA client to locate a PANA authentication Agent.
The option has two encodings, specified by the encoding byte ('enc')
that follows the code byte. If the encoding byte has the value 0, it
is followed by a list of domain names, as described below (Section
5.1). If the encoding byte has the value 1, it is followed by one or
more IPv4 addresses (Section 5.2). All implementations MUST support
both encodings. The 'option-length' field indicates the total number
of octets in the option following the 'option-length' field,
including the encoding byte.
5.1. PANA Authentication Agent Domain Name List
If the 'enc' byte has a value of 0, the encoding byte is followed by
a sequence of labels, encoded according to Section 3.1 of RFC 1035
[5], quoted below:
Domain names in messages are expressed in terms of a sequence of
labels. Each label is represented as a one octet length field
followed by that number of octets. Since every domain name ends
with the null label of the root, a domain name is terminated by a
length byte of zero. The high order two bits of every length
octet must be zero, and the remaining six bits of the length field
limit the label to 63 octets or less. To simplify
implementations, the total length of a domain name (i.e., label
octets and label length octets) is restricted to 255 octets or
less.
RFC 1035 encoding was chosen to accommodate future internationalized
domain name mechanisms.
The option MAY contain multiple domain names, but these SHOULD refer
to different NAPTR records, rather than different A records. Domain
names MUST be listed in order of preference.
Use of multiple domain names is not meant to replace NAPTR and SRV
records, but rather to allow a single DHCPv4 server to indicate
multiple PANA Authentication Agents available in the same access
network.
Clients MUST support compression according to the encoding in Section
4.1.4 of [5].
If the length of the domain list exceeds the maximum permissible
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within a single option (254 octets), then the domain list MUST be
represented in the DHCP message as specified in [6].
The DHCPv4 option for this encoding has the format shown in Fig. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-length | enc | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PAA Domain Name List |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: DHCPv4 option for PAA Domain Name List
option-code: OPTION_PANA_AGENT(TBD)
option-length: Number of octets following the 'option-length'
field, including the encoding byte, in octets; variable.
enc: Encoding byte set to 0
PAA Domain Name List: The domain names of the PANA Authentication
Agents for the client to use. The domain names are encoded
according to Section 3.1 of RFC 1035 [5].
5.2. PANA Authentication Agent IPv4 Address List
If the 'enc' byte has a value of 1, the encoding byte is followed by
a list of IPv4 addresses indicating one or more PANA Authentication
Agents available to the PANA client. PAAs MUST be listed in order of
preference.
The DHCPv4 option for this encoding has the format shown in Fig. 2.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-length | enc | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PAA IP Address | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DHCPv4 option for PAA IPv4 Address List
option-code: OPTION_PANA_AGENT(TBD)
option-length: Number of octets following the 'option-length'
field, including the encoding byte in octets; Must be a multiple
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of 4 plus one.
enc: Encoding byte set to 1
PAA IP Address: IPv4 address of a PAA for the PaC to use. The
PAAs are listed in the order of preference for use by the PaC.
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6. PANA Authentication Agent DHCPv6 Options
This section defines two DHCPv6 options that describe a PANA
Authentication Agent: one carries a list of domain names (Section
6.1), the other a list of 128-bit (binary) IPv6 addresses (Section
6.2).
Since DHCPv6 does not suffer from a shortage of option codes, we
avoid the encoding byte found in the DHCPv4 option for PAA
(Section 5). This makes the option shorter, easier to parse,
simplifies appropriate word alignment for the numeric addresses
and allows the DHCPv6 client to request either numeric or domain
name options using the "option request option" (ORO).
An implementation implementing this specification MUST support both
options.
6.1. PANA Authentication Agent Domain Name List
The option length is followed by a sequence of labels, encoded
according to Section 3.1 of RFC 1035 [3],quoted below:
"Domain names in messages are expressed in terms of a sequence of
labels. Each label is represented as a one octet length field
followed by that number of octets. Since every domain name ends
with the null label of the root, a domain name is terminated by a
length byte of zero. The high order two bits of every length
octet must be zero, and the remaining six bits of the length field
limit the label to 63 octets or less. To simplify
implementations, the total length of a domain name (i.e., label
octets and label length octets) is restricted to 255 octets or
less."
RFC 1035 encoding was chosen to accommodate future internationalized
domain name mechanisms.
The option MAY contain multiple domain names, but these SHOULD refer
to different NAPTR records, rather than different A records. Domain
names MUST be listed in order of preference. Use of multiple domain
names is not meant to replace NAPTR or SRV records, but rather to
allow a single DHCP server to indicate PANA Authentication Agents
operated by multiple providers.
The DHCPv6 option for PANA Authentication Agent Domain Name List has
the format shown in Fig. 3
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PAA Domain Name List |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: DHCPv6 option for PAA Domain Name List
option-code: OPTION_PANA_AGENT_D (TBD).
option-length: Length of the 'PAA Domain Name List' field in
octets; variable.
PAA Domain Name List: The domain names of the PANA Authentication
Agents (PAA) for the client to use. The domain names are encoded
as specified in Section 8 ("Representation and use of domain
names") of the DHCPv6 specification [7].
6.2. PANA Authentication Agent IPv6 Address List
This option specifies a list of IPv6 addresses indicating PANA
Authentication Agent available to the client.PANA Authentication
Agents MUST be listed in order of preference.
The DHCPv6 option for PAA IPv6 Address List has the format shown in
Fig. 4.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ PAA IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ PAA IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: DHCPv6 option for PAA IPv6 Address List
option-code: OPTION_PANA_AGENT_A (TBD).
option-length: Length of the 'options' field in octets; must be a
multiple of 16.
PANA IP Address: IPv6 address of a PAA for the client to use.The
PAAs are listed in the order of preference for use by the client.
If a client receives both the PAA Domain Name List and PAA IPv6
Address List options, it SHOULD use first the PAA Domain Name List
option. The client MUST try the records in the order listed. The
client only resolves the subsequent domain names if attempts to
contact the first one failed or denote a domain administratively
prohibited by client policy. Only if no PANA Authentication Agent in
the Domain Name List can be resolved or reached, the client MAY use
the PAA IPv6 Address List option.
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7. Client Operation
7.1. DHCPv4 Client
The client requests PAA DHCPv4 Option in a Parameter Request List as
described in [2] and [3].
If the PAA DHCPv4 option provided in response by the DHCPv4 server
contains multiple domain names, the client MUST try the records in
the order listed. The client only resolves the subsequent domain
names if attempts to contact the first one failed or denote a domain
administratively prohibited by client policy.
If the PAA DHCPv4 option provided in response by the DHCPv4 server
contains multiple IP addresses, the client MUST try the records in
the order listed.
7.2. DHCPv6 Client
A DHCPv6 client may request either or both PAA domain name list and
PAA IPv6 address list options in an Options Request Option (ORO) as
described in the DHCPv6 specification [7].
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8. DHCP Server Operation
8.1. DHCPv4 Server
If a DHCPv4 server is configured with both PAA domain name list and
PAA IP address list, the DHCPv4 server should responds to the request
with the domain name list to be used by the PANA client.
A DHCP server MUST NOT mix the two list types (domain names and IPv4
address) in the same DHCPv4 message, even if it sends two different
instances of the same option.
8.2. DHCPv6 Server
A DHCPv6 server MAY send a DHCPv6 client one or both of the PAA
Domain Name List and PAA IPv6 Address List options.
If a DHCPv6 client requests both options in an ORO and the server is
configured for both, the DHCPv6 server MAY send a DHCPv6 client only
one of these options and that option SHOULD be the PAA Domain Name
List.
If a DHCPv6 client requests only the PAA IPv6 Address List option and
the DHCPv6 server is configured with both options, the server MUST
send a DHCPv6 client the PAA IPv6 Address List option and MAY send a
the PAA Domain Name List (see [7]).
The following table summarizes the DHCPv6 server's responses:
Client sends in ORO Domain Name List IPv6 Address List
-----------------------------------------------------------------
Neither option SHOULD MAY
PAA Domain Name List SHOULD MAY
PAA IPv6 Address List MAY MUST
Both options SHOULD MAY
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9. Security Considerations
The security considerations in [2] , [3] and [7] apply. If an
adversary manages to modify the response from a DHCP server or insert
its own response, a PANA Client could be led to contact a rogue PANA
Agent, possibly one that then intercepts call requests or denies
service.
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10. IANA Considerations
IANA assignment for the following DHCPv4 option code is needed.
Option Name Value
----------------------------------
OPTION_PAA_AGENT TBD
The following option codes for PANA Authentication Agent DHCPv6
options must be assigned by IANA.
Option Name Value Described in
-----------------------------------------------------
OPTION_PAA_AGENT_D TBD Section 6.1
OPTION_PAA_AGENT_A TBD Section 6.2
11. Normative References
[1] Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A. Yegin,
"Protocol for Carrying Authentication for Network Access (PANA),
draft-ietf-pana-pana-08 (work in progress)", Novemeber 2005.
[2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[3] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[5] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[6] Lemon, T. and S. Cheshire, "Encoding Long Options in the Dynamic
Host Configuration Protocol (DHCPv4)", RFC 3396, November 2002.
[7] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 3315, July 2003.
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Authors' Addresses
Suraj Kumar
Samsung India Software Operations
No. 66/1, BAGMANE TECH PARK, C V RAMAN NAGAR
Bangalore
India
Phone: +91 80 41819999
Email: suraj.kumar@samsung.com
Lionel Morand
France Telecom R&D
38-40 rue du general Leclerc
Issy-les-Moulineaux, F-92130
France
Phone: +33 1 4529 6257
Email: lionel.morand@francetelecom.com
Alper E. Yegin
Samsung Advanced Institute of Technology
75 West Plumeria Drive
San Jose, CA 95134
USA
Phone: +1 408 544 5656
Email: alper.yegin@samsung.com
Syam Madanapalli
Samsung India Software Operations
No. 66/1, BAGMANE TECH PARK, C V RAMAN NAGAR
Bangalore
India
Phone: +91 80 41819999
Email: syam@samsung.com
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