Network Working Group L. Morand (Ed.)
Internet-Draft France Telecom R&D
Expires: September 23, 2006 S. Kumar
Samsung India Software Operations
A. Yegin
Samsung Advanced Institute of
Technology
S. Madanapalli
Samsung India Software Operations
March 22, 2006
DHCP options for PANA Authentication Agents
draft-ietf-dhc-paa-option-02
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This Internet-Draft will expire on September 23, 2006.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document defines new DHCPv4 and DHCPv6 options that contain a
list of domain names or IP addresses that can be mapped to one or
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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).
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. DHCP Specification Dependency . . . . . . . . . . . . . . . . 3
5. PANA Authentication Agent DHCPv4 Option . . . . . . . . . . . 4
5.1. PANA Authentication Agent Option . . . . . . . . . . . . . 4
5.2. PANA Authentication Agent Domain Name List Sub-option . . 5
5.3. PANA Authentication Agent IPv4 Address List Sub-option . . 5
6. PANA Authentication Agent DHCPv6 Options . . . . . . . . . . . 5
6.1. PANA Authentication Agent Domain Name List . . . . . . . . 6
6.2. PANA Authentication Agent IPv6 Address List . . . . . . . 7
7. Client Operation . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. DHCPv4 Client . . . . . . . . . . . . . . . . . . . . . . 8
7.2. DHCPv6 Client . . . . . . . . . . . . . . . . . . . . . . 8
8. DHCP Server Operation . . . . . . . . . . . . . . . . . . . . 9
8.1. DHCPv4 Server . . . . . . . . . . . . . . . . . . . . . . 9
8.2. DHCPv6 Server . . . . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Security Considerations . . . . . . . . . . . . . . . . . . . 10
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
12. Normative References . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Introduction
The Protocol for carrying Authentication for Network Access (PANA)
[I-D.ietf-pana-pana] 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 [RFC2131] and DHCPv6 [RFC3315] options
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.
2. Terminology
This document uses the PANA terminology defined in [I-D.ietf-pana-
pana].
This document uses the DHCP terminology defined in [RFC2131],
[RFC2132] and [RFC3315].
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 [RFC2119].
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 [RFC2131], [RFC2132] and DHCPv6 specification
[RFC3315].
Definitions for terms and acronyms not specifically defined in this
document are defined in [RFC2131], [RFC2132] and [RFC3315].
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5. PANA Authentication Agent DHCPv4 Option
This document defines a new DHCPv4 option that carries either a
domain name list or a 32-bit (binary) IPv4 address list to be used by
the PANA client to locate PANA authentication Agents.
5.1. PANA Authentication Agent Option
The PANA Authentication Agent Option is specified as a "container"
option that conveys one or more "sub-options" providing information
to locate PANA Authentication Agents. The format of the PANA
Authentication Agent Option is shown in Fig. 1.
Code Len PAA Information Field
+------+------+------+------+------+------+--...-+------+
| TDB | N | i1 | i2 | i3 | i4 | | iN |
+------+------+------+------+------+------+--...-+------+
Figure 1: DHCPv4 option for PANA Authentication Agent
The length N gives the total number of octets in the PAA Information
Field. The PAA Information field consists of a sequence of SubOpt/
Length/Value tuples for each sub-option, encoded as shown in the Fig.
2.
SubOpt Len Sub-option Value
+------+------+------+------+------+------+--...-+------+
| TBD | N | s1 | s2 | s3 | s4 | | sN |
+------+------+------+------+------+------+--...-+------+
Figure 2: Encoding of of PAA Information field
No "pad" sub-option is defined, and the PAA Information field SHALL
NOT be terminated with a 255 sub-option.
The length N of the PANA Authentication Agent Option SHALL include
all octets of the sub-option code/length/value tuples.
Since at least one sub-option MUST be defined, the minimum PANA
Authentication Agent Option length is two (2).
The length N of the sub-options SHALL be the number of octets in only
that sub-option's value field. A sub-option length MAY be zero. The
sub-options need not appear in sub-option code order.
The initial assignment of PANA Authentication Agent Sub-options is as
follows:
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PAA Sub-option Sub-Option Description
Code
--------------- --------------------------------
1 PAA Domain Name List Sub-option
2 PAA IPv4 Address List Sub-option
An implementation implementing this specification MUST support both
sub-options.
5.2. PANA Authentication Agent Domain Name List Sub-option
This sub-option carries a list of domain names indicating one or more
PANA Authentication Agents available to the PANA client.
This sub-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.
The domain names are encoded according to Section 3.1 of [RFC1035].
Clients MUST support compression according to the encoding in Section
4.1.4 of [RFC1035].
If the length of the domain list exceeds the maximum permissible
within a single option (254 octets), then the domain list MUST be
represented in the DHCP message as specified in [RFC3396].
5.3. PANA Authentication Agent IPv4 Address List Sub-option
This sub-option carries 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 for use by the PaC.
The number of octets following the sub-option length field MUST be a
multiple of four (4).
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, the other a
list of 128-bit (binary) IPv6 addresses.
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An implementation implementing this specification MUST support both
options.
6.1. PANA Authentication Agent Domain Name List
This option carries a list of domain names indicating one or more
PANA Authentication Agents available to the PANA client.
The option length is followed by a sequence of labels, encoded
according to Section 3.1 of [RFC1035],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."
[RFC1035] 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.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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;
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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 [RFC3315].
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.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ 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 sixteen (16).
PANA IP Address: IPv6 address of a PAA for the client to use. The
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PAAs are listed in the order of preference for use by the client.
7. Client Operation
7.1. DHCPv4 Client
The client requests PAA Option in a Parameter Request List as
described in [RFC2131] and [RFC2132].
If a client receives in response a PAA Domain Name List Sub-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.
If a client receives in response a PAA IPv4 Address List Sub-option,
the client MUST try the records in the order listed.
If a client receives both the PAA Domain Name List Sub-option and PAA
IPv4 Address List Sub-options, it SHOULD use first the PAA Domain
Name List Sub-option. The client MUST try the records in the order
listed. The client only resolves the subsequent domain name 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 IPv4 Address List Sub-option.
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 [RFC3315].
If a client receives in response a PAA Domain Name List Sub-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.
If a client receives in response a PAA IPv6 Address List Sub-option,
the client MUST try the records in the order listed.
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
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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.
8. DHCP Server Operation
8.1. DHCPv4 Server
If 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. However the DHCPv4 server MAY
send a DHCPv4 client both of the PAA Domain Name List and PAA IPv4
Address List Sub-options.
8.2. DHCPv6 Server
If configured with both PAA domain name list and PAA IP address list,
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 [RFC3315]).
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
9. IANA Considerations
The following DHCPv4 option code for PANA Authentication Agent option
must be assigned by IANA:
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Option Name Value
--------------------------------------------------------
PAA Option TBD
IANA is required to maintain a new number space of "DHCP PAA Sub-
options", located in the BOOTP-DHCP Parameters Registry. The initial
sub-options are described in section 5 of this document with the
following assignment:
PAA Sub-option Sub-Option Description Described in
Code
----------------------------------------------------------------
1 PAA Domain Name List Sub-option Section 5.1
2 PAA IPv4 Address List Sub-option Section 5.2
IANA assigns future DHCP PAA Sub-options with a "IETF Consensus"
policy as described in [RFC2434]. Future proposed sub-options are to
be referenced symbolically in the Internet-Drafts that describe them,
and shall be assigned numeric codes by IANA when approved for
publication as an RFC.
The following DHCPv6 option codes for PANA Authentication Agent
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
10. Security Considerations
The security considerations in [RFC2131], [RFC2132] and [RFC3315]
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.
11. Acknowledgements
12. Normative References
[I-D.ietf-pana-pana]
Forsberg, D., "Protocol for Carrying Authentication for
Network Access (PANA)", draft-ietf-pana-pana-11 (work in
progress), March 2006.
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[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
November 2002.
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Authors' Addresses
Lionel Morand
France Telecom R&D
38-40 rue du general Leclerc
92794 Issy-Les-Moulineaux Cedex 9
France
Phone: +33 1 45296257
Email: lionel.morand@francetelecom.com
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
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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