MIPSHOP WG Gabor Bajko
Internet Draft Nokia
Intended Status: Standards Track Subir Das
Expires: May 18, 2008 Telcordia
November 18, 2007
Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for
Mobility Server (MoS) discovery
draft-bajko-mos-dhcp-options-01
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document defines a number of Dynamic Host Configuration
Protocol (DHCP-for-IPv4 and DHCP-for-IPv6) options that contain a
list of domain names or IP addresses that can be mapped to servers
providing IEEE 802.21 type of Mobility Services. These Mobility
Services are used to assist an MN in handover preparation (network
discovery) and handover decision (network selection). The services
addressed by this document are the Media Independent Handover
Services defined in [1].
Conventions used in this document
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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 [1].
Terminology and abbreviations used in this document
Mobility Services: comprises of a set of different services provided
by the network to mobile nodes to facilitate handover preparation
and handover decision.
Mobility Server: a network node providing Mobility Support Services.
MIH: Media Independent Handover, as defined in [1].
MIH Service: IS, ES or CS type of service, as defined in [1].
Table of Content
1. Introduction ...................................................2
2. DHCPv4 Options for MoS Discovery................................3
2.1 Domain Name List .........................................4
2.2 IPv4 Address List ........................................5
3. DHCPv6 Options for MoS Discovery................................5
3.1 MoS Identifier Option.....................................6
3.2 IPv6 Relay Agent MoS Option...............................7
3.3 MoS Information Option 8
4. Option Usage 10
4.1 Usage of DHCPv4 Options for MoS Discovery 10
4.2 Usage of DHCPv6 Options for MoS Discovery 11
5. Security Considerations .......................................11
6. IANA Considerations ...........................................11
7. Acknowledgements ..............................................12
8. Normative References ..........................................12
9. Informative References ........................................12
10. Author's Addresses ...........................................12
1. Introduction
IEEE 802.21 [1] defines three distinct service types to facilitate
link layer handovers across heterogeneous technologies:
a) Information Services (IS)
IS provides a unified framework to the higher layer entities
across the heterogeneous network environment to facilitate discovery
and selection of multiple types of networks existing within a
geographical area, with the objective to help the higher layer
mobility protocols to acquire a global view of the heterogeneous
networks and perform seamless handover across these networks.
b) Event Services (ES)
Events may indicate changes in state and transmission behavior
of the physical, data link and logical link layers, or predict state
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changes of these layers. The Event Service may also be used to
indicate management actions or command status on the part of the
network or some management entity.
c) Command Services (CS)
The command service enables higher layers to control the
physical, data link, and logical link layers. The higher layers may
control the reconfiguration or selection of an appropriate link
through a set of handover commands.
In IEEE terminology these services are called Media Independent
Handover (MIH) services.
While these services may be co-located, the different pattern and
type of information they provide does not necessitate the co-
location.
An MN may make use of any of these MIH service types separately or
any combination of them.
It is anticipated that a Mobility Server will not necessarily host
all three of these MIH services together, thus there is a need to
discover the MIH services types separately.
This document defines three dhcp options for DHCPv4 and DHCPv6, one
for each of the services defined in [1], namely IS, ES and CS. The
options would allow an MN to locate a Mobility Server which hosts
the desired MIH service type (IS, ES or CS) the MN is looking for.
This is one of the possible solutions for locating a server
providing Mobility Services; manual configuration is an example of
another.
2. DHCPv4 Options for MoS Discovery
This section describes three options for DHCPv4.
The DHCPv4 options for MoS discovery carry either a 32-bit (binary)
IPv4 address or, preferably, a DNS [RFC1035] fully-qualified domain
name to be used by the MN to locate a server hosting either an IS,
an ES or a CS service.
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| Length | enc | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Mos Server (domain name or IP address list)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option code: IPv4 MoS option codes assigned by IANA (tbd), separate
ones for IS (IPv4-IS), for ES (IPv4-ES) and CS (IPv4-CS).
Length: indicates the total number of octets in the option following
the 'Length' field, including the encoding byte
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enc: one byte indicating the encoding type of the next field
The options have 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 2.1). If the encoding byte has the value 1, it is
followed by one or more IPv4 addresses (Section 2.2). All
implementations MUST support both encodings. The 'Length' field
indicates the total number of octets in the option following the
'Length' field, including the encoding byte.
A DHCP server MUST NOT mix the two encodings in the same DHCP
message, even if it sends two different instances of the same
option. Attempts to do so would result in incorrect client behavior
as DHCP processing rules call for the concatenation of multiple
instances of an option into a single option prior to processing the
option [7].
The code for the MIH IS option is XXX. The code for the MIH ES
option is YYY. The code for the MIH CS option is ZZZ.
2.1 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 [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 minimum length for this encoding is 3.
The option MAY contain multiple domain names, but these SHOULD refer
to different NAPTR records, rather than different A records. The
client MUST try the records in the order listed, applying the
mechanism described in [8] for each. The client only resolves the
subsequent domain names if attempts to contact the first one failed
or yielded no common transport protocols between the MN and the
server.
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Use of multiple domain names is not meant to replace NAPTR and SRV
records, but rather to allow a single DHCP server to indicate MIH
servers operated by multiple providers.
Clients MUST support compression according to the encoding in
Section 4.1.4 of "Domain Names - Implementation And Specification"
[RFC1035].
Since the domain names are supposed to be different domains,
compression will likely have little effect, however.
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 [7].
The DHCP option for this encoding has the following format:
Code Len enc DNS name of MoS server
+-----+-----+-----+-----+-----+-----+-----+-----+--
| XXX | n | 0 | s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+--
As an example, consider the case where the server wants to offer two
MIH IS servers, "example.com" and "example.net". These would be
encoded as follows:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|XXX|27 | 0 | 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'c'|'o'|'m'| 0 |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'n'|'e'|'t'| 0 |
+---+---+---+---+---+---+---+---+---+---+---+---+---+
2.2 IPv4 Address List
If the 'enc' byte has a value of 1, the encoding byte is followed by
a list of IPv4 addresses indicating appropriate MIH servers
available to the MN. Servers MUST be listed in order of preference.
Its minimum length is 5, and the length MUST be a multiple of 4 plus
one. The DHCP option for this encoding has the following format:
Code Len enc IPv4 Address 1 IPv4 Address 2
+-----+-----+-----+-----+-----+-----+-----+-----+--
| XXX | n | 1 | a1 | a2 | a3 | a4 | a1 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+--
3. DHCPv6 Options for MoS discovery
3.1 MoS Identifier Option
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This option is included in the Information-request message and used
to request an MoS-type information from a given network by the
mobile node from the DHCP server.
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 IPv6-MoS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|target network | MoS-type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. .
. Home Network Identifier .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code
OPTION_IPv6-MoS (TBD)
option-len
2 + length of the Home Network Identifier field
Target network
The target network for the location of MoS Identifier:
1 local network
2 home network
3 both local and home networks
MoS-Type
The type of Mobility Services the MN is looking for,
i.e. IS, ES or CS or a combination of these:
1 IS service
2 ES service
3 both IS and ES services
4 CS service
5 IS and CS services
6 ES and CS services
7 IS, ES and CS services
Home Network Identifier
The identifier to specify the requested home network of
the mobile node. This field MUST be set in the form of
FQDN [RFC1035].
The target network value 1 indicates the mobile node is interested
in learning MoS information that pertains to the currently visited
network. This type can be used to discover local MoS. In this case,
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the option-len field is set to 2 and the Home Network Identifier
field MUST NOT be included.
The target network value of 2 indicates the mobile node is
interested in learning the MoS information that pertains to the home
network of the MN. This type can be used to discover MoS that are
hosted by a user's home domain. The MN's home network is specified
in the Home Network Identifier field.
The target network value of 3 indicates the mobile node is
interested in learning the MoS information that pertains to both
local and home networks of the MN.
3.2 IPv6 Relay Agent MoS Option
This option carries the home network information which was
transferred to the NAS from AAAH by using [I-D.ietf-mip6-radius-MoS,
TBD]. The DHCP relay agent sends this option to the DHCP server in
the Relay-forward Message.
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_IPv6-MoS-RELAY | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. sub-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code
OPTION_IPv6-MoS-RELAY (TBD).
option-len
The length of sub-options
sub-options
A series of IPv6 Relay Agent sub-options.
3.2.1. IPv6 Relay Agent Sub-option
This sub-option carries the MoS information to the DHCP server.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-opt-code | sub-opt-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MoS Type | |
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. MoS Address .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sub-opt-code
A 16-bit unsigned integer for the type of the following
MoS Address field. Possible values are:
1 MoS IP address list
2 MoS FQDN list
sub-opt-len
1 + The length of MoS Address field.
MoS type
The type of MoS services the server supports. Valid
values:
1 IS service
2 ES service
3 both IS and ES services
4 CS service
5 IS and CS services
6 ES and CS services
7 IS, ES and CS services
MoS Address
An MoS IP address or MoS FQDN to be provided to a mobile
node according to the sub-opt-code.
When the sub-opt-code is set to 1, the MoS Address field MUST
contain the 128-bit IPv6 address of the MoS.
When the sub-opt-code is set to 2, the MoS Address field MUST
contain the FQDN of the MoS as described in Section 8 of [RFC3315].
Multiple sub-options may exist in a IPv6 Relay Agent option to carry
more than one MoS address or FQDN.
3.3 MoS Information Option
This option is included in the Reply message and used to carry MoS
information to the mobile node in the form of one or more of MoS IP
address(es) or MoS FQDN(s).
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_IPv6-MoSINF | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. sub-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code
OPTION_IPv6-MoSINF (TBD).
option-len
length of sub-options
sub-options
A series of MoS Information sub-options.
3.3.1 MoS Information Sub-option
This sub-option carries the assigned MoS information to the DHCP
client.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-opt-code | sub-opt-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MoS Type | network | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. MoS Information .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
sub-opt-code
A 16-bit unsigned integer for the type of the following
MoS Information field. Possible values are:
1 MoS address
2 MoS FQDN
sub-opt-len
2 + length of MoS Information field.
MoS type
An 8 bit integer specifying the type of MoS services the
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server supports. Valid values are:
0 NULL
1 IS service
2 ES service
3 both IS and ES services
4 CS services
5 IS and CS services
6 ES and CS services
7 IS, ES and CS services
network
An 8 bit integer specifying the network where the MoS
whose address is attached, resides. Valid values:
1 home network
2 local network
MoS Information
An MoS IP address or MoS FQDN to be provided to a mobile
node according to the sub-opt-code.
The sub-opt-code, sub-opt-len and MoS Information fields are set in
the same manner as those of an IPv6 Relay Agent sub-option.
4. Option Usage
4.1 Usage of DHCPv4 Options for MoS Discovery
The requesting and sending of the proposed DHCPv4 options follow the
rules for DHCP options in [RFC2131].
4.1.1 Mobile Node behavior
The mobile node may perform the MoS information discovery procedure
either during initial association with a network or when the
mobility service is required. It may also try to perform the MoS
information discovery when it lacks the network information for MoS
or needs to change the MoS for some reasons, for instance, to
recover from the single point of failure of the existing MoS
In order to acquire the MoS information, the mobile node MUST send a
REQUEST message to a unicast server address. In this message the
mobile node (DHCP client) MUST include the Option Code for the MoS
Discovery option in the OPTION_code.
4.1.2 DHCP Server behavior
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When the DHCP server receives the REQUEST message with the MoS
Discovery option in the OPTION_code, the DHCP server MUST follow the
[RFC2131] logic to construct a REPLY message with the MoS Discovery
option. The reply message may contain IP address or the FQDN of the
MoS Server.
In case that the server cannot find any MoS information, it MUST
return the MoS Discovery option by setting the MoS Server address
0.0.0.0 with 'enc' 1.
4.2 DHCPv6 Options for MoS discovery
TBD.
4.2.1 Mobile node behavior
4.2.2 DHCP Relay Agent behavior
4.2.3 DHCP Server behavior
5. Security Considerations
The security considerations in [RFC2131] apply. If an adversary
manages to modify the response from a DHCP server or insert its own
response, an MN could be led to contact a rogue Mobility Server,
possibly one that then would provide wrong information, event or
command for handover.
It is recommended to use either DHCP authentication option described
in [RFC3118] where available, or rely upon link layer security. This
will also protect the denial of service attacks to DHCP servers.
[RFC3118] provides mechanisms for both entity authentication and
message authentication.
6. IANA Considerations
This document registers the following dhcpv4 options with IANA:
IPv4-IS
IPv4-ES
IPv4-CS
This document also registers the following dhcpv6 options with IANA:
IPv6-MoSINF
IPv6-MoS
This document also registers the following dhcpv6 Relay options with
IANA:
IPv6-MoS-RELAY
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7. Acknowledgements
Acknowledgements to the DT members.
8. Normative References
[1] IEEE 802.21 Standard for Local and Metropolitan Area Networks:
Media Independent Handover Services
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[7] Lemon, T. and S. Cheshire, "Encoding Long DHCP Options",
RFC3396, November 2002.
[RFC3118] Authentication for DHCP Messages, Droms et al, June 2001
[RFC3315] Dynamic Host Configuration Protocol for IPv6 (DHCPv6),
Droms et al, July 2003
9. Informative References
[8] Bajko, G. " Locating Mobility Servers", draft-bajko-mos-dns-
discovery-00.txt
10. Author's Addresses
Gabor Bajko
Nokia
gabor.bajko@nokia.com
Subir Das
Telcordia
subir@research.telcordia.com
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