MIPSHOP WG Gabor Bajko
Internet Draft Nokia
Intended Status: Proposed Standard Subir Das
Expires: March 07, 2009 Telcordia
September 08, 2008
Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for
Mobility Server (MoS) discovery
draft-ietf-mipshop-mos-dhcp-options-05
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Copyright Notice
Copyright (C) The IETF Trust (2008).
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 [MSFD]. These
Mobility Services are used to assist an MN in handover preparation
(network discovery) and handover decision (network selection). The
services addressed in this document are the Media Independent
Handover Services defined in [IEEE802.21].
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.
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 [IEEE802.21].
MIH Service: IS, ES or CS type of service, as defined in
[IEEE802.21].
Table of Content
1. Introduction .................................................2
2. DHCPv4 Options for MoS Discovery..............................3
2.1 Domain Name List........................................5
2.2 IPv4 Address List.......................................6
3. DHCPv6 Options for MoS Discovery..............................6
3.1 IPv6 MoS Identifier Option..............................6
3.2 IPv6 MoS Information Option.............................7
4. Option Usage..................................................9
4.1 Usage of DHCPv4 Options for MoS Discovery...............9
4.2 Usage of DHCPv6 Options for MoS Discovery..............10
5. Security Considerations .....................................11
6. IANA Considerations .........................................11
7. Acknowledgements ............................................12
8. References ..................................................12
8.1 Normative References ...................................12
8.2 Informative References .................................12
Author's Addresses .............................................13
Intellectual Property and Copyright Statements .................13
1. Introduction
IEEE 802.21 [IEEE802.21] 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.
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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
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 [MSFD]. In practice a Mobility Server may
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 a new dhcpv4 option called MoS option, which
allows the MN to locate a Mobility Server which hosts the desired
service type (i.e. IS, ES or CS)as defined in [IEEE802.21]. The MoS
information type defines sub-options for different services. The
document also defines DHCPv6 options that allow the MN to
discover Mobility Servers hosting MIH services in different
deployment scenarios. Apart from manual configuration, this is one
of the possible solutions for locating a server providing Mobility
Services.
2. DHCPv4 Option for MoS Discovery
This section describes the MoS option for DHCPv4.
The MoS option begins with a option code followed by a length and
sub-options. The value of the length octet does not include itself
or the option code. The option layout is depicted below:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Option 1 |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Option n |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Option Code
OPTION-IPv4-MoS (TBD) - 2 bytes
Length
2 bytes
Sub-options
A series of DHCPv4 sub-options.
When the total length of a MoS option exceeds 255 octets, the
Procedure outlined in [RFC3396] MUST be employed to split the
option into multiple, smaller options.
A sub-option begins with a sub-option Type followed by a length
and a `enc` field. The value of the length octet does not include
itself or the option code. There are two types of 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. 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 [RFC3396].
The sub-option layout is depicted below:
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 Type | length | enc |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FQDN or IP Address |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The sub-option Types are summarized below.
+--------------+---------------+
| Sub-opt | Service |
| Type* | Name |
+==============+===============+
| 1 | IS |
+--------------+---------------+
| 2 | ES |
+--------------+---------------+
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+--------------+---------------+
| 3 | IS and ES |
+--------------+---------------+
| 4 | CS |
+--------------+---------------+
| 5 | IS and CS |
+--------------+---------------+
| 6 | ES and CS |
+--------------+---------------+
| 7 | IS, CS and ES |
+--------------+---------------+
*Note: The values `0` '8' to '255' are reserved and MUST NOT be used.
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 limits 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 international-
lized 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 [MoS-DNS] 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.
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.
The sub-option for this encoding has the following format:
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Type Len enc DNS name of MoS server
+-----+---+---+-----+-----+-----+-----+-----+--
|1..7 | 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:
+----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|1..7|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 sub-option for this encoding has the following format:
Code Len enc IPv4 Address 1 IPv4 Address 2
+-----+---+---+-----+----+---+----+----+--
|1..7 | n | 1 | a1 | a2 |a3 | a4 | a1 | ...
+-----+---+---+-----+----+---+----+----+--
3. DHCPv6 Options for MoS discovery
This section introduces new DHCPv6 options used for MoS discovery.
Whether the MN receives an MoS address from local or home network
will depend on the actual network deployment [MSFD].
3.1 IPv6 MoS Identifier Option
This option is included in the Information-request message and used
to request the address of a specific (e.g., IS, ES, CS or any
combination) MoS-type from a 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 Code | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MoS-type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Option Code
OPTION-IPv6-MoS (TBD) - 2 bytes
Length
2 bytes
MoS-Type*
1 byte
The type of Mobility Services the MN is looking for,
i.e., IS, ES or CS or a combination of these:
+--------------+-------------- +
| MoS-type | MoS Name |
| value | |
+==============+===============+
| 1 | IS |
+--------------+---------------+
| 2 | ES |
+--------------+---------------+
| 3 | IS and ES |
+--------------+---------------+
| 4 | CS |
+--------------+---------------+
| 5 | IS and CS |
+--------------+---------------+
| 6 | ES and CS |
+--------------+---------------+
| 7 | IS, CS and ES |
+--------------+---------------+
*Note: The values '0', '8' to '255' are reserved and MUST NOT be
used.
3.2 IPv6 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Sub-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Option Code
OPTION-IPv6-MoSINF (TBD)- 2 bytes
Length
The length of sub-options
sub-options
A series of MoS Information sub-options.
3.2.1 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 | Length | MoS Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. MoS Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sub-opt Code
An 8-bit unsigned integer for the type of the following
MoS Information field. Possible values are:
1 MoS IP address
2 MoS FQDN
Length
1 + length of MoS Information field.
MoS-Type*
1 byte
The type of Mobility Services the MN is looking for,
i.e., IS, ES or CS or a combination of these:
+--------------+-------------- +
| MoS Type | MoS Name |
| value | |
+==============+===============+
| 1 | IS |
+--------------+---------------+
| 2 | ES |
+--------------+---------------+
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+--------------+---------------+
| 3 | IS and ES |
+--------------+---------------+
| 4 | CS |
+--------------+---------------+
| 5 | IS and CS |
+--------------+---------------+
| 6 | ES and CS |
+--------------+---------------+
| 7 | IS, CS and ES |
+--------------+---------------+
*Note: The values '0', '8' to '255' are reserved and MUST NOT be
used.
MoS Information
An MoS IP address or MoS FQDN to be provided to a mobile
node as indicated in the sub-opt-code.
When the sub-opt-code is set to 1, the MoS Information field MUST
contain the 128-bit IPv6 address of the MoS.
When the sub-opt-code is set to 2, the MoS Information field MUST
contain the FQDN of the MoS as described in Section 8 of [RFC3315].
4. Option Usage
4.1 Usage of DHCPv4 Options for MoS Discovery
The requesting and sending of the proposed DHCPv4 option 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
either a DHCPDISCOVER or DHCPINFORM message to a subnet broadcast or
a unicast server address, respectively. In this message the mobile
node (DHCP client) MUST include the sub-opt Type for the MoS
Discovery in the sub-options field.
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4.1.2 DHCP Server behavior
When the DHCP server receives the DHCPDISCOVER or DHCPINFORM message
with the MoS Discovery option in the options field, the DHCP server
MUST follow the [RFC2131] logic to construct either a DHCPOFFER or
DHCPACK message including the MoS Discovery option. The reply
message may contain the IP address or the FQDN of the MoS Server.
The DHCP server MUST always construct the response according to
the Sub-opt Type requested by the DHCP client.
In case that the server cannot find any MoS information for a
specific MoS sub-opt Type, it MUST return the MoS option with a
sub-option by setting the sub-opt Type to the requested
sub-opt Type and the length of the sub-option to 1.
4.2 DHCPv6 Options for MoS discovery
The requesting and sending of the proposed DHCPv6 options follow the
rules for DHCP options in [RFC3315].
4.2.1 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 address, the mobile node MUST send an
Information-request message to the All_DHCP_Servers
multicast address. In this message the mobile node (DHCP client)
MUST include the Option Code for the MoS Discovery option in the
option_code.
4.2.2 DHCP Server behavior
When the DHCP Server receives the Information-request message the
DHCP server MUST follow the following logic to construct a Reply
message with the MoS Information option.
If the DHCP server has the requested MoS information, it MUST
include the information in the MoS Information option. The server
may provide the matching information from the preconfigured
information available locally.
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The DHCP server MUST always construct the response
according to the MoS Type requested by the DHCP client.
In case that the server cannot find any MoS information for a
specific MoS type, it MUST return the MoS Information option with
a sub-option by setting the MoS type to the requested MoS Type
and the length of the sub-option to 4.
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 defines one new DHCPv4 option as described in section
2.
MoS Option for DHCPv4 (OPTION-IPv4-MoS) TBD
This document creates a new registry for the Sub-Option field in the
MoS DHCPv4 option called the "MoS Service Type".
IS 1
ES 2
IS and ES 3
CS 4
IS and CS 5
ES and CS 6
IS, CS and ES 7
The values '0', '8' to '255' are reserved and MUST NOT be used. New
values can be allocated by Standards Action or IESG approval.
This document also defines new DHCPv6 options as described in
sections 3.1 and 3.2
IPv6-MoS (IPv6 MoS Identifier Option) TBD
IPv6-MoSINF (IPv6 MoS Information Option) TBD
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This document creates a new registry for the "MoS Type" field in
the IPv6 MoS Information Sub-option (section 3.2).
IS 1
ES 2
IS and ES 3
CS 4
IS and CS 5
ES and CS 6
IS, CS and ES 7
The values '0', '8' to '255' are reserved and MUST NOT be used. New
Values can be allocated by Standards Action or IESG approval.
7. Acknowledgements
Authors would like to acknowledge the following individuals for
their valuable comments.
Vijay Devarapalli, Telemaco Melia, and Yoshihiro Ohba
8. References
8.1 Normative References
[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.
[RFC3396] 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
8.2 Informative References
[IEEE802.21] IEEE 802.21 Standard for Local and Metropolitan Area
Networks: Media Independent Handover Services
[MoS-DNS] Bajko, G., "Locating Mobility Servers",
draft-ietf-mipshop-mos-dns-discovery, (Work in Progress),
May 2008.
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[MSFD] T Melia, Ed., " Mobility Services Framework Design (MSFD)",
draft-ietf-mipshop-mstp-solution, (Work in Progress)
Authors' Addresses
Gabor Bajko
Nokia
e-mail: gabor.bajko@nokia.com
Subir Das
Telcordia Technologies Inc.
e-mail: subir@research.telcordia.com
Full Copyright Statement
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