Internet DRAFT - draft-arifumi-ipv6-nd-source-address-select
draft-arifumi-ipv6-nd-source-address-select
Arifumi Matsumoto
Internet-Draft Tomohiro Fujisaki
Expires: July 26, 2005 Hirotaka Matsuoka
Jun-ya Kato
NTT PF Lab.
January 26, 2005
Configuring Source Address Selection Policy
by Neighbor Discovery Protocol for IPv6
draft-arifumi-ipv6-nd-source-address-select-02
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document describes a Neighbor Discovery IPv6 Source Address
Selection(SAS) Policy option for distributing of source address
selection policies to end nodes. This option is particularly
effective when a consumer site has multiple address blocks. Every
end node is guided by such a policy in selecting an appropriate
source address for each destination address. This makes it possible
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for an end node to set up a connection without concern for transfer
failures due to ingress filtering by ISPs, for ISP operators to
manage user behavior and networking policy, and for consumers to be
provided with networks that are almost automatically robust and
reliable.
1. Introduction
An IPv6 multihoming site has multiple nodes, each of which is
assigned multiple IPv6 addresses by up stream ISPs. When there are
multiple up stream ISPs, the current means of selecting the ISP for
an outgoing packet is based on the destination address. Actually, in
general, each packet should have a source address that has been
allocated by the selected up stream ISP. This is because the routers
of ISPs may be configured to perform ingress filtering with the aim
of blocking packets with illegal source addresses.
In another Internet-Draft [1], we propose a technique that can be
used both to distribute policy information for source address
selection(SAS) at end nodes and to establish a method for packet-
forwarding by routers. This enables ISPs to control incoming traffic
from customer sites and the end nodes to select appropriate source
addresses. It also enables the selection of outgoing ISPs in a way
that is almost certain to produce successful connection setups.
In this document, we propose an extension to the Neighbor Discovery
Router Advertisement Message [2]. In another draft, we propose a new
option [5] for DHCPv6 [3,4] to handle delivery of address selection
policies end nodes. An address selection policy delivered to an end
node is stored in the form of a policy table, as defined in RFC 3484
[6]. These two drafts are protocol specifications implementing the
multihome network technique proposed previously [1].
2. Terminology
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 [7].
3. Message formats
3.1. Changes to Prefix Information option of Router Advertisement
Message
The change from Neighbor Discovery [2] section 4.6 is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Prefix Length |L|A|M| SASID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preferred Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields:
SASID
A 5-bit unsigned integer; the identifier of the Source Address
Selection (SAS) Policy option related to this Prefix Information
option. Each Prefix Information option can be linked with one
SAS Policy option, as mentioned in the next paragraph. If this
Prefix Information option isn't bound with any SAS Policy
option, the value of this field must be zero. Otherwise, it
will be the identifier of the corresponding SAS option.
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3.2 Source Address Selection (SAS) Policy option
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 | Reserved | SASID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | |
+-+-+-+-+-+-+-+-+ Prefix (Variable Length) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Prefix Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Prefix (Variable Length) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Prefix Length & Prefix ... .
. +-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding and End Marker |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields:
Type TBD
Length An 8-bit unsigned integer; the length of the option
(including the Type and Length fields) in units of 8 octets.
Reserved A 10-bit unused field. This field MUST be initialized to
zero by the sender and ignored by the receiver.
SASID A 5-bit unsigned integer; the identifier of the SAS Policy
option. A Router Advertisement Message cannot contain
multiple SAS Policy options with the same SASID. With this
identifier, the SAS Policy options are linked with the Prefix
Information option. An SAS Policy option with no linked
Prefix Information option will be discarded.
Prefix Length
An 8-bit unsigned integer; the number of leading bits in the
prefix that are valid. The value ranges from 0 to 128. The
Prefix field is 0, 4, 8, 12, or 16 octets, depending on the
length.
Prefix A variable-length field containing an IP address or the
prefix of an IP address. The Prefix Length field contains
the number of valid leading bits in the prefix. The bits in
the Prefix after the prefix length (if any) MUST be
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initialized to zero by the sender and ignored by the
receiver. Pairs of Prefix Length and Prefix field may follow
here.
Padding and End Marker A variable-length padding field for 32-bit
alignment. This field also serves as a end marker and MUST
be initialized to 1 by the sender and ignored by the
receiver, in order not to be confused with Prefix field.
This option appears only in Router Advertisement Message and has to
have corresponding Prefix Information option within the same Router
Advertisement Message. Otherwise, this option MUST be ignored.
3.3 Discussion
The SASID, mentioned above, is used to link the Prefix Information
and a SAS Policy option. This field occupies as much space as 5-bit
reserved field in the Prefix Information option. Instead of the
SASID, an alternative method of linking is to copy the prefix of the
corresponding Prefix Information option into the SAS Policy option,
as shown in the figure below. This method, however, is expected to
consume more option space.
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 | Prefix Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
| Prefix |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | |
+-+-+-+-+-+-+-+-+ Prefix (Variable Length) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Prefix Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Prefix (Variable Length) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Prefix ... .
. +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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4. Specifications
4.1 Router Specification
- The SAS Policy option MUST NOT appear in anything other than a
Neighbor Discovery Router Advertisement Message.
- Multiple Prefix Information options can share the same SASID.
- When a router has too much information to make into one packet
(1280 bytes), the incident SHOULD be reported or logged.
4.2 Host Specification
- An SAS Policy option in anything other than a Neighbor
Distribution Router Advertisement Message MUST be ignored.
- Each SAS Policy option is linked with one or more Prefix
Information options. This tuple will be kept in a policy table,
as defined in RFC 3484, Section 2.1 [6]. Assume that a host
receives the following tuples:
Prefix SAS
2001:1:1:1::/64 - SAS1 (2001:1::/16, 2001:2::/16)
2001:2:2:2::/64 - SAS1 (2001:1::/16, 2001:2::/16)
2002:3:3:3::/64 - SAS2 (::/0)
Table 1
Then, these tuples are stored in a policy table like that shown
below.
Prefix Precedence Label
2001:1:1:1::/64 undefined 10
2001:2:2:2::/64 undefined 10
2001:1::/16 undefined 10
2001:2::/16 undefined 10
2002:3:3:3::/64 undefined 20
::/0 undefined 20
Table 2
The first two tuples in Table 1 are linked with the same SAS
Policy option (SAS1), so they are also linked with each other, and
thus, they have the same Label value in Table 2.
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- When two Prefixes contained in different SAS Policy options are
the same, the Prefixes will be ignored.
- Each SAS Policy option has a lifetime, which is the valid lifetime
of the corresponding Prefix Information option. When an SAS
Policy option is related to multiple Prefix Information options,
its lifetime will be the maximum lifetime among those of all the
Prefix Information options.
5. Security Considerations
With regard to the possibility of traffic abduction by announcing a
bogus policy, this scheme seems to neither lower nor raise the
security level obtained with the existing base protocol, namely,
Neighbor Discovery Router Advertisement. It does, however, raise the
possibility of a new form of DoS attack on routers and hosts, in
which large numbers of address selection policies are generated by
different source addresses. We will have to discuss this and take
precautionary measures in designing the protocol specification.
6. IANA Considerations
This document defines a new ICMP option type. This must be assigned
ICMPv6 type number.
7. Revision History
- Unit of Source Address Selection Policy Option's Length field was
changed to 8 octets in conformance with RFC 2461.
- The length of SASID field in Prefix Information Option and Source
Address Selection Policy Option reduced to 5 bits for the support
of R flag defined by MobileIPv6 [8].
- The field name 'padding' was changed to 'padding and end marker' to
clarify that it isn't just a padding.
8. Normative References
[1] Matsumoto, A., Fujisaki, T., Matsuoka. H and J. Kato, "Source
Address Selection Policy Distribution for Multihoming",
Internet-Draft, January 2005, draft-arifumi-ipv6-sas-policy-
dist-00.txt. (Work In Progress)
[2] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery
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for IP Version 6 (IPv6)," RFC 2461, December 1998.
[3] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M.
Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)," RFC 3315, July 2003.
[4] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host
Configuration Protocol (DHCP) version 6" RFC 3633, December
2003.
[5] Matsuoka, H., Fujisaki, T., Kato, J. and A. Matsumoto, "Source
Address Selection Option DHCPv6," Internet-Draft, October
2004, draft-hirotaka-dhcp6-sas-option-00.txt.
[6] R. Draves, "Default Address Selection for Internet Protocol
version 6 (IPv6)," RFC 3484, February 2003.
[7] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[8] D. Johnson, C. Perkins, J. Arkko, "Mobility Support in IPv6",
RFC 3775, June 2004.
Authors' Addresses
Arifumi Matsumoto
Nippon Telegraph and Telephone Corporation
Information Sharing Platform Laboratories
3-9-11 Midori-cho
Musashino-shi, Tokyo 180-8585 Japan
Phone: +81-422-59-3334
E-Mail: matsumoto.arifumi@lab.ntt.co.jp
Tomohiro Fujisaki
Nippon Telegraph and Telephone Corporation
Information Sharing Platform Laboratories
3-9-11 Midori-cho
Musashino-shi, Tokyo 180-8585 Japan
Phone: +81-422-59-7351
E-Mail: fujisaki.tomohiro@lab.ntt.co.jp
Hirotaka Matsuoka
Nippon Telegraph and Telephone Corporation
Information Sharing Platform Laboratories
3-9-11 Midori-cho
Musashino-shi, Tokyo 180-8585 Japan
Phone: +81-422-59-4949
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E-Mail: matsuoka.hirotaka@lab.ntt.co.jp
Jun-ya Kato
Nippon Telegraph and Telephone Corporation
Information Sharing Platform Laboratories
3-9-11 Midori-cho
Musashino-shi, Tokyo 180-8585 Japan
Phone: +81-422-59-2939
E-Mail: kato.junya@lab.ntt.co.jp
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