--- 1/draft-ietf-6man-addr-select-opt-08.txt 2013-05-02 08:24:27.020708546 +0100 +++ 2/draft-ietf-6man-addr-select-opt-09.txt 2013-05-02 08:24:27.504720622 +0100 @@ -1,49 +1,49 @@ -6man Working Group A. Matsumoto -Internet-Draft T. Fujisaki +6man Working Group A.M. Matsumoto +Internet-Draft T.F. Fujisaki Intended status: Standards Track NTT -Expires: July 20, 2013 T. Chown +Expires: October 27, 2013 T.C. Chown University of Southampton - January 16, 2013 + April 25, 2013 Distributing Address Selection Policy using DHCPv6 - draft-ietf-6man-addr-select-opt-08.txt + draft-ietf-6man-addr-select-opt-09.txt Abstract RFC 6724 defines default address selection mechanisms for IPv6 that allow nodes to select an appropriate address when faced with multiple source and/or destination addresses to choose between. The RFC 6724 allowed for the future definition of methods to administratively configure the address selection policy information. This document defines a new DHCPv6 option for such configuration, allowing a site administrator to distribute address selection policy overriding the default address selection parameters and policy table, and thus control the address selection behavior of nodes in their site. -Status of this Memo +Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on July 20, 2013. + This Internet-Draft will expire on October 27, 2013. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -171,66 +170,64 @@ source address prefixes and destination address prefixes. precedence: An 8-bit unsigned integer; this value is used for sorting destination addresses. prefix-len: An 8-bit unsigned integer; the number of leading bits in the prefix that are valid. The value ranges from 0 to 128. prefix: A variable-length field containing an IP address or the prefix of an IP address. An IPv4-mapped address [RFC4291] must - be used to represent an IPv4 address as a prefix value. The - prefix should be left aligned, big-endian, and zero padded on - the right up to the next octet boundary. So the length of this - field should be between 0 and 16 bytes. - -3. Appearance of the Address Selection options - - The Address Selection options MUST NOT appear in any DHCPv6 messages - other than the following ones: Solicit, Advertise, Request, Renew, - Rebind, Reconfigure, Information-Request, and Reply. + be used to represent an IPv4 address as a prefix value. This + field is padded with zeros up to the nearest octet boundary when + prefix6-len is not divisible by 8. This can be expressed using + the following equation: (prefix-len+7)/8 So the length of this + field should be between 0 and 16 bytes. For example, the prefix + 2001:db8::/60 would be encoded with an prefix-len of 60, the + prefix would be 8 octets and would contains octets 20 01 0d b8 + 00 00 00 00. -4. Processing the Policy Table option +3. Processing the Policy Table option This section describes how to process received Policy Table option at the DHCPv6 client. This option's concept is to serve as a hint for a node about how to behave in the network. So, basically, it should be up to the node's administrator how to deal with the received policy information in the way described below. -4.1. Handling of the local policy table +3.1. Handling of the local policy table RFC 6724 defines the default policy table. Also, users are usually able to configure the policy table to satisfy their own requirements. The client implementation SHOULD provide the following choices to the user: a) replace the existing active policy table with the DHCPv6 distributed policy table. + b) preserve the existing active policy table, whether this be the default policy table, or user configured policy. -4.2. Handling of the stale policy table +3.2. Handling of the stale policy table When the information from the DHCP server goes stale, the policy received form the DHCP server should be deprecated. The received information can be considered stale in several cases, such as, when the interface goes down, the DHCP server does not respond for a certain amount of time, and the Information Refresh Time is expired. -4.3. Multi-interface situation - +3.3. Multi-interface situation The policy table, and other parameters specified in this document are node-global information by their nature. One reason being that the outbound interface is usually chosen after destination address selection. So, a host cannot make use of multiple address selection policies even if they are stored per interface. Even if the received policy from one source is merged with one from another source, the effect of both policy are more or less changed. The policy table is defined as a whole, so the slightest addition/ deletion from the policy table brings a change in semantics of the @@ -255,21 +253,21 @@ The above restrictions do not preclude implementations from providing configuration options to enable this option on a certain network interface. Nor, they do not preclude implementations from storing distributed address selection policies per interface. They can be used effectively on such implementations that adopt per-application interface selection. -5. Implementation Considerations +4. Implementation Considerations o The value 'label' is passed as an unsigned integer, but there is no special meaning for the value, that is whether it is a large or small number. It is used to select a preferred source address prefix corresponding to a destination address prefix by matching the same label value within the DHCP message. DHCPv6 clients SHOULD convert this label to a representation appropriate for the local implementation (e.g., string). o Currently, the label and precedence values are defined as 8-bit @@ -282,86 +280,81 @@ possible to carry over 3,000 rules in one DHCPv6 message (maximum UDP message size). However, it should not be expected that DHCP clients, servers and relay agents can handle UDP fragmentation. Network adiministrators SHOULD consider local limitations to the maximum DHCPv6 message size that can be reliably transported via their specific local infrastructure to end nodes; and therefore they SHOULD consider the number of options, the total size of the options, and the resulting DHCPv6 message size, when defining their Policy Table. - o Since the number of selection rules could be large, an - administrator configuring the policy to be distributed should - consider the resulting DHCPv6 message size. - -6. Security Considerations +5. Security Considerations A rogue DHCPv6 server could issue bogus address selection policies to a client. This might lead to incorrect address selection by the client, and the affected packets might be blocked at an outgoing ISP because of ingress filtering, incur additional network charges, or be misdirected to an attacker's machine. Alternatively, an IPv6 transition mechanism might be preferred over native IPv6, even if it is available. To guard against such attacks, a legitimate DHCPv6 server should communicate through a secure, trusted channel, such as a channel protected by IPsec, SEND and DHCP authentication, as described in section 21 of RFC 3315, Another threat is about privacy concern. As in the security consideration section of RFC 6724, at least a part of, the address selection policy stored in a host can be leaked by a packet from a remote host. This issue will not be modified by the introduction of this option, regardless of whether the host is multihomed or not. -7. IANA Considerations +6. IANA Considerations IANA is requested to assign option codes to OPTION_ADDRSEL and OPTION_ADDRSEL_TABLE from the option-code space as defined in section "DHCPv6 Options" of RFC 3315. -8. References -8.1. Normative References +7. References + +7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [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. [RFC3484] Draves, R., "Default Address Selection for Internet Protocol version 6 (IPv6)", RFC 3484, February 2003. [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, "Default Address Selection for Internet Protocol Version 6 (IPv6)", RFC 6724, September 2012. -8.2. Informative References +7.2. Informative References [I-D.ietf-6man-addr-select-considerations] Chown, T. and A. Matsumoto, "Considerations for IPv6 - Address Selection Policy Changes", - draft-ietf-6man-addr-select-considerations-04 (work in - progress), October 2011. + Address Selection Policy Changes", draft-ietf-6man-addr- + select-considerations-05 (work in progress), April 2013. [I-D.ietf-6man-addr-select-sol] Matsumoto, A., Fujisaki, T., and R. Hiromi, "Solution - approaches for address-selection problems", - draft-ietf-6man-addr-select-sol-03 (work in progress), - March 2010. + approaches for address-selection problems", draft-ietf- + 6man-addr-select-sol-03 (work in progress), March 2010. - [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 - (IPv6) Specification", RFC 2460, December 1998. + [RFC2460] Deering, S.E. and R.M. Hinden, "Internet Protocol, Version + 6 (IPv6) Specification", RFC 2460, December 1998. [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. - Stevens, "Basic Socket Interface Extensions for IPv6", - RFC 3493, February 2003. + Stevens, "Basic Socket Interface Extensions for IPv6", RFC + 3493, February 2003. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 4941, September 2007. [RFC5220] Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama, "Problem Statement for Default Address Selection in Multi-