IPv6 Operations Working Group A. Matsumoto Internet-Draft T. Fujisaki Intended status:
Standards TrackInformational NTT Expires: August 5,November 16, 2007 R. Hiromi K. Kanayama Intec Netcore May 15, 2007 Requirements for theaddress selection mechanisms draft-ietf-v6ops-addr-select-req-01.txtdraft-ietf-v6ops-addr-select-req-02.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 5,November 16, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract RFC3484In a multi-prefix environment, nodes could have multiple addresses on one network interface. RFC 3484 defines source and destination address selection algorithms that areaddress-selection algorithm, which is commonly deployed in current popular OSs. Meanwhile, there is a possibility to provide multiple addresses in one physical network. In such a multi-prefix environment, end-hostsHowever, nodes could encounter some troublesdifficulties in thenetwork communication because of defaultwhen they use of the RFC3484 mechanism.default address selection rules defined in RFC 3484. Some mechanismmechanisms for thesolving address selection problems are proposed including RFC3484the RFC 3484 policy table distribution and RFC3484-update.ICMP error-based mechanisms. This document describes the requirements for these address selection mechanisms. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Scope of this document . . . . . . . . . . . . . . . . . . 32. Requirements of Address Selection . . . . . . . . . . . . . . 3 2.1. Contents of Policy Table . . . . . . . . . . . . . . . .. 3 2.2. Timing . . . . .2.1. Effectiveness . . . . . . . . . . . . . . . . . . . . . 4 2.3. Redistribution of changed Policy Table. . 3 2.2. Timing . . . . . . . . 4 2.4. Sections. . . . . . . . . . . . . . . . . . 3 2.3. Dynamic Behavior Update . . . . . . . 4 2.5. Generating Policy Table per CPE/Node. . . . . . . . . . . 4 2.6. Security . . . . . . . . . . . . . .2.4. Node-Specific Behavior . . . . . . . . . . . 4 3. Possible Solutions for Address Selection Problem. . . . . . . 4 3.1. Routing System Assistance for Address Selection by Fred Baker . . . . . . . . .2.5. Application-Specific Behavior . . . . . . . . . . . . . . . 4 3.2. 3484-update . . . . . . . . . . . . . . . . . . . .2.6. Multiple Interface . . . 5 3.3. shim6. . . . . . . . . . . . . . . . . 4 2.7. Central Control . . . . . . . . . 6 3.4. policy distribution mechanism. . . . . . . . . . . . . 4 2.8. Next-hop Selection . 6 4. Discussion at 67th IETF. . . . . . . . . . . . . . . . . . . 7 5.4 3. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6.. 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 Appendix A. Solutions for RFC3484 policy distribution . . . . . . 9 A.1. Policy distribution with router advertisement (RA) message option . . . . .. 5 5. References . . . . . . . . . . . . . . . . 10 A.2. Policy distribution in DHCPv6. . . . . . . . . . 5 5.1. Normative References . . . . 10 A.3. Using other protocols. . . . . . . . . . . . . . . 5 5.2. Informative References . . . 11 A.4. Defining a new protocol. . . . . . . . . . . . . . . 5 Authors' Addresses . . 11 A.5. Converting routing information to policy table. . . . . . 11 7. References. . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 147 1. Introduction One physical network can have multiple logical networks. In that case, an end-host has multiple IP addresses. ( e.g. In the IPv4-IPv6 dual stack environment ordual-stack environment, in a site connected tothat uses both ULA [RFC4193] and global scope networks, an end-host has multiple IP addresses. These are examples of the networks that we focus onaddresses or in this document. Ina site connected to multiple upstream IPv6 networks) For such an environment, an end-host will encounter some communication trouble documented in PS. [I-D.arifumi-v6ops-addr-select-ps]a host, RFC 3484 [RFC3484] defines bothdefault address-selection rules for the source and destination address selection algorithms.addresses. Today, the RFC 3484 defines a default address table,mechanism is widely implemented in major OSs. However, we and enables adding other entries to this table. Flexible address selection can be carried out. In addition,others have found that in many sites the distribution of andefault address-selection rules are not appropriate for the network structure. PS [I-D.ietf-v6ops-addr-select-ps] lists problematic cases that resulted from incorrect address policy table is an important matter.selection. Though RFC 3484 describes all the algorithms for settingmade the address policy table, but it makes no mentionaddress-selection behavior of autoconfiguration. To make a smooth connection with the appropriate source and destination address selection insidea multi-prefix environment, nodes must be informed about routing policieshost configurable, typical users cannot make use of that because of their upstream networks and possible source address selection policies. Then, those nodes must put those policies into individual policy tables. On the other hand,the RFC3484 mechanism is commonly deployed. However, manual configurationcomplexity of the policy table is not a feasible ideamechanism and some automaticlack of knowledge about their network topologies. Therefore, an address-selection autoconfiguration mechanism is needed. In this document, requirementsnecessary, especially for distributionunmanaged hosts of thetypical users. This document contains requirements for address-selection mechanisms that enable hosts to perform appropriate address selection policy are described for promotional use of the RFC3484 mechanism. 1.1. Scope of this document The routing information from an upstream network is necessary, but in this document, we are focused on how to select source and destination addresses at the RFC3484 address policy table of the end-host.automatically. 2. Requirements of Address Selection Address-selection mechanisms have to fulfill the following seven requirements. 2.1. Contents of Policy Table A Policy Table is a set of Policies describedEffectiveness The mechanism can modify RFC 3484 default address-selection behavior at nodes. As documented in PS [I-D.ietf-v6ops-addr-select-ps], the default rules defined in RFC 3484. Each Policy consists of four elements: prefix value, precedence value, label value, and zone index value. The Policy distribution3484 do not work properly in some environment. Therefore, the mechanism shouldhas to be able to distributemodify address-selection behavior of a Policy Table that has one or more Policies to Nodes.host. 2.2. Timing The Policy Table should be distributed toNodes by a Policy broker at any timecan obtain address selection information when Nodes send a request fornecessary. If nodes need to have address-selection information before performing address selection, then the Policy. 2.3. Redistribution of changed Policy Table When a Policy brokermechanism has any change in a Policy Table that is distributedto Nodes, the Policy broker should redistribute the latest Policy Tableprovide a way for nodes to Nodes. 2.4. Sectionsobtain necessary information beforehand. The Policy distributionmechanism should support being performed in two kinds of sections: from PE to CPE and from CPE to Node. Policy distribution mechanisms provided in each section may or manynot be the same. 2.5. Generating Policy Table per CPE/Nodedegrade userbility. The Policy distributionmechanism should allow for generating an appropriate Policy Table per Node. For example, in some cases, each Node may have a different setnot enforce long address- selection processing time upon users. 2.3. Dynamic Behavior Update Address-selection behavior of assigned prefixes. In such a case, the appropriate Policy Table for each Node may also be different, and a Policy broker maynodes can be needed to generatedynamically updated. When the Policy Table accordingnetwork structure changes and address-selection behavior has to be changed accordingly, a network administrator can modify the identityaddress-selection behavior of the Node. 2.6. Securitynodes. 2.4. Node-Specific Behavior The Policy distributionmechanism should provide for reliable, secure distribution of the Policy distribution from a Policy broker to Nodes. 3. Possible Solutions for Address Selection Problem A few mechanisms for address selection problemscan support node-specific address-selection behavior. Even when multiple nodes are proposed. This section quickly reviews each proposal including a policy distribution mechanism. 3.1. Routing System Assistance for Address Selection by Fred Baker Fred Baker proposed to us about this mechanism. A host asks the DMZ routers or the local router which is the best pair of source and destination addresses when the host has a set of addresses A and destination host has a set of addresses B. And then, the host uses the policy provided by the server/routing system as a guide in applying the response. He also proposed a mechanism that utilizes ICMP error message to change the source address of the existing session. This point resembles 5.2 3484-update mechanism, so the following evaluation is based only on the first part of his proposal. Advantages: - A host can choose the best address pair that reflects the dynamic changing routing status. - The destination address selection can be handled in this mechanisim as well as source address selection. Disadvantages: - A host can choose the best address pair that reflects the dynamic - A host has to consult the routing system every time it starts a connection if the host doesn't have address selection information for the destination host or the information lifetime is expired. This could be a possible scalability problem. - A host has to wait until the response is received from the routing system. - The existing host/router OS implementation has to be changed a lot. In the existing TCP/IP protocol stack implementation, destination address selection is mainly the role of the application and not that of the kernel unlike source address selection. Therefore, implementing this model without causing any affects on applications is not so easy. 3.2. 3484-update M. Bagnulo proposed a new method of address selection in his draft. [I-D.bagnulo-rfc3484-update] When the host notices that a network failure occurs or packets are dropped somewhere in the network by for example, an ingress filter, the host changes the source address of the connection to another source address. The host stores a cache of address selection information so that the host can select an appropriate source address for new connections. Advantages: - A host can choose the best address that reflects the dynamic changing routing status. Disadvantages: - A host has to learn address selection information per destination host. The number of cache entries can be too big. - The existing host/router OS implementation has to be changed a lot. In particular, changing the source address of the existing connection is not so easy and has a big impact on the existing TCP/IP protocol stack implementation. - There is not so much experience with this kind of address selection cache mechanism. - The host tries every address one-by-one, so the user has to wait for a long time before the appropriate address pair is found. 3.3. shim6 shim6 is designed for site-multihoming. This mechanism introduces a new method of address selection for session initiation and session survivability, which is documented in [I-D.ietf-shim6-locator-pair-selection] and [I-D.ietf-shim6-failure-detection]. The shim6 host detects connection failures and changes the source address during the session. Advantages: - The shim6 host performs address selection that reflects network failures in the source and destination end-to-end link. Moreover, network failure avoidance can be achieved by end hosts themselves. Disadvantages: - A host has to learn address selection information per destination host. The number of cache entry can be too big. - The existing host/router OS implementation has to be changed significantly. - The host tries every address one-by-one, so the user has to wait for a long time before the appropriate address pair is found. 3.4. policy distribution mechanism This mechanism takes advantages of RFC 3484 Policy Table that is widely deployed already. By distributing policies for Policy Table, you can auto-configure a host's address selection policy. Advantages: - A host can receive and understand address selection information before the host starts a connection. Therefore, the amount of traffic and connection overhead time can be minimized. - A host does not need any other address-selection-related information once that host receives the address selection policy set. This can also reduce the amount of traffic. - The existing OS implementation does not need to be changed significantly on the OS that implements the RFC 3484 policy table. Only the delivery mechanism to the table has to be prepared. - Destination address selection can also be controlled by this mechanism. Disadvantages: - No other address selection rule that is beyond the RFC 3484 policy table framework can be implemented. - The OS implementation has to be changed, and the policy distribution server, such as a gateway router, has to be prepared. - When DHCP or RA is used for transport mechanism of policy table, frequently changing policy cannot be delivered to hosts quickly because of the nature of these protocols. 4. Discussion at 67th IETF Here listed some points that was raised at San Diego and comments below. These points are classified into 3 classes from the aspect of RFC3484. It seems to be better to settle the basis for this discussion. That is, we can assume RFC3484 as it is now, we should modify RFC3484 or we should start from nothing. 1) Issues that don't need RFC3484 modification"> - The ability to deliver specific set of policies to a specific host This issue is already in the requiremnt draft. 2) Issues that may need slight RFC3484 change. - The address type dependent preference. There was a thread "address selection and DHCPv6" by James Carlson at IPv6 ML about address type dependent preference, such as DHCPv6, RA, manual and also privacy extension(RFC3041) address. http://www1.ietf.org/mail-archive/web/ipv6/current/msg06910.html It is hard to define default preferences for these address types, because it depends on the usage of these addresses, but not on address types themselves. It is the policy table where you can control host's address selection behavior. At this time, however, I cannot say policy table is the perfect way to fulfill this requirement. For example, You can set priority on 3041 address by putting a line in policy table specifying 3041 address by 128-bit prefixlen and continuing to update policy table according to 3041 address changes. But, this is surely troublesome for users and implementers. One idea is to update RFC3484 policy table definition so that it can handle alias addresses like privacy, DHCPv6 generated, RA generated, manually generated (and even Home Address ?) To prefer privacy address by default, and to prefer RA-generated address for site internal, the policy table will look like this. Prefix Pref Label 2001:db8:1234::(PRIVACY)/128 30 2 ::/0 10 2 2001:db8:1234::(RA):/128 30 1 2001:db8::/48 20 1 3) Issues that need big RFC 3484 change. - Multiple Interfaces Issues Dave Thaler gave us comments that multiple-interface hosts may face policy collision and distribution of dst address selection policy and src address selection policy should be separated. Also, per-interface policy table was proposed. After all, this is a policy collision problem. To make a host have one policy table per network interface doesn't solve policy collision issue. Source address selection is performed after output interface is selected, but destination address selection is before output interface selection. In this case, destination address selection uses all the policy tables a host has, so here collision can happen. Separating destination address selection and source address selection will have a big change on RFC3484 policy table definition. Though it may be a good idea to avoid source address selection policy collision. - application specific address selection should be considered. Also, XML was proposed for the right format to describe those policies. This issue is so much application dependent. Even if policy table supports application specific policies, the application doesn't necessarily follow the policy table. It seems to me a better idea to use address selection APIs or application specific configuration file for it. 5. Security Considerations Address false-selection can lead to serious security problem, such as session hijack. However, it should be noted that address selection is eventually up to end-hosts. We have no means to enforce one specific address selection policy to every end-host. So, a network administrator has to take countermeasures for unexpected address selection. 6. IANA Considerations This document has no actions for IANA. Appendix A. Solutions for RFC3484 policy distribution In this section, several mechanisms for distributing RFC3484 policy are compared and evaluated. The reason why this section is in appendix is that these discussions should be after address selection mechanism selection is finished and policy distribution mechanism is selected. solution. As described in section 3.1, the address selection policy table consists of four elements: prefix value, precedence, label, and zone- index. The policy distribution mechanism will deliver lists of these elements. A.1. Policy distribution with router advertisement (RA) message option The RA message can be used to deliver a policy table by adding a new ND option. Existing ND transport mechanisms (i.e., advertisements and solicitations) are used. Advantages and disadvantages are almost the same as those described in [DNS configuration RFC, RA section]. In addition, an advantage and disadvantages of distributing a policy table are as follows. Advantages: - The RA message is used to deliver IPv6 address prefixes. Therefore, delivering policies for selecting addresses with the address attached to the host would be natural. Disadvantages: - The RA message is limited in size, and the RA may not be sufficient to deliver full policies. The same compression techniques, which were adopted in RFC4191 [RFC4191] can be used to increase the number of policies delivered by RA messages. - Currently, RA messages are not used between a PE and CPE. Other protocols may be necessary to deliver a policy table. - Configuring a policy table in each router that advertises RA messages with an address prefix is necessary, so if a site has a lot of routers, there will be a higher management cost. - Delivering a specific policy table to one node is impossible because RA messages are multicast. A.2. Policy distribution in DHCPv6 By defining a new DHCPv6 option like [I-D.fujisaki-dhc-addr-select-opt], a policy table can be delivered. The advantages and disadvantages are almoston the same as those described in [DNS configuration RFC, DHCPv6 section]. In addition, there are the following advantages and disadvantages. Advantages: - Currently, DHCPv6 prefix delegation is mainly used between a PE and CPE. Delivering a policy table with prefixes is possible. - A DHCPv6 server can deliver a host-specific policy table. - By using a DHCPv6 relay mechanism, managing a policy table from a central server is possible. Disadvantages: - The DHCPv6 message size is limited to the maximum UDP transmission size, so delivering complex policies by DHCPv6 may be impossible. A.3. Using other protocols Using other protocols (i.e., http and ftp) to deliversubnet, the policy table is possible. Advantages: - No new transport mechanisms are necessary. Disadvantages: - Other service discovery mechanisms will be necessary. - The procedure to distribute informationmechanism should be defined (e.g., whenable to distribute and whereprovide a method for the information is stored). - Existing protocolsnetwork administrator to make nodes behave differently. For example, each node may nothave a mechanism to inform clients about policy changes. A.4. Defining a new protocol Defining a new protocol to deliverdifferent set of assigned prefixes. In such a policy table will havecase, the following advantages and disadvantages. Advantages: - Defining a protocol suitable for policy distributionappropriate address-selection behavior may be possible. Disadvantages: - In additiondifferent. 2.5. Application-Specific Behavior The mechanism can support application-specific address-selection behavior or combined use with an application-specific address- selection mechanism such as address-selection APIs. 2.6. Multiple Interface The mechanism can support those nodes equipped with multiple interfaces. The mechanism has to the disadvantagesassume that nodes have multiple interfaces and makes address selection of those nodes work appropriately. 2.7. Central Control The address selection behavior of 4.3,nodes can be centrally controlled. A site administrator or a new transportservice provider can determine or have effect on address-selection behavior at their users' hosts. 2.8. Next-hop Selection The mechanism needs to be defined. A.5. Convertingcan control next-hop-selection behavior at hosts or cooperate with other routing information to policy table In an environment in whichmechanisms, such as routing information and network links are separated (e.g., between PEprotocols and CPE), convertingRFC 4191 [RFC4191]. If the address-selection mechanism is used with a routing informationmechanism, the two mechanisms has to a policy table is possible.be able to work synchronousely. 3. Security Considerations Incorrect address-selection can lead to serious security problems, such as session hijack. However, when intermediate routers and nodes receive next-hop information,we should note that address- selection is aggregated as a default route or neighbor router,ultimately decided by nodes and cannot generate policy table [a policy table cannot be generated]. Advantages: - No new distribution mechanism is necessary. Disadvantages: - This mechanism can be used only intheir users. There are no means to enforce a limited environment. 7.specific address-selection behavior upon every end-host from outside of the host. Therefore, a network administrator has to take countermeasures for unexpected address selection. 4. IANA Considerations This document has no actions for IANA. 5. References 126.96.36.199. Normative References [I-D.arifumi-v6ops-addr-select-ps][I-D.ietf-v6ops-addr-select-ps] Matsumoto, A., "Problem Statement of Default Address Selection in Multi-prefix Environment: Operational Issues of RFC3484 Default Rules", draft-arifumi-v6ops-addr-select-ps-01draft-ietf-v6ops-addr-select-ps-01 (work in progress), October 2006.April 2007. [RFC3484] Draves, R., "Default Address Selection for Internet Protocol version 6 (IPv6)", RFC 3484, February 2003. 188.8.131.52. Informative References [I-D.bagnulo-rfc3484-update] Bagnulo, M., "Updating RFC 3484 for multihoming support", draft-bagnulo-rfc3484-update-00 (work in progress), June 2006. [I-D.fujisaki-dhc-addr-select-opt] Fujisaki, T., "Distributing Default Address Selection Policy using DHCPv6", draft-fujisaki-dhc-addr-select-opt-03 (work in progress), January 2007. [I-D.ietf-shim6-failure-detection] Arkko, J. and I. Beijnum, "Failure Detection and Locator Pair Exploration Protocol for IPv6 Multihoming", draft-ietf-shim6-failure-detection-07 (work in progress), December 2006. [I-D.ietf-shim6-locator-pair-selection] Bagnulo, M., "Default Locator-pair selection algorithm for the SHIM6 protocol", draft-ietf-shim6-locator-pair-selection-01 (work in progress), October 2006.[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and More-Specific Routes", RFC 4191, November 2005. [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, October 2005. Authors' Addresses Arifumi Matsumoto NTT PF Lab Midori-Cho 3-9-11 Musashino-shi, Tokyo 180-8585 Japan Phone: +81 422 59 3334 Email: email@example.com Tomohiro Fujisaki NTT PF Lab Midori-Cho 3-9-11 Musashino-shi, Tokyo 180-8585 Japan Phone: +81 422 59 7351 Email: firstname.lastname@example.org Ruri Hiromi Intec Netcore, Inc. Shinsuna 1-3-3 Koto-ku, Tokyo 136-0075 Japan Phone: +81 3 5665 5069 Email: email@example.com Ken-ichi Kanayama Intec Netcore, Inc. Shinsuna 1-3-3 Koto-ku, Tokyo 136-0075 Japan Phone: +81 3 5665 5069 Email: firstname.lastname@example.org Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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