IPv6 Working Group A. Matsumoto Internet-Draft NTT Expires: August 1, 2005 T. Fujisaki H. Matsuoka J. Kato January 31, 2005 Source Address Selection Policy Distribution for Multihoming draft-arifumi-ipv6-sas-policy-dist-00.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. 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 become aware will be disclosed, in accordance with RFC 3668. 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 1, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document describes a method for the distribution of source address selection policy from ISPs to gateway routers for consumers and from the gateways to end nodes. This method is particularly effective when a consumer site has multiple address blocks. Every end node is guided by the policy in selecting an appropriate source Matsumoto, et al. Expires August 1, 2005 [Page 1] Internet-Draft SAS Policy Distribution January 2005 address for each destination address and every gateway is guided by the policy in forwarding packets to appropriate next-hop ISPs. This makes it possible for an end node to set a connection up without being concerned about failures of transfer due to ingress filtering by the ISPs, for ISP operators to manage consumers' behavior and networking policy, and for consumers to be provided with networks that are almost automatically robust and reliable. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2.1 Ingress Filtering Problem . . . . . . . . . . . . . . . . 3 2.2 Closed Network Problem . . . . . . . . . . . . . . . . . . 4 3. Concepts of Our Proposal . . . . . . . . . . . . . . . . . . . 5 4. Proposal Overview For Each Case . . . . . . . . . . . . . . . 7 4.1 Case 1: Multihome Site with Global-Closed Mixed Connectivity . . . . . . . . . . . . . . . . . . . . . . . 7 4.1.1 Description of Each Element . . . . . . . . . . . . . 7 4.1.2 Discussion . . . . . . . . . . . . . . . . . . . . . . 10 4.2 Case 2: Host with Multiple Addresses and Connectivity to Two Global Networks . . . . . . . . . . . . . . . . . . 11 4.2.1 Description of Each Element . . . . . . . . . . . . . 11 4.2.2 Discussion . . . . . . . . . . . . . . . . . . . . . . 13 4.3 Case 3: A Host Directly Connected to Multiple ISPs . . . . 13 5. Who merges conflicting policies and how ? . . . . . . . . . . 14 6. Failure Recovery . . . . . . . . . . . . . . . . . . . . . . . 14 6.1 Stop advertising . . . . . . . . . . . . . . . . . . . . . 14 6.2 Address Revocation . . . . . . . . . . . . . . . . . . . . 15 6.3 Policy Modification . . . . . . . . . . . . . . . . . . . 15 7. Solution Comparison . . . . . . . . . . . . . . . . . . . . . 15 7.1 Site Local Address . . . . . . . . . . . . . . . . . . . . 15 7.2 Router Selection . . . . . . . . . . . . . . . . . . . . . 16 7.3 Routing Protocol Based Policy Distribution . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 9. Revision History . . . . . . . . . . . . . . . . . . . . . . . 16 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 16 11. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . 17 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 12.1 Normative References . . . . . . . . . . . . . . . . . . . . 17 12.2 Informative References . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . . 19 Matsumoto, et al. Expires August 1, 2005 [Page 2] Internet-Draft SAS Policy Distribution January 2005 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 means of selection of the ISP for an outgoing packet is currently based on the destination address. In general, however, 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 that have strange source addresses. In this document, we clarify the problems of source address selection, list up solutions for them, and propose our solution, which is a technique that is used both to distribute policy information for source address selection at end nodes and to establish a method for the forwarding of packets by routers. This enables the control of incoming traffic from customer sites by ISPs, the selection of appropriate source addresses by end nodes, and the selection of outgoing ISPs in a way that is almost certain to produce successful connection setup. 2. Problem Statement 2.1 Ingress Filtering Problem ================== | Internet | ================== | | 2001:db8::/32 | | 3ffe:1800::/32 +----+-+ +-+----+ | ISP1 | | ISP2 | +----+-+ +-+----+ | | 2001:db8:a::/48 | | 3ffe:1800:a::/48 ++-------++ | Gateway | +----+----+ | 2001:db8:a:1::/64 | 3ffe:1800:a:1::/64 ------+---+---------- | +-+----+ 2001:db8:a:1:EUI64 | Host | 3ffe:1800:a:1:EUI64 +------+ [Fig. 1] Matsumoto, et al. Expires August 1, 2005 [Page 3] Internet-Draft SAS Policy Distribution January 2005 When a relatively small site, we call it "consumer network", is attached to two up-stream ISPs, each ISP delegates network address block, which is usually /48, and a host has multiple IPv6 addresses. When the source address of an outgoing packet isn't the one that is delegated by a transit ISP, the packet will be very probably dropped by ISP's ingress filter. Ingress filtering is getting popular and popular among ISPs in order to mitigate the damage of DoS attacks. One possible solution for this problem is to adopt source address based routing at consumer site's gateway, but this new way of routing is not widely deployed yet. 2.2 Closed Network Problem You can see a second typical source address selection problem in a multihome site with global-closed mixed connectivity like the figure below. In this case, Host-A is in a multihomed network and has two IPv6 addresses delegated from each of up-stream ISPs. Note that ISP2 is closed network and doesn't have connectivity to the Internet. +--------+ | Host-C | 3ffe:503:c:1:EUI64 +-----+--+ | ============== +--------+ | Internet | | Host-B | 3ffe:1800::EUI64 ============== +--------+ | | 2001:db8::/32 | | 3ffe:1800::/32 +----+-+ +-+---++ | ISP1 | | ISP2 | (Closed Network / VPN tunnel) +----+-+ +-+----+ | | 2001:db8:a::/48 | | 3ffe:1800:a::/48 ++-------++ | Gateway | +----+----+ | 2001:db8:a:1::/64 | 3ffe:1800:a:1::/64 ------+---+---------- | +--+-----+ 2001:db8:a:1:EUI64 | Host-A | 3ffe:1800:a:1:EUI64 +--------+ [Fig. 2] Matsumoto, et al. Expires August 1, 2005 [Page 4] Internet-Draft SAS Policy Distribution January 2005 This network environment isn't so uncommon as you might perhaps think of it. The access-line to the ISP2 might be actually a VPN tunnel over ISP1 and the Internet. When Host-A starts connection to Host-B in ISP2, the source address of a sending packet will be the one delegated from ISP2, that is 3ffe:1800:a:1:EUI64, because of rule 8 (longest matching prefix) in RFC 3484 [RFC3484]. Host-C is located somewhere in the Internet and has an IPv6 address 3ffe:503:c:1:EUI64. When Host-A sends a packet to Host-C, longest matching algorithm chooses 3ffe:1800:a:1:EUI64 for the source address. In this case, the packet goes through ISP1 and may be filtered by ISP1's ingress filter. Even if the packet isn't filtered by ISP1 fortunately, a return packet from Host-C won't possibly reach at Host-A, because the return packet is destined for 3ffe:1800:a:1:EUI64, which is closed from the Internet. In this case, source address based routing alone described in the previous section doesn't solve the problem. What is important is that each host chooses a correct source address for a given destination address as far as NAT doesn't exist in IPv6 world. 3. Concepts of Our Proposal In this document, we propose a method by which an ISP can distribute source address selection policies to each end node at a customer site. The policy information is particularly helpful to hosts in which multihoming is used, since an end node can use the destination address to select a source address that leads to a high probability of successful setup for the connection. An up-stream ISP is expected to use DHCPv6 Prefix Options [RFC3633] to delegate a certain portion of the IPv6 address space to its subscribers. We propose a DHCPv6 new option, which contains a per- delegating-prefix address-selection policy. By making use of this option, an ISP can inform its customers of an address block that can be reached through the ISP and of a corresponding source address of packets, that is, a source address that must be used to reach the given block. This is simply achieved through delegation of the delegated source-address prefix and policy by the ISP. The gateway router of a customer's site receives the delegated prefix and address-selection policy mentioned above from its up-stream ISPs. The router in turn distributes this information to end nodes at the site. Here, we propose an extension to the ND6 Router Advertisement Message [RFC2461] and a DHCPv6 [RFC3315] new option to cover delivery of address-selection policy to the end nodes. The address-selection Matsumoto, et al. Expires August 1, 2005 [Page 5] Internet-Draft SAS Policy Distribution January 2005 policy delivered to an end node is stored in the form of a Policy Table as defined in RFC 3484 [RFC3484]. Once the above series of processes is complete, an end node can select an appropriate source address for a given destination address. Routing of an outgoing packet to the corresponding up-stream ISP can be implemented in several ways that avoids blocking of the packet by ingress filtering. One way is a routing method guided by the source address of the packet, which is sometimes called "policy routing". Another method uses destination address based routing with the aid of additional routing information. This mechanism is particularly effective when a site subscribes to an ISP or VPN service that provides connectivity to a certain closed network as described in the previous section. This is because selecting an appropriate source address for a given destination address is crucial in such a network environment. This approach gives end nodes an advance measure against connection setup failure. At the same time, an ISP can control incoming traffic from customers' sites, and the network managers of customers' sites can reflect their networking policy to some extent by configuring DHCPv6 or ND6 RA settings on routers. The last but not the least significant feature to note here is that this sequence of passing, processing, generation, and reflection of policy information can be made almost totally automatic from the viewpoint of customers. Matsumoto, et al. Expires August 1, 2005 [Page 6] Internet-Draft SAS Policy Distribution January 2005 4. Proposal Overview For Each Case 4.1 Case 1: Multihome Site with Global-Closed Mixed Connectivity Fig. 3 shows a multihome site that subscribes to two ISPs. One ISP provides global network connectivity and the other provides connectivity to a closed network but not to the Internet. This site has one border router, labeled Gateway here, and the router may be connected to up-stream ISPs through a physical or logical link, say PPPoE or an IPsec Tunnel. ============== | Internet | ============== | 2001:db8::/32 | 3ffe:1800::/32 +----+-+ +-+----+ | ISP1 | | ISP2 | (Closed Network / VPN tunnel ) +----+-+ +-+----+ | | 2001:db8:a::/48 | | 3ffe:1800:a::/48 (DHCP-PD') ++-------++ (DHCP-PD') | Gateway | +----+----+ | 2001:db8:a:1::/64 | 3ffe:1800:a:1::/64 | (RA'/DHCP') ------+---+---------- | +-+----+ 2001:db8:a:1:EUI64 | Host | 3ffe:1800:a:1:EUI64 +------+ [Fig. 3] 4.1.1 Description of Each Element i) ISP -> Gateway This figure shows that ISP1 has been allocated 2001:db8::/32 and ISP2 has been allocated 3ffe:1800::/32. Each ISP delegates part of its address block, called the "provider aggregatable (PA)" block, to this customer site. Here, ISP1 and ISP2 use DHCP-PD to delegate 2001:db8:a::/48 and 3ffe:1800:a::/48, respectively. In this document, we propose an extension to DHCP-PD, which is actually a new DHCP option and called DHCP-PD' here. DHCP-PD' gives DHCP servers (ISPs) functionality for delivering an address- Matsumoto, et al. Expires August 1, 2005 [Page 7] Internet-Draft SAS Policy Distribution January 2005 selection policy in combination with a delegated prefix to a client (gateway). In this example, ISP2 includes Address Addr. Sel. Policy 3ffe:1800:a::/48 ---- 3ffe:1800::/32 in the PD and address-selection policy options sent to the client. This means that the subscribers of ISP2 should use an address from the delegated range, that is, 3ffe:1800:a::/48, when communicating with 3ffe:1800::/32. Selection of an appropriate source address is very important, and this is particularly so when one of the subscribing networks is closed as in this example. This is simply because a return packet from the closed network can't possibly reach the session- originating host if the return packet is destined for an address beyond the range available to the closed ISP. ISP1 also uses DHCP-PD', in this case to deliver its address- selection policy to its customers. As ISP1 provides global network connectivity, the PD and policy options will take the following form. Address Addr-Sel. Policy 2001:db8:a::/48 --+-- 2001:db8::/32 +-- ::/0 (all address) This means that ISP1 can provide connectivity to 2001:db8::/32 and act as a transit point for any other address (::/0) in the Internet as long as the source address is that delegated by ISP1, namely 2001:db8:a::/48. Of course, ::/0 includes 2001:db8::/32, so 2001:db8::/32 isn't necessary information for down-stream users. Like this way, however, by announcing more specific network block than ::/0 as a policy to down-stream, it is more likely to be adopted by down-stream nodes. This is because conflicting policies will be probably discarded at end nodes and routers, as mentioned below in 4.2.1, and ::/0 is much more likely to conflict with other ISP's policy than 2001:db8::/32. ISPs often provides additional services, such as video streaming and homepage building tool, only to their customers. This kind of access control is easily implemented by announcing ISP's specific network block in their address-selection policies. With regard to backward compatibility, a normal DHCP-PD packet, which does not carry address-selection policy information of the above type, should be deemed to have ::/0 as its policy field. Matsumoto, et al. Expires August 1, 2005 [Page 8] ii) Gateway -> Host A gateway router receives address-delegation information and address-selection policy from up-stream ISPs, in turn delivering both to down-stream nodes. In this document, we propose DHCP new option and an extension to RA (Router Advertisement Message). We refer to these as DHCP' and RA', respectively. The gateway router combines information given by multiple up-stream ISPs and distributes the following information down-stream through DHCP' or RA'. Address Addr. Sel. Policy 1 2001:db8:a:1::/64 --+-- 2001:db8::/32 +-- ::/0 2 3ffe:1800:a:1::/64 ----- 3ffe:1800::/32 This is just the combination of the information from the two up- stream elements in the previous section, except that each advertising address prefix is 64 bits long. iii) Host When a host receives an RA' or DHCP' message from the site gateway, it configures addresses for each receiving network interface and reflects address-selection policy in its RFC3484-based policy table. In this example, we propose that the policy table should be configured as follows, by making use of the Label field defined in RFC3484, and the relation between address prefix and address- selection policy should be kept in this table. Prefix Pref. Label 2001:db8::/32 10 100 ::/0 10 100 2001:db8:a:1::/64 10 100 3ffe:1800::/32 10 200 3ffe:1800:a:1::/64 10 200 When this host sends a packet to, for example, 3ffe:1800:a::100, whose longest matching entry in this table is 3ffe:1800::/32, the host chooses the address beginning with 3ffe:1800:a:1:: as the source address. The source-address selection algorithm will select the longest entry that is a candidate source-address range and has the same label as the longest matching address for the destination address. In the same way, the source address of a packet destined for 2001:db8::/32 or 2002::/16 will be 2001:db8:a:1:EUI64. Preference values are only used in the selection of destination addresses. This document does not include an algorithm for Matsumoto, et al. Expires August 1, 2005 [Page 9] Internet-Draft SAS Policy Distribution January 2005 determining preference values. iv) Gateway As well as delivering addresses and policy information to hosts through RA' or DHCP', the gateway is in charge of forwarding packets according to policy information distributed by up-stream ISPs. One way of implementing such forwarding or routing, called policy routing, is based on the source addresses of out-going packets. Policy routing is illustrated in the table below. Src. Next Hop 2001:db8:a:1::/64 ISP1 3ffe:1800:a:1::/64 ISP2 This kind of routing method, however, isn't so common for consumer network routers. Even if this technique is implemented, it may degrade packet forwarding performance seriously when it doesn't have hardware acceleration support. One alternative for policy routing is to use a routing protocol or some similar protocols and give a consumer network gateway as much routing information as the gateway can do destination address based routing. In this example, the routing table of the gateway looks like this. Dst. Next Hop 2001:db8::/32 ISP1 ::/0 ISP1 3ffe:1800::/32 ISP2 4.1.2 Discussion The benefits of this scheme are very clear. Every end node can determine which source address should be used and can send packets without a risk of failure due to ingress filtering or the limited reachability of a closed network. What should be discussed from here is the need for and implementation of policy enforcement to end nodes and the process of combining multiple address-selection policies. It's so hard to combine two policies automatically when a policy coming from an ISP conflicts with another ISP's policy. We may also have to think about combining or pruning algorithm to contain too much policy information in one packet. Matsumoto, et al. Expires August 1, 2005 [Page 10] Internet-Draft SAS Policy Distribution January 2005 4.2 Case 2: Host with Multiple Addresses and Connectivity to Two Global Networks ================== | Internet | ================== | | 2001:db8::/32 | | 3ffe:1800::/32 +----+-+ +-+----+ | ISP1 | | ISP2 | +----+-+ +-+----+ | | 2001:db8:a::/48 | | 3ffe:1800:a::/48 (DHCP-PD') ++-------++ (DHCP-PD') | Gateway | +----+----+ | 2001:db8:a:1::/64 | 3ffe:1800:a:1::/64 | (RA'/DHCP') ------+---+---------- | +-+----+ 2001:db8:a:1:EUI64 | Host | 3ffe:1800:a:1:EUI64 +------+ [Fig. 4] Fig. 4 shows a host with multiple addresses that subscribes to two ISPs for connectivity to the Internet. The manner of address delegation and allocation is as described in the previous example. 4.2.1 Description of Each Element i) ISP -> Gateway The difference between this and the previous example is that ISP2 provides global network connectivity, so the DHCP-PD' address- selection policy option for ISP2 includes an additional entry. Address Addr. Sel. Policy 3ffe:1800:a::/48 --+-- 3ffe:1800::/32 +-- ::/0 ii) Gateway -> Host As both ISPs provide global network connectivity, the policy for address-selection from the gateway router to the end nodes is of the form shown below. Matsumoto, et al. Expires August 1, 2005 [Page 11] Internet-Draft SAS Policy Distribution January 2005 Address Addr. Sel. Policy 1 2001:db8:a:1::/64 --+-- 2001:db8::/32 +-- ::/0 2 3ffe:1800:a:1::/64 --+-- 3ffe:1800::/32 +-- ::/0 (deleted) Note that the gateway is notified of an address-selection policy that includes prefix ::/0 by both ISPs. A policy table cannot have multiple entries whose prefixes are the same and labels aren't the same, which we call conflicting policies. Though the next section includes further statements about merging conflicting policies, there are basically two solutions for this issue: to remove all the conflicting policies or to choose one. Here, we continue the description of this example with the latter solution, so the second entry above is removed here and not forwarded down-stream. iii) Host Each end node will have the following address-selection policy table. Prefix. Pref. Label 2001:db8::/32 10 100 ::0 10 100 2001:db8:a:1::/64 10 100 3ffe:1800::/32 10 200 3ffe:1800:a:1::/64 10 200 It doesn't have any conflicting entries anymore, owing to the conflict removal at the gateway. Thus, end nodes can determine a source address for any destination addresses without any trouble. iv) Gateway If you remove conflicting source address selection policies for ::/0 and choose one ::/0 policy, the gateway can do destination address based routing. The routing table at the gateway looks like this. Dst. Next Hop 2001:db8::/32 ISP1 ::/0 ISP1 3ffe:1800::/32 ISP2 Here, we assume that end nodes select an appropriate source address for any destination addresses by the aid of distributed source address selection policy. So, destination address based routing suffices in this case. Matsumoto, et al. Expires August 1, 2005 [Page 12] Internet-Draft SAS Policy Distribution January 2005 4.2.2 Discussion One of the benefits of having an ISP provide address-selection policy to its customers is that it can explicitly check incoming packets to see if it is delegated their source addresses. Delivery of an address-selection policy makes the following mechanisms possible. - Since end nodes and routers in a multihoming site are given some kind of routing information, they can select the route expected to be optimal. In the above example, end nodes can communicate with servers of the ISPs without any circumvention. - Another possible usage of this framework is notification of security policy. ISPs commonly apply IP-address-based filtering to packets that attempt access to their services, such as POP, SMTP and Web content, partly for security reasons and partly as a value- added service for their customers. 4.3 Case 3: A Host Directly Connected to Multiple ISPs ================== | Internet | ================== | | 2001:db8::/32 | | 3ffe:1800::/32 | | 2001:db8:a::/48 | | 3ffe:1800:a::/48 (DHCP-PD') +----+-+ +-+----+ (DHCP-PD') | GW1 | | GW2 | +----+-+ +-+----+ 2001:db8:a:1::/64 | | 3ffe:1800:a:1::/64 (RA'/DHCP') | | (RA'/DHCP') -----+---+---+----- | 2001:db8:a:1:EUI64 +--+---+ 3ffe:1800:a:1:EUI64 | Host | +------+ [Fig. 5] This example shows an end node directly connected to two ISPs, both of which provide global network connectivity. This case also has source address selection problem. Even if a host has enough knowledge about up-stream network addresses and routes, a host in this site cannot select an appropriate source address for a given destination address, as we've mentioned in the problem statement section. Matsumoto, et al. Expires August 1, 2005 [Page 13] Internet-Draft SAS Policy Distribution January 2005 [I-D.ietf-ipv6-router-selection] defines another Neighbor Discovery Router Advertisement option for distributing routing information. In a case that a host has two network interfaces and is connected to gateways on a separate link, routing information suffices for choosing a correct source address. In a site like this, however, a host should store relationships between routing information and source address selection. So, in this kind of site, it seems to be better to use both router-selection mechanism, for distributing routing information, and our mechanism, for distributing source address selection policy. In case gateways are under your control, there is one alternative approach. It is to redirect packets with a wrong source address at gateways. 5. Who merges conflicting policies and how ? Another discussion topic should be about merging method of conflicting policies and who merges them. As far as an end node cannot have or make use of multiple source address selection policy entry for the same prefix, somebody has to merge them into one policy. There may be three cases for this issue; the site exit gateway does the merging job, end nodes do and both gateways and end nodes do. The management cost of a site might be relatively low, if you let a gateway to decide which policy to choose, in that you have only to configure the gateway. In contrast, if you give end nodes all the information the gateway received, you can let each end node to choose which source address selection policy to apply and to select which access-line to use. This means, at the same time, you have to configure each end node. Even in such a site that a gateway removes policy conflicts, an end node should be capable of receiving and manipulating conflicting policies in case that an additional gateway gets into a local link. 6. Failure Recovery When one of the links to up-stream ISPs has network trouble and the consumer gateway detects it, the gateway can take the following responses. 6.1 Stop advertising "Stop advertising IPv6 address prefix of the ISP in trouble." Matsumoto, et al. Expires August 1, 2005 [Page 14] Internet-Draft SAS Policy Distribution January 2005 If the address is assigned by Router Advertisement, this doesn't have effects on source address selection immediately, because IPv6 address has relatively long valid and preferred lifetime. 6.2 Address Revocation "Revoke an address delegated by an ISP in trouble." If IPv6 address is assigned to end nodes by DHCPv6, the gateway (DHCPv6 Server) can revoke those addresses that is delegated by a troubled ISP in a reasonably short time. 6.3 Policy Modification "Distribute modified source address selection policy that prevents end nodes from using a certain address." By distributing, for example, the following source address selection policy to end nodes, the gateway can control end hosts' address selection quickly. Prefix. Pref. Label 2001:db8::/32 10 100 ::0 10 100 2001:db8:a:1::/64 10 100 3ffe:1800::/32 10 100 3ffe:1800:a:1::/64 10 200 In this case, this host doesn't use the address 3ffe:1800:a:1:EUI64, except when it communicate with hosts on the same link. You may argue that Router Advertisement is essentially a rather static protocol and isn't suitable for this kind of dynamic configuration modification. However, it seems also to be true that these failure recovery methods are useful enough. We basically leave this topic to an operational issue. 7. Solution Comparison 7.1 Site Local Address One alternative method for this approach is to use site-local address for closed network ISP. The site-local address, however, is deprecated and isn't recommended to use anymore. The newly proposed site-local address, what we call Unique Local IPv6 Unicast Address [I-D.ietf-ipv6-unique-local-addr], isn't appropriate for such kind of use as this, because the address block size of it (/48) is too small for ISPs to delegate a certain size of IPv6 address block to each Matsumoto, et al. Expires August 1, 2005 [Page 15] Internet-Draft SAS Policy Distribution January 2005 customer. 7.2 Router Selection Router Selection [I-D.ietf-ipv6-router-selection] internet-draft is a proposal for introducing new options for Router Advertisement. As it is mentioned in section 4.3, this is a solution especially for those IPv6 nodes that has multiple network interfaces and assigned one IPv6 address for each network interface. Our proposal and this draft surely has close relationship with each other, but our scope of problem cannot be resolved only by this mechanism. 7.3 Routing Protocol Based Policy Distribution Another alternative might be such a modified form of routing protocol, so that it can store relationships of routes and source address selection policy. However, it seems to be a big drawback that consumer site gateway has to support a dynamic routing protocol. This can bring a big impact on both consumer site gateways and a provider edge routers. 8. Security Considerations With regard to the possibility of traffic abduction through the announcement of a bogus policy, this scheme seems to neither lower nor raise the security level obtained by the existing base-protocols, such as DHCP-PD, DHCP and RA. However, it does 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. 9. Revision History The previous revision of this document is "draft-arifumi-multi6-sas-policy-dist-00.txt". [I-D.arifumi-multi6-sas-policy-dist] Here lists differences from it. o Section 2,5,6,7,9 are added. o We removed descriptions that show dependency on source address base routing. o 3rd case in section 4 is changed to one network interface host from two. o A little description about merging conflicting policies is added to 2nd case in section 4. 10. IANA Considerations Matsumoto, et al. Expires August 1, 2005 [Page 16] Internet-Draft SAS Policy Distribution January 2005 This document has no actions for IANA. 11. Acknowledgement Many thanks to Iljitsch, Changming and Shin Miyagawa for detailed feedbacks and discussions on this document. We really appreciate all the members in our laboratory for their contributions. 12. References 12.1 Normative References [I-D.ietf-ipv6-router-selection] Draves, R. and D. Thaler, "Default Router Preferences and More-Specific Routes", draft-ietf-ipv6-router-selection-07 (work in progress), January 2005. [I-D.ietf-ipv6-unique-local-addr] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", draft-ietf-ipv6-unique-local-addr-09 (work in progress), January 2005. [RFC2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. [RFC2991] Thaler, D. and C. Hopps, "Multipath Issues in Unicast and Multicast Next-Hop Selection", RFC 2991, November 2000. [RFC2992] Hopps, C., "Analysis of an Equal-Cost Multi-Path Algorithm", RFC 2992, November 2000. [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. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. 12.2 Informative References [I-D.arifumi-multi6-sas-policy-dist] Matsumoto, A., "Source Address Selection Policy Distribution for Multihoming", Matsumoto, et al. Expires August 1, 2005 [Page 17] Internet-Draft SAS Policy Distribution January 2005 draft-arifumi-multi6-sas-policy-dist-00 (work in progress), October 2004. Authors' Addresses Arifumi Matsumoto NTT PFLab Midori-Cho 3-9-11 Mitaka City, Tokyo Prefecture 180-8585 JP Phone: +81 422 59 3334 EMail: arifumi@nttv6.net Tomohiro Fujisaki Midori-Cho 3-9-11 Mitaka City, Tokyo Prefecture 180-8585 JP Phone: +81 422 59 7351 EMail: fujisaki@syce.net Hirotaka Matsuoka Midori-Cho 3-9-11 Mitaka City, Tokyo Prefecture 180-8585 JP Phone: +81 422 59 4949 EMail: matsuoka@syce.net Jun-ya Kato Midori-Cho 3-9-11 Mitaka City, Tokyo Prefecture 180-8585 JP Phone: +81 422 59 2939 EMail: kato@syce.net Matsumoto, et al. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Matsumoto, et al. Expires August 1, 2005 [Page 19]