SEND Working Group P. Nikander (editor) Internet Draft October 17, 2002 draft-ietf-send-psreq-00.txt Expires: April 17, 2002 IPv6 Neighbor Discovery trust models and threats Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026. 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. Abstract The existing IETF standards specify that IPv6 Neighbor Discovery and Address Autoconfiguration mechanisms MAY be protected with IPsec AH. However, the current specifications limit the security solutions to manual keying due to practical problems faced with automatic key management. This document specifies three different trust models and discusses the threats pertient to IPv6 Neighbor Discovery. The purpose of this discussion is to define the requirements for Securing IPv6 Neigbor Discovery. draft-ietf-send-psreq-00.txt P. Nikander (editor) Table of Contents 1.0 Introduction 2.0 Previous Work 3.0 Trust models 3.1 Corporate Intranet Model 3.2 Public Wireless Network with an Operator 3.3 Ad Hoc Network 4.0 Threats on a (Public) Multi-Access Link 4.1 Non router/routing related threats 4.1.1 Neighbor Solicitation/Advertisement Spoofing 4.1.2 Neighbor Unreachability Detection (NUD) failure 4.1.3 Duplicate Address Detection DoS Attack 4.2 Router/routing involving threats 4.2.1 Malicious Last Hop Router 4.2.2 Good Router Goes Bad 4.2.3 Spoofed Redirect Message 4.2.4 Bogus On-Link Prefix 4.2.5 Bogus Address Configuration Prefix 4.2.6 Parameter Spoofing 4.3 Remotely exploitable attacks 4.3.1 Neighbor Discovery DoS Attack 4.4 Summary of the attacks 5.0 Security Considerations 6.0 Acknowledgements 7.0 References 8.0 Authors' Addresses 9.0 Copyright Statement 1.0 Introduction The IPv6 Neighbor Discovery [RFC2461] and Address Autoconfiguration [RFC2462] mechanisms are used by nodes in an IPv6 network to learn the local topology, including the IP to MAC address mappings for the local nodes, the IP and MAC addresses of the routers present in the local network, and the routing prefixes served by the local routers. The current specifications suggest that IPsec AH [RFC2402] MAY be used to secure the mechanisms, but does not specify how. It appears that using current AH mechanisms is problematic due to key management problems [IKE-ND]. To solve the problem, the Secure Neighbor Discovery (SEND) working group was chartered in fall 2002. The goal of the working group is to define protocol support for securing IPv6 Neighbor Discovery without requiring excessive manual keying. The purpose of this document is to define the types of networks the Secure IPv6 Neighbor Discovery mechanisms are expected to work, and the threats that the security protocol(s) must address. To fulfil this purpose, this document first defines three different trust models, roughly corresponding to secured corporate intranets, public wireless access networks, and pure ad hoc netwroks. After that, a number of threats is are discussed in the light of these trust models. The threat catalog is aimed to be exhaustive, but it draft-ietf-send-psreq-00.txt P. Nikander (editor) is likely that some threats are still missing. Thus, ideas for new threats to consider are solicited. This document occasionally discusses solution proposals, such as CGA [CGA] and ABK [ABK]. However, the discussion is solely for illustrative purposes. It is meant to give the readers a more concrete idea of some possible solutions. It does NOT indicate any preference on solutions on the behalf of the authors or the working group. 2.0 Previous Work The RFCs that specify the IPv6 Neighbor Discovery and Address Autoconfiguration protocols [RFC2461] [RFC2462] contain the required discussion of security in a Security Considerations section. Some of the threats identified in this document were raised in the original RFCs. The recommended remedy was to secure the involved packets with an IPsec AH header [RFC2402]. However, thas solution is not always possible due to key management problems. For example, a host attempting to gain access to a Public Access network may or may not have the required IPsec security associations set up with the network. In a roaming (but not necessarily mobile) situation, where a user is currently accessing the network through a service provider different from the home provider, it is not likely that the host will have been preconfigured with the proper mutual trust relationship for the foreign provider's network. As of today, any IPsec security association between the host and the last hop routers or other hosts on the link would need to be completely manually preconfigured, since the Neighbor Discovery and Address Autoconfiguration protocols deal to some extent with how a host obtains initial access to a link. Thus, if a security association is required for initial access and the host does not have that association, there is currently no standard way that the host can dynamically configure itself with that association, even if it has the necessary minimum prerequisite keying material. This situation could induce administration hardships when events such as re-keying occur. In addition, Neighbor Discovery and Address Autoconfiguration use a few fixed multicast addresses plus a range of 4 billion "solicited node" multicast addresses. A naive application of pre-configured SAs would require pre-configuring an unmanagable number of SAs on each host and router just in case a given solicited node multicast address is used. Preconfigured SAs are impractical for securing such a large potential address range. 3.0 Trust models When considering various security solutions for the IPv6 Neighbor Discovery (ND) [RFC2461], it is important to keep in mind the underlying trust models. The trust models defined in this section are used later in this document, when discussing specific threats. draft-ietf-send-psreq-00.txt P. Nikander (editor) Three different trust models are specified: 1. A model where all authenticated nodes trust each other. This model is thought to represent a situation where the nodes are under a single administration and form a closed or semi-closed group. A corporate intranet is a good example. 2. A model where there is a router trusted by the other nodes in the network. This model is thought to represent a public network run by an operator. The clients pay to the operator, have its credentials, and trust it to provide the service. The clients do not trust each other. 3. A model where the nodes do not directly trust each other at the IP layer. This model is considered suitable for e.g., ad hoc networks. 3.1 Corporate Intranet Model In a corporate intranet or other network where all nodes are under one administrative domain, the nodes may be considered to be reliable at the IP layer. Thus, once a node has been accepted to be a member of the network, it is assumed to behave in a trustworthy manner. Under this model, if the network is physically secured or if the link layer is cryptographically secured to the extend needed, no other protection is needed for IPv6 ND. For example, a wired LAN with 802.1x access control or a WLAN with 802.11i RNS/EAS may be considered secure enough, requiring no further protection under this trust model. On the other hand, if the network is not physically secured and the link layer does not have cryptographic protection, or if the cryptographic protection is not secure enough (e.g., just 802.1x and not 802.11i in a WLAN), the nodes in the network may be vulnerable to some or all of the threats outlined in Section 4.0. In such case some protection is desirable to secure ND. Providing such protection falls within the main initial focus of the SEND working group. As mentioned in Section 2.0, one possiblity would be to use IPsec AH with symmetric shared keys, known by all trusted nodes and by no outsiders. However, none of the currently standardised automatic key distribution mechanisms work right out-of-the-box. For further details, see [IKE-ND]. 3.2 Public Wireless Network with an Operator A scenario where an operator runs a public wireless (or wireline) network, e.g., a WLAN in a hotel, air port, or cafe, has a different trust model. Here the nodes may be assumed to trust the operator. However, they do not usually trust each other. Typically the router (or routers) fall under one administrative domain, and the client nodes each fall under its own administrative domain. draft-ietf-send-psreq-00.txt P. Nikander (editor) It is assumed that under this scenario the operator authenticates all the client nodes, or at least requires authorization in the form of a payment. At the same time, the clients must be able to authenticate the router and make sure that it belongs to the trusted operator. Depending on the link layer authentication protocol and its deployment, the link layer MAY take care of the mutual authentication. The link layer authentication protocol MAY allow the client nodes and the access router to create a security association. Notice that there exists authentication protocols, e.g., variants of EAP, that do not create secure keying material and/or do not allow the client to authenticate the network. In this scenario, cryptographically securing the link layer does not necessarily block all the threats outlined in Section 4.0; see the individual threat descriptions. Specifically, even in 802.11i RNS/EAP the broadcast and multicast keys are shared between all nodes. Even if the underlying link layer is aware of all the nodes' link layer addresses, and is able to check that no source addresses were falsified, there may still be vulnerabilities. There seems to be two ways to bring in security into this scenario. One is to enforce strong security between the clients and the access router, and make the access router aware of the IP layer protocol details. That is, the router would check ICMPv6 packet contents, and filter packets that contain information which does not match the network topology. The other way is to add cryptographic protection to the ICMPv6 packets carrying ND messages. 3.3 Ad Hoc Network In an ad hoc network, or any network without a trusted operator, none of the nodes trust each other. Since there are no a priori trust relationships, the nodes cannot rely on traditional authentication. However, it is still possible to use self-identifying mechanisms, such as Cryptographically Generated Addresses [CGA]. These allow the nodes to ensure that they are talking to the same nodes (as before) at all times, and that each of the nodes indeed have generated their IP address themselves and not "stolen" someone else's address. It may also be possible to learn the identities of any routers using various kinds of heuristics, such as testing the node's ability to convery cryptographically protected traffic towards a known and trusted node somewhere in the Internet. Methods like these seem to mitigate (but not completely block) some of the attacks outlined in the next section. 4.0 Threats on a (Public) Multi-Access Link In this section we discuss threats against the current IPv6 Neighbor Discovery mechanisms, when used in multi-access links. The threats are discussed in the light of the trust models defined in the previous section. draft-ietf-send-psreq-00.txt P. Nikander (editor) There are two general types of threats: 1) Redirect attacks in which a malicious node redirects packets away from the last hop router to another node on the link. 2) Denial of Service (DoS) attacks, in which a malicious node prevents communication between the node under attack and all other nodes, or a specific destination address. A redirect attack can be used for DoS purposes by having the node to which the packets were redirected drop the packets, either completely or by selectively forwarding some of them and not others. The subsections below identify specific threats for IPv6 network access. The threat descriptions are organized in three subsections. We first consider threats that do not involve routers or routing information, and only after then those that do. Finally, we consider threats that are remotely exploitable. All threats are discussed in the light of the trust models. 4.1 Non router/routing related threats In this section we discuss attacks against "pure" Neighbor Discovery functions, i.e., Neighbor Discovery, Neigbor Unreachability Discovery, and Address Autoconfiguration. 4.1.1 Neighbor Solicitation/Advertisement Spoofing Nodes on the link use Neighbor Solicitation and Adverticement messages to created bindings between IP addresses and MAC addresses. An attacking node can cause packets for legitimate nodes, both hosts and routers, to be sent to some other link-layer address. This can be done by either sending a Neighbor Solicitation with a different source link-layer address option, or sending a Neighbor Advertisement with a different target link-layer address option. The IP address could additionally be the subnet router anycast address, allowing the attacker to capture traffic to that address. The attack results because the Neighbor Cache entry with the new link-layer address overwrites the old. If the spoofed link-layer address is a valid one, as long as the attacker responds to the unicast Neighbor Solicitation messages sent as part of the Neighbor Unreachability Detection, packets will continue to be redirected. This is a redirect/DoS attack. This mechanism can be used for a DoS attack by specifying an unused link-layer address, however, the attack is of limited duration since after 30-50 seconds (with default timer values) the Neighbor Unreachability Detection mechanism will discard the bad link-layer address and multicast anew to discover the link-layer address. As a consequence, the attacker will need to keep responding with fabricated link layer addresses if it wants to maintain the attack beyond the timeout. draft-ietf-send-psreq-00.txt P. Nikander (editor) This threat involves Neighbor Solicitation and Neighbor Advertisement messages. This attack is not a concern if access to the link is restricted to trusted nodes. In the case just the operator is trusted, the nodes may rely on the operator to certify the address bindings for other local nodes. In the ad hoc network case, and optionally in the trusted operator case, the nodes may use self certifying techniques (e.g. CGA) to authorize address bindings. 4.1.2 Neighbor Unreachability Detection (NUD) failure Nodes on the link monitor the reachability of local destinations and routers with the Neighbor Unreachability procedure [RFC2461]. Normally the nodes rely on upper-layer information to determine whether peer nodes are still reachable. However, if there is a sufficiently long delay on upper-layer traffic, or if the node stops receiving replies from a peer node, the NUD procedure is invoked. The node first waits for a small random delay, and then sends a targeted NS to the peer node. If the peer is still reachable, it will reply with a NA. However, if the soliciting node receives no reply, it tries a few more times, eventually deleting the neighbor cache entry. If needed, this triggers the standard address resolution protocol. No higher level traffic can proceed if this procedure flushes out neighbor cache entries after determining (perhaps incorrectly) that the peer is not reachable. A malicious node may keep sending fabricated NAs in response to NUD NS messages. Unless the NA messages are cryptographically protected, the attacker may be able to distrupt communications for a long time using this technique. This is a DoS attack. This threat involves Neighbor Solicitation/Advertisement. This attack is not a concern if access to the link is restricted to trusted nodes. Under the two other trust models, a solution requires that the node performing NUD is able to make a disctinction between genuine and fabricated NA responses. 4.1.3 Duplicate Address Detection DoS Attack In networks where the entering hosts obtain their addresses using stateless address autoconfiguration [RFC2462], an attacking node could launch a DoS attack by responding to every duplicate address detection attempt by an entering host. If the attacker claims the address, then the host will never be able to obtain an address. This threat was identified in RFC 2462 [RFC2462]. This is a DoS attack. This attack involves Neighbor Solicitation/Advertisement. draft-ietf-send-psreq-00.txt P. Nikander (editor) This attack is not a concern if access to the link is restricted to trusted nodes. Under the two other trust models, a solution requires that the node performing DAD is able to verify whether the sender of the NA response is authorized to use the given IP address or not. In the trusted operator case, the operator may acts as an authorizer, keeping track of allocated addresses and making sure that no node may allocated more than a few (hundreds of) addresses. In the ad noc network case one has to structure the addresses in such a way that self authorization is possible. CGA [CGA] provides one possible way to achieve that. 4.2 Router/routing involving threats In this section we consider threats pertient to router discovery or other router assisted/related mechanisms. 4.2.1 Malicious Last Hop Router This threat was identified in [MIP_TH], but was classified as a general IPv6 threat and not specific to Mobile IPv6. It is also identified in [RFC2461]. This threat is a redirect/DoS attack. An attacking node on the same subnet as a host attempting to discover a legitimate last hop router could masquerade as an IPv6 last hop router by multicasting legitimate-looking IPv6 Router Advertisements or unicasting Router Advertisements in response to multicast Router Advertisement Solicitations from the entering host. If the entering host selects the attacker as its default router, the attacker has the opportunity to siphon off traffic from the host, or mount a man-in-the-middle attack. The attacker could ensure that the entering host selected itself as the default router by multicasting periodic Router Advertisements for the real last hop router having a lifetime of zero. This may spoof the entering host into believing that the real access router is not willing to take any traffic. Once accepted as a legitimate router, the attacker could send Redirect messages to hosts, then disappear, thus covering its tracks. [XXX: The section above needs reconsideration. It appears that just sending an RA with a zero lifetime is not enough. New text is needed.] This threat involves Router Advertisement and Router Advertisement Solicitation. This attack is not a concern if access to the link is restricted to trusted nodes. In the case of a trusted operator, there must be a means for the nodes to make a distinction between trustworthy routers, run by the operator, and other nodes. There are currently no known solutions for the ad hoc network case, and the issue remains as a research question. draft-ietf-send-psreq-00.txt P. Nikander (editor) 4.2.2 Good Router Goes Bad In this attack, a router that previously was trusted is compromised. The attacks available are the same as those discussed in Section 4.2.1. This is a redirect/DoS attack. There are currently no known solutions for any of the presented three trust models. On the other hand, on a multi-router link one could imagine a solution involving revocation of router rights. The situation remains as a research question. 4.2.3 Spoofed Redirect Message The Redirect message can be used to send packets for a given destination to any link-layer address on the link. The attacker uses the link-local address of the current first-hop router in order to send a Redirect message to a legitimate host. Since the host identifies the message by the link-local address as coming from its first hop router, it accepts the Redirect. As long as the attacker responds to Neighbor Unreachability Detection probes to the link- layer address, the Redirect will remain in effect. This is a redirect/DoS attack. This threat involves Redirect messages. This attack is not a concern if access to the link is restricted to trusted nodes. In the case of a trusted operator, there must be a means for the nodes to make a distinction between trustworthy routers, run by the operator, and other nodes. There are currently no known solutions for the ad hoc network case, and the issue remains as a research question. 4.2.4 Bogus On-Link Prefix An attacking node can send a Router Advertisement message specifying that some prefix of arbitrary length is on-link. If a sending host thinks the prefix is on-link, it will never send a packet for that prefix to the router. Instead, the host will try to perform address resolution by sending Neighbor Solicitations, but the Neighbor Solicitations will not result in a response, denying service to the attacked host. This is a DoS attack. The attacker can use an arbitrary lifetime on the bogus prefix advertisement. If the lifetime is infinity, the sending host will be denied service until it loses the state in its prefix list e.g., by rebooting, or the same prefix is advertised with a zero lifetime. The attack could also be perpetrated selectively for packets destined to a particular prefix by using 128 bit prefixes, i.e. full addresses. This threat involves Router Advertisement messages. This attack is not a concern if access to the link is restricted to trusted nodes. In the case of a trusted operator, there must be a means for the nodes to make a distinction between trustworthy draft-ietf-send-psreq-00.txt P. Nikander (editor) routers, run by the operator, and other nodes. There are currently no known solutions for the ad hoc network case, and the issue remains as a research question. 4.2.5 Bogus Address Configuration Prefix An attacking node can send a Router Advertisement message specifying an invalid subnet prefix to be used by a host for address autoconfiguration. A host executing the address autoconfiguration algorithm uses the advertised prefix to construct an address [RFC2462], even though that address is not valid for the subnet. As a result, return packets never reach the host because the host's source address is invalid. This is a DoS attack. This attack has the potential to propagate beyond the immediate attacked host if the attacked host performs a dynamic update to the DNS based on the bogus constructed address. DNS update causes the bogus address to be added to the host's AAAA record in the DNS. Should this occur, applications performing name resolution through the DNS obtain the bogus address and an attempt to contact the host fails. However, well-written applications will fall back and try the other IP address in the AAAA RRset, which may be correct. This threat involves Router Advertisement messages. This attack is not a concern if access to the link is restricted to trusted nodes. In the case of a trusted operator, there must be a means for the nodes to make a distinction between trustworthy routers, run by the operator, and other nodes. There are currently no known solutions for the ad hoc network case, and the issue remains as a research question. 4.2.6 Parameter Spoofing IPv6 Router Advertisements contain a few parameters used by hosts when they send packets and to tell hosts whether or not they should perform stateful address configuration [RFC2461]. An attacking node could send out a valid-seeming Router Advertisement that duplicates the Router Advertisement from the legitimate default router, except the included parameters are designed to disrupt legitimate traffic. This is a DoS attack. Specific attacks include: 1) The attacker includes a Current Hop Limit of one or another small number which the attacker knows will cause legitimate packets to be dropped before they reach their destination. 2) The attacker implements a bogus DHCPv6 server or relay and the 'M' and/or 'O' flag is set, indicating that stateful address configuration and/or stateful configuration of other parameters should be done. The attacker is then in a position to answer the stateful configuration queries of a legitmate host with its own bogus replies. draft-ietf-send-psreq-00.txt P. Nikander (editor) This attack involves Router Advertisements. This attack is not a concern if access to the link is restricted to trusted nodes. In the case of a trusted operator, there must be a means for the nodes to make a distinction between trustworthy routers, run by the operator, and other nodes. There are currently no known solutions for the ad hoc network case, and the issue remains as a research question. 4.3 Remotely exploitable attacks 4.3.1 Neighbor Discovery DoS Attack In this attack, the attacking node begins fabricating addresses with the subnet prefix and continuously sending packets to them. The last hop router is obligated to resolve these addresses by sending neighbor solicitation packets. A legitimate host attempting to enter the network may not be able to obtain Neighbor Discovery service from the last hop router as it will be already busy with sending other solicitations. This DoS attack is different from the others in that the attacker may be off link. The resource being attacked in this case is the conceptual neighbor cache, which will be filled with attempts to resolve IPv6 addresses having a valid prefix but invalid suffix. This is a DoS attack. This attack involves Neighbor Solicitation. This attack does not directly involve the trust models presented. However, if access to the link is restricted to registed nodes, and the access router keeps track of nodes that have registered for access on the link, the attack may be trivially plugged. However, no such mechanisms are currently standardized. It is an open question whether the SEND WG should address this threat or not. draft-ietf-send-psreq-00.txt P. Nikander (editor) 4.4 Summary of the attacks Columns: N/R Neighbor Discovery (ND) or Router Discovery (RD) attack R/D Redirect/DoS (Redir) or just DoS attack Msgs Messages involved in the attack: NA, NS, RA, RS, Redir 1 Present in trust model 1 (corporate intranet) 2 Present in trust model 2 (public operator run network) 3 Present in trust model 3 (ad hoc network) Symbols in trust model columns: - The threat is not present + The threat is present and at least one solution is known R The threat is present but solving it is a research problem +-------+----------------------------+-----+-------+-------+---+---+---+ | Sec | Attack name | N/R | R/D | Msgs | 1 | 2 | 3 | +-------+----------------------------+-----+-------+-------+---+---+---+ | 4.1.1 | NS/NA spoofing | ND | Redir | NA NS | - | + | + | | 4.1.2 | NUD failure | ND | DoS | NA NS | - | + | + | | 4.1.3 | DAD DoS | ND | DoS | NA NS | - | + | + | +-------+----------------------------+-----+-------+-------+---+---+---+ | 4.2.1 | Malicious router | RD | Redir | RA RS | - | + | R | | 4.2.2 | Good router goes bad | RD | Redir | RA RS | R | R | R | | 4.2.3 | Spoofed redirect | RD | Redir | Redir | - | + | R | | 4.2.4 | Bogus on-link prefix | RD | DoS | RA | - | + | R | | 4.2.5 | Bogus address config prefix| RD | DoS | RA | - | + | R | | 4.2.6 | Parameter spoofing | RD | DoS | RA | - | + | R | +-------+----------------------------+-----+-------+-------+---+---+---+ | 4.3.1 | Remote ND DoS | ND | DoS | NS | + | + | + | +------------------------------------+-----+-------+-------+---+---+---+ draft-ietf-send-psreq-00.txt P. Nikander (editor) 5.0 Security Considerations This document discusses security threats to network access in IPv6. As such, it is concerned entirely with security. 6.0 Acknowledgements Thanks to Alper Yegin of DoCoMo Communications Laboratories USA for identifying the Neighbor Discovery DOS attack. We would also like to thank Tuomas Aura and Michael Roe of Microsoft Research Cambridge as well as Jari Arkko and Vesa-Matti Mntyl of Ericsson Research Nomadiclab for discussing some of the threats with us. 7.0 References [RFC2461] T. Narten, E. Nordmark, and W. Simson, "Neighbor Discovery for IP Version 6 (IPv6)," RFC2461, December, 1998. [RFC2462] Thomas, S., and Narten, T., "IPv6 Stateless Address Autoconfiguration," RFC 2462, December, 1998. [RFC2402] Kent, S., and Atkinson, R., "IP Authentication Header," RFC 2402, November 1998. [MIP_TH] Mankin, et. al., "Threat Models introduced by Mobile IPv6 and Requirements for Security in Mobile IPv6," draft-ietf-mobileip- mipv6-scrty-reqts-01.txt, a work in progress. [EAP] Blunk, L., and Vollbrecht, J., "PPP Extensible Authentication Protocol (EAP)," RFC 2284, March, 1998. [RFC2472] Haskin, D. and Allen, E., "IP Version 6 over PPP," RFC 2472, December, 1998. [DHCPv6] Droms, R., editor, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", draft-ietf-dhc-dhcpv6-20.txt, a work in progress. [ABK] J. Kempf, C. Gentry, A. Silverberg, "Securing IPv6 Neighbor Discovery Using Address Based Keys (ABKs)," work in progress, draft-kempf-secure-nd-00.txt, February 2002. [CGA] M. Roe, T. Aura, G. O'Shea, J. Arkko, "Authentication of Mobile IPv6 binding updates and acknowledgements," work in progress, draft-roe-mobileip-updateauth-02.txt, IETF Mobile IP WG, February 2002. [IKE-ND] J. Arkko, "Effects of ICMPv6 on IKE and IPsec Policies," work in progress, drat-arkko-icmpv6-ike-effects-02.txt, June 2002. draft-ietf-send-psreq-00.txt P. Nikander (editor) 8.0 Authors' Addresses Pekka Nikander (editor) Ericsson Research Nomadic Lab Phone: +358 9 299 1 FIN-02420 JORVAS Email: pekka.nikander@nomadiclab.com FINLAND James Kempf DoCoMo USA Labs 181 Metro Drive, Suite 300 Phone: +1 408 451 4711 San Jose, CA, 95110 Email: kempf@docomolabs-usa.com USA Erik Nordmark Sun Microsystems Laboratories Phone: +33 4 76 18 88 03 29, Chemin du Vieux Chene Fax: +33 4 76 18 88 88 38240 Meylan Email: erik.nordmark@sun.com France 9.0 Copyright Statement Copyright (c) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. SEND Working Group P. Nikander (editor) Internet Draft October 17, 2002 draft-ietf-send-psreq-00.txt Expires: April 17, 2002
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