Network Working Group B. Sarikaya Internet-Draft F. Xia Expires: November 8, 2007 Huawei USA May 7, 2007 DHCPv6 or AAA Based Home Network Prefix Delegation for PMIPv6 and MIPv6 draft-sarikaya-netlmm-prefix-delegation-00.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 November 8, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Sarikaya & Xia Expires November 8, 2007 [Page 1] Internet-Draft Prefix Delegation May 2007 Abstract In Mobile IPv6 and Proxy Mobile IPv6, one prefix can only be assigned to one mobile node by the home agent/ local mobility anchor (HA/LMA) and different mobile nodes can not share this home network prefix. Managing per-MN home network prefixes is likely to increase the processing load at the HA/LMA. Based on the idea that Dynamic Host Configuration Protocol for IPv6 (DHCPv6) servers as well as Authentication, Authorization and Accounting (AAA) servers can manage prefixes, we propose a new technique in which HA/LMA offloads delegation and release tasks of the prefixes to the DHCPv6/AAA server. HA/LMA requests a prefix for an incoming mobile node to the DHCPv6/AAA server. Based on this prefix, the mobile node can create a home address. When the mobile station leaves the network, the prefix is returned to the DHCPv6/AAA server. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. PMIPv6 Home Network Prefix Delegation . . . . . . . . . . . . 4 4. Mobile IPv6 Home Network Prefix Delegation . . . . . . . . . . 8 5. Prefix Release Procedure . . . . . . . . . . . . . . . . . . . 9 6. Miscellaneous Considerations . . . . . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 11 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 10.1. Normative References . . . . . . . . . . . . . . . . . . 12 10.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Sarikaya & Xia Expires November 8, 2007 [Page 2] Internet-Draft Prefix Delegation May 2007 1. Introduction Proxy Mobile IPv6 (PMIPv6) provides network-based mobility solution to the mobile nodes (MN). MN configures its interface with an address from the home network prefix (HNP) topologically anchored at MN's local mobility anchor (LMA). PMIPv6 adopted per-MN prefix model where a prefix is only assigned to one MN. Different MNs can not share a prefix, and an MN can have multiple prefixes. The same applies to Mobile IPv6 where due to multi-link subnet issues per-MN prefixes must be used in assigning home link prefixes. However, in per-MN prefix model, prefix management is an issue. When an MN enters the network, its HA or LMA requests one or more prefixes for the MN for MIPv6 or PMIPv6, respectively. The prefixes should be released when the MN leaves the network. When an operator wants to renumber its network, the prefixes with different lifetime are advertised to the MN. Identity Association for Prefix Delegation (IA_PD) Option enables DHCP messages to carry IPv6 prefixes. The procedure for prefix delegation with DHCP which is independent of address assignment with DHCP has been defined in [RFC3633]. Therefore DHCPv6 provides a way to manage the prefixes. At the same time, AAA protocols, RADIUS or Diameter, can also be used for prefix allocation as defined in [RFC4818]. In this document we propose DHCPv6 or AAA based home network prefix allocation to MIPv6/PMIPv6 MNs. Section 3 describes PMIPv6 home network prefix allocation, Section 4 describes Mobile IPv6 home link prefix allocation, Section 5 describes how prefixes are released and Section 6 presents miscellaneous considerations that apply. Sarikaya & Xia Expires November 8, 2007 [Page 3] Internet-Draft Prefix Delegation May 2007 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119]. This document uses the terminology defined in [RFC3315], [RFC3633]. All MIPv6 related terms are defined in [RFC3775] and PMIPv6 related terms are defined in [I-D.ietf-netlmm-proxymip6]. 3. PMIPv6 Home Network Prefix Delegation We first describe HNP allocation without policy profile/ store (defined in [I-D.ietf-netlmm-proxymip6]) followed by policy store based HNP allocation using DHCP or AAA. MN MAG LMA DHCPS |------>| | | 1. RtSol | |------->| | 2. PBU (HNP=0) | | |------->| 3. DHCP Solicit | | |<-------| 4. DHCP Advertise | | |------->| 5. DHCP Request (HNP) | | |<-------| 6. DHCP Reply (HNP) | |<-------| | 7. PBA (HNP) |<------| | | 8. RA(HNP) |------>| | | 9. DAD NS Figure 1: Prefix request procedure 1 Figure 1 illustrates the scenario where MN is assigned a home network prefix without a policy store. In this scenario, LMA has a DHCP Client and DHCP Server is connected directly. DHCP messages need to be relayed using DHCP relay function in the LMA if the LMA and DHCP server are not connected directly. 1. An MN solicits a router advertisement (RtSol) for stateless address configuration. 2. Mobile Access Gateway (MAG) sends Proxy Binding Update (PBU) message to LMA and with HNP to zero. 3. LMA as the requesting router initiates DHCP Solicit procedure to request prefixes for the MN. LMA creates and transmits a Solicit message as described in sections 17.1.1, "Creation of Solicit Messages" and 17.1.2, "Transmission of Solicit Messages" of RFC 3315. LMA creates an IA_PD and assigns it an IAID. LMA MUST include the IA_PD option in the Solicit message. Sarikaya & Xia Expires November 8, 2007 [Page 4] Internet-Draft Prefix Delegation May 2007 4. The DHCP server as the delegating router sends an Advertise message to LMA in the same way as described in section 17.2.2, "Creation and transmission of Advertise messages" of RFC 3315. 5. LMA uses the same message exchanges as described in section 18, "DHCP Client-Initiated Configuration Exchange" of RFC 3315 to obtain or update prefixes from a DHCP server. LMA and the DHCP server use the IA_PD Prefix option to exchange information about prefixes in much the same way as IA Address options are used for assigned addresses. 6. LMA stores the prefix information it received in the Reply message. 7. LMA replies PBU with Proxy Binding Acknowledgement (PBA) and sets MN's prefix to HNP field of PBA. 8. MAG advertises prefixes to MN with Router Advertisement (RA) for stateless address configuration. 9. The MN starts verifying address uniqueness by sending a Duplicate Address Detection (DAD) Neighbor Solicitation (NS) message. The corresponding procedure for AAA-based prefix delegation is shown in Figure 2. MN MAG LMA AAA |------>| | | 1. RtSol | |------->| | 2. PBU (HNP=0) | | |------->| 3. AA-Request | | |<-------| 4. AA-Answer (HNP) | |<-------| | 5. PBA (HNP) |<------| | | 6. RA(HNP) |------>| | | 7. DAD NS Figure 2: Prefix request procedure 2 [RFC4818] defines a RADIUS attribute called Delegated-IPv6-Prefix that carries an IPv6 prefix to be delegated. This attribute is usable within either RADIUS or Diameter. The procedure is shown in Figure 2 and explained below. 1. MN solicits a router advertisement. 2. MAG sends PBU to LMA and sets HNP to zero. 3. LMA as Diameter client sends AA-Request message with an MN's information to Diameter server. 4. If the MN passes the authentication, the Diameter server sends AA-Answer message with prefix information to the LMA. The Delegated-IPv6-Prefix attribute MAY appear in an AA-Request packet as a hint by the LMA to the Diameter server that it would prefer a prefix, for example, a /48 prefix. The Diameter server MAY delegate a /64 prefix which is an extension of the /48 prefix in an AA-Request message containing Delegated-IPv6-Prefix Sarikaya & Xia Expires November 8, 2007 [Page 5] Internet-Draft Prefix Delegation May 2007 attribute. The attribute can appear multiple times when RADIUS server assigns multiple prefixes to MN. 5. Step 7 in Figure 1. 6. Step 8 in Figure 1. 7. Step 9 in Figure 1. Policy store based home network prefix allocation using DHCP can be done as shown in Figure 3. Policy store contains parameters such as the mobile node's home network prefix, permitted address configuration modes, roaming policy related and other parameters. MN MAG LMA DHCPS AAA |-------|--------|------- |--------| 1. Network entry | | |<-------|--------| 2. AAAH-HA Protocol | | |------->| | 3. DHCP Solicit | | |<-------| | 4. DHCP Advertise | | |------->| | 5. DHCP Request (HNP) | | |<-------| | 6. DHCP Reply (HNP) | | |--------|------->| 7. AAAH-HA Protocol | | | | | 8. HNP to MAG with |-------|--------|------- |--------| Successful network entry |<------| | | | 9. RA (HNP) |------>| | | | 10. DAD NS | |------->| | | 11. PBU (HNP) | |<-------| | | 12. PBA | | | | | Figure 3: Prefix request procedure 3 1. An MN boots up in the network and goes through several EAP exchanges. DHCP Server in Figure 3 is not involved in the network entry procedures. 2. The network asks the home agent/ local mobility agent for the home network prefix of MN. 3. Step 3 in Figure 1. 4. Step 4 in Figure 1. 5. Step 5 in Figure 1. 6. Step 6 in Figure 1. 7. LMA replies with MN's prefix. 8. Successful network entry terminates and MAG gets HNP. 9. MAG advertises prefixes to MN with RA for stateless address configuration. 10. The MN starts verifying address uniqueness by sending a DAD NS. 11. MAG sends PBU with HNP assigned. 12. LMA replies with PBA and establishes MAG-LMA tunnel. Policy store based home network prefix allocation can be done by AAA server. The procedure is shown in Figure 4. Sarikaya & Xia Expires November 8, 2007 [Page 6] Internet-Draft Prefix Delegation May 2007 MN MAG LMA AAA |-------|--------|---------| 1. Network entry | | |<--------| 2. AAAH-HA Protocol | | |-------->| 3. AA-Request | | |<--------| 4. AA-Answer | | |-------->| 5. AAAH-HA Protocol | | | | 6. HNP to MAG with |-------|--------|---------| Successful network entry |<------| | | 7. RA (HNP) |------>| | | 8. DAD NS | |------->| | 9. PBU (HNP) | |<-------| | 10. PBA Figure 4: Prefix request procedure 4 1. An MN boots up in the network and goes through several EAP exchanges. 2. The network asks the home agent/ local mobility agent for the home network prefix hint of MN. 3. Step 3 in Figure 2. 4. Step 4 in Figure 2. 5. LMA confirms MN's prefix. 6. Successful network entry terminates and MAG gets HNP. 7. MAG advertises prefixes to MN with RA for stateless address configuration. If stateful address configuration is used MAG sends DHCP reply with MN's home address assigned from the home network prefix. 8. The MN starts verifying address uniqueness by sending a DAD NS. 9. MAG sends PBU with HNP assigned. 10. LMA replies with PBA and establishes MAG-LMA tunnel. If stateful address configuration is used in PMIPv6 links, prefix allocation using DHCPv6 can be done as shown in Figure 5. MN MAG LMA DHCPS AAA |-------|--------|------- |--------|1. Network entry | | |<-------|--------|2. AAAH-HA Protocol | | |------->| |3. DHCP Solicit | | |<-------| |4. DHCP Advertise | | |------->| |5. DHCP Request (HNP) | | |<-------| |6. DHCP Reply (HNP) |-------|--------|------- |--------|7. Successful network entry |------>| | | |8. DHCP Request | |------->| | |9. PBU (HNP=0) | |<-------| | |10. PBA (HNP) |<------| | | |11. DHCP Reply Figure 5: Prefix request procedure 5 Sarikaya & Xia Expires November 8, 2007 [Page 7] Internet-Draft Prefix Delegation May 2007 In Steps 1-7, MN does network entry and LMA assigns its HNP using DHCPv6. In Step 8, MN requests an address from the local DHCP proxy/ server colocated in MAG. MAG sends PBU to LMA with HNP set to zero in Step 9 and LMA replies with PBA and sets its HNP parameter in Step 10. DHCP Proxy assigns MN-HoA from this prefix and sends it to MN in DHCP Reply in Step 11. If stateful address configuration is used in PMIPv6 links, prefix allocation using AAA can be done as shown in Figure 6. MN MAG LMA DHCPS AAA |-------|--------|------- |--------|1. Network entry | | |<-------|--------|2. AAAH-HA Protocol | | |------->| |3. AA-Request | | |<-------| |4. AA-Answer |-------|--------|------- |--------|5. Successful network entry |------>| | | |6. DHCP Request | |------->| | |7. PBU (HNP=0) | |<-------| | |8. PBA (HNP) |<------| | | |9. DHCP Reply Figure 6: Prefix request procedure 6 In Steps 1-5, MN does network entry and LMA assigns its HNP using AAA. In Step 6, MN requests an address from the local DHCP proxy/ server colocated in MAG [I-D.sarikaya-dhc-proxyagent]. MAG sends PBU to LMA with HNP set to zero in Step 7 and LMA replies with PBA and sets its HNP parameter in Step 8. DHCP Proxy assigns MN-HoA from this prefix and sends it to MN in DHCP Reply in Step 9. When MN moves under a different MAG, DHCP Proxy continues to provide the same home address to MN. 4. Mobile IPv6 Home Network Prefix Delegation Home agents (HA) MUST use per-MN home network prefixes in order to avoid multi-link subnet issues. Prefix management becomes an issue for HAs. DHCPv6 or AAA based prefix delegation can be used for this purpose. Mobile IPv6 per-MN prefix delegation procedure is shown in Figure 7 using DHCPv6. Sarikaya & Xia Expires November 8, 2007 [Page 8] Internet-Draft Prefix Delegation May 2007 MN AR HA DHCPS AAA |-------|--------|--------|--------| 1. IKEv2 SA Establishment | |------->| | | 2. CFG_REQUEST | | |------->| | 3. DHCP Solicit | | |<-------| | 4. DHCP Advertise | | |------->| | 5. DHCP Request (HNP) | | |<-------| | 6. DHCP Reply (HNP) | |<-------| | | 7. CFG_REPLY (HoA) with |-------|--------|--------|--------| IKEv2 SA Establishment |<------| | | | 8. RA for CoA |------>| | | | 9. DAD NS for CoA Figure 7: Prefix request procedure 7 1. MN solicits security association establishment using IKEv2. 2. HA gets configuration request message [RFC4877]. 3. Step 3 in Figure 1. 4. Step 4 in Figure 1. 5. Step 5 in Figure 1. 6. Step 6 in Figure 1. 7. HA sends back the reply to configuration request with HoA. MN uses HoA in sending a Binding Update (BU) message to register its care of address. 8. The care of address configuration. 9. The care of address configuration. Note that home address can be assigned during the bootstrapping process and downloaded into the AR as part of the policy store. In this case, HA will be triggered by HAAA-HA protocol and HA MUST get a per-MN prefix from DHCP server using steps 3-6 in Figure 7 and MUST assign HoA from this prefix. MN can receive the bootstrapping parameters by sending DHCP Info- Request message and receiving DHCP Info-Reply message. MIPv6 per-MN prefix delegation procedure using AAA is similar to Figure 7 except that instead of Steps 3-6, Steps 3-4 in Figure 2 are executed. 5. Prefix Release Procedure Sarikaya & Xia Expires November 8, 2007 [Page 9] Internet-Draft Prefix Delegation May 2007 MN MAG LMA DHCPS |------>| | | 1. Network exit/deregistration | |------->| | 2. PBU (lifetime=0) | |<-------| | 3. PBA | | |------->| 4. DHCP Release (HNP) | | |<------ | 5. DHCP Reply | | | | Figure 8: PMIPv6 Prefix Release Prefixes can be released in two ways, prefix aging or DHCP release procedure. In the former way, a prefix SHOULD not be used by an MN when the prefix ages, and the DHCP Server can delegate it to another MN. A prefix lifetime is delivered from the DHCPv6 server to the requesting router (HA or LMA) through DHCP IA_PD Prefix option [RFC3633] and RA Prefix Information option [I-D.ietf-ipv6-2461bis]. We first describe PMIPv6 prefix release procedure followed by MIPv6 release procedure. Figure 8 illustrates how LMA releases prefixes to an DHCP Server: 1. An MN detachment signaling, such as switch-off or handover, triggers prefix release procedure. 2. MAG sends PBU with lifetime set to zero. 3. LMA replies with PBA. 4. LMA initiates a Release message to give back the prefixes to the DHCP server. 5. The server responds with a Reply message, and then the prefixes can be reused by other MNs. If PMIPv6 and MIPv6 are being used by the same MN and HA also supports LMA functionality as described in [I-D.devarapalli-netlmm-pmipv6-mipv6] the same binding cache entry for the MN is sometimes modified by the MN or by a MAG. Because of this, at Step 4 in Figure 8, if the HA colocated with LMA receives a MIPv6 registration message (BU), LMA MUST not release the prefix(es). In case of Mobile IPv6, Figure 9 can be used to release prefixes. MN HA DHCPS |------->| | 1. BU (lifetime=0) |<-------| | 2. BA | |------->| 3. DHCP Release (HNP) | |<-------| 4. DHCP Reply | | | Figure 9: MIPv6 Prefix release Sarikaya & Xia Expires November 8, 2007 [Page 10] Internet-Draft Prefix Delegation May 2007 HA MUST release MN's home link prefix when MN returns home and sends a Binding Update message with the lifetime set to zero and receives a Binding Acknowledgement (BA) message back. The prefix release signaling is as shown in Figure 9. If PMIPv6 and MIPv6 are being used by the same MN and LMA also supports HA functionality as described in [I-D.devarapalli-netlmm-pmipv6-mipv6] the same binding cache entry for the MN is sometimes modified by the MN or by a MAG. Because of this, at Step 3 in Figure 9, if the LMA colocated with HA receives a PMIPv6 registration PBU, HA MUST not release the prefix(es). For RADIUS, when the MN exits the network, the LMA release the MN's prefixes through Accounting Stop message [RFC2866]. For Diameter, the LMA release prefixes through Accounting-Request[RFC3588]. MAG MUST advertise the prefix(es) to MN in RA message. Site renumbering is an open issue for RADIUS/ Diameter protocols to manage prefixes. [RFC3576] MAY be used for renumbering. 6. Miscellaneous Considerations The considerations on how to generate IAIDs and to delegate prefixes described in [I-D.sarikaya-16ng-prefix-delegation] on the access routers (AR) apply here on the local mobility anchors (LMA) and the home agents (HA). 7. Security Considerations This draft introduces no additional messages. Comparing to [RFC3633], [RFC2865] and [RFC3588] there is no additional threats to be introduced. DHCPv6, RADIUS and Diameter security procedures apply. 8. IANA consideration None. 9. Acknowledgements 10. References Sarikaya & Xia Expires November 8, 2007 [Page 11] Internet-Draft Prefix Delegation May 2007 10.1. Normative References [I-D.ietf-ipv6-2461bis] Narten, T., "Neighbor Discovery for IP version 6 (IPv6)", draft-ietf-ipv6-2461bis-11 (work in progress), March 2007. [I-D.ietf-netlmm-proxymip6] Gundavelli, S., "Proxy Mobile IPv6", draft-ietf-netlmm-proxymip6-00 (work in progress), April 2007. [I-D.sarikaya-16ng-prefix-delegation] Sarikaya, B. and F. Xia, "Using DHCPv6 and AAA Server for Mobile Station Prefix Delegation", draft-sarikaya-16ng-prefix-delegation-01 (work in progress), March 2007. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000. [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 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. [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. Aboba, "Dynamic Authorization Extensions to Remote Authentication Dial In User Service (RADIUS)", RFC 3576, July 2003. [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko, "Diameter Base Protocol", RFC 3588, September 2003. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [RFC4818] Salowey, J. and R. Droms, "RADIUS Delegated-IPv6-Prefix Attribute", RFC 4818, April 2007. Sarikaya & Xia Expires November 8, 2007 [Page 12] Internet-Draft Prefix Delegation May 2007 10.2. Informative References [I-D.devarapalli-netlmm-pmipv6-mipv6] Devarapalli, V., "Proxy Mobile IPv6 and Mobile IPv6 interworking", draft-devarapalli-netlmm-pmipv6-mipv6-01 (work in progress), April 2007. [I-D.sarikaya-dhc-proxyagent] Sarikaya, B. and K. Chowdhury, "DHCP v4/v6 Proxy", draft-sarikaya-dhc-proxyagent-00 (work in progress), October 2006. [RFC4877] Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with IKEv2 and the Revised IPsec Architecture", RFC 4877, April 2007. Authors' Addresses Behcet Sarikaya Huawei USA 1700 Alma Dr. Suite 100 Plano, TX 75075 Email: sarikaya@ieee.org Frank Xia Huawei USA 1700 Alma Dr. Suite 100 Plano, TX 75075 Phone: +1 972-509-5599 Email: xiayangsong@huawei.com Sarikaya & Xia Expires November 8, 2007 [Page 13] Internet-Draft Prefix Delegation May 2007 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. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Sarikaya & Xia Expires November 8, 2007 [Page 14]