Network work group Mach Chen Internet Draft Renhai Zhang Expires: December 2007 Huawei Technologies Co.,Ltd Category: Standards Track June 28, 2007 ISIS Traffic Engineering (ISIS-TE) Extensions in Support of Inter-AS Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering draft-chen-ccamp-isis-interas-te-extension-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 December 28, 2007. Abstract This document describes extensions to the ISIS Traffic Engineering (ISIS-TE) mechanisms to support Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering (TE) for multiple Autonomous Systems (ASes). It defines ISIS-TE extensions for the flooding of TE information about inter-AS links which can be used to perform inter-AS TE path computation. Mach & Renhai Expires December 28, 2007 [Page 1] Internet-Draft ISIS extensions for Inter-AS TE June 2007 Conventions used in this document 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 RFC-2119 [RFC2119]. Table of Contents 1. Introduction.................................................2 2. Problem statement............................................3 2.1. A Note on Non-Objectives................................3 2.2. Per-Domain Path Determination...........................4 2.3. Backward Recursive Path Computation.....................5 3. Extensions to ISIS-TE........................................6 3.1. Link Type sub-TLV.......................................6 3.2. Remote AS Number Sub-TLV................................7 3.3. Remote ASBR ID sub-TLV..................................7 3.4. Inter-AS reachability TLV...............................8 4. Procedure for Inter-AS TE Links..............................9 5. Security Considerations.....................................10 6. IANA Considerations.........................................10 6.1. Inter-AS Reachability TLV..............................10 6.2. Sub-TLVs for the Inter-AS Reachability TLV.............11 6.3. Sub-TLVs for the Extended IS Reachability TLV..........11 6.4. ISIS TE Link Type......................................11 7. Acknowledgments.............................................12 8. References..................................................12 8.1. Normative References...................................12 8.2. Informative References.................................12 Author's Addresses.............................................13 Intellectual Property Statement................................13 Disclaimer of Validity.........................................14 Copyright Statement............................................14 Acknowledgment.................................................14 1. Introduction [ISIS-TE] defines extensions to the ISIS protocol [ISIS] to support intra-area Traffic Engineering (TE). The extensions provide a way of encoding the TE information for TE-enabled links within the network (TE links) and flooding this information within an area. The Extended IS reachability TLV and Traffic Engineering Router ID TLV, which are defined in [ISIS-TE], are used to carry such TE information. The Extended IS reachability TLV has several nested sub-TLVs which describe the TE attributes for a TE link. Mach & Renhai Expires December 28, 2007 [Page 2] Internet-Draft ISIS extensions for Inter-AS TE June 2007 [ISIS-TE-V3] and [GMPLS-TE] define similar extensions to ISIS [ISIS] in support of IPv6 and GMPLS traffic engineering respectively. Requirements for establishing Multiprotocol Label Switching (MPLS) TE Label Switched Paths (LSPs) that cross multiple Autonomous Systems (ASes) are described in [INTER-AS-TE-REQ]. As described in [INTER-AS- TE-REQ], a method SHOULD provide the ability to compute a path spanning multiple ASes. So a path computation entity that may be the head-end Label Switching Router (LSR), an AS Border Router (ASBR), or a Path Computation Element (PCE [PCE]) needs to know the TE information not only of the links within an AS, but also of the links that connect to other ASes. In this document, some extensions to ISIS-TE are defined in support of carrying inter-AS TE link information for inter-AS Traffic Engineering. Three new sub-TLVs are added to the Extended IS reachability TLV, and a new TLV, which is referred to as inter-AS reachability TLV, is defined. The extensions are equally applicable to IPv4 and IPv6 as identical extensions to [ISIS-TE] and [ISIS-TE- V3]. The detailed definitions and procedures are discussed in the following sections. 2. Problem statement As described in [INTER-AS-TE-REQ], in the case of establishing an inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209] may include the following elements in the Explicit Route Object (ERO) in order to describe the path of the LSP: - a set of AS numbers as loose hops; and/or - a set of LSRs including ASBRs as loose hops. Two methods for determining inter-AS paths are currently discussed. The per-domain method [PD-PATH] determines the path one domain at a time. The backward recursive method [BRPC] uses cooperation between PCEs to determine an optimum inter-domain path. The sections that follow examine how inter-AS TE link information could be useful in both cases. 2.1. A Note on Non-Objectives It is important to note that this document does not make any change to the confidentiality and scaling assumptions surrounding the use of ASes in the Internet. In particular, this document is conformant to the requirements set out in [INTER-AS-TE-REQ]. Mach & Renhai Expires December 28, 2007 [Page 3] Internet-Draft ISIS extensions for Inter-AS TE June 2007 The following lists of features are explicit exclusions. o There is no attempt to distribute TE information from within one AS to another AS. o There is no mechanism proposed to distribute any form of TE reachability information for destinations outside the AS. o There is no proposed change to the PCE architecture or usage. o TE aggregation is not supported or recommended. o There is no exchange of private information between ASes. 2.2. Per-Domain Path Determination In the per-domain method of determining an inter-AS path for an MPLS- TE LSP, when an LSR that is an entry-point to an AS receives a PATH message from an upstream AS with an ERO containing a next hop that is an AS number, it needs to find which LSRs within the local AS are connected to the downstream AS so that it can compute a TE LSP segment across the AS to that LSR and forward the PATH message to the LSR and hence into the next AS. See the figure below for an example: R1------R3----R5-----R7------R9-----R11 | | \ | / | | | \ | ---- | | | \ | / | R2------R4----R6 --R8------R10----R12 : : <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> Figure 1: Inter-AS Reference Model The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are ASBRs in AS3. If an inter-AS TE LSP is planned to be established from R1 to R12, the AS sequence is limited as: AS1, AS2, AS3. Suppose that the Path message enters AS2 from R3. The next hop in the ERO shows AS3, and R5 must determine a path segment across AS2 to reach AS3. It has a choice of three exit points from AS2 (R6, R7, and R8) and it needs to know which of these provide TE connectivity to Mach & Renhai Expires December 28, 2007 [Page 4] Internet-Draft ISIS extensions for Inter-AS TE June 2007 AS3, and whether the TE connectivity (for example, available bandwidth) is adequate for the requested LSP. Alternatively, if the next hop in the ERO is the entry ASBR for AS3 (say R9), R5 needs to know which of its exit ASBRs has a TE link that connects to R9. Since there may be multiple exist ASBRs that are connected to R9 (both R7 and R8 in this example), R5 also needs to know the TE properties of the inter-AS TE links so that it can select the correct exit ASBR. Once the path message reaches the exit ASBR, any choice of inter-AS TE link can be made by the ASBR if not already made by entry ASBR that computed the segment. More details can be found in the Section 4.0 of [PD-PATH], which clearly points out why advertising of inter-AS links is desired. To enable R5 to make the correct choice of exit ASBR the following information is needed: o List of all inter-AS TE links for the local AS. o TE properties of each inter-AS TE link. o AS number of the neighboring AS connected to by each inter-AS TE link. o Identity (TE Router ID) of the neighboring ASBR connected to by each inter-AS TE link. In GMPLS networks further information may also be required to select the correct TE links as defined in [GMPLS-TE]. The example above shows how this information is needed at the entry point ASBRs for each AS (or the PCEs that provide computation services for the ASBRs), but this information is also needed throughout the local AS if path computation function is fully distributed among LSRs in the local AS, for example to support LSPs that have start points (ingress nodes) within the AS. 2.3. Backward Recursive Path Computation Another scenario using PCE techniques has the same problem. [BRPC] defines a PCE-based TE LSP computation method (called Backward Recursive Path Computation) to compute optimal inter-domain constrained MPLS-TE or GMPLS LSPs. In this path computation method, a specific set of traversed domains are assumed to be selected before Mach & Renhai Expires December 28, 2007 [Page 5] Internet-Draft ISIS extensions for Inter-AS TE June 2007 computation starts. Each downstream PCE in domain(i) returns a multipoint-to-point tree of potential paths to its upstream neighbor PCE in domain(i-1). Each tree consists of the set of paths from all Boundary Nodes located in domain(i) to the destination where each path satisfies the set of required constraints for the TE LSP (bandwidth, affinities, etc.). So a PCE needs to select Boundary Nodes (that is, ASBRs) that provide connectivity from the upstream AS. In order that the tree of paths provided by one PCE to its neighbor can be correlated, the identities of the ASBRs for each path need to be referenced, so the PCE must know the identities of the ASBRs in the remote AS reached by any inter-AS TE link, and, in order that it provides only suitable paths in the tree, the PCE must know the TE properties of the inter-AS TE links. Thus, to support Backward Recursive Path Computation the same information as listed in Section 2.2 is required. 3. Extensions to ISIS-TE Note that this document does not define mechanisms for distribution of TE information from one AS to another, does not distribute any form of TE reachability information for destinations outside the AS, does not change the PCE architecture or usage, does not suggest or recommend any form of TE aggregation, and does not feed private information between ASes. See section 2.1. In this document, three new sub-TLVs are added to the extended IS reachability TLV to carry the information about the neighboring AS, the remote ASBR ID and the Link Type of an inter-AS link. An new TLV, which is referred to as inter-AS reachability TLV, is defined to flood the information about the neighboring AS and the remote ASBR ID within a whole AS. 3.1. Link Type sub-TLV To identify a link as an inter-AS link and allow easy identification of these new advertisements, a new Link Type sub-TLV is added to the extended IS reachability TLV to identify the type of the links. The Link Type sub-TLV is TLV type 22 (which needs to be confirmed by IANA), and is one octet in length. The format of the link type sub- TLV is as follows: Mach & Renhai Expires December 28, 2007 [Page 6] Internet-Draft ISIS extensions for Inter-AS TE June 2007 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Type | +-+-+-+-+-+-+-+-+ The value of the Link Type for an inter-AS point-to-point link is 3 (which needs to be confirmed by IANA). The use of multi-access inter- AS TE links and intra-area TE links is for future study. 3.2. Remote AS Number Sub-TLV As described in [ISIS-TE], the Extended IS reachability TLV describes a single link and consists of a set of sub-TLVs. A new sub-TLV, the Remote AS Number sub-TLV is added to the extended IS reachability TLV when advertising inter-AS links. The Remote AS Number sub-TLV specifies the AS number of the neighboring AS to which the advertised link connects. The Remote AS number sub-TLV is TLV type 23 (which needs to be confirmed by IANA), and is four octets in length. The format is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote AS Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Remote AS number field has 4 octets. When two octets are used for the AS number, as in current deployments, the left (high-order) two octets MUST be set to zero. 3.3. Remote ASBR ID sub-TLV A new sub-TLV, which is referred to as the Remote ASBR ID sub-TLV, is added to the extended IS reachability TLV when advertising inter-AS links. The remote ASBR ID sub-TLV specifies the Router ID or TE Router ID of the remote ASBR to which the advertised inter-AS link connects, which provides a stable, routable identifier of the remote ASBR. Mach & Renhai Expires December 28, 2007 [Page 7] Internet-Draft ISIS extensions for Inter-AS TE June 2007 The Remote ASBR ID sub-TLV is TLV type 24 (which needs to be confirmed by IANA), and is four or sixteen octets in length. The format of the remote ASBR ID sub-TLV is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote ASBR ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ or 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote ASBR ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote ASBR ID (continued) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote ASBR ID (continued) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote ASBR ID (continued) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ If a router implements traffic engineering for IPv4, the length of the remote ASBR ID is four. If a router implements traffic engineering for IPv6, the length of the remote ASBR ID is sixteen. 3.4. Inter-AS reachability TLV The inter-AS reachability TLV has type 141 (which needs to be confirmed by IANA). This is an optional TLV, when needed, it is used to flood the reachability information of the inter-AS links within a whole AS. And such reachability information SHOULD include the neighboring AS number and the remote ASBR ID to which an inter-AS link connects. The inter-AS reachability TLV contains a data structure consisting of: Mach & Renhai Expires December 28, 2007 [Page 8] Internet-Draft ISIS extensions for Inter-AS TE June 2007 6 octets of System ID 1 octet of Pseudonode Number 1 octet flags 1 bit of up/down information 1 bit indicating the presence of sub-TLVs 6 bits reserved 1 octet of length of sub-TLVs 0-246 octets of sub-TLVs where each sub-TLV consists of a sequence of: 1 octet of sub-type 1 octet of length of the value field of the sub-TLV 0-244 octets of value In this document, two sub-TLVs are defined for the inter-AS Reachability TLV, they are: Sub-TLV type length Name 23 4 Remote AS number 24 4or16 Remote ASBR Identifier These two sub-TLVs have the same format and semantics as defined in Section 3.1 and section 3.2 of this memo. 4. Procedure for Inter-AS TE Links When TE is enabled on an inter-AS link and the link is up, the ASBR SHOULD advertise this link using the normal procedures for ISIS-TE [ISIS-TE]. When either the link is down or TE is disabled on the link, the ASBR SHOULD withdraw the advertisement. When there are changes to the TE parameters for the link (for example, when the available bandwidth changes) the ASBR SHOULD re-advertise the link, but the ASBR MUST take precautions against excessive re-advertisements. The information advertised comes from the ASBR's knowledge of the TE capabilities of the link, the ASBR's knowledge of the current status and usage of the link, and configuration at the ASBR of the remote AS number and remote ASBR TE Router ID. When the inter-AS reachability information needs to reach all routers(including area border routers, ASBRs, and PCEs) in the AS, the ASBR SHOULD carry the Remote AS sub-TLV and Remote ASBR ID sub- TLV in the inter-AS reachability TLV. As defined in Section 4.1 of [ISIS-TE], the inter-AS reachability TLV also defines an up/down bit to facilitate the redistribution of inter-AS reachability information Mach & Renhai Expires December 28, 2007 [Page 9] Internet-Draft ISIS extensions for Inter-AS TE June 2007 freely between level 1 and level 2. The semantics of the up/down bit in the new inter-AS reachability TLV are identical to the semantics of the up/down bit defined in [ISIS-TE]. That is, the up/down bit SHALL be set to 0 when the inter-AS reachability information first injected into ISIS [ISIS], and the up/dawn bit SHALL be set to 1 if the inter-AS reachability information needs to be advertised from high level to low level. Legacy routers receiving an advertisement for an inter-AS TE link are able to ignore it because they do not know the new TLV and sub-TLVs that are defined in Section 3 in this document. They will continue to flood the LSP, but will not attempt to use the information received as if the link were an intra-AS TE link. Routers or PCEs that are capable of processing advertisements of inter-AS TE links SHOULD NOT use such links to compute paths that exit an AS to a remote ASBR and then immediately re-enter the AS through another TE link. Such paths would constitute extremely rare occurrences and SHOULD NOT be allowed except as the result of specific policy configurations at the router or PCE computing the path. 5. Security Considerations The protocol extensions defined in this document are relatively minor and can be secured within the AS in which they are used by the existing ISIS security mechanisms. It should be noted, however, that some of the information included in these new advertisements(the remote AS number and the remote ASBR ID) are obtained from a neighboring administration and cannot be verified in anyway. Since the means of delivery of this information is likely to be part of a commercial relationship, the source of the information should be carefully checked before it is entered as configuration information at the ASBR responsible for advertising the inter-AS TE links. 6. IANA Considerations IANA is requested to make the following allocations from registries under its control. 6.1. Inter-AS Reachability TLV This document defines the following new ISIS TLV type that needs to be reflected in the ISIS TLV code-point registry: Mach & Renhai Expires December 28, 2007 [Page 10] Internet-Draft ISIS extensions for Inter-AS TE June 2007 Type Description IIH LSP SNP ---- ---------------------- --- --- --- 141 Inter-AS reachability n y n information 6.2. Sub-TLVs for the Inter-AS Reachability TLV This document defines the following new sub-TLV types of top- level TLV 141 that need to be reflected in the ISIS sub-TLV registry for TLV 141: Type Description Length ---- ------------------------------ -------- 23 Remote AS number 4 24 Remote ASBR Identifier 4 or 16 6.3. Sub-TLVs for the Extended IS Reachability TLV This document also defines the following new sub-TLV types of top- level TLV 22 that need to be reflected in the ISIS sub-TLV registry for TLV 22: Type Description Length ---- ------------------------------ -------- 22 Link Type 1 23 Remote AS number 4 24 Remote ASBR Identifier 4 or 16 6.4. ISIS TE Link Type IANA is requested to create a new sub-registry "TE Link Types" of the registry "Intermediate System to Intermediate System (ISIS) Traffic Engineering TLVs" to track TE Link Types. The sub-registry should read as follows: This document defines the Link Type sub-TLV of the extended IS reachability TLV. The following values are defined. Value Meaning Reference ---- -------------------- ---------- 3 Inter-AS link [this document] Mach & Renhai Expires December 28, 2007 [Page 11] Internet-Draft ISIS extensions for Inter-AS TE June 2007 New allocations from this registry are by IETF Standards Action. 7. Acknowledgments 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [ISIS] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, December 1990. [ISIS-TE] Smit, H. and T. Li, "Intermediate System to Intermediate System (IS-IS) Extensions for Traffic Engineering (TE)", RFC 3784, June 2004. [GMPLS-TE] K.Kompella and Y.Rekhter, "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching", RFC 4205, October 2005. 8.2. Informative References [INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic Engineering Requirements", RFC4216, November 2005. [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain path computation method for establishing Inter-domain", draft-ietf-ccamp-inter-domain-pd-path-comp, (work in progress). [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A Backward Recursive PCE-based Computation (BRPC) procedure to compute shortest inter-domain Traffic Engineering Label Switched Paths ", draft-ietf-pce-brpc, (work in progress) [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation Element (PCE)-Based Architecture", RFC4655, August 2006. Mach & Renhai Expires December 28, 2007 [Page 12] Internet-Draft ISIS extensions for Inter-AS TE June 2007 [ISIS-TE-V3] Harrison, J., Berger, J., and Bartlett, M., "IPv6 Traffic Engineering in IS-IS", draft-ietf-isis-ipv6-te- 03.txt, {work in progress}. Author's Addresses Mach Chen Huawei Technologies Co.,Ltd KuiKe Building, No.9 Xinxi Rd., Hai-Dian District Beijing, 100085 P.R. China Email: mach@huawei.com Renhai Zhang Huawei Technologies Co.,Ltd KuiKe Building, No.9 Xinxi Rd., Hai-Dian District Beijing, 100085 P.R. China Email: zhangrenhai@huawei.com Intellectual Property Statement 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. Mach & Renhai Expires December 28, 2007 [Page 13] Internet-Draft ISIS extensions for Inter-AS TE June 2007 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. Disclaimer of Validity 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. 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. Acknowledgment Mach & Renhai Expires December 28, 2007 [Page 14]