Network Working Group Fatai Zhang Internet-Draft Huawei Intended status: Standards Track Oscar Gonzalez de Dios Telefonica D. Ceccarelli Ericsson Expires: September 12, 2012 March 12, 2012 RSVP-TE Signaling Extensions in support of Flexible Grid draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 September 12, 2012. Abstract This memo describes the signaling extensions of GMPLS control of flexible grid network. Zhang Expires September 2012 [Page 1] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 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. Terminology .................................................. 3 3. Requirements for Flexible Grid Signaling ..................... 3 3.1. Slot Width .............................................. 4 3.2. Frequency Slot .......................................... 4 4. Extensions ................................................... 5 4.1. SSON Traffic Parameters ................................. 5 4.2. Generalized Label ....................................... 6 4.3. Signaling Procedures .................................... 8 4.3.1. Distributed SA ..................................... 8 4.3.2. Centralized SA ..................................... 9 5. Example ...................................................... 9 6. IANA Considerations ......................................... 10 6.1. RSVP Objects Class Types ............................... 10 6.2. DWDM Channel Spacing ................................... 10 6.3. PCEP Object ............................................ 11 7. Security Considerations ..................................... 11 8. References .................................................. 11 8.1. Normative References ................................... 11 8.2. Informative References ................................. 12 9. Contributors' Address ....................................... 12 10. Authors' Addresses ......................................... 13 1. Introduction [G.694.1v1] defines the DWDM frequency grids for WDM applications. A frequency grid is a reference set of frequencies used to denote allowed nominal central frequencies that may be used for defining applications. The channel spacing, i.e. the frequency spacing between two allowed nominal central frequencies can be 12.5 GHz, 25 GHz, 50 GHz, 100 GHz and integer multiples of 100 GHz as defined in [G.694.1v1]. All of the wavelengths on a fiber SHALL use different central frequencies and occupy a fixed bandwidth of frequency. [G.FLEXIGRID], an updated version of [G.694.1v1] has be consented in December 2011 in support of flexible grids. The terms "frequency Zhang Expires September 2012 [Page 2] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 slot (i.e. the frequency range allocated to a specific channel and unavailable to other channels within a flexible grid)" and "slot width" (i.e. the full width of a frequency slot in a flexible grid) are introduced to define a flexible grid. A channel is represented as an LSC (Lambda Switching Capable) LSP in the control plane and occupies a frequency slot on each fiber it traverses. In the case of flexible grid, the different flexi-LSPs may have different slot widths on a given fiber, referring to [SSON-FWK]. [WSON-SIG] describes the requirements and extensions for WSON signaling. It focuses on the control of optical networks using a fixed DWDM grid. This document describes the additional requirements and extensions for signaling of LSPs using the felxi-grid capabilities. 2. Terminology Flexi-grid: See [SSON-FWK]. Slot Width: See [SSON-FWK]. Frequency Range: See [SSON-FWK]. SSON: Spectrum-Switched Optical Networks; See [SSON-FWK]. flexi-LSP: See [SSON-FWK]. RSA: See [SSON-FWK]. 3. Requirements for Flexible Grid Signaling A flexi-LSP SHOULD occupy a frequency slot, i.e. a range of frequencies. The process of computing a route and the allocation of a frequency slot is referred to as RSA (Routing and Spectrum Assignment). [SSON-FWK] describes three types of architecture approaches to RSA, which are: combined RSA, separated RSA and distributed SA. The first two approaches among them could be called "centralized SA", since both routing and spectrum (frequency slot) assignment are performed by centralized entity before the signaling procedure. In the case of centralized SA, the assigned frequency slot SHOULD be specified in the Path message. In the case of distributed SA, the slot width of the flexi-LSP SHOULD be specified in the Path message, allowing the involved network elements (e.g., the egress node) to perform such distributed assignment. Zhang Expires September 2012 [Page 3] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 Similar to a fixed grid network, if the capability of shifting or converting the whole optical spectrum allocated to a flexi-LSP is not available, the flexi-LSP is subject to the Optical "Spectrum Continuity Constraint", as described in [SSON-FWK]. 3.1. Slot Width The slot width is an end-to-end parameter representing how much frequency resource is requested for a flexi-LSP. Since different LSPs may request different amounts of frequency resource in flexible grid networks, the slot width SHOULD be carried in the signaling message, so that all the nodes along the LSP can know how much frequency resource (including both central frequency and slot width) will be allocated for the LSP. 3.2. Frequency Slot The frequency slot information represents which part of the frequency resource is allocated on each link for a flexi-LSP. This information SHOULD be carried hop-by-hop in signaling message so that each node can indicate its neighbor the resource reservation on the link between them. The frequency slot can be represented by the two parameters: central frequency and slot width, as follows: Frequency slot = [(central frequency) - (slot width)/2] ~ [(central frequency) + (slot width)/2] Since the slot width information is carried in the signaling message (as described in Section 2.1), also the central frequency parameter SHOULD be carried in the signaling message for frequency slot determination. As described in [G.FLEXIGRID], for the flexible DWDM grid, the allowed frequency slots have a nominal central frequency (in THz) defined by: 193.1 + n * 0.00625, where n is a positive or negative integer including 0, and 0.00625 is the nominal central frequency granularity in THz. and a slot width defined by: 12.5 * m, where m is a positive integer and 12.5 is the slot width granularity in GHz. Zhang Expires September 2012 [Page 4] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 Applications may be defined where only a subset of the possible slot widths and positions are required to be supported. For example, an application could be defined where the nominal central frequency granularity is 12.5 GHz (by only requiring values of n that are even) and that only requires slot widths as a multiple of 25 GHz (by only requiring values of m that are even). Figure 1 shows an example of two flexi-LSPs traversing a link and illustrates how to determine the frequency slot based on the central frequency and slot width information. Frequency Slot 1 Frequency Slot 2 ------------- ------------------- | | | | -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 ...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--... ------------- ------------------- ^ ^ Central F = 193.1THz Central F = 193.14375 THz Slot width = 25 GHz Slot width = 37.5 GHz Figure 1 - Two flexi-LSPs traverse a Link The two wavelengths shown in figure 1 have the following meaning: flexi-LSP 1: central frequency = 193.1 THz, slot width = 25 GHz. It means the frequency slot [193.0875 THz, 193.1125 THz] is assigned to this flexi-LSP. flexi-LSP 2: central frequency = 193.14375 THz, slot width = 37.5 GHz. It means the frequency slot [193.125 THz, 193.1625 THz] is assigned to this flexi-LSP. Note that the frequency slots of two flexi-LSPs on a fiber MUST NOT overlap with each other. 4. Extensions This section defines the extensions of signaling for flexible grid. 4.1. SSON Traffic Parameters As described in Section 2, the slot width represents how much frequency resource is requested for a flexi-LSP, i.e., it describes the end-to-end traffic profile of the LSP. Therefore, the slot width SHOULD be regarded as a traffic parameter for a flexi-LSP. Zhang Expires September 2012 [Page 5] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 The SSON traffic parameters are organized 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | m | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ m (8 bits): the slot width is specified by m*12.5 GHz. Note that the slot width of a fixed grid defined in [G.694.1v1] can also be specified by m because the defined channel spacings (12.5 GHz, 25 GHz, 50 GHz, 100 GHz and integer multiples of 100 GHz) are also the multiple of 12.5 GHz. Therefore, the traffic parameters are general for SSON including both fixed grid (i.e. WSON) and flexible grid. The SSON traffic parameters are carried in the SENDER_TSPEC object within a Path message and in the FLOWSPEC object within a Resv message: SSON SENDER_TSPEC: Class = 12, C-Type = to be assigned by IANA, preferred 8. SSON FLOWSPEC: Class = 9, C-Type = to be assigned by IANA, preferred 8. 4.2. Generalized Label In the case of a flexible grid link, the allocated central frequency is calculated as follows: Central Frequency = (193.1 + n * 0.00625) THz Where n can be a positive or negative integer, or 0. The Generalized Label object is used to indicate the resource reserved on a link. In Flexible Grid networks, it is used to indicate which frequency slot is allocated on a link for the given flexi-LSP. Since the frequency slot assigned to a flexi-LSP can be determined by the combination of [central frequency, slot width], while the slot width of a flexi-LSP is specified in the traffic parameters, the Label object just needs to carry the assigned central frequency. Zhang Expires September 2012 [Page 6] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 Therefore, the wavelength label format defined in [RFC6205] can be reused to specify the central frequency of a flexi-LSP, without any change on the label format. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Grid | C.S. | Identifier | n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The meaning of Grid, Identifier and n fields are not changed. The usage of the label format is also not changed. According to [G.FLEXIGRID], flexible grid still belongs to DWDM, so there is no need to introduce a new type of Grid, i.e., Grid=1 (ITU- T DWDM) SHOULD be used for flexible grid. In case of Grid=1 (ITU-T DWDM), according to [G.697v2.1], a new value of C.S. is defined for flexible 6.25 GHz grid. The C.S.(Channel Spacing) field is defined as follows: +--------------+---------+ |C.S. (GHz) | Value | +--------------+---------+ | Reserved | 0 | +--------------+---------+ | 100 | 1 | +--------------+---------+ | 50 | 2 | +--------------+---------+ | 25 | 3 | +--------------+---------+ | 12.5 | 4 | +--------------+---------+ |Flexible grid | 5 (TBA) | +--------------+---------+ |Future use | 6 ~ 15 | +--------------+---------+ The frequency is calculated as such in [G.FLEXIGRID]: Frequency (THz) = 193.1 THz + n * channel spacing (THz) Zhang Expires September 2012 [Page 7] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 For the case where the channel spacing value is set to "Flexible grid", a channel spacing of 6.25 GHz MUST be used in the above formula. 4.3. Signaling Procedures This section describes the signaling procedures for distributed SA and centralized SA (See [SSON-FWK]). 4.3.1. Distributed SA In this case, only the route is provided by a PCE or ingress node before the signaling procedure. The available central frequencies SHALL be collected hop by hop and the egress node SHOULD select a proper central frequency for the LSP. After the route is computed, the ingress node SHOULD find out the available central frequencies for the LSP on the next link of the route. If the frequency slot does not overlap with the existing flexi-LSPs, the central frequency is considered to be available for the requesting flexi-LSP. Then a Path message is sent to the next node on the route. The Path message MUST contain a SSON SENDER_TSPEC object to specify the slot width of the flexi-LSP. A LABEL_SET object SHALL be added to the Path message, which contains the candidate central frequencies for the LSP on the next link. When an intermediate node receives a Path message, it can get the slot width from the SSON SENDER_TSPEC object. Then it SHOULD find the available central frequencies for the LSP on the next link of the route similar to the ingress node. The common part of the two available central frequency sets, i.e. the set received from the Path message and the set of the next link, SHALL be selected as the new available central frequency set for the LSP. If the new set is null, the Path message SHALL be rejected by a PathErr message. Otherwise, the LABEL SET object in the Path message SHALL be updated according to the new set and the Path message is forwarded to the next node on the route. When an egress node receives a Path message, it SHOULD select an available central frequency from the LABEL SET object based on local policy and determine the frequency slot based on the slot width and the selected central frequency (See section 2.2). Then a Resv message is responded so that the nodes along the LSP can establish the optical cross-connect based on the frequency slot determined by Zhang Expires September 2012 [Page 8] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 the slot width in the traffic parameters and the central frequency in the label. 4.3.2. Centralized SA In this case, both of the route and the frequency slot are provided by the PCE or ingress node. When signaling the LSP, the slot width is carried in the traffic parameters, and the assigned central frequency is carried in the Label ERO. When the nodes along the LSP receive the Path message carrying this information, they can determine the frequency slot by the slot width and the central frequency, so that they can establish the optical cross-connect based on the central frequency. The procedures of ERO and Label ERO are the same as described in [RFC3209] and [RFC3473]. 5. Example An example is provided as below. In this example, assume that there are two links and three nodes for the network topology and a flex- LSP is assumed to be created from Node N1 to Node N3. +------+ link1 +------+ link2 +------+ | N1 +----------+ N2 +----------+ N3 | +------+ +------+ +------+ Frequency resources on link1 (central frequency granularity = 12.5 GHz): -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 ...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--... |--Available Frequency Range--| Frequency resources on link2 (central frequency granularity = 12.5 GHz): -8 -6 -4 -2 0 2 4 6 8 10 ...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--... |--Available Frequency Range--| The symbol '+' represents the allowed nominal central frequency. The symbol "--" represents a 6.25 GHz frequency unit. The number on the top of the line represents the 'n' in the frequency calculation formula (193.1 + n * 0.00625). The nominal central frequency is 193.1 THz when n equals zero. A flexi-LSP establishment request: Zhang Expires September 2012 [Page 9] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 o Source node: N1 o Sink node: N3 o Slot width: 25 GHz The usable central frequencies set for the flexi-LSP is [n=0,1,2,3,4,5,6] on link1. But on link2, because the central frequency granularity is 12.5 GHz, The usable central frequencies set for the flexi-LSP is [n=0,2,4]. In the case of Centralized SA, PCE or ingress node (N1) could allocate an available frequency slot to the flexi-LSP, e.g. n=2 and slot width=50 Ghz. During the LSP setup procedures, the slot width (50 GHz, i.e. m=4) should be specified in the traffic parameters objects and the central frequency (n=2) should be specified in the label objects. 6. IANA Considerations 6.1. RSVP Objects Class Types This document introduces two new Class Types for existing RSVP objects. IANA is requested to make allocations from the "Resource ReSerVation Protocol (RSVP) Parameters" registry using the "Class Names, Class Numbers, and Class Types" sub-registry. Class Number Class Name Reference ------------ ----------------------- --------- 9 FLOWSPEC [RFC2205] Class Type (C-Type): (TBA) SSON FLOWSPEC [This.I-D] Class Number Class Name Reference ------------ ----------------------- --------- 12 SENDER_TSPEC [RFC2205] Class Type (C-Type): (TBA) SSON SENDER_TSPEC [This.I-D] 6.2. DWDM Channel Spacing The IANA has created a registry and manages the space of DWDM Channel Spacing as described in section 5.2 of [RFC6205]. It is requested that the IANA makes assignments from the DWDM Channel Spacing. Zhang Expires September 2012 [Page 10] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 Value Channel Spacing (GHz) Reference ----- ------------------------- ---------- TBA Flexible grid [This.I-D] 6.3. PCEP Object This document introduces a new Object-Type for existing PCEP objects. It is requested that the IANA makes an assignment from the object- type of GENERALIZED-BANDWIDTH. Object-Class Name Reference ------------ ----------------------- --------- TBA GENERALIZED-BANDWIDTH [GMPLS-PCE] Object-Type: (TBA) SSON [This.I-D] 7. Security Considerations This document introduces no new security considerations to [RFC3473]. 8. References 8.1. Normative References [RFC2119] S. Bradner, "Key words for use in RFCs to indicate requirements levels", RFC 2119, March 1997. [WSON-PCE] Y. Lee, G. Bernstein, Jonas Martensson, T. Takeda and T. Tsuritani, "PCEP Requirements for WSON Routing and Wavelength Assignment", draft-ietf-pce-wson-routing- wavelength-05, July 2011. [WSON-SIG] G. Bernstein, Sugang Xu, Y. Lee, G. Martinelli and Hiroaki Harai, "Signaling Extensions for Wavelength Switched Optical Networks", draft-ietf-ccamp-wson- signaling-02, September 2011. [RFC3209] D. Awduche et al, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC3209, December 2001. Zhang Expires September 2012 [Page 11] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 [RFC3473] L. Berger, Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol- Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. [RFC6163] Y. Lee, G. Bernstein and W. Imajuku, "Framework for GMPLS and Path Computation Element (PCE) Control of Wavelength Switched Optical Networks (WSONs)", RFC 6163, April 2011. [RFC6205] T. Otani and D. Li, "Generalized Labels for Lambda-Switch- Capable (LSC) Label Switching Routers", RFC 6205, March 2011. [SSON-FWK] F.Zhang et al, "Framework for GMPLS and PCE Control of Spectrum Switched Optical Networks" , draft-zhang-ccamp- sson-framework, in progress. [G.FLEXIGRID] Revised G.694.1 version 1.6, Consented in December 2011, ITU-T Study Group 15. [GMPLS-PCE] C. Margaria, O. Gonzalez de Dios, Desarrollo, and F. Zhang, "PCEP extensions for GMPLS", draft-ietf-pce-gmpls- pcep-extensions-04, October 2011. 8.2. Informative References [G.694.1v1] ITU-T Recommendation G.694.1, Spectral grids for WDM applications: DWDM frequency grid, June 2002. [G.697v2.1] Draft revised G.697 version 2.1, Consented in December 2011, ITU-T Study Group 15. 9. Contributors' Address Ramon Casellas CTTC - Centre Tecnologic de Telecomunicacions de Catalunya Av. Carl Friedrich Gauss n7 Castelldefels, Barcelona 08860 Spain Phone: Email: ramon.casellas@cttc.es Zhang Expires September 2012 [Page 12] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 10. Authors' Addresses Fatai Zhang Huawei Technologies F3-5-B R&D Center, Huawei Base Bantian, Longgang District Shenzhen 518129 P.R.China Phone: +86-755-28972912 Email: zhangfatai@huawei.com Oscar Gonzalez de Dios Telefonica Investigacion y Desarrollo Emilio Vargas 6 Madrid, 28045 Spain Phone: +34 913374013 Email: ogondio@tid.es Felipe Jimenez Arribas Telefonica Investigacion y Desarrollo Emilio Vargas 6 Madrid, 28045 Spain Email: felipej@tid.es Daniele Ceccarelli Ericsson Via A. Negrone 1/A Genova - Sestri Ponente Italy Email: daniele.ceccarelli@ericsson.com Xiaobing Zi Huawei Technologies F3-5-B R&D Center, Huawei Base Bantian, Longgang District Shenzhen 518129 P.R.China Phone: +86-755-28973229 Email: zixiaobing@huawei.com Zhang Expires September 2012 [Page 13] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 Yi Lin Huawei Technologies Co., Ltd. F3-5-B R&D Center, Huawei Base, Bantian, Longgang District Shenzhen 518129 P.R.China Phone: +86-755-28972914 Email: yi.lin@huawei.com Intellectual Property The IETF Trust 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 any IETF 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. Copies of Intellectual Property 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 any standard or specification contained in an IETF Document. Please address the information to the IETF at ietf-ipr@ietf.org. The definitive version of an IETF Document is that published by, or under the auspices of, the IETF. Versions of IETF Documents that are published by third parties, including those that are translated into other languages, should not be considered to be definitive versions of IETF Documents. The definitive version of these Legal Provisions is that published by, or under the auspices of, the IETF. Versions of these Legal Provisions that are published by third parties, including those that are translated into other languages, should not be considered to be definitive versions of these Legal Provisions. Zhang Expires September 2012 [Page 14] draft-zhang-ccamp-flexible-grid-rsvp-te-ext-01.txt March 2012 For the avoidance of doubt, each Contributor to the IETF Standards Process licenses each Contribution that he or she makes as part of the IETF Standards Process to the IETF Trust pursuant to the provisions of RFC 5378. No language to the contrary, or terms, conditions or rights that differ from or are inconsistent with the rights and licenses granted under RFC 5378, shall have any effect and shall be null and void, whether published or posted by such Contributor, or included with or in such Contribution. Disclaimer of Validity All IETF Documents and the information contained therein 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 THEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Full Copyright Statement Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Zhang Expires September 2012 [Page 15]