Network Working Group Y. Lee Internet Draft Huawei Intended status: Informational G. Bernstein Expires: April 2010 Grotto Networking D. Li Huawei W. Imajuku NTT October 9, 2009 Routing and Wavelength Assignment Information Model for Wavelength Switched Optical Networks draft-ietf-ccamp-rwa-info-05.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 April 9, 2009. Copyright Notice Copyright (c) 2009 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 in effect on the date of Bernstein and Lee Expires April 9, 2010 [Page 1] Internet-Draft Wavelength Switched Optical Networks October 2009 publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This document provides a model of information needed by the routing and wavelength assignment (RWA) process in wavelength switched optical networks (WSONs). The purpose of the information described in this model is to facilitate constrained lightpath computation in WSONs, particularly in cases where there are no or a limited number of wavelength converters available. This model does not include optical impairments. Table of Contents 1. Introduction...................................................3 1.1. Revision History..........................................3 1.1.1. Changes from 01......................................3 1.1.2. Changes from 02......................................3 1.1.3. Changes from 03......................................4 1.1.4. Changes from 04......................................4 2. Terminology....................................................4 3. Routing and Wavelength Assignment Information Model............5 3.1. Dynamic and Relatively Static Information.................5 3.2. Node Information..........................................6 3.2.1. Connectivity Matrix..................................6 3.2.2. Shared Risk Node Group...............................7 3.2.3. Wavelength Converter Pool............................7 3.2.4. OEO Wavelength Converter Info.......................10 3.3. Link Information.........................................10 3.3.1. Administrative Group................................10 3.3.2. Interface Switching Capability Descriptor...........11 3.3.3. Link Protection Type (for this link)................11 3.3.4. Shared Risk Link Group Information..................11 3.3.5. Traffic Engineering Metric..........................11 3.3.6. Port Wavelength (label) Restrictions................11 3.4. Dynamic Link Information.................................13 3.5. Dynamic Node Information.................................13 4. Security Considerations.......................................14 5. IANA Considerations...........................................14 6. Acknowledgments...............................................14 7. References....................................................15 7.1. Normative References.....................................15 7.2. Informative References...................................15 Bernstein and Lee Expires April 9, 2010 [Page 2] Internet-Draft Wavelength Switched Optical Networks October 2009 8. Contributors..................................................16 Author's Addresses...............................................17 Intellectual Property Statement..................................17 Disclaimer of Validity...........................................18 1. Introduction The purpose of the following information model for WSONs is to facilitate constrained lightpath computation and as such is not a general purpose network management information model. In particular this model has particular value in the cases where there are no or a limited number of wavelength converters available in the WSON. This constraint is frequently referred to as the "wavelength continuity" constraint, and the corresponding constrained lightpath computation is known as the routing and wavelength assignment (RWA) problem. Hence the information model must provide sufficient topology and wavelength restriction and availability information to support this computation. More details on the RWA process and WSON subsystems and their properties can be found in [WSON-Frame]. The model defined here does not currently include impairments however optical impairments can be accommodated by the general framework presented here. 1.1. Revision History 1.1.1. Changes from 01 Added text on multiple fixed and switched connectivity matrices. Added text on the relationship between SRNG and SRLG and encoding considerations. Added clarifying text on the meaning and use of port/wavelength restrictions. Added clarifying text on wavelength availability information and how to derive wavelengths currently in use. 1.1.2. Changes from 02 Integrated switched and fixed connectivity matrices into a single "connectivity matrix" model. Added numbering of matrices to allow for wavelength (time slot, label) dependence of the connectivity. Discussed general use of this node parameter beyond WSON. Integrated switched and fixed port wavelength restrictions into a single port wavelength restriction of which there can be more than one and added a reference to the corresponding connectivity matrix if there is one. Also took into account port wavelength restrictions in Bernstein and Lee Expires April 9, 2010 [Page 3] Internet-Draft Wavelength Switched Optical Networks October 2009 the case of symmetric switches, developed a uniform model and specified how general label restrictions could be taken into account with this model. Removed the Shared Risk Node Group parameter from the node info, but left explanation of how the same functionality can be achieved with existing GMPLS SRLG constructs. Removed Maximum bandwidth per channel parameter from link information. 1.1.3. Changes from 03 Removed signal related text from section 3.2.4 as signal related information is deferred to a new signal compatibility draft. Removed encoding specific text from Section 3.3.1 of version 03. 1.1.4. Changes from 04 Removed encoding specific text from Section 3.2.1. Removed encoding specific text from Section 3.4. 2. Terminology CWDM: Coarse Wavelength Division Multiplexing. DWDM: Dense Wavelength Division Multiplexing. FOADM: Fixed Optical Add/Drop Multiplexer. ROADM: Reconfigurable Optical Add/Drop Multiplexer. A reduced port count wavelength selective switching element featuring ingress and egress line side ports as well as add/drop side ports. RWA: Routing and Wavelength Assignment. Wavelength Conversion. The process of converting an information bearing optical signal centered at a given wavelength to one with "equivalent" content centered at a different wavelength. Wavelength conversion can be implemented via an optical-electronic-optical (OEO) process or via a strictly optical process. WDM: Wavelength Division Multiplexing. Bernstein and Lee Expires April 9, 2010 [Page 4] Internet-Draft Wavelength Switched Optical Networks October 2009 Wavelength Switched Optical Network (WSON): A WDM based optical network in which switching is performed selectively based on the center wavelength of an optical signal. 3. Routing and Wavelength Assignment Information Model We group the following WSON RWA information model into four categories regardless of whether they stem from a switching subsystem or from a line subsystem: o Node Information o Link Information o Dynamic Node Information o Dynamic Link Information Note that this is roughly the categorization used in [G.7715] section 7. In the following we use where applicable the reduced Backus-Naur form (RBNF) syntax of [RBNF] to aid in defining the RWA information model. 3.1. Dynamic and Relatively Static Information All the RWA information of concern in a WSON network is subject to change over time. Equipment can be upgraded; links may be placed in or out of service and the like. However, from the point of view of RWA computations there is a difference between information that can change with each successive connection establishment in the network and that information that is relatively static on the time scales of connection establishment. A key example of the former is link wavelength usage since this can change with connection setup/teardown and this information is a key input to the RWA process. Examples of relatively static information are the potential port connectivity of a WDM ROADM, and the channel spacing on a WDM link. In this document we will separate, where possible, dynamic and static information so that these can be kept separate in possible encodings and hence allowing for separate updates of these two types of information thereby reducing processing and traffic load caused by the timely distribution of the more dynamic RWA WSON information. Bernstein and Lee Expires April 9, 2010 [Page 5] Internet-Draft Wavelength Switched Optical Networks October 2009 3.2. Node Information The node information described here contains the relatively static information related to a WSON node. This includes connectivity constraints amongst ports and wavelengths since WSON switches can exhibit asymmetric switching properties. Additional information could include properties of wavelength converters in the node if any are present. In [Switch] it was shown that the wavelength connectivity constraints for a large class of practical WSON devices can be modeled via switched and fixed connectivity matrices along with corresponding switched and fixed port constraints. We include these connectivity matrices with our node information the switched and fixed port wavelength constraints with the link information. Formally, ::= [...] [] Where the Node_ID would be an appropriate identifier for the node within the WSON RWA context. Note that multiple connectivity matrices are allowed and hence can fully support the most general cases enumerated in [Switch]. 3.2.1. Connectivity Matrix The connectivity matrix (ConnectivityMatrix) represents either the potential connectivity matrix for asymmetric switches (e.g. ROADMs and such) or fixed connectivity for an asymmetric device such as a multiplexer. Note that this matrix does not represent any particular internal blocking behavior but indicates which ingress ports and wavelengths could possibly be connected to a particular output port. Representing internal state dependent blocking for a switch or ROADM is beyond the scope of this document and due to it's highly implementation dependent nature would not be subject to standardization. This is a conceptual M by N matrix representing the potential switched or fixed connectivity, where M represents the number of ingress ports and N the number of egress ports. We say this is a "conceptual" since this matrix tends to exhibit structure that allows for very compact representations that are useful for both transmission and path computation [Encode]. Note that the connectivity matrix concept can be useful in any context where asymmetric switches are utilized. ConnectivityMatrix(i, j) ::= Bernstein and Lee Expires April 9, 2010 [Page 6] Internet-Draft Wavelength Switched Optical Networks October 2009 Where is a unique identifier for the matrix. can be either 0 or 1 depending upon whether the connectivity is either fixed or potentially switched. represents the fixed or switched connectivity in that Matrix(i, j) = 0 or 1 depending on whether ingress port i can connect to egress port j for one or more wavelengths. 3.2.2. Shared Risk Node Group SRNG: Shared risk group for nodes. The concept of a shared risk link group was defined in [RFC4202]. This can be used to achieve a desired "amount" of link diversity. It is also desirable to have a similar capability to achieve various degrees of node diversity. This is explained in [G.7715]. Typical risk groupings for nodes can include those nodes in the same building, within the same city, or geographic region. Since the failure of a node implies the failure of all links associated with that node a sufficiently general shared risk link group (SRLG) encoding, such as that used in GMPLS routing extensions can explicitly incorporate SRNG information. 3.2.3. Wavelength Converter Pool A WSON node may include wavelength converters. These are usually arranged into some type of pool to promote resource sharing. There are a number of different approaches used in the design of switches with converter pools. However, from the point of view of path computation we need to know the following: 1. The nodes that support wavelength conversion. 2. The accessibility and availability of a wavelength converter to convert from a given ingress wavelength on a particular ingress port to a desired egress wavelength on a particular egress port. 3. Limitations on the types of signals that can be converted and the conversions that can be performed. To model point 2 above we can use a similar technique as used to model ROADMs and optical switches this technique was generally discussed in [WSON-Frame] and consisted of a matrix to indicate possible connectivity along with wavelength constraints for links/ports. Since wavelength converters are considered a scarce Bernstein and Lee Expires April 9, 2010 [Page 7] Internet-Draft Wavelength Switched Optical Networks October 2009 resource we will also want to our model to include as a minimum the usage state of individual wavelength converters in the pool. Models that incorporate more state to further reveal blocking conditions on ingress or egress to particular converters are for further study. We utilize a three stage model as shown schematically in Figure 1. In this model we assume N ingress ports (fibers), P wavelength converters, and M egress ports (fibers). Since not all ingress ports can necessarily reach the converter pool, the model starts with a wavelength pool ingress matrix WI(i,p) = {0,1} whether ingress port i can reach potentially reach wavelength converter p. Since not all wavelengths can necessarily reach all the converters or the converters may have limited input wavelength range we have a set of ingress port constraints for each wavelength converter. Currently we assume that a wavelength converter can only take a single wavelength on input. We can model each wavelength converter ingress port constraint via a wavelength set mechanism. Next we have a state vector WC(j) = {0,1} dependent upon whether wavelength converter j in the pool is in use. This is the only state kept in the converter pool model. This state is not necessary for modeling "fixed" transponder system, i.e., systems where there is no sharing. In addition, this state information may be encoded in a much more compact form depending on the overall connectivity structure [WC-Pool]. After that, we have a set of wavelength converter egress wavelength constraints. These constraints indicate what wavelengths a particular wavelength converter can generate or are restricted to generating due to internal switch structure. Finally, we have a wavelength pool egress matrix WE(p,k) = {0,1} depending on whether the output from wavelength converter p can reach egress port k. Examples of this method being used to model wavelength converter pools for several switch architectures from the literature are given in reference [WC-Pool]. Bernstein and Lee Expires April 9, 2010 [Page 8] Internet-Draft Wavelength Switched Optical Networks October 2009 I1 +-------------+ +-------------+ E1 ----->| | +--------+ | |-----> I2 | +------+ WC #1 +-------+ | E2 ----->| | +--------+ | |-----> | Wavelength | | Wavelength | | Converter | +--------+ | Converter | | Pool +------+ WC #2 +-------+ Pool | | | +--------+ | | | Ingress | | Egress | | Connection | . | Connection | | Matrix | . | Matrix | | | . | | | | | | IN | | +--------+ | | EM ----->| +------+ WC #P +-------+ |-----> | | +--------+ | | +-------------+ ^ ^ +-------------+ | | | | | | | | Ingress wavelength Egress wavelength constraints for constraints for each converter each converter Figure 1 Schematic diagram of wavelength converter pool model. Formally we can specify the model as: ::= [] Bernstein and Lee Expires April 9, 2010 [Page 9] Internet-Draft Wavelength Switched Optical Networks October 2009 Note that except for all the other components of are relatively static. In addition is a relatively small structure compared potentially to the others and hence in a future revision of this document maybe moved to a new section on dynamic node information. 3.2.4. OEO Wavelength Converter Info An OEO based wavelength converter can be characterized by an input wavelength set and an output wavelength set. Such a wavelength converter can be modeled by: ::= [] [] 3.3. Link Information MPLS-TE routing protocol extensions for OSPF and IS-IS [RFC3630], [RFC5305] along with GMPLS routing protocol extensions for OSPF and IS-IS [RFC4203, RFC5307] provide the bulk of the relatively static link information needed by the RWA process. WSON networks bring in additional link related constraints. These stem from WDM line system characterization, laser transmitter tuning restrictions, and switching subsystem port wavelength constraints, e.g., colored ROADM drop ports. In the following summarize both information from existing route protocols and new information that maybe needed by the RWA process. ::= [] [] [] []... [] [] 3.3.1. Administrative Group AdministrativeGroup: Defined in [RFC3630]. Each set bit corresponds to one administrative group assigned to the interface. A link may belong to multiple groups. This is a configured quantity and can be used to influence routing decisions. Bernstein and Lee Expires April 9, 2010 [Page 10] Internet-Draft Wavelength Switched Optical Networks October 2009 3.3.2. Interface Switching Capability Descriptor InterfaceSwCapDesc: Defined in [RFC4202], lets us know the different switching capabilities on this GMPLS interface. In both [RFC4203] and [RFC5307] this information gets combined with the maximum LSP bandwidth that can be used on this link at eight different priority levels. 3.3.3. Link Protection Type (for this link) Protection: Defined in [RFC4202] and implemented in [RFC4203, RFC5307]. Used to indicate what protection, if any, is guarding this link. 3.3.4. Shared Risk Link Group Information SRLG: Defined in [RFC4202] and implemented in [RFC4203, RFC5307]. This allows for the grouping of links into shared risk groups, i.e., those links that are likely, for some reason, to fail at the same time. 3.3.5. Traffic Engineering Metric TrafficEngineeringMetric: Defined in [RFC3630]. This allows for the definition of one additional link metric value for traffic engineering separate from the IP link state routing protocols link metric. Note that multiple "link metric values" could find use in optical networks, however it would be more useful to the RWA process to assign these specific meanings such as link mile metric, or probability of failure metric, etc... 3.3.6. Port Wavelength (label) Restrictions Port wavelength (label) restrictions (PortWavelengthRestriction) model the wavelength (label) restrictions that the link and various optical devices such as OXCs, ROADMs, and waveband multiplexers may impose on a port. These restrictions tell us what wavelength may or may not be used on a link and are relatively static. This plays an important role in fully characterizing a WSON switching device [Switch]. Port wavelength restrictions are specified relative to the port in general or to a specific connectivity matrix (section 3.2.1. Reference [Switch] gives an example where both switch and fixed connectivity matrices are used and both types of constraints occur on the same port. Such restrictions could be applied generally to other label types in GMPLS by adding new kinds of restrictions. ::= [...] [...] Bernstein and Lee Expires April 9, 2010 [Page 11] Internet-Draft Wavelength Switched Optical Networks October 2009 ::= [] ::= [] ::= [...] [] [] Where MatrixID is the ID of the corresponding connectivity matrix (section 3.2.1. The RestrictionType parameter is used to specify general port restrictions and matrix specific restrictions. It can take the following values and meanings: SIMPLE_WAVELENGTH: Simple wavelength set restriction; The wavelength set parameter is required. CHANNEL_COUNT: The number of channels is restricted to be less than or equal to the Max number of channels parameter (which is required). WAVEBAND1: Waveband device with a tunable center frequency and passband. This constraint is characterized by the MaxWaveBandWidth parameters which indicates the maximum width of the waveband in terms of channels. Note that an additional wavelength set can be used to indicate the overall tuning range. Specific center frequency tuning information can be obtained from dynamic channel in use information. It is assumed that both center frequency and bandwidth (Q) tuning can be done without causing faults in existing signals. Restriction specific parameters are used with one or more of the previously listed restriction types. The currently defined parameters are: WavelengthSet is a conceptual set of wavelengths (labels). MaxNumChannels is the maximum number of channels that can be simultaneously used (relative to either a port or a matrix). MaxWaveBandWidth is the maximum width of a tunable waveband switching device. Bernstein and Lee Expires April 9, 2010 [Page 12] Internet-Draft Wavelength Switched Optical Networks October 2009 For example, if the port is a "colored" drop port of a ROADM then we have two restrictions: (a) CHANNEL_COUNT, with MaxNumChannels = 1, and (b) SIMPLE_WAVELENGTH, with the wavelength set consisting of a single member corresponding to the frequency of the permitted wavelength. See [Switch] for a complete waveband example. This information model for port wavelength (label) restrictions is fairly general in that it can be applied to ports that have label restrictions only or to ports that are part of an asymmetric switch and have label restrictions. In addition, the types of label restrictions that can be supported are extensible. 3.4. Dynamic Link Information By dynamic information we mean information that is subject to change on a link with subsequent connection establishment or teardown. Currently for WSON the only information we currently envision is wavelength availability and wavelength in use for shared backup purposes. ::= [] AvailableWavelengths is a set of wavelengths (labels) currently available on the link. Given this information and the port wavelength restrictions we can also determine which wavelengths are currently in use. This parameter could potential be used with other technologies that GMPLS currently covers or may cover in the future. SharedBackupWavelengths is a set of wavelengths (labels)currently used for shared backup protection on the link. An example usage of this information in a WSON setting is given in [Shared]. This parameter could potential be used with other technologies that GMPLS currently covers or may cover in the future. 3.5. Dynamic Node Information Dynamic node information is used to hold information for a node that can change frequently. Currently only wavelength converter pool information is included as a possible (but not required) information sub-element. ::= [] Where NodeID is a node identifier and the exact form of the wavelength converter pool status information is TBD. Bernstein and Lee Expires April 9, 2010 [Page 13] Internet-Draft Wavelength Switched Optical Networks October 2009 4. Security Considerations This document discussed an information model for RWA computation in WSONs. Such a model is very similar from a security standpoint of the information that can be currently conveyed via GMPLS routing protocols. Such information includes network topology, link state and current utilization, and well as the capabilities of switches and routers within the network. As such this information should be protected from disclosure to unintended recipients. In addition, the intentional modification of this information can significantly affect network operations, particularly due to the large capacity of the optical infrastructure to be controlled. 5. IANA Considerations This informational document does not make any requests for IANA action. 6. Acknowledgments This document was prepared using 2-Word-v2.0.template.dot. Bernstein and Lee Expires April 9, 2010 [Page 14] Internet-Draft Wavelength Switched Optical Networks October 2009 7. References 7.1. Normative References [Encode] G. Bernstein, Y. Lee, D. Li, W. Imajuku, "Routing and Wavelength Assignment Information Encoding for Wavelength Switched Optical Networks", work in progress: draft-ietf- ccamp-rwa-wson-encode. [RBNF] A. Farrel, "Reduced Backus-Naur Form (RBNF) A Syntax Used in Various Protocol Specifications", RFC 5511, April 2009. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4202, October 2005 [RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005. [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, October 2008. [RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 5307, October 2008. [WSON-Frame] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS and PCE Control of Wavelength Switched Optical Networks", work in progress: draft-ietf-ccamp-rwa-wson-framework. 7.2. Informative References [Shared] G. Bernstein, Y. Lee, "Shared Backup Mesh Protection in PCE- based WSON Networks", iPOP 2008, http://www.grotto- networking.com/wson/iPOP2008_WSON-shared-mesh-poster.pdf . [Switch] G. Bernstein, Y. Lee, A. Gavler, J. Martensson, " Modeling WDM Wavelength Switching Systems for Use in GMPLS and Automated Path Computation", Journal of Optical Communications and Networking, vol. 1, June, 2009, pp. 187-195. Bernstein and Lee Expires April 9, 2010 [Page 15] Internet-Draft Wavelength Switched Optical Networks October 2009 [G.Sup39] ITU-T Series G Supplement 39, Optical system design and engineering considerations, February 2006. [WC-Pool] G. Bernstein, Y. Lee, "Modeling WDM Switching Systems including Wavelength Converters" to appear www.grotto- networking.com, 2008. 8. Contributors Diego Caviglia Ericsson Via A. Negrone 1/A 16153 Genoa Italy Phone: +39 010 600 3736 Email: diego.caviglia@(marconi.com, ericsson.com) Anders Gavler Acreo AB Electrum 236 SE - 164 40 Kista Sweden Email: Anders.Gavler@acreo.se Jonas Martensson Acreo AB Electrum 236 SE - 164 40 Kista, Sweden Email: Jonas.Martensson@acreo.se Itaru Nishioka NEC Corp. 1753 Simonumabe, Nakahara-ku, Kawasaki, Kanagawa 211-8666 Japan Phone: +81 44 396 3287 Email: i-nishioka@cb.jp.nec.com Lyndon Ong Ciena Email: lyong@ciena.com Bernstein and Lee Expires April 9, 2010 [Page 16] Internet-Draft Wavelength Switched Optical Networks October 2009 Author's Addresses Greg M. Bernstein (ed.) Grotto Networking Fremont California, USA Phone: (510) 573-2237 Email: gregb@grotto-networking.com Young Lee (ed.) Huawei Technologies 1700 Alma Drive, Suite 100 Plano, TX 75075 USA Phone: (972) 509-5599 (x2240) Email: ylee@huawei.com Dan Li Huawei Technologies Co., Ltd. F3-5-B R&D Center, Huawei Base, Bantian, Longgang District Shenzhen 518129 P.R.China Phone: +86-755-28973237 Email: danli@huawei.com Wataru Imajuku NTT Network Innovation Labs 1-1 Hikari-no-oka, Yokosuka, Kanagawa Japan Phone: +81-(46) 859-4315 Email: imajuku.wataru@lab.ntt.co.jp Intellectual Property Statement 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 Bernstein and Lee Expires April 9, 2010 [Page 17] Internet-Draft Wavelength Switched Optical Networks October 2009 represent that it has made any independent effort to identify any such rights. 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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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Bernstein and Lee Expires April 9, 2010 [Page 18]