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+Internet Engineering Task Force (IETF) F. Zhang
+Request for Comments: 7580 Y. Lee
+Category: Standards Track J. Han
+ISSN: 2070-1721 Huawei
+ G. Bernstein
+ Grotto Networking
+ Y. Xu
+ CATR
+ June 2015
+
+
+ OSPF-TE Extensions for General Network Element Constraints
+
+Abstract
+
+ Generalized Multiprotocol Label Switching (GMPLS) can be used to
+ control a wide variety of technologies including packet switching
+ (e.g., MPLS), time division (e.g., Synchronous Optical Network /
+ Synchronous Digital Hierarchy (SONET/SDH) and Optical Transport
+ Network (OTN)), wavelength (lambdas), and spatial switching (e.g.,
+ incoming port or fiber to outgoing port or fiber). In some of these
+ technologies, network elements and links may impose additional
+ routing constraints such as asymmetric switch connectivity, non-
+ local label assignment, and label range limitations on links. This
+ document describes Open Shortest Path First (OSPF) routing protocol
+ extensions to support these kinds of constraints under the control of
+ GMPLS.
+
+Status of This Memo
+
+ This is an Internet Standards Track document.
+
+ This document is a product of the Internet Engineering Task Force
+ (IETF). It represents the consensus of the IETF community. It has
+ received public review and has been approved for publication by the
+ Internet Engineering Steering Group (IESG). Further information on
+ Internet Standards is available in Section 2 of RFC 5741.
+
+ Information about the current status of this document, any errata,
+ and how to provide feedback on it may be obtained at
+ http://www.rfc-editor.org/info/rfc7580.
+
+
+
+
+
+
+
+
+
+
+Zhang, et al. Standards Track [Page 1]
+
+RFC 7580 Generic Constraint OSPF-TE June 2015
+
+
+Copyright Notice
+
+ Copyright (c) 2015 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.
+
+Table of Contents
+
+ 1. Introduction ....................................................3
+ 1.1. Conventions Used in This Document ..........................3
+ 2. Node Information ................................................3
+ 2.1. Connectivity Matrix ........................................4
+ 3. Link Information ................................................4
+ 3.1. Port Label Restrictions ....................................5
+ 4. Routing Procedures ..............................................5
+ 5. Scalability and Timeliness ......................................6
+ 5.1. Different Sub-TLVs into Multiple LSAs ......................6
+ 5.2. Decomposing a Connectivity Matrix into Multiple Matrices ...6
+ 6. Security Considerations .........................................7
+ 7. Manageability ...................................................7
+ 8. IANA Considerations .............................................8
+ 8.1. Node Information ...........................................8
+ 8.2. Link Information ...........................................8
+ 9. References ......................................................9
+ 9.1. Normative References .......................................9
+ 9.2. Informative References ....................................10
+ Acknowledgments ...................................................11
+ Contributors ......................................................11
+ Authors' Addresses ................................................12
+
+
+
+
+
+
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+Zhang, et al. Standards Track [Page 2]
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+RFC 7580 Generic Constraint OSPF-TE June 2015
+
+
+1. Introduction
+
+ Some data-plane technologies that require the use of a GMPLS control
+ plane impose additional constraints on switching capability and label
+ assignment. In addition, some of these technologies should be
+ capable of performing non-local label assignment based on the nature
+ of the technology, e.g., wavelength continuity constraint in
+ Wavelength Switched Optical Networks (WSONs) [RFC6163]. Such
+ constraints can lead to the requirement for link-by-link label
+ availability in path computation and label assignment.
+
+ [RFC7579] provides efficient encodings of information needed by the
+ routing and label assignment process in technologies such as WSON.
+ These encodings are potentially applicable to a wider range of
+ technologies as well. The encoding provided in [RFC7579] is
+ protocol-neutral and can be used in routing, signaling, and/or Path
+ Computation Element communication protocol extensions.
+
+ This document defines extensions to the OSPF routing protocol based
+ on [RFC7579] to enhance the Traffic Engineering (TE) properties of
+ GMPLS TE that are defined in [RFC3630], [RFC4202], and [RFC4203].
+ The enhancements to the TE properties of GMPLS TE links can be
+ advertised in OSPF-TE Link State Advertisements (LSAs). The TE LSA,
+ which is an opaque LSA with area flooding scope [RFC3630], has only
+ one top-level Type-Length-Value (TLV) triplet and has one or more
+ nested sub-TLVs for extensibility. The top-level TLV can take one of
+ three values: Router Address [RFC3630], Link [RFC3630], or Node
+ Attribute [RFC5786]. In this document, we enhance the sub-TLVs for
+ the Link TLV in support of the general network element constraints
+ under the control of GMPLS.
+
+ The detailed encoding of OSPF extensions is not defined in this
+ document. [RFC7579] provides encoding details.
+
+1.1. 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].
+
+2. Node Information
+
+ According to [RFC7579], the additional node information representing
+ node switching asymmetry constraints includes device type and
+ connectivity matrix. Except for the device type, which is defined in
+ [RFC7579], the other pieces of information are defined in this
+ document.
+
+
+
+
+Zhang, et al. Standards Track [Page 3]
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+
+ Per [RFC7579], this document defines the Connectivity Matrix sub-TLV
+ of the Node Attribute TLV defined in [RFC5786]. The new sub-TLV has
+ Type 14.
+
+ Depending on the control-plane implementation being used, the
+ Connectivity Matrix sub-TLV may be optional in some specific
+ technologies, e.g., WSON networks. Usually, for example, in WSON
+ networks, the Connectivity Matrix sub-TLV may be advertised in the
+ LSAs since WSON switches are currently asymmetric. If no
+ Connectivity Matrix sub-TLV is included, it is assumed that the
+ switches support symmetric switching.
+
+2.1. Connectivity Matrix
+
+ If the switching devices supporting certain data-plane technology are
+ asymmetric, it is necessary to identify which input ports and labels
+ can be switched to some specific labels on a specific output port.
+
+ The connectivity matrix, which can represent either the potential
+ connectivity matrix for asymmetric switches (e.g., Reconfigurable
+ Optical Add/Drop Multiplexers (ROADMs) and such) or fixed
+ connectivity for an asymmetric device such as a multiplexer as
+ defined in [RFC7446], is used to identify these restrictions.
+
+ The Connectivity Matrix is a sub-TLV of the Node Attribute TLV. The
+ length is the length of the value field in octets. The meaning and
+ format of this sub-TLV value field are defined in Section 2.1 of
+ [RFC7579]. One sub-TLV contains one matrix. The Connectivity Matrix
+ sub-TLV may occur more than once to contain multiple matrices within
+ the Node Attribute TLV. In addition, a large connectivity matrix can
+ be decomposed into smaller sub-matrices for transmission in multiple
+ LSAs as described in Section 5.
+
+3. Link Information
+
+ The most common link sub-TLVs nested in the top-level Link TLV are
+ already defined in [RFC3630] and [RFC4203]. For example, Link ID,
+ Administrative Group, Interface Switching Capability Descriptor
+ (ISCD), Link Protection Type, Shared Risk Link Group (SRLG), and
+ Traffic Engineering Metric are among the typical link sub-TLVs.
+
+ Per [RFC7579], this document defines the Port Label Restrictions sub-
+ TLV of the Link TLV defined in [RFC3630]. The new sub-TLV has Type
+ 34.
+
+
+
+
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+Zhang, et al. Standards Track [Page 4]
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+
+ Generally, all the sub-TLVs above are optional, depending on control-
+ plane implementations being used. The Port Label Restrictions sub-
+ TLV will not be advertised when there are no restrictions on label
+ assignment.
+
+3.1. Port Label Restrictions
+
+ Port label restrictions describe the label restrictions that the
+ network element (node) and link may impose on a port. These
+ restrictions represent what labels may or may not be used on a link
+ and are intended to be relatively static. For increased modeling
+ flexibility, port label restrictions may be specified relative to the
+ port in general or to a specific connectivity matrix.
+
+ For example, the port label restrictions describe the wavelength
+ restrictions that the link and various optical devices such as
+ Optical Cross-Connects (OXCs), ROADMs, and waveband multiplexers may
+ impose on a port in WSON. These restrictions represent which
+ wavelengths may or may not be used on a link and are relatively
+ static. Detailed information about port label restrictions is
+ provided in [RFC7446].
+
+ The Port Label Restrictions sub-TLV is a sub-TLV of the Link TLV.
+ The length is the length of value field in octets. The meaning and
+ format of this sub-TLV value field are defined in Section 2.2 of
+ [RFC7579]. The Port Label Restrictions sub-TLV may occur more than
+ once to specify a complex port constraint within the Link TLV.
+
+4. Routing Procedures
+
+ All sub-TLVs are nested in top-level TLV(s) and contained in Opaque
+ LSAs. The flooding rules of Opaque LSAs are specified in [RFC2328],
+ [RFC5250], [RFC3630], and [RFC4203].
+
+ Considering the routing scalability issues in some cases, the routing
+ protocol should be capable of supporting the separation of dynamic
+ information from relatively static information to avoid unnecessary
+ updates of static information when dynamic information is changed. A
+ standards-compliant approach is to separate the dynamic information
+ sub-TLVs from the static information sub-TLVs, each nested in a
+ separate top-level TLV (see [RFC3630] and [RFC5786]), and advertise
+ them in the separate OSPF-TE LSAs.
+
+ For node information, since the connectivity matrix information is
+ static, the LSA containing the Node Attribute TLV can be updated with
+ a lower frequency to avoid unnecessary updates.
+
+
+
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+Zhang, et al. Standards Track [Page 5]
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+
+ For link information, a mechanism MAY be applied such that static
+ information and dynamic information of one TE link are contained in
+ separate Opaque LSAs. For example, the Port Label Restrictions sub-
+ TLV could be nested in separate top-level Link TLVs and advertised in
+ the separate LSAs.
+
+ As with other TE information, an implementation typically takes
+ measures to avoid rapid and frequent updates of routing information
+ that could cause the routing network to become swamped. See
+ Section 3 of [RFC3630] for related details.
+
+5. Scalability and Timeliness
+
+ This document defines two sub-TLVs for describing generic routing
+ constraints. The examples given in [RFC7579] show that very large
+ systems, in terms of label count or ports, can be very efficiently
+ encoded. However, because there has been concern expressed that some
+ possible systems may produce LSAs that exceed the IP Maximum
+ Transmission Unit (MTU), methods should be given to allow for the
+ splitting of general constraint LSAs into smaller LSAs that are under
+ the MTU limit. This section presents a set of techniques that can be
+ used for this purpose.
+
+5.1. Different Sub-TLVs into Multiple LSAs
+
+ Two sub-TLVs are defined in this document:
+
+ 1. Connectivity Matrix (carried in the Node Attribute TLV)
+
+ 2. Port Label Restrictions (carried in the Link TLV)
+
+ The Connectivity Matrix sub-TLV can be carried in the Node Attribute
+ TLV (as defined in [RFC5786]), whereas the Port Label Restrictions
+ sub-TLV can be carried in a Link TLV, of which there can be at most
+ one in an LSA (as defined in [RFC3630]). Note that the port label
+ restrictions are relatively static, i.e., only would change with
+ hardware changes or significant system reconfiguration.
+
+5.2. Decomposing a Connectivity Matrix into Multiple Matrices
+
+ In the highly unlikely event that a Connectivity Matrix sub-TLV by
+ itself would result in an LSA exceeding the MTU, a single large
+ matrix can be decomposed into sub-matrices. Per [RFC7579], a
+ connectivity matrix just consists of pairs of input and output ports
+ that can reach each other; hence, this decomposition would be
+ straightforward. Each of these sub-matrices would get a unique
+ matrix identifier per [RFC7579].
+
+
+
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+Zhang, et al. Standards Track [Page 6]
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+
+ From the point of view of a path computation process, prior to
+ receiving an LSA with a Connectivity Matrix sub-TLV, no connectivity
+ restrictions are assumed, i.e., the standard GMPLS assumption of any
+ port to any port reachability holds. Once a Connectivity Matrix sub-
+ TLV is received, path computation would know that connectivity is
+ restricted and use the information from all Connectivity Matrix sub-
+ TLVs received to understand the complete connectivity potential of
+ the system. Prior to receiving any Connectivity Matrix sub-TLVs,
+ path computation may compute a path through the system when, in fact,
+ no path exists. In between the reception of an additional
+ Connectivity Matrix sub-TLV, path computation may not be able to find
+ a path through the system when one actually exists. Both cases are
+ currently encountered and handled with existing GMPLS mechanisms.
+ Due to the reliability mechanisms in OSPF, the phenomena of late or
+ missing Connectivity Matrix sub-TLVs would be relatively rare.
+
+ In the case where the new sub-TLVs or their attendant encodings are
+ malformed, the proper action would be to log the problem and ignore
+ just the sub-TLVs in GMPLS path computations rather than ignoring the
+ entire LSA.
+
+6. Security Considerations
+
+ This document does not introduce any further security issues other
+ than those discussed in [RFC3630], [RFC4203], and [RFC5250].
+
+ For general security aspects relevant to GMPLS-controlled networks,
+ please refer to [RFC5920].
+
+7. Manageability
+
+ No existing management tools handle the additional TE parameters as
+ defined in this document and distributed in OSPF-TE. The existing
+ MIB module contained in [RFC6825] allows the TE information
+ distributed by OSPF-TE to be read from a network node; this MIB
+ module could be augmented (possibly by a sparse augmentation) to
+ report this new information.
+
+ The current environment in the IETF favors the Network Configuration
+ Protocol (NETCONF) [RFC6241] and YANG [RFC6020] over SNMP and MIB
+ modules. Work is in progress in the TEAS working group to develop a
+ YANG module to represent the generic TE information that may be
+ present in a Traffic Engineering Database (TED). This model may be
+ extended to handle the additional information described in this
+ document to allow that information to be read from network devices or
+ exchanged between consumers of the TED. Furthermore, links state
+
+
+
+
+
+Zhang, et al. Standards Track [Page 7]
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+
+ export using BGP [BGP-LS] enables the export of TE information from a
+ network using BGP. Work could realistically be done to extend BGP-LS
+ to also carry the information defined in this document.
+
+ It is not envisaged that the extensions defined in this document will
+ place substantial additional requirements on Operations,
+ Administration, and Maintenance (OAM) mechanisms currently used to
+ diagnose and debug OSPF systems. However, tools that examine the
+ contents of opaque LSAs will need to be enhanced to handle these new
+ sub-TLVs.
+
+8. IANA Considerations
+
+ IANA has allocated new sub-TLVs as defined in Sections 2 and 3 as
+ follows:
+
+8.1. Node Information
+
+ IANA maintains the "Open Shortest Path First (OSPF) Traffic
+ Engineering TLVs" registry with a sub-registry called "Types for sub-
+ TLVs of TE Node Attribute TLV (Value 5)". IANA has assigned a new
+ code point as follows:
+
+ Type | Sub-TLV | Reference
+ -------+-------------------------------+------------
+ 14 | Connectivity Matrix | [RFC7580]
+
+8.2. Link Information
+
+ IANA maintains the "Open Shortest Path First (OSPF) Traffic
+ Engineering TLVs" registry with a sub-registry called "Types for sub-
+ TLVs of TE Link TLV (Value 2)". IANA has assigned a new code point
+ as follows:
+
+ Type | Sub-TLV | Reference
+ -------+-------------------------------+------------
+ 34 | Port Label Restrictions | [RFC7580]
+
+
+
+
+
+
+
+
+
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+Zhang, et al. Standards Track [Page 8]
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+
+9. References
+
+9.1. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119,
+ DOI 10.17487/RFC2119, March 1997,
+ <http://www.rfc-editor.org/info/rfc2119>.
+
+ [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
+ DOI 10.17487/RFC2328, April 1998,
+ <http://www.rfc-editor.org/info/rfc2328>.
+
+ [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
+ (TE) Extensions to OSPF Version 2", RFC 3630,
+ DOI 10.17487/RFC3630, September 2003,
+ <http://www.rfc-editor.org/info/rfc3630>.
+
+ [RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
+ Extensions in Support of Generalized Multi-Protocol Label
+ Switching (GMPLS)", RFC 4202, DOI 10.17487/RFC4202,
+ October 2005, <http://www.rfc-editor.org/info/rfc4202>.
+
+ [RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
+ in Support of Generalized Multi-Protocol Label Switching
+ (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
+ <http://www.rfc-editor.org/info/rfc4203>.
+
+ [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
+ OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250,
+ July 2008, <http://www.rfc-editor.org/info/rfc5250>.
+
+ [RFC5786] Aggarwal, R. and K. Kompella, "Advertising a Router's
+ Local Addresses in OSPF Traffic Engineering (TE)
+ Extensions", RFC 5786, DOI 10.17487/RFC5786, March 2010,
+ <http://www.rfc-editor.org/info/rfc5786>.
+
+ [RFC7579] Bernstein, G., Ed., Lee, Y., Ed., Li, D., Imajuku, W., and
+ J. Han, "General Network Element Constraint Encoding for
+ GMPLS-Controlled Networks", RFC 7579,
+ DOI 10.17487/RFC7579, June 2015,
+ <http://www.rfc-editor.org/info/rfc7579>.
+
+
+
+
+
+
+
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+Zhang, et al. Standards Track [Page 9]
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+
+9.2. Informative References
+
+ [BGP-LS] Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
+ Ray, "North-Bound Distribution of Link-State and TE
+ Information using BGP", Work in Progress,
+ draft-ietf-idr-ls-distribution-11, June 2015.
+
+ [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
+ the Network Configuration Protocol (NETCONF)", RFC 6020,
+ DOI 10.17487/RFC6020, October 2010,
+ <http://www.rfc-editor.org/info/rfc6020>.
+
+ [RFC6163] Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
+ "Framework for GMPLS and Path Computation Element (PCE)
+ Control of Wavelength Switched Optical Networks (WSONs)",
+ RFC 6163, DOI 10.17487/RFC6163, April 2011,
+ <http://www.rfc-editor.org/info/rfc6163>.
+
+ [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
+ and A. Bierman, Ed., "Network Configuration Protocol
+ (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
+ <http://www.rfc-editor.org/info/rfc6241>.
+
+ [RFC6825] Miyazawa, M., Otani, T., Kumaki, K., and T. Nadeau,
+ "Traffic Engineering Database Management Information Base
+ in Support of MPLS-TE/GMPLS", RFC 6825,
+ DOI 10.17487/RFC6825, January 2013,
+ <http://www.rfc-editor.org/info/rfc6825>.
+
+ [RFC7446] Lee, Y., Ed., Bernstein, G., Ed., Li, D., and W. Imajuku,
+ "Routing and Wavelength Assignment Information Model for
+ Wavelength Switched Optical Networks", RFC 7446,
+ DOI 10.17487/RFC7446, February 2015,
+ <http://www.rfc-editor.org/info/rfc7446>.
+
+ [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
+ Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
+ <http://www.rfc-editor.org/info/rfc5920>.
+
+
+
+
+
+
+
+
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+Zhang, et al. Standards Track [Page 10]
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+
+Acknowledgments
+
+ We thank Ming Chen and Yabin Ye from DICONNET Project who provided
+ valuable information for this document.
+
+Contributors
+
+ Guoying Zhang
+ China Academy of Telecommunication Research of MII
+ 11 Yue Tan Nan Jie
+ Beijing
+ China
+ Phone: +86-10-68094272
+ EMail: zhangguoying@mail.ritt.com.cn
+
+ Dan Li
+ Huawei Technologies Co., Ltd.
+ F3-5-B R&D Center, Huawei Base
+ Bantian, Longgang District
+ Shenzhen 518129
+ China
+ Phone: +86-755-28973237
+ EMail: danli@huawei.com
+
+ Ming Chen
+ European Research Center
+ Huawei Technologies
+ Riesstr. 25, 80992
+ Munchen
+ Germany
+ Phone: 0049-89158834072
+ EMail: minc@huawei.com
+
+ Yabin Ye
+ European Research Center
+ Huawei Technologies
+ Riesstr. 25, 80992
+ Munchen
+ Germany
+ Phone: 0049-89158834074
+ EMail: yabin.ye@huawei.com
+
+
+
+
+
+
+
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+Zhang, et al. Standards Track [Page 11]
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+
+Authors' Addresses
+
+ Fatai Zhang
+ Huawei Technologies
+ F3-5-B R&D Center, Huawei Base
+ Bantian, Longgang District
+ Shenzhen 518129
+ China
+ Phone: +86-755-28972912
+ EMail: zhangfatai@huawei.com
+
+ Young Lee
+ Huawei Technologies
+ 5360 Legacy Drive, Building 3
+ Plano, TX 75023
+ United States
+ Phone: (469)277-5838
+ EMail: leeyoung@huawei.com
+
+ Jianrui Han
+ Huawei Technologies Co., Ltd.
+ F3-5-B R&D Center, Huawei Base
+ Bantian, Longgang District
+ Shenzhen 518129
+ China
+ Phone: +86-755-28977943
+ EMail: hanjianrui@huawei.com
+
+ Greg Bernstein
+ Grotto Networking
+ Fremont, CA
+ United States
+ Phone: (510) 573-2237
+ EMail: gregb@grotto-networking.com
+
+ Yunbin Xu
+ China Academy of Telecommunication Research of MII
+ 11 Yue Tan Nan Jie
+ Beijing
+ China
+ Phone: +86-10-68094134
+ EMail: xuyunbin@mail.ritt.com.cn
+
+
+
+
+
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+Zhang, et al. Standards Track [Page 12]
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