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diff --git a/doc/rfc/rfc6566.txt b/doc/rfc/rfc6566.txt new file mode 100644 index 0000000..6b751c3 --- /dev/null +++ b/doc/rfc/rfc6566.txt @@ -0,0 +1,1739 @@ + + + + + + +Internet Engineering Task Force (IETF) Y. Lee, Ed. +Request for Comments: 6566 Huawei +Category: Informational G. Bernstein, Ed. +ISSN: 2070-1721 Grotto Networking + D. Li + Huawei + G. Martinelli + Cisco + March 2012 + + + A Framework for the Control of + Wavelength Switched Optical Networks (WSONs) with Impairments + +Abstract + + As an optical signal progresses along its path, it may be altered by + the various physical processes in the optical fibers and devices it + encounters. When such alterations result in signal degradation, + these processes are usually referred to as "impairments". These + physical characteristics may be important constraints to consider + when using a GMPLS control plane to support path setup and + maintenance in wavelength switched optical networks. + + This document provides a framework for applying GMPLS protocols and + the Path Computation Element (PCE) architecture to support + Impairment-Aware Routing and Wavelength Assignment (IA-RWA) in + wavelength switched optical networks. Specifically, this document + discusses key computing constraints, scenarios, and architectural + processes: routing, wavelength assignment, and impairment validation. + This document does not define optical data plane aspects; impairment + parameters; or measurement of, or assessment and qualification of, a + route; rather, it describes the architectural and information + components for protocol solutions. + + + + + + + + + + + + + + + + + +Lee, et al. Informational [Page 1] + +RFC 6566 Framework for Optical Impairments March 2012 + + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + 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). Not all documents + approved by the IESG are a candidate for any level of Internet + Standard; see 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/rfc6566. + +Copyright Notice + + Copyright (c) 2012 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. + + + + + + + + + + + + + + + + + + + + + +Lee, et al. Informational [Page 2] + +RFC 6566 Framework for Optical Impairments March 2012 + + +Table of Contents + + 1. Introduction ....................................................3 + 2. Terminology .....................................................4 + 3. Applicability ...................................................6 + 4. Impairment-Aware Optical Path Computation .......................7 + 4.1. Optical Network Requirements and Constraints ...............8 + 4.1.1. Impairment-Aware Computation Scenarios ..............9 + 4.1.2. Impairment Computation and + Information-Sharing Constraints ....................10 + 4.1.3. Impairment Estimation Process ......................11 + 4.2. IA-RWA Computation and Control Plane Architectures ........13 + 4.2.1. Combined Routing, WA, and IV .......................15 + 4.2.2. Separate Routing, WA, or IV ........................15 + 4.2.3. Distributed WA and/or IV ...........................16 + 4.3. Mapping Network Requirements to Architectures .............16 + 5. Protocol Implications ..........................................19 + 5.1. Information Model for Impairments .........................19 + 5.2. Routing ...................................................20 + 5.3. Signaling .................................................21 + 5.4. PCE .......................................................21 + 5.4.1. Combined IV & RWA ..................................21 + 5.4.2. IV-Candidates + RWA ................................22 + 5.4.3. Approximate IA-RWA + Separate Detailed-IV ..........24 + 6. Manageability and Operations ...................................25 + 7. Security Considerations ........................................26 + 8. References .....................................................27 + 8.1. Normative References ......................................27 + 8.2. Informative References ....................................27 + 9. Contributors ...................................................29 + +1. Introduction + + Wavelength Switched Optical Networks (WSONs) are constructed from + subsystems that may include wavelength division multiplexed links, + tunable transmitters and receivers, Reconfigurable Optical Add/Drop + Multiplexers (ROADMs), wavelength converters, and electro-optical + network elements. A WSON is a Wavelength Division Multiplexing + (WDM)-based optical network in which switching is performed + selectively based on the center wavelength of an optical signal. + + As an optical signal progresses along its path, it may be altered by + the various physical processes in the optical fibers and devices it + encounters. When such alterations result in signal degradation, + these processes are usually referred to as "impairments". Optical + impairments accumulate along the path (without 3R regeneration + [G.680]) traversed by the signal. They are influenced by the type of + fiber used, the types and placement of various optical devices, and + + + +Lee, et al. Informational [Page 3] + +RFC 6566 Framework for Optical Impairments March 2012 + + + the presence of other optical signals that may share a fiber segment + along the signal's path. The degradation of the optical signals due + to impairments can result in unacceptable bit error rates or even a + complete failure to demodulate and/or detect the received signal. + + In order to provision an optical connection (an optical path) through + a WSON, a combination of path continuity, resource availability, and + impairment constraints must be met to determine viable and optimal + paths through the network. The determination of appropriate paths is + known as Impairment-Aware Routing and Wavelength Assignment (IA-RWA). + + Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] provides + a set of control plane protocols that can be used to operate networks + ranging from packet switch capable networks to those networks that + use time division multiplexing and WDM. The Path Computation Element + (PCE) architecture [RFC4655] defines functional computation + components that can be used in cooperation with the GMPLS control + plane to compute and suggest appropriate paths. [RFC4054] provides + an overview of optical impairments and their routing (path selection) + implications for GMPLS. This document uses [G.680] and other ITU-T + Recommendations as references for the optical data plane aspects. + + This document provides a framework for applying GMPLS protocols and + the PCE architecture to the control and operation of IA-RWA for + WSONs. To aid in this evaluation, this document provides an overview + of the subsystems and processes that comprise WSONs and describes + IA-RWA models based on the corresponding ITU-T Recommendations, so + that the information requirements for use by GMPLS and PCE systems + can be identified. This work will facilitate the development of + protocol extensions in support of IA-RWA within the GMPLS and PCE + protocol families. + +2. Terminology + + ADM: Add/Drop Multiplexer. An optical device used in WDM networks + and composed of one or more line side ports and, typically, many + tributary ports. + + Black Links: Black links refer to tributary interfaces where only + link characteristics are defined. This approach enables + transverse compatibility at the single-channel point using a + direct wavelength-multiplexing configuration. + + CWDM: Coarse Wavelength Division Multiplexing + + DGD: Differential Group Delay + + DWDM: Dense Wavelength Division Multiplexing + + + +Lee, et al. Informational [Page 4] + +RFC 6566 Framework for Optical Impairments March 2012 + + + FOADM: Fixed Optical Add/Drop Multiplexer + + GMPLS: Generalized Multi-Protocol Label Switching + + IA-RWA: Impairment-Aware Routing and Wavelength Assignment + + Line Side: In a WDM system, line side ports and links typically can + carry the full multiplex of wavelength signals, as compared to + tributary (add or drop ports), which typically carry a few + (typically one) wavelength signals. + + NEs: Network Elements + + OADMs: Optical Add/Drop Multiplexers + + OSNR: Optical Signal-to-Noise Ratio + + OXC: Optical Cross-Connect. An optical switching element in which a + signal on any input port can reach any output port. + + PCC: Path Computation Client. Any client application requesting that + a path computation be performed by the Path Computation Element. + + PCE: Path Computation Element. An entity (component, application, or + network node) that is capable of computing a network path or route + based on a network graph and application of computational + constraints. + + PCEP: PCE Communication Protocol. The communication protocol between + a Path Computation Client and Path Computation Element. + + PXC: Photonic Cross-Connect + + Q-Factor: The Q-factor provides a qualitative description of the + receiver performance. It is a function of the optical signal-to- + noise ratio. The Q-factor suggests the minimum SNR (Signal-to- + Noise Ratio) required to obtain a specific bit error rate (BER) + for a given signal. + + ROADM: Reconfigurable Optical Add/Drop Multiplexer. A wavelength- + selective switching element featuring input and output line side + ports as well as add/drop tributary ports. + + RWA: Routing and Wavelength Assignment + + Transparent Network: A Wavelength Switched Optical Network that does + not contain regenerators or wavelength converters. + + + + +Lee, et al. Informational [Page 5] + +RFC 6566 Framework for Optical Impairments March 2012 + + + Translucent Network: A Wavelength Switched Optical Network that is + predominantly transparent but may also contain limited numbers of + regenerators and/or wavelength converters. + + Tributary: A link or port on a WDM system that can carry + significantly less than the full multiplex of wavelength signals + found on the line side links/ports. Typical tributary ports are + the add and drop ports on an ADM, and these support only a single + wavelength channel. + + Wavelength Conversion/Converters: The process of converting an + information-bearing optical signal centered at a given wavelength + to information 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 + + Wavelength Switched Optical Networks (WSONs): WDM-based optical + networks in which switching is performed selectively based on the + center wavelength of an optical signal. + +3. Applicability + + There are deployment scenarios for WSONs where not all possible paths + will yield suitable signal quality. There are multiple reasons; + below is a non-exhaustive list of examples: + + o WSONs are evolving and are using multi-degree optical cross- + connects in such a way that network topologies are changing from + rings (and interconnected rings) to general mesh. Adding network + equipment such as amplifiers or regenerators to ensure that all + paths are feasible leads to an over-provisioned network. Indeed, + even with over-provisioning, the network could still have some + infeasible paths. + + o Within a given network, the optical physical interface may change + over the network's life; e.g., the optical interfaces might be + upgraded to higher bitrates. Such changes could result in paths + being unsuitable for the optical signal. Moreover, the optical + physical interfaces are typically provisioned at various stages of + the network's life span, as needed, by traffic demands. + + o There are cases where a network is upgraded by adding new optical + cross-connects to increase network flexibility. In such cases, + existing paths will have their feasibility modified while new + paths will need to have their feasibility assessed. + + + +Lee, et al. Informational [Page 6] + +RFC 6566 Framework for Optical Impairments March 2012 + + + o With the recent bitrate increases from 10G to 40G and 100G over a + single wavelength, WSONs will likely be operated with a mix of + wavelengths at different bitrates. This operational scenario will + impose impairment constraints due to different physical behavior + of different bitrates and associated modulation formats. + + Not having an impairment-aware control plane for such networks will + require a more complex network design phase that needs to take into + account the evolving network status in terms of equipment and traffic + at the beginning stage. In addition, network operations such as path + establishment will require significant pre-design via non-control- + plane processes, resulting in significantly slower network + provisioning. + + It should be highlighted that the impact of impairments and use in + determination of path viability is not sufficiently well established + for general applicability [G.680]; it will depend on network + implementations. The use of an impairment-aware control plane, and + the set of information distributed, will need to be evaluated on a + case-by-case scenario. + +4. Impairment-Aware Optical Path Computation + + The basic criterion for path selection is whether one can + successfully transmit the signal from a transmitter to a receiver + within a prescribed error tolerance, usually specified as a maximum + permissible BER. This generally depends on the nature of the signal + transmitted between the sender and receiver and the nature of the + communications channel between the sender and receiver. The optical + path utilized (along with the wavelength) determines the + communications channel. + + The optical impairments incurred by the signal along the fiber and at + each optical network element along the path determine whether the BER + performance or any other measure of signal quality can be met for a + signal on a particular end-to-end path. + + Impairment-aware path calculation also needs to take into account + when regeneration is used along the path. [RFC6163] provides + background on the concept of optical translucent networks that + contain transparent elements and electro-optical elements such as OEO + regenerations. In such networks, a generic light path can go through + a number of regeneration points. + + + + + + + + +Lee, et al. Informational [Page 7] + +RFC 6566 Framework for Optical Impairments March 2012 + + + Regeneration points could happen for two reasons: + + (i) Wavelength conversion is performed in order to assist RWA in + avoiding wavelength blocking. This is the impairment-free case + covered by [RFC6163]. + + (ii) The optical signal without regeneration would be too degraded to + meet end-to-end BER requirements. This is the case when RWA + takes into consideration impairment estimation covered by this + document. + + In the latter case, an optical path can be seen as a set of + transparent segments. The calculation of optical impairments needs + to be reset at each regeneration point so each transparent segment + will have its own impairment evaluation. + + +---+ +----+ +----+ +-----+ +----+ +---+ + | I |----| N1 |---| N2 |-----| REG |-----| N3 |----| E | + +---+ +----+ +----+ +-----+ +----+ +---+ + + |<----------------------------->|<-------------------->| + Segment 1 Segment 2 + + Figure 1. Optical Path as a Set of Transparent Segments + + For example, Figure 1 represents an optical path from node I to + node E with a regeneration point, REG, in between. This is feasible + from an impairment validation perspective if both segments (I, N1, + N2, REG) and (REG, N3, E) are feasible. + +4.1. Optical Network Requirements and Constraints + + This section examines the various optical network requirements and + constraints under which an impairment-aware optical control plane may + have to operate. These requirements and constraints motivate the + IA-RWA architectural alternatives presented in Section 4.2. + Different optical network contexts can be broken into two main + criteria: (a) the accuracy required in the estimation of impairment + effects and (b) the constraints on the impairment estimation + computation and/or sharing of impairment information. + + + + + + + + + + + +Lee, et al. Informational [Page 8] + +RFC 6566 Framework for Optical Impairments March 2012 + + +4.1.1. Impairment-Aware Computation Scenarios + + A. No Concern for Impairments or Wavelength Continuity Constraints + + This situation is covered by existing GMPLS with local wavelength + (label) assignment. + + B. No Concern for Impairments, but Wavelength Continuity Constraints + + This situation is applicable to networks designed such that every + possible path is valid for the signal types permitted on the + network. In this case, impairments are only taken into account + during network design; after that -- for example, during optical + path computation -- they can be ignored. This is the case + discussed in [RFC6163] where impairments may be ignored by the + control plane and only optical parameters related to signal + compatibility are considered. + + C. Approximated Impairment Estimation + + This situation is applicable to networks in which impairment + effects need to be considered but where there is a sufficient + margin such that impairment effects can be estimated via such + approximation techniques as link budgets and dispersion [G.680] + [G.Sup39]. The viability of optical paths for a particular class + of signals can be estimated using well-defined approximation + techniques [G.680] [G.Sup39]. This is generally known as the + linear case, where only linear effects are taken into account. + Note that adding or removing an optical signal on the path should + not render any of the existing signals in the network non-viable. + For example, one form of non-viability is the occurrence in + existing links of transients of sufficient magnitude to impact the + BER of existing signals. + + Much work at ITU-T has gone into developing impairment models at + this level and at more detailed levels. Impairment + characterization of network elements may be used to calculate + which paths are conformant with a specified BER for a particular + signal type. In such a case, the impairment-aware (IA) path + computation can be combined with the RWA process to permit more + optimal IA-RWA computations. Note that the IA path computation + may also take place in a separate entity, i.e., a PCE. + + + + + + + + + +Lee, et al. Informational [Page 9] + +RFC 6566 Framework for Optical Impairments March 2012 + + + D. Accurate Impairment Computation + + This situation is applicable to networks in which impairment + effects must be more accurately computed. For these networks, a + full computation and evaluation of the impact to any existing + paths need to be performed prior to the addition of a new path. + Currently, no impairment models are available from ITU-T, and this + scenario is outside the scope of this document. + +4.1.2. Impairment Computation and Information-Sharing Constraints + + In GMPLS, information used for path computation is standardized for + distribution amongst the elements participating in the control plane, + and any appropriately equipped PCE can perform path computation. For + optical systems, this may not be possible. This is typically due to + only portions of an optical system being subject to standardization. + In ITU-T Recommendations [G.698.1] and [G.698.2], which specify + single-channel interfaces to multi-channel DWDM systems, only the + single-channel interfaces (transmit and receive) are specified, while + the multi-channel links are not standardized. These DWDM links are + referred to as "black links", since their details are not generally + available. However, note that the overall impact of a black link at + the single-channel interface points is limited by [G.698.1] and + [G.698.2]. + + Typically, a vendor might use proprietary impairment models for DWDM + spans in order to estimate the validity of optical paths. For + example, models of optical nonlinearities are not currently + standardized. Vendors may also choose not to publish impairment + details for links or a set of network elements, in order not to + divulge their optical system designs. + + In general, the impairment estimation/validation of an optical path + for optical networks with black links in the path could not be + performed by a general-purpose IA computation entity, since it would + not have access to or understand the black-link impairment + parameters. However, impairment estimation (optical path validation) + could be performed by a vendor-specific IA computation entity. Such + a vendor-specific IA computation entity could utilize standardized + impairment information imported from other network elements in these + proprietary computations. + + In the following, the term "black links" will be used to describe + these computation and information-sharing constraints in optical + networks. From the control plane perspective, the following options + are considered: + + + + + +Lee, et al. Informational [Page 10] + +RFC 6566 Framework for Optical Impairments March 2012 + + + 1. The authority in control of the black links can furnish a list of + all viable paths between all viable node pairs to a computation + entity. This information would be particularly useful as an input + to RWA optimization to be performed by another computation entity. + The difficulty here is that such a list of paths, along with any + wavelength constraints, could get unmanageably large as the size + of the network increases. + + 2. The authority in control of the black links could provide a + PCE-like entity a list of viable paths/wavelengths between two + requested nodes. This is useful as an input to RWA optimizations + and can reduce the scaling issue previously mentioned. Such a + PCE-like entity would not need to perform a full RWA computation; + i.e., it would not need to take into account current wavelength + availability on links. Such an approach may require PCEP + extensions for both the request and response information. + + 3. The authority in control of the black links provides a PCE that + performs full IA-RWA services. The difficulty here is that this + option requires the one authority to also become the sole source + of all RWA optimization algorithms. + + In all of the above cases, it would be the responsibility of the + authority in control of the black links to import the shared + impairment information from the other NEs via the control plane or + other means as necessary. + +4.1.3. Impairment Estimation Process + + The impairment estimation process can be modeled through the + following functional blocks. These blocks are independent of any + control plane architecture; that is, they can be implemented by the + same or by different control plane functions, as detailed in the + following sections. + + + + + + + + + + + + + + + + + +Lee, et al. Informational [Page 11] + +RFC 6566 Framework for Optical Impairments March 2012 + + + +-----------------+ + +------------+ +-----------+ | +------------+ | + | | | | | | | | + | Optical | | Optical | | | Optical | | + | Interface |------->| Impairment|--->| | Channel | | + | (Transmit/ | | Path | | | Estimation | | + | Receive) | | | | | | | + +------------+ +-----------+ | +------------+ | + | || | + | || | + | Estimation | + | || | + | \/ | + | +------------+ | + | | BER/ | | + | | Q Factor | | + | +------------+ | + +-----------------+ + + Starting from the functional block on the left, the optical interface + represents where the optical signal is transmitted or received and + defines the properties at the path endpoints. Even the impairment- + free case, such as scenario B in Section 4.1.1, needs to consider a + minimum set of interface characteristics. In such a case, only a few + parameters used to assess the signal compatibility will be taken into + account (see [RFC6163]). For the impairment-aware case, these + parameters may be sufficient or not, depending on the accepted level + of approximation (scenarios C and D). This functional block + highlights the need to consider a set of interface parameters during + the impairment validation process. + + The "Optical Impairment Path" block represents the types of + impairments affecting a wavelength as it traverses the networks + through links and nodes. In the case of a network where there are no + impairments (scenario A), this block will not be present. Otherwise, + this function must be implemented in some way via the control plane. + Architectural alternatives to accomplish this are provided in + Section 4.2. This block implementation (e.g., through routing, + signaling, or a PCE) may influence the way the control plane + distributes impairment information within the network. + + The last block implements the decision function for path feasibility. + Depending on the IA level of approximation, this function can be more + or less complex. For example, in the case of no IA approximation, + only the signal class compatibility will be verified. In addition to + a feasible/not-feasible result, it may be worthwhile for decision + functions to consider the case in which paths would likely be + feasible within some degree of confidence. The optical impairments + + + +Lee, et al. Informational [Page 12] + +RFC 6566 Framework for Optical Impairments March 2012 + + + are usually not fixed values, as they may vary within ranges of + values according to the approach taken in the physical modeling + (worst-case, statistical, or based on typical values). For example, + the utilization of the worst-case value for each parameter within the + impairment validation process may lead to marking some paths as not + feasible, while they are very likely to be, in reality, feasible. + +4.2. IA-RWA Computation and Control Plane Architectures + + From a control plane point of view, optical impairments are + additional constraints to the impairment-free RWA process described + in [RFC6163]. In IA-RWA, there are conceptually three general + classes of processes to be considered: Routing (R), Wavelength + Assignment (WA), and Impairment Validation (IV), i.e., estimation. + + Impairment validation may come in many forms and may be invoked at + different levels of detail in the IA-RWA process. All of the + variations of impairment validation discussed in this section are + based on scenario C ("Approximated Impairment Estimation") as + discussed in Section 4.1.1. From a process point of view, the + following three forms of impairment validation will be considered: + + o IV-Candidates + + In this case, an IV process furnishes a set of paths between two + nodes along with any wavelength restrictions, such that the paths + are valid with respect to optical impairments. These paths and + wavelengths may not actually be available in the network, due to + its current usage state. This set of paths could be returned in + response to a request for a set of at most K valid paths between + two specified nodes. Note that such a process never directly + discloses optical impairment information. Note also that this + case includes any paths between the source and destination that + may have been "pre-validated". + + In this case, the control plane simply makes use of candidate + paths but does not have any optical impairment information. + Another option is when the path validity is assessed within the + control plane. The following cases highlight this situation. + + o IV-Approximate Verification + + Here, approximation methods are used to estimate the impairments + experienced by a signal. Impairments are typically approximated + by linear and/or statistical characteristics of individual or + combined components and fibers along the signal path. + + + + + +Lee, et al. Informational [Page 13] + +RFC 6566 Framework for Optical Impairments March 2012 + + + o IV-Detailed Verification + + In this case, an IV process is given a particular path and + wavelength through an optical network and is asked to verify + whether the overall quality objectives for the signal over this + path can be met. Note that such a process never directly + discloses optical impairment information. + + The next two cases refer to the way an impairment validation + computation can be performed from a decision-making point of view. + + o IV-Centralized + + In this case, impairments to a path are computed at a single + entity. The information concerning impairments, however, may + still be gathered from network elements. Depending on how + information is gathered, this may put additional requirements on + routing protocols. This topic will be detailed in later sections. + + o IV-Distributed + + In the distributed IV process, approximate degradation measures + such as OSNR, dispersion, DGD, etc., may be accumulated along the + path via signaling. Each node on the path may already perform + some part of the impairment computation (i.e., distributed). When + the accumulated measures reach the destination node, a decision on + the impairment validity of the path can be made. Note that such a + process would entail revealing an individual network element's + impairment information, but it does not generally require + distributing optical parameters to the entire network. + + The control plane must not preclude the possibility of concurrently + performing one or all of the above cases in the same network. For + example, there could be cases where a certain number of paths are + already pre-validated (IV-Candidates), so the control plane may set + up one of those paths without requesting any impairment validation + procedure. On the same network, however, the control plane may + compute a path outside the set of IV-Candidates for which an + impairment evaluation can be necessary. + + The following subsections present three major classes of IA-RWA path + computation architectures and review some of their respective + advantages and disadvantages. + + + + + + + + +Lee, et al. Informational [Page 14] + +RFC 6566 Framework for Optical Impairments March 2012 + + +4.2.1. Combined Routing, WA, and IV + + From the point of view of optimality, reasonably good IA-RWA + solutions can be achieved if the PCE can conceptually/algorithmically + combine the processes of routing, wavelength assignment, and + impairment validation. + + Such a combination can take place if the PCE is given (a) the + impairment-free WSON information as discussed in [RFC6163] and (b) + impairment information to validate potential paths. + +4.2.2. Separate Routing, WA, or IV + + Separating the processes of routing, WA, and/or IV can reduce the + need for the sharing of different types of information used in path + computation. This was discussed for routing, separate from WA, in + [RFC6163]. In addition, as was discussed in Section 4.1.2, some + impairment information may not be shared, and this may lead to the + need to separate IV from RWA. In addition, if IV needs to be done at + a high level of precision, it may be advantageous to offload this + computation to a specialized server. + + The following conceptual architectures belong in this general + category: + + o R + WA + IV + separate routing, wavelength assignment, and impairment + validation. + + o R + (WA & IV) + routing separate from a combined wavelength assignment and + impairment validation process. Note that impairment validation is + typically wavelength dependent. Hence, combining WA with IV can + lead to improved efficiency. + + o (RWA) + IV + combined routing and wavelength assignment with a separate + impairment validation process. + + Note that the IV process may come before or after the RWA processes. + If RWA comes first, then IV is just rendering a yes/no decision on + the selected path and wavelength. If IV comes first, it would need + to furnish a list of possible (valid with respect to impairments) + routes and wavelengths to the RWA processes. + + + + + + + +Lee, et al. Informational [Page 15] + +RFC 6566 Framework for Optical Impairments March 2012 + + +4.2.3. Distributed WA and/or IV + + In the non-impairment RWA situation [RFC6163], it was shown that a + distributed WA process carried out via signaling can eliminate the + need to distribute wavelength availability information via an + interior gateway protocol (IGP). A similar approach can allow for + the distributed computation of impairment effects and avoid the need + to distribute impairment characteristics of network elements and + links by routing protocols or by other means. Therefore, the + following conceptual options belong to this category: + + o RWA + D(IV) + combined routing and wavelength assignment and distributed + impairment validation. + + o R + D(WA & IV) + routing separate from a distributed wavelength assignment and + impairment validation process. + + Distributed impairment validation for a prescribed network path + requires that the effects of impairments be calculated by approximate + models with cumulative quality measures such as those given in + [G.680]. The protocol encoding of the impairment-related information + from [G.680] would need to be agreed upon. + + If distributed WA is being done at the same time as distributed IV, + then it is necessary to accumulate impairment-related information for + all wavelengths that could be used. The amount of information is + reduced somewhat as potential wavelengths are discovered to be in use + but could be a significant burden for lightly loaded networks with + high channel counts. + +4.3. Mapping Network Requirements to Architectures + + Figure 2 shows process flows for the three main architectural + alternatives to IA-RWA that apply when approximate impairment + validation is sufficient. Figure 3 shows process flows for the two + main architectural alternatives that apply when detailed impairment + verification is required. + + + + + + + + + + + + +Lee, et al. Informational [Page 16] + +RFC 6566 Framework for Optical Impairments March 2012 + + + +-----------------------------------+ + | +--+ +-------+ +--+ | + | |IV| |Routing| |WA| | + | +--+ +-------+ +--+ | + | | + | Combined Processes | + +-----------------------------------+ + (a) + + +--------------+ +----------------------+ + | +----------+ | | +-------+ +--+ | + | | IV | | | |Routing| |WA| | + | |Candidates| |----->| +-------+ +--+ | + | +----------+ | | Combined Processes | + +--------------+ +----------------------+ + (b) + + +-----------+ +----------------------+ + | +-------+ | | +--+ +--+ | + | |Routing| |------->| |WA| |IV| | + | +-------+ | | +--+ +--+ | + +-----------+ | Distributed Processes| + +----------------------+ + (c) + + Figure 2. Process Flows for the Three Main Approximate Impairment + Architectural Alternatives + + The advantages, requirements, and suitability of these options are as + follows: + + o Combined IV & RWA process + + This alternative combines RWA and IV within a single computation + entity, enabling highest potential optimality and efficiency in + IA-RWA. This alternative requires that the computation entity + have impairment information as well as non-impairment RWA + information. This alternative can be used with black links but + would then need to be provided by the authority controlling the + black links. + + o IV-Candidates + RWA process + + This alternative allows separation of impairment information into + two computation entities while still maintaining a high degree of + potential optimality and efficiency in IA-RWA. The IV-Candidates + process needs to have impairment information from all optical + network elements, while the RWA process needs to have + + + +Lee, et al. Informational [Page 17] + +RFC 6566 Framework for Optical Impairments March 2012 + + + non-impairment RWA information from the network elements. This + alternative can be used with black links, but the authority in + control of the black links would need to provide the functionality + of the IV-Candidates process. Note that this is still very + useful, since the algorithmic areas of IV and RWA are very + different and conducive to specialization. + + o Routing + Distributed WA and IV + + In this alternative, a signaling protocol may be extended and + leveraged in the wavelength assignment and impairment validation + processes. Although this doesn't enable as high a potential + degree of optimality as (a) or (b), it does not require + distribution of either link wavelength usage or link/node + impairment information. Note that this is most likely not + suitable for black links. + + +-----------------------------------+ +------------+ + | +-----------+ +-------+ +--+ | | +--------+ | + | | IV | |Routing| |WA| | | | IV | | + | |Approximate| +-------+ +--+ |---->| |Detailed| | + | +-----------+ | | +--------+ | + | Combined Processes | | | + +-----------------------------------+ +------------+ + (a) + + +--------------+ +----------------------+ +------------+ + | +----------+ | | +-------+ +--+ | | +--------+ | + | | IV | | | |Routing| |WA| |---->| | IV | | + | |Candidates| |----->| +-------+ +--+ | | |Detailed| | + | +----------+ | | Combined Processes | | +--------+ | + +--------------+ +----------------------+ | | + (b) +------------+ + + Figure 3. Process Flows for the Two Main Detailed Impairment + Validation Architectural Options + + The advantages, requirements, and suitability of these detailed + validation options are as follows: + + o Combined Approximate IV & RWA + Detailed-IV + + This alternative combines RWA and approximate IV within a single + computation entity, enabling the highest potential optimality and + efficiency in IA-RWA while keeping a separate entity performing + detailed impairment validation. In the case of black links, the + authority controlling the black links would need to provide all + functionality. + + + +Lee, et al. Informational [Page 18] + +RFC 6566 Framework for Optical Impairments March 2012 + + + o IV-Candidates + RWA + Detailed-IV + + This alternative allows separation of approximate impairment + information into a computation entity while still maintaining a + high degree of potential optimality and efficiency in IA-RWA; + then, a separate computation entity performs detailed impairment + validation. Note that detailed impairment estimation is not + standardized. + +5. Protocol Implications + + The previous IA-RWA architectural alternatives and process flows make + differing demands on a GMPLS/PCE-based control plane. This section + discusses the use of (a) an impairment information model, (b) the PCE + as computation entity assuming the various process roles and + consequences for PCEP, (c) possible extensions to signaling, and + (d) possible extensions to routing. This document is providing this + evaluation to aid protocol solutions work. The protocol + specifications may deviate from this assessment. The assessment of + the impacts to the control plane for IA-RWA is summarized in + Figure 4. + + +--------------------+-----+-----+------------+---------+ + | IA-RWA Option | PCE | Sig | Info Model | Routing | + +--------------------+-----+-----+------------+---------+ + | Combined | Yes | No | Yes | Yes | + | IV & RWA | | | | | + +--------------------+-----+-----+------------+---------+ + | IV-Candidates | Yes | No | Yes | Yes | + | + RWA | | | | | + +--------------------+-----+-----+------------+---------+ + | Routing + | No | Yes | Yes | No | + |Distributed IV, RWA | | | | | + +--------------------+-----+-----+------------+---------+ + + Figure 4. IA-RWA Architectural Options and Control Plane Impacts + +5.1. Information Model for Impairments + + As previously discussed, most IA-RWA scenarios rely, to a greater or + lesser extent, on a common impairment information model. A number of + ITU-T Recommendations cover both detailed and approximate impairment + characteristics of fibers, a variety of devices, and a variety of + subsystems. An impairment model that can be used as a guideline for + optical network elements and assessment of path viability is given + in [G.680]. + + + + + +Lee, et al. Informational [Page 19] + +RFC 6566 Framework for Optical Impairments March 2012 + + + It should be noted that the current version of [G.680] is limited to + networks composed of a single WDM line system vendor combined with + OADMs and/or PXCs from potentially multiple other vendors. This is + known as "situation 1" and is shown in Figure 1-1 of [G.680]. It is + planned in the future that [G.680] will include networks + incorporating line systems from multiple vendors, as well as OADMs + and/or PXCs from potentially multiple other vendors. This is known + as "situation 2" and is shown in Figure 1-2 of [G.680]. + + For the case of distributed IV, this would require more than an + impairment information model. It would need a common impairment + "computation" model. In the distributed IV case, one needs to + standardize the accumulated impairment measures that will be conveyed + and updated at each node. Section 9 of [G.680] provides guidance in + this area, with specific formulas given for OSNR, residual + dispersion, polarization mode dispersion/polarization-dependent loss, + and effects of channel uniformity. However, specifics of what + intermediate results are kept and in what form would need to be + standardized for interoperability. As noted in [G.680], this + information may possibly not be sufficient, and in such a case, the + applicability would be network dependent. + +5.2. Routing + + Different approaches to path/wavelength impairment validation give + rise to different demands placed on GMPLS routing protocols. In the + case where approximate impairment information is used to validate + paths, GMPLS routing may be used to distribute the impairment + characteristics of the network elements and links based on the + impairment information model previously discussed. + + Depending on the computational alternative, the routing protocol may + need to advertise information necessary to the impairment validation + process. This can potentially cause scalability issues, due to the + high volume of data that need to be advertised. Such issues can be + addressed by separating data that need to be advertised only rarely + from data that need to be advertised more frequently, or by adopting + other forms of awareness solutions as described in previous sections + (e.g., a centralized and/or external IV entity). + + In terms of scenario C in Section 4.1.1, the model defined by [G.680] + will apply, and the routing protocol will need to gather information + required for such computations. + + In the case of distributed IV, no new demands would be placed on the + routing protocol. + + + + + +Lee, et al. Informational [Page 20] + +RFC 6566 Framework for Optical Impairments March 2012 + + +5.3. Signaling + + The largest impacts on signaling occur in the cases where distributed + impairment validation is performed. In this case, it is necessary to + accumulate impairment information, as previously discussed. In + addition, since the characteristics of the signal itself, such as + modulation type, can play a major role in the tolerance of + impairments, this type of information will need to be implicitly or + explicitly signaled so that an impairment validation decision can be + made at the destination node. + + It remains for further study whether it may be beneficial to include + additional information to a connection request, such as desired + egress signal quality (defined in some appropriate sense) in + non-distributed IV scenarios. + +5.4. PCE + + In Section 4.2, a number of computational architectural alternatives + were given that could be used to meet the various requirements and + constraints of Section 4.1. Here, the focus is on how these + alternatives could be implemented via either a single PCE or a set of + two or more cooperating PCEs, and the impacts on the PCEP. This + document provides this evaluation to aid solutions work. The + protocol specifications may deviate from this assessment. + +5.4.1. Combined IV & RWA + + In this situation, shown in Figure 2(a), a single PCE performs all of + the computations needed for IA-RWA. + + o Traffic Engineering (TE) Database requirements: WSON topology and + switching capabilities, WSON WDM link wavelength utilization, and + WSON impairment information. + + o PCC to PCE Request Information: Signal characteristics/type, + required quality, source node, and destination node. + + o PCE to PCC Reply Information: If the computations completed + successfully, then the PCE returns the path and its assigned + wavelength. If the computations could not complete successfully, + it would be potentially useful to know why. At a minimum, it is + of interest to know if this was due to lack of wavelength + availability, impairment considerations, or both. The information + to be conveyed is for further study. + + + + + + +Lee, et al. Informational [Page 21] + +RFC 6566 Framework for Optical Impairments March 2012 + + +5.4.2. IV-Candidates + RWA + + In this situation, as shown in Figure 2(b), two separate processes + are involved in the IA-RWA computation. This requires two + cooperating path computation entities: one for the IV-Candidates + process and another for the RWA process. In addition, the overall + process needs to be coordinated. This could be done with yet another + PCE, or this functionality could be added to one of a number of + previously defined entities. This later option requires that the RWA + entity also act as the overall process coordinator. The roles, + responsibilities, and information requirements for these two + entities, when instantiated as PCEs, are given below. + + RWA and Coordinator PCE (RWA-Coord PCE): + + The RWA-Coord PCE is responsible for interacting with the PCC and + for utilizing the IV-Candidates PCE as needed during RWA + computations. In particular, it needs to know that it is to use + the IV-Candidates PCE to obtain a potential set of routes and + wavelengths. + + o TE Database requirements: WSON topology and switching + capabilities, and WSON WDM link wavelength utilization (no + impairment information). + + o PCC to RWA PCE request: same as in the combined case. + + o RWA PCE to PCC reply: same as in the combined case. + + o RWA PCE to IV-Candidates PCE request: The RWA PCE asks for a + set of at most K routes, along with acceptable wavelengths + between nodes specified in the original PCC request. + + o IV-Candidates PCE reply to RWA PCE: The IV-Candidates PCE + returns a set of at most K routes, along with acceptable + wavelengths between nodes specified in the RWA PCE request. + + IV-Candidates PCE: + + The IV-Candidates PCE is responsible for impairment-aware path + computation. It need not take into account current link + wavelength utilization, but this is not prohibited. The + IV-Candidates PCE is only required to interact with the RWA PCE as + indicated above, and not the initiating PCC. Note: The + RWA-Coord PCE is also a PCC with respect to the IV-Candidate. + + + + + + +Lee, et al. Informational [Page 22] + +RFC 6566 Framework for Optical Impairments March 2012 + + + o TE Database requirements: WSON topology and switching + capabilities, and WSON impairment information (no information + link wavelength utilization required). + + Figure 5 shows a sequence diagram for the possible interactions + between the PCC, RWA-Coord PCE, and IV-Candidates PCE. + + +---+ +-------------+ +-----------------+ + |PCC| |RWA-Coord PCE| |IV-Candidates PCE| + +-+-+ +------+------+ +---------+-------+ + ...___ (a) | | + | ````---...____ | | + | ```-->| | + | | | + | |--..___ (b) | + | | ```---...___ | + | | ```---->| + | | | + | | | + | | (c) ___...| + | | ___....---'''' | + | |<--'''' | + | | | + | | | + | (d) ___...| | + | ___....---''' | | + |<--''' | | + | | | + | | | + + Figure 5. Sequence Diagram for the Interactions between the PCC, + RWA-Coord PCE, and IV-Candidates PCE + + In step (a), the PCC requests a path that meets specified quality + constraints between two nodes (A and Z) for a given signal + represented either by a specific type or a general class with + associated parameters. In step (b), the RWA-Coord PCE requests up to + K candidate paths between nodes A and Z, and associated acceptable + wavelengths. The term "K candidate paths" is associated with the k + shortest path algorithm. It refers to an algorithm that finds + multiple k short paths connecting the source and the destination in a + graph allowing repeated vertices and edges in the paths. See details + in [Eppstein]. + + + + + + + + +Lee, et al. Informational [Page 23] + +RFC 6566 Framework for Optical Impairments March 2012 + + + In step (c), the IV-Candidates PCE returns this list to the + RWA-Coord PCE, which then uses this set of paths and wavelengths as + input (e.g., a constraint) to its RWA computation. In step (d), the + RWA-Coord PCE returns the overall IA-RWA computation results to + the PCC. + +5.4.3. Approximate IA-RWA + Separate Detailed-IV + + Previously, Figure 3 showed two cases where a separate detailed + impairment validation process could be utilized. It is possible to + place the detailed validation process into a separate PCE. Assuming + that a different PCE assumes a coordinating role and interacts with + the PCC, it is possible to keep the interactions with this separate + IV-Detailed PCE very simple. Note that, from a message flow + perspective, there is some inefficiency as a result of separating the + IV-Candidates PCE from the IV-Detailed PCE in order to achieve a high + degree of potential optimality. + + IV-Detailed PCE: + + o TE Database requirements: The IV-Detailed PCE will need optical + impairment information, WSON topology, and, possibly, WDM link + wavelength usage information. This document puts no restrictions + on the type of information that may be used in these computations. + + o RWA-Coord PCE to IV-Detailed PCE request: The RWA-Coord PCE will + furnish signal characteristics, quality requirements, path, and + wavelength to the IV-Detailed PCE. + + o IV-Detailed PCE to RWA-Coord PCE reply: The reply is essentially a + yes/no decision as to whether the requirements could actually be + met. In the case where the impairment validation fails, it would + be helpful to convey information related to the cause or to + quantify the failure, e.g., so that a judgment can be made + regarding whether to try a different signal or adjust signal + parameters. + + Figure 6 shows a sequence diagram for the interactions corresponding + to the process shown in Figure 3(b). This involves interactions + between the PCC, RWA PCE (acting as coordinator), IV-Candidates PCE, + and IV-Detailed PCE. + + In step (a), the PCC requests a path that meets specified quality + constraints between two nodes (A and Z) for a given signal + represented either by a specific type or a general class with + associated parameters. In step (b), the RWA-Coord PCE requests up to + K candidate paths between nodes A and Z, and associated acceptable + wavelengths. In step (c), the IV-Candidates PCE returns this list to + + + +Lee, et al. Informational [Page 24] + +RFC 6566 Framework for Optical Impairments March 2012 + + + the RWA-Coord PCE, which then uses this set of paths and wavelengths + as input (e.g., a constraint) to its RWA computation. In step (d), + the RWA-Coord PCE requests a detailed verification of the path and + wavelength that it has computed. In step (e), the IV-Detailed PCE + returns the results of the validation to the RWA-Coord PCE. Finally, + in step (f), the RWA-Coord PCE returns the final results (either a + path and wavelength, or a cause for the failure to compute a path and + wavelength) to the PCC. + + +----------+ +--------------+ +------------+ + +---+ |RWA-Coord | |IV-Candidates | |IV-Detailed | + |PCC| | PCE | | PCE | | PCE | + +-+-+ +----+-----+ +------+-------+ +-----+------+ + |.._ (a) | | | + | ``--.__ | | | + | `-->| | | + | | (b) | | + | |--....____ | | + | | ````---.>| | + | | | | + | | (c) __..-| | + | | __..---'' | | + | |<--'' | | + | | | + | |...._____ (d) | + | | `````-----....._____ | + | | `````----->| + | | | + | | (e) _____.....+ + | | _____.....-----''''' | + | |<----''''' | + | (f) __.| | + | __.--'' | + |<-'' | + | | + + Figure 6. Sequence Diagram for the Interactions between the PCC, + RWA-Coord PCE, IV-Candidates PCE, and IV-Detailed PCE + +6. Manageability and Operations + + The issues concerning manageability and operations are beyond the + scope of this document. The details of manageability and operational + issues will have to be deferred to future protocol implementations. + + + + + + + +Lee, et al. Informational [Page 25] + +RFC 6566 Framework for Optical Impairments March 2012 + + + On a high level, the GMPLS-routing-based architecture discussed in + Section 5.2 may have to deal with how to resolve potential scaling + issues associated with disseminating a large amount of impairment + characteristics of the network elements and links. + + From a scaling point of view, the GMPLS-signaling-based architecture + discussed in Section 5.3 would be more scalable than other + alternatives, as this architecture would avoid the dissemination of a + large amount of data to the networks. This benefit may come, + however, at the expense of potentially inefficient use of network + resources. + + The PCE-based architectures discussed in Section 5.4 would have to + consider operational complexity when implementing options that + require the use of multiple PCE servers. The most serious case is + the option discussed in Section 5.4.3 ("Approximate IA-RWA + Separate + Detailed-IV"). The combined IV & RWA option (which was discussed in + Section 5.4.1), on the other hand, is simpler to operate than are + other alternatives, as one PCE server handles all functionality; + however, this option may suffer from a heavy computation and + processing burden compared to other alternatives. + + Interoperability may be a hurdle to overcome when trying to agree on + some impairment parameters, especially those that are associated with + the black links. This work has been in progress in ITU-T and needs + some more time to mature. + +7. Security Considerations + + This document discusses a number of control plane architectures that + incorporate knowledge of impairments in optical networks. If such an + architecture is put into use within a network, it will by its nature + contain details of the physical characteristics of an optical + network. Such information would need to be protected from + intentional or unintentional disclosure, similar to other network + information used within intra-domain protocols. + + This document does not require changes to the security models within + GMPLS and associated protocols. That is, the OSPF-TE, RSVP-TE, and + PCEP security models could be operated unchanged. However, + satisfying the requirements for impairment information dissemination + using the existing protocols may significantly affect the loading of + those protocols and may make the operation of the network more + vulnerable to active attacks such as injections, impersonation, and + man-in-the-middle attacks. Therefore, additional care may be + required to ensure that the protocols are secure in the impairment- + aware WSON environment. + + + + +Lee, et al. Informational [Page 26] + +RFC 6566 Framework for Optical Impairments March 2012 + + + Furthermore, the additional information distributed in order to + address impairment information represents a disclosure of network + capabilities that an operator may wish to keep private. + Consideration should be given to securing this information. For a + general discussion on MPLS- and GMPLS-related security issues, see + the MPLS/GMPLS security framework [RFC5920] and, in particular, text + detailing security issues when the control plane is physically + separated from the data plane. + +8. References + +8.1. Normative References + + [G.680] ITU-T Recommendation G.680, "Physical transfer functions + of optical network elements", July 2007. + + [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label + Switching (GMPLS) Architecture", RFC 3945, October 2004. + + [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path + Computation Element (PCE)-Based Architecture", RFC 4655, + August 2006. + +8.2. Informative References + + [Eppstein] Eppstein, D., "Finding the k shortest paths", 35th IEEE + Symposium on Foundations of Computer Science, Santa Fe, + pp. 154-165, 1994. + + [G.698.1] ITU-T Recommendation G.698.1, "Multichannel DWDM + applications with single-channel optical interfaces", + November 2009. + + [G.698.2] ITU-T Recommendation G.698.2, "Amplified multichannel + dense wavelength division multiplexing applications with + single channel optical interfaces", November 2009. + + [G.Sup39] ITU-T Series G Supplement 39, "Optical system design and + engineering considerations", February 2006. + + [RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other + Constraints on Optical Layer Routing", RFC 4054, + May 2005. + + + + + + + + +Lee, et al. Informational [Page 27] + +RFC 6566 Framework for Optical Impairments March 2012 + + + [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS + Networks", RFC 5920, July 2010. + + [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, April 2011. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Lee, et al. Informational [Page 28] + +RFC 6566 Framework for Optical Impairments March 2012 + + +9. Contributors + + Ming Chen + 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: mchen@huawei.com + + + Rebecca Han + 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: hanjianrui@huawei.com + + + Gabriele Galimberti + Cisco + Via Philips 12 + 20052 Monza + Italy + + Phone: +39 039 2091462 + EMail: ggalimbe@cisco.com + + + Alberto Tanzi + Cisco + Via Philips 12 + 20052 Monza + Italy + + Phone: +39 039 2091469 + EMail: altanzi@cisco.com + + + + + + + + + +Lee, et al. Informational [Page 29] + +RFC 6566 Framework for Optical Impairments March 2012 + + + David Bianchi + Cisco + Via Philips 12 + 20052 Monza + Italy + + EMail: davbianc@cisco.com + + + Moustafa Kattan + Cisco + Dubai 500321 + United Arab Emirates + + EMail: mkattan@cisco.com + + + Dirk Schroetter + Cisco + + EMail: dschroet@cisco.com + + + Daniele Ceccarelli + Ericsson + Via A. Negrone 1/A + Genova - Sestri Ponente + Italy + + EMail: daniele.ceccarelli@ericsson.com + + + Elisa Bellagamba + Ericsson + Farogatan 6 + Kista 164 40 + Sweden + + EMail: elisa.bellagamba@ericsson.com + + + Diego Caviglia + Ericsson + Via A. Negrone 1/A + Genova - Sestri Ponente + Italy + + EMail: diego.caviglia@ericsson.com + + + +Lee, et al. Informational [Page 30] + +RFC 6566 Framework for Optical Impairments March 2012 + + +Authors' Addresses + + Young Lee (editor) + Huawei Technologies + 5340 Legacy Drive, Building 3 + Plano, TX 75024 + USA + + Phone: (469) 277-5838 + EMail: leeyoung@huawei.com + + + Greg M. Bernstein (editor) + Grotto Networking + Fremont, CA + USA + + Phone: (510) 573-2237 + EMail: gregb@grotto-networking.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 + + + Giovanni Martinelli + Cisco + Via Philips 12 + 20052 Monza + Italy + + Phone: +39 039 2092044 + EMail: giomarti@cisco.com + + + + + + + + + + + +Lee, et al. Informational [Page 31] + |