SDH / SONET Explained in Functional Models: Modeling the Optical Transport Network / Edition 1

by Huub van Helvoort

Overview

H/SONET Explained in Functional Models represents a fresh approach to the modeling of transport network technologies. This practical guide and reference text uncovers the description of SDH (Synchronous Digital Hierarchy), SONET (Synchronous Optical Network) and OTN (Optical Transport Network) transport networks and equipment using functional/atomic modeling techniques. It clearly explains the use of models in the ITU-T and ETSI standards, the transport networks and the transport equipment in the definition, implementation and deployment phase.

• Pays particular attention to the SDH and OTN standards using functional/atomic modeling, as used and defined in the ITU-T (International Telecommunication Union) recommendations G.805 and G.809 and the ETSI (European Telecommunications Standards Institute) standards EN 300 417, as opposed to the formal language used in the ANSI (American National Standards Institute) standard T1.105.
• Topics of discussion range from functional modeling high level transport networks to the most detailed device functions, aided by a variety of figures and tables.
• Shows that functional modeling is not restricted to SDH/SONET but that is can be used to describe any transport network, connection-oriented and connectionless, e.g. Ethernet and MPLS networks.
• Written by a leading authority in the area, this is the first book dedicated to the novel approach of using functional modeling to describe SDH/SONET/OTN networks.

This volume will appeal to manufacturers, engineers and all those involved in developing and deploying SDH, SONET, OTN, Ethernet, MPLS technology.  It will be an invaluable resource for postgraduate students on network communications courses and advanced users using functional modeling.

Product Details

ISBN-13:	9780470091234
Publisher:	Wiley
Publication date:	09/23/2005
Pages:	300
Product dimensions:	6.10(w) x 9.10(h) x 0.80(d)

About the Author

Huub van Helvoort has an M.S.c. in Electrotechnical Engineering from the Technical University of Eindhoven in 1977. He has worked at Philips Telecommunication Industries, AT&T, and as System Architect for Lucent technologies working on ISM successors ADM16/1 and Metro ADM (2nd and 3rd generation SDH equipment). In addition he has taught telecommunication technology to post graduate students at the University of Utrecht. The standardisation of VCAT, LCAS and GFP was one of Helvoort's major achievements. He was the representative for Lucent on these subjects in the international standards body ITUT and the regional standards bodies ANSI T1X1.5 and ETSI TM. He was the editor if ITU-T recommendations G.707, G.783, G.7042. He chaired the working group TM1 and TM1-WP3 in ETSI and of the ETSI standard EN 300 417.

Read an Excerpt

SDH/SONET Explained in Functional Models

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By Huub van Helvoort

John Wiley & Sons

Copyright © 2005 John Wiley & Sons, Ltd.
All right reserved.
ISBN: 0-470-09123-1

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Chapter One

Introduction

A telecommunications network is a complex network that can be described in a number of different ways depending on the particular purpose of the description. In this book the optical transport network will be described as a network from the viewpoint of the capability to transfer information. More specifically, the functional and structural architecture of optical transport networks is described independently of the networking technology, for example, distribution, platforms, packaging. The methodology used for this description is commonly referred to as functional modeling and is used in many standards documents to describe the functional architecture of existing and evolving PDH, SDH, OTN, ATM, Ethernet and MPLS networks. The functional model is also used extensively by operators to describe their network and by manufacturers to describe their equipment or devices.

1.1 HISTORY

The development of functional models for use in telecommunication networks was a combined effort of network operators and equipment manufacturers. After an extensive analysis of existing transport network structures, the functional modeling methodology was first introduced in the standards documents of the European Telecommunications Standards Institute (ETSI) around 1995. In the ETSI standards the methodology was used to model the SDH network and its equipment. After the introduction and standardization in ETSI, the International Telecommunications Union - Telecommunication Standardization Sector (ITU-T) also adapted the functional modeling in 1997. Although initially used for the specification of SDH, later it was applied in the specification of other technologies. Currently, work is in progress on modeling Ethernet networks. There is an increased interest in the American National Standards Institute (ANSI) to adopt the functional model methodology in their standards.

1.2 JUSTIFICATION

There were several reasons to start the study and development of a methodology to model a transport network or equipment in a functional way. Some of these reasons were:

Increased complexity. Owing to the natural growth of optical transport networks and equipment, the contained functionality increased as well.

Increased variety. Owing to the growth in complexity, the number of required functions also increased as well as the number of possible combinations of these functions.

Multiple applications. The same transport equipment is labeled differently, e.g. multiplexer, cross-connect, line system, depending on the application in the network topology.

Written requirements. Generally, in a natural language, there have the following disadvantages:

- no common language; requires translation

- voluminous; easy to lose overview

- inconsistent; often dependent on the writer's background

- ambiguous; uses a natural language

- incomplete.

These reasons meant that it became more and more difficult to manage the transport network and equipment. It was almost impossible to guarantee the compatibility and interoperability of equipment based solely on written documentation. Consequently, this created the need for a new language that showed similarities where networks and equipment were similar and differences where they were dissimilar.

Considering the reasons mentioned above, the following requirements were taken as input for the study to establish a new description methodology, i.e. a common language:

It should provide a flexible description of the functional architecture at transport network level that takes into account varying partitioning and layering requirements.

It should identify functional similarities and differences in heterogeneous technology-based layered transport network architecture.

It should be able to produce network element functional models that are traceable to and reflective of network level requirements.

It should establish a rigorous and consistent relationship between transport network functional architecture and management information models.

In addition, the established methodology should have the following characteristics:

it is simple;

it is short;

it is visual;

it contains basic elements;

it provides combination rules;

it supports generic usage;

it has recursive structures;

it is implementation independent;

it is transport level independent;

it has the capability to automate generation and verification.

The result of the study is the definition and standardization of the functional modeling methodology. With a functional model it is possible to present:

Optical Transport Network capabilities, independent of actual deployed equipments.

Transport Equipment capabilities, independent of actual equipment implementation.

The unambiguous specification produced by applying the methodology will provide a unique definition of transport networks and equipment towards:

Optical Transport Network operators;

Optical Transport Equipment and Device manufacturers;

Network Management Systems and Element Management Systems.

1.3 REMARKS ON THE CONCEPT

The analysis and decomposition of existing transmission networks resulted in the definition of the atomic functions that are used in the functional modeling methodology. These atomic functions can be used to compose the functional models of the same existing, legacy and future transmission networks.

This concept is not new. Some other technologies that have used atomic models are listed below.

Hardware (analog). The atomic functions used in this technology are, for example, resistors, capacitors, inductors, diodes, and transistors. These atomic functions can be used to model an analog circuit or network, for example, an amplifier, a cable or even a digital circuit like an OR gate as illustrated in Figure 1.1.

Hardware (digital). The atomic functions utilized in this technology are, for example, AND, NAND, OR, NOR, INVERT and XOR gates. Even though these functions can be represented by the atomic functions of the analog hardware as shown in the previous example, in this technology they would provide too much detail and would make the description of the digital circuit too complex. Thus the gates are in fact compound functions representing the analog hardware atomics. These atomic functions in this technology can again be used to model a digital circuit, for example, a flip-flop, which can be used as a compound function in other models, a microprocessor or a digital transmission function (e.g. a multiplexer, framer). Figure 1.2 shows the atomics and an example circuit.

Software (assembly language). Even the primitives in textual form can be considered as building blocks to describe a particular function. Examples of the textual atomic functions are JUMP, JMPNC, LOAD, STORE, SUB, XOR and NOP instructions. These atomic functions can be used to model a process. Figure 1.3 depicts a simple example. Instructions can be grouped together to form procedures that can be CALLed and RETURNed from when finished; these procedures can be used as compound functions.

Assembly language is however very implementation specific; every vendor has its proprietary set of atomic models and there are no generic assembly language atomic functions.

Software (higher order language). The ITU-T has defined a higher order language to provide a vendor independent programming capability for telecommunication processes: CHILL, the CCITT Higher Level Language (for a description, see ITU-T Rec. Z.200, 1999). Another and more widespread higher order language is the C programming language (Kernighan and Ritchie, 1978). The atomic functions are, for example, FOR, WHILE, IF-THEN-ELSE, CASE, and ASSIGNMENT. Frequently used routines can be collected in a library and used as compound functions. These atomic functions can be used to model a process, for example, the same as the assembly language example above (see Figures 1.3 and 1.4.) Higher order languages are independent of the implementation. There are, however, only a few (micro-) processors that can interpret this higher order language; a translator, or compiler, is used to generate the implementation specific assembly language understood by a particular (micro-) processor.

Process descriptions using state diagrams. The atomic functions in this methodology (e.g. SDL Specification and Description Language, ITU-T Rec. Z.100, 2002) are STATE, INPUT, OUTPUT, TASK and DECISION. The TASK symbol may represent a procedure that can again be specified in SDL and can be considered as a compound function. These atomic functions can be used to describe a process, for example, subscriber signaling, Link Capacity Adjustment Scheme (LCAS, see ITU-T Rec. G.7042, 2004). Hardware and software designers can use these models when implementing a specific process. Figure 1.5 shows an example of the graphical representation: SDL/GR. This is a part of the SDL diagram describing the Source side processing in LCAS (see ITU-T Rec. G.7042, 2004).

SDL also has a textual phrase representation as shown in Figure 1.6: SDL/PR. Tools exist that use this text to generate the graphical representation and and/or generate executable code for testing purposes.

1.4 STANDARDS STRUCTURE

The modeling conventions are described in ETSI EN 300 417-1-1(2001) and the equipment specifications in the remainder of this series (EN 300 417-2-1 to EN 300 417-7-1, EN 300 417-9-1 and EN 300 417-10-1). The methodology is also described by Brown (1996).

After the functional modeling was accepted by ETSI it was also introduced in the recommendations of the ITU-T. The ANSI has not yet adopted the functional modeling methodology to describe SONET networks and equipment (see ANSI T1.105, 2001). Currently there is a whole suite of Recommendations covering the full functionality of network equipment:

The principles of functional modeling are defined in ITU-T Rec. G.805 (2000) for the transport of connection oriented signals and, since the introduction of packet oriented data transport, ITU-T Rec. G.809 (2003) defines the connectionless principles.

Functional modeling conventions and generic equipment functions are defined in ITU-T Rec. G.806 (2004).

The SDH network architecture can be found in ITU-T Rec. G.803 (2000) and the equipment specification in ITU-T Rec. G.783 (2004).

The OTN network architecture can be found in ITU-T Rec. G.872 (2001) and the equipment specification in ITU-T Rec. G.798 (2004).

For PDH only the equipment specification is available in ITU-T Rec. G.705 (2000).

The ATM network architecture is defined in ITU-T Rec. I.326 (1995) and the functional characteristics are described in ITU-T Rec. I.732 (2000).

The Ethernet network architecture can be found in ITU-T Rec. G. 8010 (2004) and the equipment specification in ITU-T Rec. G. 8021 (2004).

The MPLS network architecture can be found in ITU-T Rec. G. 8110 (2005) and the equipment specification in draft ITU-T Rec. G. mplseq (2005).

Network and Network Element management functionality is described in ITU-T Rec. G.7710 (2001) for common equipment, in G.784 (1999) for SDH networks and in G.874 (2001) for OTN equipment. MPLS OAM functionality is defined in ITU-T Rec. Y 1710 (2002).

(Continues...)

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Table of Contents

Preface.

Acknowledgements.

Abbreviations.

1 Introduction.

1.1 History.

1.2 Justification.

1.3 Remarks on the concept.

1.4 Standards structure.

2 Functional modeling.

2.1 Functional architecture of transport networks.

2.2 Functional model requirements.

2.3 Functional model basic structure.

2.4 Functional model detailed structure.2

2.5 Client/server relationship.

2.6 Layer network interworking.

2.7 Linking the functional model and the information model.

2.8 Application of concepts to network topologies and structures.

3 Partitioning and layering.

3.1 Layering concept.

3.2 Partitioning concept.

3.3 Concept applications.9

4 Expansion and reduction.

4.1 Expansion of layer networks.

4.2 General principles of expansion of layers.

4.3 Reduction of detail.

5 Adaptation functions.

5.1 Generic adaptation function.

5.2 Adaptation function examples.

6 Trail termination functions.

6.1 Generic trail termination function.

6.2 Trail termination function examples.

7 Connection functions.

7.1 Generic connection function.

7.2 Connection function example.

7.3 Connection matrix examples.

8 Connection supervision.

8.1 Quality of Service.

8.2 Connection monitoring methods.

8.3 Connection monitoring applications.

9 Protection models.

9.1 Introduction.

9.2 Protection.

10 Compound functional models and their decomposition.

10.1 LCAS disabled VCAT functions.

10.2 LCAS-capable VCAT functions.

10.3 VCAT network model.

10.4 S4–X_c to S4–X_c interworking function.

10.5 VCAT-CCAT interworking network model.

11 Example functional models to exercise.

11.1 Device level functional model.

11.2 Equipment detailed functional model.

11.3 Network element functional model.

11.4 Trail connection model.

11.5 Synchronization network model.

11.6 OTN network element model.

11.7 Data transport model.

11.8 Ethernet layer network model.

11.9 MPLS layer network model.

Glossary.

References.

Index.