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Connection-Oriented Networks:


Harry G. Perros Computer Science Department NC State University


Table of Contents

Preface List of abbreviations 1. Introduction 1.1 Communication networks 1.2 Examples of connections 1.3 Organization of the book 1.4 Standards committees Problems SONET/SDH, GFP, and Data over SONET/SDH 2.1 T1/E1 2.1.1 Fractional T1/E1 2.1.2 Unchannelized framed signal 2.2 SONET/SDH 2.3 The SONET STS-1 frame structure 2.3.1 The section, line, and path overheads 2.3.2 The STS-1 section, line, and path overhead 2.3.3 The STS-1 payload a) Virtual tributaries b) Asynchronous DS3 c) ATM cells d) Packet over SONET (PoS) 2.4 The SONET STS-3 frame structure 2.5 SONET/SDH devices 2.6 Self-healing SONET/SDH rings 2.6.1 Two-fiber unidirectional path switched ring (2F-UPSR) 2.6.2 Two-fiber bidirectional line switched ring (2F-BLSR) 2.6.3 Four-fiber bidirectional line switched ring (4F-BLSR) 2.7 The generic frame protocol (GFP) 2.7.1 The GFP frame structure 2.7.2 GFP client-independent functions 2.7.3 GFP client-dependent functions 2.8 Data over SONET/SDH (DoS) Problems The ATM architecture 3.1 Introduction 3.2 The structure of the header of the ATM cell




3.3 The ATM protocol stack 3.4 The physical layer 3.4.1 The transmission convergence (TC) sublayer 3.4.2 The physical medium-dependent (PMD) sublayer 3.5 The ATM layer 3.6 ATM switch architectures 3.6.1 The shared memory ATM switch architecture 3.6.2 Scheduling algorithms 3.7 The ATM adaptation layer 3.7.1 ATM adaptation Layer 1 (AAL 1) 3.7.2 ATM adaptation Layer 2 (AAL 2) 3.7.3 ATM adaptation Layer 5 (AAL 5) 3.8 Transporting IP Traffic over ATM Problems Appendix: A simulation model of AAL 2 4. Congestion Control in the ATM Network 4.1 Traffic characterization 4.1.1 Standardized traffic descriptors 4.1.2 Empirical models 4.1.3 Probabilistic models 4.2 Quality of service (QoS) parameters 4.3 ATM service categories 4.4 Congestion control 4.5 Preventive congestion control 4.6 Call admission control (CAC) 4.6.1 Equivalent bandwidth 4.6.2 Virtual path connections 4.7 Bandwidth enforcement 4.7.1 The generic cell rate algorithm (GCRA) 4.7.2 Packet discard schemes 4.8 Reactive congestion control 4.8.1 Available bit rate (ABR) service Appendix: Estimating the ATM traffic parameters of an MPEG video source Problems Signaling in ATM networks 5.1 Signaling over the UNI 5.1.1 Connection types 5.1.2 The signaling protocol stack 5.1.3 The signaling ATM adaptation layer (SAAL) 1 5.2 The signaling channel 5.3 ATM addressing 5.4 The format of the signaling message 5.5 The signaling protocol Q.2931



5.5.1 Information elements 5.5.2 Q.2931 messages 5.6 The Private Network-Network Interface (PNNI) Problems 6. The Multi-protocol label switching architecture 6.1 The internet protocol (IP): A primer 6.1.1 The IP header 6.1.1 IP addresses 6.1.3 ARP, RARP, and ICMP 6.1.4 IP version 6 (IPv6) 6.2 The multi-protocol label switching architecture 6.2.1 Label allocation schemes 6.2.2 The next hop label forwarding entry (NHLFE) 6.2.3 Explicit routing 6.2.4 An example of the use of the label stack 6.2.5 Schemes for setting up an LSP 6.3 MPLS over ATM Problems Label distribution protocols 7.1 The label distribution protocol (LDP) 7.1.1 Label spaces, LDP sessions, and hello adjacencies 7.1.2 The LDP PDU format 7.1.3 The LPD messages 7.2 The constrained-based routing label distribution protocol (CR-LDP) 7.2.1 CR-LSP setup procedure 7.2.2 The label request message 7.2.3 The label mapping message 7.2.4 The traffic parameters TLV 7.2.5 Classes of service 7.3 The resource reservation protocol (RSVP) 7.3.1 Reservation styles 7.3.2 Soft state 7.3.3 The RSVP message format 7.3.4 The Path message 7.3.5 The Resv message 7.4 The resource reservation protocol ­ traffic engineering (RSVP­TE) 7.4.1 Service classes and reservation styles 7/4.1 The RSVP-TE new objects 7.4.2 The RSVP-TE Path and Resv messages 7.4.3 RSVP-TE extensions Problems Optical fibers and components 8.1 WDM optical networks




8.2 How light is transmitted through an optical fiber 8.2.1 Multi-mode and single-mode optical fibers 8.2.2 Impairments 8.2.3 Types of fibers 8.3 Components 8.3.1 Lasers 8.3.2 Photo-detectors and optical receivers 8.3.3 Optical amplifiers 8.3.4 The 2x2 coupler 8.3.5 Optical cross connects Problems 9. Wavelength routing optical networks 9.1 Wavelength routing networks 9.1.1 Lightpaths 9.1.2 Traffic grooming 9.2 Protection schemes 9.2.1 Point-to-point links 9.2.2 WDM optical rings 9.2.3 Mesh optical networks 9.3 The ITU-T G.709 standard - The digital wrapper 9.3.1 The optical channel (Och) frame 9.4 Control plane architectures 9.5 GMPLS 9.5.1 Basic features of GMPLS 9.5.2 CR-LDP extensions for GMPLS 9.5.3 RSVP-TE extensions for GMPLS 9.6 The OIF UNI 9.6.1 The UNI abstract messages 9.6.2 LDP extensions for UNI signaling 9.6.3 RSVP extensions for UNI signaling Problems Appendix: A simulation model of a wavelength routing network Optical burst switching 10.1 Optical packet switching 10.2 Optical burst switching 10.2.1 Connection setup schemes 10.2.2 Reservation and release of resources 10.2.3 Scheduling of bursts at an OBS node 10.2.4 Lost bursts 10.2.5 Burst assembly 10.3 The Jumpstart project 10.3.1 Signaling messages 10.3.2 The signaling message structure 10.3.3 Addressing



10.3.4 The routing architecture Problems Appendix: A simulation model of an optical burst switching network 11. Access networks 11.1 The ADSL-based access network 11.1.1 The discrete multi tone (DMT) technique 11.1.2 Bearer channels 11.1.3 The ADSL super frame 11.1.4 Schemes for accessing network service providers 11.2 The cable-based access network 11.2.1 The physical layer 11.2.2 The DOCSIS MAC frame format 11.2.3 The DOCSIS MAC protocol operation 11.2.4 Quality of service 11.3 The ATM passive optical network 11.3.1 Frame structures for downstream and upstream transmission 11.3.2 The PLOAM cell 11.3.3 The divided-slots cells 11.3.4 Churning 11.3.4 Ranging Problems Voice over ATM and MPLS 12.1 Background 12.1.1 Some basic concepts 12.1.2 Channel-associated signaling (CAS) 12.1.3 Signaling System No. 7 (SS7) 12.1.4 Narrowband ISDN (N-ISDN) 12.1.5 Digital subscriber signaling system No. 1 (DSS1) 12.2 Voice over ATM specifications 12.3 Circuit Emulation Services (CES) over ATM 12.4 ATM trunking using AAL 2 for narrowband services 12.5 AAL 2 service specific convergence sublayer (SSCS) for trunking 12.5.1 User functions 12.5.2 The service specific convergence sublayer 12.6 Segmentation and reassembly SSCS for AAL 2 (SEG-SSCS) 12.7 Voice over MPLS (VoMPLS) 12.8 TDM transport over MPLS using AAL 1 12.9 I.366.2 voice trunking format over MPLS Problems


List of standards Index



This book explores a number of connection-oriented packet-switched networks and circuit-switched networks. These networks, though seemingly different, share common networking principles, and in some cases one network is built on another older one. The first connection-oriented network is probably the familiar and ubiquitous telephone network. This is a circuit-switched network, whereby a connection is established between the two parties by allocating a channel on each transmission link along the path. The concept of connection, as used in the telephone system, has been emulated for a long time in computer packet-switched networks. In view of this, such networks are known as connection-oriented packet-switched networks. In this book, we explore two connection-oriented packet-switched networks, namely, ATM networks and Multi-Protocol Label Switched (MPLS) networks. ATM is a legacy network that was developed in the late 1980s and early 1990s. It is used in the backbone to transport IP traffic, in access networks such as ADSL-based networks and passive optical networks, and also in cellular telephony. The MPLS architecture can be seen as an extension of ATM, and it has be used to introduce quality of service in IP networks. Two circuit-switched networks, namely SONET/SDH and Optical WavelengthRouting networks, are also presented in this book. SONET/SDH has been around for along time, whereas optical wavelength routing networks are relatively new. SONET/SDH is the underlying transport network of the telephone system and it is also used in all modern packet-switched networks, such as IP and ATM. In view of this, it is included in the book as part of the necessary background that the reader should have. Wavelength routing networks are also circuit-switched networks since the transmission of data is done using optical circuit-switched connections, known as lightpaths. We also present a new optical networking scheme, which has not as yet been standardized, known as Optical Burst Switching, which can be seen as lying between packet switching and circuit switching.


Finally, the book contains a Chapter on access networks, such as ADSL-based networks, cable modems, and ATM passive optical networks, and a Chapter on voice over ATM and voice over MPLS. The book was written with a view to be used as a text book in a second course on computer networks at the graduate level or senior undergraduate level. Also, it was written for networking engineers out in the field who would like to learn more about connection-oriented packet-switched networks and circuit-switched networks. The book does not deal explicitly with IP networks, and it is not necessary for the reader to have a detailed knowledge of the IP network in order to understand the material presented here. The only pre-requisite for this book is basic knowledge of computer networking principles. The book consists of twelve Chapters, which cover the following topics: · · · · · · · Chapter 1: Introduction Chapter 2: SONET/SDH Chapters 3, 4, 5: ATM networks Chapters 6 and 7: MPLS Chapters 8, 9, and 10: Optical networks Chapter 11: Access networks Chapter 12: Voice over ATM and MPLS.

How current are the specifications? Most of this book was written during 2003 and 2004, and therefore the specifications presented in the book have been frozen in that period of time. Since the networking technology is continuously evolving, the reader is strongly encouraged to browse through the web sites of the standard committees for updates. A note to the students using this book This book grew out of teaching a course on connection-oriented networks and a course on optical networks for the degree of Master of Science in Computer Networks at NC State University. At the beginning of a course, I like to tell my students jokingly that if they


want to get an A they have to read the book five times. If they read it four times, then they will end up with a B, and if they read it three times they will end up with a C, and so on! As the reader can imagine, this statement always gives rise to some lively discussion. However, there is some truth in this statement since the book deals with descriptive material which has been developed over several years by different standards bodies. As a result there are a lot of details to learn and frequently the networking concepts are convoluted and not easy to understand in one or two readings. A good way to test your understanding of a particular networking scheme, is to ask yourself a question, and then try to answer it. If you can answer it immediately without hesitation, then you know it. Otherwise, you need to go back for another reading!! A note to the instructor At the end of each Chapter there are problems. Also, at the end of some of the Chapters there is a simulation project designed to help the reader understand better some of the intricacies of the networks presented in this book. Specifically, the following four simulation projects have been included in the book: · · · · Chapter 3: A simulation model of AAL 2 Chapter 4: Estimating the ATM traffic parameters of an MPEG video source Chapter 9: A simulation model of a wavelength routing network Chapter 10: A simulation model of an optical burst switching network

Each simulation project contains enough information so that a reader who is unfamiliar with discrete-event simulation techniques can easily write the simulation program. More information on basic discrete-event simulation techniques can be found in many simulation books including my e-book entitled Computer Simulation Techniques ­ The Definitive Introduction, which is available free of charge from my web page The solution to the problems and the code and results for the simulation projects can be found in a solution manual, available directly from Wiley's web site. Also, a


power point presentation for each Chapter is available from the same Wiley's web site. If you cannot access this web site, please send me an email ([email protected]).

Harry Perros


10 pages

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