Network Management Principles and Practice - 2nd Edition (2010)_2.pdf

Network
Management
Principles and Practice
Mani Subramanian
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Network Management:
Principles and Practice
By: Manl Subramanian; Tlmothy A. Gonsalves; N. Usha Rani
Publisher: Pearson Education India
Pub. Date: 2010
Print ISBN-10: 81-3172-759-9
Print ISBN-13: 978-8-131-72759-1
e-book ISBN- 10: 81-3174-208-3
e-book ISBN-13: 978-8-131-74208-2
Pages in Print Edition: 726

Table of Contents
Copyright
Endorsements
Preface
About the Author
Plitt J: Background
Oiapt« 1. Data Communications and Networl< ManagementOverview
Section 1.1. Analogy cl Telephone Network Management
Section 1.2. Data (Computer) and Telea>mmunicatlon Network
Section 1.3. Distributed CCmputing Environment
Section 1.4. TCP/IP-Based Networks: Internet and Intranet
Section 1.5. Communication Protocols and Standards
Section 1.6. Networks, Systems, and Services
Section 1.7. case Histories on Network, System, ard Servics Management
Section 1.8. Challenges of IT Managers
Section 1.9. Network Management: Goals, Organization, and Functions
Section 1.10. Network ManagementArchitecture and Organization
Section 1.11. Network Management Perspectives
Section 1.1.2. NMS Platform
Section 1.13. CUrrent Status and Future cl Network Mana{jement
Summary
Exercises
Chapter 2. Review of Information Nelwor1< and Technology
Section 2.1. Network Topology
Section 2.2. Local Area Networks
Section 2.3. Network Node Components
Section 2.4. Wide Area Networks
Section 2.5. Transmission Technology

Section 2.6. Integrated Services: ISDN, Frame Relay, and Broadband
Summary
Exerdses
Part II: SNMP and.-rk 14anagement
Chapter 3. Basic Foundations: Sblndards, Models, and Language
Section 3.1. Network Management Standards
Section 3.2. Network Management Models
Section 3.3. Organization Model
Section 3.4. Information Model
Section 3.5. Communication Model
Section 3.6. Abstract Syntax Notation One: ASN.l
Section 3.7. Encoding Structure
Section 3.8. Maaos
Section 3.9. Functi9nal Model
Summary
Exerdses
Clutpter4. SNI4Pv1 Network Management Organization and information 14odels
Section 4.1. Managed Network: Case Histories and Examples
Section 4.2. History of SNMP Management
Section 4.3. Internet Organizations and Standards
Section 4.4. SNMP Model
Section 4.5. Organization Model
Section 4.6. System Overview
Section 4.7. Information Model
Summary
Exerdses

01apter 5. SNMPvl Net-rk Management: comm..,icatlonand F..,ctional Models
Section 5.1. SNMP Communication Model
Section 5.2 Fund:ionall'tldel
Summary
EXercises
chapter 6. 5NMP Management: SNMPY2
5ectlon 6.1. MajorChanges in SNMPv2
5ectlon 6.2. SN.
MPv2 System Architecture
Section 6.3. SNMPv2 Struci)Jre of Management Information
Section 6.4. SNMv2 Management Information Base
Section 6.5. SNMPv2 Prot:oa>l
5ectlon 6.6. COmpatibility with SNMPv1
Summary
EXercises
01apter 7. 5NMP Management: SNMPvl
Section 7.1. SNMPv3 Key Features
Section 7.2. SNMPv3 Documentation Architecture
Section 7.3. Architecture
5ectlon 7.4. SNMPv3 Applications
5ectlon 7.5. SNMPv3 Management Information Base
Section 7.6. Security
5ectlon 7.7. SNMPv3 User-Based Security Model
Section 7.8, Acai!ss Control
Summary
Exercises
01apter 8. 5NMP "!1111agoment: RMON

section 8.1. What is Remote Monitoring?
section 8.2. RMON SMI and MIB
section 8.3. RMON1
section 8.4. RMON2
section 8.5. An-1 Remote Monitoring
section 8.6. A Case Sttdy on Internet TralfiC USing RMON
Results
Summary
Exercises
Chllpter t . Network Manogement TooII, s,.tom., and Engineering
section 9.1. System Utilities for Management
section 9.2. Network Statistics Measurement Systems
section 9.3. MIBEngineering
section 9.4. NMS Design
section 9.5. Network Management Systems
Summary
Exercises
Part W: TMN and Appllcatlortt Management
section 10.1. Wl'rf n-1N?
section 10.2. Operations Systems
section 10.3. n-1N Conce~Xual Model
Section 10.4. n-1N Standards
Section 10.5. n-1N Architecture
section 10.6. n-1N Management Service Architecture
section 10.7. n-1N Integrated View

Sedlon 10.8. 'TMN Implementation
Summary
Exercises
Chapter 11. Networlc ManagementAppllcatloni
Sedlon lLl. Configuration Management
Sedlon 11.2. Fault Management
Sedlon 11.3. Performance Management
Sedlon 11.4. Event Correlation Techniques
Sedlon 11.5. SeOJrity Management
Sedlon 11.6. Accounting Management
Section 11.7. Re~X~rt Management
Sedlon 11.8. Policy-Based Management
Sedlon 11.9. Service Level Management
Summary
Exercises
PartIV: Broadband Networl< Management
Chapter 12. Broadband NetworkManagement: WAN
Sedlon 12.1. Broadtend Network and Servk:es
Section 12.2. A'TM Technology
Section 12.3. A'TM Network Management
Section 12.4. MPLS Network Technology
Sedlon U.S. MPLS OAM Management
Sedlon U.6. Optical and MAN Feeder Networks
Summary
Exercises
Chapter 13. Broadband Networj< Management Wired and Optical AcC<!IS Networks

section 13.1. Broadband Access Network
section 13.2. Broadband Access Technology
section 13.3. cable Modem Techrology
section 13.4. cable lv.:CI!SS Network Management
section 13.5. DOCSIS Standards
section 13.6. DSL kress Netwai<
Section 13.7. Asymmetric Dgtal Subscriber Une
Section 13.B. ADSL Management
Section 13.9. ADSL2, ADSL2+, and VDSL2
section 13.10. Passive O~ical Network
section 13.11. PON Management
Summary
Exercises
Section 14.1. Basic Prindlies
section 14.2. Fixed Broadband Wireless Access Networks
section 14.3. Mot:XIe Wireless Networks
section 14.4. Satellite Networks
Summary
Exercises
section 15.1. Home Networking Technologies
section 15.2. Wired Home Distribution Network
section 15.3. Ethernet: Management
section 15.4. Wireless Home Distribution Networks
section 15.5. IEEE B02.11/WIFI Network
section 15.6. IEEE 802.11 Network Management

Sunrnary
EXercises
Chaptar 16. AdVI-d MlnlgiiiMntTopics
Section 16.1. Introduction
section 16.2. Early Web-Based Development
Section 16.3. CORBA·Based NM Technology
Section 16.4. XML·Based NM Technology
Section 16.5. COmparison of Management Technologies
section 16.6. Recent NM·Related Standards
Summary
Exercise
Aj>pendbt A. 051 Networlc ond System M1n1goment
Section A.l. OSI Management St!ndards
Section A.2. System Overview
Section A.3. Organization Model
section A.4. Information Model
Section A.S. COmmunication Model
Section A.6. Application Functions Management
Sunrnary
Aj>pendbt e. ProjeCt 91ggostlont
Section 8.1. Project Struct~.re and Evaluation
Section 8.2. Projects
Aj>pendl~ C. LaborlltofY Tuto~el
5ectlon C.l. Network Basic Tools Lab

Section C.2. SNMP Tools lab
Section C.3. SNI'F AJ)Pications
Appendlx D.Sp•ud Spec:tnlm Tedlnology: OFOM
5edion 0.1. FourierTransformation
Trademarks
Acronyms
Glossary
References
Index

Copyright
Copyright C 2010 Manl Subramanian
This edilion is published by arrongemeot with P~'MSOn Education, lnc. aodDorling Kindersley Publishing lnc.
This book is sold subject to the condition thatit shall not, by way oftrade or otherwise, be lent, resold hired out, or
othimvise circulated without the publisher's prior written consent in any form ofbinding or cover other than that in
which it is pubtisbed and withoul a similar condition including litis condition being imposed on the subsequent
purchaser and without limiting tbe rights under copyright reserved above, no pan of this publication may be
reproduced, stored in or introduced into a retrieval system, or transmitted in any form or by BOY means (eleoironic,
mechanlcal, pho10copying, recording or otherwise), wilhoul the prior written permission of both the copyright
owner and tbe aboVC>-mentioned publisher ofthis book.
First Impression
Publlshed by Dorllng Kindersley (lndia) Pvt Ltd, licensees ofPearson Education in South Asia.
Head Office: 7th Floor, Knowledge Boulevard, A-8(A). Sector-62, Noidn 201 309, lndia.
Registered Office: 14 Local Shopping Centre, Panchsheel Park, New Delhi II 0 017, India.
Typeset in 10.5/125Times New Roman by Sigllia Business Process, Chennai.
Printed in India
Dedication
In loving memory ofAppa Mahadevan Amma Kalyani
Affectionatelydedicated to R1rth,.Rnvi, and Mcern Subramanian fur sustained support and persistent
patience
With deep appreciation to Stimulating Students Who led me to leoro by teaching

Endorsements
•t have ~n using the first edition since 21Xl3 as core management principles-and practical topics discussed therein made It
an e>ctremely useful reference even for practitioners. I am happy to note that the second edition Is making the contents of
the·te>Ctbook even more appli!<!ble In the current technoi C~~Ical context by Incorporating management of Optical & MPLS
networks widely deployed In the telecommunications network. discussing broadband wireless ne~orks management that
are now ubiquitous and the evolution of standards and t.echnoiOI!ies governing the actual implementation ofthe NMS Itself.
The addition of discussions around Cygnet NMS to Illustrate the NMS architecture concepts and Implementation
considerations are quite useful. 1 am sure·the· book will serve· the needs of both students In academics as well as the
telecom and networking professionals.•
-Nagarajan, Sankor
Head, NMS R&D Services, Tech Mahindra, Chennai, India
"Many congrnl ulations! It is a wonderful book wiU1 lots ofminute details on Network Management
ram sure it will be a ready handbook for the student/professional communities.
My sincere thanks for your time and effortin bringing out the second edition ofthe textbook."
- Seetharaman, V.
Head, ITMC & Cable NOC, Bharti Airtel Limited, Chennni, India
"Prolessor Subramanian has a remarkable ability to set oomplex network engineering and associated
network maJiagement problems in context with well-written explanations and real-work! examples
1hat deal with 1he varied demand~ placed on converging telecommunications networks and the
design and operation ofthe underpinning management systems and protocols.
This book will be extremely useful resource for graduate· and postgraduate students on CSIEE
courses including those studying in their first year ofPhD in Telecommunications Engineering, as it
provides a fantastic coverage ofa wide ra11ge of fundamental network management issues. I fur one
will be using it for my graduat.e students."
-Parr, Gerrard
School of Computing and Information Engineering, University of Ulster, Coleraine campus,
Londonderry, Ireland
"Dr. Subramanian's Network Management Principles and Practice provides the most thorough
treatment of network management. io date. There is no fluff in this book. rt ·is for tl!C serious,
interesr.ed reader. rt proceeds from the ground up. startlng with common network managemeru
protocols and coot!nuing to cover telecommunications management and broadband network
management, focusing o n WANs, optical networks, wireless networks, and home networks. Each
chapter builds nicely upon previous chapters so that there is a logical delivery of infom1ation.
Chapter 9, "Network Management Tools, Systems, a.nd Engineering" is a very useful, practical
chapter. rt provides Lhe reader with the know-how to perfOrm hands-on network management with
various management tools. Chapter l0 covers the classic model of tl!C Telecommunications
Management Network, indispensoble for understanding network management. C hapter II covers
other important aspects of network management, including fimll management, performance
management, security management, policy-based management, and service level management.
Further, C hapter II includes a section on event correlation methods, typically notfound in book~ on
network management, and this is refreshing. These two chapters provide a soUd foundation for
understanding the management ofWANs, optical networks, wireless networks, and home networks
in lhe subsequent chapters. Chapter 16 covers forward-looking topics in network management,

including web-based enterplise management and XML-based management approaches. Titere are
appendices on Project Suggestions and Laboratory Tutorials that render the book quite well·suitcd
fur use in a course on network management. All in all, Dr. Subramanian's book provides a serious,
first-rule trealment ofthe subject."
-Lundy Lewis
Department Chair & Professor. Southern New Hampshire University. Manchester, USA
"This book fills a loog-siandiog need. While there is an abundance of courses and textbooks that
deal with typical topics in networking, there is a lack of such books for Network Management.
Often, concepts and technologies related to Network Management are relegated to the last few
chapters. This book brings out the fuct that there is a wealth ofdetail in this area, which is important
fur practitiooers as well as students.
This book give·s comprehensive details of aU aspects ofnetwork management, in different types of
contemporary networks. Reading it would save .practitioners considerable time and effort, which
they might otherwise put into reading diverse onllne sources. This book also provides the syllabus
structure required fur a fitll-fledged course.on Networking Management. It would be appropriate for
students at the wtdergraduate as well as postgraduate levels."
-Sridhar lyer
Indian institute ofTechnology Bombay. Mumba India
"It is a very comprehensive book on Network Management Systems addressing the needs of
academia, industry both.R&D and Operations. Coming from a person who has worked on all these
functions in telecoms, the good thing about the second edition is the coverage of various
technologies like Wireless, broadband, home networking nod the challenges these technologies pose
to ihe NMS."
-Chalapathi Rao
Vice President & Head Global Delivery, Tata Communications Transformation Services Ltd.,
Chenoa~ Iodin
"Mani Subramanian's book has been of great help in our undergraduate Network Management
course.
Tite book provides both a top-down view on Network Management approaches and a boHom-up
view of the managemeru information available in almost any kind of network technology and
environments. ln particular, it offers quick and visna Iorientatio.n in the jungle of Mills available in
all kinds ofequipment.
The new edition kept the spiril oft·he first edition, but enhanced it significanllywith new and helpful
visualisalions, examples and contempomry management scenarios.
The presentation is interspersed with the author's long-standing experience with Network
Management and its tools, which beIps lhe reader to gain a deC~> understanding of the reasoning
'behind NetworkManagement models, protocols, services nod tools."
- Markus Fiedler
Blekinge lnstituteofTechnology, Karlskrooa, Sweden
"This edition takes offfrom the previous one with a renewed perspective on network management,
incorporating relevant developments over the pas! decade. The ueatment ofthe topic beginning with

a problem statement sels the scene for a detalled coverage on network management systems and
their asscx:iated protcx:ols. Mapping of TMN and eTOM gives a we.U-rouoded view of both the
technical and business process aspects of network management for the telecom operator. Real
industry examples provide. the much-needed meeting ground of theory and practical
implementations. Or. Subramanian's experience with the implemeolalion of network management
in major telcos lends authenticity to the treatment of this interesting sU:bjecL To summarize, the
book would be va.luable to students and professiooa.ls alike."
-Aiyappao Pillai
Head, CNMS, Tata CommunicailinsLtd., Mumbai, lodia

Preface
Network-centric World 1
1nd Role of Network Management
The world in the information era has become network-centric. Daily life, both personal and institutional, is
network-centric. Century-old telephone technology has brought us today to llte converged telccommunicatiom and
data communications technology eni. We are linke-d to and i:nterfitce with the globally ''flat-world" viae-lifeline.
The information era has buib a world of information networks and systems that we need to operate, administer,
maiotain, and provision onan on-going basis. That is our cballenge.
Areas of management ofnetworks, systems, and appiJcations in data and telecommunication services are not only
the responsibility oftelecommunications and networking industries and standards bodies but also of the academic
world. Snadents gradualing from technical Colleges nod universities are eltpected to be prepared to use a network
and also to design and to manage one. The eltisting procedure to design and.test some key networks is heuristic.
Personnel with e1tperience, nod sometimes without, design networks and test ·them in live situations. A corporation
hardly functions today without the deployment of locaJ area. networks (LANs) in their networking environment.
The majority of homes in developed 118tions have a home network distributing voice, video, and data information.
With the prolifernLing use ofthe internet and Web technology, Lhe subject ofnetworking nod network managemenl
has become part of the academic curriculum. This tClttbook. introduced ten years ago, has been part of this
evolution. This newedition brings newtechnologies and services to undergraduateand graduate classrooms in the
broad arena ofwhat is known as network management.
Justificntioo for a Textbook on Network Management
Over a decade ago when I sLnrted teaching a course on network management, there was a need for a textbook that
satisfied quarter/semester requirements. The adoption ofthis book bycoUeges and universities across the world has
partially fiU.ed lltal void. Just as networking education has been brought from the graduate to the undergraduate
level. thiseditim ofthe textbook has been upgraded so that early parts ofthe book can be used at the junior and the
senior undergraduate level and tarter parts at lhe graduate level. It alJJO addresses lhe audience of self.learners who
want to get into or gain knowledge ofnetwork management.
Once again, a note abotrt the title of this book: As noied in the earlier edition, the title does not truly reflect Lhe
contents of the book because we want to keep it succinct. The book covers management principles, practices, and
teclmologies fur managing networks. systems, appllcations, and services. The book is designed to be self-
conLnined, so that the student does not have to traverse in ond out ofthis book' s domain. An atte.mpt has been made
to strike the right balance between theoretical background and practical aspects of networking. The treatment of
practical aspects includes some real-world examples and "war stories." lf"a picture is worth a thousand words,"
this book oomains. about a million. Just as a programming course requires hands-o.n programming exercises, so
does a. network management course. So we have added laboratocy tutorials to the nppeodix, which supplement
classroom teaching.
A major addition to the book is the eXpanded treatment ofbroadbaod network management. It covers "triple play"
services of voice, video, and daLn communications. It spiUlS the netwOrk over the segments ofwide area network
(WAN), access networks to home, and home distribution networks includingLANs. Multimedia communications
is covered from the aspects ofwired transmission media ofcable. digital subscriber line, and optical fiber as well
as tilted and mobile wireless.
This book exposes the student tocurrentnetwork management technology. At the completion ofa course using this
book, the student could either enter the industry with adequate networking knowledge or graduate scboolto pursue
further research and specialization.

About t.be Contents
The book is divided into four part$. Part I deals with baekground material on networking and net,vorking
technologies. Pan naddresses network management archirecltlre$ and protocols. l11e fOcus is on SNMP and lP
network management. Pan ill extends network management to tbe management of telecommunications, which
includes networks, systems, opemHJDs and business services, and management applicaHJDs. The lasi, and final,
Pan IV concludes with the management ofbroadband networks and the latest trends in management technology.
Pan Lconsists ofChapters I and 2. Chapter I presents an overview of networking nod network management.lt is
intended not only as a. background and top-down information, but also as a motivation for the student. Chapter 2
reviews networking technology with a slant on management aspects. The course, fur which this textbook is
intended, assumes thlll the student bas basic knowle<lge of data communications and networking. However, we
review them briefly in Chapters I and 2. lt is extromely difficult to cover much more than the basics of protocols,
algoridmts, and procedures of transport protocol layers 2, 3, and 4, as well as basic ruditne.nts of components of
LAN and WAN networks in such a cour.se. Not much techno logy can be covere<l, and network rnanagement
depends strongly on managing oerwork components that are based on an ever-evolving technology, hence the
presence ofChapter 2. It can be either skipped or covered in parts by ihe·instructor. Relevantsections could also be
used when dealing with subjects in Pans 11, IlL nod rv. However, it would be useful as reference material for non-
classroom learners who want an introduction to networking and network management.
Chapters 3 dtmugh 9 fonn Pan 11. Basic foundations ot models that are needed to build various network
management architectures and protoools are covere<l. OSI-b115ed network management is rarely used. but has some
strong fundamental concepts. For completeness of the subject, it is included in Appendix A. SNMP-based
protocols that manage TCP/lP networks are covered in Chapters 4 through 8. Chapters 4 and 5 are devoted to
learning the concepts and use of SNMP (version I) in network management. Chapters 6 and 7 deal with the
additional specifications defined in versioos 2 and 3. Chapter 8 extends network management using remote
monitoring capabilities. Chapter 9 discusses networking and network management tools. The architecture and
features ofsome ofthe widely used network and systemmanagement systems are also covered.
Network management is more than just managing the network infra.;tructure. Pan Ill addre$ses this trom the
service, business, and applications points of view. Chapter 10 extends the management area to cover broader
aspects of networ.k management &om managing oetwor.k elements and networks to service and business
management as addressed in Telecommunications Management Network (TMN) standards. The knowledge
acquired onmana&rement tools and systems, as weU as on principles in Panll, .
is applied to practical applications i.n
managing iilult. configuration, performance, security, and acoounti.ng, which fOrms the contents ofChapter II.
The demarcation of telecommunications and data communications is becoming increasingly fuzzy in broadband
communications. ln Pan IV, tbe broadband network is segmented into WAN, access network, and home
distribution network. Cbapter 1
2 deals with WAN.lP teclmology bas been extensively dealt with in Parts f and IT.
The management of ATM network, MPLS network, and optical SONET/SDHIDWDM network management is
covered in Chapter 12. Chapter 13 addresses wired broadband access networks in bringing services .from core
WAN to home. Management of cable, DSL. and PON are the three technologies Lhat we cover. Pixed and mobile
wireless access network mnoogement form the subject matter ofChapter 14. Having brought voice, video, and data
ofbroadband service to home, it needs to be distributed inside customer premises and managed. This is the topic of
discussion In ChapUT 15.
The impact of emerging technologies in a We!>-based and object-oriented management system is me future of
management techno logy, which is addressed in Chapter 16.
Suggestions furCourse Syllabus
Pans I and IT along with tbe Laboratory Tutorials in Appendix C form a unit for undergraduate courses. Pans ID
and IV are suitable for gmduate-level oourses with senior-level students admitted with Lhe consent ofthe instructor.

The complete contents of the book are more than can be covered in a quarler or !!Yeo a semes1er course. The
instructor may do a "mi.x and match" between chapters to sui1· fecal needs if SNMP basics and some of the
broadband network management are to be covered in one seme,~ter. Independent of the choice, a project to
aocompaoy the course is recommended, and suggestions are given in Appendix B.
For a dedicated course on network management, U1ere are seve~:~~ I choices. If the focus is on SNMP managemeni,
then Chapters 6 through 8 covering SNMPv2. SNMPv3, and RMON, respectively, can be used. That can be
followed with network management tools and systems (Chapter 9) and applications (Chapter II).
Iftelecommunications is·emphasizcd (this is more likely in computer engineering sthools), !hen it would be good
to include Telecommunications MlUlagement Network (ChaptQr I0).
Ifbroadband services are taught at the schoo~ then Part IV (Chapters 12- 16) could be included.
Finally, ifthe school has a research program on network management, il is suggested that in addition to the special
areas ofinterest, management applicutions in Chapter .II be dealt with in depth. ln addilien, adequate treatment of
Advanced Management Topics (Cbapter 16) is strongly suggested.
To the JnMructor
This 1
extbook is designed as a dual-level book. It can be used for undergraduate courses at the junior or the senior
level or for graduate-level courses. H assumes that the student bas t.akeo a prerequisite course in either data or
telecommunication network or has equivale.nt knowledge. Howeve.r, the book does review networking from a
management focus prior to de-.tling direc1ly with the main subject ofnetwork management.
With the prolific growth of networking, nel:vork management is expected to become part of the academic
curriculum, and. this book will be useftl fur both Computer Science and Electrical and Computer Engineering
schools that specialize in networking.
Online Supplements: Solutions to exercises are available to instructors from the Pearson representative. Visual aids
in the format of PowerPoint sfides fur instructors and students are available to all from the Pearson website that
would facilitate leachiQg and note-taking in 1hc class.
The book could also be used as a reference material ifyou are leaching a Continuing Education course on network
management. lloe PowerPoint slides will come in handy as classroom aids. l have found that students like to take
borne koowledge in the !Orm of a book in addition to the srudetn manua.l. The author welcomes suggestions and
material to be added and may be reached at manims@ieee.org.
To the Student
Although the book is written as a textbook to be adopted for n course, additimal information is provkled in the
book !bat would serve as a reference book for students after graduation. For example, basic information is provided
along with references to serve as a springboard to access additional in-depth details on any specialized
management topic.
The book is also geared toward self-motivated. engineers in the industry who are eager to learn network
management. lfthe engineer bas access to network resources, many ofthe bands-on exercises could be practiced.
At the minimum. it would provide enough tools and knowledge for tbe frustrated worker when he or she eaMoi
access the network resources and does not know why.
Grateiitl Acknowledgements

Tbe major impetus for tbe contents ofthis book bas come from students overtbe course offerings since 1996. lt bas
been reviewod a.t various levels and LO various depths by rnany students.
My thanks flow profusely to Profussor Timothy Gonsalves and Dr. Usha Rnni for making major contributions to
Chapters 9 and 16, respectively. We hove shared together teaching tbe Network Management course at Indian
Institute of Technology Madms, I thank Professor Gemrd Paar for moth•ating me to come out with a second
edition; and it is unfortunate that he coukl not participate as a contributing author due to other commitmen.ts. I owe
gratitude to several persons at NMSWorks who have helped in various ways in the preparation ofthe lllJllluscript
My special thanks to Binu Raghavan for generat.ing topological views of CygNet NMS that is customized for the
textbook presentation, to Madangopal and Adithyan for SOH exercises, and to Santosh Chaudbari for help with
network load statistics figures.
Many reviewers· comments and suggestions have contributed to the richnessofthe contents ofthe first edition that
.form U1e basis of this edition. 1 owe special gtutitude to Lundy Lewis, who bas made numerous and specific
suggestions for improvement in the ftrSt edition. TI1e results of .interviews described in Chapter I generated
positive feedback from reviewers and students; and I thank the fullowing at Georgia Tech .
fur consenting to be
interviewed: Cas D'Angelo, Ron Hutchln.s, Dave Miller, John Mize, and Jobn Mullin. Some of the case histories
were provkled by Rob Beverly, Ron Hutchins, and Dave Mlllcr. Brandon Rhodes and Oleg Kolesnikov provided
someinteresting practicalexercises to be included in the book.
My thanks go to Sojan Jose, Commissioning Editor, M. E. Sethurajan, Senior Production Editor, and Je1mifer
Samuel Sargunar, Associate Production Editor, of Pearson Education for their ever-willing cooperation in
successfully seeing this second edition through to complet.ion.
1 am indebted to the lndian Institute ofTe:chnology Madms fur providing time off fur me to corr~e out with the
second edition. r also want to tbank Professors Ashok Jhunjhunwala, Timothy Gonsalves, and Bhaskar
Ramamurthy of TeNeT Group for providing me with an environment to fulfill my desire of the long-needed
upgrade oftbe book.
My wife, Ruth, continued her contribming role to the book by inputting revisions, ncling as the local copy edi1or,
and beingproduction manager ofmanuscripts. Thank you again, Ruth.

About The Author
Mani Subramanian
Mani Subramanian is a Chair Professor at Indian {nstitute of Technology Madras where he teaches courses on
Network Management and Broadband Communication Systems. Be is also the Director ofNMSWorks Software
Solutions Private Ltd., Chennai. India. He initiated 11 ·network 1011nagement program at Georgia Institute of
Technology in 1996, wJ1ere he is presently on tile Adjunct Faculty. The first edition ofhis book, published in 2000,
is currently adopred ns a te:..tbook in over fifteen countries and translated into Chinese for Higher Education in
Chinn. For over 45 years, he has led research and development at several IT corporations including ~II
Laboratories, has been in the faculty at three tmivcrs.
ities, and bas founded network management companies in the
broadband arena. As an elected Director of the Network Management Forum, be was responsible for the fl'.st
release ofOSI NM specifications. Dr Subramanian received h.is Ph.D. fi:om Purdue University.

Part I: Background
Chapter I presents an overview of tel.ecommunicaiions, dala communlCIItions, and network
management. It is a broad review ofnetworking and network mamigement. It stru1s with an anabgy
of lite telephone network. Telephone network almost always works, and there are reasons tOr its
achieving quality and reliability. You will learn lite relationship between data communications and
telecommunications and b.ow the d.istinction between the two is slowly disappearing. The influence
of desktop computing sod distrlbuted computing environment based on client-server architecture
.bas revolutionized computer communlCIItion. The lnier.
net is a worldwide fabric and you willleam
to appreciate bow infOrmation travels across it around the globe. Basics ofcommunication protocols
and architecture are presenred along with various standard~. Select equivalent applications are used
as illustrations comparingthe Internet and OSI protocols.
Components ofnetwork llUIJl8gemeot are described and complemented by interviews witll network
managers, whose experiences emphasize the need .
fur network managemem and a network
operations renter. Network management is more than just managing networks. Network
management l$ presented from lite perspectives ofservice management, operatiorts support systems,
and business management. The platfOrm !Or a network management system is discussed based on
client-server architecture. Chapter I concludes with a note onfuture trends in network management
technology.
Chapter 2 !Oc:uses on netvork techoology. You may skip this chapter ifyou are familiar with the
practical aspects ofnetworking. Ifyou are knowledgeable on principles ofdata communication, this
chapter. will help you appreciate lite 1eclloological aspects of i1. You will learn how various
topologies are implemented in LAN and WAN networks. Basics of Ethernet, Token Ring, and
FOOl networks are described from a pmctical point ofview. Ofll"oe.se, Elhernet is the most widely
deployed LAN today. LAN evolution from basic Ethernet to Gigabit Ethernet. with half· and full·
duplex configurations is presented. Switched Ethernet adds capability to expand lite bandwidth and
the flexibility of LAN. Virtual LAN is implemented using a switched Ellternet bub accomplishing
flexibility in administmtion of workstations across mukiple LANs. You will learn the various
network components--hubs, bridges, routers, gateways, and protocol converters--that need to be
managed. A brief review of wide area networking and transmission technology is also presented.
Broadband technology is briefly described in Litis chapter. but a dem.iled discussion of it will be
done in Pan rv while addressing the managemem ofbroadband networks and services.

1. Data Communications and Network Management Overview
Objccth'es
Teleoommunications overview
Data oom.municalionsoverview
Evolution ofconverged networks
Desktop processors and LAN technology
Client-Server architec1ure in networking
Internet and intmnet
Nerwork communication protocols
OST and lntemet standards
Broadband networks and services
Need for network management and NMS
Operat·ions, Administmtion, Ma.inlenance, and Provisioning
Network management architecture and organization
Concep1 ofNetwork Operations Center
Perspeclivc.s ofnetwork managemenl
• Network ma11agemeli/ :r."-">tem
Look-ahead ofnetwork management technology
This chapter demonstrates the lleCessity of network system and service management in providing infurmation
technology (IT) services. The challenges thai IT managers face are pl:esented to motivate !he studenl to get excited
about n.etwork management. We start with the ltistory of computer oommunicatiotL walk you through some real-
world case histories, and then present an overview ofvarious aspecls ofnetwork management.
The telephone system is known to be very reliable and dependable, One can make a lelepbone call from anywhere
to anywhere at any time oft.be day and be reasonably sure that the connection will be made and the quality of
conneclion will be good. This is partly due lo the efficient management of the telephone network. Secrion 1.1
introduces the concept of managemem for the success of telephone nelwork by using Operation Support Systems
(OSSs).
Computer communication initially used the 'telephone networlt to carry digital data. There was a clear demarcation
between '!be tmditionalteleconummication network and computer communication network. The evolution ofearly
computer communication networks is dealtwith in Section 1.2.
Computer communicalion technology radically changed with the advent of desktop computing power and
distributed computing environments (DCEs) using local area netvorks (LAN) as described in Sec!ion 1.3. Global
communicalion using Internet became. a reality with the introduction of TCP/IP-based networks. Section 1.4
describes Internet and inlnlnel followed by a dlscussion in Section 1.5 on the importance of communication
pro!oonls and standards.
The nexi phase in the evolution ofIT was !he introduerion of broadband services. Voice, video, and data oould he
delivered on the same medium to homes. lltis has revolutionized the access network to horne and the distribution
network at customer premises. 11 has also iniliated impt"Ovemenl in the core wide area network (WAN). Section 1.6
addresses these issues.
Nelworking is full of "war stories" as experienced by IT managers. Sec!ions I.7 and 1.8 presenl case histories
experienced by IT managers and the challenges !hey face in today's computer and telecommunicalion

enviro.mnent. Interviews with them emphasize the impor11loce of network and system management tools. Section
1.9 describes network management that comprises operations, administration, maimenan.ce, aod provisioning.
Three groups perform these functions: Engineering, Operations, and Installation aod Maintenance (l&M). Section
I. 10 focuses on Network Management System (NMS) aod relationships between its various components. Besides
managing network components, application system resources also need to be managed. TWs is the subject of
Section 1.1 I.
Network. managemem tecbnology is still in an evolutionary mode as network and software technologies advance.
Section 1.12 bricily add.resses NMS platforms baSed on Microsoft. Windows and UNIX operating system. The
future direction~ of network management technology form the content ofSection L 13. As with all chapters in the
book. a sun:unary section and exercises conclude this chapter.
1.1. Analogy ofTclcphone Network Management
The need.for data or computer communication network management is best illustrated.by an analogy oftelephone
·network management. Tbe high degree of reliability of the telephone network is evidenced by the following
illustration. We can pick up a telephone, call anybody, anytime. anywhere in tl!e world, aod be·almost sure to be
connected to the destination. It is reliable and dependable; and the quality ru1d speed ofconnection are good. It is
reliable because it almost a!ways provides se.rvice of voice communication tbat we expect of it. It is dependable
because we can be fairly sure that il works when we need il. especially in an e.mergency situation. such as 911 calls
in 'the USA or military defense situations. The quality ofservice is generally good; and we can have a conversation
across !he world with the same clarity that we bave when we call our neighbor.
The pre~nt-dny telephone network is referred to as Public-Switched Telephone Network (PSTN). aod is probably
the best example of traffic engineering providing guaranteed Quality of Service. The reason .for such reliability,
dependability, and quality Is more than careful planning. design. aod implementation of a good telephone network
using good and reliable components. 'Tlte key is management aod operation of the oetwor.k. Much of the
management of the network is so well automated that it becomes part of the operation. Let us first look at the
telephone network architecture and then at some oflhe operations support systems tbat manage it. In the 1970s the
telecommunications industJy switched to digital services, which followed much the same pattern as voice services
and conceived a vision of end-to-end circuil-switc.hed services. known as the Broadband Integrated Services
DigitalNetwork(B-ISON).B-ISON is now being replaced by Internet and Broadband Service.
The ar.chitecntre ofa telephone network is hierarchical as shown in Figure 1.1[AT&T 1977]. There are five levels
of network switches and three types of trunks that connect these switches. A trunk is a logical link between two
switches and may traverse one or more physical links. The end office (Class 5), wh.ich is lowest in the hierarchy, ls
the local switching office. The customer's telephone or Private Branch Exchange (PBX) Is connected to the end
office via a dedicated link called " loop." The other fuur higher levels of switches (Class 4 through Class I) are
tandem or toll switches carrying toll (long-<listance) calls. Because of the advance in switching technology and
economy oftransmission, ctasse·s I through 4 have been merged into a single class rercrred to as Class 4. A direct
trunk connects two end offices, a toll-connecting trunk connects an end office to any toll office, and 11.toll(internal)
trunk connects any two toll offices.
Figure 1.1.Td•t•hou• Notwork Mod<l

End Cllfoee EndOfflc<>
Class5 SwiiCh Class 5 Switch
• t
6> 0
Voire Voice
To Oliler
Regional Centers
Sedional Cenlers
Primal)' Centers
ToUCenteB
EndOff.a;s
Primary Centers
Toft Centers
EndOiftee$
Cia$$ 4 Toll Polnls
EndOtr,._
Logond;
.... I..OQP
- Olrecl Trunk
- - Toii.COnnoc~ng Trunk
- Toii Trunk
From the lo<:al Class 5 office to the called party's Class 5 office, there are multiple routes. A circuit connection is
set. up either directly using a local trunk or via higher-level switches and routers. Primary and secondary routes are
alrea~y programmed into the switc.h. lftbe primary route Is broken or facilities over the primary route are filled to
capacity, an alternate route is automatically assigned. For e.xrunple, on Mother's Day, which is the busiest
telephone-troffic day ofthe year in theUnited States, a call io tbe neighboring town could trove! clear across the
country and. back iftb.at's the route where adequate bandwidth is available. Let us remember that there is a 3-hour
time difference·between the two coasts, and traffic in the West Coast starts 3 hours laterlhan the East Coast.
To ensure tbe quality of service in a telephone network, operations support systems are implemented. They
constantly monitor the various parometerll oftbe network. Forexa.mpte, to ensure that there is adequate band,vidLb
to carry the· troffic over the facilities, a troffic measurement system constantly measures iroffic over switch
appearances. The results are analyzed for facility-planning purposes. They also provide real-time input to a NMS
when there is excessive blocking (traffic over the capacity oft.he trunk group) in any link.
The qualily of the call, measured in terms of signal-t~no ise (SIN) rotio, is measured regularly by a trunk
maintenance. system. This system accesses all the trunks in an office during the night· and does a loo~back test to
the far end. lbe results are analyz.ed in the morning and corrective actions taken. For example, ifthe SIN ral.io ofa
trunk is below the ac.ceplaoce level, the trunk is nimovcd from service before the· customer experiel.lCes poor
performance.

Par a given region, there is a network operntions cemer (NOC) where the global s1atus of!he network is mo.nitored.
Traffic patterns are constant.ly observed and corrective operations are taken, ifneeded, in real time. The NOC is t:he
nerve center oftelephone network operations.
lt is worlh noting !hat the telephone .network is lll1IJI8ged from the users' perspective, and not nom that of the
system or the service provider, even though the objectives of both are the same. However, with emphasis on the
user's point ofv.iew, the fnt objective in operations is restoration ofservice and then the qualiiy and economy of
service. Thus, isolation ofthe problem and providing allelll8tive means of service, by either manual or automated
means, bocome more important !han fixing tbe problem.
To manage a network remotely, i.e., to monitor and control network componems from a central location. network
management functions need to he bui.lt into the components of the network as much as possible. In tbat sense,
network component designs should include network 01anagement functions as part of their requirements and
speci.fications.
The computer or da.ta communication network has no1m3tured to the same ell1em a.
s the telephone network. Data
communications technology is merging with telephone technology. Dala and modern telecommunication networks
are evolving into broadband communication networks and are more complicated 1han the plain old telephone.
service (POTS). Analog audio and video services are migrating to digillll services. The analog hierarchy of low-to-
high bandwidth signals is being mmsmitted across the globe using a Synchronous Digital Hierarchy (SOH) mode.
Network management and operations of lhese digital networks are continuously being developed as new
l.echnologies emerge. Furlher, the telephone industry all over the world had been monopolistic and 1hus singlt>
vendor oriented. This is no longer true. Digital-based computer communications started 8ll a private industry and iS
hence m1~tivendor oriented. Unfortunately, this bas produced enoanous problems 10 users because network
components supplied by different vendors do not always communicate with eacb other. The network or
information systems manager. who has the responsibility of keeping the service alive all the time, has been
confronted with resolving the issue as oow tecbnology and oow vendor products emanate. This situation has been
recognized by various industrial and standard groups and is being continuously addressed.
1.2. Da.hl (Computer) 110d T elecommunication Network
Network communications lechnology deals with the lheorY and application of electrical engiooering, computer
engineering. and computer science to aU types of communication over networks. It also addresses accessing of
daUlbases and applications remotely over LANs 8ll well as switched and private lines. A basic network can be
vJe,ved as interconnected nodes and links as shown in Figure 1.2. A link carries infurmalion from one node to
another that. is directly connected to it. A node behaves as an end (tenninating or originaling) node, or an
intennediate node. or both. If the node behaves as an end node, infonnation either originates or tenninates there.
An intermediate node redirects the informalion from one link to another. End-office nodes mentioned in Section
1.1 behave as end nodes. A node can drop and add infur01ation channels and til the same time switch infurmation
t·ransparently between two links. EaCh end node has aconnection to a user interface if1he infOrmation originates or
termina1es !here. Tlti.s interface could use My type of equipment-audio, video, or Data Tenninating Equipment
(DTB). A DTE is anyequipment I hat generates or accepts digital da1a.
Flgul't 1.2. LogicAl Nttwnrk Modtt

VIdeo
EN: End NOC!o
IN. lnlermodialo NIXIe Wo.rkslallon
Daia coo be trnnsmilled eiiher in an analog or digital formal. The analog da!a are sent eilher·as a baseband (e.g.,
voice data from !he switching office 10 !he customer premises) or on top of a carrie.
r (e.g., cable TV). Digital data
are eilher directly generated by the user equipmem (e.g., computer 1erminnl) or as analog data and are convened lo
digital data (e.g., Integrated Services Digital Network. (ISDN) connection to cus1omer premises). The ]utter
scenario of the ability to handle integrated digital and analog signals is beooming extremely importanl as in the
case of multimedia broadband services. Management considerations associated with them are alsO very
oballenging, as we will sec in Pan lV. Long.<fistance data transmission today is mos1ly digital due 10 its superior
prioe and performance.
Data ore sen! from the originating to the terminating node via a direct link. or via a tandem ofliok.s and intermediate
nodes. Dala can be transmiued in one of three modes: circuit switched, message switched, or packet switched. Ln
!he circuit-switched mode, a physical circuit is established between the originating and terminating ends befure the
data are transmitted. The circuit is released or "tom down" aftercompletion oftransmission.
ln message-switched and packet-switched modes, data are broken int·o packets and each packet is enveloped with
destination and originating addresSes. 1lte message-switched mode is used to send long messages) such as emall.
The packet-switched mode is used to transmit small packets used in applications such as intera~1ive
communication. Bridges and routers open each packet to find the destination addre$5 and switch the data to the
appropriate output links. The path between thetwo ends may change during the transmission ofa message because
each packel may take a differenl route. They are reassembled in I he right order at the receiving end. The main
difference between message and packet swilcb.ing is thm in the former, data are stored by !he system and then

retrieved by the user at a later time (e.g, email). l,o the packet-switched mode, packets fire fragmented and
reassembled in almost real t·ime. They are stored in the system only long enough to receive aU the packets in the
message. ln Europe, X.25 packet-switched network was ex-tensively used in Public-Switched Data Network
(PSDN).
Neh~rk communications are commonly classified as either data communications or telecommunications. This
classif
tcation is based on historical evolution. The te.lephone network, which came into existence first, was known
as a telecommunication network. It is a circuir-swilcbed network that is structured as a public network accessible
by any user. The telephone network represents a telecommunication net,vork. The org-anization that provides this
service iscalled a telecommunication service provider (e.g., AT&T, British Telecom, NTI, BSNL, etc.).
With the advent ofoomptrtcrs, the terminology data communication network carne into vogue. It is also sometimes
called computer communication network. The telecommun1catiorts infrastructure was, and is, still used for data
communications. Figure 1.3 shows an early configuration of terminal-to-host and host-to-host commuoicat.ions,
and how data and telecommunication networks interface w ilh each other. To interface, a terminal or host connected
to an end-office switch communicates with the host connected to another end-office switch by modems at each
end. Modems transfer information from digitallo analog ai the source (telephone nehvorks carried analog signals)
and back to digilal at the destinatk>n.
Figurt t.l.Anotog•nd Data Ttltrommunlu rlon Nttworks
Modem telecommunication networks mostly carry digital data. The nodes in Figure 1.4 are digital switches.
Analog signals from telephones are converted to digital signals either at the customer premises or the central office.
figure 1.4 shows a corporate or enterprise .environment in the stage of the .evolution of data a.nd telephone
communications. A number of telephones and computer terminals at various corporate sites are connected by
telecommunication network. Telephones are locally interconne<:ted to each other by a local switch, PBX, at the
customer premises, which interfaces digitally to the telephone .
network. The computer terminals arecoMected to a
communication controller, such as a djgital mutt iplexer, which provides a single interface to the telephone network.
Figurt 1..&.. Oiaie:al Data and Te:IKOIIHUWJication NttVOI'k s

With the advent of desktop computers and LAN, data communication was revolutionized. Desktop computers
could communicate with each other over the LAN. This led to a Distributed Computing Environment (DCE),
which is discussed in tbe next section.
1.3. DL
~ttibuted Computing E nviron ment
Figure 1.5 shows a LAN with hosts and workstations. Let us ob.serve that dtey are workstations with processing
power and not just dumb terminals as described in the previous section. Any workstation can communicate with
any host on the LAN. Therecan be a large oumber ofworkstatioDS and bosts depending on the type ofLAN.D1Es
connected to different LANs that are gcogrnpbically far apari can communicate via telecommunication net,vork,
either public or private switched. The system of links eotu1ecting remote LANs is called a WAN. A LAN is
physically connected to a WAN by a bridge or a router as shown in Figure I.S(b). We will discuss the types of
LANs and WANs in Chapter 2. .First, we want to bring out two important aspects ofDCE in this section.
Figurt t..5. DCE with L
~Ns IUid WANs

~ 1l g
~
w...- ._ W<NWon
0 I ElJiemot I
~
I
1i
w-..
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(•1-ondVI-ool-"CCOIAo'l
Q~
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:=-'6
LANC
-%-- WNI
The first aspect is the question ofwhether the different plalforms and applications mooing on DCBs have the
ability to communicate with each other. In the early stage of communication network evolution, proprietary
interfaces between platforms and processeJ> were implememed by telecommunication service providers and
computer vendors to communicate autonomously within each of their networks. For example, Bell System, a
monopolistic telecommunlcatbn service provider, and IDM, the largest computer vendor, established transmission,
switching, and interface standards and manufuctured their own communications equipment to meet them. They
made significant contributions to the standards bodies to make such specifications the industry standards. For
customer premises equipment (CPE) interface, specifications are published for them to interlilce cleanly with the
network. For example, Bell System published specifications for Customer Service Unit (CSU) for customer
equipment to interface with the network. However, as the telecommunications industry rapidly grew, national and
intematb nal standards needed to be established for communication between equipment provided by various
vendors. Protocols and database st11ndards for handshaking and information exchan.ge are discussed in the
following sections. For now, we will assume that the different processors 1llld prooesses running on them collld
communicate with each other.
The second aspect of DCB is the ability of processors attached to LANs to do multiple functlons. They could
continue, as dumb terminals did, to request a bost to perfunn the functions and retmn the results. Alternatively,
they could request some special functions to be performed by a host-and it could be any processor in the
network-and receive the results. In this scenario, the processor that requests a service is called the client; and the
processor tbat provides the service is called the server. Such a configuration is termed a client- Saverenvironment.
Allhough the terminology of clieru and server is commonly associated with t.he processors, the more accurate

defnition shouk! be associated with the processes. Thus, the process that iniliates a transaction 1.0 run an
application in either a local or a remote processor is called the client. The application process that is invoked by a
client process is called ·the server. 1lte .serv-er returns the results to the client. Tbe application designed to take
advantage of such a capability in a network is called a clie.m- server architecture. With such an interpretation, the
e llen! and server processescan coexist in the same processor or in different processors.
We will now go into some detail on ·the salient characteristics and features ofclient-server architecture and models,
as they are very pertinent to nct~:>rk management applications and architecture. A simple client-server model is
shown in Figure 1.6. There is apt to be confusion between wh.ich is a client and which is a server in distributed
computing architedure. The 'best way to distinguish 'between the two is to remember that the client initiates the
request and the server responds.
Flgw·• 1.6. Simplt Clitni-Str'tr Modtl
Cllel'l
The client initiates a request to tbe server and waits. Tbe server executes tbe prooess to provide the requeSied
service and sends the resuk$ to the client. lt is worth noting that the client cannot initiate a process in thu server.
Thus. tbe process should have already been started in the server and be waiting for request.s to be processed.
A rea.l-world analogy to the clieot-server operation is a post offioe. The clerk behind the counter is ready and
waiting for a client. She is a server. When a customer walks in and initiates a transaction, for example, ordering
stamps, the clerk responds. The customer is the client. After the clerk gives me Sinmps to the customer, I.e., she has
delivered the resuks, the customer leaves and the cler.k, as a server, goes into a waiting modeuntil the next client
initiates a transaction.
As with any system, delays and breakdowns of COIIliDuoiCation need to be considered in this model The server
may be providing the service to many clients that are conncctoo to it on a LAN. as shown in Figure I.7(a). Eaeh
client's request is normally proces.~ed by the server according to the FrFO rule--f~rst in first out. This dei3y could
be min.im.ized, but not eliminated, by concun:eot processing ofrequests by the server. It is also possible that, due to
either the communication link or some other abnormal termination, the server may never return the result to th.c
client. The application on the client should be programmed to take care ofsllCh deficiencies in communication.
Fi~ur< 1.7. Clitni-Strvt r In Discrlbused Cumt>ulio.g.Environmeuc

.•
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Since the client and application are processes runnlng in nDCB, each oftbem can be designed to execute a specific
function efficiently. Further. each function may be under the jurisdiction of different departments in an
organization. An example ofthis is shown in Figure 1.7(b). joe.stooe@source.com (Joe Stone's user id) using a
client in a network sends a message to sally.jones@lest.com (Sally Jones' user id) on the network. The message
first goes to tbe mall server on the network. BefOre it can pro<:ess the request, the mall server needs to know the
network !!ddress ofsally.jones, which is dest.com. Therefore, it makes a requestto the domain name server (DNS)
on the network for routing information for the address ofdest.com. When it receives that information, it sends out
joe.stone' s message via the bridge connected to the network. It then sends a message to joe.stone on the client
stating that the message has been sent (or not sent because the dest.com address does not exist in the DNS). In ·this
e-
xample, the mail se.rver behaves both as a server and as a client. The three processes in this scenario, namely the
client, lhc mail server, and the DNS, are considered cooperative computing processes and may be running in three
separate platfonns on remote LANs connected by a WA:N. Communication between these processes is called peer-
to-peer communication. We wi.ll soon learn bow network. management fits into such a model nod manages
components on lbe network. that perform cooperative computing using peer-to-peer communication. However,
befOre we pursue that.. let ns first look at a new dimension that the DCE has caused ·networking to mushroom
into-t:helntemet.

lA. TCP/JP-Based Networks: Internet and .Intranet
Transmission Control Prot.ocoVlmemCI Prot.ocol (TCPIIP) Js a suile of protocols that enable networks to be
interconnected. It forms the basic foundation ofthe Internet. Architecture and protocols are discussed in detail in
Section 1.5. We will brie·fly Mscribe tbe role TCP/IP plays in Internet. Nodes in the network route packets using
network protocol IP, a connectionless protocol. That means there is no guarantee that the packet will be delivered
to the destination node. However, end-to-end communication can be guaranteed by using the transport protoco~
TCP. Thus, ifa packet is lost by LP, the acknowledgement process ofTCP ensures successful retransmission ofthe
packet.
TCP/TP suite of protocols contains more than TCP and IP protocols. TCP is a connection-oriented protocol A
complement to TCP is User Dalagrnm Protocol (UDP)., which is a co.nnectionless protocol. Much oflntemet traffic
really uses UDPIIP due to the reliability ofdata transmission. For example, email and management messages are
carried by connectionless transmission.
lbe Internet is a network of networks. Just as we can communicate over the telecommunication ·network using the
telephone from anywhere to anywhere in the world today, we can now communicate worldwide over thecomputer
network via email. We looked at the example of Joe St.one sending a message to Sally Jones in the previous
section, Figure 1.7(b). Let us expand that example and visualize that Joe Stone, who is at the College ofComptrting
building of Georgia lnstintte ofTechnology, is sending an email to Sally Jones at her home in Australia. SaJiy is
connected to an Internet service provider, ostrich. com. Similar to a unique telephone number that each station has
in the telephone world, each person has a unique address in the computer communication netwOrk. Joe's email
address isjoe@cc.gatecb.edu and SaUy's address issally@ostrlcb.com.au.
Figure 1.8 shows an lnt.emet configuration fOr our scenario. Assume that Joe is at Workstation A on LAN A
sending the ernall to Sally at Workstation Z that is "telccormected" to her Internet service provider's email server
on LAN Z. Two serve.
rs shown on LA~ A are mail server and DNS. J't should be noted that the servers do not b.we
to be on the same LAN as the sender's LAN, as shown in Figure 1.8. The two servers cooperatively transmit the
email message to LANCon the computer network made up ofbridges and routers. lbe link between LAN A and
LAN C could bea WAN. tnfurmation is transported exclusively based on TCPITP-based protocols. We will explain
TCP/LP protocol in Section 1.5.2.
Flgurt t.8.1nttrnet Conllgurnclon

lnfonnation from LAN C progresses vill gateways and WANs to the computer communications network in
Australia, as shown in Pigure 1.8. The WAN network shown is composed of a ser.ies of networks, not all
necessarily using TCP/TP prot~ol Gateways between them serve as the interfaces between dissimilar and
independent autonomous networks and perfurm many functions including protocol COilversions. Autnnomous
networks have liitle knowledge ofeach other's aitrlbutes, configumlions, and addresses and yet communication is
automatically taken care ofey a bierarcbyoflnternet servers along the path.
Joe's email message finally reaches the email server on LAN Z in Australia and is stored there until Sally retrieves
it via her Internet link with an Internet service provider's server. ln fact, email messages are trMsmitie.d by a

"store-and-furward" scheme all along lhe path. 1n addition, the final sLage in the Lntemetlink uses a TCPIIP suite
ofprotocols.
Thus, viathe Interne!, any user can communicate with any other user in any pan of the world as IQng as both are
connected to n network that is pan of the lnternel. This .has aIso revolutionized the software user interfuce
providing capabilities li.ke web pages so that you can gather information about any1hing in the world instantly
through the 1nternet.
Another per.speclive ofthe Internet is to view it as a layered architecture, as shown in Figure 1.9. This architecture
shows the global Internet as concentric layers of workstations, LANs, and WANs interconnected by fubries of
Medium Access Controls (MACs), switches, and gateways. Workstations belong to the user plane, LANs to the
LAN plane. and WANs to the WAN plane. The interlilces are defined as the fabdcs. MAC fabric interfaces the
user plane t·o the LAN plane. LAN and WAN planes interface through switching fabric. WANs in tlte WAN plane
interface wii.h each other via the gateway fa'bric.
Flgun 1.9. loltrott Fobri< Mod<l
~~ GatowiiYIOb<icl
( ] SWitchlnolab<lc
MACiob1C
USER PLANE
The user's workstation intermces to a LAN via a MAC. which will beexplained in Chapter 2. LANs internee to a
WAN by a switching fabric of bridges, routers, and switches. Enoh WAN may be considered as an acrtooomotl~
network, and hence needs a gateway to communicate with another WAN. Gateway fllbric iotercOtmects different

WANs. Thus, a single lnternet plane at the core of the model multiplies into millions and mlllions of users at the
user plane, with virtuaiJy no limits in sight.
Communlcation between two users in the user plane, i.e., logical link connection on the user plane, takes the
following path. The physical path traverses the MAC fabric, the LAN plane, the switching fabric, the WAN plane,
and the gateway fabric to the core and then returns (o the user plane going through all the planes and interface
fabrics in reverse..
The huge success oflnternet teclmology has spawned Intranet h::chnology. The main distin~1ion between lhe two is
similarto that between public and private switched networks. An intranet is a private network and access to it is
controlled by the enterprise that owns it. whereas the Internetis public.
The impaot of ihe Internet in nelvorking is enormous. How do we manage the Inte.met? For example, ifan email
does not reach its destination, how do we detect where the communication broke down? How do we take
advan111ge of lnten-.et ·capabilities to impl.eme.nt network manage.ment? We have not yet defined network
management and how it fits into the client-server environment. However, before we define what network
management is, let us briefly look at the protocols and protocol architecture that enable successful communication
between different components on the network.
1.5. Commun.ic:ttion Protocols and Standar ds
Consider a fax machine and a modem bought from a local store successfully sending a fux to a modem and fax
machine anywhere in the wodd. even though each fax machineand attacl-.ed modem were manufuctured by local
vendors. Likewise, isn't it a technological miracle thattOJ computers located anywhere in the world can transmit
messages to each other as long as each is connected to the Internet? The key to the practical success of these and
other such teohnologies is the interoperability of ihe two end devices. More and more vendors in more and more.
countries have recognized that in this world of shrinking cyberspace and advancing modem communication
technology, interoperability is the key to the success oftheir business,
Universal interoperabllity is achieved when all participants agree to estllblish common operational procedures. In
communications lingo, commonal.lty can be interpreted as standards and procedures as protocols. Let us consider
the scenario ofJoe sending an email from Georgia Institute ofTechnology(GA Tech) in Atlanta to a colleague in a
Japanese Telecommunications Company (ITC) in Tokyo. Joe oomposes the message on his comprrter terminaland
sends it to llis colleague (yoho@jtc.com.jp). Joe's message with his user id (joe@cc.gatech.edu) and IP address
(169. I11.103.44) goes through several changes befure it is transmitted on tl-.e plrysical LAN medium at GA Tech.
The message goes to its College of Computing (cc)'s email server, which oblnins the IP address of the destination
and sends the message out on the Internet. The message traverses several nodes and links and arrives at the post
office box ofYoho's mail server at JTC. She establishes a session in her computer and gets the complete message
thai Joe transmitted. ln this seenario, Joe's message is wrapped with several layers of control information at
various times and is broken down into packet unitS and reassembled at the destination. AII these steps happen each
time without any loss or error in ihe message due to standard.ization and modular (layered) architecture of data
communication protocols. As we w Wsoon learn in this section, the popularity oflnternet as a peer-to-peer network
has been mnde possible by the peer-to-peer protocol TCP/IP suite.
Architecture can be defirled as ·modeling a system into functional components and the relationship among ihem.
Thus, communication architecture deseribc.s the functional components of oommunication network as well as the·
operational intcr:filce between dtem. Operational procedures-both intra· and iuter-modules--ere specified in te.rms
of protocols. Just as human communication is made mutually understandable by speaking a common language,
communication protocols are standardized for service interfaces from the perspectives ofboth a service provider
and a service user. If diffi:rent vendors implement the same standards in thei.r sy·stem components, then
communic11tion between iheir different components can be universal. Standa.rdization of protocols involves
agreement in the physical characteristics and operational procedures between communication equipment providing
similar functions. Thus. looking at our example, all fax machines are able to comrnunicale with eacb other because

all vendors bave implemented standards recommended by loternational Telecommun.ication Union-
Telecommunications Sec10r (ITU-T). Similarly, email exchange across !he world ls possible because most vendors
have adopted Intemet standard Simple MailTransport Pm10eol (SMTP) in ·!heirsoftware. However, there are email
software packages other than SMTP, and the user has to i.os.tall a gateway in those.systems to convert back and
filrlh between SMTP and the vendor-specific proprietary protocol For example, lBM Lotus uses oc:mail (now
defunct), and any network tl111t uses oc:mail bas to implement a gateway (o send an e.mail over the Internet. Note
·!hat there are different mail protocols (SMTP, !MAP, POP, etc.~ whlcb have different procedures. We will now
look atlhe details ofcommunication architecture.
1.5.1. Commm1ication A•·chitectures
Communication between users (human beings using a system) and applications (programs that run in a system)
occurs at various levels. They can communicate wah each olher at the application level, lhe highest level of
communication architecture. Alternatively, they can exchange Information at the lowest level, the physical
mediUl.D. Each system can be broadly subdivided into two sets of communication layers. The top set of layers
consists of application layers and the bottom ~1 tronsport layers. The users-nd users include application
program!O-interface with the application level layer, and the communication equipment interfaces with the
physical medium. The basic communication architecture 1$ s.hown in Flgure 1.10. In Figure 1.1O(a), the two end
systems associated with the two end nodes communicat.e dirCclty with eaob other. Direct communication occurs
between lhe corresponding cooperating layers of each system. Thus, lransport layers can exchange infonnatioo
with each other, and so can lhe application layers and the users.
SVaollnA
t•lOOiet CoMmunl<a!M BMw..,. EIC!Sy<l...,.
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This can be illustrated w.itb a real-life example. A bearing-impaired pers~n, accompanied by an interpreter,
arteoded oneofmy classes. As llecmred, the interpreter t.ranslated to the student using sign .language. Ifthe student
had a que·stion, the interpreter translated the information &om sign language, orally to the da.~s and me. In this
llluslration, the bearing-impaired Sll1dent aod I are at the application layer. The interpreter di:l the protocol
conversion attheapplication layer level. 1lte transport layer is the aural aod vL~al media.
Figure I.J ()(b) shows the end systems communicating v.ia an intermediate system N, which enables the use of
different physical media for the two end systems. System N converts the transport layer information into the
appropriate protocols. Thus, system A could be on a copper wire LAN and system Z could be on a fiber optic
cable.
Var.
ious standard organizations propose, deliberate, and establish standards. One of the internationally re·nowned
standard organizatiolls is International Standards Organization (ISO). lSO has developed a highly modular, or
layered, architecture for communication protocols that is called the Open Systems Interconnection (OSI) Reference
Model, published as OSl RM-ISO 7498. This model was developed based on the premise abat the different layers
of protocol provide different services; and tbat each layer can communicate with only its own neighboring level.
Two systems can communicate on a peer-to-peer level, Lbat is. at the same level ofthe protocol. The OSl protocol
architecture with all seven layers is shown in Figure 1.11. Table 1.1 describes the salient features of, and services
provided by, each layer. Layers 1-4 are the transport system protocol layers and layers 5-7 aro application support
protocol layers.
Figurt 1.11. 051 Protocol Laytrs
t
l~7 Aj>f>li<ooon
layet& Pr~
"-5 ~"
~·
TIMspo<t
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~2 0."'-"'k
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l
Tablt 1.1. OSI Lay•l"5 and Strvi<ts
Layer Layer Name· Salient Services Provided by the·Layer
No.
1 Physical -Transfersto and gathers from the physical medium raw bit data

Tablt 1.1.. OSI LAy<rs Rnd Strvkes
Layer Layer Name SalientServices Provided bythe layer
No.
2 Data nnk
3 Network
4 Transport
s Session
-llandles physical and electrical Interfaces to the transmission medlum
-Consists oftwo sublayers: logical link control (llC) and Media access control (MAC)
- llC: Formats the data togo on the medium; performs errorcontrol and flow control
-MAC: Controls data transfer to and from LAN; resolves conflicts with other data on LAN
Formsthe·swltchlng/routll'lg layer ofthe network
- Multlplexll'lg and de-multlplexll'lg of messages from applications
-Acts as a transparent layer to applications and thus isolates them from the transport system
layers
-Makes and breaks connections for connectlo,...oriented communications
-Data flow control In both directions
-Establishes and dears sessions for applications, and thus minimizes loss of data during large data
exchal'lge
6 Presentation - Provides a set of standard protocols so that the display would be transparent to syntax of the
application
-Data encryption and decryption
7 Application - Provides applcatlo,...speclfic protocols for each specific application and each specific transport
protocol system
OSI protocol architecture ITuly enables building systems with open interfuces so that networks using systems from
different vendors ore interoperable. Figure 1.12 expands the bas·ic communication architecture shown in Figure
I.I 0 to an OS! model figure 1.12(n) is a direct end-to-end communication model. The corresponding layers in the
two systems communicate with each other on a peer-to-peer protoool ioter.
l3ce associated with those layers. ln
Figure 1.12(b), the end systems communicate with each other by going ·through an intermediate node/system.
Agnln. notice that the physical media connected to the end systems could be different. The intermediate s}'stem is
involved only up to the first three layers in the process. Layers 4-7 are not involved in the intennediate system.
This is analogous to a mail container with letters enclosed in envelopes being transported from one 10wn to another
town anywhere in the world. It does not matter what .network ofintermediate cities (nodes) it goes through, or wbat
netwo(k of transportation media-surface, air, or water-it takes to get to the destination. The letter in the
envelope and contents of pa.ckages are untouched at the ITnnsfer points and are only handled by the sender and the
receiver; i.e., user applications.

Figurt I.U. OSI Communltullon Archlltc!lurr
EroS~Z
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The message in each layer is contained in message units called protoool data unit (PDU). h consists oftwo parts-
protocol control information (PCI) and user da.ta (UD). PCI contains header information about the layer. UD
contains the data ihat the layer, acting as a service provider, receives from or transmits10 the upper layer/service
user layer. The PDU communication model between two systems A and Z. including Lhe users at the top and IJ1e
u:ansmissioo medium at the bottom of the PDU layers, is shown io Figure 1.13. As you can see, the size of the
PDU increases as il goes tow81ds lower layers. If the size of the PDU exceeds the maximum size of any layer
specificauons, it. is the.n.fragmeote.d into multiple packets. Thus, a single application layer PDU could multiply into
several physical PDUs.
Figu•·e 1.13. PDU Communication Model between £nd Sy.s1ems

I lh«A
I u-z I
l t
Ai>!~ic:at.... Applicotlon
Prqwm1~ton Pleson"dtion
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l.5.2.1>rotocol Layet'S :1nc.l Set·vices
We will OOv go into some detail re~ding services provided by the seven layers ofOSI protocols.
Layer I, physical layer, is responsible fur physically p.
lacing the electrical sigonl on the physical medium and
picking up the signal from it. It controls and manages the physical and electrical interfu.ce.s to the physical medium
including the connector or the transceiver. The physical medium could be copper in the form ofa twisted pair or
coaxial cable, optical fiber, or wireless media such as radio. microwave, or infi'ared. The signal could be either
analog ordigital. There are various protocol standards fur a physical-layer interface depending on the transmission
medium and the type of signal. The 1wo classes of standards have been established by ITU-T and Electronics
Industries Association (EIA).
Layer 2 is the data link control layer, or data link layer for short. Data communication between two DTEs is
comroUed and managed by this layer. Note tllat in contrast to a. byt<>oriented tronsmlssion across a computer bus,
the data communication is a serial-bit-<>riented stream. The data link layer needs to do basic functions: first
establish and cle.ar the link, and second tra.nsmit the datn. Be.sides these, it also does error control and data
compression. Flow control on data link layer is done on a bop-to-hop basis.
For point-to-point communication using a dedicated facility, like the loop link from a customer telephone to the
telephone compa.ny switching office, the data link control is simple and stril.iglltfurwa.rd to implement. However, if
the DTE is connected to a LAN, or which is shared tf811smission media and is accessed simultaneously by many
users, then the data link control beoomes more complex. In the case of point-to-multipoint tmnsmission, the he!KI
end controls the access oft.he medium. LAN is a distributed environment and tllus access control is di.stributed. ln
an OSI-layered model, the data link layer is divided into to,w sublayers-logical link control (LLC) and media
access control (MAC), as shown in Figure 1.14. The lower MAC layer controls the access and transmittal ofdata to
U1e pllysicallayer in an algorithmic manner. There are three basic types ofLANs. Ethernet LAN is n bus type a.nd
the media is accessed using a distributed probabilistic algorillun. Carrier Sensing Multiple Access with Collision
Detection (CSMAJCD). The second type ofLAN is a ring type U
1lld in token ring (fR) and Fiber Distributed Data
lnterface (FOOl). A deterministic token-passing algorithm is used in this case. The third type. ofLAN is deployed
In wireless medium and is referred to as wireless LAN or WLAN. The probabilistic algoritlun, Carrier Sensing
Multiple Access with Collision Avoidance (CSM.A/CA), is used to access the medium . Random-access protocol
will be covered in Chapter 2.
Figure t.l4.Subtoytr Srruc:turt of• OAt.• Link l'rotoc:ol la~'fr

Netwcrk
Logical Link Control
(LLC)
lled1um Ace<:>$ Control
(MAC)
F'llysloal
LLC performs link management and dara transfer. Link management includes formaning the data ro go on the
medium, pe.rrorming error contro~ and flow control. If there is security required, it could be included in the ILC
sublayer.
The network layer is the third layer in the OSI protocol stack. It controls and manages the switching fabric of tb.e
·network. It provides both connectionless network service (CLNS) and oonnection-oriented ·network service
(CONS). The former is used when lower layers are highly reliable, such as LANs and bridges, as weU as when
messages are short. CONS is the method fur transmitting long messages, such as file transfer. It is also used when
the transmission medium is not reliable. It subdivide.s the transpol1 PDUs into !Tames ofappropriate size based on
transmission parameters. The destinalbn address ofeach packet is read in both CLNS and CONS at the network
layer and routed 011 the appropriate link.
A router, or a routing bridge, at the nodes ofa network perforras the function ofrouting and switching data. Any
subnetwork oftl~e node is under thecontrol ofthat router. The subnetwork(s) can be anything &oma simple-single
segment LAN to complex subnetworks operating under a proprietary protocol. OSI architectural model handles
this by dividing the network layer into three sublayers as shown in Figure 1.15. The lop sublayer is the
Subnetwork-Independent Convergence Protocol (SNICP) layer Ibm interfaces to the transport layer. l 'he Internet
communicares between nodes using Internet address and SNICP. llte nodes in tum communicate with subnetworks
using the Subnetwork-Dependent Convergence Protocol (SNDCP), which depends on thesubnetwork protocol and
could be any proprietary protocol In such a situation, the SNDCP communicates with its data link layer via the
third network sublayer, the Subnetwork-Dependent. Access Protocol (SNDAP). This subnetwork arc.hitecture
isolates transpon and the above layers from the subnetwork dependencies. It also enables communication between
a DTE on dte lntemet and a DTE on a subnetwork node, as shown in Figure 1.16. Figure I. I6(a) depicts network
configuratbn in which DT£..A connected to end node A communicates with DTE-NI connected to subnetwork
Mde·Nl via ·the intermediate system gateway node N. Figure 1.16(b) describes the path ofcommunication through
different protocol layers from the originating end system to the terminating end system vta the intermediate node
gateway. The formats of the PDUs are identical in all three systems at SNICP layer levels and above. Access
networks having their own addressing scheme using Network Address Translator (NAl) or Dynamic Host
Configuration protocol (DHCP) can be implemented using tltis scheme.
flgurt l.t5. SublayuStruclurt or a i'lrtwork Protoool Laytr

Transport
SNICP
Networli SNDCP
SNOAP
Oatallnk
SNICP: SubnetWOtt-tndepend9nt Con~ergence Protocol
SNOCP: Subnetwork-Dependent Convergence Protocol
SNOAP; Sulrletwork-Oependent Adapler Protocol
Flgu•·• 1.16. Caccwoy Communlralion coPrivoct Subnecwork
A-lh! s!Mda-dNll!wcirl<
N· U1-N2-N3Sotlne!worUIOefNOde N
ll'iln~ r -
SNICP
I~
SNJCP
SNOOP SNDCP
SNJC
OP-SN
SNO~P SNDN' SNOA1'-S«
tataLmlti 1
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SNOCP-sN
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(b) Pl'o4acol Olmml.,loa....,

The most used network protocol is tbe Internet Prorocol (IP) and has been PQpularized by the Internet. It is part of
the Internet suite of the TCP!IP and is a CLNS protocol. In OST terminology. It is called ISO-IP or ISO CLNP. A
connection-oriented OSI protocol is X.25 PLP, Packet Layer Protocol.
A popular scheme ofimplementing private subnetwork is to establish a network. with a private IP address, sucb as
1O.x.y.z. In this insrance, the gateway node, known asNAT, converts the global IP address to the local proprietary
IP address. fur example, LAN Z in Figure 1.8.
The transport layer is the fourth layer ofthe OSl protocol. It multiplexes the OD provided byapplication layerS and
passes packets to the network layer. Its se.rvicc is independent ofthe network on which the packets are transmitted.
The transPQrt layer can ag~~in be connectionless or connection oriented and is implemented in hoth Internet and
OS! protocols. As mentioned earlier, TCP is a component of the IP suite nod is conoection oriented. The
connect·ionless t·ransport protoool in a TCP/IP suite is called Lhe UDP. Plow control is also implemented in
tmnsport layers and functions as data rate manager between application programs and the network layer. ISO has
five transport layer specifications, TPO to TP4. TP4 is analogous to TCP.
Layers 5-7 arc application layer protocols. £xcepl in the OS! Reference Model, the tltree application layers are not
clearly separuted and independent. Let us look at each layer as ifthey were independent., like in the OSJ mode~ to
understand their specific fimctions and services provided. An application process commuolcates with flllother
application process during a seso;ion. The session layer services establish communication at the beginning of the
session. monitor, sync.hronill!, and error correct the information exchanged during the session. and then release the·
logical link at the end ofthe session. H is very strongly nilatcd to the presentation layer, which is the medium of
prese.:ttation ofthecontext ofthe mess.~ge to the user or application program. In that sense, the presentation layer is
a context-sensitive layer. ll can be interpreted as the common language and image that the users at hoth ends ofthe
system use and understand- shared semantics of the two end users. A common abstract syntax that is used for
semantics is Abstract Syntax Notlltion Number One (ASN.I). Although the primary function of the presentation
layer is the conve.rsion ofsyntax. data encryption and data oompression are also generally done in that layer.
The lop and the seventh protocol layer is the application layer. The application 'Process interfaces with the
application support processes tbat are provided by this layer. Uke the other two layers in the set ofapplication
layers (session and presenration), it is strongly coupled with the restofthe application layers. In the OS! Reference
Model, one can separate these processes &om the presenration and session layers, but in other models there is no
clear distinct·ion of the functions. Figure 1.17 presents a comparison of the models-OSI Reference Model and
Internet model.
Frguo
•r t.t7. Conoroartson qfOSI anollnltmtll'roloc:ot l,ayrr M<>oltl(

OSI INTERNET
Appllca~oo
Pro~rttnt.on
Appllcati.,.,.Spa:lfiCl
Prorocals
$<>10$000
TtlltllJIUO
fron!li>Ort ConOOCI...,.. I Conoll':lian·
le!!il: UOP orit~tlld. TCP
SNICP
N~l""'r~
N
o!WC!1(
SNOCP
I~
IP
SNOAP
Oatn ~Ink
Not S(lft(!~l>d
l't1)Sital
The Internet model does not specey the two lower layers although H
· is obvious Lhat !hey use distributed LAN and
WAN configurations. The tmnsport and network layers fotm the suite of TCPIIP protocols that we mentioned
earlier. Application layers arc combined into application-specific protocols.
Figure 1.18 shows a comparison offuur common applicat·ion-specific protocols in OST and Internet models. There
are more OSl applicalioo-specifie protocols, which we will not discuss here. All application-specific protocol
services in OS! are sandwiched between the user and pre-
sentation layers. In the lntemet mode~ drey are
sandwiched between the user and thetransport layer. The boxes on the right-hand side ofFigure 1.18 describe the
comparable scrvites offered in the two model'!. A user intedaces with a host as a remote terminal using Virtual
Te.
rmloal (VT) in the OS! model and TELNET in the Internet model. File transfi:rs are accomplished using File
Transfer Access and Management (FTAM) in !he OSl model and File Transfer Protocol (FTP) in the Internet. The
most common used mail service function in tbe Internet i<; Simple Mail Transfer Protocol (SMfP). A similar
protocol io the OS! model is the Message-Oriented Te-xt lnte.rchange Standard (M.OTIS). Network management is
accomplished using the Common Management InfOrmation Protocol (CMlP) in the OSr model and the Simple
Network MmuigemenL Protocol (SNM.P) in the Lntemel. We viii extensively discuss tbe details of SNMP in this
book. CMIP is briefly discussed in Appendix for completeness. However, it is imporUlnt to understand tbe overaii
picture of protocol layers and other application protocols to appreciate network management fimctions that are
accomplished using network management protocols.
flgur• 1.18. APt>Utailon-SI!OciRc: Protorols tn OSI and lnitn>tl Mod•IS

,.--1---:c'--,.,.--'--~
1.6. Network~, Systems, alitl SL•n•ices
~ ~
m - _J
{~I
( '::'I
We described a network comprising nodes and links in Section 1.2. The phys.ical embodiment ofa network·can be
deftned as a system. Thus, the nodes nod links are components of a network system. Just as a network can be
subdivided into subnetworks. a system comprises subsystems. A system or subsystem is made up of network
elements. Network elements can be either active or passive. Thull, a router is an octive network element, whereas a
splitter or a combiner !bat divides or combines signal energy is a passive element. A link could also be an active or
a passive component. 1n the case of an active transmission link, it can be subdivided into active nodes and passive
transmission media.
Servioes are fun~'lions ihat users derive out of networks and systems. Neiworks and systems exist to provide
service to the users. Service providers provide telecommuoicatlon services to subscribers and customers using
networks and systems.
J.(i.l . .Broutl blind Networks. Systems. 1
md Sl'n'ices
A broadband communication system can be defined as one that provides broadband service to homes and
enterprises. The common interpretation ofthis definition in practice·varies in different countries as weU as among
various service providers. ln the· most comprehensive defmition of !be term, we will define broadband
communication system as one that provides voice, video, and data services over the same medium to customer
premises. Broadband service comprising audio, video, and dara is also known as multimedia service.
Audio service includes telephone., telephone conference, and radio broadcast. Although the end terminals could be
either analog or digital devices, inrormation is carried digitally in the context of broadband service. A system
providing this service is tmly a real-lime information system.
Video service includes broadcast television, interactive television, video-oiHlemand, and video conference
services. Video service could be either real-time or quasi (near) real-time service. Once again, the presentation
could be on eitber analog or digital terminals.
Data service includes numerous applications, whi.ch can be classified into three categories: store-and-fofvard,
audio streaming, and video streaming. Some· examp.les of store-and-forward service are email. messaging, and
Web-based applications. Audio and video broadcast and streaming services mentioned above sucb as MPJ and
video-oiHlemand can in a sense be considered under this category. They are not sensitive to absolute delay time
'between the source and the destination, but are affected by delay variations orjitter.
Broadband services are provided using broadband nehvo(ks. There are nume.rous types ofnetworks to choose from
depending on what segment and what type of service one needs. It is like ordering ice cream in an ice-cream
pnrlor---ooneorcup, hard or soft; size smaJJ/mediwn/large. choice offlavor, choice oftopping, etc.

The Lhree segmenLsofbroadband network are WAN, broadband access network, and CPE nemmk.lobroadband
tenninology, the CPE network is also called home network when the customer premises is a residence. Network
segments and choices in various segments are shown in Figure 1.19.
Flgur • 1.19. Broadband NtlworkS.gmtnb and Ttcbnul~gltll
INIIIII
-··
llloliol:><l<
The WAN and access network interface with each other via !he edge rouLer. The demarcation point between the
access network and CPE network is shown as the residential gateway. Although 1his is the logical demarcation
point the physical de.marcation point between the access network oftbe service provider and the customer-owned
CPE, or home uetwork, could be different. As an example in the cable network, the demarcation point is called
Network illtcrfuce UnJL (NTU) or Network lnterfuce Device (NID) and is the physical termination of the cable
access network outside the house. Tbe residential gateway·may onnay not·exist, and ifit does, it is a part ofCPE
network.
1.6.2. Wide Area etwork<i
The four leadmg networks and protocols that are used in broadband WAN are Internet using Asynchronous
Transfer Mode (ATM), Synchronous Optical Network (SONB1), IP, and Multiprotoco.l Label Switching (MPLS)
network.
ATM. network: ATM network is ideally suited for WAN or core network. It has fast. layer 2 switches that can be
configured to func1ion in parallel and thus can process bigb data rate cell-oriented packets. l...alc:ncy can be set in
ATM. switches by setting priorities to tbe different services-real-time and non-real-tim~!Kling provided
Furthe-r. traffic·perfbrmance is iooreased by establishing Virtual Path-Virtual Circuit (VP- VC).
Four classes oftruflic have beeo defined in ATM. network to implemenL quality ofservice. COostaol bit rate (CBR).
real-time variable bit rate (VBR-R.T), oon-.real-time variable bit rate, (VBR-NR.T), and available blt rate (ABR) or

user bit rate (UBR). Transmission of voice is assigned CBR. An example ofVBR-NRT is transmission of stiU
images. Data 1raffic and store-and-forward traffic get the lowes! priority, ABR.
SONEf: An optical fibe.r medium can be used to carry multiplexed lower bandwidth signals implementing SDH.
This mode of transmission is known asSONET. The Oplicaltransmission network oontains regenerators, digital
cross·oonnect elements, and add-and-drop multiplexers (ADM). Modem optical networks use dense wavelength
division multip.lexers (OWDM) and very high bandwidth signa Is can be transmitted.through dtis optical network.
Internet: The lntemet backbone WAN using IP is highly matured. bas a full set of application·oriented li:atures,
and can interface with access and CPE network fn a more seamless manner. However, its main drawba.ck is that it
is difficult to meet qualit.y-Qf-service requirements needed for multimedia broadband service. Because of its
variable packet size. and packets choosing possible alternate padts between the source and the dcstin!llion, th.e
performance ofrouters and other transmission devices is not as efficient as in an ATM network.
Quality ofservice in IP-ori.ented WAN traffic is improved by implementing one oftwo different approaches. They
arc integrated service [RFC 2205] and differeotlated serv.
ice [RFC 2474]. Jn one form of implementation, lntserv
packets in dte·lntemct are classified into dtree classes: guaraateed, controUed or predictive, and best effort. Intserv
rese.rves bandwiddt from dte source to dte destination on a pe.r-flow basis fur a guaranteed class-of-service call or
session using reservation protoool, RSVP. Once the reserved path with dte necessary bandwiddt is established, dam
arc transmitted.The bandwidth is released after the calVsession is completed. lntse.rv is not an efficientscheme for
establishing quality ofservice in the backbone network as the.re is no guaran.tee that the resources will be available
wben needed. Furdter, the scheme does not scale weU.
In the diffi:rcntiated service, diffserv, packets belonging to the same class are grouped at each hop and then
prioritized. There are four classes and each class bas dtree subclasses for dropping packets-low, medium, and
bigb. The present tre.nd in providing quality of sc..Yvice ror backbone is to use diffe.reotiated service comple.mented
with some form ofreservation capabilities ofRSVP.
MPLS network: MPLS attempts to oombine the benefits of ATM quality ofservice with feature benefds ofthe IP-
based Internet. Conventional routers examine the packet headers and classify them into forwarding equivalence·
classes (FEC). They are then assigned the next hop.1n MPLS this is done once; possibly at tbe ingress router, and a
label is attached to it. At each router, only the label lookup is done for detem1ining the next bop. Label lookup can
also be done using a switch. A router that silpports MPLS is known as a Label SwitchingRouter (LSR). MPLS can
support nny network layer protoool. RFC 3031 describes MPLS nrchitecture fur an IP network layer protoool.
1.6.3. Broutlbund Access Networks
Figure 1.20 shows six types of broadband access networks dtatprovide broadbiiJld service to homes, Small Office
Home Office/Small and Medium Enlerprise (SOHO/SM£), and enterprises. The core network is ll'/ATM/MPLS
WAN. The l.ink from the head e.nd or dte edge router to business customers is shown as an optical earrier-n (OC-n)
link, afthough it could be any other transport scheme. Hybrid fiber coax (HFC) cable network and Digital
Subscriber Line (DSL) nelwodt are dte matured access networks. Fbted wireless is bei.ng offured as point-to-
multipoint service or meshed oetwork. W!Max, 10 metropolimn areas. Mobile wireless could be offered using
either 3G technology or wi~less !.,AN. The furmer has the limit<Ilion on data rat.e and the latter on range. Fiber
network as Passive Optical Network (PON) is still in an embryonic stage fur economic reasons.
Figuc
·• 1.20. BroiKlb•od A<tt5!l N<IWttrks

Cable Access Network has its head eod interfacing to t.he edge router. Analog and digital signals from various
service.s are multiplexed at the head end and are converted &om on electrical signal to optical wavelength signals.
The optical signal is then carried over fiber up to an intermediate point, optical node, where it is dow~Konverted to
radi:> frequency and transmitted the rest ofthe way to the cust"omer premises over two-wny coaxial cable, hence the
term hybrid fiber coax (HFC). At the customer premises, the TV analog signal is split from the digital data. The
latter is demodulated to a baseband digiml signal using a cable modem and is fed to the digiml devices, such as
computer and appliances.
Digital Subscriber Une access ·network uses a telephone line and can be deployed uSing different
implemcnmtioos, refe.
rred to as XDSL. Of tl~ese, Asymmetric DSL (ADSL) shown in Pigure 1.20 is the most
prevalent deployed all over the world. AUhough cable network is more commonly used in the United Smtes by a
ratio ofapprox.imately 2 'to I, the reverse is the case in the rest of the world. The technology uses the .existing
unshielded twisted-pair (UTP) wire that carries the analog voice to transmit data in addition to voice. The voice is
carried as an analog signal at the low end ofthe frequency spectrum (0-4 ld:lz) and the digital dam over the higher
band of1he spectrum. It is termed asymmetric as 1he downstream data rate (from the centraI office to customer
premises) is much higher than the upstream (1iom customer premises 10 the eent.ral office) data rare. The analog
voice and digital dam are separated at both e.nds of the aocess network using a fiker, and the digital dam are
modulated and demodulated at both ends using ADSL modems. Atlhe central office, voice circuit interfaces with
U1e central office~·witch and the digit.al daia with the edge router.
Wireless Access Networks: Figure 1.20 shows three types of wireless access networks. The terrestrial wireless
network, also known as fixed wireless, is a point-to-multipoint transmission. A base smtion with mullipleantellll8S
covers multiple sectors, each serving many subscribers. The two well-known deployed technologies are
Multichannel Muh:ipoint Distribution Service (MMDS) for rural areas and WiMax fur urban areas. Satellite
wireless syste.ms are primarily used for on~>,vny televisi:m broadcasting service. Mobile wireless has limited
bandwidth and is currently used In phones such as smart pbooes, providing bl:oadband service.
1.6.4. Homf/CJ>E etworks

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