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`Ericsson Exhibit 1014
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`Page 1
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`Ericsson Exhibit 1014
`Page 1
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`

`

`Computer Networks
`
`Third Edition
`
`Andrew S. Tanenbaum
`
`Vn'je Universiteit
`Amsterdam, The Netherlands
`
`For book and bookstore information
`
`http://www.prenha|l.com
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`as
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`5%
`#5
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`Prentice Hall PTR
`Upper Saddle River, New Jersey 07458
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`_.____.—————
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`Ericsson Exhibit 1014
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`Page 2
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`Ericsson Exhibit 1014
`Page 2
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`
`
`Library of Congress Cataloging in Publication Data
`
`Tanenbaum, Andrew S. 1944-.
`Computer networks / Andrew S. Tanenbaum. -- 3rd ed.
`p.
`cm.
`Includes bibliographical references and index.
`ISBN 0—13-349945-6
`
`1.Computer networks.
`TK5105.5.T36 1996
`004.6--d020
`
`I. Title.
`
`96-4121
`CIP
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`Editorial/production manager: Camille Trentacoste
`Interior design and composition: Andrew S. Tanenbaum
`Cover design director: Jerry Votta
`Cover designer: Don Maninetti, DM Graphics, Inc.
`Cover concept: Andrew S. Tanenbaum, from an idea by Marilyn Tremaine
`Interior graphics: Hadel Studio
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`© 1996 by Prentice Hall PTR
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`The publisher offers discounts on this book when ordered in bulk quantities. For more information,
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`All rights reserved. No part of this book may be reproduced, in any form or by any means, without
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`All product names mentioned herein are the trademarks of their respective owners.
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`Printed in the United States of America
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`ISBN 0-13-349945-6
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`Ericsson Exhibit 1014
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`Page 3
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`Ericsson Exhibit 1014
`Page 3
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`

`

`SEC. 1.4
`
`REFERENCE MODELS
`
`29
`
`Below we will discuss each layer of the model in turn, starting at the bottom
`layer. Note that the OSI model itself is not a network architecture because it does
`not specify the exact services and protocols to be used in each layer.
`It just tells
`what each layer should do. However, ISO has also produced standards for all the
`layers, although these are not part of the reference model itself. Each one has
`been published as a separate international standard.
`
`Layer
`
`Name of unit
`exchanged
`
`.
`.
`Application protocol
`_
`
`Applicatlon < ------------------------------------ > Application
`
`
`5 Fa--——-—--§9§§'9'—‘Prm°°°'-------------
`
`r
`'
`------------P-resentatloqpolocpl —————————— :- Presentation
`
`
`
`Session
`
`7
`
`6
`
`4
`
`3
`
`
`“HI
`Iii HIll
`i 4— —-4-
`
`
`APDU
`
`PPDU
`
`SPDU
`
`TPDU
`
`Transport
`
`< ------------------------------------ > Transport
`
`Network
`
`+~- 4-
`
`+ a-..
`
`Network
`
`Packet
`
`Data link
`
`Frame
`
`Physical
`
`Bit
`
`Host B
`
`Host A
`
`Flouter
`
`Router
`
`Network layer host-router protocol
`Data link layer host-router protocol
`Physical layer host-router protocol
`
`Fig. 1-16. The OSI reference model.
`
`The Physical Layer
`
`|
`
`The physical layer is concerned with transmitting raw bits over a communi—
`cation channel. The design issues have to do with making sure that when one side
`sends a 1 bit, it is received by the other side as a 1 bit, not as a 0 bit. Typical
`
`vh—
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`Ericsson Exhibit 1014
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`Ericsson Exhibit 1014
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` E
`
`34
`
`INTRODUCTION
`
`CHAP.
`
`1
`
`different file naming conventions, different ways of representing text lines, and so
`on. Transferring a file between two different systems requires handling these and
`other incompatibilities. This work, too, belongs to the application layer, as do
`electronic mail, remote job entry, directory lookup, and various other general-
`purpose and special-purpose facilities.
`
`Data Transmission in the OSI Model
`
`Figure 1—17 shows an example of how data can be transmitted using the 081
`model. The sending process has some data it wants to send to the receiving pro-
`cess. It gives the data to the application layer, which then attaches the application
`header, AH (which may be null), to the front of it and gives the resulting item to
`the presentation layer.
`
`Sending
`Process
`
`Receiving
`Process
`
`
`
`
`
`
`
`
`Application
`layer
`Presentation
`layer
`
`Session
`layer
`Transport
`layer
`Network
`layer
`
`Data link
`layer
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Application protocol
`
`_______________________________
`-—
`Presentation protocol
`
`
`Session protocol
`
`___________
`
`
`
`
`Transport
`PFOlOCOI
`Network
`protocol
`
`_
`
`
`
`__,
`
`
`
`
`
`
`
`
`Application
`layer
`
`layer
`
`Session
`layer
`Transport
`layer
`Network
`layer
`
`Data link
`layer
`
`
`
`
`
`Physical
`Physical
`layer
`layer
`
`
`‘\ Actual data transmission path
`
`Fig. 1-17. An example of how the 081 model is used. Some of the headers may
`be null.
`(Source: H.C. Folts. Used with permission.)
`
`The presentation layer may transform this item in various ways and possibly
`add a header to the front, giving the result to the session layer.
`It is important to
`realize that the presentation layer is not aware of which portion of the data given
`to it by the application layer is AH, if any, and which is true user data.
`This process is repeated until the data reach the physical layer, where they are
`actually transmitted to the receiving machine. On that machine the various
`
`
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`Ericsson Exhibit 1014
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`Page 5
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`Ericsson Exhibit 1014
`Page 5
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`

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`
`
`412
`
`THE NETWORK LAYER
`
`CHAP. 5
`
`too dicey. Combined with encryption and packet filtering, this arrangement offers
`a limited amount of security at the cost of some inconvenience.
`It is easy to
`One final note concerns wireless communication and firewalls.
`design a system that is logically completely secure, but which, in practice, leaks
`like a sieve. This situation can occur if some of the machines are wireless and usc
`radio communication, which passes right over the firewall in both directions.
`
`5.5. THE NETWORK LAYER IN THE INTERNET
`
`At the network layer, the Internet can be viewed as a collection of subnet~
`works or Autonomous Systems (ASes) that are connected together. There is no
`real structure, but several major backbones exist. These are constructed from
`high—bandwidth lines and fast routers. Attached to the backbones are regional
`(midlevel) networks, and attached to these regional networks are the LANs at
`many universities, companies, and Internet service providers. A sketch of this
`quasihierarchical organization is given in Fig. 5-44.
`
`Leased lines
`to Asia
`
`US backbone
`
`Leased
`transatlantic
`
`European backbone
`
`
`
`
`IP Router
`
`SNA
`network
`
`D
`
`\ Tunnel
`
`National
`network
`
`
`
`2.!
`
`
`
`
`
`
`
`J_
`lP Ethernet
`LAN
`
`Regional
`network
`
`
`
`
`
`
`IP token bus
`LAN
`
`IP token ring LAN
`
`Fig. 5-44. The Internet is an interconnected collection of many networks.
`
`The glue that holds the Internet together is the network layer protocol, IP
`(Internet Protocol). Unlike most older network layer protocols, it was designed
`from the beginning with internetworking in mind. A good way to think of the net—
`work layer is this.
`Its job is to provide a best-efforts way to transport datagrams
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`Ericsson Exhibit 1014
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`Page 6
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`Ericsson Exhibit 1014
`Page 6
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