`
`LIBRARY OF CONGRESS
`
`l“WNWIIHIIIM||l||WINlllWWIIllIWIIIHIHIII
`
`
`UUDDBE‘BSLLA
`
`
`
`Ericsson Exhibit 1041
`Ericsson v.
`|V1, |PR2018—00727
`Page 1
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`Ericsson Exhibit 1041
`Ericsson v. IV1, IPR2018-00727
`Page 1
`
`

`

`
`
`
`
`Again, for my loving wife Tricia Antigone
`7/6/03
`* ’7
`
`
`
`
`
`
`
`
`i
`
`'
`
`
`
`
`
`
`
`
`
`mo
`
`56:51
`
`Copyright © 1989, Macmillan Publishing Company, a division of Macmillan, Inc.
`Printed in the United States of America
`All rights reserved. No part of [his lmuk may be reproduced or tmnsrnilterl in any form or by any
`trim-um. electronic or mechanical, including photocopying. recording, or any information storage
`and retrieval system, without permission in writing from the publisher.
`
`Macmillan Publishing Company
`866 Third Avenue, New York, New York 10022
`
`Collier Macmillan Canada, Inc.
`
`Library of Congress Cataloging in Publication Data
`
`/ William Stallings.
`
`Stallings, William.
`ISDN :
`an introduction
`p.
`cm.
`Bibliography: p.
`Includes index.
`ISBN 0-02-415471-7
`1. Integrated services digital networks.
`TK5103.7.S73 1989
`004.6--dc19
`
`I. Title.
`
`\
`
`88-11083
`CIP
`\x J}
`
`Printing212345678
`
`Year29012345678
`
`
`
`Ericsson Exhibit 1041
`Ericsson v.
`|V1, |PR2018—00727
`Page 2
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`

`

`
`
`CONTENTS
`
`PREFACE
`
`V
`
`CHAPTER 1
`INTRODUCTION
`
`T
`
`2
`i The Arrival of lSDN
`1
`1~2 The Computer-Communications Revolution
`1-3 From Communications to Computers
`6
`1 A From Computers to Communications
`11
`1—5 Outline of the Book
`14
`
`5
`
`PART I
`INTEGRATED DIGITAL NETWORKS
`
`17
`
`CHAPTER 2
`CIRCUIT SWITCHING
`
`19
`
`wenboom—n
`we???CD\|O~O'I
`
`19
`Overview
`One—Node Networks
`Space-Division Switching
`Time—Division Switching
`Digital Carrier Systems
`Routing
`41
`Control Signaling
`Summary
`61
`
`51
`
`23
`
`25
`29
`37
`
`ix
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`

`x I CONTENTS
`
`Recommended Reading
`2—9
`2-10 Problems
`62
`
`62
`
`CHAPTER 3
`PACKET SWITCHING
`
`65
`
`Overview
`
`66
`
`
`
`00903030090030)000000
`
`
`
`—'—'~O®\|O~O'Ib(JON—I—-‘O
`
`67
`Internal Operation
`Comparison of Circuit Switching and Packet
`Switching
`71
`Application of Packet Switching
`Routing
`78
`Congestion Control
`X.25
`89
`
`74
`
`86
`
`Fast Packet Switching
`Summary
`107
`Recommended Reading
`Problems
`108
`
`102
`
`107
`
`CHAPTER 4
`IDN TECHNOLOGY
`
`1 T T
`
`1 The Evolution of IDN
`
`1 1 1
`
`2 Digital Subscriber Loops
`3 Signaling System Number 7
`4 Software Defined Networks
`
`1 15
`
`122
`138
`
`Recommended Readings
`Problems
`147
`
`145
`
`5 6
`
`PPENDIX 4A Analog and Digital Data
`Transmission
`148
`
`4-
`4-
`4-
`4-
`4-
`4-
`A
`
`APPENDIX 4B Digital Encoding of Analog Data
`
`151
`
`PART II
`
`INTEGRATED SERVICES DIGITAL
`
`NETWORKS
`
`T55
`
`CHAPTER 5
`ISDN OVERVIEW
`
`157
`
`5—1 A Conceptual View of ISDN
`5-2
`ISDN Standards
`272
`
`157
`
`5-3 Recommended Reading
`5-4 Problems
`182
`APPENDIX 5A CCITT
`
`183
`
`182
`
`
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`

`

`0000Illll
`0000
`
`03\l0UlboJl\)—I
`
`\ITI\I\I\I\Iomme—I
`
`oooooooooaoomoom
`0&L5555bL
`
`~0~0~I0~O~0Cflwa—I
`
`CONTENTS
`
`xi
`
`215
`
`CHAPTER 6
`ISDN SERVICES
`
`185
`
`T85
`
`Service Capabilities
`Facsimile
`195
`209
`Telex
`Teleservice Protocol Architecture
`Message Handling Systems
`226
`Summary
`238
`Recommended Reading
`Problems
`239
`
`239
`
`CHAPTER 7
`
`ISDN ARCHITECTURE
`
`243
`
`Transmission Structure
`User—Network Interfaces
`
`243
`252
`
`259
`Addressing
`268
`lnterworking
`Recommended Reading
`Problems
`273
`
`273
`
`CHAPTER 8
`
`ISDN PROTOCOLS
`
`275
`
`ISDN Protocol Architecture
`ISDN Connections
`277
`Physical Layer
`Lap—D
`292
`304
`Layer 3 User-Network Interface
`ISDN User Part of Signaling System Number 7
`Summary
`327
`Recommended Reading
`Problems
`328
`
`275
`
`328
`
`281
`
`314
`
`CHAPTER 9
`
`BROADBAND ISDN
`
`331
`
`Broadband Services
`BlSDN Architecture
`
`332
`344
`
`352
`Summary
`Recommended Reading
`Problems
`352
`
`352
`
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`

`xii
`
`| CONTENTS
`
`APPENDIX A
`
`FLOW CONTROL, ERROR DETECTION, AND ERROR
`CONTROL
`355
`
`Flow Control
`A-l
`A-2 Error Detection
`A—3 Error Control
`
`355
`360
`368
`
`A-4 A Comparison of Protocols
`A-5 Recommended Reading
`A-é Problems
`374
`
`372
`374
`
`APPENDIX B
`
`THE OSI REFERENCE MODEL
`
`377
`
`l Motivation
`
`377
`
`379
`
`2 Concepts
`385
`3 Layers
`-4 Perspectives on the Open Systems Interconnection
`Model
`388
`
`5 Recommended Reading
`6 Problems
`390
`
`389
`
`GLOSSARY
`
`39I
`
`REFERENCES
`
`397
`
`INDEX
`
`407
`
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`

`CHAPTER 3
`
`
`PACKET
`SWITCHING
`
`Around 1970, research began on a new form of architecture for long—distance
`digital data communications: packet switching. Although the technology of packet
`switching has evolved substantially since that time, it is remarkable that: (l) the basic
`technology of packet switching is Fundamentally the same today as it was in the
`early—Iq'Ftls networks, and (2) packet switching remains one of the few effective
`technologies for long—distance data. cornmnnications. Even with the continuing
`evolution and increasing digital capability of long—haul circuit—switched networks,
`packet switching will continue to play an important role in integrated digital net‘
`works (IDNS).
`rl'his chapter provides an overview of packet switching technology. We will
`see thal many of the advantages of packet switching (flexibility, resource sharing,
`robustness, responsiveness) come with a cost. The packet-switched network is a
`distributed collection of packet—switched nodes. in the ideal, all packctvswitched
`nodes would always know the state of the entire network. Unfortunately, because the
`nodes are distributed, there is always a time delay between a change in status in one
`portion of the network and the knowledge of that change elsewhere. Furtl'lern'iore,
`there is overhead involved in communicating status information. As a result, a
`packet-switched network can never perform “perfectly," and elaborate algorithms
`are used to cope with the time delay and overhead penalties of network operation.
`The chapter begins with an introduction to packet—switched network opera-
`tion. Next, we look at the internal operation of these networks. introducing the
`concepts of virtual circuits and datagrarns. Following this, the key technologies of
`routing and flow control are examined. The chapter concludes with an introduction
`to fast packet switching, which is one of the few genuine recent advances in packet-
`switehing technology and will be important in the evolution of the IDN and [SDN
`networks.
`
`65
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`66 l CHAPTERS Pocket Switching
`
`3-] OVERVIEW
`
`The long-haul circuit—switched telecommunications network was originally
`designed to handle voice traflic, and the majority of traffic on these networks
`continues to be voice. A key characteristic of circuit—switched networks is that
`resources within the network are dedicated to a particular call. For voice connec-
`tions, the resulting circuit will enjoy a high percentage of utilization since, most of
`the time, one party or the other is talking. However, as the circuit—switched network
`began to be used increasingly for data connections, two shortcomings became
`apparent:
`
`0
`
`0
`
`In a typical terminal-to-host data connection, much of the time the line
`is idle. Thus, with data connections, a circuit—switched approach is
`inefficient.
`
`In a circuit—switched network, the connection provides for transmission
`at constant data rate. Thus both devices that are connected must
`transmit and receive at the same data rate. This limits the utility of the
`network in interconnecting a variety of host computers and terminals.
`
`To understand how packet switching addresses these problems, let us briefly
`summarize packet-switching operation. Data are transmitted in short packets. A
`typical upper bound on packet length is 1000 octets (bytes). If a source has a longer
`message to send, the message is broken up into a series of packets (Figure 3—1). Each
`packet contains a portion (or all for a short message) of the user’s data plus some
`control information. The control information, at a minimum, includes the informa-
`tion that the network requires in order to be able to route the packet through the
`network and deliver it to the intended destination. At each node en route, the packet
`is received, stored briefly, and passed on to the next node.
`
`Packets
`
`User data
`
`
`
`FIGURE 3-] Pockets
`
`
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`3—2
`
`Internal Operation | 67
`
`Let us return to Figure 2-1, but now consider that this is a simple packet—
`switched network. Consider a packet to be sent from station A to station E. The
`packet will include control information that indicates thal [he intended destination is
`E. The packet is sent from A In node 4. Node 4 stores the packet, determines the next
`leg of the route (say 5), and queues the packet to go out on that link (the 4—5 link).
`When the link is available, the packet is transmitted to node 5, which will forward the
`packet to node 6, and finally to E. This approach has a number of advantages over
`circuit switching:
`
`O Line efficiency is greater, since a single node—to-node link can be
`dynamically shared by many packets over time. The packets are queued
`up and transmitted as rapidly as possible over the link. By contrast, with
`circuit switching, time on a node-to-node link is preallocated using
`synchronous time—division multiplexing. Much of the time, such a link
`may be idle because a portion of its time is dedicated to a connection
`which is idle.
`0 A packet—switched network can carry out data—rate conversion. Two
`stations of different data rates can exchange packets since each connects
`to its node at its proper data rate.
`II When traffic becomes heavy on a circuit—switched network, some calls
`are blocked; that is, the network refuses to accept additional connection
`requests until the load on the network decreases. On a packet—switched
`network, packets are still accepted, but delivery delay increases.
`Priorities can be used. Thus, if a node has a number of packets queued
`for transmission, it can transmit the higher—priority packets first. These
`packets will therefore experience less delay than lower—priority packets.
`
`I
`
`3-2
`
`INTERNAL OPERATION
`
`Switching Technique
`
`A station has a message to send through a packet-switched network that is of
`length greater than the maximum packet size. It therefore breaks the message up into
`packets and sends these packets, one at a time, to the network. A question arises as to
`how the network will handle this stream of packets as it attempts to route them
`through the network and deliver them to the intended destination. There are two
`approaches that are used in contemporary networks: datagram and virtual circuit.
`In the datagram approach, each packet is treated independently, with no
`reference to packets that have gone before. Let us consider the implication of this
`approach. Suppose that station A in Figure 2-1 has a three-packet message to send to
`E. It transmits the packets, 1-2-3, to node 4. On each packet, node 4 must make a
`
`T i
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`
`68 ‘ CHAPTERS Pocket Switching
`
`routing decision. Packet 1 arrives for delivery to E. Node 4 could plausibly forward
`this packet to either node 5 or node 7 as the next step in the route. In this case, node 4
`determines that its queue of packets for node 5 is shorter than for node 7, so it queues
`the packet for node 5. Ditto for packet 2. But for packet 3, node 4 finds that its queue
`for node 7 is now shorter and so queues packet 3 for that node. So the packets, each
`with the same destination address, do not all follow the same route. Because of this, it
`is just possible that packet 3 will beat packet 2 to node 6. Thus it is possible that the
`packets will be delivered to E in a different sequence from the one in which they were
`sent. It is up to E to figure out how to reorder them. Also, it is possible for a packet to
`be destroyed in the network. For example, if a packet—switched node crashes mo-
`mentarily, all of its queued packets may be lost. If this were to happen to one of the
`packets in our example, node 6 has no way of knowing that one of the packets in the
`sequence of packets has been lost. Again, it is up to E to detect the loss of a packet and
`figure out how to recover it. In this technique, each packet, treated independently, is
`referred to as a datagram.
`In the virtual circuit approach, a preplanned route is established before any
`packets are sent. For example, suppose that A has one or more messages to send to E.
`It first sends a special control packet, referred to as a Call Request packet, to 4,
`requesting a logical connection to E. Node 4 decides to route the request and all
`subsequent packets to 5, which decides to route. the request and all subsequent
`packets to 6, which finally delivers the Call Request packet to E. If E is prepared to
`accept the connection, it sends a Call Accept packet to 6. This packet is passed back
`through nodes 5 and 4 to A. Stations A and E may now exchange data over the route
`that has been established. Because the route is fixed for the duration of the logical
`connection, it is somewhat similar to a circuit in a circuit—switching network, and is
`referred to as a virtual circuit. Each packet now contains a virtual circuit identifier as
`well as data. Each node on the preestablished route knows where to direct such
`packets; no routing decisions are required. Thus every data packet from A intended
`for E traverses nodes 4, 5, and 6; every data packet from E intended for A traverses
`nodes 6, 5, and 4. Eventually, one of the stations terminates the connection with a
`Clear Request packet. At any time, each station can have more than one virtual
`circuit to any other station and can have virtual circuits to more than one station.
`So, the main characteristic of the virtual—circuit technique is that a route
`between stations is set up prior to data transfer. Note that this does not mean that this
`is a dedicated path, as in circuit switching. A packet is still buffered at each node, and
`queued for output over a line. The difference from the datagram approach is that,
`with virtual circuits, the node need not make a routing decision for each packet. It is
`made only once for all packets using that virtual circuit.
`If two stations wish to exchange data over an extended period of time, there are
`certain advantages to virtual circuits. First, the network may provide services related
`to the virtual circuit, including sequencing and error control. Sequencing refers to
`the fact that, since all packets follow the same route, they arrive in the original order.
`Error control is a service that assures not only that packets arrive in proper sequence,
`
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`

` Virtual Circuit Advantages
`
`INTERNAL OPERA TION
`
`Virtual Circuit Advantages
`
`O Connection-oriented services,
`such as sequencing, and error
`control may be provided.
`0 Routing decisions are not re-
`quired for each packet for each
`node, but only once at setup
`time. Thus packet transmission
`and delivery may take less time.
`
`EXTERNAL SER VICE
`
`
`
`Datagram Advantages
`
`0 Call setup time is avoided. This
`is an advantageforshorttransac—
`tions.
`¢ Network congestion can be by—
`passed, improving delivery per—
`formance.
`0 Network failures can be by—
`passed, improving reliability.
`
`Datagram Advantages
`
`0
`
`
`
`3-2
`
`Internal Operation .69
`
`BOX 3-]
`
`COMPARISON OF VIRTUAL CIRCUITS AND
`DATAGRAMS
`
`
`Supports connectionless appli—
`0 Provides the user with connec-
`cations.
`tion—oriented services, such as
`0 Avoids call setup time.
`sequencing and error control.
`
`
`but that all packets arrive correctly. For example, ita packet in a sequence from node
`~l to node 6 fails lo arrive at node 6, or arrives with an error, node 6 can request a
`retransmission otthat packet from node 4. Another advantage is that packets should
`transit the network more rapidly with a virtual circuit; it is not necessary to make a
`routing decision For each packet at each node.
`One advantage of the datagram approach is that the call sch Ip phase is avoided.
`’l"hus, ita station wishes to send onlyr one or a Few packets, datagram delivery will he
`quicker. Another adval'ltage of the datagi'aro service is that, hccausc it
`is more
`primitive, it is more flexible. For example, it congestion develops in one part ol- the
`network, incoming datagrams can be routed away from the congestion. With the use
`of virtual circuits, packets Follow a predefined route, and thus it is more difficult for
`the netwmk to adapt to congestion. A third advantage is that {latagrarn delivery is
`inherently more reliahlc. With the use oi virtual circuits, ita node tails, all virtual
`circuits that pass through that node are lost. With datagrani delivery, if a node tails,
`suhschenl packets may find an alternate route that bypasses that node.
`
`
`
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`70 i CHAPTER3 Pocket Switching
`
`Box 3-1 summarizes the relative merits of the two approaches. Most
`eiltr-entlyavailable packet—switched networks make use of virtual circuits for their
`internal operation To some degree this reflect a historical motivation to provide a
`network thai 111esenis a service as reliable (in terms of sequencing) as :1 Circuit-
`switched network There are, however, several providers of private packetswitched
`
`(a)
`l-packet
`message
`
`(b)
`2-packet
`message
`
`(C)
`5-packet
`message
`
`(d)
`iO—packet
`message
`
`
`
`
`
`
`
`W/WW
`
`
`
`
`
`
`WW
`
`
`
`
`
`
`III-
`
`
`
`
`WW/fi
`fl/W/W
`
`
`-II—
`Wfl/fl’
`---
`
`/////§4”é
`Wfl/i/
`
`WW1?//
`“--
`[f/ifi/Z/
`l\
`
`
`fi/ux"§/////%
`
`
`WW
`
`
`WWfi
`
`
`
`
`WW
`
`
`
`W9
`
`
`
`
`
`X
`
`a
`
`b
`
`Y
`
`FIGURE 3-2 Effect of Pocket Size on Transmission Time
`
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`

`3-3 Comparison of Circuit Switching and Pocket Switching
`
`7]
`
`networks that make use of datagrams operation. From the user’s point of view, there
`should be very little difference in the external behavior based on the use of datagrams
`or virtual circuits. If a manager is faced with a choice, other factors such as cost and
`performance should probably take precedence over whether the internal network
`operation is datagram or virtual circuit.
`
`Pocket Size
`
`One important design issue is the packet size to be used in the network. There
`is a significant relationship between packet size and transmission time, as shown in
`Figure 3—2. In this example, it is assumed that there is a virtual circuit from station X
`through nodes (1 and b to station Y. The message to be sent comprises 30 octets, and
`each packet contains 3 octets of control information, which is placed at the beginning
`of each packet and is referred to as a header. If the entire message is sent as a single
`packet of 33 octets (3 octets of header plus 30 octets of data), then the packet is first
`transmitted from station X to node a (Figure 3-2a). When the entire packet is
`received, it can then be transmitted from a to b. When the entire packet is received at
`node b, it is then transferred to station Y. The total transmission time is 99 octet—
`times (33 octets X 3 packet transmissions).
`Suppose now that we break the message up into two packets, each containing
`15 octets of the message and, of course, 3 octets each of header or control informa—
`tion. In this case, node (1 can begin transmitting the first packet as soon as it has
`arrived from X, without waiting for the second packet. Because of this overlap in
`transmission, the total transmission time drops to 72 octet—times. By breaking the
`message up into 5 packets, each intermediate node can begin transmission even
`sooner and the savings in time is greater, with a total of63 octet-times. However, this
`process of using more and smaller packets eventually results in increased, rather than
`reduced delay, as illustrated in Figure 3—2d. This is because each packet contains a
`fixed amount of header, and more packets mean more of these headers. Further—
`more, the example does not show the processing and queuing delays at each node.
`These delays are also greater when more packets are handled for a single message.
`Thus, packet—switched network designers must consider these factors in attempting
`to find an optimum packet size.
`
`3-3 COMPARISON OF CIRCUIT SWITCHING AND
`PACKET SWITCHING
`
`Having looked at the internal operation of packet switching, we can now
`return to a comparison of this technique with circuit switching. We first look at the
`important issue of performance, and then examine other characteristics.
`
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`72
`
`CHAPTERS Pocket Switching
`
`(a) Circuit switching
`
`(b) Virtual circuit packet
`switching
`
`(c) Datagram packet
`switching
`
`Propagation delay
`/ Processing delay
`
`Call
`signal
`
`<——Time
`
`Call
`packet
`
`Call accept
`signal
`
`Acknowledge-
`mentsignal
`
`=-——...._ Call accept \i\|
`’4; packet
`PKT2 PKTl
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`PKTZ PKTI
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`this;
`PKT3 P
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`PKT3
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`32E
`|PKT3 PKTZ
`PKT3 Acknow—
`ledgement
`packet
`
`
`
`
`
`
`
`
`
`.,
`.
`MESSAQL
`R72;
`
`
`
`Liv}:
`
`
`
`line
`
`line
`
`
`
`
`
`line
`
`..— qu——>-a—n-
`l
`2
`3 4\ /
`Nodes
`FIGURE 3-3 Event Timing for Various CommUnicotion Switching
`Techniques
`
`l
`
`2
`
`3
`
`4
`
`l
`
`2
`
`3
`
`4
`
`Performance
`
`A simple comparison oicircuit switching and the two forms otpaclcet switch-‘
`ing is provided in Figure 3—3. The figure depicts the transmission ofa message across
`four nodes. From a source station attached to node 1 to a destination station attached
`to node 4.
`For circuit switching, there is a certain amount ofdelay before the message can
`he sent. First, a call request signal is sent through the network, to set up a connection
`to the destination. lithe destination station is not busy, :1 call accepted signal returns.
`Nott- that a processing delay is incurred at each node during the call request; this time
`is suenl at each node setting up the route of the connection. 0n the return, this
`processing is not needed since the connection is already setup. After the connection
`is set up,
`the message is sent as a single block, with no noticeable delay at
`the
`switching nodes.
`Virtual—circuit packet switching appears quite similar to circuit switching. A
`virtual circuit is requested using a call request packet, which incurs a delay at each
`
`Ericsson Exhibit 1041
`Ericsson v.
`|V1, |PR2018—00727
`Page 14
`
`Ericsson Exhibit 1041
`Ericsson v. IV1, IPR2018-00727
`Page 14
`
`

`

`3-3 Comparison of Circuit Switching and Packet Switching
`
`73
`
`node. The virtual circuit is accepted with a call accept packet. In contrast to the
`circuit-switching case, the call acceptance also experiences node delays, even though
`the virtual circuit route is now established. The reason is that this packet is queued at
`each node and must wait its turn for retransmission. Once the virtual circuit is
`
`established, the message is transmitted in packets. It should be clear that this phase of
`the operation can be no faster than circuit switching, for comparable networks. This
`is because circuit switching is an essentially transparent process, providing a constant
`data rate across the network. Packet switching requires some node delay at each node
`in the path. Worse, this delay is variable and will increase with increased load.
`Datagram packet switching does not require a call setup. Thus, for short
`messages, it will be faster than virtual circuit packet switching and perhaps circuit
`switching. However, since each individual datagram is routed independently, the
`processing for each datagram at each node may be longer than for virtual-circuit
`packets. Thus, for long messages, the virtual circuit technique may be superior.
`Figure 3—4 is intended only to suggest what the relative performance of the
`techniques might be; however, actual performance depends on a host of factors,
`including the size of the network, its topology, the pattern of load, and the character-
`istics of typical exchanges. The interested reader may pursue these topics in
`[KLEI76], [ROSN82], [SAND80], [KUMM80], [MIYA7S], and [STUC85].
`
`Other Characteristics
`
`Besides performance, there are a number of other characteristics that may be
`considered in comparing the techniques We have been discussing. Table 3—1 summa-
`rizes the most important of these. Box 3-2 attempts to summarize some of the key
`relative merits of circuit switching and packet switching.
`
`
`
`
`
`
`
`Private
`
`
`
`Trafficvolume
`
`packet-switched
`
`
`
`
`
`Dedicated
`circuits
`
`
`
`Pubhc
`
`
`packet-switched
`
`
`Circuit-switched
`
`
`Interactive
`(Bursty)
`
`Traffic mix
`
`Batch
`(Stream)
`
`FIGURE 3-4 Alternatives for Data Communications [BLAC87)
`
`Ericsson Exhibit 1041
`Ericsson v.
`|V1, |PR2018—00727
`Page 15
`
`Ericsson Exhibit 1041
`Ericsson v. IV1, IPR2018-00727
`Page 15
`
`

`

`74
`
`CHAPTERS Packet Switching
`
`TABLE 3-] COMPARISON OF COMMUNICATION SWITCHING
`TECHNIQUES
`Virtual-Circuit
`Datagram Packet
`Packet Switching
`Circuit Switching
`Switching
`No dedicated path
`No dedicated path
`Transmission of packets
`Transmission of packets
`
`Dedicated transmission path
`Continuous transmission of
`data
`
`Fast enough for interactive
`Messages are not stored
`
`The path is established for
`entire conversation
`
`Call setup delay. Negligible
`transmission delay
`Busy signal if called party
`busy
`Overload may block call
`setup; no delay for
`established calls
`Electromechanical or
`
`computerized switching
`nodes
`
`Fast enough for interactive
`Packets may be stored until
`delivered
`Route established for each
`
`packet
`Packet transmission delay
`
`Sender may be notified if
`packet not delivered
`Overload increases packet
`delay
`
`Small switching nodes
`
`Fast enough for interactive
`Packets stored until
`delivered
`Route established for entire
`conversation
`
`Call setup delay. Packet
`transmission delay
`Sender notified of
`connection denial
`
`Overload may block call
`setup; increases packet
`delay
`Small switching nodes
`
`Network may be responsi-
`ble for individual packets
`Speed and code conversion
`
`Network may be responsi—
`ble for packet sequences
`Speed and code conversion
`
`User responsible for
`message loss protection
`Usually no speed or code
`conversion
`Fixed bandwidth transmis—
`sion
`No overhead bits after call
`Overhead bits in each packet
`Overhead bits in each packet
`
`setup
`
`Dynamic use of bandwidth
`
`Dynamic use of bandwidth
`
`3-4 APPLICATION OF PACKET SWITCHING
`
`Although we will later in this chapter explore some of the details of packet-
`switching technology, we are already in a position to comment on the applicability of
`this networking approach (Box 3-3). Recall that we said that packet switching held
`certain advantages over circuit sWitching for data communications. In particular,
`packet switching may make more efficient use of internal (to the network) communi—
`cations resources and allow devices of difiering data rates to interconnect. However,
`in order to be more specific about the applicability of packet switching, we need to
`examine in more detail the nature of the data communications traffic.
`
`Data communications trafiic can be roughly classified into two categories:
`stream and bursty. Stream traffic is characterized by lengthy and fairly continuous
`transmission. Examples are file transfer, telemetry, other sorts of batch data process-
`
`
`
`Ericsson Exhibit 1041
`Ericsson v.
`|V1, |PR2018—00727
`Page 16
`
`Ericsson Exhibit 1041
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`Page 16
`
`

`

`3-4 Application of Pocket Switching l 75
`
`
`
`BOX 3-2
`
`RELATIVE MERITS OF CIRCUIT SWITCHING
`AND PACKET SWITCHING OF DATA
`
`CIRCUIT SWITCHING
`
`Advantages
`
`Disadvantages
`
`. Compatible with voice. Econo-
`mies of scale can be realized by
`using the same network for
`voice and data.
`
`Commonality of calling proce-
`dures for voice and data. No
`
`special user training or commu—
`nication protocols are needed to
`handle data traffic.
`
`0 Subject to blocking. This makes
`it diflicult to size the network
`
`properly. The problem is less
`severe with the use of dynamic
`nonhierarchical
`routing tech-
`niques.
`Requires subscriber compatibil-
`ity. The devices at each end of a
`circuit must be compatible in
`terms of protocol and data rate,
`since the circuit is a transparent
`connection. Furthermore,
`for
`each terminal connected to a
`
`line
`
`a separate physical
`host,
`into the host is required.
`Large processing and signal
`burden. For
`transaction—type
`applications, data calls are of
`short duration and need to be set
`
`up rapidly. This proportionally
`increases the overhead burden
`on the network.
`
`PA CKET SWITCHING
`
`Advantages
`
`Disadvantages
`
`conversion.
`speed
`0 Provides
`Two attached devices with dif-
`
`ferent data rates may exchange
`data;
`the network buffers the
`data and delivers it at the appro-
`priate data rate.
`
`' Complex routing and control.
`To achieve efficiency and resil-
`ience,
`a packet—switched net—
`work must employ a complex
`set of routing and control algo—
`rithms.
`
`
`
`
`
`Ericsson Exhibit 1041
`Ericsson v.
`|V1, |PR2018—00727
`Page 17
`
`Ericsson Exhibit 1041
`Ericsson v. IV1, IPR2018-00727
`Page 17
`
`

`

`76 | CHAPTERS Pocket Switching
`
`BOX 3-2 continued
`
`Advantages
`
`Disadvantages
`
`0 Delay. Delay is a function of
`load. Itcanbelong anditisvari—
`able.
`
`0 Appears nonblocking. As the
`network load increases,
`the
`delay increases, but new ex—
`changes are usually permitted.
`0 Efficient utilization. Switches
`and trunks are used on demand
`
`rather than dedicating capacity
`to a particular call.
`0 Logical multiplexing. A host
`system can have simultaneous
`conversations with a number of
`
`terminals over a single line.
`
`ing applications, and digitized voice communication. Bursty traffic is characterized
`by short, sporadic transmissions. Interactive terminal—host traffic, such as transaction
`processing, data entry, and time-sharing, fits this description.
`Figure 3—4 shows the relative applicability of four alternative networking
`approaches. The circuit-switched network approach makes use of dial—up lines.
`The cost is based on data rate, connection time, and distance. As we have said, this is
`quite inefficient for bursty traffic. However, for occasional stream—oriented require—
`ments, this may be the most appropriate choice. For example, a corporation may
`have distributed offices. At the close of the day, each office transfers a file to
`headquarters summarizing the activities for that day. A dial-up line used for the
`single transfer from each office appears to be the most cost-effective solution. When
`there is a high volume of stream traffic between a few sites, the most economical
`solution is to obtain dedicated circuits between sites. These circuits, also known as
`leased lines or semipermanent circuits, may be leased from a telecommunications
`provider, such as a telephone company, or from a satellite provider. The dedicated
`circuit carries a constant fixed cost based on data rate and, in some cases, distance. If
`the traffic volume is high enough, then the utilization will be high enough to make
`this approach the most attractive.
`On the other hand, if the trafiic is primarily bursty, then packet switching has
`the advantage. Furthermore, packet switching permits terminals and computer ports
`of various data rates to be interconnected. If the traffic is primarily bursty, but is of
`relatively modest volume for an organization, then a public packet-switched
`network provides the best solution. A public packet-switched network works much
`like a public telephone network. In this case, the network provides a packet transmis—
`sion service to a variety of subscribers, each of which has moderate traffic require-
`ments. If there are a number of different subscribers, then the total traflic should be
`great enough to result in high utilization. Hence, the public network is cost—effective
`
`
`
`Ericsson Exhibit 1041
`Ericsson v.
`|V1, |PR2018—00727
`Page 18
`
`Ericsson Exhibit 1041
`Ericsson v. IV1, IPR2018-00727
`Page 18
`
`

`

`3-4 Application of Pocket Switching
`
`77
`
`BOX 3-3
`
`PACKET SWITCHING
`
`
`APPLICA TIONS
`
`Data
`
`Public Data Network (PDN)/Value—Added Network (VAN)
`
`Provide a wide-area data communications facility for computers and
`terminals. The network is a shared resource, owned by a provider who
`sells the capacity to others. Thus it functions as a utility service for a
`number of subscriber communities