Frame Relay - for Faster and More Efficient Data Communications ...

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ERICSSON REVIEWBO HEDFORSPublisher 1992-GOSTA LINDBERGPublisher 1979-1991EDITORIAL CHANGESOn March 1, 1992, Gosta Lindberg andGoran Norrman retired from their respectiveposts as publisher and editor of EricssonReview. The new publisher is Bo Hedfors,senior vice president in TelefonaktiebolagetL M Ericsson and Director of CorporateSystems and Technology. Per-OlofThyselius has been appointed as the neweditor.Gosta Lindberg succeeded Dr ChristianJacobaeus as publisher of Ericsson Reviewin 1979, following his appointment asTechnical Director of TelefonaktiebolagetL M Ericsson. Gosta Lindberg has takenan active part in making Ericsson Reviewan objective and informative technical journaland has been a valuable support to thesuccessive editors during his 13 years aspublisher.Goran Norrman leaves his position as editorof Ericsson Review with this issue.When he succeeded Gosta Neovius, in1986, he had a long and successful serviceto the company behind him. His broadtechnical knowledge and interest intechnology has been very valuable in hiseditorial work, which has been much appreciatedby the publisher and management,and not least by the readers.From the editor's deskThis, the first issue of Ericsson Review aftermy appointment as editor, is also thefirst issue to be published in English only.Subscribers who have previously receivedthe French, Spanish or Swedish editionswill from now on receive only the Englishedition. When the Board of Ericsson Reviewrecently decided to stop publishing thenon-English editions, their prime motivewas the awkward delay between the firstand last editions - even considering thatEricsson Review has never had the ambitionto be a technical news magazine.Another basis for the decision was, of cource,our firm belief that the majority of ourFrench, Spanish and Swedish readers arefamiliar with English.Ericsson Review was first published in1923, and as early as 1924 it became afive-language magazine. Since the discontinuanceof the German edition, it hasbeen issued in four languages. The ambitionfrom the start was to publish a technicalmagazine to spread knowledge ofEricsson products and Ericsson technologyto our customers' technical staffs andto the technical staffs within our own worldwideorganisation. This objective has neverbeen changed. The major content ofEricsson Review has always been descriptionsof our different systems and productsand outlines of our technical objectives.Occasionally, the magazine has also containednews from Ericsson's business operations,large telecom exhibitions andconferences.Scientific material from our applied researchactivities had once an exclusiveoutlet in the form of Ericsson Technics.This magazine was integrated with EricssonReview in 1978. Unfortunately, it turnedout that scientific material met with difficultiesin competing for space in EricssonReview. The readers are the only oneswho can change this situation, and we willcertainly appreciate it if they inform us oftheir views on Ericsson Review and itscontents.During my 38 years of working with differentparts of Ericsson, I have myself beena regular reader of Ericsson Review. Takingoffice as editor I will do my best tocreate a readable and informative magazinein the years to come.GORAN NORRMANEditor 1986-1991To avoid the situation of our English readersreceiving the first issue of Ericsson Review1992 prior to the last 1991 issue, wehave chosen to publish a double-issue:1-2, 1992.PER-OLOF THYSELIUSEditor 1992-ERICSSON REVIEW No. 1-2, 1992
Frame Relay - for Faster and MoreEfficient Data CommunicationsKajsa LundfallKAJSA LUNDFALLEricsson Business CommunicationsToday, workstations and personal computers have become everyday tools. This fachas radically changed the conditions for data communications networking. Theprocessing power has moved from computer centres to users' desks. Thecommunications pattern is also different: it is no longer a matter of exchangingtransactions of the question/answer type, but of transferring large volumes of data inthe form of "bursts". At the same time, technological improvements in the transportnetworks have resulted in better data transmission quality. This, in turn, reduces theneed for error-correcting functions in the communication protocols; instead, effortsfocus on the ever-growing need for higher transmission speed. Efficient handling ofthe new situation requires new protocols and new communications systems.The author describes the way technological advances and a growing market demandcontribute to the development of new communications protocols such as FrameRelay. The article compares Frame Relay to packet switching (X.25) and describeshow Frame Relay works.data communication systemscomputer networkspacket switchingprotocolsFig. 1Traditional centralised multi-user systemThe environment is primarily designed for moderatetransmission speedIn the last few years we have been witnessinghow developments in the data processingand data communication fieldshave changed the use of computers inmany companies. Due to the low cost ofpersonal computers and workstations,practically every desk is equipped withthese tools today. The typical informationsystem is no longer a centralised multiusersystem, but a decentralised systemmade up of interacting Local Area Networks(LAN). These inter-networks (composedof various LANs) place new demandson the Wide Area Networks (WAN).Centralised systemsThe core of a typical transaction-orientedsystem is a central host computer whichserves a large number of terminal usersconnected via concentrators and communicationprocessors, Fig. 1. All exchangeof information between a terminal and itsenvironment takes place via the host computer,which also accommodates all processingpower. Most of today's applicationsand communication networks havebeen designed for operation in this environment.The typical transaction is a text string (aquestion) which is sent to the host computer,and a full screen (an answer) which issent from the host computer to the terminal.Very little graphics - if any at all - isused, and the amount of information transferredis small. Moderate transmissionspeed can be used, even when the requirementsfor short response time are stringent.Distributed systemsThe present development in computertechnology is creating a new computer environment- based on Local Area Networksand distributed, interacting applications- which supplements the traditionalhost computer configuration. LANs usesimple protocols and provide high transmissionspeed for data communicationsover short distances. Gone is the centralisedarrangement, with a master-slave relationshipbetween computer and terminal,in which all information must pass througha mainframe.Local Area Networks and personal computershave developed along parallel lines.ERICSSON REVIEW No. 1-2, 1992
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Page 6 and 7: 4Fig. 2Distributed computer environ
Page 8 and 9: Fig. 7A company's data network shou
Page 10 and 11: 8Fig. 11The frame format used for F
Page 12 and 13: 10er (DE, Fig. 12) should be set to
Page 14 and 15: Computerised System for QualityInsp
Page 16 and 17: Box 1Code39, the first alphanumeric
Page 18 and 19: 16Fig. 6Cable attenuation test at E
Page 20 and 21: 18Fig. 9Installing the Dehlfi syste
Page 22 and 23: Human Factors - A Key to ImprovedQu
Page 24 and 25: 221 Use the user's model2 Introduce
Page 26 and 27: 24Fig. 5Advanced Human Factors desi
Page 28 and 29: Fig. 7User interface for PBX attend
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Page 32 and 33: 30Box1CELL-VOLTAGE EQUALISER BMP 16
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Page 36 and 37: In Search of Managed ObjectsWalter
Page 38 and 39: Fig. 4The telecommunication network
Page 40 and 41: Fig. 6Functional Model illustrating
Page 42 and 43: 40Fig. 9Combination of layering and
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54Table 5Cross-connect functions, R
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Fig. 32, leftCross-connect Fragment
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