AT T Network Architecture Evolution
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This document discusses the evolution of AT&T's network architecture to meet future needs. Key points: - AT&T aims to provide a lowest-cost, feature-rich network globally to maintain core businesses, expand data networking, and grow internationally. - Digitalization, distributed intelligence, and advanced technologies like ISDN will be implemented. This will allow new services like enhanced private networks, domestic services globally, and data capabilities for customer management. - The network architecture objectives are a high-quality, feature-rich network; low-cost core network; end-to-end data capability; and globalized services. Digital switching, signaling, ISDN deployment, and extended data networking will achieve these objectives
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competitive challenges, and corporate objectives for 1986
to 1995. The essence is to ensurethatits 1995 network is
intelligent, software driven, and digital---enabling AT&T to
adapt rapidly to customer needs.
Theplanning horizon hasalso beenexpanded
beyond 1995. Aswe determine the technology and archi-
tecturethatlead to the network ofthe 1990s, we further
envision a graceful evolution to the network ofthe twenty-
firstcentury.
Acknowledgments
The combined effort ofmany people within AT&T
was required to produce thiscomprehensive AT&T net-
work architecture. The authors want to acknowledge the
members ofseveral organizations:
- AtAT&T, the End-to-End Network Architecture Plan-
ning Division and the Networking and Services
Architecture Division under Ron Angner and Marda
Higdon.
- AtAT&T Bell Laboratories, the Network Interface Plan-
ning Department under James Mansell, and the
Advanced Services andArchitecture Planning Depart-
mentunder Rich Adleman.
References
1. A. E Bulfer, "AT&T's Pay-per-View Television Trial," AT&TTech-
nicaljournal, Vol. 66, No.3, Mayl]une 1987, pp. 54-63.
2. M. R. Braunstein, C. L. Burton, andS. D. McNabb, "ASQIC 800
Call DataMaster," AT&TTechnical joumai, Vol. 66, No.3, May/
June 1987, pp. 21-31.
3. J. E. Rogalski, "Evolution of Gigabit Lightwave Transmission Sys-
tems," AT&TTechnical journal, Vol. 66, No.3, May/June 1987,
pp.32-40.
4. IntegratedServicesDigital Network, AT&TTechnicalJournal,
Vol. 65, No.1, january/February 1986, pp. 4-55.
5. E.]. Obuchowski, "Access ChargeandRevenue Architecture,"
AT&TTecnnical Ioumal, Vol. 66, No.3, May/June 1987, pp. 73-
81.
6. H. S. Hinton, "Photonic Switching Technology Applications,"
AT&TTechnical journal, Vol. 66, No.3, Mayl]une 1987, pp. 41-
53.
7. J.]' Lawserand P. L. Oxley, "Common Channel Signaling Net-
workEvolution," AT&TTechnical journal, Vol. 66, No.3, May/
June1987, pp. 13-20.
8. R. Merski andD. M. Parrish, "Operations SystemsTechnology
forNew AT&T Network andServicesCapabilities," AT&TTech-
nicaljournal, Vol. 66, No.3, Mayl]une 1987, pp. 64-72.
Biographies (continued)
long-range architecture planning for AT&T Network Operations
Group's stored program control network. He joined the com-
pany in 1980 and has a B.S. in mathematics from Greenville
College, and an M.S. in mathematics and Ph.D. in applied
mathematics, both from Iowa State University.
(Manuscript receivedjanuary 19, 1987)
MAY/JUNE 1987·VOWME66' ISSUE 3
AT&T TECHNICAL JOURNAL](https://image.slidesharecdn.com/attnetworkarchitectureevolution-230804173223-440621b2/85/AT-T-Network-Architecture-Evolution-11-320.jpg)
AT T Network Architecture Evolution
- 1. AT&T TECHNICAL JOURNAL ATleT NETWORK ARCHITECTURE EVOLUTION Janis L. Cummings, Kevin R. Hickey, and Beth D. Kinney _ 2 Janis L. Cummings is in the AT&T Network Operations Group in Bedminster, NewJer- sey, and Kevin R. Hkkey is with AT&T Bell Laboratories in Holmdel, NewJersey. Beth D. Kinney was formerly a manager in the Network Opera- tions Group. Ms. Cummings, district manager of Network Architecture Evolution, is responsible for pro- viding long-range network and end-to- end architectures and for forward-looking work that assesses emerging technologies for possible future network application. She joined the com- pany in 1967, and has a B.S. in mathematics from Carnegie-Mellon University and M.S. degrees in mathemat- ics/computer science and electrical engi- neering from Stevens Institute of Technol- ogy. Mr. Hickey, a supervisor in the SPC Network Interface Planning Department, is responsible for (continued on page 12) The network ofthe future will use technologies and architectures that meet the telecommunications needs ofourcustomers. These customer needs are embodied inthree AT&T corporate goals: maintain and strengthen the core businesses, expand the focus on data networking, and establish a major position ininter- national markets. To address these goals, AT&T will provide a network that is lowest incost and rich infea- tures and functionality. Key elements inthe network evolution are anaggressive plan for digitalization, implementation ofdistributed network intelligence, and deployment ofadvanced technologies. These key ele- ments allow AT&T to expand its existing services and introduce new services including: data capabilities ori- ented toward customer network management; modernized private networks such as EPSCS; domes- ticservices offered globally; ISDN; and enhanced services. The plans for the AT&T network extend to the year 2000 and beyond to ensureAT&T's leadership position. Perspective Our society is moving toward an information-intensive cul- ture built around the exchange of information. Telecommunications technology is evolving rapidly, with computing capabilities becoming widely distributed in the home, office, and factory. Information is being exchanged between humans, between humans and machines, and between machines. This information exchange is a necessity between a wide range of locations, induding the home, businesses, and factories, both domestically and internationally. These factors have initiated the formation of an information movement and man- agement (IM&M) industry.
- 2. IM&M customers have a diverse spectrum of needs. Large business customers are looking for the most technologically advanced telecommunications network available. Key requirements include a feature-rich network thatprovides rapid deployment ofthesefeatures, along with high quality and flexibility. Robust interfaces between the network and customer premises equipment (CPE), smaller locations, and international locations are critical. Although smaller business and residential customers also want anincreasing set offeatures that provide high-quality solutions to meet theirneeds, theirfinancial decision cri- teriaare different from large businesses. (Inthisissue, Bulfer describes the trial ofAT&T's Pay-per-View Ser- vice.'anadvanced service.) Customers also needservices that provide infor- mation storage and processing inthe marketplace. Soon, the capability will existto perform advanced information processing transactions, such as the shopping scenario in Panell. This will createa needfor AT&T's customers- business, industry, or consumer-to have information man- agement that encompasses the generation, collection, storage, processing, and transfer ofinformation thatorigi- nates from a variety ofmedia (voice, data, and image). Asindicated above, AT&T's customers have a rap- idly evolving, everincreasing needfor IM&M capabilities. Thecompetitive and regulatory context inwhich AT&T must respond to thesecustomer needs isalso evolving. Historically, AT&T hasbeenthe clear technological and service leader inthe telecommunications field. Since divestiture, competition hasgrown rapidly. AT&T faces strong competitive challenges from several interexchange carriers who continue to invest heavily to upgrade their networks. Thesecompetitive challenges will make it increasingly important forAT&T's network to provide advanced features and high functionality end-to-end solu- tions quickly and effectively, inresponse to customer needs for voice, data, and image handling. One step that we are taking to allow rapid implementation ofnew service concepts is the ASQIC (Advanced Services Quick Imple- mentation Capability) program thatBraunstein, Burton, Alpha Corp. Bank Co. InternationaI Corp. Panel 1. Future shopping scenario Scenario: Customerpurchases anitemfrom Alpha Corp. 1. Customer telephones Alpha Corp..andselectsSales Department at the.automated prompt. 2.• Customer looks through the on-line catalog and selectsanitem. 3. Alpha Corp. prices theitemandprompts forthe paymentmethod. 4. Alpha Corp. alsochecks inventory onthe item, finds it is low; andelectronically notifies itsJapa- neseplant, International Corp., toproduce and ship more. 5.. Customer requests electronic transfer offunds from Bank Co. 6. Alpha Corp. andBank Co. determine authorization inrealtime. 7. Customer gives hisor her authorization code inreal time, Alpha Corp. accepts payment, and customer disconnects. and McNabb describe- inthisissue. Regulatory requirements have constrained AT&T's ability to meetthe full range ofcustomer needs, particu- larly inthe areaofprotocol processing and enhanced services. However, the regulatory environment has 3
- 3. 4 changed dramatically with the Federal Communications Commission's (FCC) ruling on Computer Inquiry IIIand protocol processing. Although regulatory requirements still existinthese areas, AT&T will be allowed more flexibility to provide enhanced services andprotocol processing that meetcustomer needs. NetworkArchitecture Objectives To design the future AT&T network architecture, we have developed objectives (Panel 2)thatincorporate anticipated customer needsand the effects ofgrowing competition and continuing regulatory constraints. Specifi- cally, ourprimary architectural objectives are: • Provide a high-quality, feature-rich network thatallows rapid deployment ofnew features. • Maintain a low-unit-cost corenetwork with diverse access andservice options. • Develop anend-to-end datacapability tomeet increasing customer expectations and enable AT&T to remain a leading competitor inthe IM&M marketplace. • Globalize AT&T services to satisfy the needs ofmultina- tional customers. AT&T will continue to provide a flexible, cost- effective network to link customers' computing and com- munications technologies andefficiently handle their information. For thisnetwork, AT&T will use the following strategies: • Rely onstandards that define common protocols and physical interfaces to allow computing and communica- tions technologies to interact easily. • Provide all the capacity customers desire, while allowing customers to tailor the network to theirspecial needs. • Use fault tolerant systems that recover rapidly from fail- ureswhen they occur. • Make full use ofnew technology to provide new applica- tions to customers. Key Architectural Strategies To ensurethat AT&T's network continues to meet evolving customer needsand achieves its architecture Panel 2. ATBeT Objectives - High-quality, feature-rich network - Low-unit-cost corenetwork - Development ofanend-to-end data capability - Globization ofthe AT&T network objectives, wehave defined a target architecture forthe 1995 timeframe thatcomprises the following key elements. Evolution ofthe AT&T switching, signaling, and transmission network elements mustcontinue. AT&T is deploying digital facilities, CCS7 (aversion ofcommon channel signaling, CCS), and common software and hard- ware inthis signaling andtransportnetwork. This evolution will allow integration ofservices andcapabilities across the network that will provide a cohesive set ofser- vices with the flexibility andfunctionality that AT&T's customers require. Thiscontinuing evolution supports the objectives ofmaintaining a low-unit-cost corenetwork and developing a feature-rich network. Anationwide, followed byaninternational, Inte- gratedServices Digital Network (ISDN) will be deployed. The new network capabilities that are inherent inthe ISDN architecture support the maintenance ofa low-cost core network, evolution ofa feature-rich network, and globali- zation ofservices. ISDN will be designed to support evolving customer needs formore sophisticated services. Inaddition, it will provide anintegrated network-access capability to support integration ofservices inthe net- work. The timely introduction ofISDN, at both a domestic and international level, will help AT&T maintain technolog- icalleadership. AT&T's data networking capability will be extended to include a more comprehensive set ofend-to- enddata features andfunctions. This will support AT&T's objective ofbeing anend-to-end service provider and a leading competitor inthe IM&M industry.
- 4. International network AT&T switched network • ISDN • SON • NodaI services Private switched network • EPSCS ｃｃｓｾｾ• Signaling lAD LATA C 4 Signaling The existing international network architecture will be expanded to facilitate introducing advanced services to meet the needsofmultinational customers. Thecurrent international deployment ofdigital facilities andadvanced signaling will have a strongeffect onthisarchitecture. This strategysupports the objective ofglobalization ofAT&T's network services. Figure 1. Current (1987) AT&T network. CCITI6 = a provision of standards set byInternational Telegraph andTelephone Consultative Committee; CCS = common channel signaling; EPSCS = Enhanced Private Switched Communications Ser- vice; lAD = Integrated accessdistributor; ISDN = Integrated services digital network; LATA = localaccesstransport area; SDN = software defined network. 5 Architectural Evolution Today, AT&T's network architecture consists of several independent, service-oriented networks. Asthe architecture evolves through 1995, these networks will be integrated, onbotha capabilities andservices level. Figure 1 shows AT&T's currentarchitecture, while Figure 2 shows the architecture planned for1995. The subsections that follow describe thisevolution forthe 1987 to 1995 timeframe. Later sections describe the network's technical direction beyond 1995. Facility Evolution. AT&T plans to provide more digital connectivity and capability. AT&T has embarked onan aggressive digital deployment strategythat is rapidly increasing the percent- age ofdigital circuit miles inits facility network. Eventually, mostofAT&T's facility network will be digital. The purpose ofthisaggressive plan is to reduce costand increase functionality, design a network thatwill provide ISDN data capabilities, and give increasing support to customer control andvertical services. AT&T intends to provide as much intelligence, flexibility, andfunctionality in the network as possible. (Rogalski discusses the facility network plans inhispaperonlightwave transmission systems.3) Access. AT&T will provide a full-featured ISDN capability to serve both large and small customer locations. ISDN-as a network capability andas aninte- grated-access alternative to transport voice, data, or image traffic-will be offered using out-of-band signaling. Evolution ofthe signaling network will enable AT&T to introduce ISDN capabilities' inphases starting in1987
- 5. PRJ AT&T ESC International network PRI AT&T switched network • ISDN • SON • Nodal services • Privateswitched network -ESPCS lAD LATA ', ....• Signaling ESP 6 Figure 2. 1995 AT&T network. CCS = common channel sig- naling; CPE =customer premises equipment; EPSCS = Enhanced Private Switched Communications Service; ESC = enhanced services complex; ESP = enhanced services pro- vider; lAD =Integrated access distributor; LATA =local access transport area. using a primary rate interface (PRI), with 23or more B channels andone D channel (Figure 3). Among the supported ISDN features will be: - Identification ofthe originating station - Call-by-call switched service selection - Switched digital capability at 64kb/s - User-to-user information. Interworking with the local exchange carrier's2B + D basic rate interface (BRI) andprimary rate interface (PRI) offerings is being planned. Since divestiture, the management ofaccess has beena major new activity forAT&T. Asystems architec- ture hasbeendeveloped to provide anefficient way to manage access costs, andis described inObuchowski's paper onaccess charge andrevenue architecture.5 SPC Network. AT&T will use several techniques in the evolution ofits storedprogram controlled (SPC) network. Advanced technologies. AT&T will extend the capa- bility ofits switched network through the strategic use of advanced technologies. Inthe ASN, wewill continue to use the 4ESSTM switching system as the high-functionality switch for domestic andinternational switching center (ISC) func- tions throughout the early 1990s. To provide a more flexible, lower costASN, weare considering the use of wideband-packet technology to provide integrated trans- portand switching ina common packet form fora variety ofvoice, data, andimage applications. Wideband-packet technology may eventually serve as anintegration vehicle forthe ASN and AT&T-provided, dedicated private-line subnetworks. The goal ofsuchintegration is increased effectiveness through universal provisioning and mainte- nance procedures, regardless ofthe services involved. Anew, high-functionality switching system that useselectronic and, possibly, photonic technologies is under studyforthe mid-1990s. (Inthisissue, Hinton dis- cusses applications ofthe photonic technology-l Besides the usual narrowband circuit capability, the advanced
- 6. Data Control 238 + 0 OS1 lAD 4ESS switch Figure 3. AT&T ISDN primary rate interface has 23 B channels and 1 D channel; the DS1 rate is 1.544 Mbls. CCS7 =com- mon channel sig- naling, version 7; DSTC =digital serving test center; lAD = integrated access distributor; ISDN = integrated services digital network. switching technology could support wideband circuit and packet switching. Application ofthisswitch inthe network could provide voice, data, and image transfer, as well as facility restoration and rearrangements. Enhanced CCS network. AT&T will enhance the common channel signaling network to provide the basis for distributed network intelligence and new service features. In the AT&T network, common channel signaling isevolving from CCS6 to CCS7, a message-oriented proto- col thatis a variant ofCCITT7. (This isa provision ofthe International Telegraph and Telephone Consultative Com- mittee.) AT&T plans to introduce CCS7 thisyear. Introduction ofthe No. 2 Signal Transfer Point (2STP); increased capacity ofhigh-speed, 56-kb/s digital signaling links; and out-of-band signaling using CCS7 all combine to facilitate a rich set ofnew services. This more robust, digital signaling network is the foundation for new services with sophisticated fea- tures that require message-oriented signaling protocols to transport special customer messages. In addition to improvements to the internal AT&T signaling network, network interconnection links with local exchange carrier networks and foreign countries are also planned for the 1990 period. This new signaling architecture, which Lawser and Oxley discuss in their paper about the CCS7 network," will also facilitate distributed processmg. Distributed intelligence. AT&T will use distributed intelligence to provide sophisticated features and functionality. Over theplanning period, thetrendtoward distrib- uting service-control logic (which isthefeature set required tosupport service capabilities) will continue. By introducing advanced technology and deploying common software and hardware invarious network elements, AT&T can strategi- cally and selectively locate theservice-control logic to increase thenetwork's flexibility and functionality. An exam- ple ofthisistheability todeploy processing nodes ona variety ofnetwork elements tosupport database and signal- ingapplications. With such processing nodes available, itis easiertodeploy service-control logic inanoptimal network arrangement. Inaddition, distributing theservice-control logic this way will extend thecapacity ofnetwork elements thatcurrently provide AT&T direct-services-dialing- capability (DSDC) services. 7
- 7. 8 Figure 4. Private net- workevolution; EPSCS (Enhanced Pri- vate Switched Communications Ser- vice)will be modemlzed and Inte- grated with an AT&T switched offering. CP =customer prem- Ises; DNHR = dynamic nonhlerarchl- cal routing; NCP = network control point; PLIMT = private line Intermachlne trunks; PNI = private network Interface; PRI = pri- maryrate Interface. - - - Signaling CP CP Routing and numbering plan. AT&T will develop a comprehensive and robust routing and numbering plan to meetthe needs ofadvanced services into the twenty-first century. Thefuture's routing and numbering plans must satisfy customer needs, as well as technological and legal or regulatory forces overthe planning period. Because net- work architectures are moving toward integrated services and capabilities, we are studying a class ofservice-routing capability as a way to accommodate the routing ofvarious services and types oftraffic inanintegrated architecture environment. Arelated architectural direction is the expansion ofnumbering plans. This will accommodate the large trunk-group requirements ofthe next-generation intercon- nection system and give customers flexibility inthe design ofinternal numbering plans. Modernized private networks. AT&T will modernize private switched networks to meetincreasing customer expectations and give customers ofsuch networks a path- way to ISDN. To do this, we will integrate private- switched-network functionality with the AT&T switched network. To meetcustomer needs foradvanced technolo- gies, AT&T will use the digital technology ofthe 5ESS™ switch-beginning in1988-to modernize the Enhanced Private Switched Communications Service (EPSCS) net- work. To provide a pathway to ISDN for the EPSCS customer, we will integrate the modernized EPSCS and an AT&T switched-network offering. As Figure 4 shows, the private network interface (PNI) allows the customer to obtain both ASN capabilities and modernized EPSCS capabilities. Full feature transparency, which is a complemen- taryfeature set among switches inthe integrated network, will provide the service capability ofthis AT&T switched
- 8. offering that combines the virtual private-network capabil- ityofthe software defined network (SDN) with EPSCS- like features. Ahybrid 4ESS/5ESS switch network will provide the initial functionality. Thisis aninterim step toward integrating the architectures ofthe AT&T switched network and the private switched network. Data Networking. AT&T will develop data networking capabilities that are comparable to the existing feature-rich voice capabilities. Architectural efforts are focusing ongiving AT&T customers end-to-end data networking capabilities. The capabilities planned inthisarchitecture will provide anend- user data networking AT&T service thatfocuses onlow latency, statistical multiplexing, routing, customer network management, and operations capabilities. Thisarchitecture will offer AT&T customers anend-to-end intelligent data capability ona flexible network, inaddition to the digital- transport-based services that are currently offered. International. AT&T will extend domestic capabili- tiesto the international arena. The need forglobal service architectures is increasing. To meet this need, AT&T will seekfeature transparency ofadvanced services capabilities across national boundaries to provide forthe evolving needs ofthe multinational information movement andmanagement mar- ketplace. Akey feature ofthisglobal architecture is the introduction ofinternational digital facilities (e.g., the TAT-8transatlantic andHAW-4/TPC-3 transpacific cables shown inFigure 5), as well as the international introduc- tion ofCCITT7-based signaling protocols. Support Systems. AT&T will continue to evolve its workcenter and operations system (aS) architectures to ensure continued support forits strategic objectives. To support theseobjectives andaccommodate changes intechnology, weexpectworkcenter andas architectures to change significantly over the nextdecade. Customers will be provided with a single contact to meet theirservice-related needs. We are also integrating plans for network and CPE workcenters to provide end-to-end coordination ofworkcenter functions. Over the nextdecade, the general trendsinas architecture will be: - Become UNIX® system based. - Use more graphics workstations. - Employ distributed processing techniques. - Introduce the use ofartificial intelligence. In thisissue, Merski andParrish discuss an advanced operations system.8 Enhanced Services. AT&T will develop architectures forenhanced services thatinvolve the processing and stor- ageofinformation to meet customer needs. Enhanced services, which are subject to varying degrees ofregulation, will be offered overthe planning period. Because AT&T is subject to Computer Inquiry Ill's requirements forcomparably efficient interconnection (CEI) and open network architecture (aNA), the enhanced services architecture will be external to the network ele- mentsthatprovide basic services. The equipment to provide enhanced services will connect to the network via basic, tariffed interfaces. If, inthe future, the FCC grantsrelief from CEI and aNA, a network-based enhanced services architecture could be usedwhen appropriate. Anew network element, called anEnhanced Network Services Complex, is being studied as part ofthe enhanced services architecture. Such a network element could provide storage andfor- warding ofvoice and datamessages, attendant-based product information, speech response, andentertainment services. This complex would have processors, voice rec- ognition and synthesizing, announcement, storage, and otherappropriate equipment. Future Directions Aswe extend the planning horizon beyond 1995, new technology trends emerge. During thisperiod, cus- tomers will continue to require increasingly complex features and functions. To ensureAT&T's competitive position inthe future, its network architecture must con- tinue to meet long-term evolving customer needs while capitalizing ontechnological advances that occur inthe 9
- 9. 10 -HAW-4 ........ TPC-3 - TAT-8 Figure 5. Digital connectivity In the Atlantic and Pacific ba- sins using the TAT-S and HAW-4/TPC-3 undersea cable systems. period. The work ofdefining this architecture beyond 1995 is underactive research, using assumptions about technol- ogytrends andcustomerneeds, combined with assumptions about the corporate, competitive, andregula- tory environment. Technology Trends. As noted above, the long-term needs ofAT&T's customers, modulated bythe effect of regulatory constraints, will set the direction ofAT&T's network architecture. Akeyelementofthe architecture is the technology that will be available to meet customer needs. The new technologies andcapabilities that they offer will have a significant effect onthe future architec- ture. Significant advancements are expectedinthree areas: fiber, switching, andprocessing andstoragetech- nology. The key technological trends andtheir effect on the architecture are summarized below. Fiber. Long-haul fiber facilities from 1.7 Gb/s to at June1986 TAT-8 least 10Gb/s will be available. Fiberis the facility of choice forthe future. Butwherefiber is notpractical or economical, digital radio systemswill continue to be used inthe AT&T network. The percentage ofcoaxial cable in the network will be decreasing. The trend is fortransmission costs to continue to drop rapidly, so high-capacity transport will be available at relatively low costs. Asa result, AT&T's customers should begin to desire higher bandwidth services. Thiswill clearly affect the hierarchy oftransmission rates andthe cross- connect andswitching rates that the network supports. Inaddition, a large fiber deployment will make it necessary forthe network to supportrapid restoration capabilities incaseswherefibers are cut. Switching. Forswitching systems, improved elec- tronic nonblocking switching fabrics will be available. Purely photonic switching systems (photonic switching driven byphotonic control) are notexpected to be available forcommercial use before the year2000. Butelectroni- cally controlled optical systemsmay be available inthe late 1990s. Switching systemsare expected to perform
- 10. switching and cross-cormect functions to support the high- bandwidth circuit and packet traffic that customers gener- ate. Photonic cross-cormects are expected to be usedto handle facility restoration. (Hinton's paper onwideband switching' discusses optical switching and related technologies. ) Processing and storage. Processing and storage tech- nology to support basic and enhanced services will also advance. The scale and complexity ofintegrated circuit devices will continue to increase, butthe physical volume required to store datawill decrease (especially with the development ofoptical disk storage). Inaddition, high- speed processors forcommercial usewill reach 100 to 1000 million instructions per second. Assoftware-development techniques advance, software productivity will also improve (though lessrap- idly). Overall software costs (including testing and maintenance) will continue to increase, indicating the cost benefits ofusing special-purpose hardware. During this period, advancements will be made inthe development of expertsystems, object-oriented languages, and artificial intelligence. Advances inprocessing and software technology will dictate the control structureforfuture network ele- ments. Most likely, the various fabrics will be controlled by high-capacity processors thatruncomponent-based soft- ware ina distributed-processing environment. Modular hardware and software that is easily modified and growable isseenas onekey to AT&T's ability to respond rapidly to changing customer needs. Preliminary AT&T Architecture Beyond 1995. TheAT&T network beyond 1995 is envisioned to consist ofmodular network elements aimed at providing a highly flexible and intelligent network thatmeets customer needsfor end-to- endservice ina cost-effective way. Thisnetwork will pro- vide customers with increased capabilities to control their telecommunications services. Hardware and software modularity will simplify the introduction ofnew network elements and services. Integration ofthe various special- purpose networks will result inreduced operations costs and increased flexibility to meetcustomer needs with high- quality services. TheAT&T network will have access and egress points to local exchange carriers, foreign administrations, enhanced service providers, and customer premises equip- ment. Attheseaccess and egresspoints, the network will support standard interfaces for packet data, narrowband circuits (1.5 Mb/s and below), and wideband circuits (45 Mb/s and above). Ultimately, intercormect vehicles that integrate the control ofvarious fabrics will provide the wide range ofswitching, cross-cormect, and selected mul- tiplex functions thatcustomers will require from the network. Inaddition, the intercormect vehicles will handle restoration and rearrangement ofthe high-bandwidth facili- ties, caring for the various transmission rate traffic types. The network will also support specialized data- base functions thatwill give the customer increased customization capabilities. In thisperiod, the signaling protocol used will focus onpermitting more advanced user-to-user and user- to-network capabilities. It will also take advantage ofthe characteristics offiber transmission facilities to allow increased signaling rate and better error performance. Thenetwork will contain customer interfaces that will interpretcustomer-controlled input and provide that input to the relevant service operations systems. The ser- vice operations systems will thentranslate the input into actions inthe network. Correspondingly, the customer will receive data from the customer interfaces via the service operations center. Thearchitecture for AT&T's network beyond 1995 isintended to provide a targetforthe on-going AT&T net- work evolution. It should guide thatevolution to ensure thatnew technology is developed and deployed optimally to meetcustomer needs for end-to-end basic and enhanced services. Conclusion AT&T's network architecture embodies the direc- tions and changes plarmed inresponse to customer needs, 11
- 11. 12 competitive challenges, and corporate objectives for 1986 to 1995. The essence is to ensurethatits 1995 network is intelligent, software driven, and digital---enabling AT&T to adapt rapidly to customer needs. Theplanning horizon hasalso beenexpanded beyond 1995. Aswe determine the technology and archi- tecturethatlead to the network ofthe 1990s, we further envision a graceful evolution to the network ofthe twenty- firstcentury. Acknowledgments The combined effort ofmany people within AT&T was required to produce thiscomprehensive AT&T net- work architecture. The authors want to acknowledge the members ofseveral organizations: - AtAT&T, the End-to-End Network Architecture Plan- ning Division and the Networking and Services Architecture Division under Ron Angner and Marda Higdon. - AtAT&T Bell Laboratories, the Network Interface Plan- ning Department under James Mansell, and the Advanced Services andArchitecture Planning Depart- mentunder Rich Adleman. References 1. A. E Bulfer, "AT&T's Pay-per-View Television Trial," AT&TTech- nicaljournal, Vol. 66, No.3, Mayl]une 1987, pp. 54-63. 2. M. R. Braunstein, C. L. Burton, andS. D. McNabb, "ASQIC 800 Call DataMaster," AT&TTechnical joumai, Vol. 66, No.3, May/ June 1987, pp. 21-31. 3. J. E. Rogalski, "Evolution of Gigabit Lightwave Transmission Sys- tems," AT&TTechnical journal, Vol. 66, No.3, May/June 1987, pp.32-40. 4. IntegratedServicesDigital Network, AT&TTechnicalJournal, Vol. 65, No.1, january/February 1986, pp. 4-55. 5. E.]. Obuchowski, "Access ChargeandRevenue Architecture," AT&TTecnnical Ioumal, Vol. 66, No.3, May/June 1987, pp. 73- 81. 6. H. S. Hinton, "Photonic Switching Technology Applications," AT&TTechnical journal, Vol. 66, No.3, Mayl]une 1987, pp. 41- 53. 7. J.]' Lawserand P. L. Oxley, "Common Channel Signaling Net- workEvolution," AT&TTechnical journal, Vol. 66, No.3, May/ June1987, pp. 13-20. 8. R. Merski andD. M. Parrish, "Operations SystemsTechnology forNew AT&T Network andServicesCapabilities," AT&TTech- nicaljournal, Vol. 66, No.3, Mayl]une 1987, pp. 64-72. Biographies (continued) long-range architecture planning for AT&T Network Operations Group's stored program control network. He joined the com- pany in 1980 and has a B.S. in mathematics from Greenville College, and an M.S. in mathematics and Ph.D. in applied mathematics, both from Iowa State University. (Manuscript receivedjanuary 19, 1987) MAY/JUNE 1987·VOWME66' ISSUE 3 AT&T TECHNICAL JOURNAL