Converged Networks Case Studies · Converged Networks Case Studies Converged networking is an emerging technology thrust that integrates voice, video, and data traf-fic on a single

Converged Networks

T e c h n i c a l P a p e r

Case Studies

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Converged NetworksCase Studies

Contents

Overview of Converged Networks 2

What Is Driving Converged Networks? 3

Cost Reduction 4

Emerging Technologies 5

Greater Flexibility and Functionality 5

Standards 6

Converged Network Architecture 6

Case Studies 7

Case 1: Converged Network Support for Call Centers 7

Phase 1: Single Call Center on a Dedicated LAN 8

Phase 2: Two Call Centers on Dedicated LANs, Interconnected by the PSTN 9

Phase 3: Multiple Call Centers on Dedicated LANs, Interconnected by a WAN 10

Phase 4: Multiple Call Centers on Dedicated LANs, Interconnected by a WAN, with Customer Access over the Internet 11

Phase 5: Multiple Call Centers on Multi-Application LANs, Connected by a WAN, with Customer Access over the Internet 12

Case 2: Converged Network Support for Financial Transaction Applications 14

Phase 1: Data Only 15

Phase 2: Voice and Data on Business-Critical Networks 16

Phase 3: Voice, Video, and Data on Business-Critical Networks with Multiple Data Centers 17

Case 3: Converged Network Support for the Virtual Classroom and Corporate Training 18

Phase 1: Small Number of Dedicated LANs with an ATM Campus Backbone Supporting ELANs 18

Phase 2: Larger Number of Dedicated LANs with a Packet Switched Backbone 19

Phase 3: Multi-Application LANs with a Packet Switched Backbone and Supporting Video Return 20

Phase 4: Multiple Campuses Interconnected by a WAN 22

Phase 5: Multiple Campuses and Remote Home Sites Interconnected by a WAN 23

Case 4: Converged Network Support for Toll Reduction 25

Phase 1: Toll Reduction over Existing PSTN 26

Phase 2: Toll Reduction with Redundancy and Sophisticated Call Management 27

Phase 3: Toll Reduction for Enterprise Networks, Small/Medium Businesses, and Consumers 28

Phase 4: Toll Reduction with Advanced Services and Standardization 31

Conclusion 32

Converged Networks

Case Studies

Converged networking is an emerging technologythrust that integrates voice, video, and data traf-fic on a single network. The market drivers forconverged networks are cost reduction; supportfor sophisticated, highly integrated applications;and the provision of greater network flexibilityand functionality.

This white paper presents four case studiesfocusing on high-influence market segments andapplications that can benefit from converged net-working technology. The selection of these exam-ples is intended to provide a basic understandingof the technology issues involved in network con-vergence. For each case study, the analysis includesa set of required technology capabilities.

Overview of Converged Networks

As networking technology becomes pervasive,opportunities arise for using it in new andmore creative ways. One example is that ofusing data networks, rather than the traditionalcircuit switched networks, to carry voice andvideo traffic. The generic term for this kind ofuse is converged networking. Converged net-working offers many benefits, including costsavings and the enabling of new, tightly inte-grated, multimedia applications.

The World Wide Web has permanentlychanged the nature of networking. Before itsappearance, networking was the province ofspecialized applications running in privatecorporations and research institutions. Today,networking is used by millions of peoplearound the world. The Internet has becomethe backbone for small business communica-tions. Networking has permanently changedthe way organizations do business.

Like most revolutionary technologies, theWeb has drawn together previously separateactivities and integrated them under a com-mon framework. Web pages no longer provideonly text and static graphics; they also provideanimated graphics, audio, video, and othermultimedia content. Consequently, the Websupports the convergence of content delivery

over networks. The Web is to content deliverywhat backplane buses are to computer systems.

The Web is one example of a larger trendin networking. Formerly distinct activities areundergoing integration into a common frame-work. Integration is occurring at a number ofdifferent levels, most noticeably at the applica-tion level, where users expect ease of usebetween different applications (such as Webbrowsing, calendaring) as well as applicationsthat incorporate a diversity of data types (suchas documents that embed spreadsheets, graph-ics, and voice annotation). The motivationbehind this trend includes ease of use, reducedcost, and increased functionality. Similarly,users are showing interest in solutions thatprovide a diverse range of functionality in asingle network (voice/data/video integration)and offer the possibility of reduced cost (lesscapital equipment acquisition, less need for arange of technical experts in different areas).

The concept of convergence describes thistrend toward tighter integration. Convergednetworking encompasses several aspects, all ofwhich are related to the aggregation of net-working activity.• Payload convergence is that aspect of con-

verged networking wherein different datatypes are carried in the same communica-tions format. For example, while in the pastaudio and video traffic was carried over cir-cuit switched networks as Layer 1 bitstreams, while bursty data traffic was carriedover packet switched networks in Layer 3datagrams, payload convergence describesthe trend to carry both audio/video andbursty data traffic in Layer 3 datagrams.Note, however, that payload convergencedoes not prohibit the network from han-dling packets differently, according to theirservice requirements.

• Protocol convergence is the movementaway from multiprotocol to single protocol(typically IP) networks. While legacy net-works are designed to handle many proto-cols (e.g., IP, IPX, AppleTalk) and one typeof data (so called “best effort”), convergednetworks are designed to support one proto-col and provide the services necessary for

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Acronyms andAbbreviations

ACD

automated call distribution

ATM

Asynchronous Transfer Mode

BGP4

Border Gateway Protocol

Version 4

CoS

Class of Service

CMTS

cable modem transmission

system

CWE

Collaborative Work

Environment

DHCP

Dynamic Host Configuration

Protocol

DNS

Domain Name Service

DSLAM

digital subscriber loop

access multiplexer

DVMRP

Distance Vector Multicast

Routing Protocol

ELAN

emulated LAN

IEEE

Institute of Electrical and

Electronics Engineers

IETF

Internet Engineering Task

Force

IGMP

Internet Group Management

Protocol

IP

Internet Protocol

IPsec

IP Security

ISDN

Integrated Services Digital

Network

multiple types of data (such as voice, one-way video, interactive video, best effort).

• Physical convergence occurs when payloadstravel over the same physical networkequipment regardless of their service require-ments. Both multimedia and Web trafficcan use the facilities of an edge network,even though the former has more stringentbandwidth, delay, and jitter requirementsthan the latter. Resource reservation, prior-ity queuing and other Quality of Service(QOS) or Class of Service (COS) mecha-nisms within the network are used to differ-entiate the service requirements of one typeof traffic from another and to deliver thenecessary service to each.

• Device convergence describes the trend innetwork device architecture to support dif-ferent networking paradigms in a single sys-tem. Thus, a switch may support Ethernetpacket forwarding, IP routing and Asyn-chronous Transfer Mode (ATM) switching.Network devices may handle data, carriedby a common network protocol (i.e., IP),that have separate service requirements (e.g.,bandwidth guarantees, delay, and jitter con-straints). In addition, an end system maysupport both Web-based data applicationsand packet telephony.

• Application convergence represents theappearance of applications that integrateformerly separate functions. For example,Web browsers allow the incorporation ofplug-in applications that allow Web pagesto carry multimedia content such as audio,video, high-resolution graphics, virtual real-ity graphics, and interactive voice.

• Technology convergence signifies the movetoward common networking technologiesthat satisfy both LAN and WAN require-ments. For example, ATM can be used toprovide both LAN and WAN services.

• Organizational convergence is the central-ization of networking, telecommunications,and computing services under a singleauthority, for example, the chief informa-tion officer. This provides the necessarymanagerial framework for integrating voice,video, and data on a single network.

These aspects of converged networkingallow the integration of voice, video, and dataservices from the edge of the network to thecore. The following sections provides a briefdescription of the market drivers for convergednetworks and a summary of converged net-work architecture. The remainder of the paperpresents four application case studies forconverged networks and describes the tech-nologies necessary to support successivedeployment phases for each application.

What Is Driving Converged Networks?

Several emerging forces are driving marketinterest in converged networks: • Cost reduction, both in capital outlay and

technical support expenditures• The emergence of sophisticated, highly inte-

grated applications that put new demandson networks

• Greater network flexibility and functionality• The emergence of industry standards

Organizations will replace their existingvoice, data, and video infrastructures by a con-verged network only if they anticipate sub-stantial savings in both capital expenditureand day-to-day operational costs. At the sametime, a converged network must deliver ser-vice at least equivalent to existing facilities.

Achieving the necessary cost/serviceobjective requires the use of emerging andanticipated technologies. Organizations aregenerally leery of using proprietary technolo-gies when faced with major upgrades to theirnetworks. Consequently, the fundamentaltechnologies of converged networks must bestandards-based, and the network deploymentmust be incremental.

Certain applications are difficult to sup-port on existing communication infrastruc-tures. For example, coordinating customervoice calls with database accesses that manipu-late customer records currently requires spe-cialized application hardware and software.Over a converged network, packet voice anddatabase access use a common network, allow-ing software applications to provide this ser-vice and eliminating the need for specializedapplication hardware.

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ISP

Internet service provider

ISSLL

Integrated Services over

Specific Link Layers

ISUP

ISDN User Part

ITU

International

Telecommunications Union

IVR

interactive voice response

L2TP

Layer 2 Tunneling Protocol

LAN

local area network

LDAP

Lightweight Directory

Access Protocol

LRU

line replaceable unit

MAC

Media Access Control

MCU

Multipoint Control Unit

NIC

network interface card

NSP

network service provider

ODBC

Open Database Connectivity

OSPF

Open Shortest Path First

PBX

private branch exchange

PPP

Point-to-Point Protocol

PPTP

Point-to-Point Tunneling

Protocol

Another market motivation for convergednetworks is indirectly related to integratingvoice, video, and data on a single network.Many of the characteristics necessary for aconverged network, such as robustness, man-ageability, availability, and so on, are alsodesirable characteristics for legacy networks.As the features that support these characteris-tics are developed, organizations without apressing need for converged networks will beattracted to products containing such featuresin order to improve their existing legacynetworks.

Cost Reduction

The potential for cost reduction in convergednetworks arises from the elimination ofunnecessary infrastructure duplication. Itmust be noted that some duplication is desir-able in order to meet reliability objectives.However, there are unjustifiable costs associ-ated with duplicate equipment acquisition andmaintenance for separate data, voice, andvideo networks, duplicate management infra-structure for these networks, duplicate person-nel to service these networks, and duplicatefacilities costs (for example, for cabling plant,wire closet floor space, cooling) to bring theservices of these networks to users.

The University of Oklahoma in the U.S.is deploying IP-based video conferencing toChoctaw County high schools. They choseIP-based video conferencing for several reasons.Integrated Services Digital Network (ISDN)availability is limited in Choctaw County. At$92/month and requiring an expensive multi-plexer, ISDN is too expensive. Finally, an IP-based system uses the same cable plant forvideo conferencing as is used for Internet access.

Polaroid Corporation (Cambridge, Mass-achusetts) also sees cost reduction possibilitiesin converged networking. “Users can reap

benefits by running voice over Frame Relayinternationally, as voice rates are far higheroutside the U.S.,” says George Deyett, telecom-munications operations manager for Polaroid’s20-country Frame Relay network. “The savingspay for the cost of the equipment you need ina matter of months.”1 The principle is simple.If an enterprise can run all of its applicationson one network, it will save money.

Increasing economic pressures are forcingnetwork service providers (NSPs) to considertechnologies that provide the highest level ofservice for the least cost. Greg Jacobsen, execu-tive vice president of MCI Systemhouse(Atlanta, Georgia), says, “Today, customershave five bidders; they pit them against eachother to drive out the biggest penalties, costs,and service levels, and they ride them like ahawk.”2 Under scrutiny of this kind, NSPsmust determine the costs of service level agree-ments (SLAs) to ensure profitability. Theymust also effectively manage their networks toachieve those SLAs.

In the consumer and small business mar-kets, moving long distance traffic onto packetswitched networks will provide significantreductions in long-distance telephone bills.For example, Level 3 Communications, Inc.(Omaha, Nebraska) will provide an inte-grated telephony and data service that carriesvoice traffic over an IP network. Level 3 hasattracted $2.5 billion from Kiewit Capital,which they plan to spend building a newinternational fiber network. Level 3 CEOJames Crowe says, “Our goal is to make everyfax and phone a terminal to access our IP net-work.” The cost advantages of IP packetswitching will drive this market. “We’re in themiddle of a fundamental change—the same asthe telegraph to the telephone,” Crowe con-tinues. “IP enjoys a 100-to-one cost advantageover switched networks.”3

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PSTN

public switched telephone

network

QoS

Quality of Service

RIP

Routing Information

Protocol

RMON

Remote Monitoring

RSVP

Resource Reservation

Protocol

RTP

Real-Time Transport

Protocol

RTSP

Real-Time Streaming

Protocol

SLA

service level agreement

SONET

Synchronous Optical

Network

SS7

Signaling System 7

TCAP

Transaction Capabilities

Application Part

ToS

Type of Service

VC

virtual circuit

VPN

virtual private network

WAN

wide area network

xDSL

digital subscriber line

xMDS

Multipoint Distribution

Service

1 “Cisco Plots Voice/Data Integration,” Computerworld, October 27, 1997; http://www.computerworld.com/.

2 Emily Kay, “Sleuthing for Services: Managers Closely Scrutinize Outsourcers as They Rely More on Third Parties to KeepTheir Networks Running,” LAN Times, July 1997.

3 Randy Barrett, “Billion-Dollar Net Telco Born,” Inter@ctive Week, January 19, 1998; http://www.zdnet.com/intweek/daily/980119a.html.

Emerging Technologies

The merger of data, voice, and video traffic inthe home market is on the horizon. Commu-nications technologies such as cable modems,digital subscriber line (xDSL) services, andMultipoint Distribution Service (xMDS) pro-vide the necessary bandwidth and multiplex-ing capabilities to support multiple trafficclasses. Furthermore, there are preexisting dis-tribution facilities (coaxial cable and fiber inthe case of cable modems, twisted pair in thecase of xDSL, and electromagnetic spectrumin the case of xMDS) that enable the rapiddeployment of these technologies. In addition,computer and communications equipmentmanufacturers are developing low-cost prod-ucts with the potential to utilize these newinterconnection technologies.

Coupling low-cost devices with low-costmultimedia applications like Microsoft’s freeNetMeeting application will substantiallyincrease demand for multimedia applications.This in turn will further accelerate the conver-gence of networks. The large number of devicesand media types will also encourage networkconvergence. It is not economical to provide aphysically separate device for each media type.

Greater Flexibility and Functionality

Converged networks provide the necessaryinfrastructure to support applications integrat-ing voice, video, and data management. Thisallows customers to achieve their objectivesmore effectively and efficiently. The GartnerGroup writes, “We believe that interactivemedia will have as much of an impact on cor-porate and government computing applica-tions as client/server computing.”4

IT personnel in enterprise networks usedto worry about what power users might do totheir networks. With the availability of audioand video sound clips on the Web and withapplications like PointCast gaining wide

acceptance, even average users are now a forcefor convergence within the enterprise network.

In addition, enterprises are now providingmultimedia content on their own intranets.Corporations use multimedia on their networksto invigorate corporate training and more eas-ily convey corporate messages. Guy Baltzelle,instructional designer for AT&T WirelessServices in Redmond, Washington, says, “Train-ing on the wireless industry’s standards, proto-cols, network elements, and mobile switchingmight seem static without some entertaininggraphics.”5 Without multimedia, corporatemessages and training would be less effective.

The MITRE Corporation (Bedford,Massachusetts) is working on a CollaborativeWork Environment (CWE) application, whichincorporates text, audio, and multicast fullmotion video. CWE provides users with a richset of information management tools, allow-ing them to carry out their job assignmentsmore effectively. MITRE intends to use CWEboth as an in-house tool and as a model for itsgovernment customers.

The University of Mississippi also seestheir network converging and seeks the latestnetworking technologies. When asked whatmotivates the University to move to a con-verged network, network manager MikeMyrick replies, “People are starting to experi-ment with multicast. Desktop video confer-encing may be next.”6

Convergence is also an increasingly attrac-tive prospect in the high-end Web site hostingand collocation industry. Traditional sites pro-vide low-priority transactions incorporatingtext and graphics. Today’s sites also provideaudio and video as well as electronic com-merce transactions, which require extremelyhigh priority and security. Dataquest predictsthe total collocation market will grow to $2.6billion by the year 2001, from $633 million in1997, with high-end business increasingexponentially.7

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4 Gartner Group, “Interactive Media: Integrative View and Commentary,” March 28, 1997.

5 Kathleen Murphy, “Multimedia Applications on Rise Within Corporate Webs: Shockwave, Other Tools Being MoreWidely Deployed,” Webweek, December 6, 1996.

6 Jeff Caruso, “Ole Miss Students Tap VLAN’s Power; Layer 3 Moots Issue of Moves, Adds, Changes,” Techweb, December 1,1997.

7 Michelle V. Rafter, “Exodus Invests in Data Centers as High-End Outsourcing Market Booms,” Webweek, December 15, 1997.

Standards

Converged networks depend on the availabil-ity of standards to ensure their widespreaddeployment. Standards useful in a convergednetwork, such as International Telecommuni-cations Union (ITU) H.323, Institute of Elec-trical and Electronics Engineers (IEEE)802.1p/Q, and Real-Time Transport Protocol(RTP), to name a few, have been developedover the last several years and are now beingimplemented in products.

ITU standards such as H.323 enablepacket switched networks to carry telephonytraffic. IEEE standards 802.1p and 802.1Qsupport prioritization of data traffic at Layer2, which enables QoS support. Gigabit Ether-net increases bandwidth, allowing convergednetworks to carry increased traffic load. Inter-net Engineering Task Force (IETF) standardssuch as RTP, Integrated Services over SpecificLink Layers (ISSLL), and Real-Time Stream-ing Protocol (RTSP) enable IP networks tocarry multimedia traffic.

Converged Network

Architecture

There are many ways to imple-ment a converged network. One

might assume a homogeneous infra-structure, either completely packet-

based and connectionless (such as sharedand switched LANs, packet-service WANs) orconnection-oriented (such as ATM to the desk-top and long-distance ATM clouds). In prac-tice, neither of these architectural options isviable, due to the different economic and per-formance requirements for LANs and WANs.A converged network that spans large dis-tances will have a WAN core network that issurrounded by LAN edge networks (Figure 1).

In the general case, the edge networks willbe based on different technologies. Thus, oneedge network may be based on a switchedEthernet fabric (i.e., one without Layer 3routing), another on routed Ethernet seg-ments, and a third on ATM LAN technology.

The core may be a single technology net-work, such as Frame Relay, ATM, or the Inter-net. Alternatively, it may consist of multipleparallel networks, some connection-orientedand some packet switched (Figure 2).

While it is possible to solve many QoSproblems in the LAN by radical overprovi-sioning, this is not economically feasible in aWAN. Thus, WANs are engineered to optimizetheir resource use for a particular class of traffic.

Pure packet-based networks, such as a largeportion of the Internet, provide good serviceto bursty, non–time-critical traffic. They donot deliver good service to traffic with tight

bandwidth, delay, and jitterrequirements. Connection-ori-ented networks such as ATM,on the other hand, provide good

service to traffic with tight band-width, delay, and jitter require-

ments. However it is costly to usethese networks for bursty traffic, since

they reserve resources and charge forthem whether or not they are used.

Consequently, a converged network islikely to use the parallel WAN networks

according to service requirements of the traf-fic routed to them. LANs will carry voice,

66

LAN edge

network

LAN edge

network

WAN core

network

Figure 1. WAN Core Network with LAN Edge

Networks

LAN edge

network

LAN edge

network

Parallel WAN

core networks

Figure 2. Parallel WAN Core Networks

data, and video traffic over a common physi-cal infrastructure. At the LAN/WAN bound-ary, traffic will be classified and routed overthe most appropriate WAN network. Forexample, bursty, non–time-critical traffic willbe routed over a packet switched WAN. Mul-timedia data, however, will probably be routedover a connection-oriented network, such asATM, that provides QoS guarantees.

Converged networks may be able to opti-mize application performance by customizingnetwork devices on an application-by-applica-tion basis. Filtering network traffic in a waythat identifies application traffic and thenhandling that traffic according to the applica-tion’s unique processing requirements is anexample of this approach. The use of activenetworking,8 whereby applications downloadsmall programs or configuration data into net-work devices, is another example. There aresome important issues to address, such assecurity, resource management, and inter-device coordination, but there is also anopportunity to obtain significant competitiveadvantage if the network can optimize servicesfor important applications.

Case Studies

Converged networks require new technologyfor their implementation and deployment.The remainder of this paper presents casestudies that illustrate the phased deploymentof technology to support four key applicationsas they grow within a converged network.Case studies are presented for the followingfour applications:• Call centers• Financial transaction applications• Virtual classrooms and corporate training• Toll reduction

Case 1: Converged Network Support

for Call Centers

Call centers are business units that accepttelephone calls in order to provide customerservice, such as product purchase, product

maintenance, customer relations, and cus-tomer support. Centers may be third-partyoutsourcing businesses or organizations withina large corporation.

A call center is staffed by agents who acceptcustomer calls and then coordinate the pro-vided service. Normally, this requires the agentto associate the customer with records or otherinformation held in a database and to updatethese records according to the service request.

A service call proceeds as follows. First,the incoming call is routed to an appropriatefree agent. If no agents are available, the call isrouted to holding equipment that provides thecustomer with an appropriate message andthen queues the call for service. When anagent answers the call, the calling number maybe used to find a customer database record,which provides the agent with informationnecessary to service the call. In some cases thecustomer may provide additional information,such as account or tracking numbers, that isused to retrieve additional data. Once the ser-vice call is complete, the agent releases it andbecomes available for further service requests.

Existing call centers utilize a variety ofproprietary call service equipment, known asautomated call distribution (ACD) servers,which tie a public switched telephone network(PSTN) call to a PC. These servers extractincoming call information, such as the callingID, passing it to an application running onthe PC, which performs the necessary data-base access. They also provide hold-queue,interactive voice response (IVR), accounting,and monitoring services. ACD servers areexpensive and not easily customized to meetcustomer requirements, and they present sig-nificant complexities when deployed in a dis-tributed environment involving multiple callcenter sites.

Consequently, there is significant motiva-tion for customers to migrate to a convergednetwork solution. Converged networks allowboth the telephone call and the caller’s serviceinformation to arrive at the agent over a

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8 David L. Tennenhouse and Davide J. Wetherall, “Towards an Active Network Architecture,” Computer CommunicationReview, ACM Special Interest Group on Data Communication, April, 1996, pp. 5–18.

common communications fabric. The ACDserver is replaced by an ACD application run-ning on a call center server that distributespacket voice calls and coordinates them withcustomer record retrieval. This reduces cost byusing standard, off-the-shelf hardware, pro-vides the foundation for more flexible call cen-ter applications, and naturally allows the callcenter application to be distributed over mul-tiple call center sites.

The migration of call centers to con-verged networking is described here in fivephases. In each phase, the solution builds onfunctionality made available in the precedingphases. In addition, the solution provided ateach phase introduces new flexibility in howthe call center is deployed.

Phase 1: Single Call Center on a Dedicated LAN

Perhaps the simplest way to integrate call cen-ter voice and data on the same network is todedicate a LAN exclusively to call center oper-ations (Figure 1-1).

This configuration is attractive to cost-conscious customers who have proprietary ACDserver equipment and who want to have moreflexibility in customizing their applicationsand to decrease the complexity of multi-sitedeployments. The call center server providessome of the functionality of the ACD server,including hold queues, IVR, and accounting

functions. To ensure the appropriate level ofservice without introducing traffic prioritiza-tion, the LAN must be over-provisioned.

The following technologies are requiredto implement this configuration:• H.323 gateway. An H.323 gateway packe-

tizes voice traffic arriving over the PSTNand forwards it to an agent’s station.

• H.323 client on end system. The end sys-tem serving the call center agent must beable to handle H.323 traffic.

• H.323 gatekeeper. An H.323 gatekeeperprovides basic call management functionsfor routing calls coming through the H.323gateway to an agent station.

• Multipoint Control Unit (MCU). AnMCU provides the functionality to imple-ment teleconferencing, which allows multi-ple agents to cooperate to service anincoming call.

• Efficient multicast routing and filtering.To implement teleconferencing, the dedi-cated LAN must support efficient multicastrouting and filtering, which reduces the costof overprovisioning the LAN.

• Monitoring capabilities. LAN traffic mustbe monitored to ensure that it is distributedaccording to the policy implemented by thecall center server and that LAN resourcescontinue to be overprovisioned as the callcenter grows. Both RMON2 and distrib-uted RMON can be used for this purpose.

• Reliable Domain Name Service (DNS)/Dynamic Host Configuration Protocol

88

Customer

H.323 gateway

Database server

Agent station

Agent station

H.323 gatekeeperCall center server

LAN

• • •

PSTN

Figure 1-1. Single Call Center on a Dedicated LAN

(DHCP). As agents arrive at and leave work,they must reconnect and disconnect theirmachines from the call center application.This means their PCs must obtain IP addressleases as well as locate various servers imple-menting the call center functions. Conse-quently, there must be reliable DNS andDHCP services to ensure that calls are notdropped during shift transitions.

• Resilient links and hot-swappable linereplaceable units (LRUs). The underlyingcommunications fabric must be reliable aswell. When links fail, backup links must auto-matically take over the new load. Resilientlinks provide this capability. When networkdevices experience failures in their compo-

nents, the smallest replaceable part that con-tains the failed component (an LRU) must beswapped out and a correctly operating partswapped in. To ensure the reliability necessaryfor a call center, LRUs must be hot-swap-pable; that is, the network device should con-tinue to operate while the LRU is replaced.

Phase 2: Two Call Centers on Dedicated LANs,

Interconnected by the PSTN

One way of generalizing the single dedicatedLAN call center is to allow it to be distributedacross multiple sites. In the simplest case, twosites can be interconnected by the PSTN withprivate link interconnection of the gatekeepers(Figure 1-2).

99

Customer

H.323 gateway

Database server

Agent station

Agent station Private

link

H.323 gatekeeper

Call center server

LAN

• • •

H.323 gateway

Database server

Agent station

Agent station

H.323 gatekeeper

Call center server

LAN

• • •

PSTN

Figure 1-2. Call Centers on Dedicated LANs Interconnected by the PSTN

Using multiple call center sites is attractivefor a number of reasons:• It allows the placement of call center sites in

different time zones, which increases thehours during which the call center is opera-tional.

• It allows customers to call a particular siteand still use the spare capacity of a remotesite when the first becomes oversubscribed.

• It decouples call site operations from limi-tations such as physical plant space, avail-able phone numbers, and trained agentavailability.

• It allows large organizations to distributecall center operations over a number ofadministratively separate suborganizationswithout requiring them to share space.

The following additional technologies arerequired to support this configuration:• H.323 gatekeeper coordination. Both sites

must have their own H.323 gatekeepers,which must to coordinate with one another.This requires a gatekeeper-to-gatekeeperprotocol supporting basic functionality.

• Signaling System 7 (SS7) integration withH.323. When a call request arrives at anH.323 gatekeeper that needs to be reroutedto another call center, the gatekeeper (ormore likely an embedded SS7 gateway)signals the rerouting information to thePSTN using SS7, the call signaling protocolused within the PSTN.

Phase 3: Multiple Call Centers on Dedicated

LANs, Interconnected by a WAN

The next level of generality supports multiplecall center sites by interconnecting themthrough an overprovisioned WAN (Figure 1-3).Call forwarding is achieved by H.323 gatewaysupport of SS7.

Since customer data may reside on aremote database server, call center LANs areinterconnected by a WAN. This phase alsoeliminates the private link required in phase 2,since inter-gatekeeper traffic can now travelover the WAN. These characteristics enablelarge customers to build large call centers dis-tributed over many sites.

1100

H.323 gateway

Database server

Agent station

Agent station

H.323 gatekeeper Call center server


Customers

LAN

• • •

H.323 gateway

Database server

Agent station

Agent station


LAN

• • •

H.323 gateway

Database server

Agent station

Agent station

LAN

• • •

H.323 gateway

Database server

Agent station

Agent station


LAN

• • •

WAN

Customers

PSTN

PSTN

Figure 1-3. Multiple Call Centers on Dedicated LANs Interconnected by a WAN

The following additional technology isrequired for this configuration:• Multicast distribution management and

troubleshooting. Support of an arbitrarynumber of call center sites introduces scal-ing considerations for multicast, which isrequired for MCU teleconferencing. Inorder to effectively address this issue, theconverged network must support effectivemulticast distribution management andtroubleshooting.

Phase 4: Multiple Call Centers on Dedicated

LANs, Interconnected by a WAN, with Customer

Access over the Internet

Another generalization of call centers operat-ing over converged networks allows incomingcalls not only from the PSTN, but also

directly from customer PCs using packet tele-phony over the Internet (Figure 1-4).

The addition of Internet access allows thecall center to service new customers who wantto receive service from their packet voice-capa-ble PCs. This enlarges the market served bythe call center, thereby increasing potentialrevenue.

The Internet currently does not providesufficient service guarantees to support busi-ness-grade voice traffic. However, the IETF isworking on this problem and may have a solu-tion in a reasonable time frame. In addition,use of the Internet introduces significant secu-rity issues that must be addressed.

The following additional technologies arerequired for this configuration:

1111

H.323 gateway

Database server

Agent station

Agent station

Customers

LAN

• • •

H.323 gateway

Database server

Internet customers

Agent station

Agent station


LAN

• • •

H.323 gateway

Database server

Agent station

Agent station

LAN

• • •

H.323 gateway

Database server

Agent station

Agent station


LAN

• • •

WAN

Internet

Customers



PSTN

PSTN

Figure 1-4. Multiple Call Centers on Dedicated Lans Interconnected by a WAN with Customer Access

over the Internet

• IP differentiated services. The use of IP tocarry voice traffic requires support for prior-itization. Current work in the IETF is inves-tigating use of the Type of Service (ToS)field in IP headers to tag traffic according toits urgency, as well as resource reservation bymeans of the Resource Reservation Protocol(RSVP). RSVP is a signaling protocol usedfor reservation, and ToS bits indicate adesired priority. There must be mechanismsin Layer 3 switches and routers to imple-ment this priority, such as packet schedulingalgorithms in routers or 802.1p–compliantpriority queuing mechanisms in switches.Either of these approaches, or another thatprovides the necessary IP traffic handlingcharacteristics, is required to support busi-ness-grade packet telephony over theInternet.

• ISSLL-LOW. In the most common case,customer PCs will be connected to theInternet via a dial-up link connected toremote access equipment. Since voice anddata traffic will share a common link, a linktraffic prioritization scheme must be used toensure that voice traffic has precedence overdata traffic. The ISSLL-LOW standarddefines such a scheme.

• Virtual private networks (VPNs). Manypacket voice applications assume that pack-ets sent between the sender and receiverarrive in order. However, IP may re-orderpackets carried over the Internet. Conse-quently, a VPN tunneling protocol, such asPoint-to-Point Tunneling Protocol (PPTP)or Layer 2 Tunneling Protocol (L2TP),must be used for voice traffic to ensure thatpackets arrive in order at the receiver whenvoice traffic transits the Internet.

• Media protection. Since the Internet doesnot provide sufficient reliability for busi-ness-grade voice traffic, and since voice traf-fic is not suited for error correction schemesbased on retransmission, forward error cor-rection techniques are necessary to ensurethe appropriate level of reliability for voicetraffic over the Internet.

• IP Security (IPsec). Traffic over the Internetis inherently unsecure. Since call centervoice traffic may carry business-sensitive

data, it must be protected by a security pro-tocol providing confidentiality, integrity,and authentication services. IPsec is thestandard protocol for these services.

• Cryptographic policy management. Man-aging IPsec is an arduous task unless there issome help in the form of cryptographic pol-icy management. This is required in anypractical, large-scale deployment of IPsec.

• Security policy management. It is likelythat once customers can access call centersdirectly over the Internet, new applicationswill arise that utilize this direct connectivity.This will turn call centers into extranets,whereby customers are allowed access topreviously isolated systems. To control thesecurity threats this introduces, call centerswill require security policy management sys-tems, such as the Multilayer Firewall andNetwork Login, which protect the call cen-ter from security threats mounted fromwithin the call center LAN.

Phase 5: Multiple Call Centers on Multi-

Application LANs, Connected by a WAN, with

Customer Access over the Internet

As the market for call centers on convergednetworks matures, customers will require eventighter integration of the center with the restof their business. For example, customers willintegrate call center and financial transactionapplications, such as SAP, in order to providebusiness-critical services to callers. Thus,LANs will be shared by call center operationsand other applications (Figure 1-5).

Implementing call center operations on amulti-application LAN allows businesses tointegrate other applications with call centeractivity. For example, call centers used forproduct purchase or other business transac-tions could integrate call center services withfinancial transaction services. This wouldallow an agent to service an incoming call, usethe identified customer’s records to authorizepurchases, and then use the financial transac-tion application to execute them.

This is the first phase in which large-scaleconverged networks are a factor, introducingscaling, reliability, and prioritization require-ments.

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The following additional technologies arerequired for this configuration:• Prioritization of LAN traffic. Priority queu-

ing of LAN traffic requires tagging ofMAC-level frames and switch support forpriority queuing. IEEE standard 802.1Qdefines frame tagging, while 802.1p defineshow an 802.1D-compliant switch canimplement priority queuing based on those

tags. LAN equipment such as switches andnetwork interface cards (NICs) must sup-port these standards (or their relevant parts)so voice traffic can receive higher prioritythan data traffic.

• Policy management of traffic prioritiza-tion. It is impractical to manually configurea large number of switches and NICs inorder to implement a coordinated, high-

1133

H.323 gateway

Database server

Agent station

Agent station

H.323

gatekeeper

H.323

gatekeeper

Call

center server

Call

center server

Other

application server

Other

application client

Other

application server

Other

application

server

Customers

Other

application client

Other application

client

Other application

client

LAN

• • •

H.323 gateway

Database server

Internet customers

Agent station

Agent station


Other application

server

LAN

• • •

H.323 gateway

Database server

Agent station

Agent station

LAN

• • •

H.323 gateway

Database server

Agent station

Agent station


LAN

• • •

WAN

Internet

Customers

PSTN

PSTN

Figure 1-5. Multiple Call Centers on Multi-Application LANs Connected by a WAN with Customer Access

over the Internet

priority service for voice traffic. Conse-quently, call centers on multi-applicationLANs require policy management tools forconfiguring priority information in networkdevices.

• Bulk configuration of network devices. Alarge scale converged network presents sig-nificant management problems that cannotbe met by manual device configuration. Toreduce costs and free network managementpersonnel to work on problems with solu-tions that cannot be automated, devicesmust be managed as groups, rather than assingle systems. This requires network man-agement tools that support coordinatedconfiguration of devices.

• Rapid, coordinated fault-recovery. Whenparts of a large scale converged network fail,manual methods of recovery are expensiveand time consuming. For call center support,converged networks must provide rapid,coordinated, and automated network faultrecovery.

• Enhanced gatekeeper-to-gatekeeper inter-actions. Basic gatekeeper functionality pro-vides for call hand-off on a per call basis. Ina large scale converged network, moresophisticated interactions are necessary. Forexample, there may be a requirement forload-balancing or fail-over between gatewaysin different call center sites. Furthermore,

migration of agents between sites requiresdynamic distribution of agent locationinformation between gatekeepers.

Case 2: Converged Network Support for

Financial Transaction Applications

Financial transaction applications have a widerange of uses within vertical market segments,such as the financial industry, and within hor-izontal markets, such as the financial arms ofcorporations in all industries. One of the mostcommon applications of this kind is SAP,which is used for general ledger, accountspayable, accounts receivable, manufacturing,shipping and receiving, and order processingand fulfillment, among other things.

SAP is a three-tiered application (Figure2-1). A SAP client makes a request to anapplication server, which implements all busi-ness logic. This functional distribution resultsin a very thin client, which is advantageoussince the number of clients may be very large.The application server accepts a client requestand accesses data in back-end databases to ser-vice the request.

A typical network supporting SAP sepa-rates the physical subnetwork holding thedatabase servers from the rest of the network,i.e., from those parts holding the clients. Theapplication server acts as the mediator between

the two. In certain cases, other applica-tions may access the databaseservers as well.

Maintaining a separate physi-cal back-end subnetwork for thedatabase servers is expensive. Notonly must the subnetwork havededicated equipment, but man-

agement of the enterprise net-work is incoherent. In effect

there are two networks tomanage, the database sub-

network and the rest ofthe enterprise net-work. Consequently,

IT organizations aremotivated to integrate the data-

base subnetwork into the enterprise network. To accomplish this integration, certain

business-critical requirements must be met.

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SAP clientsApplication servers

Database servers

Back-end

network

Enterprise

network

Figure 2-1. SAP Distributed Architecture

Traffic between the application servers and thedatabases must be high priority, since financialtransactions are the lifeblood of a commercialcompany. Communications between theapplication servers and the database must behighly available and reliable. In some deploy-ments (for example, the securities industry),even a small delay in a transaction can costmillions of dollars.

Integrating a financial transaction appli-cation into an enterprise is further compli-cated as companies move to convergednetworks. In addition to data traffic, transac-tions must compete in these networks withhigh QoS multimedia traffic, such as packetvoice. However, there are compelling reasonsother than cost why financial transactionapplications may need to use the services of aconverged network. An important example isthe use of such applications in call centers tosupport product purchase, shipment tracking,and other customer service objectives.

The migration of financial applications toconverged networks is described in threephases. In each phase, the solution builds onfunctionality made available in precedingphases. In addition, the solution provided ateach phase generalizes the deployment scenar-ios for the application.

Phase 1: Data Only

Existing applications and network architecturesupporting financial transaction applicationsis the baseline for financial transaction appli-cation deployment on converged networks.This phase addresses how financial transac-tion applications currently operate. The basicrequirement is high availability and reliabilityof network services.

The technologies required in this phaseare required in all subsequent phases. Thesetechnologies are:• Fast, convergent routing. When failures

occur in a large network, the routing proto-col must react quickly to restore connectiv-ity. Routing protocols such as RoutingInformation Protocol (RIP) do not have thischaracteristic, while Open Shortest PathFirst (OSPF) does. Consequently, networks

supporting financial transaction applica-tions should use OSPF.

• Routing domain support. Large networkssupporting financial transaction applicationsmust be partitioned into routing domains;otherwise it is difficult to contain failuresaffecting routing information. Inter-domainrouting protocols such as Border GatewayProtocol v4 (BGP4) are then necessary toroute between these domains.

• Over-provisioned LANs and WANs. Busi-ness-critical applications such as SAP mustalways have all necessary network resourcesavailable for execution. In phase one, this isguaranteed by radical overprovisioning ofLANs and WANs.

• Monitoring capabilities. Monitoring ofLAN traffic is required to ensure that trafficon the dedicated database LAN conforms tosite policy, and for capacity planning toensure that LAN resources continue to beoverprovisioned. Both RMON2 and distrib-uted RMON can be used for this purpose.

• Resilient links and hot-swappable LRUs.Highly available and highly reliable net-works must recover quickly from link andnetwork device failures. Resilient links allowthe network to continue in service when alink fails. Hot-swappable LRUs allow net-work devices to be repaired while onlineand in operation.

• Reliable DNS/DHCP. The support of mis-sion-critical applications in shared networksrequires stable IP address management.When a client starts a transaction, it mustlocate the appropriate application server,which is normally identified by DNS name.Consequently, DNS must provide a reliableservice. Similarly, when PCs running clientcode boot, they must be able to obtain anIP address, which requires a reliable DHCPservice.

• Monitoring tools for network manage-ment. Rapid response to network failuresrequires real-time monitoring tools that rec-ognize and diagnose faults. Network man-agement applications must tie into thesetools so that faults can be repaired quicklybefore they become critical.

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Phase 2: Voice and Data on Business-Critical

Networks

There are a number of reasons why a customermight want to deploy a business-critical appli-cation on a converged network supportingboth voice and data. For example, in phase 5of call center evolution described above, finan-cial transaction software is used to service pur-chase requests made during a customer callsession. Furthermore, it is expensive to main-tain a separate back-end network for applica-tion server–to-database interactions. Movingsuch interactions over a common networksupporting multiple applications typesincreases network operation efficiency.

Moving financial transaction applicationsto a converged network requires the provisionof priority services. Once these are available,the IT department can move the databaseservers onto the enterprise network, therebyeliminating the requirement for a separateback-end subnetwork (Figure 2-2).

It may be that these departments willmigrate the database servers to the enterprisenetwork before supporting voice. However, theset of technologies required to give financialtransaction traffic high priority are the sameset required to support both voice and high-priority data on a converged network. Conse-quently, the technology descriptions given hereapply to both situations. The following addi-tional technologies are required for phase 2:

• IP differentiated services. The use of IPto carry financial transaction traf-

fic requires support for priori-tization. Current work in theIETF is investigating use ofthe Type of Service (ToS) fieldin IP headers to tag traffic

according to its urgency, as wellas resource reservation by means of theResource Reservation Protocol (RSVP).RSVP is a signaling protocol used forreservation, and ToS bits indicate adesired priority. To implement this pri-

ority, there must be mechanisms in Layer3 switches and routers such as packet sched-uling algorithms in routers or 802.1p-com-pliant priority queuing mechanisms inswitches.

• Prioritization of LAN traffic. Priority queu-ing of LAN traffic requires tagging ofMAC-level frames and switch support forpriority queuing. IEEE standard 802.1Qdefines frame tagging, while 802.1p defineshow an 802.1D-compliant switch canimplement priority queuing based on thosetags. LAN equipment such as switches andNICs must support these standards.

• Policy management of traffic prioritiza-tion. It is impractical to manually configurea large number of switches and NICs. Con-sequently, financial transaction applicationsrequire policy management tools for config-uring priority information in networkdevices.

• Bulk configuration of network devices. Alarge-scale converged network presents sig-nificant management problems that cannotbe met by manual device configuration. Toreduce costs and free network managementpersonnel to work on problems with solu-tions that cannot be automated, devicesmust be managed as groups, rather than assingle systems. This requires network man-agement tools that support coordinatedconfiguration of devices.

• IPsec. Financial application data is sensitiveand requires protection from unauthorizedaccess. Moving this data in the clear acrossthe enterprise network presents a significantopportunity for unscrupulous employees

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Application servers

Database servers

SAP clients

Enterprise

network

Figure 2-2. Voice and Data Support on a

Business-Critical Network

and contractors to either sabotage business-critical operations or obtain potentiallyvaluable information. The use of the confi-dentiality, integrity, and authenticationservices of IPsec, which is the standard pro-tocol for protecting IP traffic, eliminatesmany of these security vulnerabilities.


• Security policy management. IPsec pro-vides strong security services, but is expen-sive in terms of both economic cost andcomputing resources. It is best to placeIPsec protection across enterprise networksegments that have a high exposure toattack. Within more isolated segments,security policy management technologiessuch as Multilayer Firewall and NetworkLogin can provide sufficient protection at alower cost.

• VPNs. The application server–to-databasetraffic of a financial transaction applicationcurrently runs over a protected, dedicatedLAN. When the database servers are movedto the enterprise, there is no reason whythey must be co-located. Some may belocated in different parts of the enterpriseand communications between them and theapplications servers may move over a WAN.If the application protocol between theapplication servers and databases relies oncertain Layer 2 characteristics, such as pack-ets not being reordered, these characteristicsmust be restored for operation across arouted network. VPN tunnels provide thesereliability features.

• ISSLL. In order to provide priority serviceacross LAN segments, 802.1p/Q tags mustbe mapped into IP-differentiated service pri-orities. ISSLL is an emerging IETF standardthat defines how to perform this mapping.

Phase 3: Voice, Video, and Data on Business-

Critical Networks with Multiple Data Centers

In the final phase of integrating financialtransaction applications onto a converged net-work, voice, video, and data are carried by the

common network. The introduction of videoservices may occur to achieve business-criticalobjectives (such as to provide top companyexecutives with video-teleconferencing capa-bilities on their desktops) or for non-business-critical purposes (such as broadcast talks orbusiness-related news programs to employeedesktops). In either case, video traffic maystress networking equipment, introducingmore opportunity for network failure.

In this phase, database servers are placedin multiple data centers, each under the con-trol of a separate administration. Using multi-ple data centers provides backup of criticaldata and allows a large company to organizeits financial work according to its organiza-tional structure (for example, subsidiaries runtheir own data centers, which interact withthose of other subsidiaries). The followingadditional technologies are required for phase 3:• Management of failover activity. Multiple

data centers allow auto fail-over when a cen-ter becomes unavailable. However, configu-ration of application servers so they movetheir transactions to the appropriate data-bases in such failure situations may be com-plex. Consequently, establishing fail-overpolicy in terms of high-level objectives isnecessary. This requires a failure policymanagement system.

• Capacity planning and better monitoringtools. To ensure that financial transactionapplications experience adequate service,network capacity must be sufficient to sup-port all high-priority traffic. Thus, capacityplanning is an important activity. Since con-verged networks are much more complexthan existing data-only networks, bettersimulation and analysis tools are necessary.In addition, better monitoring tools arerequired to provide the data necessary forsimulations and analysis.

• Standardized benchmarking/testingmethodologies. When simulation andanalysis indicate a network upgrade, the ITdepartment must use network device perfor-mance data to determine what equipment isneeded and where it should be placed. Sinceconverged networks support classes of trafficnot normally observed in currently deployed

1177

networks, network device vendors mustestablish standard and enhanced bench-marking and testing methodologies so cus-tomers can accurately plan their futureequipment acquisitions.

• WAN compression. The use of multipledata centers will create inter-center trafficthat in general will move over the WAN.Since some of this traffic may consist of largedata transfers, WAN efficiency becomes anissue. WAN compression techniques providefor the most efficient use of WAN resources,thereby reducing the cost of multiple datacenter operations.

• Point-to-Point Protocol (PPP) over Syn-chronous Optical Network (SONET). Inaddition to WAN compression, higherWAN bandwidth will alleviate inter-centertraffic bottlenecks. PPP over SONET elimi-nates overhead imposed by technologiessuch as ATM, thereby increasing the band-width delivered to the WAN customer forthe same cost.

Case 3: Converged Network Support for the

Virtual Classroom and Corporate Training

Customers in the education market includepublic and private elementary and secondaryschools, vocational schools, trade schools,community colleges, four-year colleges, bache-lor and graduate degree-granting universities,and professional graduate schools such asthose for law and medicine. In addition, local,state, and federal government departments aswell as private industry generally contain orga-nizations that provide educational servicessimilar to those offered by more traditionalschools.

The virtual classroom, where studentsattend classes in locations remote from theteacher or lecturer, provides an importantapplication for converged networks. Previously,virtual classrooms were implemented usingtraditional communications facilities over ana-log carrier equipment. However, there areseveral opportunities for enhancing the educa-tional experience by carrying voice, video, anddata traffic between the studio, where a lectureor other educational content is produced, andthe premises where the students are located.

For example, whiteboard data can be used toshare a common drawing space between lec-turer and student, allowing both to illustratepoints during a question and answer interac-tion. Class notes can be distributed electroni-cally during lectures and annotated by theteacher in real time to correct errors or improveexposition. Students can hand in homeworkelectronically using e-mail, and then receiveindividual help from a teacher during virtualoffice hours. There are some early adoptervirtual classrooms based on digital communi-cations supporting converged networkingfeatures.

The basic architecture for a virtual class-room includes a studio, which may be a dedi-cated facility or a lecture hall equipped withaudio and camera equipment, and one ormore remote classrooms. The latter may behalls or rooms with large-screen projectionequipment, rooms with individual desktopmachines dedicated to virtual classroom activ-ity, or individual desktop machines located instudents’ own quarters. There is a requirementfor rendezvous between voice, video, and datatraffic created both at the studio and at theremote classroom, which is a function ofvideo-conferencing software.

The migration of virtual classrooms tofully converged networking solutions isdescribed in five phases. The first phase repre-sents how a virtual classroom might be builtusing existing networking capabilities. Eachsucceeding phase builds on the technology ofthe previous ones to provide more flexibledeployment options.

Phase 1: Small Number of Dedicated LANs with

an ATM Campus Backbone Supporting ELANs

The first phase of support for virtual class-rooms utilizes LANs dedicated to virtual class-room communications interconnected by anATM campus backbone (Figure 3-1).

This configuration is attractive to cus-tomers who build remote classrooms exclu-sively for this purpose on a campus. Since theLANs are dedicated, they carry only virtualclassroom traffic. Configurations in this phasesupport voice and video traffic traveling fromthe studio to the remote classrooms, but only

1188

voice is returned in the opposite direction.This eliminates complexities arising from pro-viding and controlling video streams in bothdirections.

To ensure an appropriate level of service,overprovisioned edge LANs are required. Suf-ficient reserved virtual circuit (VC) bandwidthis required to guarantee uncongested trafficflows between the edge LANs. To eliminatecertain control problems, we assume there areonly a small number of edge LANs.

The following technologies are requiredto implement this configuration:• Media encoding. The studio must contain

video/audio encoding equipment, for exam-ple, that producing MPEG-1 streams. Forthe return audio channels, a proprietaryscheme, such as CUSeeMe is used, or thereturn audio may come out-of-band, forexample through PBX or H.323 equipment.

• Layer 2 multicast. Delivery of the out-bound (i.e., studio to remote classroom)video data uses Layer 2 multicast in theedge LANs. A common emulated LAN(ELAN) is used to interconnect the edgeLANs with the studio LAN for each session.If sufficient bandwidth is available in theedge LANs and ATM backbone, multiplevirtual classroom sessions can be supportedby using different ELANs for each session.However, restrictions in ATM switchingequipment may limit the number of ELANs

available at any one time.Optionally, to increase performance,

the ATM backbone may support Layer 2multicast.

• ATM access devices. The access devicebetween the ATM network and an edgeLAN must support the specification ofbandwidth, delay, and jitter requirementsfor ATM ELANs. This requirement ensuresthe appropriate level of service for emulatedLayer 2 multicasting.

• Audio bridge. To mix the outbound andreturn audio traffic, the studio must have anaudio bridge. This could be a digital or ana-log device.

• Resilient ATM switch fabric and hot-swap-pable LRUs. To provide the reliability nec-essary for virtual classrooms, the ATMswitch fabric must tolerate single failures ofswitches and communication channels.Edge LANs should use switches with hot-swappable LRUs so field personnel can pro-vide quick, online repair of devices.

Phase 2: Larger Number of Dedicated LANs with

a Packet Switched Backbone

The second phase eliminates the requirementfor a campus ATM backbone supportingELANs with QoS/CoS provisioning andreplaces it with a campus packet switchedbackbone (Figure 3-2 on page 20). The edgeLANs are still dedicated and overprovisioned,but no longer need be small in number. Themultimedia protocol is H.323.

This configuration is attractive, sincemany educational institutions already have

1199

Studio

• • •

Remote classroom

Remote classroom

Dedicated LAN

Dedicated LAN

• • •

ATM campus

backbone LAN

Dedicated LAN

Figure 3-1. Dedicated Edge LANs Connected by

ATM Campus Backbone LAN

packet switched backbones. Furthermore,since the convergence protocol is IP, packetswitching is a better match for the traffic gen-erated by virtual classrooms than ATM.

The following additional technologies arerequired to support this configuration:• Prioritization of LAN traffic. The campus

backbone must support 802.1p/Q taggingand prioritization, so virtual classroom traf-fic receives the necessary level of service.The dedicated LANs need not support802.1p/Q, since they are overprovisioned.The campus backbone access devices con-necting to the edge networks must partici-pate in the packet tagging activity, however.

• RSVP and RSVP proxy. The campus back-bone must support RSVP so resources canbe reserved to ensure high-priority handlingof virtual classroom traffic. Since RSVP isnot currently supported on many end sys-tems, an RSVP proxy may be required tocreate an RSVP tunnel through the campusbackbone.

• H.323 client on end system. In order forremote PCs to receive the H.323 broadcastvideo, they must have an H.323 client.

• H.323 gatekeeper. Since the number ofedge LANs is no longer small in this config-uration, the video-conferencing services mustsupport a higher level of control. H.323provides the necessary encoding and trans-port services. An H.323 gatekeeper providesthe necessary voice/video call managementservices.

• MCU. An MCU allows remote classrooms/end systems to coordinate their traffic withstudio traffic and with the traffic of otherremote classrooms/end systems.

• Resilient links in campus backbone. TheATM backbone in phase 1 provides a resil-ient fabric. The packet switched backbonethat replaces it must provide similar reliabil-ity, which resilient links and hot-swappableLRUs (from phase 1) provide.

• Efficient multicast routing and filtering atLayer 3. Distribution of the video andaudio content from the studio to remoteclassrooms requires Layer 3 (e.g., IP) multi-cast services. Routers in the campus back-bone must support the Distance VectorMulticast Routing Protocol (DVMRP),which is the least common denominatormulticast routing protocol.

Phase 3: Multi-Application LANs with a

Packet Switched Backbone and Supporting

Video Return

A further generalization of the configurationsin previous phases connects remote classroomsand studios to multi-application LANs (Figure3-3). Shared networking capabilities alloweach LAN to support more than one studio orremote classroom. This flexibility introduces arequirement for QoS/CoS support in the edgeLANs. (Some of the features for this supportare introduced in phase 2 for the core packetswitched backbone and are therefore notrepeated here.)

2200

• • •

Remote classroom

Remote classroom

Dedicated LAN

• • •

Campus packet

switched backbone

Dedicated LAN

Studio

Dedicated LAN

Figure 3-2. Dedicated Edge LANs Connected by a Campus Packet Switched Backbone

An interesting capability enabled byQoS/CoS support in edge LANs is videoreturn. Thus, each remote classroom canreturn to the studio video that is mixed withthe outbound video (e.g., Picture in Picturedisplay). This would be useful for displaying astudent that asks or answers a question as wellas periodic or random monitoring of studentattendance/body language.

An implied generalization in this phase isan increased number of multi-application andstudio LANs. Thus, accommodating scalebecomes an issue. Since the edge LANs nowsupport many applications, end systems mustsupport QoS/CoS signaling to the network inorder to obtain the services necessary to sup-port real-time video and audio. The confluenceof large-scale and QoS/CoS support introducesa QoS/CoS policy management requirementto allow network administrators to controlscarce networking resources according to estab-lished institutional policies.

The following additional technologies arerequired to support this configuration:• QoS/CoS in end systems. End systems must

support application-based packet classifica-tion and either 802.1p/Q tagging, RSVP, orIP ToS tagging. This allows them to signaltheir packet-handling requirements to thenetwork, which is necessary when LANscarry traffic other than real-time video andaudio.

• Policy management of traffic prioritization.Scaling concerns require network adminis-trators to deal with high-level, business-

oriented issues rather than with device-levelcommands and configuration data.

• Bulk configuration of network devices.Scaling also introduces device managementissues that require configuration of deviceson an aggregated basis. When a site hasthousands of network devices, each with alarge number of optional or configurablefeatures, point device management is nolonger effective. Network administratorsrequire the capability to manage devices in groups based on their location and capa-bilities.

• Multicast distribution management andtroubleshooting. Support of a large numberof edge LANs introduces scaling considera-tions for multicast. In order to effectivelyaddress this issue, the converged networkmust support effective multicast distribu-tion management and troubleshooting.

• Fast, convergent routing. When failuresoccur in a large network, the routing proto-col must react quickly to restore connectiv-ity. Routing protocols such as RIP do nothave this characteristic, while OSPF does.Consequently, networks supporting virtualclassrooms should use OSPF.

• Rapid, coordinated fault recovery. Whenparts of a large-scale converged network fail,manual methods of recovery are expensiveand time-consuming. For virtual classroomsupport, converged networks must provide

2211

• • •

Remote classroom

Remote classroom

Remote classroom

Multi-application LAN

• • •

• • •

Campus packet

switched backbone


Studio

Studio


Figure 3-3. Multi-Application Edge and Studio LANs Connected by a Campus Packet Switched Backbone

rapid, coordinated, and automated networkfault recovery.

Phase 4: Multiple Campuses Interconnected

by a WAN

In phase 4, multiple campuses are intercon-nected over a WAN (Figure 3-4). Since muchof the traffic of a virtual classroom will bemulticast, reliable multicast services areimportant. In addition, most WANs do notsupport multicast, so this traffic must be tun-neled. One limitation in this phase is that all

campus networks aremanaged as a single adminis-

trative domain. This limitation isremoved in the next phase.

This phase supports more sophisticatedinteractions between teacher and students,such as use of a shared whiteboard. Since thesecurity of communications over a WAN maybe less than that required for educational ser-vices requiring payment, this phase also intro-duces security technology for protectingcommunications over the WAN. In addition,cost recovery for educational content movedacross a WAN requires the provision ofaccounting services.

The following additional technologies arerequired to support this phase:• WAN QoS/CoS/ToS support. Moving vir-

tual classroom traffic across the WAN

2222

Studio

• • •

Remote classroom

Remote classroom

Remote classroom

Studio





• • •

• • •

Remote classroom

• • •

• • •

Remote classroom

Remote classroom

• • •

Campus packet

switched backbone

Campus packet

switched backbone


WAN

Studio

Studio


Figure 3-4. Multiple Campuses Interconnected by

a Public WAN

imposes bandwidth, delay, and jitter require-ments on WAN services. An ATM-basedWAN has underlying resource reservationmechanisms and signaling capabilities onVC interfaces for QoS. Current FrameRelay–based WANs do not support QoS/CoS controls, so using them for virtualclassroom support requires this enhance-ment. Pure packet-based networks requiresomething like RSVP tunneling for WANQoS/CoS support.

• DVMRP tunneling in WANs or InternetGroup Management Protocol (IGMP)proxying. Current WANs do not supportmulticast and such support is unlikely inthe near future. One way to solve this prob-lem is to tunnel multicast traffic across theWAN using mechanisms such as a DVMRPtunnel. Another approach is to use a broad-cast WAN service, such as that available insatellite networks, and have the router at theuplink point act as an IGMP proxy.

• Policy-based WAN selection. Since videoclassroom traffic will coexist with other traf-fic moved over the WAN between edgeLANs, there must be a way to select theappropriate WAN services for each.

• T.120 support. Using whiteboards requirespoint-to-multipoint services, which are sup-ported by T.120. A T.120 MCU is useful incoordinating multiple users drawing on thesame whiteboard. T.120 can also supportremote camera control, which provides astandard way of synchronizing remote videoreturn data.

• IPsec. Traffic over a public WAN is inher-ently unsecure. Since virtual classrooms arelikely to be a costed service, they must beprotected by a security protocol providingconfidentiality, integrity, and authenticationservices. IPsec is the standard protocol forthese services.


• Security policy management. Interconnect-ing campuses with a WAN introduces prob-lems of network and end system access

control. To control the security threats thisintroduces, sites supporting cross-WAN vir-tual classrooms will require security policymanagement systems, such as the MultilayerFirewall and Network Login, which protectsites against security threats mounted fromremote edge LANs.

• Accounting. Virtual classrooms will be usedfor a variety of purposes, but pay-per-vieweducational seminars and talks will form asignificant percentage of broadcast content.To properly charge for these sessions requiressome sort of accounting technology.

Phase 5: Multiple Campuses and Remote Home

Sites Interconnected by a WAN

The last generalization discussed here supportshome access to the virtual classroom overregional access networks forwarding trafficthrough a WAN (Figure 3-5 on page 24). Theaddition of home access raises a number oftechnology issues. For example, there must besufficient bandwidth to the home to delivervideo and audio content as well as optionallypermit video return. Remote access equipmentservicing the access network customers mustsupport multicast or convert multicast intopoint-to-multipoint traffic.

In this phase, multiple administrativedomains become an issue, since customers areunlikely to allow administration of their com-puting resources by an educational institution.Furthermore, a home may use the services ofmultiple educational offerings, which wouldpreclude management by any one institution.Also, the access networks are managed by thecarrier, not by either the educational institu-tion or the home. Since this phase supportsmultiple administrative domains, it allows themanagement of multiple campus backbonesby more than one administration.

When campuses and homes are intercon-nected, the amount of service-sensitive trafficmoving over the converged network is likelyto increase substantially, and reliability of thenetwork becomes a much more serious issue.Proactive approaches to ensuring network reli-ability become attractive in this phase. Thereliability of a WAN is generally much less

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than that of a typical LAN, so improvementin this area is also critical.

The following additional technologies arerequired to support this phase:• Reliable multicast. To assist in the synchro-

nization of whiteboard modifications so thatteacher and students see the same sharedinformation, this phase supports reliablemulticast. Such service is especially impor-tant when whiteboard traffic moves acrossthe WAN.

• High bandwidth to thehome. Virtual classroom to the

home requires the provision of high-band-width services. This means that access net-works such as cable and xDSL facilitiesmust exist and that the core WAN mustsupport high-bandwidth service to a largenumber of homes.

• Multicast support in remote access equip-ment. In order for homes to participate invirtual classroom sessions, which are distrib-uted as multicast streams, the remote accessequipment must support multicast andeither pass the multicast traffic on to thehome system or convert it to point-to-mul-tipoint traffic.

• IGMP over PPP. In order for home systemsto join a multicast session, they must send

2244

Studio

• • •

Remote classroom

Remote classroom

Remote classroom

Home students

Studio





• • •

• • •

Home students

Remote classroom

• • •

• • •

Remote classroom

Remote classroom

• • •

Campus packet

switched backbone

Campus packet

switched backbone


WAN network

Studio

Studio


Access network

Access network

Figure 3-5. Multiple Campuses Interconnected by

a Public WAN with Home Student Access

an IGMP message to their nearest multicast-capable router. Since home systems will gen-erally connect to the access networks by PPP,network equipment must support IGMPover PPP.

• Video/audio transcoding of virtual class-room content. It is unlikely that studio ser-vices will supply virtual classroom video andaudio data in the same format as all end sys-tems are capable of handling. To accommo-date this, video and audio transcoders mustrun on gateways in the network to performthe necessary conversions.

• IP differentiated services. Since the Internetwill be the WAN in many cases in thisphase, it must support multicast service aswell as some service quality mechanism,such as IP ToS tagging. This requires thedevelopment of the necessary technologyand the adoption and deployment of thattechnology by the ISPs.

• QoS/CoS support across multiple adminis-trative domains. In the previous phase, allnetworks were under the control of a singleadministrative domain. This phase requiresthe coordination of QoS/CoS services pro-vided by multiple administrative domains.Not only must interfacing equipmentunderstand and implement the QoS/CoSpolicies of the domains they interconnect,managing the cross-administrative domainQoS/CoS services requires the developmentand deployment of a federated policy man-agement system.

• Predictive network failure tools. To ensurea high-reliability network service for virtualclassrooms, it is useful to support technolo-gies such as predictive network failure tools.

Case 4: Converged Network Support for

Toll Reduction

A significant shift in telephony service is onthe horizon. Toll traffic that currently travelsover circuit switched networks will be divertedover packet-based WANs, thereby reducinglong-distance service costs. This reduction ispossible due to economies of scale that are dri-ving down the cost of packet switching equip-ment in relation to the cost of circuit switcheddevices. For the purposes of this case study, we

use the term toll reduction to describe thediversion of toll traffic over packet-basedWANs.

The advantages of toll reduction are botheconomic and technical. From an economicperspective, customers receive long-distanceservice at lower cost. Competitive pressure onvoice service carriers by data service carrierswill force voice carriers to offer toll reductionservices or risk a significant loss of marketshare.

Toll reduction will initially be transparentto customers, except for its reduced cost. Inlater stages of toll reduction, carriers will takeadvantage of the converged voice/data net-work to provide value-added services. Forexample, in cooperation with local PSTN ser-vice providers, carriers might offer accountingand billing information to customers over theWeb. They might provide e-mail arrival notifi-cation using LEDs or displays on packet voicehandsets. They could provide online whiteand yellow pages services. They could providemore advanced call management services, suchas displaying the phone number of an inter-rupting call when customers subscribe to callwaiting.

Toll reduction requires voice packetiza-tion, which will occur in carrier equipmentconnected to the local PSTN. Prior to themovement of packet voice traffic across theWAN, the remote termination point for thepacket voice traffic is located. This is accom-plished by translating the destination phonenumber into an IP address, which identifiesthe equipment that will convert the packetvoice into analog form and forward it over theremote PSTN to the call’s destination. Oncecall setup is achieved, the packet voice data isrouted over the intervening WAN, therebybypassing the long-distance circuit switchednetwork.

One advantage carriers enjoy is theiraccess to the voice circuit switched network. Ifthe load on their WAN network reaches alevel at which toll service quality becomesdegraded, the carrier can route the call overthe circuit switched network; this is calledbackhauling. This allows carriers to manage

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their capital expenses by growing the WANpacket network incrementally over time.

Toll reduction is predicated on the capa-bility of WANs to deliver acceptable band-width, delay, and jitter characteristics. Mostcarriers have extensive experience in capacityplanning and understand their load modelswell enough to overprovision their WAN ser-vice. In future offerings, packetized voice maybe carried directly from enterprises over directlinks to the WAN and from small/mediumbusinesses and home premises over broadbandservices such as cable modem and xDSL.Access network providers and enterprise net-work administrators are not as experienced inprovisioning their data networks to provideacceptable voice quality. For these providers,additional access network enhancements maybe necessary for toll-grade service.

Phase 1: Toll Reduction over Existing PSTN

In the first phase of toll reduction, carriers willintercept toll traffic at an H.323 gateway con-nected to a local PSTN and move this trafficover a packet switched WAN, delivering it toan H.323 gateway near the calling party. The

destination H.323 gateway will then place acall over the remote PSTN to the destination(Figure 4-1).

To utilize toll reduction, the customerdials the H.323 gateway, enters a PIN or otherauthentication information to establish hisidentity (for authorization and accountingpurposes), and then enters the destinationphone number. The gateway translates thephone number into the appropriate IP addressand establishes an H.323 session with theH.323 gateway at that address. The remoteequipment then calls the destination phonethrough the local PSTN, thereby establishingthe necessary local circuit switched connec-tion.

Once the call is established, the localH.323 gateway packetizes the voice traffic androutes it over the WAN. At the remote gate-way the packet voice is decoded and sent over

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WAN

H.323 gateway

Carrier

H.323 gateway

PSTN

PSTN

Figure 4-1. Toll Reduction over Existing PSTN Services

the PSTN as normal voice data. The remoteend may decode the packet voice into analogor digital form, using whatever codec standardis appropriate for the local PSTN.

The following technologies are requiredto implement this configuration:• H.323 gateway. Both the local and remote

PSTN connection points must have anH.323 gateway that accepts packet voicedata and decodes it into voice traffic suit-able for sending and receiving over a PSTN.The gateway must provide authenticationand accounting services, perhaps by inter-acting with other services connected to iteither locally or through the WAN. In thisphase, the H.323 gateway will support alimited number of codecs, such as G.723.Finally, the gateway must connect to thePSTN through span lines of sufficient capa-city, such as E1/T1, to handle a significantamount of traffic.

• Directory server. The H.323 gateway musttranslate the destination phone number pro-vided by the customer into the IP address ofthe remote gateway. This service is providedby a phone directory server. In this phase, aproprietary protocol is used for the interac-tions between the gateway and directoryserver.

• Interactive voice response (IVR). In orderto service the customer’s call request, anIVR system is required to guide the callerthrough the appropriate steps (enter PIN,enter destination phone number, etc.).

Phase 2: Toll Reduction with Redundancy and

Sophisticated Call Management

The next phase of toll reduction adds moresophisticated call management facilities andsignificant redundancy (Figure 4-2 on page 28).

Load management of the WAN benefitsfrom technology added in phase 2. To protectthe WAN from becoming congested, anH.323 gatekeeper is added that manages callsestablished through the H.323 gateways toensure that sufficient WAN resources areavailable to service them. If the WAN is over-loaded, the gatekeeper can communicate withan SS7 gateway, rerouting the call to anotherH.323 gateway or over circuit switched long-

distance equipment. Finally, LightweightDirectory Access Protocol (LDAP), a standardX.500 directory services access protocol, isused to communicate with phone directory,authentication, and accounting servers exter-nal to the H.323 gateway. In this phase, theLDAP schemas are proprietary.

Significant redundancy is also added inthis phase with fully redundant H.323 gate-ways and gatekeepers and redundant SS7gateways. The local and remote H.323 gate-ways are supported by a full complement ofgatekeepers, SS7 gateways, and phone direc-tory, authentication, and accounting servers.

The following additional technologies arerequired to support this phase:• H.323 gatekeeper. A fully redundant

H.323 gatekeeper provides basic call man-agement functions for routing calls comingthrough an H.323 gateway.

• SS7 integration with H.323. When a callrequest arrives at an H.323 gatekeeper thatneeds to be rerouted to another gateway, thegatekeeper signals an SS7 gateway, whichpasses on the rerouting information to thePSTN using the ISDN User Part (ISUP)protocol.

• Accounting. In order to recover costs associ-ated with toll reduction calls the carrier mustsupport a billing and accounting service. Twoadditional servers are required: an authenti-cation server and an accounting server. Bothutilize existing carrier functionality by inter-facing to them through an Open DatabaseConnectivity (ODBC) interface.

• H.323 gatekeeper coordination. As tollreduction becomes pervasive, carriers willdeploy multiple fully redundant H.323gatekeepers, which will coordinate withthose in other parts of the carrier network.This requires a gatekeeper-to-gatekeeperprotocol supporting basic functionality.

• Improved H.323 gateway. The deploymentof toll reduction access through cable modemand xDSL access networks is likely to stressexisting H.323 gateway implementations.Handling the increased load requires a morerobust gateway, supporting a larger numberof ports and providing greater reliabilitythan the gateway deployed in phase 1.

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• Fax over IP. Traditional long-distance ser-vice allows customers to fax informationbetween local and remote points. Since faxdata is digital in nature, efficiencies are pos-sible if fax analog data are converted to digi-tal form when moved over the toll reductionWAN.

• Resilient links and hot-swappable LRUs.Not only must the H.323 gateway be reli-able, the underlying communications fabricmust be reliable as well. This requires resil-ient links and LRUs. When links fail, backuplinks must automatically take over the newload. Resilient links provide this capability.When network devices experience failures intheir components, the smallest replaceablepart that contains the failed component (an

LRU) must be swapped out and a correctlyoperating part swapped in. LRUs must behot-swappable; that is, the network deviceshould continue to operate while the LRUis replaced.

Phase 3: Toll Reduction for Enterprise Networks,

Small/Medium Businesses, and Consumers

In the third phase, carriers provide toll reduc-tion services to small and medium businesses,enterprises, and consumers (Figure 4-3).

These customers directly access the tollreduction WAN through cable modem andxDSL access networks or through direct links(such as T1 or analog modem). Access controlin H.323 gateways handling inbound callsfrom direct links and access networks (notshown in the figure) protect the toll reductionWAN from becoming congested by this directaccess traffic.

The following additional technologies arerequired to support this phase:• Broadband access. A cable modem trans-

mission system (CMTS) allows both digitaldata and traditional analog cable channels

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WAN

PSTN

PSTN

Carrier

Redundant

gatekeepers

Redundant

gatekeepers

Redundant

H.323 gateways

SS7 gateway

SS7 gateway

Redundant

H.323 gateways

Directory, authorization,

and accounting servers



Figure 4-2. Toll reduction with Sophisticated Call

Management and Redundancy

to coexist in the same system. Similarly, adigital subscriber loop access multiplexer(DSLAM) in a PSTN central office sepa-rates voice and data, allowing data to berouted over a packet network, thus relievingstress on the circuit switched network.

• Header compression. To ensure efficiencieswhen voice and data are moved simultane-ously over the same access network link,voice traffic is compressed. Header compres-sion complements voice data compressionin the voice traffic data, making voice pack-

ets compact. This is particularly importantfor low-speed lines.

• IPsec. As toll reduction expands from anexclusively carrier-based service to the small/medium enterprise and mass market, thesecurity of voice traffic over the data networkwill become an issue. This will require theconfidentiality and integrity services pro-vided by IPsec.

• Cryptographic policy management. Man-aging IPsec is an arduous task unless there issome help in the form of cryptographic

2299

Enterprise LAN

WAN

Modem

or xDSL

Modem

or xDSL

Carrier

Redundant

gatekeepers

Redundant

gatekeepers

Redundant

H.323 gateways

SS7 gateway

SS7

gateway

Modem

Redundant

H.323 gateways

PC-based

telephone

• • •

• •

•

PSTN

PSTN





Figure 4-3. Toll Reduction Services for Enterprise Networks, Small/Medium Businesses, and Consumers

policy management. This is required in anypractical, large-scale deployment of IPsec.

• IP differentiated services. Support of toll-grade voice service over cable modems,xDSL, and analog modems requires priori-tized handling of packet voice data, whichwill require IP differentiated services inthose networks. Current work in the IETFis investigating use of the Type of Service(ToS) field in IP headers to tag trafficaccording to its urgency, as well as resourcereservation by means of the Resource Reser-vation Protocol (RSVP). RSVP is a signal-ing protocol used for reservation, and ToSbits indicate a desired priority. To imple-ment this priority, there must be mecha-nisms in Layer 3 switches and routers suchas packet scheduling algorithms in routersor 802.1p–compliant priority queuingmechanisms in switches.

• Policy management of traffic prioritiza-tion. Scaling concerns require networkadministrators to deal with high-level busi-ness-oriented issues rather than with device-level commands and configuration data.Carriers supporting toll reduction mustmanage their QoS/CoS resources carefullyin order to achieve the efficiencies requiredin a competitive environment. Policy man-agement is the tool that provides the neces-sary level of control.

• H.323 client on end system. In order fortoll reduction service to extend to the home,PCs and IP-capable handsets must supportan H.323 client.

• H.323 gatekeeper support for bandwidthcontrol. Toll-quality voice requires gate-keeper functionality that admits and routescalls based on network load. This requiresinteraction between the H.323 gateway andnetwork management systems.

• Enhanced gatekeeper-to-gatekeeper inter-actions. Basic gatekeeper functionality pro-vides for call handoff on a per-call basis. Ina large-scale deployment of toll reduction,more sophisticated interactions are necessary.For example, there may be a requirementfor load balancing or fail-over between gate-ways in different parts of a carrier’s network.

• Enhanced SS7 support. When calls origi-nate in PCs or IP-capable handsets, the SS7gateway used to route the outgoing call overthe PSTN must translate certain destina-tions (such as 800 numbers) using theTransaction Capabilities Application Part(TCAP) protocol.

• Capacity planning and better monitoringtools. To ensure that toll reduction trafficreceives adequate service, WAN and accessnetwork capacity must be sufficient to sup-port it. Thus, capacity planning is animportant activity. Since converged net-works are much more complex than exist-ing, data-only networks, better simulationand analysis tools are necessary. In addition,better monitoring tools are required to pro-vide the data necessary for simulations andanalysis.

• Home LANs. The provision of toll reduc-tion will stimulate the home LAN market.Multiple handsets/PCs in the home sup-porting packet voice will allow multiple,simultaneous, outbound calls if there is ahome LAN to move the packet voice trafficfrom the handsets to the access networkconnection point.

• Home LAN QoS/CoS support. To ensurethat voice traffic transiting the home LANreceives the appropriate level of service,home LANs must support an appropriatelevel of QoS/CoS. Since proposed homeLAN technologies are unswitched, MACaccess layer control algorithms for homeLANs must support QoS/CoS objectives.

• ISSLL-LOW. When toll reduction trafficmoves over analog modems, voice and datatraffic will share a common link. Thisrequires the use of a link traffic prioritiza-tion scheme to ensure voice traffic hasprecedence over data traffic. The ISSLL-LOW standard defines such a scheme.

• QoS/CoS in end systems. End systems mustsupport application-based packet classifica-tion and RSVP or IP ToS tagging. This allowsthem to signal their packet handlingrequirements to the carrier and access net-works.

3300

Phase 4: Toll Reduction with Advanced Services

and Standardization

As toll reduction services become common,carriers will begin offering advanced servicesto differentiate themselves from their competi-tors (Figure 4-4). They will offer multi-confer-encing services based on IP multicasting andprovide advanced telephony features such ascall waiting and call forwarding. They willinteroperate with one another, which requiressettlement services to account for callcosts. Carriers will implement least-cost routing functions in their

WAN networks to locate the best H.323 gate-way for a call or to determine when to back-haul traffic. These routing protocols will useload, price, and congestion (among other fac-tors) as input to their routing metrics. Toserve customers who connect to the toll reduc-tion WAN through cable modem and xDSL,carriers will support data created by high-fidelity codecs at these customers’ premises.

In addition to these advanced services,carriers will move away from proprietary

protocols for toll reduction andmove toward international

3311

WAN

Modem

or xDSL

Modem

or xDSL

Carrier

Redundant

gatekeepers

Redundant

gatekeepers

Redundant

H.323 gateways

SS7 gateway

SS7

gateway

Modem

Redundant

H.323 gateways

PSTN

PSTN





Enterprise LAN

Soft PBX

PC-based telephone

• • •

POTS

Figure 4-4. Toll Reduction with Advanced Services and Standardization

standards, which should emerge during thisphase. They will migrate to a standard, full-featured, gatekeeper-to-gatekeeper protocol,utilize standardized LDAP directory serviceschemas, and install and use standardizedQoS/CoS services in their WAN networks.

The following additional technologies arerequired to support this phase:• Soft PBX. The origination of multiple out-

bound calls from an enterprise, small/medium business, or home does not requireadditional equipment. Supporting multipleinbound calls is possible as well, but suchservice requires a soft PBX. This can be pro-vided either by access network head-endequipment, by the carrier, or by equipmentsited within a customer’s premises. The softPBX will also handle calls traversingpremises POTS service.

• MCU. Multiconferencing support requiresan MCU, which coordinates separate voicestreams by multiplexing them into a singleaggregated flow. An appropriate MCU isprovided in the T.120 standard.

• Efficient multicast routing and filtering.To implement multiconferencing, tollreduction WANs and access networks mustsupport efficient multicast routing and fil-tering. This increases their efficiency whenhandling multiconferencing traffic.

• Multicast distribution management andtroubleshooting. Support of an arbitrarynumber of multiconferencing participantsintroduces scaling considerations for multi-cast. In order to effectively address thisissue, toll reduction must support effectivemulticast distribution management andtroubleshooting.

• Standardized LDAP schemas. To maintainefficiencies, carriers will standardize theLDAP schemas that are used to manage

phone directory, authentication, andaccounting services.

• Advanced telephony services. Carriers willimplement such advanced telephony ser-vices as call waiting and call forwarding fortheir toll reduction offerings.

• Least-cost routing. To institute efficienciesnecessary to meet increasing competition inthe toll reduction market, carriers will designand implement least-cost routing mecha-nisms, which take into account load, price,and congestion when formulating routes.

• Enhanced codecs support. As more cus-tomers use high-bandwidth access servicesdirectly connected to the toll reductionWAN, they will increase the fidelity of theirvoice service by employing more advancedaudio codecs. Carriers will improve theirtoll reduction services to support this classof traffic.

• Settlement services. Interexchange carrierswill offer settlement services to their carriercustomers so that calls can transit multiplecarrier networks.

Conclusion

The case studies presented in this paper offer asuggestion of the wide range of applicationsand business environments that will benefitfrom network convergence in the comingyears. But in order to realize the benefits ofconvergence—cost savings, improved networkcontrol, increased flexibility and functional-ity—new capabilities are required in the net-work infrastructures. A phased deploymentcan deliver benefits at each incremental step.Whether or not an organization’s immediateplans include convergence, today’s infrastruc-ture investment should include features andcapabilities that position the network to sup-port these applications in the future.

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To learn more about 3Com products and services, visit our World Wide Web site at www.3com.com. 3Com is a publicly traded corporation (Nasdaq: COMS).

© 1998 3Com Corporation. All rights reserved. 3Com is a registered trademark of 3Com Corporation or its subsidiaries. AppleTalk is a trademark of Apple Computer. IPX is a trademark of Novell. PointCast

is a trademark of PointCast. SAP is a trademark of SAP AG. Other brand and product names may be trademarks or registered trademarks of their respective owners. All specifications are subject to change

without notice.

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Converged Networks Case Studies · Converged Networks Case Studies Converged networking is an emerging technology thrust that integrates voice, video, and data traf-fic on a single

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