The Broadband Infrastructure

We are in an era of new networks that we loosely term next-generation networks. Data traffic in these networks is equal to or surpassing voice as the most mission-critical aspect of the network. Remember that when all the traffic is ones and zeros, everything is data, and voice is just another data application. Integration of voice, data, and video without protocol conflicts greatly simplifies the migration of legacy communication systems and network applications to next-generation transport technologies. The undeniable appeal of interactive multimedia applications, content, and programming also signals the need for a convergent infrastructure that offers minimum latencies to ensure the responsiveness that customers need.

Traffic is growing at an alarming rate. More human users, more machine users, and more broadband access are all contributing to the additional traffic. Established carriers and new startups are deploying huge amounts of fiber-optic cable and wireless broadband, introducing new possibilities, and optical technology is revolutionizing the network overall. This new era of abundant capacity stimulates development and growth of bandwidth-hungry applications and demands service qualities that can allow control of parameters such as delay, jitter, loss ratio, and throughput. Bandwidth-intensive applications are much more cost-effective when the network provides just-in-time bandwidth management options. Next-generation networks will provide competitive rates due to lower construction outlays and operating costs.

Converging Public Infrastructures

Public infrastructures are converging on a single set of objectives. The PSTN looks to support high-speed multimedia applications, and therefore it also looks to provide high levels of QoS and the ability to guarantee a granular diversification of QoS. The PSTN has traditionally relied on a connection-oriented networking mode as a means of guaranteeing QoS, initially via circuit switching and now incorporating ATM as well.

The public Internet is also intended to support high-speed multimedia applications, and it must deal with providing QoS guarantees. But we are investigating slightly different options for how to implement this in the Internet than in the PSTN (see Chapter 8, "The Internet and IP Infrastructures"). Included in the IETF standards are Integrated Services (IntServ), Differentiated Services (DiffServ), and the new panacea, Multiprotocol Label Switching (MPLS), all of which are described later in this chapter.

Broadband Service Requirements

For next-generation networks to succeed, they must offer a unique set of features, including the following:

• High speed and capacity All next-generation networks must offer very high capacities, today measured in terabits per second (1Tbps = 1 trillion bps) and already moving into the range of petabits per second (1Pbps = 1,000Tbps). Higher-bandwidth broadband access (such as 100Gbps) will drive the need for additional core bandwidth, and discussions are beginning about network cores needing to support capacities measured in exabits per second (1Ebps = 1 billion Gbps) when 100Gbps broadband access becomes a reality.
• Bandwidth-on-demand Next-generation networks must be able to provide or provision bandwidth-on-demand, as much as is needed, when it is neededunlike today's static subscription services.
• Bandwidth reservation Next-generation networks must be able to offer reserved bandwidth, so that when you know you will need a high-capacity service for streaming media, you can reserve the network resources so that they are guaranteed at the time and place that you need them. Mind you, the major application for reserved bandwidth is videoconferencing; for other applications, most people don't plan ahead.
• Support of isochronous traffic Isochronous traffic is time-bounded information that must be transferred within a specific time frame, and it therefore has a low tolerance for delay and loss.
• Agnostic platforms Agnostic devices support multiple data protocols (e.g., IP, Frame Relay, ATM, MPLS) and traffic types (e.g., voice, data, and video), so that all traffic can be aggregated and administered at a single point.
• Support for unicasting and multicasting In unicasting, streams from a single origination point go directly to a single destination point. In multicasting, streams from a single origination point flow to multiple destination points. This reduces traffic redundancy by limiting the access to a selected group of users.
• QoS As discussed later in this chapter, next-generation networks must provide variable QoS parameters and ensure that those service levels can be guaranteed and that service-level agreements (SLAs) can be honored.

A number of developments have been key to allowing us to deliver on this set of requirements. One important area is photonics and optical networking. Chapter 11, "Optical Networking," describes the revolution that started with the ability to manufacture glass wires; went further to introduce erbium-doped fiber amplifiers (EDFAs); grew to encompass Wavelength Division Multiplexing (WDM), Dense Wavelength Division Multiplexing (DWDM), and Coarse Wavelength Division Multiplexing (CWDM); and is proceeding to introduce new generations of high-performance fiber, reconfigurable optical add/drop multiplexers (ROADMs), optical cross-connects, optical switches and routers, and the optical probes and network management devices that are very important for testing networks. We're looking forward to a future of end-to-end optical environments.

A number of broadband access technologies, both wireline and wireless, have been developed to facilitate next-generation networking. Chapter 12 covers these options, which include the twisted-pair DSL family; hybrid fiber coax (HFC) alternatives that make use of cable modems; fiber-to-the-node and fiber-to-the-home/fiber-to-the-premises; broadband wireless, including direct broadcast satellite, Wi-Fi, and WiMax; Free-Space Optics; and innovative new uses of powerlines to support high-speed communications. As discussed later in this chapter, multiservice core, edge, and access platformsincluding the IP Multimedia Subsystem (IMS), multiservice provisioning platforms (MSPPs), and the MPLS architectureare being developed.