Session Eight:
Network Services

Lecture Notes

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Lecture 8  Network Services

The competitive strategy of the various players in telecommunications is based upon technology. All of them must offer robust, reliable services that customers want. If they were each building a network from scratch, they might make decisions about which media to employ, which processes to develop, and which services to offer based purely on market economics.

But they must all make the transition from "where we are now" to "where we want to be." So many make technological decisions in part based upon the types of network services which have evolved in the past and which customers have come to expect, as well as making assumptions and investments about new technologies currently coming on line or becoming economically viable for the first time. The strategic investments they make in technology are, to some extent, a major gamble for each of them. But the basic framework all must follow is to provide a core of network services for both voice and data, increase bandwidth and speed, and provide for reliable alternative technologies to compete against the rest of the industry.

Network services today are provided by and driven by three factors. First, the history of the public switched network has produced a number of common, robust technologies upon which many are dependent. The public switched network is a national strategic asset. Dependence upon it for communications in the event of disaster or emergency is so great that its protection is one of the top priorities of national defense. The overwhelming majority of services rely on the public switched network to be transacted, including voice, fax, and dial-up modem connections.

Second, specialized network services are growing to support customer desires and increase carrier profitability. Dedicated services are permanent links between two locations. They may be created by either hard-wiring a connection directly between and among two or more locations or by creating a so-called circuit switched "virtual private network" or VPN. As indicated in the Dodd text, the distinction between a switched connection and a dedicated leased line service is whether the call must be dialed and switched at the central office.

Third, the increase in applications in data and video is producing enormous pressure to create greater capacity for broadband services. If you drive around Northern Virginia these days, you will notice an enormous amount of work going on to increase the capacity of wireline connections using glass fiber. Sheafs of 18-24 cables each containing 80 or more pairs of fiber are being laid. This increase in capacity foreshadows such enhanced series as full motion real time video and video on demand, as well as dramatic increases in speed and capacity for data transfers. In the meantime, a number of other technologies are being deployed, such as ISDN, DSL, frame relay, and ATM to provide enhanced services to customers selecting those services.

 

 

 

 

 

The public network has embedded in it three broad types of service. These are switched services, dedicated services (or private lines), and network intelligence and signaling.

 

Since the investment made by the incumbent local exchange carriers in copper lines is so great, potential local exchange competitors must determine how to duplicate the access and the capacity of this embedded investment without having to pay too much for the access. It is estimated that each potential competitor would have to invest $500 billion or more to duplicate the wires currently in existence. This cost is, of course, prohibitive, and has stimulated potential competitors to look at alternative technologies to reach the "last mile". Conversely, because of that investment, it is almost impossibly expensive for the incumbent local exchange carrier to replace all of the existing copper with other transmission media to every household. As you are aware, the big players are investing heavily in alternative technologies, such as AT&T’s investment in cable and MCI WorldCom’s investment in "ricochet" wireless modems are examples of investment n alternative technology. But let us try to understand more fully the capability and limitations of the existing technology, and then review currently available alternative or advanced services.

The local loop is primarily made up of twisted copper wires, with some fiber optic cable. The critical enabling technology for enhancing service over these wires is digitization. First developed in the 60’s, digitization has made the network more efficient. Analog services continue to be provided. To increase capacity and speed to residential and small business customers, most local exchange companies now provide ISDN and DSL services. Cable TV, and wireless offer the other basic service alternatives.

Common channel signaling first appeared in the mid-seventies. It is a means of overlaying the switched network with a separate digital packet data network. Slide 4 It is an out-of-band method that began as a way to run the network more efficiently and evolved into a basis for intelligent networks.

 

 

Signaling System 7 (SS7) is the signaling protocol. Slide 5

SS7 operates as the signaling system which manages the PSTN.  It is, for example, the basis for measuring call duration from one network to another, and hence to provide critical billing information. It is the basis for global "roaming" for wireless calls, toll free calls, and other enhanced services from one carrier to another, or from one country to another. It is the basis for being able to reroute traffic in the event of an emergency, such as the Taiwan earthquake.

 

 

 

 

 

 

A variety of specialized network services increase speed and capacity. Review the chart on page 160 of Dodd and Slides 7-12 to compare the essential technology and capacity of these services.

 

Notice that price and capacity are strongly tied together when using these services. As capacity increases, price increases steeply. Most users must balance traffic needs with price. The high end services are not, so far, scalable downward to allow small users to gain large increases in bandwidth at affordable prices. But this is an area where competition will increase rapidly, since market demand exists, but currently lacks the volume necessary to warrant the payment of high fees to install and operate high speed, high capacity connections. New entrants into local exchange markets are gearing up for providing such low cost, high capacity services. ILECs are building out improved networks to prevent losing customers when the CLECs enter their service territories.

The IEEE recently conducted a workshop at Cornell University on anticipated telecommunications needs for the 21^st century and developed a number of plausible scenarios. Basic to their assumptions were a business and residential demand for broadband information rates of 100 Megabits per second to the desktop. They also assumed that the network would support multiple applications. A high definition television (HDTV) program, for example, would be delivered at 20 Mb/s, with households wanting access to several channels simultaneously, from a menu of perhaps three hundred channels. Other desired services might include videoconferencing or interactive digital video on demand.

This "typical" household of a 2010 is probably not that far off the mark. But the bandwidth demand is dramatically higher than network services currently available at any price. While certain government applications can currently operate at the OC-3 rate – 155 Mb/s – a dramatic increase in capacity will be necessary to meet the anticipated residential and business demand. Compare that OC-3 rate with an effective rate on ISDN of 1.5 Mb/s, 6 Mb/s on DSL and the degree of the need to increase capacity to the home becomes obvious. The rates of even the highest capacity systems are still slow and primitive compared to the IEEE scientists’ expectations and what is currently deployed.

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