VDSL, at rates of 25 Mbps or higher, requires a distribution point closer to the subscriber than a present-day telephone office. Its potential penetration is difficult to predict and depends a great deal on the success and competitive implications of cable-based data services.
24. Cable interactive access services are just beginning to be commercially available. It is a fairly safe prediction that by mid-1999 millions of cable subscribers will be offered this service.
25. It is a challenge to the cable industry to make subscription and service provisioning simple and fast, and some standards interoperability questions discussed later, such as "plug and play" of digital set-top boxes, remain to be resolved.
26. The conventional "best-effort" IP service does not require any special capabilities from the core network, but the new QoS-conscious IP services and, of course, ATM do. The core network must deploy technologies such as edge switches and access multiplexers that aggregate traffic arriving under various communications protocols, and must closely control QoS parameters for multiswitch routings.
27. For the modem-based ISPs this implies higher rates, but the cable model may allow "always-on" capability without major increases in hardware investment.
28. CORBA (Common Object Request Broker Architecture), standardized by the Object Management Group, is a leading candidate for a universally accepted architecture, although there are other distributed object systems proposed by major software vendors, such as Microsoft's ActiveX.
29. Transportable software and object broker systems such as CORBA are complementary more than competitive. CORBA provides important object location and management services and facilitates use of existing applications software by wrapping applications (written in whatever computer language) in CORBA objects with standard IDL interfaces. The Java virtual machine requires new applications, all in the Java language, and applets may not execute as efficiently as software written for the underlying operating system, but it facilitates the movement of executable software, with appropriate security constraints, with the benefits outlined above. There are many examples now of CORBA-based systems in which CORBA objects are invoked by transportable Java applets.