PDF of this tutorial"The remote access market is expected to more than double from $3.8 billion in 1998 to $7.7 billion by 2003. Voice and data convergence creates a new category of remote access—VoIP–enabled RAS—and this segment is forecasted to realize at 81-percent compound annual growth rate (CAGR) from 1999 to 2003."
—Brian Baldwin, International Data Corp.
There is a great deal of talk about high-speed broadband access to the home via technologies such as digital subscriber line (xDSL) and cable modems. The reality is that while these technologies are beginning to be deployed, the vast majority of us still can only obtain plain old telephony service (POTS) dialup modem access for our connection to the Internet and corporate enterprise. Thus, the dialup modem market continues to grow to support ever-increasing Internet access demands.
With the number of people worldwide accessing the Internet from home nearing 100 million and climbing fast, remote access servers (RASs) are likely to enjoy continued strong demand in the years ahead. With the global Internet explosion just dawning in many parts of the world, the figures indicate that hundreds of millions of Internet users will be counting on dialup access well into the future (see Figure 1).
Figure 1. Worldwide Internet Users 1996—2003
Projected number of Internet users (measured in millions)
Source: International Data, Corp., 1999
Making these numbers even more compelling for equipment providers is the emergence of VoIP. Service providers have traditionally been focused only on providing dialup modem Internet access to their customers. However, with the convergence of voice and data networks, service providers now desire to add value-added telephony services, using VoIP and fax-relay technologies as a means of generating new sources of revenue. ISPs, who may feel the particular squeeze of commodity-priced Internet service, are likely to exploit voice-over–Internet protocol (VoIP)–enabled RAS platforms to provide revenue-generating telephony services with a minimal infrastructure investment.
These services have grown to include VoIP and fax relay for consumers, home offices, and telecommuters, as well as virtual private networks (VPNs) for enterprises with many mobile employees or small branch offices. This array of services represents a significant expansion for the role of RAS platforms from their early use solely as data connections for individual users. As a result, the RAS equipment market is transitioning from modem-only to universal port (voice, fax, and modem). It should be noted that even when high-speed access services such as xDSL and cable modems become available, these services must still support dialup modem services to the user to emulate traditional POTS services fully. Service providers desire to have one set of RAS equipment that can support voice, fax, and data on a call-by-call basis. In addition, this equipment must be able to scale to new heights with regard to overall channel capacity to meet increasing Internet growth.
The RAS equipment market has traditionally been divided into two segments: enterprise and infrastructure. To support a remote workforce (e.g., sales offices, telecommuters, and business travelers), corporations install enterprise RAS equipment to allow their employees remote access to the corporate local-area network (LAN). With the ubiquity of the Internet and the growing acceptance of tunneling programs and firewall security, more and more corporations are addressing their remote access needs by allowing their employees to connect to the corporate LAN through the Internet via ISPs with local points of presence (PoPs). This, combined with the proliferation of home Internet access as more and more households get connected to the Internet, has created a growing demand for very high-density infrastructure RAS equipment capable of supporting thousands of connections in a single rack. The increasing scalability of RAS platforms is even enabling many service providers to wholesale Internet access and Internet telephony service to other ISPs. This low-margin, high-volume business is perfectly suited for next-generation universal ports that offer unprecedented price and performance per channel.
Enterprises are also continuing to deploy RAS systems. Though most industry analysts agree that growth in this market sector will not keep pace with growth among service providers, the increased acceptance of telecommuting, combined with the growing use of the Internet overseas by small businesses, means that the enterprise should remain a strong market for the foreseeable future.
To meet these demands, equipment manufacturers must provide next-generation RAS equipment that offers very high-density, low-power, and low-cost-per-channel solutions that are software-defined to facilitate feature updates and to provide strong network management remote debug capabilities. These platform needs are enabled by a new generation of digital signal processors (DSPs) that make it possible to run multiple channels of modem, voice, and fax in the same DSP while significantly reducing the cost and power per port and increasing the overall channel density of the solution.
Major network-equipment providers today offer a wide range of RAS systems, including some that are touted as VoIP–enabled. This equipment is in use by service providers of all sizes as well as enterprise IT departments offering remote access to employees. While technically speaking some of today’s RAS platforms support VoIP, the truth is these first-generation VoIP–enabled RAS platforms are highly inefficient implementations lacking important software features and often require separate hardware modules within an equipment rack to support modem, voice, and fax services. This requires a priori allocation of hardware resources based on anticipated service needs. As a result, this equipment does not offer an optimum solution with regard to cost and features offered. Figure 2 illustrates the use of a remote access server (RAS; also called a remote access concentrator) to terminate nearly every type of fax, modem, and voice call, and prepare it for transmission over a packet-switched network.
Figure 2. Remote Access Server (RAS)
There are three significant limitations of current RAS equipment: channel density, power consumption, and processing capability. The combination of these three shortcomings will soon render older RAS equipment useless for many of the newer applications mentioned earlier, including VoIP, fax relay, VPN, and access wholesaling.
Channel Density
With space at a premium inside central offices (COs) and data centers, as well as inside the call-processing equipment itself, channel density is very important. Channel density is essentially the number of call channels that can fit into a rack of equipment.
Underscoring the importance of channel density is the typical carrier equipment-refresh cycle. RAS platform providers develop products on refresh cycles of anywhere from nine to eighteen months, and they expect channel density at least to double during each cycle. The resulting increase in capacity not only enables equipment to scale dramatically, it can lower the cost per channel by as much as fifty percent. Traditional RAS platforms offer several hundred modem channels per rack while next-generation RAS platforms will offer several thousands of universal port channels per rack.
Power Consumption
In a massively scalable environment, operating 24x7x365, small variations in power consumption can have a great impact on service providers. First, power is a utility that must be sourced. The cost is pure overhead that moves straight to the bottom line. Second, power consumption is also directly related to heat. Sensitive electronic equipment requires a temperature-controlled environment. This could mean even greater utility costs should external cooling measures become necessary. Third, the network equipment building standard (NEBS) is a Telecordia standard required by carriers and service providers that sets limits on power consumption for a variety of safety and operational reasons.
The goal for equipment manufacturers is to offer the most number of channels in a seven-foot rack without exceeding power consumption allocated for the rack. This may be on the order of 1000 to 1500 watts for the entire rack, including common equipment. Most solutions today tend to be power-limited rather than board space–limited. As service providers evaluate next-generation RAS platforms, the power budget will shrink by about 50 percent and is expected eventually to dip down to 10 milliwatts per channel.
Processing Power
DSPs used in first-generation RAS modem implementations could only handle a single modem channel each. Density improvements were obtained by implementing multiple chip modules (MCMs), which placed multiple DSPs in a single chip, thereby increasing channel density. Newer standards and universal port features place additional demands on processing power per channel as well as program and data memory per channel. To meet the density and power objectives, more powerful and efficient DSPs are required.
