Remote Dial-in Access Applications and Virtual Private Networks

Remote dial-in access (or simply remote access) is the way many users access the Internet. It is also used in the telecommuting service whereby corporate road warriors and those who work at home access corporate IP networks. On the surface, both types of access look the same. In fact, the very procedure (dialing a number and entering a password) and the end-user equipment necessary (a telephone line and a modem) to accesses the network are identical. At least one important piece of the underlying technology pertinent—carrying IP packets over PSTN lines—is also present in both types of services. There are significant differences as well, with underlying issues, between accessing the Internet privately (through an ISP) and accessing corporate networks. We treat remote dial-in access simply as part of VPNs, discussed in a section that follows.

One problem inherent to data access from home via a telephone line is that the line will be busy for the duration of the data access session. The busy line has posed a number of problems for households with only one telephone line. One solution, perhaps most typical for many American households, is to have two lines. Another is to have ISDN installed (which is still rather expensive). Yet another solution is to use a special modem that splits the line into data and voice. Then, of course, there are service solutions (such as the Internet call-waiting service). As it becomes more available, the xDSL technology will eliminate the need to dial at all!

With remote access, in its oldest form (See Figure 1), a user simply established a point-to-point link between a terminal (connected to a modem) and a remote computer (also connected to a modem).

Figure 1: Terminal-to-host dial-in access.

As PCs became household appliances, the terminals virtually disappeared. PCs are presently used both as terminals (with so-called shell accounts, provided by both ISPs and corporations) and IP hosts. Even with the shell accounts, users get access to the Internet (including the Web) through a host. However, with shell accounts, the graphical interface that has made the World Wide Web so popular is not available.

To act as a host, a PC typically dials in the remote access server (RAS) of an IP network (as depicted in Figure 2, where the PSTN path happens to traverse three telephone switches). What actually distinguishes a host equipped with a set of modems from an access server? The answer is simple: A RAS is an IP router equipped with a set of modems or digital signal processors capable of terminating a call. Remote access servers are sometimes called remote access concentrators. Although both terms are used interchangeably, some people use the latter term only when referring to large multiservice modules, which have access to asynchronous transfer mode (ATM) networks, X.25-based public data networks (PDNs), and other non-IP networks (hence the term multiservice).

Figure 2: Host-to-host dial-in access.

Having just defined a RAS, we should note that the data network access may be not so remote. First of all, an enterprise or ISP can place several access servers (see Figure 3) so that users in different geographic areas can call local numbers. Second, remote access can also be outsourced. A remote access outsourcing application uses the existing network infrastructure of a larger service provider to offer remote access termination service to enterprise customers. Then, with the Internet offload application (also called Internet call diversion), the very edge (that is, the central office switch) of the PSTN can recognize the call (based on the dialed number, for example) as a data call, and terminate it at a colocated or even internal access server. From there the call is passed to the appropriate ISP (or enterprise) network (Figure 3).

Figure 3: Internet offload.

The Internet offloading application has been created out of urgency. The ever increasing use of Internet access has manifested a serious problem with the PSTN: The duration (or holding time, in telephony parlance) of such data calls far exceeds what telephone companies expected from voice calls (and consequently engineered their network for). As a result, more and more real (voice) calls became blocked throughout the PSTN, and the problem became so serious that specialized solutions to offload the data traffic from telephone switches to data networks, were urgently requested by telephone companies. The problem warrants special attention here if only because it was among the first instances where data-over-voice applications required significant restructuring of the PSTN. What is especially interesting is that even the old PSTN paradigm—the more calls and the longer they are, the better—has changed! The danger of these long data calls blocking voice traffic became so serious that the telephone companies decided they did not want data calls in the voice network. This conflict has created a classic example of PSTN-Internet integration by necessity.

Web-Based Service Customization

Service customization is the activity through which a subscriber to a communications service can change a subset of parameters. These parameters typically define the runtime behavior of the service. For example, for the freephone service, subscribers should (at minimum) be able to set the following parameters:

• The time of day when the calls are to be directed to a particular destination number

• The day of the week when the calls are to be directed to a particular destination number

• The destination number where the calls from a certain area code should terminate

Another example is the follow-me service, where customers can prescribe how they wish incoming calls to be directed according to their schedule and availability (by using similar parameters).

Traditionally, to customize a communications service, particularly one that is delivered over the PSTN, a subscriber would need to have a special networking arrangement with his or her service provider to receive direct, secure access to customer records. Before the proliferation of the Internet, there simply was no infrastructure that would allow small customers to access such information. Now, telecommunications companies can move the customizable parameters to (properly secured) IP hosts that are accessible by subscribers.

When it is easy for subscribers to customize the services so that they can be called when they wish, the telephone companies that serve them naturally complete more calls and thereby improve profits. Since services offered are Web-based, the potential customer base extends worldwide.

PINT Services

The basic PSTN/Internet Internetworking (PINT) services (RFC 2458) include click-to-dial-back, click-to-fax, click-to-fax-back, and voice-access-to-content. The common denominator of PINT services is that they combine the Internet applications and PSTN telecommunications services in such a way that Internet applications can request the PSTN telecommunications services. Further, the Internet is used for nonvoice interactions, while voice (and fax) is carried entirely over the PSTN. An example of such a service is the combination of a Web-based Yellow Pages service with the ability to initiate a PSTN call between a customer and a supplier in the manner described later. Note that the word click in some of these services should not be taken literally and construed as a prescribed way for invoking the services. It is rather used to underline that service initiation takes place on the Internet, where pointing and clicking are the most prevalent user actions.

Click-to-Dial-Back
With the click-to-dial-back service, a user requests (through an IP host) that the PSTN call be established with another party. As in several other examples of PSTN/Internet hybrid services, an important prerequisite for using this service is that the user have both voice access to the PSTN (via a telephone terminal) and data access to the Internet (via a PC).

A typical example application of this service is online shopping: A user browsing through an online catalog clicks a button, thus inviting a call from a sales representative. Note that (as is the case with the all-PSTN freephone), flexible billing arrangements can be implemented on behalf of the service provider. In addition, the PSTN can route the call depending on the time of day, day of week, availability of agents in different locations, and so on.

Click-to-Fax
With click-to-fax service, a user at an IP host requests that a fax be sent to a particular fax number. This service is especially meaningful when the fax is to be sent to someone who has only a fax machine but no access to the Internet. Consider as an example a service scenario in which a Web user makes a reservation for a hotel room in Beijing from a travel service page containing hotel information for major cities around the world. Suppose a specific Beijing hotel chosen by the user does not have an Internet connection but has a fax machine. The user fills out the hotel reservation form and then clicks a button to send the form to the service provider, whose equipment then generates a fax request and sends it together with the hotel reservation form to a PSTN node. Upon receiving the request and the associated data, the PSTN translates the data into the proper fax format and delivers it to the Beijing hotel.

Click-to-Fax-Back
With click-to-fax-back service, a user at an IP host can request that a fax be sent to him or her. Now the traveler of the previous example can request confirmation from the Beijing hotel. Another useful application of the service is when the size of the information that a user needs to retrieve is so large that downloading it to the user’s PC over the Internet would require a long time and too much disk space.

Voice-Access-to-Content
With voice-access-to-content service, a user at an IP host requests that certain information on the Internet be accessible (and delivered) in an audio form over the PSTN, using the telephone as an informational appliance. One application of this service is providing Web access to the blind. (This may require special resources—available in the PSTN—to convert the Web data into speech.) A variant of this service is that the telephone is used to initiate as well as to retrieve the content. In other words, the user requests through the telephone with voice commands that certain information on the Internet be delivered in an audio form over the PSTN and heard on the telephone.

Cisco IP Telephony Applications

Cisco has developed software solutions to enhance their IP telephony solutions. IP telephony applications allow Cisco to augment their IP telephony hardware with features and services to provide an even more viable solution.

Cisco Web Attendant

Cisco WebAttendant is Windows Web-based TAPI software that allows the user to receive and dispatch calls from any IP telephone on the network. WebAttendant allows the IP phone to interface directly with the CallManager to direct calls and to monitor the status of lines, much like a traditional receptionist console. WebAttendant offers many of the same features of traditional PBX systems such as hunt groups and multiple attendant consoles.

WebAttendant is included in the basic CallManager package. It can scale to meet the size of almost any IP telephony infrastructure. A single WebAttendant console can monitor up to 26 calls at a time. A single CallManager cluster utilizing WebAttendant can support up 32 hunt groups with 16 members per hunt group. Also, a cluster can support up to 96 WebAttendant consoles, which means support for up to 512 (96 consoles x 26 calls) calls at one time.

Internet Communications Software

Internet Communications Software (ICS) is a suite of five tools for service and application providers to further gain the benefits of IP telephony.

• Network Applications Manager (NAM) A management console that enables utilization of Automatic Call Distribution (ACD), Intelligent Contact Mangement (ICM), CIS, and IP Contact Center (IPCC).

• Automatic Call Distribution Part of NAM, it reroute calls to different customers serviced via the same CO.

• Cisco IP Contact Center Allows call centers using IP telephony to receive regular POTS calls as well as IP telephony calls.

• Intelligent Contact Management Directs and relays customer contact information between resources such as Web, voice, and e-mail.

• Customer Interaction Suite Allows corporations and service providers to interact with their customers on the Internet or network in real-time. Four components: Cisco Media Manager, Cisco Media Blender, Cisco E-Mail Manager, and Cisco Collaboration Server: