Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-11-10
2002-03-26
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S401000, C379S221010
Reexamination Certificate
active
06363065
ABSTRACT:
BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
The invention relates to apparatus, and accompanying methods for use therein, for a telephony gateway intended for use, e.g., paired use, at opposite ends of a data network connection, in conjunction with at each end, e.g., a private branch exchange (PBX) for automatically routing telephone calls, e.g., voice, data and facsimile, between two peer PBXs over either a public switched telephone network (PSTN) or a data network, based on, among other aspects, cost considerations for handling each such call and called directory numbers, monitoring quality of service (QoS) then provided through the data network and switching (“auto-switching”) such calls back and forth between the PSTN and the data network, as needed, in response to dynamic changes in the QoS such that the call is carried over a connection then providing a sufficient QoS.
2. Description of the Prior Art
Over the past century, telephone communications have become rather ubiquitous as the public switched telephone network (PSTN) has expanded into increasingly rural and other remote areas of the country, thus affording nearly universal telephone access. The PSTN provides real-time circuit-switched connections between caller and called parties, i.e., it establishes a continuous real-time link between caller and called locations, the latter often being specified by a string of digits entered by the caller; maintains that connection for the duration of a telephone call and then tears down that connection once that call terminates.
While basic plain old telephone service (POTs) connections typically provide continuous high quality analog connections, suited for voice, facsimile and relatively low speed data, such connections, based on their toll charges, can be expensive to use. Telephone companies frequently price these connections based on distance and time, i.e., a distance between the caller and called locations and duration of each call. Over the past few years in the United States, competition among regional and long distance telephone companies has existed and is intensifying, so much so as to effectively, in many instances, reduce telephone toll charges. However, such competition is only now emerging in many foreign countries. Further, various foreign governments have set relatively high interconnection tariffs to protect their local telephone companies, which are frequently governmentally regulated monopolies, from competitive pricing pressures arising from foreign carriers. Consequently, while telephone charges, on a per minute basis, are relatively inexpensive in the United States, the same is not true for telephone calls within and between foreign countries. In that regard, international calls between one country and another, such as the United States, can be rather expensive.
For many types of communication, such as data, continuous real-time switched connections, provided by the PSTN, are simply not necessary, given, e.g., relaxed latency restrictions for data, and are too costly.
Hence, within the last decade, private packet networks (commonly referred to as private “data” networks) have experienced phenomenal growth as organizations, particularly those with computer and other digital equipment stationed at disparately located offices, sought cost-effective methods of communicating digital information between these offices. For ease of use and to accommodate as wide a universe of currently available network equipment and computer software as possible, these networks are generally designed to embody Internet Protocol (IP) based routing (which is the same methodology used in the Internet).
Though initial costs associated with implementing a private data network can be significant, average per use charges incurred through use of such a network tend to be considerably less than the toll charges for similar carriage, in terms of an amount of information being communicated, associated with the PSTN and hence, if the private network is sufficiently well used, can provide substantial cost savings to its owner as compared with equivalent use of the PSTN.
During the course of designing a private data network, various long-haul communication links that underlie the network are often chosen to provide bandwidth which, to accommodate anticipated growth, greatly exceeds current usage requirements. A common result of this is that many organizations, which have private data networks in operation, find themselves with significant amounts of unused (excess) installed bandwidth, which they have already built into their cost structure, available on their networks. Hence, some amount of additional traffic can be carried over this available bandwidth at what is, for all intents and purposes, essentially no additional cost. However, bandwidth is ephemeral: it is either consumed or not; it can not be stored for future use and hence, if not used when it is available, is simply wasted.
Those organizations that have implemented and use private data networks also tend to be extremely heavy telephone users as well, thus incurring substantial telephone charges on a regular continuing basis. These organizations include relatively large corporations, as well as government, academic and military organizations. Moreover, with increasing global computerization caused by explosive proliferation of personal computer usage over the past decade, even mid-sized and relatively small organizations with multiple offices are increasingly experiencing a need for access to an IP-based data network to facilitate inter-office data sharing and data communication. Though these organizations rarely, if ever, have sufficient usage to justify implementing their own networks, they are increasingly turning, for reasons of security and economy, to various network providers who offer secure access to a shared private IP network.
Recognizing the substantial telephone charges which these organizations regularly incur, particularly when viewed in the context of excess bandwidth available on their private data networks (whether dedicated or shared) and a near zero marginal cost of utilizing that bandwidth, these organizations would likely stand to economically benefit if this bandwidth could be used in some fashion to carry telephone calls that would otherwise be routed, at much higher cost particularly for international traffic, through the PSTN.
Currently, an effort, commonly referred to as “Voice over IP” (or more simply just “VoIP”), is underway in the art to develop technology and ultimately commercial products that can be utilized to transport, as an alternative to use of the PSTN, voice, data and facsimile communication, which would heretofore be carried over the PSTN, in packetized fashion over an IP data network, such as the Internet or a private data network. As currently envisioned in the art and described in A. Cary, “IP PBXs: Open Questions”,
Data Communications
, March 1999, pages 69-83 and particularly page 72, products embodying this technology will probably utilize one of two basic approaches: (a) an “adjunct” approach, and (b) a LAN-based approach. The adjunct approach would use existing subscriber PBXs, subscriber line wiring and telephone sets but incorporate a VoIP telephony gateway, as an “adjunct”, at each of a number different sites. At each site, a corresponding gateway would be situated between PSTN trunk connections to a PBX at that site and connections to an IP network, so as to route incoming and outgoing telephone calls between PBX peers at these sites through the IP network. In contrast, the LAN-based approach would replace conventional telephone subscriber equipment and telephone PBXs with IP-compatible telephones to packetize voice calls, and carry these calls over local area networks (LANs).
The LAN based approach is likely to meet with significant disfavor and commercial skepticism owing to a substantial expense, particularly with large organizations that have extensive telephone systems, associated with removing and replacing existing telephone equipment, including PBXs and tel
Bhatia Rajiv
Suh Ki Choon
Thornton Timothy R.
Ho Duc
Michaelson Peter L.
Michaelson & Wallace
Quintum Technologies, Inc.
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