Secure LAN/internet telephony

Details Secure LAN/internet telephony Secure LAN/internet telephony

1997-06-03

2001-05-15

Pham, Chi H. (Department: 2731)

Multiplex communications

Pathfinding or routing

Combined circuit switching and packet switching

C370S401000

Reexamination Certificate

active

06233234

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to telephony over a public packet switched data network such as the Internet to and from a multi-site industrial/business establishment having a local area network linking the sites and serving as a link to the public packet switched data network through a localized gateway system.
Acronyms
The written description uses a large number of acronyms to refer to various services and system components. Although generally known, use of several of these acronyms is not strictly standardized in the art. For purposes of this discussion, acronyms therefore will be defined as follows:
ADPCM
Adaptive Differential Pulse Code Modulation
ARPA
Advanced Research Projects Agency
ARPANET
Advanced Research Projects Agency NETwork
AS
Autonomous Systems
ATM
Asynchronous Transfer Mode
CDMA
Code Division Multiple Access
CO
Central Office
CODEC
digital CODer and DECoder
CPU
Central Processing Unit
CREN
Corporation for Research and Educational
Networking
DHCP
Dynamic Host Configuration Protocol
DID
Direct Inward Dialing
DNS
Domain Name Server
DTMF
Dual Tone Multi-Frequency
FDDI
Fiber Distributed Data Interface
GAO
Government Accounting Office
IP
Internet Protocol
ISDN
Integrated Services Digital Network
ISP
Internet Service Provider
LAN
Local Area Network
MAC
Media Access Control
MILNET
MILitary NETwork
NSFNET
National Science Foundation NETwork
PC
Personal Computer
PABX
Private Automatic Branch Exchange
PBX
Private Branch Exchange
POTS
Plain Old Telephone Service
PPP
Point to Point Protocol
PRI
Primary Rate Interface (for ISDN)
PSTN
Public Switched Telephone Network
RAM
Random Access Memory
ROM
Read Only Memory
TCP
Transmission Control Protocol
SONET
Synchronous Optical NETwork
SMDS
Switched Megabit Data Service
SMDI
Simplified Message Desk Interface
T1
Digital Transmission Link with 1.544 Mbps
Capacity (24 voice channels)
T3
Digital Transmission Link with 44.73 Mbps
Capacity (672 voice channels)
TDMA
Time Division Multiple Access
X.25
Protocol Providing Direct Connection to a
Packet Switched Network
BACKGROUND ART
Attention recently has been directed to implementing a variety of communication services, including voice telephone service, over the worldwide packet switched data network now commonly known as the Internet. The Internet had its genesis in U.S. Government programs funded by the Advanced Research Projects Agency (ARPA). That research made possible national internetworked data communication systems. This work resulted in the development of network standards as well as a set of conventions, known as protocols, for interconnecting data networks and routing information across the networks. These protocols are commonly referred to as TCP/IP (transmission control protocol/internet protocol). The TCP/IP protocols were originally developed for use only through ARPANET but have subsequently become widely used in the industry. TCP/IP is flexible and robust. TCP takes care of the integrity, and IP moves the data.
The Internet provides two broad types of services: connectionless packet delivery service and reliable stream transport service. The Internet basically comprises several large computer networks joined together over high-speed data links ranging from ISDN to T1, T3, FDDI, SONET, SMDS, ATM, OT
1
, etc. The most prominent of these national nets are MILNET (Military Network), NSFNET (National Science Foundation NETwork), and CREN (Corporation for Research and Educational Networking). In 1995, the Government Accounting Office (GAO) reported that the Internet linked 59,000 networks, 2.2 million computers and 15 million users in 92 countries. However, since then it is estimated that the number of Internet users continues to double approximately annually.
In simplified fashion the Internet may be viewed as a series of packet data switches or ‘routers’ connected together with computers connected to the routers. The information providers constitute the end systems which collect and market the information through their own servers. Access providers are companies such as UUNET, PSI, MCI and SPRINT which transport the information. Such companies market the usage of their networks to the actual end users.
FIG. 9
shows a simplified diagram of the Internet
349
and various types of systems typically connected thereto. Generally speaking the Internet consists of Autonomous Systems (AS) type packet data networks which may be owned and operated by Internet Service Providers (ISPs) such as PSI, UUNET, MCI, SPRINT, etc. Three such AS/ISP networks appear in
FIG. 9
at
310
,
312
and
314
. The Autonomous Systems (ASs) are linked by high bandwidth Inter-AS Connections
311
,
313
and
315
. Information providers
316
and
318
, such as America Online (AOL) and Compuserve, connect to the Internet via high speed lines
320
and
322
, such as T1/T3 and the like. Information providers generally do not have their own Internet based Autonomous Systems but have or use Dial-Up Networks such as SprintNet (X.25), DATAPAC and TYMNET.
In some cases, the information provider
316
or
318
operates a host server or network of servers that their customers access by dial-up connection. If a customer wants information over and above that offered by the provider, the host server provides a tunnel connection through to the high speed link and the Internet
349
. Other parties may connect into the network
349
at some other point and access information offered by provider
316
or
318
through the network
349
.
By way of current illustration, MCI is both an ISP and an information provider, SPRINT is an ISP, and the MicroSoft Network is an information provider using UUNET as its ISP. Other information providers, such as universities, are indicated in exemplary fashion at
324
and are connected to the AS/ISPs via the same type connections here illustrated as T1 lines
326
. Parties access information on servers of providers
324
via the Internet
349
. Corporate Local Area Networks (LANs), such as those illustrated in
328
and
330
, are connected through routers
332
and
334
and high speed data links such as T1 lines
336
and
338
. Laptop computers
340
and
342
are representative of various personal computers and the like connected to the Internet via the public switched telephone network (PSTN) and are shown connected to the AS/ISPs via dial up links
344
and
346
.
Recently, several companies have developed software for use on personal computers to permit two-way transfer of real-time voice information via an Internet data link between two personal computers, for example between PCs
340
and
342
. In one of the directions, the sending computer converts voice signals from analog to digital format. The software facilitates data compression down to a rate compatible with modem communication via a POTS telephone line, in some cases as low as 2.4 kbits/s. The software also facilitates encapsulation of the digitized and compressed voice data into the TCP/IP protocol, with appropriate addressing to permit communication via the Internet
349
. At the receiving end, the computer and software reverse the process to recover the analog voice information for presentation to the other party. These programs permit telephone-like communication between Internet users.
PCs having voice communication capabilities can conduct two-way, real-time audio communications with each other, in a manner directly analogous to a two-way telephone conversation. However, the actual signals exchanged between two such terminal devices go through the public packet data network. Typically, such communications at least bypass long distance interexchange carriers.
Internet based telephone programs have relied on servers (not separately shown) coupled to the Internet to establish voice communication links through the networks. Each person active on the network, who is willing to accept a voice call, must register with a server. A calling party can call only those persons registered on the voice communication server.
Subsequent new developments have provided systems which are capable of avoiding s

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