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Description  |
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BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
The invention relates to apparatus, and accompanying methods for use therein, for an ISDN LAN modem (or an aspect thereof) that is particularly, though not exclusively, suited for small user environments and which contains an internal ISDN router
having a self-contained network hub for inter-connecting multiple network devices, such as workstations, to each other through a local area network (LAN) and for permitting each of those devices to gain access through the router to any one of a number of
different remote networks.
2. Description of the Prior Art
Over the past decade, personal computer (PC) usage has increased substantially to the point where currently PCs have diffused into many aspects of a business organization. Coincident with this phenomena, a desire has increasingly arisen,
certainly in a workplace environment, among computer users in a common organization, such as a business establishment, to readily share computer files. This desire, particularly when fueled by historically decreasing costs of network equipment, has led
to an expanding number of network installations throughout the business community to facilitate file sharing and electronic communication among not only users in a common organization, but also with users at other organizations and locations. Moreover,
as these costs of increasingly sophisticated PCs and network equipment continue to fall, networked computer usage is penetrating increasingly smaller organizations as the expected benefits to those organizations, such as expanded productivity, outweigh
the costs associated therewith.
Moreover, the trend of increasing PC usage is not confined to business. Home usage of PCs is also rising though currently penetration of PCs into homes is still considerably less than that in the business community. Nevertheless, PC
applications exist that address various needs of a family, from, e.g., traditional productivity tools, such as work processing for, e.g., home office use, to education, entertainment and to Internet access. Given this, today, it is increasingly common
for a family to possess several PCs. For example, for a typical family of two spouses and two children of school age, each spouse may require his(her) own PC for business use, such as for job-related endeavors, while each child may have one PC or share
a common PC, purchased for all children in the family, for, e.g., educational use, such as running teaching programs of one sort or another, Internet access, or entertainment.
If current cost and technology trends continue, PC usage should increasingly proliferate throughout businesses and families to a point of becoming rather ubiquitous and inter-connected, i.e., at least ideally and at some time in the future where
most people will possess their own PC and where such PCs will become increasingly inter-networked with each other.
However, a significant obstacle to increasing PC usage and inter-networking has been the continued difficulty many individuals face when installing and configuring a PC, let alone connecting the PC to a wide area network (WAN), such as the
Internet, or even implementing a simple local area network (LAN).
For many individuals, specifically those inexperienced with PCs, the task of just installing and configuring a PC itself is so daunting, particularly for so-called IBM compatible PCs, that the task often negates their desire to purchase a PC. To
counter this, PC manufacturers have made and continue to make significant strides over the past few years, such as through incorporating so-called "Plug and Play" hardware and using compatible pre-loaded operating systems, such as the "WINDOWS 95"
operating system (WINDOWS 95 is a trademark of the Microsoft Corporation of Redmond, Wash.), to automatically detect system hardware and self-configure the PC, as well as to simplify subsequent PC use and maintenance. Unfortunately, the same can not be
said for computer networks.
Installing hardware for a very simple computer network for a small number of users (henceforth referred to as a "workgroup") is relatively straightforward--typically encompassing installing a multi-port network hub and a network interface card,
the latter into each PC to be networked in the workgroup, and running interconnecting cables therebetween. However properly configuring conventional network hardware and associated software in each of the PCs is a rather tedious task--one that often
frustrates even an experienced user. Consequently, many users desiring to network their computers, even for a simple network, have relegated the task of installing and properly configuring their networks, including both hardware and software components,
to properly trained service organizations or consultants but at a considerable expense relative to the cost of the equipment. While a relatively large organization can afford to incur such expenses, small organizations and families can not.
Accordingly, while many small business users and even home users could significantly benefit from networking their computers together as workgroups--such as through file sharing and electronic communication, the difficulty and expense associated
therewith has effectively limited the penetration of computer networks into these environments.
Therefore, a need exists in the art for a computer networking device that not only implements a LAN, which permits computers to be networked together in, e.g., a workgroup, but also significantly simplifies and expedites network configuration.
Such a device should ease the burden placed on the user as much as possible, preferably to a point of automatically adapting itself, without user intervention, to its current network environment. As yet, no such device exists in the art.
Furthermore and quite apart from increasing proliferation of PCs, in recent years, a number of domestic and foreign telephone companies have begun offering Integrated Service Digital Network (ISDN) services to their customers. ISDN provides an
integrated voice and data network that offers both increased bandwidth and significant flexibility over traditional analog telephone services. Inasmuch as subscriber charges for ISDN access are decreasing--with the decrease being rather noticeable for
some telephone companies, demand for ISDN service and equipment is rising appreciably. Demand is particularly strong and growing for those subscribers who seek cost-effective high speed access to a WAN such as, e.g., the Internet, and/or other computer
networks.
In particular, a basic rate (so-called "2B+D" service) ISDN interface
provides higher speed bandwidth than both traditional analog, modem-based dial-up access modalities and comparably priced switched digital services. Each so-called B ("bearer") channel, which carries subscriber voice and/or data, provides 64
Kbits/second of bandwidth; while a D ("data") channel, which carries signaling and control information, provides 16 Kbits/second of bandwidth. For the bandwidth delivered, an ISDN line is significantly less expensive than a private leased line that
supplies the same bandwidth across the three channels. Furthermore, ISDN, being a digital end-to-end service, provides digital transmission channels that tend to be more accurate and reliable, from a standpoint of error rates and dropped connections,
than are conventional analog telephone connections. In addition, ISDN service provides rapid connect times which, in turn, provide faster support for those LAN protocols that require relatively short latency across WAN connections.
Starting a few years ago, various networking and communications equipment manufacturers have been offering relatively inexpensive ISDN terminal adapters, more commonly and rather loosely referred to as "ISDN modems" (though these adapters do not
contain a traditional analog modulator-demodulator as occurs in a conventional analog modem), and other ISDN-based network devices, such as routers, for subscriber end-use. Such a modem, also generically referred to as "data circuit terminating
equipment" (DCE), once connected to an ISDN connection and a serial port on a subscriber's PC, permits that subscriber to connect his(her) computer to, e.g., an Internet service provider and communicate at speeds approximately two to four times greater
than through a conventional analog modem. The computer so connected becomes so-called "data terminal equipment" (DTE). While the availability of ISDN modems is clearly not the sole cause underlying the growth in ISDN usage, it, when combined with
decreasing rates for ISDN service, is certainly a large and growing factor.
Unfortunately, currently available ISDN devices, such as routers, which connect a network, e.g., an Ethernet network, to a single ISDN connection are rather cumbersome and tedious to configure. In that regard, such a router typically contains an
RS-232 serial port to which a PC is connected in order to initially configure the router. During configuration, a user at the PC, typically executing a proprietary application provided by the manufacturer of the router, assigns suitable network
parameters, including in IP address and a subnet mask, to the router. Until these parameters are loaded into the router, the router is simply unable to communicate over the network to any PC connected thereto. Determining the correct value of these
parameters and then completing the configuration, with all the other salient information, proved to be a rather tedious process. Furthermore, not only did the user incur a burden of installing software on the PC used to configure the router, but also
the price of the router needed to reflect an added cost of the serial port, which during the life of the router is usually used just once for initial configuration.
In addition, in the event of a network fault or other condition that affects a connection to a remote LAN or WAN and/or server thereon, conventional routers do not indicate the specific nature of that fault to any local client connected to the
router. This, in turn, relegates the user at that client to rely on an error message, in those instances when it is provided by a network, that is often rather cryptic at best and more often simply not provided at all. In the latter situation, the user
simply waits in basically total ignorance of the fault, i.e., the fault occurs but the user receives no indication of it on, e.g., his(her) browser. Not only is the user annoyed by this type of fault handling, but also the user if forced to wait, owing
to a lack of information which leads to an expectation (which later proves to be unwarranted) that the fault will resolve itself, which can be rather time-consuming and frustrating.
Moreover, it is increasingly common to find multiple users on the same network who simultaneously desire to connect to the Internet through different network service providers, e.g., one user may desire to connect to one Internet service provider
(ISP) at the same time another user wants to connect to a different ISP. Unfortunately, currently available ISDN routers can not accommodate simultaneous ISDN connections by multiple PCs to different ISPs; such routers are limited to accommodating only
one connection to one ISP at a time. Moreover, these routers are unable to control access, on a per PC basis, to any one of a number of multiple accounts across different network service providers.
Hence, given the increasing availability of economical ISDN connections and advantages associated with the use thereof, the computer networking device needed in the art should not only implement a LAN that serves a workgroup but also should
implement an ISDN router to provide simultaneous high-speed access for the LAN through a single ISDN connection to multiple service providers, such as, e.g., different ISPs. Moreover, such a device should be easy to configure, without a need for any
external software, and to reduce its price, dispense with a need for any serial or other port used solely for initial configuration.
Advantageously, such a device, which as yet does not exist in the art, should not only substantially eliminate user frustration and significantly reduce time and costs associated with establishing, configuring and using a LAN for a workgroup as
well as with connecting each PC therein to a remote network service provider, but also increase the use of such LANs in small businesses and among home users to the eventual benefit of each.
SUMMARY OF THE INVENTION
The present invention overcomes the deficiencies in the art and satisfies these needs by providing an ISDN LAN modem that contains an ISDN router, with an internal multi-port hub to implement a LAN (local are network), that automatically adapts
itself to a current network environment of a workstation connected thereto and then permits browser-based configuration, and accommodates several modalities of network communication not heretofore possible in a conventional router.
With respect to configuration, the LAN modem can receive configuration information directly from a workstation connected to the LAN, and specifically through, illustratively, a web browser (or other appropriate TCP/IP application, such as Telnet)
executing on that workstation, advantageously without any need for any additional serial (or other) port on either the LAN modem or the workstation.
Specifically, in accordance with specific teachings of the present invention, once the workstation is connected to the hub and the browser begins executing on the workstation, the LAN modem automatically adapts itself to the current network
environment of the workstation. To do so, the LAN modem will detect the Ethernet address of that workstation through packets transmitted by the workstation, determine the IP address of that workstation (either through dynamic assignment or by static
address of the workstation from an ARP (address resolution protocol packet)), and then, if the workstation is using static addressing, set its own IP address and subnet mask such that the LAN modem and the workstation are on the same subnet. Once this
occurs, the LAN modem and the workstation are then able to communicate over the network through the web browser. The LAN modem will then intercept any request issued by the workstation to fetch a web page and, through its own internal web server, will
generate and download to the workstation, a default home page through which the user can commence configuring the LAN modem. Once configuration commences, the web server will then step the user through a succession of displayed web pages through which
the user will be queried to enter salient configuration data. The web server will then extract this data from responses received from the user and then store this data, for subsequent use, in a shared database within the LAN modem.
Furthermore, the LAN modem provides additional modalities of network communication through use of an inventive multi-tiered routing hierarchy, which permits bi-directional translation between many individual private IP addresses and one shared
public IP address.
Specifically, the LAN modem assigns a private IP address to each workstation that connects to the LAN. The LAN modem translates the individual private IP address of each of the workstations to a single public address assigned, e.g., either
statically or dynamically, to the LAN modem by a network service provider, e.g., and Internet service provider (ISP), by accessing a source-based routing table and a host list which collectively associate the private source IP address of a particular
workstation on the LAN and a network ID for the service provider to which that workstation is ultimately connected through the LAN modem. The LAN modem also translates source and destination port number fields, as needed. This IP address and port
number translation assures uniqueness of a set of source/destination IP addresses, protocol ID and source/destination port numbers in packets that flow between unique client/server applications and which pass through the LAN modem so as to provide
unambiguous routing in the LAN modem between all the workstations connected to the LAN modem and associated remote servers.
Consequently, through such translation, then as far as the ISP is concerned, all packet traffic involving the workstations, by virtue of their common, though shared, public IP address, appears to emanate from or be directed to a single user.
Appropriate account information, such as user identification and password data, for the shared account is stored within the shared database in the LAN modem. Through this information, the LAN modem transparently established the connection between the
workstations and the ISP without prompting any of the actual users therefor for appropriate account information. As a result of employing this inventive translated addressing technique, the LAN modem distributes (effectively de-multiplexing) individual
packets emanating over a single ISDN connection from the ISP to the proper workstations on the LAN, and routes (i.e., effectively multiplexes) outgoing packets, from all such workstations having differing private IP addresses, into a common packet stream
over a single shared packet connection to that ISP for subsequent transport over the remote network. Advantageously, by permitting multiple users to share a single ISP account, use of our inventive technique is likely to significantly reduce collective
network access charges over what these users would otherwise incur if, as conventionally occurs, they were to gain network access through separate user accounts.
Furthermore, through use of the inventive hierarchical routing scheme, the LAN modem can simultaneously route packet traffic between multiple workstations on the LAN and different corresponding ISPs through different ISDN connections
simultaneously existing between the LAN modem and those providers. In this regard, the LAN modem accommodates connections to several different user-definable network service providers, e.g., ISPs, by storing appropriate information for each such
provider in a shared database, such as user account and password information, as well as network identification including network IP address, domain names and remote DNS server addresses, and employing this information to define the appropriate
connections and properly route packets accordingly over these connections.
As a feature of the present invention, the LAN modem advantageously contains internal co-operating DHCP (dynamic host control protocol) and DNS (domain name system) servers that are integrated with routing and call management processes, all
utilizing data stored within the shared database.
Use of the internal DNS server provides local name-to-address resolution such that, for user convenience and simplicity, each workstation on the LAN can be addressed in terms of its machine name rather than its IP address. Furthermore, the DNS
server, by using the same shared database as does the DHCP server, operates transparently of any user to acquire machine names of all the workstations connected to the LAN and then provide suitable machine name to IP address resolution, as needed, for
all communication between the LAN modem and these workstations as well as between any pair of workstations themselves. In addition, the DNS server given a DNS query, will determine, based on the source of the query, i.e., which specific workstation
generated it, and the destination to which the query is directed (e.g., another host on the LAN as identified by the machine name of the host, the LAN modem itself or a remote network), the DNS server to which the query is to be routed and will then
route the query accordingly to that server. As such, the LAN modem hides from a host the selection of the DNS server that will be used in a given instance and hence significantly simplifies the use of the DNS in each workstation connected to the LAN
modem. In addition, the DHCP server provides the IP address, subnet mask and gateway and DNS server addresses to the local workstations, thereby eliminating any need for a user to manually configure and administer these items. Furthermore, any
workstation is always assigned the same IP address from the DHCP server, rather than having its IP address change from session to session, as would normally occur with dynamic IP addressing. Consequently, a user profile associated with each workstation
can be easily maintained and identified using its host IP address, and the number of workstations that are simultaneously allowed to use the LAN modem can be very easily controlled.
As another feature of the present invention, the LAN modem assures the integrity, to a substantial degree, of executing program code stored within volatile memory, e.g., DRAM (dynamic random access memory), within the LAN modem, thereby
advantageously preventing to a significant extent code corruption and improper operation of the LAN modem. Flash memory, by virtue of its non-volatility, stores executable program code for the LAN modem. Upon a system reset, the executable code is
written into DRAM, which provides markedly faster access time over the flash memory, from which the code is then executed.
Specifically, while the LAN modem is idling, a preemptable background process executes with, e.g., a low execution priority, to continually compare the entire executable program code stored in the DRAM, on a location-by-location basis, with that
stored in the flash memory. In the event a discrepancy is detected, the contents of a location in flash memory are copied to a corresponding location in the DRAM to eliminate the discrepancy, thereby maintaining the integrity of the executable code
stored in the DRAM. Integrity of the code stored in the flash memory is assured by restricting any change in the mode of the flash memory from read-only to read/write through use of a key-based software lock.
As an additional feature of the present invention, the LAN modem contains an internal web server that, in addition to storing full web pages, constructs web pages in real-time from a predefined stored web page template by selectively inserting,
e.g., event-specific, code segments therein. Illustratively, this insertion occurs by substituting such a segments(s) for a corresponding so-called "placeholder(s)" that appears in the template. These segments can represent dialog boxes, graphics,
predefined textual messages or, generically speaking, any object, whether implemented through HTML or otherwise, that is to be, e.g., selectively presented to a user either for display and/or to solicit a response, such as an item of data or a selection
among a list of predefined data values, from the user. Since relatively few full web pages are stored, memory requirements to store the underlying data to support the web server advantageously become rather modest. Illustratively, and in the context of
the LAN modem, these web pages are used to query a user situated at any workstation on the LAN to enter information needed to configure the LAN modem, as well as to display a specific nature and cause, if known, of a detected fault condition so that an
affected user situated at any such workstation can take appropriate action.
BRIEF DESCRIPTION OF THE DRAWINGS
The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
FIG. 1 depicts an overall high-level block diagram of inventive LAN modem 300 in it typical environment of use;
FIGS. 2A-2C each depicts a different illustrative mode of operation which inventive LAN modem 300, shown in FIG. 1, can provide;
FIG. 3 depicts a hardware block diagram of inventive LAN modem 300 shown in
FIG. 1;
FIG. 4A depicts an overall block diagram of software that is executed by central processing unit (CPU) 330, shown in FIG. 3, situated within the inventive LAN modem;
FIG. 4B depicts an architectural block diagram of software 400 contained within application software 4020 shown in FIG. 4A that, among other aspects, implements the various modes of operation of the LAN modem shown in FIGS. 2A-2C;
FIG. 5 depicts interaction, in terms of predominant inter-process communications, that occurs within software 400 shown in FIG. 4B for setting up an ISDN call based on traffic on the local area network (LAN);
FIG. 6 depicts interaction, in terms of predominant inter-process communications, that occurs within software 400 shown in FIG. 4B for setting up an ISDN call based on a DNS (domain name system) request from a workstation (host) on the LAN;
FIG. 7 depicts interaction, in terms of predominant inter-process communications, that occurs within software 400 shown in FIG. 4B for processing an incoming ISDN call to the LAN modem;
FIG. 8 depicts interaction, in terms of predominant inter-process communications, that occurs within software 400 shown in FIG. 4B for disconnecting an ISDN call as a result of an idle timeout condition;
FIG. 9 depicts the correct alignment of the drawing sheets for FIGS. 9A-9C;
FIGS. 9A-9C collectively depict a flowchart of Initial Configuration procedure 900 performed by CPU 330;
FIG. 10 depicts the inventive source-based routing architecture used in the LAN modem;
FIG. 11 depicts a flowchart of Primary Router procedure 1100 shown in FIG. 10 and performed by CPU 330;
FIG. 12 depicts the correct alignment of the drawing sheets for FIGS. 12A-12D;
FIGS. 12A-12D collectively depict a flowchart of Secondary Router procedure 1200 also shown in FIG. 10 and performed by CPU 330;
FIG. 13A depicts the structure of host list 1300 including its constituent data fields and their initial entries, contained within database 416 stored within flash memory 376 shown in FIG. 3;
FIG. 13B depicts the structure of network service provider list 1350 including its constituent data fields also contained within database 416 stored in flash memory 376 shown in FIG. 3;
FIG. 13C depicts the structure of Destination-Based Routing Table 432, including its initial values, stored within DRAM 372 shown in FIG. 3;
FIG. 13D depicts the structure of Source-Based Routing Table 446 which is also stored within DRAM 372 shown in FIG. 3;
FIG. 14 depicts a flowchart of DHCP Induced IP Address Request procedure 1400 performed by CPU 330;
FIG. 15 depicts the correct alignment of the drawing sheets for FIGS. 15A-15D;
FIGS. 15A-15D collectively depict a flowchart of DNS Induced IP address Request procedure 1500 that is also performed by CPU 330;
FIG. 16 depicts a flowchart of Firmware Upgrade (FU) process 402 shown in FIG. 4B that is also performed by CPU 330;
FIG. 17 depicts a flowchart of Firmware Assurance Manager process 1700 that is contained within application programs 4020 shown in FIG. 4A and is executed therein as background (lowest priority) application 4030;
FIG. 18 depicts a high-level block diagram of web server 412, shown in FIG. 4B, and certain of its associated processes;
FIG. 19 depicts a flowchart of Static Page Processing operation 1830 that is performed by web server 412 shown in FIG. 18;
FIG. 20 depicts a flowchart of Dynamic Page Formation operation 1840 that is also performed by web server 412 shown in FIG. 18;
FIG. 21 depicts a flowchart of Post Processing operation 1850 that is also performed by web server 412 shown in FIG. 18;
FIG. 22 depicts code 2200 for an illustrative inventive web page template, and specifically one employed in conjunction with an ISP Wizard used in the LAN modem;
FIG. 23 depicts a page, as would be rendered on a workstation display, in response to HTML code 2200 shown in FIG. 22;
FIG. 24 depicts, in block diagram form, inventive process 2400 for forming a web page from a web page template and page components, and illustratively for a web page used in conjunction with the ISP Wizard;
FIG. 25 depicts HTML code 2500 for a specific web page that results from use of process 2400 and template HTML code 2200 for a specific event, e.g. a failure to establish a connection to an Internet service provider (ISP);
FIG. 26 depicts a page, as would be rendered on a workstation display, in response to HTML code 2500 shown in FIG. 25;
FIG. 27 depicts a sequence of three pages 2710, as would be rendered on a workstation display, to portray a progress bar and which result from three corresponding HTML code segments 2720, all of which are dynamically constructed in accordance
with the present invention;
FIG. 28 depicts a flowchart of File Creation process 2800 that creates a common file of a web page template and associated web page components in accordance with the present invention;
FIG. 29 depicts data structure 3000, stored within repository 1860, containing templates and web page components as produced through execution of File Creation process 2800 shown in FIG. 28;
FIG. 30 depicts the correct alignment of the drawing sheets for FIGS. 30A-30B;
FIGS. 30A-30B collectively depict source code for data structure 3000 containing, in accordance with the present invention teachings, various entries each having, for either an illustrative web page template or an illustrative web page component,
a pointer and a corresponding name; and
FIG. 31 depicts actual object code for a document array, e.g., FRMAIN.sub.-- HTM[ ], containing a corresponding illustrative predefined web page component, as stored in structure 3000.
To facilitate understanding, identical reference
numerals have been used, where possible, to designate identical elements that are common to various figures.
DETAILED DESCRIPTION
After considering the following description, those skilled in the art will clearly realize that the teachings of the present invention can be readily utilized in substantially any ISDN data circuit terminating equipment (DCE) which interfaces an
ISDN line to nearly any form of computer network, regardless of the type of network. In that regard, the ISDN line can be, e.g., a basic rate (2B+D) interface (BRI) or a primary rate (23B+D or 30B+D) interface. Moreover, the network can be
illustratively Ethernet, Token Ring, asynchronous transfer mode (ATM), frame relay or other type of network--with the actual network modality being irrelevant to the present invention. In addition, these teachings are also applicable across a wide
variety of remote network connection modalities, not just ISDN. In that regard these modalities can illustratively range from, e.g., analog telephone connections using conventional modems, through high-speed digital connections such as ATM or frame
relay. Inasmuch as Ethernet networks are the predominant network architecture used in inter-connecting personal computers (PCs) in a local area network, and particularly those for implementing as workgroups, to simplify the discussion, the invention
will be discussed in that context. Moreover, since a basic rate type ISDN interface is often used to provide a remote network connection for individual subscribers and small businesses, we will also discuss our invention in the context of its use with
such an interface. Clearly, after considering this discussion, those skilled in the art will readily appreciate how to use our invention with any of a wide range of differing types of computer networks and to modify the inventive teachings, as
necessary, to conform to the requirements of the specific network being used, as well as to conform use of the present invention with another type of ISDN interface, or different connection modality, to a remote network.
A. Overall Network Environment
FIG. 1 depicts an overall high-level block diagram of the inventive local area network (LAN) modem 300 in its typical environment of use. Though LAN modem 300 does not contain a traditional analog modulator-demodulator as occurs in a
conventional analog modem, for ease of reference, this device will nevertheless be referred to as a "LAN modem" inasmuch as it provides the general functionality associated with a modem of connecting a workstation to an external computer network, though
here through an ISDN, rather than an analog POTS (plain old telephone service), connection.
As illustrated, LAN modem 300 inter-connects a group of workstations (also referred to herein as "hosts") 10, illustratively here four individual workstations (typically personal computers--PCs) 10.sub.a, 10.sub.b, 10.sub.c and 10.sub.d, in an
Ethernet local area network. To implement the LAN, LAN modem 300 contains ISDN router 305 which itself contains an internal, here illustratively 10 Mb/second 10 BaseT, Ethernet hub 340 which connects through ports 15, specifically 15.sub.a, 15.sub.b,
15.sub.c and 15.sub.d, to workstations 10.
The router establishes an ISDN connection through BRI ISDN connection 40 and public switched telephone network (PSTN) 50 to appropriate remote networks 60 and/or 70, such as the Internet or a private network, accessible through a corresponding
service provider, or a remote LAN, such as an office network. Inasmuch as router 305, as discussed in detail below, can accommodate, in one of its operational modalities (as discussed below in conjunction with FIG. 2B), two simultaneous connections,
over different B channels (here shown as B.sub.1 and B.sub.2) in a common BRI ISDN connection, to two different external networks, these connections are symbolized by leads 55 and 58 connecting remote networks 60 and 70 over channels B.sub.1 and B.sub.2,
respectively.
Apart from routing ISDN packet traffic, via PSTN 50, between any of workstations 10 and a remote network(s), LAN modem 300, specifically ISDN router 305 therein, can also accommodate two analog telephone devices 20 (here illustratively shown as
facsimile machine 20.sub.a and telephone 20.sub.b and also denoted as analog telephone devices 1 and 2, respectively) appropriately interfaced, via ports 25, to analog lines 25.sub.1 and 25.sub.2. In that reg | | |
