Network access server testing system and methodology

Details Network access server testing system and methodology Network access server testing system and methodology

1998-08-12

2001-06-05

Trammell, James P. (Department: 2161)

Error detection/correction and fault detection/recovery

Data processing system error or fault handling

Reliability and availability

C714S046000

Reexamination Certificate

active

06243832

ABSTRACT:

TECHNICAL FIELD
The present invention relates to computer networking and, more particularly, to a system and methodology for testing network access servers.
BACKGROUND ART
The Internet is a rapidly growing, world-wide network of computer systems. One reason for the current popularity of the Internet is electronic mail (email). Users can send and receive email messages to friends, family members, and business contacts around the nation and indeed the world within minutes. Furthermore, the World-Wide Web is another popular aspect of the Internet. The World-Wide Web features information stored in “home pages” or “web pages” in the form of text, graphics, audio, and even video files at various sites in the Internet. Web pages include links to other web pages, so that a user “surfing” the World-Wide Web with a “browser” application can easily visit related sites with a click of a button. Consequently, Internet service providers (ISPs) are deploying host computer systems sited on the Internet. These host computer systems coordinate the flow of email, provide storage for web pages, and enable users at a personal computer to connect with the Internet.
A lot has to happen, however, before a user can connect to the Internet.
FIG. 4
depicts a typical Internet access network used by an Internet service provider to enable one of its customers to use the Internet. A user at a personal computer (PC), for example user PC
410
a
, executes locally resident network software to initiate a connection with an Internet service provider. When executed, the network software causes modem
412
a
to dial a predefined telephone number for the Internet service provider over a telephone line. The telephone call is routed by a central office telephone switch
420
to a network access server
430
belonging to the Internet service provider. The link between the central office telephone switch
420
can be a multiplexed line, such as a T1 line or a Primary Rate Interface (PRI) type ISDN link.
The network access server
430
, also known as a “remote access server” (RAS), is a combination of a modem bank and a high-end router. The incoming telephone call is automatically directed to one of the modems (not separately shown) belonging to the network access server
430
, typically assigned in a round-robin fashion. For example, the dial up number can be a lead number in a multi-line hunt group, so that a second, concurrent incoming telephone would be automatically “rolled over” to the next modem. In this manner the network access server
430
allows a plurality of users, for example at user PCs
410
a
,
410
b
, and
410
c
to access the Internet via modems
412
a
,
412
b
, and
412
c
, respectively.
Accordingly, one of the modems on the network access server
430
answers the telephone call and undergoes a modem handshaking procedure with the source modem
412
a
. When the modem handshaking is complete, the network access server
430
provides access to a host computer system
450
of the Internet service provider via a local area network
440
such as an Ethernet network. The host computer system
450
, also referred to as “ISP host
450
,” is typically a mini-computer or high end PC running a multi-process operating system, such as the Unix™ operating system or the Windows NT™ operating system.
Many ISP hosts
450
are configured to use the “point-to-point protocol” (PPP) for communication with one of the user PCs
410
. For PPP, each user PC is assigned an IP (Internet protocol) address for Internet communications. An IP address has four octets, each octet specifying a number from 0-255. When written in a human-readable format, the octets of an IP address are often separated by periods, for example, “10.1.1.1”. As well known in the art, ISP hosts
450
can be configured to use other communications protocols such as SLIP (single-line Internet protocol).
Since the ISP host computer system
450
also has an IP address, the user PC
410
a
and the ISP host
450
can communicate with each other using standard Internet protocols specifying their IP addresses. For example, a user can download files from ISP host
450
, e.g. text and graphics, or upload files to ISP host
450
. These files can include computer programs, graphics, and documents. ISP host
450
has access to an Internet connection
460
.
Some common Internet activities for users involve downloading a large number of files. For example, a user may wish to read news articles from news groups or bulletin board postings on Usenet. In this case, a user executes a “news reader” application, which coordinates the transfer of unread or otherwise desired articles from ISP host
450
or from a news server on Internet
460
.
As another example, the user may wish to access home pages on the World Wide Web. In this case, the user executes a “browser,” e.g. Navigator™ available from Netscape Communications Corp. or the Internet Explorer™ available from Microsoft Corp. The browser application coordinates the downloading of related files from ISP host
450
or other sites on the Internet
460
. These files comprise text files, i.e. home pages coded in the HyperText Markup Language HTML, graphics files, commonly encoded in such formats as GIF or JPEG, audio files, and other kinds of files.
As the user base for the Internet increases, Internet service providers have to support a growing number of customers. Consequently, the performance and reliability of their network access servers
430
under peak demand times become crucial.
For example, some unreliable network access servers undergo a loss of throughput for a high number of calls. Other network access servers may lose throughput if one of the connected users is downloading a very large binary file (e.g. a 2 megabyte graphics file). Some can only support a limited number of concurrent dial ups, even though the total number of modems is greater. Other network access servers run fine for a week, only to spontaneously reboot, disconnecting all the users.
To ensure reliability of network access servers before the Internet service providers go on-line with real customers, the vendors of network access servers need some system and methodology to effectively test the access network components. Systems already exist for some low level aspects of the network, for example, electrical functions. Some manufacturers have load tested their own network elements by manually initiating calls and data communications from a plurality of PCs.
Such testing, however, is not scalable nor standardized, and it is difficult to test high stress conditions. For example, a vendor of a network access server capable of supporting twenty-four concurrent connections may only use twelve PCs with modems for testing, due to the limited number of testers and financial resources in the quality assurance department. Thus, the network access server can be tested for up to half the total theoretical number of concurrent dial ups, twenty-four. However, during actual operation, it is not uncommon for twenty-four customers to dial in at the same time.
For example, if the network access server reboots and disconnects connected users, those users typically attempt to reestablish their connections all at the same time. Therefore, conventional methods are unable to test likely usage patterns of network access servers.
DISCLOSURE OF THE INVENTION
There is a need for a system and methodology to test network access servers under high stress conditions and with likely usage patterns. A need also exists for an automatic network access server testing method and system.
These and other needs are met by the present invention, in which a test computer system with a bank of communications interfaces is coupled to a network access server via a telephone switch and is configured to simulate multiple, concurrent users using the network access server.
Accordingly, one aspect of the invention is a network for testing a network access server. The network includes a test computer system. The test computer system has more than one communications interfaces, such as modem or IS

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