Pulse or digital communications – Transceivers – Modems
Reexamination Certificate
1998-10-23
2002-11-12
Pham, Chi (Department: 2631)
Pulse or digital communications
Transceivers
Modems
C375S224000, C375S228000
Reexamination Certificate
active
06480531
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of networking systems and particularly networking systems employing a large number of modem devices.
2. Description of the Prior Art
As is commonly known, modem devices are often employed for transferring data, such as in the form of email messages, files, video and the like between various computer systems over telephone lines.
In this respect, modems are quite prevalent in networking applications for transmission and reception of data over many telephone lines or T
1
communications links. In networking systems employing a large number of modems, it is crucial to ensure that when data is transferred through modems, the integrity of the data that is being transferred remains intact. Ideally, this requires detection of malfunctioning or defective modem devices prior to their usage in order to avoid inaccurate data transfers. Once defective modem devices have been identified, there needs to be a replacement of the same with modems that are operational.
One prior art method for testing that is currently in use includes back-to-back testing in which a pair of modems is selected and one of the selected pair modems is designated as the originator while the other modem is referred to as the receiver. Data is sent from the originator to the receiver in the form of twenty-six characters which are sent one at a time. Subsequently, the data that is received by the receiver is compared to the original sent data in order to determine the functionality of the modems. If the data transfer is satisfactory the pair of modems is labeled as ‘good’, otherwise the pair is declared defective or ‘bad’.
By testing all of the modems in the system, a list of ‘good’ modems and a list of ‘bad’ modems is created. When a pair of modems is labeled as ‘bad’, it is not clear whether it is both modems of the pair that are defective or whether only one modem in the pair has failed. It is therefore necessary to test the modems that are included in the list of ‘bad’ modems against those that modems that are in the list of ‘good’ modems in order to identify any ‘good’ modems that are included in the ‘bad’ list. This, however, is a lengthy and time consuming process particularly where there are a large number of modems being utilized in a given system, which is commonly the case in networking environments such as the Internet.
On the other hand, it is desirable to perform extensive testing because the modems which pass rather simple tests of, for example, transferring 26 characters, may nevertheless fail if they were to undergo more elaborate testing. In other words, verification of modems using simple pass/fail tests does not necessarily yield accurate results. A modem may therefore erroneously be included in the list of ‘good’ modems whereas it may in fact actually be a ‘bad’ or defective modem.
This is especially important in the environment of a packet-switching network, such as the Internet, where an Internet Service Provider (ISP) readily depends on the reliability of modem products included within access servers. Furthermore, in systems wherein large numbers of modem products are employed, it becomes vital to perform functionality tests on modems in an expedient fashion to maintain high system performance.
Thus, in network environments employing communications products, such as modem devices, a method and apparatus is needed for reliably and expediently verifying the functionality of such communications products so as to maintain the integrity of data being transferred by the communications products thereby increasing system performance.
SUMMARY OF THE INVENTION
Briefly, a preferred embodiment of the present invention includes a method and apparatus for use in a digital system having a plurality of modem devices from receiving de-multiplexed digital channels of information through a transmission link and providing data for use by computer equipment for detecting the presence of defective modem devices, the plurality of modem devices being organized into groups having a predetermined number of modem devices, testing each of the modems in each group against the remainder of the modems in that group, determining the number of tests that each of the modems within the group have passed successfully, selecting among the modems within each group, a ‘leader’ modem having the highest pass rate and thereafter testing the remainder of the modems in that group against the chosen ‘leader’ modem thereby reliably isolating defective modems from use during normal operation of the digital system.
These and other objects and advantages of the present invention will no doubt become apparent to those skilled in the art after having read the following detailed description of the preferred embodiment illustrated in the several figures of the drawings.
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Cisco Technology Inc.
Law Offices of Imam
Pham Chi
Tran Khanh Cong
LandOfFree
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