Multiplex communications – Diagnostic testing
Reexamination Certificate
1998-06-19
2001-09-18
Vincent, David R. (Department: 2732)
Multiplex communications
Diagnostic testing
C370S445000
Reexamination Certificate
active
06292467
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to network interfacing, and more particularly, to methods and systems for detecting a link status between network stations connected to a telephone line medium.
2. Description of the Related Art
Local area networks use a network, cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface cards at each station to share access to the media.
Conventional local area network architectures use media access controllers operating according to half-duplex or full-duplex Ethernet (ANSI/IEEE standard 802.3) protocol using a prescribed network medium, such as 10 BASE-T. Newer operating systems require that a network station be able to detect the presence of the network. In an Ethernet 10 BASE-T environment, the network is detected by the transmission of a link pulse by the physical layer (PHY) transceiver. The periodic link pulse on the 10 BASE-T media is detected by a PHY receiver, which determines the presence of another network station transmitting on the network medium based on detection of the periodic link pulses. Hence, a PHY transceiver at Station A is able to detect the presence of Station B, without the transmission or reception of data packets, by the reception of link pulses on the 10 BASE-T medium from the PHY transmitter at Station B.
Efforts are underway to develop an architecture that enables computers to be linked together using conventional twisted pair telephone lines instead of established local area network media such as 10 BASE-T. Such an arrangement, referred to herein as a home network environment, provides the advantage that existing telephone wiring in a home may be used to implement a home network environment. However, telephone lines are inherently noisy due to spurious noise caused by electrical devices in the home, for example dimmer switches, transformers of home appliances, etc. In addition, the twisted pair telephone lines suffer from turn-on transients due to on-hook and off-hook and noise pulses from the standard POTS telephones, and electrical systems such as heating and air conditioning systems, etc. Hence, the 10 BASE-T technique of sending link pulse cannot be used in a home networking environment, since the link pulses cannot be distinguished from noise signals inherently present in home networking environments.
SUMMARY OF THE INVENTION
There is a need for an arrangement for a network station to reliably detect the presence of other stations on the network, or the failure on the network, when the network includes a telephone line medium.
There is also a need for an arrangement for a network node to determine the presence of another network node on a medium susceptible to noise, without the necessity of transmitting a data packet that may otherwise reduce network throughput.
There is also a need for an arrangement in a network station to determine the presence of another network node on a medium susceptible to noise, while minimizing any reduction in system resources in a network station.
These and other needs are attained by the present invention, where a physical layer transceiver in a network having a telephone line medium determines the presence of another network station connected to a telephone line medium by determining the presence of a transmitted frame on the telephone line medium within a prescribed interval.
According to one aspect of the present invention, a method in a first network station enables detection of a link status with a second network station connected to a telephone line medium. The method includes determining a presence of a frame on the telephone line medium from the second network station within a prescribed interval. The method also includes setting the link status to an invalid state based on the determined absence of the frame within the prescribed interval. The detection of a transmitted frame on the telephone line medium enables the first network station to determine the link status based on the reception of the transmitted frame within a prescribed interval. If the frame is not detected within the prescribed interval, then the first network station sets the link status to an invalid state. In addition, the transmitted frame may be either a data frame, or a link frame having a length less than the minimum frame length. Use of a link frame having a length less than a minimum data frame length enables a physical layer transceiver to process the received link frame as if it was a data frame, by sending the link frame to the media access controller. Since the link frame is less than the minimum data frame length, the media access controller will discard the link frame as a runt frame, without wasting system resources in the receiving network station. Hence, a network station may reliably determine a link status with minimal disruption in network throughput, and while avoiding disruption of system resources in a network station.
Another aspect of the present invention provides a method in a network having a first network station, a second network station, and a telephone line medium for communication between the first and second network stations. The method includes transmitting by the first network station a link frame, having a length less than a minimum length of a data frame, onto the telephone line medium a first prescribed interval following transmission of the data frame by the first network station. The method also includes, in the second network station, determining a presence of the transmitted link frame on the telephone line medium within a second prescribed interval, and setting the link status to an invalid state based on the determined absence of the link frame within the second prescribed interval. The transmission of the link frame by the first network station having a length less than a minimum length of data frame enables the physical layer transceivers of other network stations to detect the link frame and thereby determine the presence of other stations on the network. Use of a link frame having a length less than the minimum data frame length also ensures that the link frame will not be processed by the other network stations, since the link frame will be classified as a runt packet and thereby discarded. Transmission of the link frame within a first prescribed interval following transmission of the data frame by the first network station also ensures that the link frame is transmitted during idle intervals, enabling the network stations to determine the link integrity without affecting network throughput.
Still another aspect of the present invention provides a network for transmission of data, the network comprising a telephone line medium, and network stations configured for sending and receiving a link frame and a data frame on the telephone line medium. Each network station includes a transmitter configured for outputting one of a data frame and a link frame, having a length less than a minimum data frame length, onto the telephone line within a first prescribed interval following transmission of a transmitted data frame, and a receiver configured for determining a link status of the telephone line medium based on detection of a frame transmitted from another one of the network stations within a second prescribed interval.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 5754552 (1998-05-01), Allmond et al.
patent: 5923663 (1999-07-01), Bontemps et al.
patent: 0 573 204 (1993-12-01), None
patent: 0 656 711 (1995-06-01), None
Advanced Micro Devices , Inc.
Vincent David R.
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