News Column

Patent Issued for Network System, Layer 2 Switch, and Method of Detecting Occurrence of a Fault in a Network

July 3, 2014



By a News Reporter-Staff News Editor at Computer Weekly News -- Alaxala Networks Corporation (Kawasaki, JP) has been issued patent number 8755288, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Akahane, Shinichi (Hachioji, JP); Kaganoi, Teruo (Yokohama, JP); Nagata, Tetsuya (Yokohama, JP).

This patent was filed on July 27, 2011 and was published online on June 17, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention relates to detection of occurrence of a fault in a network.

"In a system configuration where two communication devices (for example, layer 2 switches) are connected with each other via a network, two bidirectional paths (communication paths) are established between the two communication devices. When a fault occurs in one of the two paths (called 'unidirectional path fault'), various problems arise; for example, frame looping on the network. UDLD (Unidirectional Link Detection) protocol has been proposed for detection of such a unidirectional path fault (Cisco System Unidirectional Link Detection (UDLD) Protocol (RFC:5171), Cisco Systems, April 2008, Retrieved from the Internet; on Jun. 20, 2010).

"According to the UDLD protocol, each of the two communication devices sends a link health check frame to the other communication device and detects the occurrence of a unidirectional link fault based on reception or non-reception of a link health check return frame sent back from the other communication device.

"The UDLD protocol applies the software configuration to analyze various parameters included in the received frame and detects the occurrence of a unidirectional path fault based on the result of the analysis. This arrangement requires a relatively long time for detection of a fault. It is thus desired to shorten the time period required for detecting a unidirectional path fault."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "There is accordingly a requirement for detecting a unidirectional path fault between two communication devices within a short time period.

"In order to address at least part of the requirement described above, the present invention provides various aspects and embodiments described below.

"One aspect of the present invention is directed to a network system, comprises: a first communication device being set up with a first address; and a second communication device connected with the first communication device via a network and being set up with a second address, wherein the first communication device includes: a monitor frame transmitter configured to generate a monitor frame including the second address as a destination address and the first address as a source address, and to output the generated monitor frame to the network; and a monitoring-response frame monitor configured to monitor reception of a monitoring-response frame sent back from the second communication device, wherein the second communication device includes: a monitoring-response frame transmitter configured to, in response to reception of the monitor frame, generate the monitoring-response frame by exchanging the destination address in the received monitor frame for a source address and the source address in the received monitor frame for a destination address, and output the generated monitoring-response frame to the network.

"In the network system according to this aspect of the present invention, when receiving a monitor frame, the second communication device generates a monitoring-response frame by exchanging the destination address in the received monitor frame for a source address and the source address in the received monitor frame for a destination address. The procedure of generating the monitoring-response frame is thus readily achievable by hardware processing, which results in speeding up the processing. The first communication device monitors reception of the monitoring-response frame to detect the occurrence of a path fault between the first communication device and the second communication device. This arrangement of the network system does not require software processing, thus enabling the occurrence of a unidirectional path fault between the first communication device and the second communication device to be detected within a short time period.

"In one preferable embodiment of the network system, the second communication device further includes: a receive buffer configured to store the received monitor frame; and a send buffer configured to store the generated monitoring-response frame, and the monitoring-response frame transmitter reads out the destination address from the monitor frame stored in the receive buffer and records the read-out destination address as the source address of the monitoring-response frame stored in the send buffer, while reading out the source address from the monitor frame stored in the receive buffer and recording the read-out source address as the destination address of the monitoring-response frame stored in the send buffer.

"The network system of this embodiment enables the hardware configuration to perform the procedure of setting the destination address in the received monitor frame to the source address of the monitoring-response frame and the source address in the received monitor frame to the destination address of the monitoring-response frame.

"In another preferable embodiment of the network system, the first communication device further includes: a port configured to send and receive at least the monitor frame and the monitoring-response frame; and a port controller configured to set a frame sending/receiving-enabled state as a logical status of the port when the monitoring-response frame monitor detects reception of the monitoring-response frame at the port, and to set a frame sending/receiving-disabled stated as the logical status of the port while when the monitoring-response frame monitor does not detect reception of the monitoring-response frame at the port.

"The network system of this embodiment cuts off frame sending/receiving at the port, where a fault is detected. This arrangement prevents frame looping in the network system, due to the occurrence of a fault.

"In another preferable embodiment of the network system, the monitor frame transmitter sets a monitor frame identifier representing identification of the monitor frame, as part of the monitor frame, and in generating the monitoring-response frame, the monitoring-response frame transmitter changes the monitor frame identifier set in the monitor frame to a monitoring-response frame identifier representing identification of the monitoring-response frame.

"The network system of this embodiment allows for easy discrimination between the monitor frame and the monitoring-response frame. In the network system of this embodiment, when the second communication device is configured to send a monitor frame to the first communication device, the first communication device can readily identify whether the incoming frame sent from the second communication device is either a monitoring-response frame sent back as a return to the monitor frame sent from the first communication device or a monitor frame newly sent from the second communication device.

"In another preferable embodiment of the network system, the monitoring-response frame transmitter generates the monitoring-response frame by changing only the destination address and the source address in the monitor frame.

"The network system of this embodiment generates the monitoring-response frame by the simpler procedure and thus enables detection of the occurrence of a fault within a shorter time period. The monitoring-response frame is generated by changing only the settings of the destination address and the source address in the received monitor frame. In another system configuration including one or more other communication devices (frame relay devices) provided between the first communication device and the second communication device, the one or more other communication device is allowed to relay the monitoring-response frame, as well as a general frame, to the first communication device. This arrangement enables the occurrence of a fault to be detected in a large-scaled network system, while enabling the occurrence of a fault between the first communication device and the second communication device to be detected in a modified system configuration having one or more other communication devices (frame relay devices) provided between the first communication device and the second communication device.

"In another preferable embodiment of the network system, the first communication device further includes: a user interface configured to set approval or non-approval of generation and transmission of the monitoring-response frame by the second communication device.

"The network system of this embodiment enables the user to readily set approval or non-approval of generation and transmission of the monitoring-response frame by the second communication device.

"In another preferable embodiment of the network system, both the first communication device and the second communication device are layer 2 switches.

"The network system of this embodiment enables the occurrence of a fault in the layer 2 network between the layer 2 switches to be detected within a short time period.

"Another aspect of the invention is directed to a layer 2 switch being set up with a second address and connected with a communication device being set up with a first address via a network comprises: a monitoring-response frame transmitter configured to, in response to reception of a monitor frame that is a layer 2 frame including the second address as a destination address and the first address as a source address, generate a monitoring-response frame by exchanging the destination address in the received monitor frame for a source address and the source address in the received monitor frame for a destination address, and output the generated monitoring-response frame to the network.

"When receiving a monitor frame, the layer 2 switch according to this aspect of the invention generates a monitoring-response frame by exchanging the destination address in the received monitor frame for a source address and the source address in the received monitor frame for a destination address. The procedure of generating the monitoring-response frame is thus readily achievable by hardware processing, which results in speeding up the processing. This arrangement of the layer 2 switch enables the occurrence of a unidirectional path fault between the layer 2 switch and the communication device to be detected within a short time period.

"Another aspect of the invention is directed to a method of detecting occurrence of a fault in a network connecting a first communication device being set up with a first address and a second communication device being set up with a second address, the method comprising: (a) the first communication device generating a monitor frame including the second address as a destination address and the first address as a source address, and outputting the generated monitor frame to the network; (b) in response to reception of the monitor frame, the second communication device generating a monitoring-response frame by exchanging the destination address in the received monitor frame for a source address and the source address in the received monitor frame for a destination address, and outputting the generated monitoring-response frame to the network; and the first communication device monitoring reception of the monitoring-response frame output from the second communication device.

"In the method according to this aspect of the invention, the second communication device generates a monitoring-response frame by exchanging the destination address in the received monitor frame for a source address and the source address in the received monitor frame for a destination address. The procedure of generating the monitoring-response frame is thus readily achievable by hardware processing, which results in speeding up the processing. The first communication device monitors reception of the monitoring-response frame to detect the occurrence of a path fault between the first communication device and the second communication device. The method of this arrangement does not require software processing, thus enabling the occurrence of a unidirectional path fault between the first communication device and the second communication device to be detected within a short time period.

"The principle of the present invention may be actualized by diversity of other applications, for example, a control method of the network system or the layer 2 switch, a computer program including the functional blocks of the network system or the layer 2 switch, and a computer program product."

For the URL and additional information on this patent, see: Akahane, Shinichi; Kaganoi, Teruo; Nagata, Tetsuya. Network System, Layer 2 Switch, and Method of Detecting Occurrence of a Fault in a Network. U.S. Patent Number 8755288, filed July 27, 2011, and published online on June 17, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8755288.PN.&OS=PN/8755288RS=PN/8755288

Keywords for this news article include: Software, Alaxala Networks Corporation.

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Source: Computer Weekly News


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