An apparatus to detect stations having duplicated addresses, the stations of the type connected in a computer communications network, the stations of the type capable of having an assigned address and having a list of addresses for comparison with a destination address field of a frame detected on the network is disclosed. The apparatus does a transmit self test, and sets a self indicator to "pass" in the event that the self test frame is received, and sets the self indicator to "timeout" in the event that a timeout occurs. The apparatus does a neighbor response test, and sets a neighbor indicator to "timeout" in the event that a timeout occurs, and sets the neighbor indicator to "pass" in the event that a received response frame indicates no destination address match, and sets the neighbor indicator to "fail" in the event that a received response frame indicates that a destination address match did occur. The apparatus tests both the self indicator and the neighbor indicator, and in response to the testing of the self indicator and the testing of the neighbor indicator sets a duplicate address indicator in one of three states, a first state of the three states indicating that there is no duplicate address detected, a second state of the three states indicating that there is a duplicate address, and the third state of the three states indicating an unknown condition.
During data transmission between a receiver and each of terminal devices in a disaster prevention supervisory system, the receiver sends calling data including address data for specifying a specific terminal device to the side of terminal devices in a transmission error detection mode. The receiver also causes the terminal device specified by the address data to return error detection response data including self-address data and check data for a current level previously defined. When the current level of the check data in the error detection response data received by the receiver is higher than the level previously defined due to the response of a plurality of terminal devices, it is decided that an abnormality is present in the terminal device of the address specified by the calling data. The arrangement provides a transmission error detecting method for securely detecting error in data transmission between the receiver and each of the terminal devices and enables improvement in the reliability of data transmission.
A control system comprises modules, and control means to control assignment of addresses to the modules. Each particular module has a particular number. The control means iteratively determines which one of the modules has an extreme one among the particular numbers. Each module is stimulated to conditionally respond if its particular number lies within a certain range. The range is altered until the module with the extreme is found. This process is repeated for the next lower extreme until all modules have been validated. Addresses are then created and stored in the modules for access during operational use.
A multisite network switch for a series of RF digital trunked radio transceivers and dispatcher consoles. The switch establishes audio communications between different sites and various dispatcher consoles. The multisite switch has a distributed architecture in which each node of the switch is supported by a microprocessor controlled card. These nodes perform all of the logical functions of the switch. When the switch is booted-up or reset, each node executes a dynamic address generation algorithm to select a unique address and resolve any address conflicts with other nodes.
In a local area network (LAN) test instrument, a method for detecting duplicate internet protocol (IP) addresses without disrupting the LAN is provided. The LAN test instrument provides a method of choosing an IP address for itself without disrupting the ARP caches of devices connected to the LAN. Duplicate IP addresses between devices on the LAN may then be tested using a series of network broadcasts chosen to elicit responses from as many nodes on the network as possible because some nodes respond to some types of broadcasts and not others. A data base of the various nodes is collected and the newly arriving responses are dynamically compared with the responses already in the data base to detect duplicate IP addresses. Separate entries in the data base for devices having duplicate IP addresses are maintained and then displayed to the user of the LAN test instrument to selectably and reliably communicate with the devices having duplicate IP addresses for further diagnosis and correction.
A distributed protocol for allocation of multicast addresses. A first node of a network sends an address request message identifying (1) a requested in multicast address, and (2) a multicast group identifier to which the requestor belongs. The request is in multicast on a network address reserved for address resolution. All other nodes of the network monitor the reserved network address for address request messages. If a second node receiving the address request message has already allocated the requested multicast address, then the second node sends an acknowledgment message identifying (1) the already allocated in multicast address, and (2) the multicast group for which the address has been allocated. This acknowledgment is transmitted on the same reserved network address on which the address request was sent. The first node, monitoring the reserved network address, receives the acknowledgment message. If the multicast group identified in the acknowledgment message matches the multicast group to which the first node belongs, then the first node also allocates the requested network address. If the multicast group identified in the acknowledgment message does not match the multicast group to which the first node belongs, then the first node abandons the requested network address. If the first node does not receive an acknowledgment message in response to any number of address request messages repeated for the same requested multicast address, then the first node either (1) allocates the requested network address, or (2) abandons the requested network address, if the node is not the first member of a multicast group to request allocation of the address. If address allocation succeeds, then the first node uses the allocated network address for multicasting. If address allocation fails, then the first node is free to select a different multicast address to request.
