3com Ireland

3com Technologies

Other

Terence D Lockyer

Christopher J Gahan

Steven H Carter

Martin C Adams

David J Law

Tadhg Creedon

Nigel Horspool

A method of operating a repeater for a packet-based data transmission system wherein the repeater has a receiving port associated with a buffer whereby packets received at the port are temporarily stored before they are onwardly transmitted and wherein the repeater performs a contention resolution process such that if an attempted onward transmission of a packet is prevented by virtue of contention with a prior or an existing transmission, a subsequent attempt at transmission of that packet is delayed for a time which is likely to be substantially greater than a selected minimum time. The method includes examining a received packet to determine whether the packet is a multi-media packet, and giving the packet a higher priority in the contention resolution process such that if the packet is not transmitted onwardly owing to contention with a prior transmission, a fresh attempt at transmission of the packet is made on the expiry of the selected minimum time.

Method for transmitting multimedia packet data using a contention-resolution process

A multiport repeater for a local area network installation has (in addition to its conventional functions) storing access rules for the items of equipment connected to it. It reads a portion of each frame, which may be all or part of the destination address segment and/or of the source address segment and/or of the control segment of each incoming data frame, or it could be a frame or protocol identifier incorporated in opening bytes of the data segment. It compares the data that it reads with the stored access rules to determine whether the frame is permitted or not. If not, it corrupts the frame which it is in the course of re-transmitting, for example by overwriting it with meaningless digits. It may also report the source address, destination address and reason for deciding to corrupt the frame to the network controller.

Repeaters for secure local area networks

A LAN or other data network includes at least first and second repeater units for receiving data signals and repeating them to other parts of the data network and a transceiver unit for transmitting and receiving data which is connected to the first repeater unit by a primary data link and to the second repeater unit by a secondary data link. The primary data link comprises a primary transmit line for transmitting data from the transceiver unit to the first repeater unit and a primary receive line for receiving data from the first repeater unit and transmitting it to the transceiver unit; and the secondary data link comprising a secondary transmit line for transmitting data to the second repeater unit and a secondary receive line for receiving data from the second repeater unit and transmitting it to the transceiver unit. Intelligent monitoring means determines whether or not the transceiver unit is transmitting data and also whether or not data signals are present on each of the primary receive line and the secondary receive line and accordingly controls a switch unit to switch between two states in which either the primary transmit and receive lines or the secondary transmit and receive lines, but not both, are in communication with the transceiver unit. Both transmit and receive faults can be detected and appropriate action to avoid them taken.

Data networks

A multiport repeater for a local area network installation has (in addition to its conventional functions) means for storing access rules for the items of equipment connected to it. It reads a portion of each frame, which may be all or part of the destination address segment and/or of the source address segment and/or of the control segment of each incoming data frame, or it could be a frame or protocol identifier incorporated in opening bytes of the data segment. It compares the data that it reads with the stored access rules to determine whether the frame is permitted or not. If not, the repeater modifies the frame which it is in the course of re-transmitting, for example by overwriting it with meaningless digits or by encrypting it. It may also report the source address, destination address and reason for deciding to modify the frame to the network controller.

Growing community of inventors

Luton, United Kingdom

Terence D Lockyer