Nortel Networks Corporation

Digital Equipment Corporation

Cabletron Systems, Inc.

Enterasys Networks, Inc.

Nicholas Ilyadis

Ronald M Salett

David B Fite, Jr

Da-Hai Ding

Sandeep P Golikeri

William J Tiffany

Richard W Graham

Timothy Cunningham

Manish Patel

Nelson Kong

A method and apparatus for providing data communication between stations on a network which optimizes the amount of resources required for a network switch. A first data frame is encoded with a source station identifier for the first station and a source switch identifier for the first switch. The first data frame is sent from the first switch to the second switch. A station list in the second switch is updated to indicate that the first station is associated with the first switch. Subsequent data frames having the same destination as the first switch are sent directly to the second switch. Any switch on the network need only identify the local ports attached to the switch, plus the number of switches on the network. The task of identifying all of the ports on the network is distributed across all switches on the network.

Stackable switch port collapse mechanism

An address reporting technique for reporting address information in a distributed communication environment retrieves locally owned address information from each of a number of distributed address databases, sorts the address information according to a predetermined sorting scheme, and reports the sorted address information. Each address database is maintained by one of a plurality of interconnected modules. A reporting module reports address information by retrieving locally owned address information from its address database, retrieves locally owned address information from each of the other interconnected modules, sorts the address information according to a predetermined sorting scheme, and reports the sorted address information. The reporting module retrieves the locally owned address information from each of the other interconnected modules by sending a request message to the other interconnected modules and receiving a response message from each of the other interconnected modules including the locally owned address information from the module. A module that receives the request message retrieves locally owned address information from its address database, formats a response message, and sends the response message to the reporting module. The reporting module may indicate a starting address, in which case each module retrieves from its address database a predetermined number of locally owned address entries starting with a first locally owned address entry that is lexicographically greater than the starting address.

System, device, and method for address reporting in a distributed communication environment

A distributed address database management technique involves maintaining an address database by each of a number of interconnected modules. Each module maintains a number of locally owned address entries and a number of remotely owned address entries in the address database. Each module monitors the status of its locally owned address entries, maintains the locally owned address entries based upon the status, and provides the status to the other interconnected modules. Each module maintains the remotely owned address entries based upon the status received from the other interconnected modules. When a module adds a locally owned address entry to its address database, the module notifies the other interconnected modules, which in turn add a corresponding remotely owned address entry to their respective address databases. When a module purges a locally owned address entry from its address database, the module notifies the other interconnected modules, which in turn purge the corresponding remotely owned address entries from their respective address databases. Each module may periodically send a keep-alive message including a list of active addresses to the other interconnected modules, which maintain a persistence timer for each of the remotely owned address entries and purge a particular remotely owned address entry if the corresponding persistence timer expires before receiving a keep-alive message identifying the remotely owned address entry as an active remotely owned address entry. Upon receiving a keep-alive message, a module adds a remotely owned address entry for a particular address to its address database if such a remotely owned address entry is not already maintained in the address database. A module purges all remotely owned address entries from its address database if the module is reconfigured to operate in a stand-alone mode. A module purges all remotely owned address entries associated with a particular interconnected module if that particular interconnected module is removed.

System, device, and method for address management in a distributed communication environment

An enhanced spanning tree protocol for data communications networks having a multi-link trunk. In one embodiment, configuration messages are transmitted from boxes of the data communications network. In one embodiment, the configuration messages that are transmitted through all physical links of the same logical link, or multi-link trunk, include the same port Identifier. A network device that receives the configuration messages is therefore able to identify all of the physical links of a logical link. The enhanced spanning tree protocol according to one embodiment of the present invention considers all of the physical links of a multi-link trunk as a single logical link when identifying and removing loops in the data communications network to form a spanning tree.

Method and apparatus providing a spanning tree protocol for a data communications network having a multi-link trunk

A method and apparatus for providing data communication between a source station having multiple connections to a first switch and a destination station having multiple connections to a second switch. A trunk identifier to each port on the first switch and each port on the second switch. A data frame is encoded with the trunk identifier for an ingress port on the first switch. The data frame is sent to the second switch from the first switch. A list of egress ports for the destination station is obtained from a station list contained in the second switch. An egress port is selected from the list of egress ports based upon the source address, destination address and trunk identifier. The data frame is sent to the destination station through the selected egress port.

Distributed multi-link trunking method and apparatus

Bus access is arbitrated among modules connected to a common bus. Each module has a priority level and an arbitration number assigned to it. More than one module can have the same priority level. For each priority level, the arbitration numbers assigned are unique. When two or more modules attempt bus access at the same time, the one with the higher priority level wins access. If the priority levels are the same but one module has already accessed the bus, the module that has been waiting wins access. If the modules have the same priority level and have been waiting then the module with the highest arbitration number wins access.

Method and apparatus for arbitrating bus access amongst competing devices

A method and an apparatus providing data communications among network devices using tagged and untagged frame formats. In one embodiment, a virtual local area network (VLAN) is implemented using frames that may be transferred among network devices in both tagged and untagged formats. In one embodiment, the frames are transferred among network switches in an untagged format, independent of whether the source devices sent the frames in a tagged or untagged format. In addition, destination devices may receive frames in either a tagged or an untagged format, independent of whether the source devices originally send the frames a tagged or untagged format. Cyclic redundancy check (CRC) code information contained in the frames as originally sent is left unchanged when transferred among the switches of the VLAN, even though the frames may have been modified prior to transfer among switches. New CRC code information is generated for reformatted frames in the switches containing the outbound ports such that reformatted frames with valid CRC codes are forwarded to destination devices. In the event that a switch receives a corrupt frame from a source device, a corresponding corrupt reformatted frame is forwarded to the destination device from the switch.

Method and apparatus providing network communications between devices using frames with multiple formats

A method and an apparatus for adjusting an interpacket gap. In one embodiment, a plurality of network devices are tightly coupled together in series. Data is transmitted and received by the network devices in packets with interpacket gaps interposed between each packet. Buffers are included in each network device to serve as elasticity buffers for the data being transmitted between the network devices. The first upstream network device transmits interpacket gaps having an increased size. Downstream network devices may shrink increased size interpacket gaps to reduced size interpacket gaps if the internal buffers are filled to or above a high water mark. However, downstream network devices are not allowed to shrink the size of reduced size interpacket gaps that are received, even if their internal buffers are filled to or above the high water mark.

Method and apparatus for adjusting an interpacket gap using a network device in a data communications network

An arbitration unit contains a method of arbitration which includes distributed arbitration, a priority mechanism to support different classes of traffic, a unique arbitration ID bits for each module, a round robin arbitration within a given priority level to produce fair access to a bus 36, an arbitration timeout, and a bandwidth allocation between priority levels. The method of round robin bus arbitration includes the steps of providing a plurality of modules, providing a bus having a plurality of data lines, the bus connecting the plurality of modules, the bus having an arbitration unit, setting the bus to a wait state, signaling a first bus request to the bus by a first module needing to transmit a first plurality of data packets on to the bus, the first module having a first module priority level and a first unique arbitration number, signaling a second bus request to the bus by a second module needing to transmit a second plurality of data packets on to the bus, the second module having a second module priority level and a second unique arbitration number, establishing a bus priority according to a comparison of the first module priority level and the second module priority level, asserting the first unique arbitration number on the bus by the first module, asserting the second unique arbitration number on the bus by the second module, determining whether the first module and the second module have been waiting for the bus, comparing the first unique arbitration number and the second unique arbitration number, scheduling transmission of data packets in response to the steps of determining and comparing, and repeating the steps of setting, signaling, establishing, asserting, determining, comparing, and scheduling.

Method of round robin bus arbitration

A network hub for interconnection of modular devices, such as Ethernet repeaters, bridges, and routers is provided. Such a network hub efficiently interconnects the modular devices to each other. The inter-module connection is not through standard Ethernet media cabling or interconnections so that the hop count does not exceed one for all external connections, as defined by IEEE 802.3 Repeater Specification. Timing synchronization is provided by a global synchronization mechanism. Collision detection is provided by a series of lines that distribute the collision to all modules connected to the hub. The network hub comprises an inter-module bus having a backplane, the backplane able to connect to a number of modules, a clock, a method for transmitting data received by a first module across the inter-module bus to a second module and transmitting the data to ports of the second module, and a method for synchronizing the data as it is transmitted by the second module to the clock within the hub. With such an arrangement, timing of the data transfers and state exchanges on the inter-module connection are such that all state and timing specifications of the IEEE 802.3 repeater specification are satisfied for all ports on all repeater modules and all stations.

Growing community of inventors

Pepperell, MA, United States of America

Nicholas Ilyadis