3com Corporation

Atrica Israel Ltd.

Atrica Ireland Limited

Amir Lahat

Yackov Sfadya

Yoav Honig

Pavel Hardak

Gila Klein

Meir Ohana

Lior Shabtay

Zvika Bronstein

Yaron Raz

Yoav Kluger

Offer Pazy

Ronen Ofek

On Paradise

Alex Arnon

A centralized clock distribution mechanism for synchronous TDM communications traffic transported over asynchronous networks such as Ethernet networks. The centralized clocking mechanism of the present invention distributes a high accuracy central clock source to a plurality of CES modules over an Ethernet network. Clock synchronization information based on a high quality clock reference source is distributed to circuit emulation service (CES) modules in the network. CES modules receive the clock synchronization information and use it to reconstruct a local clock. A plurality of clock distributors provide clock redundancy whereby each CES module selects the best clock source to use in reconstructing the local clock.

Centralized clock synchronization for time division multiplexed traffic transported over Ethernet networks

A clock reconstruction mechanism for synchronous TDM communications traffic transported over asynchronous networks such as Ethernet networks. The invention is applicable to edge switches in Metropolitan Area Networks (MANs) that transport legacy TDM traffic using a Circuit Emulation Services (CES) module whereby TDM traffic is encapsulated and transported across the Ethernet network where it is de-encapsulated and clocked out to the destination. The mechanism encapsulates the input TDM data stream into Ethernet packets and inserts a network timestamp within the packet. At the destination CES, a local timestamp is generated for each received packet as it is received. The network timestamp is extracted and input along with the local timestamp to a Digital Time Locked Loop (DTLL) which is operative to accurately reconstruct the original transmit TDM clock. The filter in the DTLL performs a Least Squares Regression (LSR) algorithm and Infinite Impulse Response (IIR) filter algorithm to generate a clock control signal for adjusting the clock generated.

Clock reconstruction for time division multiplexed traffic transported over asynchronous ethernet networks

A transport facility adapted to transport TDM bit streams using IP packets over an asynchronous Ethernet network. TDM bit streams such as E1, T1, E3, T3, OC-3, OC-12, STM-1, STM-4, etc. are received, buffered and encapsulated into Ethernet frames. The Circuit Emulation Device (CED) receives, buffers and assembles in real-time ingress data from TDM ports into Ethernet Frames and forwards them to an Ethernet interface. The TDM data is encapsulated within RTP, UDP and IP packets before being encapsulated within an Ethernet frame. In the egress direction, Ethernet frames enter the encapsulation/segmentation processor from the Ethernet port and the IP, UDP and RTP packets are extracted from the frame. TDM data is extracted and the bit streams are re-generated and forwarded to the TDM ports for transmission over legacy TDM facilities.

Facility for transporting TDM streams over an asynchronous ethernet network using internet protocol

A mechanism and associated protocol for performing Service Level Agreement (SLA) measurements in a communications network. The measurements obtained are used to perform various SLA parameter calculations such as delay, round trip delay, one way jitter and bandwidth related calculations. SLA measurement request and response messages are stamped with time and bandwidth counters by the client and remote ends of a connection. The resultant data is used to perform the calculation of SLA parameters.

Mechanism and protocol for per connection based service level agreement measurement

Crossbar switch utilizing broadcast buffer and associated broadcast buffer management unit

A novel crossbar switching matrix that improves the transmission of variable length broadcast packets by greatly reducing transmission latency time. Unicast traffic is halted in the middle of packet transmission operations and the broadcast packet is transmitted. Once the broadcast packet has finished transmission, unicast packet transmission resumes without any loss of data. A unicast buffer is used to store the unicast packet while the broadcast packet is being transmitted. A broadcast buffer is used to buffer the broadcast packet as it egresses from the switch matrix. In this fashion, the broadcast information is given high priority and passes quickly through the switch without the large delays associated with the prior art switch matrixes. The crossbar switch matrix of the present invention is applicable to any switching matrix adapted to switch variable length data units.

Crossbar switching matrix with broadcast buffering

A system for assigning wavelengths in an optical switch to enable unicast, broadcast and multicast traffic to be sent through the switch. The optical switch enables data to be switched in the optical domain as opposed to conventional switching in the electrical domain. This permits a very high data capacity and data rate using well-known WDM technology. Tunable transmitters are configured to connect each input port to a different output port within the switch. During each cycle of the switch the transmitters are programmed to a particular wavelength, the wavelength determining the destination output port. Interface (I/F) cards issue requests to send data to the switch and receive acknowledgements indicating permission to send data to a particular destination port. A controller processes the requests received from the I/F card to generate a set of acknowledgements. A two-way round robin technique is used to select the destination ports for each I/F card based on the requests received.

System for assigning wavelengths in a wave division multiplexing based optical switch

An ATM switch which utilizes an all optical switching fabric to perform switching functions. The switch is based on fiber optics and Dense Wavelength Division Multiplexing (DWDM) technologies. The switch utilizes a centrally located optical switch fabric with multiple distributed interface cards. The switch module comprises an N X N passive star coupler which functions to pass the optical signal input present at any of its input ports to all of its output ports. Each output port has associated with it a unique wavelength. An optical filter set to the wavelength functions to block all wavelengths except for the wavelength associated with that particular output port. The ingress portion of each receive/transmit interface module comprises a tunable optical transmitter that is set to the wavelength corresponding to the desired destination output port. Cells are transmitted to the switch module on that wavelength and only the optical receiver associated with that wavelength receives the optical signal, the other output ports functioning to filter the signal. In this fashion, ATM cells received are switched to any output port utilizing WDM optical processing.

Asynchronous transfer mode switch utilizing optical wave division multiplexing

A multicast queue for controlling cell traffic to individual output queues in a multicast group in accordance with the backpressure information generated by each output queue. One or more destinations asserting the backpressure signal are identified and, in response, the corresponding one or more destinations are removed from the 'distribution list' in the routing tag associated with the connection. In this fashion, a cell that originated at a multicast source queue can be transmitted to the remaining destination queues that are not in a congested state. Cell traffic will cease only to those destination queues that generated the backpressure signal indicating that they are full. If the congestion at an output port is removed, the corresponding backpressure bit is reset and cell traffic resumes to that particular output port.

Backpressure responsive multicast queue

An optical switch utilizing WDM or DWDM techniques for use in both WAN and LAN environments. Each input to the switch is assigned a separate wavelength via a tunable transmitter. The output of the transmitters are input to a star coupler which combines all the optical signals into a single optical output signal. This signal is input to an optical demultiplexor which functions to split the incoming optical signal into a plurality of separate wavelengths with each wavelength steered to a particular output port. The output of each port, corresponding to a particular wavelength, is then converted into an electrical signal by a receiver. Unicast, broadcast and multicast calls are supported. A plurality of unicast connections can be established simultaneously by assigning each tunable transmitter a different wavelength such that all wavelengths are mutually exclusive with each other. In a broadcast connection, the source node transmits and all output ports receive the optical signal on the particular wavelength assigned to that port. The rest of the input ports are placed in an idle state. The output of each port is input to a multiplexor along with an output of the optical demux dedicated to broadcast traffic. A controller switches the multiplexors to output the broadcast signal such that all receivers output the same signal. Multicast traffic is handled similarly except that only selected multiplexors are switched. The remaining multiplexors carry unicast traffic as normal. As a result, the output ports of the members of the multicast group all output the same signal.

Growing community of inventors

Kibbutz Givat-Brenner, Israel

Amir Lahat