Abstract: A novel policer mechanism that incorporates randomization of the rate threshold which prevents “lockup” and “synchronization” problems associated with prior art policers that employ fixed rate thresholds. In one embodiment, a policer machine utilizes the well known sliding window technique to implement traffic control. In a second embodiment, a policer machine utilizes the well known token bucket technique to implement traffic control. In both embodiments, a random dimension is added to the rate threshold used by each policer algorithm. For the sliding window embodiment, the effect of randomization of the rate threshold is that the policer machine applies a scattering of rate values centered around the desired rate to the incoming traffic. For the token bucket embodiment, a random dimension is added to the empty bucket (i.e. zero tokens) threshold.

Abstract: A novel clock synchronization mechanism for recovering and distributing a centralized clock source synchronously over asynchronous networks such as optical Ethernet. A clock conversion scheme is provided whereby multiple clocks having diverse rates are converted to clock signals all having a common rate. One of the converted clocks is chosen and all downstream clock signals is derived from this clock. A high quality clock source located anywhere on the network is distributed throughout the network thus turning an asynchronous Ethernet network into a synchronous one. Synchronous TDM data streams can then be easily transported over the Ethernet network.

Abstract: A novel clock method and synchronization mechanism for recovering and distributing a centralized clock source synchronously over legacy asynchronous network devices such as legacy optical Ethernet devices that do not support synchronous Ethernet. An external device functions transparently to provide legacy optical Ethernet devices a clock synchronization and distribution mechanism. The external devices implement a clock conversion scheme whereby multiple clocks having diverse rates are converted to clock signals all having a common rate. One of the converted clocks is selected and all downstream clock signals are then derived from this clock. A high quality clock source located anywhere on the network is distributed throughout the network thus turning an asynchronous Ethernet network into a synchronous Ethernet network. Synchronous TDM data streams can then be easily transported over the Ethernet network.

Abstract: A novel mechanism for performing policy aware frame loss measurements that overcomes the problems of the prior art. The mechanism permits OAM frames to travel through the network in the same way data frames travel marked as green or yellow. The frame loss measurement is policy aware (i.e. SLA aware), taking CIR and EIR policy as well as policy in the middle of the network into consideration. In one embodiment, the value of the policer at the ingress to the client side is read just before sending an OAM frame and a potential decision value is calculated which reflects the decision that the policer would have taken if given the OAM frame at that time. If the calculated decision is to send the OAM frame as green or yellow, the frame is sent as green or yellow, accordingly. If, however, the calculated decision is to drop the frame, the frame is randomly marked as either green or yellow in accordance with the ratio of CIR to EIR. In another embodiment, red traffic (i.e.

Abstract: 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.

Abstract: An apparatus for and method of packet loss measurement for TLS connections in an MEN that overcomes the problems of the prior art. The mechanism is operative to ensure that only one copy of each received packet is counted when exiting the TLS connection (unless dropped along the path due to congestion, etc.), so that the number of egress packets counted can be accurately compared with the number of ingress packets counted. Only a single copy of each packet is marked, i.e. flagged, at ingress. Any bridging along the path that needs to duplicate the packet forwards only a single marked copy of the packet. All other copies are forwarded unmarked. At the egress from the TLS, only marked packets are counted by the egress counter. In a second embodiment, a duplication field is inserted into each packet to better track all the duplicate copies of a packet.

Abstract: A novel fast and scalable protection mechanism for protecting hierarchical multicast service in ring based networks. The mechanism of the present invention is especially suitable for use in Multi-Protocol Label Switching (MPLS) ring based networks such as Metro Ethernet Networks (MENs). The mechanism provides fast protection for MPLS based point-to-multipoint (P2MP) Label Switched Paths (LSPs) in a scalable manner. Each multicast connection on each ring in the network is split into two sub-LSPs: a primary P2MP sub-LSP originating on a primary node and a secondary P2MP sub-LSP originating on a secondary node traveling opposite to the primary path. For each node to be protected, a point-to-point protection tunnel is provisioned from that node to a secondary node that forwards the packets to the secondary path on all child rings connected to that parent ring through the protected node and that are provisioned to receive the specific multicast connection.

Abstract: An apparatus for and method of enforcing precedence of committed traffic over excess traffic that overcomes the difficulty in supporting committed over excess traffic and has particular application to distributed queuing systems. Queue control messages are generated and transmitted to other line cards to guarantee that committed traffic is not dropped when sent from multiple sources such as line interface cards to a single destination. When the level of a queue exceeds a threshold and flow control is received for the corresponding destination, the queue starts dropping excess traffic and messages indicating the queue status are sent to all other lines cards. When a line card receives a queue control message that another line card started dropping excess traffic to a specific destination, it also starts dropping excess traffic to that destination as well.

Abstract: A subport forwarding and provisioning mechanism whereby a plurality of subports implemented using slower speed processors are used to perform the packet processing for a higher speed packet stream. Outbound packets are assigned a subport based on their MPLS labels. Once assigned, the packets are forwarded to a particular subport. The output of all the subports is aggregated and combined into a single high speed packet stream and transmitted over the link. Inbound packets are received by the high speed PHY and forwarded to one of a plurality of subports. The subport chosen is the one having the same subport index as the one through which the packet was sent out over at the transmitting node. Conventional layer 2 switches can also be used whereby reserved source MAC addresses are assigned to subports. The switch forwards the inbound packets to one of the subports in accordance with the packet's source MAC address.

Abstract: A protection mechanism capable of providing both local and end-to-end connection protection for dual homed access/aggregation devices or customer-edge devices in a network. The protection mechanism provides end-to-end and fast local protection for off the shelf access devices that do not have any built in per-connection protection capabilities. The access device is connected via two separate physical uplinks to two edge switches of the network. For each connection to be protected, a main path is provisioned from one edge switch and an alternative path is provisioned from the other edge switch. The edge switches are adapted to comprise means for switching traffic from the main path to the alternative path in the event a failure along the main path is detected. Failures both in the stack portion, the core portion and in the access device uplinks are protected against.

Abstract: 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.

Abstract: An end-to-end monitoring mechanism whereby edge nodes are notified that a particular path flows through a local protection tunnel along the way. The notification mechanism utilizes OAM packets which include a link protection indication that are transmitted on the Ethernet service layer. The link protection indication may be represented by one or more flags to indicate that local protection is in place along the path. The mechanism enables fast local protection to be used with slower end-to-end protection by informing the latter when local protection is activated. In an implementation in which local-protection does not preserve the CIR of the protected traffic, the invention provides minimal interruption of Committed Information Rate (CIR) connections by minimizing the time traffic is diverted through local protection tunnels. Notification of the edge node that local protection is in use occurs very quickly, thus allowing the edge node to rapidly switch to a backup path.

Abstract: A link based network protection path calculation mechanism wherein a protection route is calculated that is guaranteed not to traverse the link it is intended to protect. The mechanism takes advantage of the fact that the same color cannot pass twice through the same optical fiber. The protection path is determined by eliminating all colors from the logical topology of the network except for the color corresponding to the link to be protected before executing the search algorithm. This serves to guarantee that the protection path calculated will not traverse the same physical fiber as the link to be protected. Virtual colors can be assigned to the links running through fiber bundles such that they do not pass through the same fiber/bundle twice.

Abstract: An optical network terminator for terminating and reducing the accumulated noise in optical networks, particularly ring based networks. The terminator eliminates problems of noise accumulation from amplifier spontaneous emission (ASE), thermal noise, etc., while providing bi-directional communications in the optical network. The optical network may have any topology including ring, star, mesh, point-to-point, etc. In the case of an optical ring, the ring is broken and an optical terminator is placed in line therewith. The optical network terminator includes a filer such as an optical demultiplexer/multiplexer or Fiber Bragg Grating (FBG) based filter. Each individual wavelength of light is filtered and a multi-wavelength optical output is generated whereby the noise accumulation is removed. Each channel is adapted to only pass a band-limited signal around the center frequency corresponding to the wavelengths supported by the particular optical ring network.

Abstract: A fast protection mechanism capable of maintaining end-to-end and fast local protection on the order of sub 50 ms for both VLAN only based connections and for connections that are based partially on VLAN technology and partially on MPLS technology. The present invention is suitable for use edge switches configured in a stack or ring topology. The NMS provisions both the main and alternative VLANs in each edge switch in the stack portions of the network. When a link failure occurs, the edge switches on either end of the failed link immediately switch all protected traffic going through that link to the alternative VLAN. The packets are then returned on the links over which they were received. Hello messages are used to signal the remote end that a link failure has occurred and that protected traffic must be switched to the main or alternative VLAN in accordance with the VLAN the Hello message was received on.

Abstract: A 1:N protection scheme that provides both equipment and line protection against a single point of failure for a network hub situated in an optical ring network. The invention is suitable for use in DWDM based optical ring networks, and in particular, in networks constructed having a logical star over physical ring topology. The hub is modified to comprise N+1 transceivers, assuming an N channel DWDM network wherein each of the N transmitters operates using a different wavelength. Protection against line failures is achieved by optically splitting the transmit signal into two paths and transmitting each separately in opposite directions over the ring (i.e. 1+1 protection). In the event of a line failure, the other signal should still arrive at the destination. Protection against equipment failures is achieved through the use of a spare transceiver having a tunable wavelength of operation (i.e. 1:N protection).

Abstract: 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.