Abstract: Algorithms and data structure are described for constructing and maintaining a clock distribution tree (“CDT”) for timing loop avoidance. The CDT algorithms and data structure allows a node to make an automated and unattended path switch to the most desirable clock source in the network. In response to a network topology change, a clock root node distributes new clock paths to all nodes in the network. In particular, the root node calculates a new clock path for each affected node by building a clock source topology tree, and identifying from that tree a path to the network node from a clock source of higher or equal stratum relative to that network node. The root node then sends a network message to each node indicating the new path that the node should use. Each node receives the message and compares the new path with the existing path. If the paths are different then the node acquires the new path just received in the message. If the paths are the same then the node does nothing and discards the message.

Abstract: Three dimensional RF tag signatures may be obtained from a three dimensional RF tag or multiple two or three dimensional RF tags so that information in addition to presence information may be obtained. In one embodiment, a three dimensional RF tag having two or more power coils disposed in non-coplanar planes enables the coils to experience different levels of excitation from an electromagnetic field. This information may be transmitted along with the RF tag response to enable the orientation of the RF tag relative to an RF tag reader to be determined. In another embodiment, multiple RF tags (either standard RF tags or three dimensional RF tags) may be used on a given article and a response signature from the article as a whole may be recorded. The three dimensional response signature thus collected may be compared with previous versions of the response signature to determine if the article has been altered.

Abstract: Various techniques for queue management based on random early detection (RED) are disclosed herein. In particular, a method for generating a drop probability for an incoming packet in a device having a queue to buffer packets between segments of a network is provided. The method comprises determining, upon receipt of an incoming packet, a size of the queue and determining an error based at least in part on a difference between the queue size and a threshold. The method further comprises determining a drop probability for the incoming packet based at least in part on the error and a constant gain factor. The constant gain factor may be based at least in part on a linearized second order dynamic model of the network.

Abstract: A method and apparatus for locating in a list of pre-defined codes, a longest code matching a given code. The method and apparatus involve producing a search mask encoding at least one portion of said given code and comparing the search mask to a search key having a Prefix Node Bit Array (PNBA) in which a bit is set active in at least one of a plurality of bit positions corresponding to possible bit combinations of bits in a bit string having a length equal to or less than the longest predefined code in the plurality of pre-defined codes and arranged by the lengths of possible bit combinations and by numeric values of the bit combinations, to identify a common active bit position in the search key and the search mask corresponding to one of the pre-defined codes having a length greater than all others of said pre-defined codes which correspond to common active bit positions.

Abstract: A technique for adaptively distributing a web server request in a system having a plurality of web servers is disclosed. In one embodiment, the technique is realized by first generating a web server request distribution function for each of the plurality of web servers based upon performance measures of each of the plurality of web servers, wherein each of the plurality of web servers is assigned a respective probability range based upon each respective web server request distribution function. A random probability number is then generated for a web server request. The particular probability range encompassing the random probability number is then determined so as to identify the corresponding web server to which the web server request is to be distributed.

Abstract: A technique for implementing an admission control scheme for data flows is disclosed. In one embodiment, the technique is realized by determining a current error value in response to a queue size in a packet buffer; generating a packet drop probability based at least in part on the current error value; receiving a data packet having a data type; and determining whether to reject or accept the received data packet at a queue based at least in part on the packet drop probability and a predetermined flow rejection threshold. In addition, the technique may involve determining whether a randomly generated number is less than or equal to the packet drop probability and determining whether a count variable is greater than or equal to an inter-drop interval.

Abstract: A rotator switch includes active and redundant tandem buffers used to switch information units through the switch. The tandem buffers are interconnected to inputs and outputs by way of commutators. Information provided to one or more of the active buffers is provided to a redundant buffer. If an active tandem buffer fails, the switch may use the redundant buffer in place of the failed active buffer. A further rotator switch is formed using a plurality of switching blocks. Each switching block includes its own set of tandem buffers, and ingress and egress commutators to interconnect the tandem buffers to inputs and outputs. The plurality of switching blocks is interconnected using additional commutators. At least one of these switching blocks is redundant and is provided with information provided to an active switching block. In the event of failure of an active block, the switch may use a redundant switching block in place of the failed or replaced active block.

Abstract: Label information used by a downstream LSR is mirrored on an upstream LSR. In particular, a copy of the label information database in the downstream LSR from LDP sessions is stored on the upstream LSR. The label information database and corresponding mirror are synchronized. The mirror is employed to facilitate recovery from control plane failure through comparison of the label information database with the mirror. For example, the intersection of the label information database and the mirror may be calculated and employed as the updated label information database and mirror.

Abstract: A system and method for synchronizing a local clock to a reference clock using a linear model of the error between the local clock and the reference clock is disclosed. In one embodiment, a direct smoothing process is used in conjunction with the linear model to estimate a frequency offset by which the frequency of an oscillator of the local clock is adjusted. Also disclosed herein is a phased-lock loop (PLL) adapted to synchronize a local clock with a reference clock using the direct smoothing process, as well as a system implementing the PLL for timing the playout of data received from a transmitter.

Abstract: A technique for multicasting an optical frequency channel in a multi-channel optical system is disclosed. In one particular exemplary embodiment, the technique may be realized as a method for multicasting an optical frequency channel in a multi-channel optical system. The method comprises splitting a first optical frequency channel in a pair of adjacent optical frequency channels into a first split optical frequency channel and a second split optical frequency channel. The method also comprises converting the optical frequency of the second split optical frequency channel to the optical frequency of the second optical frequency channel in the pair of adjacent optical frequency channels. The method further comprises selectively directing the first split optical frequency channel and the converted second split optical frequency channel to separate destinations.

Abstract: Techniques for dilating and reverse dilating optical channels in an optical system are disclosed. In one particular exemplary embodiment, a technique for dilating optical channels may be realized as a method for dilating optical channels in a system having W optical frequencies. The method comprises receiving a plurality of optical channels each operating at a respective one of the W optical frequencies. The method also comprises converting the optical frequency of each of the plurality of optical channels into a respective converted optical frequency defined by ?+?.f, wherein f represents the optical frequency of each of the plurality of optical channels, and wherein ?=±1 and ? are constant for all of the plurality of optical channels. The method further comprises directing each of the plurality of optical channels based at least in part upon the respective converted optical frequency of each of the plurality of optical channels.

Abstract: A technique for routing data within an optical network having a plurality of network nodes is disclosed. In one embodiment, the technique is realized by receiving data at a first network node via a first optical signal having a first wavelength. The first wavelength corresponds to a first optical frequency, and the first optical frequency is mapped to a first binary representation. The first binary representation is divided into a first plurality of fields, wherein at least one of the first plurality of fields corresponds to a routing label in a first label stack. A top routing label in the first label stack indicates a second network node. Based at least partially upon the top routing label, the data is transmitted from the first network node to the second network node via a second optical signal having a second wavelength. The first wavelength may be either the same as or different from the second wavelength.

Abstract: The TCP receiver's advertised window (i.e., the receive buffer of a TCP connection) limits the maximum window and consequently the throughput that can be achieved by the sender. Thus, the idea behind TCP rate control is to match the offered network load to the available resources by modifying at an intermediate network device, the receiver's advertised window in TCP acknowledgments returning to the sources. In this disclosure, we propose a new TCP rate control scheme for a shared buffer where the buffer is logically organized into multiple queues. In the scheme, dynamic buffer thresholds are used to ensure efficient and fair usage of buffer memory among the queues. Conventional schemes allocate buffer space to each queue through the use of static buffer thresholds. This can result in unnecessary packet drops which leads to poor network performance since congested or heavily loaded queues cannot gain access to buffers not utilized by lightly loaded queues.

Abstract: A technique for synchronizing clocks in a network is disclosed. In one exemplary embodiment, the technique may be realized as a method for synchronizing clocks in a network. The method comprises receiving a first timestamp and a second timestamp, each indicating a respective time instance as determined by a first clock signal within the network. The method also comprises measuring a first time interval between the first timestamp and the second timestamp. The method further comprises generating a difference signal representing a difference between the first time interval and a second time interval, and generating a second clock signal based upon the difference signal such that the second clock signal is synchronized with the first clock signal.

Abstract: A system and method for synchronizing a local clock to a reference clock using a linear model of the clock error between the local clock and the reference clock is disclosed. In one embodiment, a double-exponential smoothing process is used in conjunction with the linear model to estimate a frequency offset by which the frequency of an oscillator of the local clock is adjusted. Also disclosed herein is a phased-lock loop (PLL) adapted to synchronize a local clock with a reference clock using the double-exponential smoothing process, as well as a system implementing the PLL for timing the playout of data received from a transmitter.

Abstract: A technique for interchanging wavelengths in a multi-wavelength system having W wavelength channels is disclosed. In one embodiment, the technique is realized by selectively directing a pair of adjacent frequency channels corresponding to a respective pair of adjacent wavelength channels based upon a routing algorithm. The frequencies of the selectively directed pair of adjacent frequency channels are then interchanged. The interchanged frequencies of the selectively directed pair of adjacent frequency channels are then selectively shifted based upon a binary representation of each interchanged frequency.

Abstract: A technique for optically converting wavelengths in a multi-wavelength system is disclosed. In one embodiment, wherein the multi-wavelength system has W wavelength channels, wherein W=2N, the technique is realized by selectively directing a received frequency channel corresponding to a respective wavelength channel based upon a predetermined frequency mapping. Then, the frequency of the selectively directed frequency channel is shifted at least once by an amount defined by ±2i?f, wherein ?f is the frequency spacing between adjacent frequency channels, and i=0, 1, . . . N?1.

Abstract: A method of encoding a plurality of pre-defined codes into a search key and a method of using the search key to locate a longest matching pre-defined code to a given code is disclosed. Encoding the pre-defined codes into a search key involves producing a prefix node bit array (PNBA) having a plurality of bit positions corresponding to possible bit combinations of a bit string having a length equal to or less than the longest predefined code in said plurality of said pre-defined codes such that said bit positions are arranged by the lengths of said possible bit combinations and by numeric value of said possible bit combinations and to setting bits active in bit positions which correspond to bit combinations identified by said pre-defined codes.

Abstract: A method and apparatus are provided for adjusting the volume of data communicated between a transmitter and a receiver on a network, in a time interval. The method involves producing a desired volume value in response to a volume value specified by the receiver and a difference between a target departure volume and an estimate of arrival volume of data at a queue through which data passes from the transmitter to the receiver, and communicating the desired volume value to the transmitter in response to an acknowledgement signal produced by the receiver.

Abstract: A technique for managing a queue so as to distribute losses among different service classes is disclosed. In one embodiment, the technique is realized by classifying an incoming packet into one of a plurality of classes. Each class has an associated weighting factor. The system continuously monitors a queue size and determines an overall packet drop probability based on the actual queue size and a target queue size and calculates a target class drop probability based on the overall packet drop probability and the weighting factor. Finally, the system makes a comparison based on the target class drop probability and a selected value and decides whether to drop the incoming packet based on a result of the comparison. If losses are unavoidable in the system, the technique ensures that the losses will be distributed among the different service classes in inverse proportion to the service price of each class.