Abstract: Data rate control systems, methods, and computer program products in which an error counter is maintained that contains an error count. The error counter is periodically sampled to determine a sampling interval error count corresponding to a change in the error count since a previous read of the error counter. The sampling interval error count is provided to a first filter that is characterized by a slow time-constant and a second filter that is characterized by a fast time-constant. The first filter generates a slow-filtered sampling interval error count while the second filter generates a fast-filtered sampling interval error count, which are used as a basis for generating a data rate slowdown request signal. More specifically, the data rate slowdown request signal is generated if either the slow-filtered sampling interval error count or the fast-filtered sampling interval error count exceeds a threshold respectively associated therewith.

Abstract: Methods, systems and computer program products are provided for monitoring performance of a modem which obtain diagnostic data directly from memory associated with the modem's digital signal processor (DSP). A secondary path to the DSP memory is utilized for the monitoring operations so that real time data can be obtained during connection startup procedures and during an active connection. First-in first-out (FIFO) buffers are incorporated in the DSP memory to track state transitions of one or more of the state machines within the modem and various performance data measurements may be obtained directly from the DSP memory responsive to different state transition events. The real time collected data may be stored in a file and provided to a remote location for use in diagnosing customer problems with specific customer line connections. Accordingly, real time monitoring of digital and analog line conditions and modem performance may be utilized to diagnose problems with modems and line connections.

Abstract: Glitch filters, methods, and computer program products that utilize the generally monotonically increasing characteristics of the expected levels of code points to detect and remove noise spikes by replacing values in the code point sequence with new values based on the code points around a suspect value are provided. Measured values associated with two code points in the sequence of code points which are immediately higher in the sequence of code points than a code point of interest are evaluated so as to select a larger value of the two code points in the sequence as a first reference value. The first reference value is compared with a measured value associated with a code point in the sequence of code points immediately lower than the code point of interest to determine if the first reference value is smaller than the measured value associated with the code point in the sequence of code points immediately lower than the code point of interest.

Abstract: A system and method of protocol and frame classification in a system for data processing (e.g., switching or routing data packets or frames). The present invention includes analyzing a portion of the packet or frame according to predetermined tests, then storing key characteristics of the packet for use in subsequent processing of the frame. The key characteristics for the frame (or input information unit, such as the type of layer 3 protocol used in the frame, the layer 2 encapsulation technique, the starting instruction address and flags indicating whether the frame uses a virtual local area network, preferably using hardware to quickly and in a uniform time period. The stored key characteristics of the packet are then used by the network processing complexes in its further processing of the frame. The processor is preconditioned with a starting instruction address and the location of the beginning of the layer 3 header as well as flags for the type of frame.

Abstract: Digital impairments in a set of Pulse Code Modulation (PCM) signal levels that are received at a client modem from a server modem are identified by compressing the set of PCM signal levels into a signature. Digital impairments are determined based on the signature. In a preferred embodiment, the PCM signal levels are compressed into a signature by identifying clusters and/or skips in the set of PCM signal levels. In particular, when transmitting PCM signal levels from a server modem to a client modem over a connection that is subject to digital impairments such as Robbed Bit Signaling (RBS) and/or PAD digital impairments and quantization, some adjacent PCM signal levels may become identical or very close to one another. Moreover, other adjacent signal levels may have a difference that is at least approximately twice the difference of other levels. The former phenomenon is referred to as a “cluster” and the latter phenomenon is referred to as a “skip”.

Abstract: A method and system for encoding a set of range labels for each parameter field in a packet classification key in such a way as to require preferably only a single entry per rule in a final processing stage of a packet classifier. Multiple rules are sorted accorded to their respective significance. A range, based on a parameter in the packet header, is previously determined. Multiple rules are evaluated according to an overlapping of rules according to different ranges. Upon a determination that two or more rules overlap, each overlapping rule is expanded into multiple unique segments that identify unique range intersections. Each cluster of overlapping ranges is then offset so that at least one bit in a range for the rule remains unchanged. The range segments are then converted from binary to Gray code, which results in the ability to determine a CAM entry to use for each range.

Abstract: A packet network redistributes excess bandwidth for voice and data sessions applying a Quality of Service (QoS) algorithm. The network includes interacting client stations using H.323 protocol managing bit rate according to an algorithm as voice and data sessions are added or removed from the network. The client stations include codecs coupled to the network. The codecs provide voice sessions at a minimum bandwidth using a voice codec bit rate and preferred bandwidth using another voice codec bit rate. A first algorithm applies the QoS algorithm allocating bandwidth between interacting client stations after the addition of a new voice or data session when there is insufficient bandwidth for the new session to receive preferred bandwidth. A second algorithm is applied when a voice or data session is removed from the interacting client stations. If any session is allocated minimum bandwidth the QoS increases a voice session at minimum bandwidth to preferred bandwidth if excess bandwidth is available.

Abstract: An apparatus for performing complex pattern matching in a data stream within a computer network is disclosed. The apparatus includes a serial array register and a content-addressable memory (CAM). The CAM includes multiple CAM entries, and each of the CAM entries includes a k-byte pattern concatenated with an n-byte mask. The positions of the k-byte pattern and n-byte mask in each of the CAM entries offset from those in other CAM entries by one byte. Preferably, the k-byte pattern is each of the CAM entries represents a known computer virus pattern. After the capture of a data pattern from a data stream by the serial array register, the CAM register performs a comparison operation between the captured data pattern and all the CAM entries. If there is a match between the captured data pattern and one of the CAM entries, the CAM signals that the data stream contains information that are potentially harmful to the computer network.

Abstract: Modems, methods, and computer program products provide a dual power mode capability in which a maximum power limit is determined for a received signal and, based on that determination, at least one modem operational parameter is adjusted and/or digital impairment learning (DIL) sequence is selected. Adjustments made to the operational parameters may allow a modem to operate in a high power mode to achieve a higher downstream data rate. The higher downstream data rate may be attributed to an improved SNR resulting from an increase in data transmission power. Moreover, the modem may also operate in a normal power mode where the operational parameters may be set to maximize the client modem receiver's dynamic range. By selecting the DIL sequence based on the power limit, a DIL signal containing symbols having power levels within the power limit may be selected.

Abstract: Methods, systems and computer program products for averaging measured levels from differing intervals and differing code points based on their proximity with other measured levels are provided. Such proximity averaging may be provided by methods, systems and computer program products for averaging measured levels of code point sequences from a plurality of frame intervals in the presence of robbed-bit signaling by comparing a first measured level of a first code point from a first of the plurality of frame intervals and a measured level of a second code point from the plurality of frame intervals so as to provide a first comparison result. The measured level of the second code point is incorporated into an average of the measured levels for the first code point from the plurality of frame intervals based on the first comparison result and a threshold value.

Abstract: A system and method of protocol and frame classification in a system for data processing (e.g., switching or routing data packets or frames). The present invention includes analyzing a portion of the packet or frame according to predetermined tests, then storing key characteristics of the packet for use in subsequent processing of the frame. The key characteristics for the frame (or input information unit, such as the type of layer 3 protocol used in the frame, the layer 2 encapsulation technique, the starting instruction address and flags indicating whether the frame uses a virtual local area network, preferably using hardware to quickly and in a uniform time period. The stored key characteristics of the packet are then used by the network processing complexes in its further processing of the frame. The processor is preconditioned with a starting instruction address and the location of the beginning of the layer 3 header as well as flags for the type of frame.

Abstract: Methods, systems and computer program products for configuring a modem communication session when conditions associated with echo noise on a digitally discontinuous channel are detected are provided. The condition is detected at the local modem by reference to the local modem's respective transmit and receive rates. A low transmit rate is an indication of a channel problem. Furthermore, where the transmit rate is also lower than the receive rate, the problem is likely at the remote modem end not just a uniformly noisy channel. This combination of conditions has been found to result, for example, from middle echo noise.

Abstract: Methods, modems and computer program products for detecting whether a remote modem is of a particular design type and for adjusting the communication configuration for a communication session based on a type of the remote modem. The modem type is recognized based on a knowledge that the modem design of certain manufacturers has a unique associated data pattern contained within the startup communication sequence which is not specified by the protocol but which can be demodulated and detected to thereby recognize that the remote modem is a particular manufacturer's design type. Based on knowledge of the characteristics of the remote modem design, various steps are taken which may improve performance of the communication connection in light of the particular modem design's characteristics. For example, a different Total Harmonic Distortion (THD) threshold may be used for falling back to V.34 communications when the remote modem design only supports up to 2 look ahead for spectrum shaping.

Abstract: Methods, systems and computer program products for averaging measured levels from differing frame intervals based on a digital impairment pattern associated with the frame intervals are provided. Measured levels from frame intervals with the same digital impairment pattern may be averaged together and the measured levels replaced with the average. By averaging frame intervals based on a digital impairment pattern, the present invention may reduce the impact of noise by increasing the signal to noise ratio of the levels utilized for constellation generation. The use of the digital impairment patterns for determining which frame intervals to average may reduce the likelihood that digital impairments will corrupt the average by, for example, collapsing measured levels from one code point onto another code point.

Abstract: A method and structure for performing a delayed counter increment is provided. The method and structure allows a counter decision to be modified based upon what the computer system hardware does with the data packet. Subsequent to the generation of a counter command, the processing of the data packet may change: for example, the data packet may be discarded instead of forwarded. Accordingly, the counter increment instruction is changed. A delayed counter increment will perform the actual counter update after the processing of the data packet is completed. In one embodiment of the invention, the counter update action is modified depending upon whether the data packet is forwarded or discarded, and a different counter is selected to be updated. This solves a problem that sometimes the forwarding code is unable to determine if some independent action may later discard a data packet.

Abstract: A system and method for retrieving information in a distributed table by partitioning a search key. A packet processor may generate a search key for a received packet of data. The packet processor may partition the search key into a plurality of segments where the length of each segment corresponds to a size of a particular layer of a table. The packet processor may read a particular entry in a particular layer, e.g., the first layer, of the table using a value of the segment, e.g., the first segment, associated with that layer. A determination may be made to determine if the particular entry read stores a pointer that points to the next level of the table. If so, then the packet processor may read a particular entry in the next level of the table using the value of the next segment of the plurality of segments.

Abstract: A method and structure for performing a delayed counter increment is provided. The method and structure allows a counter decision to be modified based upon what the computer system hardware does with the data packet. Subsequent to the generation of a counter command, the processing of the data packet may change: for example, the data packet may be discarded instead of forwarded. Accordingly, the counter increment instruction is changed. A delayed counter increment will perform the actual counter update after the processing of the data packet is completed. In one embodiment of the invention, the counter update action is modified depending upon whether the data packet is forwarded or discarded, and a different counter is selected to be updated. This solves a problem that sometimes the forwarding code is unable to determine if some independent action may later discard a data packet.

Abstract: A method, system and computer program product for eliminating memory corruption when performing multi-threaded tree operations. A network processor may receive a command to perform a tree operation on a tree on one or more of multiple threads. Upon performing the requested tree operation, the network processor may lock one or more resources during a portion of the execution of the requested tree operation using one or more semaphores. A semaphore may refer to a flag used to indicate whether to “lock” or make available the resource associated with the semaphore. Locking may refer to preventing the resource from being available to other threads. Hence, by locking one or more resources during a portion of the tree operation, memory corruption may be eliminated in a multiple thread system while preventing these resources from being used by other threads for a minimal amount of time.

Abstract: Receivers, methods, and computer program products can be used to demodulate a data signal transmitted from a digital source, which has a network sampling rate that is synchronized with a network clock. In an illustrative embodiment, a receiver includes a two-stage interpolator that receives digital samples of the data signal as an input and produces an interpolated digital sample stream to be filtered by an adaptive fractionally spaced decision feedback equalizer. The digital samples received in the interpolator are synchronized with a local clock; however, the interpolated sample stream is synchronized with the network clock. A slicer generates symbols for the samples output from the decision feedback equalizer by comparing the samples with a reference signaling alphabet. The receiver can be used in a V.90 client modem to demodulate pulse code modulated (PCM) data transmitted as pulse amplitude modulated (PAM) signals from a digital network.

Abstract: A method and system for storing and searching for prefixes for rules, such as filter rules, in a computer system is disclosed. The method and system include providing a ternary content addressable memory (TCAM). The filter rules use range(s) of values in at least one dimension and correspond to prefix(es). The range(s) are described by prefix(es). Some filter rules may intersect. The method and system include providing priorities for the filter rules. The priorities include at least one different priority for the filter rules that intersect. The method and system also include storing the prefixes in the TCAM in block(s) in an order based upon the priorities of the filter rules. In another aspect, the method and system include searching the TCAM for a longest prefix match for a key and searching an additional storage for an almost exact match for the key in parallel with the TCAM.