Abstract: In a frame-switched network, a sender sends frames to a receiver over a possibly unreliable channel. Sent frames include frame identifiers that can be used for a limited automatic repeat request. Upon receipt of a frame, the receiver determines, from the frame identifier, if frames prior to the received frame were lost in transit. If the receiver determines that it missed a prior frame, the receiver sends the sender a negative acknowledgment (nack) for the missed prior frame or frames. Otherwise, if the receiver receives a frame correctly, it does not acknowledge the frame. The frame identifiers can be a set of sequential integers with frames transmitted in sequential frame order. In some embodiments, when a receiver receives a frame out of order, the receiver buffers the out of order frame in a receiver buffer for a receive buffer period until preceding frames are received or a receive buffer period expires.

Abstract: Methods and apparatus for data communication are disclosed. An example method includes encoding a first plurality of transmitting frames, where a header segment of each frame is encoded in accordance with a fixed set of header encoding parameters and a payload segment of each frame is encoded in accordance with a first set of a variable set of payload encoding parameters. The example method also includes transmitting the first plurality of transmitting frames to a receiving station and receiving a request from the receiving station to change the first set of payload encoding parameters to a second set of the variable set of payload encoding parameters.

Abstract: A modem and method for operating same. A receiver circuit of the modem is coupled to receive a continuous analog signal from a communication channel. This analog signal includes both packet and idle information. The receiver circuit monitors the analog signal to detect the presence of idle information. Upon detecting idle information, the receiver circuit enters a standby mode in which the processing requirements of the receiver circuit are reduced. A burst mode protocol is also provided, in which packets of digital information are modulated by a transmitter circuit the modem, thereby converting the packets of digital information into analog signal bursts of discrete duration. These analog signal bursts are transmitted from the transmitter circuit to a telephone line. However, the transmitter circuit does not generate any signals between the analog signal bursts. A receiver circuit monitors the telephone line to detect the analog signal bursts.

Abstract: Methods and apparatus for data communication are disclosed. An example method includes encoding a first plurality of transmitting frames, where a header segment of each frame is encoded in accordance with a fixed set of header encoding parameters and a payload segment of each frame is encoded in accordance with a first set of a variable set of payload encoding parameters. The example method also includes transmitting the first plurality of transmitting frames to a receiving station and receiving a request from the receiving station to change the first set of payload encoding parameters to a second set of the variable set of payload encoding parameters.

Abstract: A receiver circuit of the modem is coupled to receive a continuous analog signal from a communication channel. This analog signal includes both packet and idle information. A burst mode protocol is also provided, in which packets of digital information are modulated by a transmitter circuit of the modem, thereby converting the packets of digital information into analog signal bursts of discrete duration. These analog signal bursts are transmitted from the transmitter circuit to a telephone line. A receiver circuit monitors the telephone line to detect the analog signal bursts. Upon detecting the presence of the analog signal bursts on the telephone line, the receiver circuit demodulates the analog signal bursts using full processing capabilities of the receiver circuit. However, upon detecting the absence of the analog signal bursts on the telephone line, the demodulating function of the receiver circuit is disabled.

Abstract: A method of sharing information among a plurality of stations on a communications network, each of the stations being capable of transmitting and receiving frames over the communications network. A group of agreed-upon flags is established, periodic timing is provided in each station that expires after an interval, and a common frame format is defined providing the capability of specifying a current transmit flag set, an old transmit flag set, and a current receive flag set. Each station maintains: a current transmit state set a recent and previous timer expiration set and a current and previous transmit received set. A control frame is generated and transmitted by a transmitting station to all other stations on the communications network each time a flag in a logical union of current transmit flag sets is set and upon the expiration of the timer in the transmitting station.

Abstract: A method for providing dynamic adjustment of frame encoding parameters to improve transmission performance for a transmitting frame being transmitted from a transmitting station to a receiving station over a transmission medium on a frame-based communications network, the transmitting frame having a header segment and a payload segment, the header segment being transmitted using a fixed set of encoding parameters, the payload segment being transmitted using a variable set of payload encoding parameters.

Abstract: A “high availability” system comprises multiple switches under the control of one more control processors (“CPs”). Each CP performs a staged startup process when failing-over from another CP or otherwise booting up. The staged startup process involves multiple stages of processing of various executable components of the image. Some stages may depend on the prior execution of other stages. The preferred staged startup process includes the use of a staging table which permits the standby image's FSS facility to efficiently schedule the various stages of the fail-over process taking into account the inter-stage dependencies.

Abstract: A method and signal therfor embodied in a carrier wave for sending information from transmit stations to receive stations over a transmission medium of a frame-based communications network. The information is sent in transmit frames having a frame format comprising a fixed rate header, followed by a variable rate payload, followed by a fixed rate trailer. The fixed rate header includes a preamble. The preamble has a repetition of four symbol sequences for facilitating power estimation, gain control, baud frequency offset estimation, equalizer training, carrier sensing and collision detection. The preamble also includes a frame control field.

Abstract: A method of providing synchronous transport of packets between asynchronous network nodes. An asynchronous network node capable of transmitting and receiving packetson the asynchronous network is designated as a master node. Each non-master asynchronous network node which desires to synchronously transport packets across the asynchronous network is designated as a slave node. Best arrival times for packets transmitted from slave nodes to the master node are communicated from the master node to the slave nodes. Bestpacket assembly times for packets to be transmitted by the particular slave node to the master node in the future for the packets to be received by the master node at future master clock referenced best arrival times are determined. Packets for transmission at slave nodes are prepared and transmitted according to determined future bestpacket assembly time information.

Abstract: A method of controlling data sampling clocking of asynchronous network nodes, each asynchronous network node having a local clock and transmitting and receiving packets to and from an asynchronous network according to an asynchronous network media access protocol. An asynchronous network node capable of transmitting and receiving packets on the asynchronous network is designated as a master node. Each non-master asynchronous network node which desires to synchronously transport packets across the asynchronous network is designated as a slave node. A master node clock of the master node is synchronized with a slave node clock of each slave node. Each slave node clock is continuously corrected compared with the master node clock to smooth slave clock error to an average of zero compared with the master clock as a reference using timestamp information from the master node.

Abstract: A method of enhancing network transmission between stations on a priority-enabled frame-based communications network, the communications network having multiple transmit priorities and transmitting frames such that a network access time to transmit a frame of a lower transmit priority is longer than a network access time to transmit a frame of a higher transmit priority, the number of transmit priorities being fixed and all stations being capable of transmitting frames at any transmit priority. The method applies to each station. An initial transmit priority is established for each frame to be transmitted. A set of initial transmit priorities assigned to frames transmitted on the communications network is maintained.

Abstract: A method for selecting an operating mode for a frame-based communications network consisting of a plurality of stations attached to a transmission medium. The plurality of stations include both a first type station and a second type station. The first type station is capable of transmitting and receiving first protocol frames in accordance with a first protocol. The second type station is capable of transmitting and receiving both first protocol frames and second protocol frames in accordance with a second protocol. The first protocol and the second protocol each use different signals on the transmission medium. The first type station is not capable of reliably detecting second protocol frames. The first protocol has a first protocol frame format containing at least two reserved bits in a first protocol frame header which are ignored in received frames by first type stations and always sent with a same fixed value by first type stations.

Abstract: A method for distributing sets of collision resolution parameters to be used for resolution of network access contention events among nodes of a non-centralized media access control shared medium network. A set of collision resolution parameters is provided which includes a sequence of fixed numbers for resolving a single network access contention event. A single collision signal slot master node is identified when one or more candidate collision signal slot master nodes exist. Collision signal slot request messages are sent from client nodes addressed to all network nodes. Collision signal slot assignment messages are sent from the master node to the client nodes. A collision resolution parameter set to be employed by that given client node is obtained at a given client node from within a received collision signal slot assignment message. Collision signal slot acknowledgment messages are sent from client nodes addressed to all network nodes.

Abstract: A “high availability” system comprises multiple switches under the control of one more control processors (“CPs”). Each CP performs a staged startup process when failing-over from another CP or otherwise booting up. The staged startup process involves multiple stages of processing of various executable components of the image. Some stages may depend on the prior execution of other stages. The preferred staged startup process includes the use of a staging table which permits the standby image's FSS facility to efficiently schedule the various stages of the fail-over process taking into account the inter-stage dependencies.

Abstract: A modem and method for operating same. A receiver circuit of the modem is coupled to receive a continuous analog signal from a communication channel. This analog signal includes both packet and idle information. The receiver circuit monitors the analog signal to detect the presence of idle information. Upon detecting idle information, the receiver circuit enters a standby mode in which the processing requirements of the receiver circuit are reduced. A burst mode protocol is also provided, in which packets of digital information are modulated by a transmitter circuit 6f the modem, thereby converting the packets of digital information into analog signal bursts of discrete duration. These analog signal bursts are transmitted from the transmitter circuit to a telephone line. However, the transmitter circuit does not generate any signals between the analog signal bursts. A receiver circuit monitors the telephone line to detect the analog signal bursts.

Abstract: A method of providing synchronous transport of packets between asynchronous network nodes, each asynchronous network node having a local clock and transmitting and receiving packets to and from the asynchronous network according to an asynchronous network media access protocol. An asynchronous network node capable of transmitting and receiving packets on the asynchronous network is designated as a master node. Each non-master asynchronous network node which desires to synchronously transport packets across the asynchronous network as a slave node and each slave node is designated as a slave node. A master node clock of the master node is synchronized with a slave node clock of each slave node. A best arrival time for the reception by the master node of each particular packet transmitted by each particular slave node is determined at the master node. Best arrival times for packets transmitted from slave nodes to the master node are communicated from the master node to the slave nodes.

Abstract: A modem and method for operating same. A receiver circuit of the modem is coupled to receive a continuous analog signal from a communication channel. This analog signal includes both packet and idle information. The receiver circuit monitors the analog signal to detect the presence of idle information. Upon detecting idle information, the receiver circuit enters a standby mode in which the processing requirements of the receiver circuit are reduced. A burst mode protocol is also provided, in which packets of digital information are modulated by a transmitter circuit of the modem, thereby converting the packets of digital information into analog signal bursts of discrete duration. These analog signal bursts are transmitted from the transmitter circuit to a telephone line. However, the transmitter circuit does not generate any signals between the analog signal bursts. A receiver circuit monitors the telephone line to detect the analog signal bursts.

Abstract: A method of sharing information among a plurality of stations on a communications network, each of the plurality of stations being capable of transmitting and receiving frames over the communications network between any one station and all other stations. A group of agreed-upon flags is established, each flag of which may be set or not set by a station of the communications network at any given time. Periodic timing is provided in each station that expires after an interval, the interval being common among all the stations and being at least long enough to allow every station on the communications network to transmit a plurality of frames. A common frame format is defined providing the capability of specifying a current transmit flag set, an old transmit flag set, and a current receive flag set.

Abstract: A method for providing dynamic adjustment of frame encoding parameters to improve transmission performance for a transmitting frame being transmitted from a transmitting station to a receiving station over a transmission medium on a frame-based communications network, the transmitting frame having a header segment and a payload segment, the header segment being transmitted using a fixed set of encoding parameters, the payload segment being transmitted using a variable set of payload encoding parameters. The transmitting station sends the transmitting frame using one set of the variable set of payload encoding parameters at a time.