3com Corporation

3 Com Corporation

Buscom Systems Inc.

Donald M Bellenger

Steven Paul Russell

James E Dunn

Timothy F Murphy

Richard Guy Carrington Williams

James H Gibbons

David O Sovey

A statistical switching method is described. The method involving computing tags from a packet to identify the flow a packet belongs to, looking up the tag in a table to provide switching information and using the switching information to switch the packet without analyzing the whole packet. If there is no entry for the flow based on the tag generated from the packet, the packet is sent to a router for further analysis. When the analysis is complete the switching information is provided to the table. If a packet which computes the same tag arrives at the switch before the router has finished analyzing the first packet of the flow, the new packet is dropped. The statistical switch has a non-zero probability of misdirecting a packet due to the possibility that two packets belonging to different flows may produce the same tag. The statistical switch provides high-speed switching and routing capabilities at low cost.

Method for statistical switching

Method and apparatus for hierarchical management of subscriber link traffic on digital networks

The current invention provides methods for relieving congestion associated with interfacing multiple types of subscriber link traffic, i.e. voice, voice-band data, and broad-band data, with a network such as the public switched telephone network (PSTN). In an embodiment of the invention waste of modem resources is diminished by reducing the magnitude of the transmission parameters between a data terminal and modem resources during intervals of reduced data flow. This frees scarce modem resources for other sessions. In another embodiment of the invention the time required to initiate session setup is reduced. This reduces the time devoted by modem facilities to call setup at the start of session, or after an idle period.

Methods for interfacing a subscriber link to digital networks

An atomic type switch mesh is combined with standard local area network links, such as high speed Ethernet, and a bridge-like protocol to provide a high performance scalable network switch. The network switch comprises a plurality of switch nodes, a first set of communication links which are coupled between switch nodes internal to the network switch, and a second set of communication links which comprise network links from switch nodes on the border of the network switch to systems external to the network switch. The respective switch nodes include a set of ports (having more than two members) which are connected to respective communication links in either the first or second set of communication links. Each port in the set comprises a medium access control (MAC) logic unit for a connectionless network protocol, preferably high speed Ethernet. The switch nodes also include a route table memory which has a set of accessible memory locations that store switch route data specifying routes through the plurality of switch nodes within the boundaries of the network switch. Flow detect logic is coupled with the set of ports on the switch node, which monitors frames received by the set of ports and generates an identifying tag for use in accessing the route table memory. Finally, the switch node includes node route logic which is coupled with the flow detect logic, the route table memory and the set of ports. The node route logic monitors frames received by the set of ports to route a received frame for transmission out a port in the set of ports.

Atomic network switch with integrated circuit switch nodes

The present invention provides a method and an apparatus for connecting a plurality of subscriber loops to a pool of modem resources in a way that limits the amount of modem resources that are required. The present invention uses statistical multiplexing, such as is used in Ethernet (instead of a fixed time slot TDM as is used in a telephone system) to connect the plurality of subscriber loops to the modem resources. In order to implement the statistical multiplexing, communications between a plurality of remote modems coupled to a plurality of subscriber loops and modem resources within a central site modem must be flow controlled at the carrier layer, as is done in an Ethernet.

Apparatus for statistical multiplexing and flow control of digital subscriber loop modems

The present invention allows telephone subscriber loops carrying data traffic between computer systems to be switched to an alternative connection through a data network, thereby unloading data traffic from the telephone network. The invention operates by means of a break switch, which selectively switches a plurality of subscriber loops between a central office switching system and a data network. The break switch is coupled to a concentrator which takes a plurality of inputs from the break switch and connects them to a smaller number of modems in a modem pool. The concentrator allows a subscriber line to connect to different types of modems within the modem pool, depending upon requirements of a particular subscriber line user. The modem pool connects through a network interface to a packet-switched network, such as the Internet. A number of different methods can be used to transmit a command to switch a subscriber loop from the central office switching system to the packet-switched network. A loop current detector, which is coupled between the plurality of subscriber loops and the break switch, can monitor on/off hook status of the subscriber loop in order to determine whether to switch the connection to the data network. Alternatively, the command to perform the switching can originate from a remote host which transmits the command through the data network to the break switch.

Subscriber loop bypass modem

Method for bypassing telephone network

The present invention allows a modem to operate in both the voice band, from 300 to 3400 Hz, and also in the ADSL band, which extends above 3400 Hz. Unlike conventional ADSL modems, the present invention avoids the computationally-intensive operations required to extract all the available band of a telephone subscriber loop. Consequently, the present invention can be implemented with low-cost modifications to existing voice band modems. The present invention thereby offers higher data transfer rates at a fraction of the cost of more complicated ADSL modems. The present invention also provides bypassing functions, which allow communications through a modem located at the telephone central office side of a subscriber loop to be switched through a packet-switched network, which is capable of accommodating high data transfer rates, instead of a central office switching system, which generally imposes unnecessary limitations on data transfer rates.

Bypassing telephone network with dual band modem

Dual band bypass modem

Dual band modem

Dual band modem for high bandwidth communications

A flow based network switch function is based on a route cache and flow detect logic which generates hash codes for use in accessing the route cache. Flow detect logic is implemented with read-write register functions. A network switch which comprises a port for access to a communication medium to receive incoming frames. A route table memory has a set of accessible locations for storing routing information. The set of accessible locations is addressable in response to N bits, and locations in the set store a tag comprising M bits for identifying a network flow. Routing information is also stored in each of the accessible locations for the identified network flow. Flow detect logic is coupled with a port and monitors frames received by the port generate and N bit address, and an identifying tag comprising M bits for use in accessing the route table memory in response to an incoming frame on the port. Match logic is coupled with the route table memory and the flow detect logic, which accesses a particular location in the set of accessible locations in the route table memory in response to the N bit address, compares the identifying tag with the tag stored in the particular location to determine whether the incoming frame matches the network flow identified by the stored tag, and supplies the routing information for level 3 or higher stored in the particular location if a match occurs. If a match does not occur, a route table miss is indicated, and the frame is forwarded to multi-protocol routing algorithms for the purpose of generating the routing information for the incoming frame.

Stochastic circuit identification in a multi-protocol network switch

An apparatus for emulating a floppy disk drive using flash EPROMs. The apparatus transfers data between a floppy disk controller and a flash EPROM memory module, wherein the floppy disk controller operates under a first protocol and transmits requests to write data to a floppy disk in response to address marks. The flash EPROM operates under a second protocol. The invention includes control means compensating for the difference in the two protocols. In addition, the control means provides for the situation when power is terminated during the write process. Furthermore, the invention includes a means for organizing and reorganizing data in the flash EPROM to make most effective and efficient use of the flash EPROM memory module.

Apparatus for using flash memory as a floppy disk emulator in a computer

A single-tone receiver for a device which only needs simple data which can be encoded in the seven or eight single tones which can be generated by an ordinary pushbutton telephone is provided. A telephone line interface circuit receives a signal from the telephone line. The input signal is not filtered to separate the high-frequency tones from the low-frequency tones prior to their detection. A zero crossing detector coupled to the telephone line interface detects zero crossings of a received single-tone input signal. A microprocessor coupled to the zero crossing detector counts the number of zero crossings in a period and compares the count to counts corresponding to each of the seven single-tone frequencies.

Growing community of inventors

Los Altos Hills, CA, United States of America

Donald M Bellenger