Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-03-08
2003-07-08
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S466000
Reexamination Certificate
active
06590897
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the field of communication systems, and more particularly to a system and method for communicating information between a host and a communications network using a universal serial bus and a modem.
BACKGROUND OF THE INVENTION
The advent of the universal serial bus (USB) has provided significant advancements in a host's ability to communicate with peripheral equipment in a timely and efficient manner. When used in conjunction with asynchronous transfer mode (ATM) technology, however, the universal serial bus presents unique challenges that, until now, have gone largely unaddressed. As used throughout this document, the terms “asynchronous transfer mode” and “ATM” refer to a fixed-length cell based communication technology. As used throughout this document, the terms “universal serial bus” and “USB” refer to a packet-based master-slave communications device operable to facilitate communications between a host and peripheral devices.
One issue involved in transmitting ATM cells over a universal serial bus is how to provide effective control of the transmission rate associated with each class of ATM cell, and the multiple transmission rates associated with various classes of service. Conventional approaches rely on a driver at the host to provide virtually all rate control functionality. This approach suffers from several problems. One problem with relying on the host to provide rate control is that it places an unnecessary, and often heavy burden on the host, rendering the host unable to attend to other processing tasks. Another problem with this approach is that hosts typically utilize operating systems that lack the capability to provide the necessary granularity in rate control. Still another problem with this approach is that even if the host's operating system could provide a high level of granularity in rate control, the accuracy gained in the rate control algorithm would be lost when the ATM cells are transmitted across the universal serial bus, which typically has a one millisecond frame rate.
A recent universal serial bus specification suggests that it may be possible to provide some level of rate control functionality at the modem. This specification, however, requires that prior to performing rate control functions, the modem be configured to perform rate control functions for a particular transmission rate. The specification requires that the modem be configured by sending a separate stream of control information to the modem. Using this approach, each time it is desired that the modem perform rate control using a different transmission rate, the modem must be reconfigured for the new transmission rate. This approach wastes memory and suffers from latency caused by having to continuously reconfigure the modem for different transmission rates.
Still another issue in transmitting ATM cells over a universal serial bus is how to format conventional ATM cells (which are typically 52 or 53 bytes) into universal serial bus transmission packets (which are typically 64-byte packets). One approach has been to simply insert one ATM cell into each USB packet, leaving the remainder of the USB packet empty. This approach wastes valuable bandwidth. Another approach has been to concatenate ATM signals from a common protocol data unit into a segment of USB packets. Although this approach may, at times, make more efficient use of the universal serial bus' bandwidth, it lacks efficiency when compared to the present invention.
Another issue in transmitting ATM cells over a universal serial bus is how to achieve effective flow control. The flow control functionality offered by the universal serial bus wastes bandwidth and is generally considered poor. Higher protocol levels, such as the transmission control protocol (TCP) level offer much better flow control. These higher level flow control mechanisms, however, give way to the USB flow control mechanism whenever the memory structure in the modem fills up.
Because conventional systems for transmitting ATM cells over a universal serial bus perform all rate control and scheduling at the host, memory and processing requirements at the host are significant. To offset costs associated with larger memories and processors used to perform rate control and scheduling at the host, conventional systems find it desirable to use the least amount of memory possible at the modem. These small modem memories, however, fill quickly and trigger the poor USB flow control mechanism, wasting valuable bandwidth.
In addition, conventional systems rarely pay much attention to flow control mechanisms of the universal serial bus, choosing instead to rely on the rate control and scheduling functions performed at the host to ensure efficient data transmission. Due to various transmission conditions, however, signal backlogs occur and flow control nevertheless becomes an issue, even where rate control and scheduling are effected at the host. Again, the universal serial bus flow control mechanism is triggered and bandwidth is wasted.
SUMMARY OF THE INVENTION
In accordance with the present invention, a system and method for communicating information from a host to a communications link using a universal serial bus are provided that substantially reduce or eliminate shortcomings associated with prior approaches.
In one aspect of the present invention, a system for communicating information between a host and a communications link using a universal serial bus, comprises a driver at the host operable to receive a data block comprising a plurality of ATM cell payloads, to format the data block into a first USB segment including rate control information associated with the plurality of ATM payloads, and to communicate the first USB segment to the universal serial bus. The system further comprises a modem operable to receive the first USB segment from the universal serial bus, to store the ATM cell payloads in a modem memory, and to schedule transmission of the ATM cell payloads at a particular transmission rate using the rate control information.
In another aspect of the present invention, a modem operable to facilitate communication between a host and a communications link comprises a memory operable to store a rate control algorithm. The modem further comprises a controller operable to receive from the universal serial bus a first USB segment comprising a first plurality of ATM cells and rate control information associated with the first plurality of ATM cells, to store the first plurality of ATM cells in the memory, and to perform the rate control algorithm on the first plurality of ATM cells using the rate control information received in the first USB segment. The modem further operable to transmit each of the plurality of ATM cells at a particular transmission rate according to the results of the rate control algorithm.
In yet another aspect of the present invention, a method of communicating information from a host to a communications link using a universal serial bus comprises receiving at a host, a data block comprising a plurality of ATM cell payloads, formatting the data block at the host into a USB segment including rate control information associated with the plurality of ATM payloads, and communicating the USB segment over the universal serial bus. The method further comprises receiving at a modem the USB segment from the universal serial bus, storing the ATM cell payloads in a modem memory, and scheduling transmission of the ATM cell payloads at a particular transmission rate using the rate control information.
In still another aspect of the invention, a method of communicating information between a host and a communications link using a universal serial bus comprises receiving from the universal serial bus a first plurality of ATM cells associated with a first transmission channel of the communications link, and receiving from the universal serial bus a second plurality of ATM cells associated with a second transmission channel of the communications link. The method further include
Fosmark Klaus S.
Lauffenburger Kenneth A.
Martin Kimberly I.
Perry, Jr. William A.
Baker & Botts L.L.P.
Cangialosi Salvatore
Efficient Networks, Inc.
LandOfFree
System and method for bridging universal serial bus and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method for bridging universal serial bus and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method for bridging universal serial bus and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3107575