Multiplex communications – Channel assignment techniques – Adaptive selection of channel assignment technique
Reexamination Certificate
1998-08-17
2002-10-08
Kizou, Hassan (Department: 2662)
Multiplex communications
Channel assignment techniques
Adaptive selection of channel assignment technique
C370S474000, C370S486000
Reexamination Certificate
active
06463071
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of data communication. More particularly, the present invention relates to a method and system to communicate prioritized data traffic over a communications network via a data communication frame.
BACKGROUND OF THE INVENTION
Communication networks are an essential tool for generating prosperity in a modem society. Communication networks have become virtually indispensable in building a thriving economy because they allow users to readily gain access to and exchange information of all types (e.g., sound, text, numerical data, video, graphics, multimedia, etc.). Information transmitted over communication networks is utilized in the performance of a number of functions, including the conveyance and analysis of ideas and trends in most areas of business, science, education and entertainment. Efficient communication of information has facilitated increased productivity and reduced costs in numerous activities. The speed at which data is communicated has a significant impact on the efficiency of a communication network.
One way to improve the performance of a communication network is to increase its bandwidth, the speed at which data can be transmitted over a communication network. Larger bandwidth communication networks can transmit more data in a shorter period of time. However, upgrading communication networks to provide increased bandwidth capacity is usually an expensive, time-consuming, and disruptive process. It typically entails discarding older equipment and replacing it with newer, faster, and more costly models. Replacing major infrastructure communication networks such as telephone or coaxial cable networks with new facilities such as overhead or underground cabling is very expensive. Furthermore, advanced networks are typically harder to maintain, service, and administer.
Upgrades are not undertaken lightly and in the meantime, users generally suffer through frustratingly slow response times and congestion problems in most older communication networks. Further complicating matters is the fact that communication networks often experience high activity and traffic at certain peak operating times. For example, a communication network's resources are usually pushed to capacity when numerous multiple devices attempt to log onto and transmit data over the network simultaneously or when an application is transmitting a very large file in a burst. When the amount of data to be transmitted exceeds a network's bandwidth, the network becomes overloaded and the time or “latency” for transmitting a packet of data increases dramatically. It is very difficult to predict and prevent the occurrence of these traffic peaks.
In an effort to minimize the impact of surges in traffic and to generally manage the overall traffic on a network, it is common for a network to include storage buffers to temporarily store the data before a transmission. If the network is currently to busy to handle the data, it is queued up in buffers. Enqueued data must wait in turn until the opportunity arises for it to be sent over the network. The basic operating principle of a queue is the items first in are those first out (FIFO). Although the queue buffers are beneficial, they still do not solve all potential communication transmission problems in a network.
In many instances the queue buffers actually operate in a manner that detracts from optimized data flow, especially when handling high priority data traffic. Usually, some of the data to be transmitted over a communication network is more important or has a higher priority than other data. For example, key network administration data, such as communication network control information, can be critical to the operation of the communication network. In addition, other components coupled to a communications network often have operational constraints and it is critical to the performance of these devices that certain data be transmitted within latency tolerances, data transfer bandwidth requirements, etc. Data comprising important information should be transmitted expeditiously in order to keep the communication network and components or devices coupled to it operating properly.
Another detrimental aspect of buffers is their capacity limitations. Including the queue buffers in a communications network increases the costs of manufacturing network devices. Hence, designers typically try to limit the number of queue buffers that are installed in a communications network. Restricting buffer capacity gives rise to increases in instances when the buffers are full. As long as the buffers are full, successive information cannot be queued for eventual transmission over the network. Data that is not entered in a buffer queue is dropped or the device it originated from has to keep attempting to get it entered into a queue buffer. During instances when the queue buffers are full with lower priority data, such as information related to non-critical activities, e-mail messages, etc., higher priority data can not be transmitted. Therefore, in limiting the number of queue buffers, designers attempt to balance the pros and cons of adding buffers and calculate the optimum amount of queue buffers from a cost benefit point of view.
Communication problems resulting from a limited number of buffers and the FIFO nature of queues are magnified in communications networks comprising limited communication paths. Usually such communication networks are administered in a manner that permits only one device or entity to communicate on a path at a time and devices typically have to compete for communication network resources. Delays incurred while a device waits to obtain access to network resources increases the detrimental affects of queuing high priority traffic behind lower priority traffic in a buffer queue. In addition to waiting for lower priority data to clear out of the queue, once high priority data reaches the top of the queue it must wait while network resources become available.
What is required is a system and method that permits higher priority data to be transmitted ahead of lower priority data included in fixed length data communication frames. The system or method should enable the higher priority information to be transmitted in a manner that minimizes impacts to communication flow and conserves communication network resources. For example, it should be applicable to existing communication networks in a manner that preserves the usefulness of current communication protocols while minimizing adverse affects on network infrastructure.
SUMMARY OF THE INVENTION
The present invention is a system and method that permits higher priority data to be transmitted before a lower priority data included in fixed length data communication frames. The present system and method enables the higher priority information to be transmitted in a manner that minimizes impacts to communication flow and conserves communication network resources. It is capable of being incorporated in existing communication networks in a manner that preserves the usefulness of current communication protocols while minimizing adverse affects on network infrastructure.
In one embodiment, the present invention is a communications network system and method operating in a data cable system that transmits a data over cable media access control (MAC) frame with an Ethernet/[ISO8802-3] type packet protocol data unit payload. Time frames for transmission of data over the communication network are allocated to cable modems and time frames originally allocated to a cable modem for transmission of lower priority data can be utilized to transfer high priority data while aborting the transmission of lower priority data. A high level data link control (HDLC) section is coupled immediately before a cyclical redundancy check (CRC) to indicate that packet protocol data units (PDU) that are encapsulated by HDLC flags include high priority data that is not to be discarded.
REFERENCES:
patent: 5412660 (1995-05-01), Chen et al.
patent: 5471474 (1995-
Araujo Kenneth
Wang Peter Si-Sheng
3Com Corporation
Kizou Hassan
PezzLo John
Wagner , Murabito & Hao LLP
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