Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-01-21
2001-07-17
Marcelo, Melvin (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C714S748000
Reexamination Certificate
active
06263001
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to protocols (i.e., sets of rules) for the communication of digital data between a sender and receiver (e.g., the sender and receiver are computer systems located at different physical locations).
BACKGROUND OF THE INVENTION
The usual form of digital data communication involves sending such digital data over a packet-based network. A packet is a group of bits representing a portion of the digital data and each packet is treated individually by the network. As digital data messages can be quite long, usually packets are grouped together by the sender and interpreted as a group by the receiver. In this way, the packet based network can still treat the packets individually, as it is used to doing, but the sender and receiver treat them as a group.
Protocols have been developed for such packet-based communications, such protocols being sets of rules by which the sender and receiver agree to abide by so that the packet data can be reliably understood once received at the receiver. One such protocol is known as UDP/IP (User Datagram Protocol/Internet Protocol). In this protocol, each time a sender sends a data packet the receiver sends an acknowledgement confirming to the sender that the receiver has received the data packet. Once the sender receives this acknowledgement, it can safely assume that the receiver has received the packet and the sender can thus delete this packet from its system. If the sender does not receive this acknowledgement, it assumes that the receiver has not received the packet and thus the sender sends the packet again to the receiver.
These protocols have been advantageously applied in the context of a client/server computing network, where a client computer system requests a server computer system to perform part of the client computer system's work. The client sends a request to the server asking the server to do some work. The server does the work and then sends a reply to the client. The client then uses this reply in its own local work.
In such client/server systems, there are many acknowledgements flowing back and forth between client and server as sometimes the client is the sender (when it sends a request for work) and sometimes the server is the sender (when it sends a reply back to the client). Acknowledgements are often sent after each data packet is received by the current receiver. Each of these received acknowledgements must be processed by the sender, which can present a drain on the processing resources of the sender computing system. Further, when certain communications networks are used, such as mobile networks, transmission time can be very expensive, so it is highly advantageous to flow as few packets as possible over the network. Thus, the many acknowledgements required in such systems has proven to be very expensive.
SUMMARY OF THE INVENTION
According to a first aspect, the invention provides a server computing system used in a client/server network, said computing system using a packet-based data transmission protocol in communicating data over said network, wherein, according to said protocol: a client computing system sends a request consisting of a plurality of packets to a server computing system; the server computing system processes the request and generates a reply, said reply consisting of a plurality of packets; and the server computing system sends the reply back to the client computing system; wherein said server computing system is characterized in that said server computing system comprises a means for setting a bit in a packet of said reply, said bit indicating that the client computing system need not send an acknowledgement back to the server computing system acknowledging that the client computing system has received said packet of said reply.
Preferably, the server computing system has a means for storing said packet of said reply containing said bit, and a means for retrieving said packet of said reply from storage upon receiving an indication from said client computing system that said packet of said reply has not been received by said client computing system.
According to a second aspect, the invention provides a client computing system used in a client/server network, said computing system using a packet-based data transmission protocol in communicating data over said network, wherein, according to said protocol: a client computing system sends a request consisting of a plurality of packets to a server computing system; the server computing system processes the request and generates a reply, said reply consisting of a plurality of packets; and the server computing system sends the reply back to the client computing system; wherein said client computing system is characterized in that said client computing system comprises a means for determining whether a bit has been set in a packet of said reply, said bit indicating that the client computing system need not send an acknowledgement back to the server computing system acknowledging that the client computing system has received said packet of said reply.
Preferably, the client computing system has a means for providing an indication to said server computing system that said packet of said reply has not been received.
Preferably, in the computing systems of the first two aspects of the invention said protocol is the UDP/IP protocol.
According to third and fourth aspects, the invention provides computer program products stored on computer readable storage media, for running on a server computing system or a client computing system of the first two aspects of the invention.
According to a fifth aspect, the invention provides a method of communicating packet based digital data over a communications network between a sender and a receiver, said method comprising steps of: sending a request, said request comprising a plurality of packets, to a receiver; receiving an acknowledgement from said receiver for each packet of said request; receiving a reply from said receiver, said reply comprising a plurality of packets, at least one of said packets including an indication that said packet need not be acknowledged upon receipt; acknowledging only the packets of said reply that do not contain said indication.
According to a sixth aspect, the invention provides a method of communicating packet based digital data over a communications network between a sender and a receiver, said method comprising steps of: receiving a request, said request comprising a plurality of packets, from the sender; sending an acknowledgement for each packet of said request; and sending a reply to said sender, said reply comprising a plurality of packets, at least one of said packets including an indication that said packet need not be acknowledged upon receipt.
Accordingly, the number of acknowledgement flows is greatly reduced as there is no need for the client to send an acknowledgement upon receipt of certain response packets from the server. This is especially advantageous when the packet based network is a mobile network, where the cost of transmitting a packet can be quite high.
Further, the server is saved from having to process these extra acknowledgements, and thus the processing resources of the server are conserved.
Still further, since the server stores the certain response packets in its internal memory, there is no need for the server to redo the work it has already done to generate the response if the client indicates that it has not received the response packets. The server need only retrieve these response packets from its internal memory.
REFERENCES:
patent: 5745685 (1998-04-01), Kirchner et al.
patent: 0 324 886 (1989-07-01), None
Duffield Edward H.
International Business Machines - Corporation
Marcelo Melvin
LandOfFree
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