Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1999-08-30
2002-09-17
Baker, Stephen M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C709S227000
Reexamination Certificate
active
06453438
ABSTRACT:
TECHNICAL FIELD
This invention generally relates to data transmission and to sending packets over a computer network. More particularly, it relates to a system and method for managing a session during which data is sent to receivers, wherein retransmission of the data to the receivers can be automatically rescheduled if the receiver did not receive some or all of the data.
BACKGROUND INFORMATION
Computer networks, such as wide area networks (WANs) using the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite, can provide unicast, multicast, and broadcast services to allow communication between network participants such as a sender node and one or more receiver nodes. IP supports the sending of data to broadcast addresses, which are delivered to all hosts on the network or subnetwork at the expense of creating traffic over the total network. IP also supports multicast technology to communicate over a computer network. The term “broadcast” refers to a sender node sending information to all of the receiver nodes connected to the network. The term “multicast” refers to a sender node sending information to a subset of all of the receiver nodes connected to the network.
Some information providers provide information electronically by broadcasting or multicasting the information from a sender node at a central location to one or more receiver nodes at remote customer locations via a computer network to which the sender and the receivers are coupled. Computer networks and systems use several different protocols to accomplish reliable data distribution.
TCP/IP, one common protocol suite, presently is used with the Internet. The TCP part provides transport protocol functions to ensure that the total amount of bytes sent is received correctly at the other end. The IP part provides a routing mechanism. In addition, because TCP/IP is a routable protocol, the messages transmitted in accordance with TCP/IP contain the address of a destination network as well as a destination station. Thus, TCP/IP messages can be sent to multiple networks. Conventional TCP/IP reliable file transfer protocols support point-to-point (i.e., unicast) file distribution only. That is, packets are sent to each address in turn.
Most packets today are sent as unicasts (one to one) or broadcasts (one to all). Unicasts have a destination IP address that points to a single recipient. Broadcasts generally have a destination address for all hosts on a specific subnet (a component of a larger network). Multicast is a one to many type of data transmission that permits a sender to transmit a message to multiple recipients at the same time. Multicast is similar to broadcasting, except that multicast generally implies sending information to a list of specific users (e.g., a subset of all possible recipients), whereas broadcast generally implies sending a message to all possible recipients.
One relevant difference between a multicast packet and a unicast (or broadcast) packet is that the destination IP address in a multicast packet refers to an address corresponding to a group of hosts, rather than a specific network or specific host. Thus, multicast traffic on a network can be distinguished from unicast and broadcast traffic by examining the destination IP address, which in a multicast packet identifies the specific multicast group for which an IP packet was sent. For example, if a sender wants to send data to a group of receivers, the sender need only send the data to the particular multicast group address associated with that group. Because receivers in a group can listen at that address for messages, these receivers can receive the packets and process the contents.
Multicast networking and the applications providing one to many services using multicast are becoming important because multicast networks enable applications to scale; that is, multicast enables the applications to service many users without overloading network and sender resources. Widespread usage of applications servicing many users generally is not possible without the scaling provided by efficient network services such as those provided by multicast. Typical applications for reliable multicast data distribution include electronic software distribution, transmission of critical information to field offices, distribution of multimedia information to local senders, replication of web senders to the edges of networks for improved performance, and providing subscription based “push” information delivery to receivers who have signed up for a particular information service.
A multicast group is the group of host recipients that simultaneously receive data via the reliable multicast data transfer. IP multicast groups are dynamic and can be set up and torn down in seconds. IP multicast session setup protocols that have been standardized support two basic group models for two basic multicast applications. One group model is the conferencing model, in which a host is “invited” to join a conference, and a many to many multicast group is set up. This conference can be a videoconference, a data conference, or some other type of conference. A second group model is the broadcast model. This is analogous to television broadcast, where events and their times and “channels” are continuously broadcast over a particular channel, much as is done on many cable TV systems. Any receiver seeing an event may join the group and receive the information, in a manner analogous to tuning a TV receiver to the channel desired. Both of these models assume that anyone can access the groups with no restriction. There is no knowledge of group membership in the one to many group model, and there may not be knowledge in the conference model.
SUMMARY OF THE INVENTION
Efficient network technologies such as multicasting permit the same content to be sent electronically via a network to many host computers, which can be servers, desktops or mobile laptops. A problem that can occur when sending content to many destination computers, however, is that not all desired destination computers receive the content. This can occur if there was an outage of the destination computer or of the link to that computer, such that a destination computer would never be available for receiving content during a session. Another way that destination computers do not receive all content is when a session ends before the destination computer is finished receiving data, such that the destination computer received some of the content but not all.
The problem of not receiving content has serious implications for the destination computers. For example, the content being sent in some instances is content being sent to servers or other computers, such as crucial information that is required to be on many servers which are required to stay synchronized with the same content. In another example, the content being sent may be software that must be deployed and installed on one or more desktop computers, such as software needed to provide support services to the users and service personnel accessing the desktop computers.
For situations where a destination computer is unavailable for a session and for situations where a destination computer does not receive all data, it is an object of the invention to provide systems and methods for automatically scheduling a transmission to the group members that did not receive all or part of the content.
An object of the invention is to send content to receivers that did not or could not receive data during a multicast data transmission session. In accordance with this and other objects of the invention, one aspect of the invention relates to a method of managing a session during which data is sent to receivers. A first message is sent over a network to a list comprising at least one receiver, the first message relating to receiving data during a first session. Replies are received over the network from the receivers on the list. Based on the replies received, each receiver on the list that will not be receiving data during the first session is identified. After the first sess
Cates Kenneth
Fiorentino Richard
Miller C. Kenneth
Rosenberg Alan
Baker Stephen M.
Darby & Darby
The Fantastic Corporation
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