Electrical computers and digital processing systems: multicomput – Computer-to-computer data routing – Prioritized data routing
Reexamination Certificate
1996-11-15
2002-07-09
Meky, Moustafa M. (Department: 2153)
Electrical computers and digital processing systems: multicomput
Computer-to-computer data routing
Prioritized data routing
C709S245000, C709S246000
Reexamination Certificate
active
06418477
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed generally to computer communication networks, and in particular, to an improved communication network that provides superior quality of service (hereinafter “QOS”) guarantees.
2. Description of the Related Art
Quality of Service guarantees are necessary for efficient network communication, and in particular for distributed multimedia applications. The need to provide a high quality of service for continuous-media and real time applications is well recognized in the communication networking community.
Two known modes of communication within a computer communications network are circuit-switching and packet-switching. In a communications network configured for circuit-switching, a dedicated communication path between two (or more) communicating programs is established for use by the communicating programs only. A traditional telephone network is an example of a communication network that utilizes circuit-switching. Although an advantage of a communications network that uses circuit-switched connections is very reliable communication between the communicating programs, a severe drawback is that resources must be reserved for establishing and maintaining the entire link during the communication. Since the computer communication is “bursty” (i.e. communicating programs communicate with each other by exchanging information in bursts in which information is exchanged continuously for a small period of time followed by relatively “long” periods of silence), a communication network based on circuit-switching has a relatively low utilization of network resources.
In a network that employs packet switching, the two (or more) communicating programs do not have any reserved physical network resources. Instead, information originating from a sender program and destined for a receiver program is transmitted in units called “packets”. Each packet contains information that identifies the receiver program to which the packet of information is intended. And, based on the address of the receiver program, the packet will be continuously switched throughout the network until the intended receiver program is reached.
In a packet-switched network, packets of information may be forwarded to their destination by intermediate nodes using information in a packet header. The information may be a destination host address (as in IP) or a connection identifier (such as the VPI/VCI field in ATM). Packets can typically be transmitted by a sending host at any time. In some networks, e.g. ATM, packets are constrained to be transmitted using a rate-controlled approach. Each packet is routed independently by the nodes in the network. However, once the packet of information is established by the sender program, the contents of the information packet does not change and remains unchanged as it moves about the nodes of the network until it reaches its destination program.
Packet-switching networks can operate in two modes, as datagrams or as virtual circuits. In a typical datagram mode, packet headers contain (a) information identifying the address of the recipient and (b) any other information that may be needed for processing the packet at any intermediate nodes in the network. The packets of information being transmitted in a network in the datagram mode may be delivered out of order and can take any available path to the receiver in the network. In fact, in a typical situation, the transmitted packets of information are not transmitted together or reach the recipient together since there is no predefined path in which the packets of information travel. Accordingly, there is no guarantee that all the transmitted information will in fact (a) reach the recipient or (b) reach the recipient in the order in which it was transmitted. This latter problem becomes significant in the situation in which information must be received within a specified period or in a particular sequence.
The virtual circuit mode is advantageous over the datagram mode in that the header may be more simply configured since it may merely need contain only the identifier for the path on which it is transmitted in the network.
In a network that operates in a virtual circuit mode, a fixed route is selected at the beginning of the communication for all the packets originating from the receiver.
In general, packet switching better utilizes network resources than networks utilizing only circuit-switching. However, packet-switching networks do not provide the same quality of service (QOS) guarantees provided by a circuit-switching network since, by definition, there are no dedicated physical circuit connections among the communicating programs (computers).
As computer networks further evolve to support audio and video applications together with data applications, a need exists to provide increasing and more reliable quality of service guarantees. Several prior attempts have been made to incorporate networking schemes which provide satisfactory and sufficient quality of service guarantees. Invariably, all of these schemes are based on some form of virtual switching techniques. That is, the known virtual-circuit switching networks utilize resources which are reserved when the virtual circuit is established and released when the virtual circuit is destroyed. When virtual circuits are established, known admission control schemes can be used to attempt to guarantee that a certain quality of service is provided for the establishment of node interconnections before the virtual circuit is established.
However, computer networks that only utilize virtual circuits are deficient in the following respects. For example, establishing a virtual circuit typically takes a relatively long time and does not provide efficient and sufficient quality of service guarantees in communications that last a relatively short amount of time.
Therefore, a network architecture for use in a communication network that provides for greater QOS guarantees than heretofore achieved and which overcomes the aforementioned deficiencies is desired.
SUMMARY OF THE INVENTION
Generally speaking a communications network for transmitting an information packet between nodes of the network is provided. The network preferably comprises at least a source node and a destination node and an information cluster transmittable between the source node and the destination node and for having attached thereto an information packet. The information packet is attachable to the information cluster at the source node when the information cluster is at the source node and detachable from the information cluster at the destination node when the information cluster is at the destination node.
An information cluster will travel about the network along a predetermined path between preselected nodes within the network. Information packets originating at a node among the selected nodes along the predetermined path can be attached to the information cluster when the information cluster arrives at the particular node at which the information packet is waiting. Similarly, the information packet can get off the information cluster at any node of the selected nodes when the information cluster reaches its destination node.
The entire network, in addition to carrying information packets, will preferably carry a plurality of information clusters, although a network with as few as one information cluster is contemplated by the present invention. The information clusters are pre-scheduled and travel between selected nodes at preferably regular intervals. Because of the regularity and predictability of the information clusters, a particular node in the network will know in advance when an information cluster will arrive at that particular node. In this way increased and more reliable QOS guarantees can be provided to the information packets in the network which are attached to the information cluster.
In addition to providing information clusters as disclosed herein, the network may contain additional known networking schemes as described above
Le Hien C.
Meky Moustafa M.
Philips Electronics North America Corporation
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