Multiplex communications – Diagnostic testing – Determination of communication parameters
Reexamination Certificate
1999-10-01
2004-03-09
Kizou, Hassan (Department: 2662)
Multiplex communications
Diagnostic testing
Determination of communication parameters
C370S242000, C370S254000, C709S224000
Reexamination Certificate
active
06704289
ABSTRACT:
TECHNICAL FIELD
This invention relates to a technique for determining the service availability in a connectionless network, such as an Internet Protocol network, to facilitate restoration of lost bandwidth.
BACKGROUND ART
Data networks, such as those maintained by communications service providers like AT&T, generally fall in the category of “connection-based or “connectionless” networks depending whether the path traversed by packets is known in advance of transmission. Connection-based data networks, such as those providing traditional Frame Relay Service, typically have Permanent Virtual Circuits (PVCs) that link network elements. Thus, in a traditional connection-based data network, each packet in a data stream passing between the same pair of network elements traverses the same PVC. By contrast, in connectionless data networks, and particularly Internet Protocol (IP) data networks, multiple paths typically exist between each origin and destination. Often different packets within the same data stream will traverse different-paths. Unlike a connection-based data network in which the transmission path is known in advance, no advance knowledge usually exists about the path traversed by each packet in a connection-less data network.
The lack of apriori knowledge of the transmission path, and the fact that connectionless IP networks often possess a wide range of access bandwidths, makes the task of estimating unavailable end-to-end customer bandwidth difficult. The unavailability of a particular path in a connectionless data network may or may not affect the transmission of packets, and may or may not affect customer bandwidth, depending on the availability of other paths within the network. In contrast, estimating unavailable customer bandwidth in a connection-based Frame Relay Service or ATM network is simply a matter of measuring the number of PVC outages that last more than a prescribed interval.
In the past, some network service providers attempted to gauge unavailable customer bandwidth in connectionless data networks by launching “pings” to probe network connectivity. The ratio of pings not received at a customer premise to the total number of pings sent within the interval of testing will provide a measure of unavailable customer bandwidth. However, sending frequent pings across the network consumes network resources. Thus, attempting to measure unavailable customer bandwidth in this manner can actually impair performance.
Thus, there is a need for a measuring unavailability in a connectionless data network that overcomes the disadvantages of the prior art.
BRIEF SUMMARY OF THE INVENTION.
Briefly, the present invention provides a technique for determining unavailable customer bandwidth in a connectionless IP network and for restoring bandwidth when the unavailable customer bandwidth exceeds a prescribed level. In other words, the present invention substantially maintains the ability of a customer to transmit data through the network at a specified service level. To maintain customer bandwidth, the technique of the invention first establishes (measures) network accessibility and continuity. Network accessibility is defined as the availability of the network to receive a packet from a customer router at an network ingress point. Network continuity is defined as the ability of the network to deliver to an egress point a customer packet received at the network ingress point. The service availability of the network is then determined in accordance with the previously established accessibility and continuity values. The actual service availability is compared to a desired service availability. If the desired service availability exceeds the actual service availability, the customer bandwidth is restored, either by way of repair, adjustment, modification or enhancement to the network.
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patent: 5867483 (1999-02-01), Ennis et al.
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U.S. patent application Ser. No. 09/271,715, filed Mar. 18, 1999, Method For Measuring The Availability Of Router-Based Connectionless Networks (D'Souza, K.L.).
D'Souza Kevin L
Kogan Yaakov
Maguluri Gangaji
Ramachandran Gomathi
AT&T Corp.
Kizou Hassan
Lee Timothy
LandOfFree
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