Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-12-10
2002-06-25
Ton, Dang (Department: 2661)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S395420
Reexamination Certificate
active
06411617
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to network communications systems, and more particularly, to a method and apparatus for transmitting and switching data packets operating under the principles of a first quality of service (e.g., SIMA technology) in a system designed to transmit and switch data packets operating under the principles of another quality of service (e.g., ATM technology).
BACKGROUND OF THE INVENTION
Communication of digital content between remote computing systems is increasing at astronomical rates as networks continue to proliferate throughout the globe. A great majority of personal computers used in business and in educational institutions are connected to a network, and the importance of emerging network technologies continues to increase as the masses feverishly enter the domain of the Internet. Data, audio, graphics, motion video, and other multimedia content are all vying for transmission availability in an era of limited, yet improving, bandwidths.
Providers of network services, and of communications system infrastructure, are faced with a number of complex issues in providing necessary bandwidth and quality service. These issues include management of network capacity, prioritization and management of both real-time and non-real-time data traffic, and implementing fair billing schemes. One solution to many of these problems is the use of packet-based digital data transmissions having an associated “quality of service,” such as the transmission technology referred to as Asynchronous Transfer Mode (ATM). Those skilled in the art understand ATM to constitute a communications networking concept that, in theory, addresses many of the aforementioned concerns, such as by providing a capability to manage increases in network load, supporting both real-time and non-real-time applications, and offering, in certain circumstances, a guaranteed level of service quality.
A conventional ATM service architecture typically provides a number of predefined quality of service classes, often referred to as service categories. Each of the service categories includes a number of quality of service (QoS) parameters that define the nature of the respective service category. In other words, a specified service category provides performance to an ATM virtual connection (VCC or VPC) in a manner specified by a subset of the ATM performance parameters. The service categories defined in the ATM Forum specification reference hereinbelow include, for example, a constant bit rate (CBR) category, a real-time variable bit rate (rt-VBR) category, a non-real-time variable bit rate (nrt-VBR) category, an unspecified bit rate (UBR) category, and an available bit rate (ABR) category.
The constant bit rate service class is intended to support real-time applications that require a fixed quantity of bandwidth during the existence of the connection. A particular quality of service is negotiated to provide the CBR service, where the QoS parameters include characterization of the peak cell rate (PCR), the cell loss rate (CLR), the cell transfer delay (CTD), and the cell delay variation (CDV). Conventional ATM traffic management schemes guarantee that the user-contracted QoS is maintained in order to support, for example, real-time applications, such as circuit emulation and voice/video applications, which require tightly constrained delay variations.
The non-real-time VBR service class is intended to support non-real-time applications, where the resulting network traffic can be characterized as having frequent data bursts. Similarly, the real-time variable bit rate service category may be used to support “bursty” network traffic conditions. The rt-VBR service category differs from the nrt-VBR service category in that the former is intended to support real-time applications, such as voice and video applications. Both the real-time and non-real-time VBR service categories are characterized in terms of a peak cell rate (PCR), a sustainable cell rate (SCR), and a maximum burst size (MBS).
The unspecified bit rate (UBR) service category is often regarded as a “best effort service,” in that it does not specify traffic-related service guarantees. As such, the UBR service category is intended to support non-real-time applications, including traditional computer communications applications such as file transfers and e-mail.
The available bit rate (ABR) service category provides for the allocation of available bandwidth to users by controlling the rate of traffic through use of a feedback mechanism. The feedback mechanism permits cell transmission rates to be varied in an effort to control or avoid traffic congestion, and to more effectively utilize available bandwidth. A resource management (RM) cell precedes the transmission of data cells, which is transmitted from source to destination and back to the source, in order to provide traffic information to the source.
Although the current ATM service architecture described above would appear to provide, at least at a conceptual level, viable solutions to the many problems facing the communications industry, ATM, as currently defined, requires implementation of a complex traffic management scheme in order meet the objectives articulated in the various ATM specifications and recommendations currently being considered. In order to effectively manage traffic flow in a network, conventional ATM traffic management schemes must assess a prodigious number of traffic condition indicators, including service class parameters, traffic parameters, quality of service parameters and the like. A non-exhaustive listing of such parameters and other ATM traffic management considerations is provided in ITU-T Recommendation I.371, entitled Traffic Control and Congestion Control in B-ISDN, and in Traffic Management Specification, version 4.0 (af-tm-0056.000, April 1996), published by the Technical Committee of the ATM Forum.
Notwithstanding the complexity of conventional ATM traffic management schemes, current ATM specifications and recommendations fail to adequately address the need of service providers for a methodology that provides for accurate and reliable charging of services utilized by user's of the network. Even if one were to assume that a charging scheme that accounts for most or all of the currently defined ATM traffic management properties could be developed, such a scheme would necessarily be complex and would typically require administration by highly skilled operators. The high overhead and maintenance costs to support such a billing scheme would likely be passed on to the network provider and, ultimately, to the network user.
The present invention is applicable in a network service class which incorporates a priority-based quality of service. This service class, hereinafter referred to as the Simple Integrated Media Access (SIMA) service class, provides a network management architecture that is simple in concept and in its implementation, yet adequately addresses the quality of service requirements to support a variety of network services, including real-time and non-real-time services. It also provides for the implementation of a simple and effective charging capability that accounts for the use of network services.
However, the existing network infrastructure does not necessarily account for data transmissions utilizing the SIMA service class, which includes a priority-based quality of service. For example, existing ATM switches residing in network nodes are not configured to manage data traffic based on the packet priorities and allowable node priorities implemented in a SIMA service class, and the benefits associated with the SIMA service class are not recognized.
Accordingly, there is a need in the communications industry for a network management method and architecture that recognizes SIMA packets and accounts for the traffic management principles provided by a SIMA service class within a conventional, non-priority-based network infrastructure such as an ATM network system. The present invention provides a solution to these and
Kilkki Matti Kalevi
Ruutu Jussi Pekka Olavi
Altera Law Group LLC
Nokia Telecommunications Oy
Ton Dang
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