Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1997-11-07
2001-02-06
Hsu, Alpus H. (Department: 2738)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S253000, C370S395430, C370S412000, C370S465000
Reexamination Certificate
active
06185186
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a system for dividing information that should be transferred into fixed-length cells and transferring the fixed-length cells, more specifically, to a fixed-length cell handling switching system and a method for controlling a read rate of a fixed-length cell suitable for use upon processing cells in various quality classes.
(2) Description of the Related Art
As a fixed-length cell handling switching system which handles fixed-length cells, there is an ATM switching system which switches, in particular, ATM (Asynchronous Transfer Mode) cells as fixed-length cells. ATM switching technique for applying such ATM switching system has been agreed as a next-generation switching system in ITU-T, and is being lively developed in various organizations as a technique which can realize wide-area ISDN (Integrated Services Digital Network).
The above ATM switching system uses an ATM cell which is a fixed length-cell of 53 octets as a unit for transferring information. The ATM cell has a header portion of 5 octets in which control information (destination, etc.) is stored and a data portion (payload) of 48 octets.
The ATM switching technique can transfer ATM cells asynchronously, and increase the number of ATM cells to be transferred in a given time when it is desired to transfer information at a high rate. On the other hand, when information is transferred at a low rate, the ATM switching technique decreases the number of ATM cells so as to readily regulate an information transmission rate.
By applying the above ATM switching technique, it is possible to uniformly handle information ranging from a low rate of several kbps such as voice data and the like to a high rate of several hundreds Mbps such as images and the like to transfer the information.
Since the ATM switching system handles communication services having various cell qualities such as voice, image, data, etc., a controlling system which can satisfy each quality and effectively make full use of resources of the switching system is required.
However, in a fixed-length cell handling switching system as the above ATM switching system, processes conducted in the switching system are complicated. For this, the above fixed-length cell handling switching system controls all media based on a service corresponding to data in the highest quality class among various services so that it is impossible to effectively use network resources.
In addition, since resources of the switching system are not divided in each quality class, cell discarding occurs depending on a state at that time irrespective of a grade of a quality if cell congestion occurs. Namely, congestion of cells in a low quality class may induce discarding of a cell in a high quality class. If cell congestion occurs in another communication, communication satisfying a required quality becomes impossible.
SUMMARY OF THE INVENTION
In the light of the above problem, an object of the present invention is to provide a fixed-length cell handling switching system and a method for controlling a read rate of a fixed-length cell, which can dynamically change a read rate of each quality class, thereby conducting a transmitting process according to a required quality class without affecting fixed-length cells of calls having different qualities on each other.
The present invention therefore provides a fixed-length cell handling switching system having a call handling control unit for controlling call handling when communication is made using a fixed-length cell comprising a quality class identifier relating unit for relating a quality class identifier according to a quality class of the fixed-length cell, a quality controlling buffer unit having a managing unit for managing the fixed-length cell related to the quality class identifier on the basis of the quality class identifier, a buffer for storing the fixed-length cell managed by the managing unit, and a read rate information holding unit for holding information about a read rate of the fixed-length cell stored in the buffer, the cell handling control unit comprising a virtual band setting unit for setting a virtual band in the buffer on the basis of the quality class and a declared band in a call presently set, and a read rate setting control unit for setting and controlling a read rate of the fixed-length cell held in the read rate information holding unit on the basis of the virtual band set by the virtual band setting unit.
The present invention also provides a fixed-length cell handling switching system comprising a quality class identifier relating unit for relating a quality class identifier to a fixed-length cell flowing in through a route of a set call on the basis of a quality class and a declared band when the call is set, a managing unit for managing a route of the fixed-length cell inputted from the quality class identifier relating unit on the basis of the quality class identifier related by the quality class identifier relating unit, a buffer for storing the fixed-length cell managed by the managing unit, and a read rate setting control unit for setting a virtual band of the buffer on the basis of the quality class-and the declared band and controlling a read rate for the fixed-length cell held in the buffer on the basis of the virtual band.
The present invention still also provides a method for controlling a read rate of a fixed-length cell stored in a buffer on the basis of a quality class of communication from the buffer comprising the steps of setting a virtual band of the buffer on the basis of the quality class and a declared band, relating a quality class identifier to a fixed-length cell flowing in through a route of a set call on the basis of the quality class of the communication and the declared band declared when the call is set, managing the fixed-length cell related to the quality class identifier on the basis of the quality class identifier and storing the fixed-length cell in the buffer, and relating the fixed-length cell stored in the buffer at a read rate determined on the basis of the virtual band.
According to the fixed-length cell handling switching system and the method for controlling a read rate of a fixed-length cell of this invention, it is possible to set and control each of fixed-length cells having different qualities to a read rate according to its quality. If there if a declaration exceeding a read rate having been set, the read rate may be readily and dynamically changed, and cell discarding and cell delay may be independently controlled in each quality class without affecting cells of calls having different qualities on each other. It is therefore possible to certainly switch a fixed-length cell to be transmitted according to a required quality class so as to largely improve a processing capability of the system.
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Fujitsu Limited
Helfgott & Karas P.C.
Hsu Alpus H.
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