Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Patent
1995-04-13
1997-12-09
Olms, Douglas W.
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
370437, 370443, 370445, H04J 324
Patent
active
056967640
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an ATM exchange and, more particularly, to an ATM exchange which is capable of maintaining a required QOS (quality of service) and which is capable of detecting a long-term congestion and avoiding the congestion in a case where there are simultaneously both a bandwidth-guaranteed connection call and a non-bandwidth-guaranteed connection call.
BACKGROUND ART
There is increasing demand not only for audio communication and data communication but also for multimedia communication in which moving pictures are transmitted as well as audio and data. As a means for realizing such broadband communication, an agreement has been reached upon an exchanging technique in a B-ISDN (Broadband-ISDN) system, which is based on an asynchronous transfer mode (ATM), and the technique is being put to practical use.
In the ATM, all the information is converted into fixed information which is called a cell without depending upon continuous information such as an audio and a moving picture or burst information such as data, and transferred at high speed without depending upon the respective communication speed. More specifically, in the ATM, a line is allocated to a plurality of calls by establishing a multiplicity of logical links on a physical line. The moving picture data and the audio data transmitted from a terminal corresponding to each call are separated into information units (which are called cells) having a fixed length, and the cells are serially transmitted over a line, thereby realizing multiplex communication.
Each cell is composed of a block having a fixed length of 53 bytes, as shown in FIG. 19. In the 53 bytes, 5 bytes constitute a header portion HD and 48 bytes an information field (information portion) DT. The header portion HD includes a virtual channel identifier (VCI) for identifying a call so as to indicate the destination even after the data is separated into blocks. The header portion HD also includes a virtual path identifier (VPI) for specifying a path, a generic flow control (GFC) which is used for flow control between links, a payload type (PT), a header error control (HEC) for correcting errors, etc.
(a) ATM Network
FIG. 20 schematically shows the structure of an ATM network so as to explain ATM transmission. In FIG. 20, the reference numerals 1a, 1b represent ATM terminals, and 3 an ATM network. The ATM network 3 is provided with an information network 3a for transferring a data cell, and a signal network 3b for transferring a control signal. The call processing processor units (CPUs) 3d-1 to 3d-n of the ATM exchanges 3c-1 to 3c-n in the information network 3a are connected to the signal network 3b.
When the originating terminal 1a executes a calling operation so as to call the terminating terminal 1b, the cell assembling portion of the originating terminal separates the SET UP message (data which includes the originating number, the terminating number, the type of terminal, the average cell rate, the peak cell rate, etc.) into cell units, attaches a signal VCI (which is determined in advance for the respective terminal) to each divided data to form a signaling cell and supplies the signaling cell to the ATM network 3.
When the signaling device of the ATM exchange 3c-1 (on the originating side) receives the signaling cell, it assembles the information contained in the signaling cell and supplies the assembled information to the CPU 3d-1. On the basis of the received message, the CPU executes calling such processing as processing for analyzing calling-party service, billing processing, processing for interpreting digits on the side of the terminating party, etc., determines a path (VPI) and a virtual channel identifier (VCI), and in accordance with a protocol No. 7, supplies connection information which includes data such as the originating number, terminating number, VPI and VCI, to the subsequent relay exchange 3c-2 via the signal network 3b. The relay exchange 3c-2 executes similar processing to that of the exchange 3c-1 on the originating side
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Hatano Takashi
Kakuma Satoshi
Katoh Masafumi
Soumiya Toshio
Watanabe Naotoshi
Fujitsu Limited
Hom Shick
Olms Douglas W.
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