摘要:
In an asynchronous transfer mode (ATM) cell transfer apparatus, a valid cell detecting circuit determines whether or not each of ATM cells is valid, based on a specific data of the ATM cell. When it is determined that the ATM cell is not valid, the valid cell detecting circuit discards the ATM cell. On the other hand, when it is determined that the ATM cell is valid, the valid cell detecting circuit writes the ATM cell in a buffer circuit. A read control circuit reads out the ATM cell from the buffer circuit.
摘要:
A coupling device (switch) for a local network operating in the asynchronous transfer mode (ATM) which comprises a central cell memory (CCM) for buffer storage of packets (frames) formed by individual ATM cells and arriving on feed lines, a central memory control device for controlling the storage in the central cell memory (CCM) and the writing and reading processes of the packets into and from the central cell memory (CCM). The control device includes a counting circuit for counting the ATM cells arriving in the central cell memory (CCM) and a discarding circuit for discarding ATM cells packet by packet for preventing a congestion in the central cell memory (CCM). To enable an efficient buffer management also in the case of very small cell memories, in particular below 1000 cells, the central memory control device comprises at least one comparator device connected upstream of the central cell memory, which comparator device cooperates with the counting circuit and with a control logic such that, when a programmable threshold value (Ldisc) for the degree of filling of the central cell memory (CCM) is reached, a programmable number of links (VC) are defined on the basis of the sequence of arrival of the ATM cells assigned to the relevant link (VC), and in that each ATM cell of the packet belonging to the defined VC value is discarded before it arrives in the central cell memory.
摘要:
In a telecommunication system that generates more than one type of communication data stream, in which each data stream exhibits a distinctive data transfer format, bandwidth utilization is improved by first reformatting the different data transfer formats so that all of the data is compatible with a common data transfer protocol, for example, the Asynchronous Transfer Mode (ATM) protocol. The communication data and the corresponding control data, required to maintain communication data alignment, are multiplexed into a single data stream which is then transmitted over a common telecommunication channel to a receiving station.
摘要:
Method and apparatus for segmenting variable length frames into fixed length cells in a network equipment. The method allows preparing information to build the cells resulting in the segmenting of a succession of frames directed to the same destination in said network equipment. The cell may be packed with more than one frame. The cell information comprises the address where to read the frame data in a first storage unit, the cell header itself which indicates if the cell includes data from one packet or for more packets, a pointer per each of said more packets, designating the place of the end of data of the previous packet in the cell and a cell type field indicating one of the following types: a start of a new frame type, a continuation of frame type, a end of current frame type and a start and a end of a new frame type. The segmenting apparatus comprises a finite state machine using an Add/substract unit to compute the cell information and write said cell information in a second storage unit.
摘要:
An asynchronous transfer mode adaptation layer (AAL) processing apparatus using a central processing unit in an asynchronous transfer mode (ATM) terminal includes: a physical layer for performing physical functions and supporting universal test and operations physical interface for ATM (UTOPIA); a software segmentation and reassembly interface device (SSID) for storing ATM cells outputted by the physical layer in a double port RAM under the control of a central processing unit and outputting to the physical layer the ATM cells, which have been stored in the double port RAM by the central processing unit, under the control of the central processing unit; a double port RAM for storing the ATM cells depending upon the control of the central processing unit or the SSID; a system memory for temporarily storing the ATM cells of the central processing unit; and a central processing unit, for storing in the double port RAM the user data, produced by reassembly of the ATM cells stored in the double port RAM, for storing in the double port RAM the ATM cells produced by segmentation of the user data stored in the double port RAM, and for controlling the overall system.