Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-11-26
2001-04-03
Ngo, Ricky (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S466000, C370S468000, C370S477000
Reexamination Certificate
active
06212186
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ATM (Asynchronous Transfer Mode) exchange, and more particularly to a cell bandwidth control apparatus for performing bandwidth control for ATM cells sent from the ATM exchange onto the line side.
2. Description of the Related Art
In an ATM exchange, a plurality of line adapters are connected to an ATM switch. ATM cells are input to the ATM exchange by payloads incoming from lines operating at various speeds; generally, the internal circuitry of the ATM exchange accommodating the lines is operating at a speed different from the speeds of the lines, and its operating speed is higher than the operating speeds of the lines.
Data formatted, for example, to SONET (Synchronous Optical Network), DS3, or other specifications, is input from the line side to the line adapter. The line adapter removes the overhead (OH), header, etc. of the data, extracts ATM cells carried in the payload, and sends the ATM cells to the ATM switch after converting each cell into an ATM switching cell with an internal routing tag appended thereto. Conversely, for ATM cells input to the line adapter from the ATM switch, the line adapter removes the ATM switching tag from each ATM cell, and maps the cells into the payload applicable on the line side, and sends them out onto the line side after appending the overhead, header, etc. of SONET, DS3, etc.
In this way, since the overhead (OH), header, etc. of SONET, DS3, etc. are appended when outputting an ATM signal from the line adapter onto the line side, the effective bandwidth for an outgoing highway signal that can be carried in the payload on the line side, i.e., the combined signal of user cells, OAM (Operations, Administration, and Maintenance) information cells for higher layers, etc., is 149.76 Mbits/s.
When the bandwidth of 149.76 Mbits/s is fully used, and OAM cells, for example, are inserted in the remaining bandwidth of 5.16 Mbits/s (155.52 Mbits/s−149.76 Mbits/s=5.76 Mbits/s) at the ATM exchange, a problem arises in that the bandwidth increases correspondingly and data equivalent to the bandwidth of the inserted OAM cells is discarded at the line side regardless of the type of cell, whether a user cell or an OAM cell.
SUMMARY OF THE INVENTION
In view of the above problem, it is an object of the present invention to provide a cell bandwidth control apparatus for an ATM exchange, that forcibly inserts empty cells within a bandwidth where signals cannot be sent from the ATM exchange to the line side (hereinafter referred to as the out-of-band area), for example, the above-noted 5.76-Mbit/s bandwidth, and thereby limits the transmission bandwidth available for transmission from the ATM exchange to the line side to the bandwidth where signals can be sent from the ATM exchange to the line side (hereinafter referred to as the line bandwidth), for example, the above-noted 149.76-Mbit/s bandwidth.
It is also an object of the present invention to provide a cell bandwidth control apparatus for use in ATM communications, that can be applied not only when performing transmissions between the ATM exchange and the line side, as described above, but also when performing ATM communications between apparatuses with different line bandwidths.
The present invention thus prevents important cells, such as user cells, from being discarded.
According to the present invention, there is provided a cell bandwidth control apparatus for performing bandwidth control for ATM cells sent from an ATM exchange out on a line side, comprising forced empty cell inserting means for forcibly inserting an empty cell in a highway connected to an ATM switch, wherein with the forced empty cell inserting means inserting a forced empty cell in an outgoing highway leading from the ATM switch to a line adapter, the line bandwidth of the outgoing highway is limited to within the bandwidth of the line accommodated in the line adapter.
The line bandwidth of the outgoing highway is limited to within the bandwidth of the line before an OAM cell is inserted in the outgoing highway. The forced empty cell carries a prescribed forced empty cell indication flag in a tag which is appended to each ATM cell to control the ATM cell within the ATM exchange, and the forced empty cell is distinguished from other cells by the forced empty cell indication flag. Alternatively, the cell bandwidth control apparatus includes a separate line for forced empty cell identification, which is provided separately from the forced empty cell, and the forced empty cell is distinguished from other cells by a forced empty cell identification signal from the separate line.
The cell bandwidth control apparatus further comprises a forced empty cell filtering device for detecting only a forced empty cell on the outgoing highway, wherein the forced empty cell detected by the forced empty cell filtering device is directly looped back by the forced empty cell inserting means for insertion into an incoming highway leading from the line adapter to the ATM switch, thereby limiting the line bandwidth of the incoming highway to within the bandwidth of the line accommodated in the line adapter.
The cell bandwidth control apparatus further comprises a counter for counting the number of forced empty cells detected on the outgoing highway by the forced empty cell filtering device, wherein the forced empty cell inserting means successively inserts forced empty cells in the number counted by the counter into the incoming highway rather than directly looping back the detected forced empty cells on the outgoing highway for insertion into the incoming highway.
The cell bandwidth control apparatus includes test cell inserting means for mapping test data into a payload area of the forced empty cell, thereby providing the forced empty cell with a line test function. Further, when the line adapter is multiplexed to accommodate a plurality of lines on a single highway, the cell bandwidth control apparatus includes a line identification number device for adding a line identification number within the tag, which is appended to each ATM cell to control the ATM cell within the ATM exchange, wherein control for forced empty cell insertion is carried out for each of the lines by the line identification number device.
According to the present invention, the cell bandwidth control apparatus for limiting the communication bandwidth in ATM communications between ATM communication apparatuses having different communication bandwidths, is provided at the ATM communication apparatus having the larger communication bandwidth, and empty cells are forcefully inserted within a difference bandwidth between the larger communication bandwidth and the communication bandwidth of the ATM communication apparatus having the smaller communication bandwidth so that the former bandwidth is held to within the latter bandwidth, thereby limiting the communication bandwidth of the larger communication bandwidth ATM communication apparatus.
REFERENCES:
patent: 5642421 (1997-06-01), Gray et al.
patent: 5663959 (1997-09-01), Nakagawa
patent: 5799003 (1998-08-01), Fujimaki et al.
Plural-Line Terminating Apparatus and OAM Processing Drawings Figs 1-23 U.S. Pending Application No. 924,052, Filed on Aug. 28, 1997.
Cell Bandwidth Control Apparatus Drawings Figs 1-11 U.S. Pending Application No. 08/979,431 filed on Nov. 26, 1997.
Aihara Naoki
Kamoi Jyoei
Tada Iwao
Yamaguchi Tomoyuki
Fujitsu Limited
Helfgott & Karas P.C.
Ngo Ricky
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