JPH0426251A - Multiplex cross connecting device - Google Patents

Abstract

PURPOSE:To reduce cell abandonment caused by the overflow from a buffer by transmitting a control signal for limiting the reception of a cell to a required path when the result of measuring the queue length of the buffer in this multiplex cross connecting device reaches a certain constant value shorter than the length of the buffer. CONSTITUTION:A spatial switch 2 is provided as a cell switch capable of switching the cell inputted from an input transmission line 7 to an arbitrary output transmission line 6, and a buffer 3 is provided to tentatively store the cell. Then, a read part 4 is provided to read out the cell from the buffer 3. Further, a monitoring part 5 is provided to transmit a control signal 10 for limiting the reception of the call in the required path when the result of measuring the queue length of the cell stored in the buffer 3 reaches a certain constant value Qt shorter than a buffer length Qm. In this case, the number of buffers 3, read parts 4 and monitoring parts 5 are provided while matching with the number N of input side and output side transmission lines 7 and 6. Thus, the rate of the cell abandonment caused by the overflow from the buffer can be sharply reduced, and high-definition lines can be obtained.

Description

[Detailed description of the invention] Industrial application field] The present invention is directed to ATM (asynchronous transmission system).
ousTransfer Mode) Used in multiplex cross-connect devices in transmission networks.

C. Prior Art] In a multiplex cross-connect device, even if a buffer overflow occurs, it does not have a control means to deal with it, or it does not have a corresponding control means after detecting the buffer overflow (whether the cells are discarded or not). It was restricting the acceptance of calls to the path.

Problems that Nikahu is trying to solve] In the conventional method, when cells are discarded due to a buffer overflow, in order to limit the acceptance of calls to the corresponding path, the cell discard can be prevented. There were drawbacks that occurred. In addition, there is a drawback that there is a high probability that cells will be discarded even during the period until the control to restrict acceptance of calls to the path becomes effective.

An object of the present invention is to eliminate or reduce cell discards due to buffer overflow, and when the result of measuring the queue length of a buffer in a multiplexing cross-connect device reaches a certain value smaller than the maximum buffer length, the required An object of the present invention is to provide a multiplexing cross-connect device having means for sending a control signal for restricting call admission to a path.

[Means to solve the problem]

The present invention provides a multiplexing cross-connect device including a cell switch capable of switching cells input from an input transmission path to an arbitrary output transmission path, and a buffer for temporarily storing the cells. Monitoring that measures the queue length of accumulated cells and, when the measured queue length reaches a certain value smaller than the buffer length, sends a control signal to limit the acceptance of calls to the desired path. It is characterized by having a section.

[Effect]

The monitoring unit measures the queue length of cells accumulated in the buffer, and limits the acceptance of required calls when the measured queue length exceeds a certain value Qt below the buffer length of 0 m. Sends out control signals. As a result, cell discards caused by buffer overflow are mainly caused by traffic until the effect of restricting call admission becomes apparent. This probability can be made extremely small by setting Qt to an appropriate value.

Therefore, it is possible to significantly reduce the cell discard rate due to buffer overflow, and it is possible to provide a high quality line.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG. 2 is a block diagram showing details of the buffer.

The present embodiment includes a space switch (SW) 2 as a cell switch capable of switching cells input from an input transmission path 7 to an arbitrary output transmission path 6, and a buffer (BU) for temporarily storing the cells. 3 and a reading unit (R) 4 for reading out cells from the buffer 3). A control signal 1 for measuring the queue length of a cell and restricting the acceptance of calls to a desired path when the measured queue length reaches a certain value Qt smaller than the buffer length Qm.
It is equipped with a monitoring section that sends out 0 (Vv'A>5).

Note that here, the buffer 3, the reading section 4, and the monitoring section 5
is, according to the number N of input transmission lines 7 and output transmission lines 6,
N pieces are provided each.

FIG. 3 is a block diagram showing an example of the flow of control signals in this embodiment. Three multiplex cross-connect devices 1 shown in FIG. A termination (PT) 9 is provided to transmit the control signal 10 to the operational network (
T M N > (Logical or physical space for transferring or processing vehicle information necessary for communication network operation, , -,
-1-Work; Telecommunication
+'Janall:ement Network)
The signal is sent to the path end 9 via ε4.

The present embodiment operates as follows. Note that t is the time taken to read a cell onto the transmission path.

The monitoring unit 5 measures the queue length of the buffer 3 at fixed time intervals TO·t (TO≧1). Measuring rIA
The unit of interval TO is cell reading time. When the queue length of the buffer 3 satisfies the conditions described below, the monitoring unit 5 sends a control signal 10 to a path termination 9 of a specific path described below to instruct a restriction on call acceptance.

Here, the conditions under which the buffer monitoring unit 5 issues an instruction to limit call acceptance are any one of the following or a combination of several.

(1) Queue length is Qt of buffer length Qm (≧1
) times.

(11) The queue length exceeds Qt of the buffer length Qm consecutively X (≧1) times.

(iii) The queue length exceeds Qt of the buffer length Qm X (≧1) times during a certain period of time TO·t.

(+V) The queue length exceeds Qt of the buffer length Qm consecutively X (≧1) times during a certain period of time TO·t.

(v) The average of the past one observed queue length is the buffer length Qm
of which exceeds Qt.

(■1) Weighting of the past one observation queue length shown by the following equation is such that the sum Q (n) exceeds Qt of the buffer length Qm.

However, Q (n) is the length of the n previous observation queue, and a is a coefficient.

Further, the path for which the call acceptance/acceptance restriction instruction is issued is any one of the following or a combination of some of the following.

(i) All paths accommodated in the output-side transmission path corresponding to the buffer.

(ii) K (≧1
) paths.

(iii) Randomly select K (≧1) paths from among the paths accommodated in the output-side transmission line corresponding to the buffer.

(iv) Among the paths accommodated in the output transmission path corresponding to the buffer, K (≧1> paths) are selected in order from the highest priority path according to a predetermined priority order.

(v) K (≧1) paths that accommodate the largest number of lines among the paths that are accommodated in the output-side transmission path corresponding to the buffer.

(Vl) Among the paths that do not correspond to the buffer and are accommodated in the transmission line on the output side, K (≧1) paths are arranged in descending order of the capacity of the accommodated line.

(vii) Among the paths accommodated in the output transmission line corresponding to the buffer, K (≧1) paths are arranged in order from the path with the largest number of passing nodes or the path with the smallest number of nodes.

FIG. 4 is a block diagram showing another example of the flow of control signals in the second embodiment.
Instead, it is sent directly via the opposite path that is paired with the bus.

Through the above operations, by appropriately setting the value of Qt, it is possible to reduce cell discards due to buffer overflow.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

In the second embodiment, the positions of the space switch (SW) 2, the buffer (BU) 3, the reading section (R) 4, and the monitoring section 5 are swapped in the first embodiment shown in FIG. The feature of the present invention is that a monitoring section 5 is provided (see FIG. 2).

Cells arriving at the multiplexing cross-connect device 1 from the input side transmission line 7 are accumulated in the buffer 3, and sent out to the space switch 2 by the cell reading section 4. At this time, the cell reading section 4 controls so that cells are not sent out to the same output transmission line 6 at the same time. The space switch 2 switches to the target output transmission line 6.

The details and operation of the buffer 3 and monitoring section 5 are the same as in the first embodiment.

Note that the buffer 3 shown in the first embodiment and the second embodiment
It is also possible to arrange them in a distributed manner inside the space switch 2.

〔Effect of the invention〕

As explained above, the present invention limits acceptance of calls to a desired path when the queue length of a buffer in a multiplex cross-connect device reaches a certain value smaller than the buffer length. This has the effect of reducing cell discard due to buffer overflow.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 2 is an explanatory diagram showing the structure of the buffer. FIG. 3 is a block diagram showing an example of the route through which the control signal passes. FIG. 4 is a block diagram showing another example of the route through which the control signal passes. FIG. 5 is a block diagram showing a second embodiment of the present invention. 1... Multiplexing cross-connect device (~iX>, 2...
... Space switch (SW), 3... Buffer (B
U), 4... Reading unit (R), 5... Monitoring unit (WA
), 6... Output side transmission line, 7... Input end transmission line,
8... Operation m (TMN), 9... Bus # end (PT
), 10... control signal. Patent Applicant: Nippon Telegraph and Telephone Corporation Agent, Patent Attorney Nao Takashi Ide Diagram No. - Engraved diagram of protruding shaft 1 No. Tora-shi φj (buffer officer θ day) Diagram No. - Example of actual flag (Yoke number) Liquid stop example) Figure 1 - Actual axis 1 (control signal shore, stop D

Claims (1)

[Claims] 1. A multiplexing cross-connect device comprising a cell switch capable of switching cells input from an input transmission path to an arbitrary output transmission path, and a buffer for temporarily storing the cells, The queue length of cells accumulated in the buffer is measured, and when the measured queue length reaches a certain value smaller than the buffer length, a control signal is sent to restrict acceptance of calls to a desired path. A multiplexing cross-connect device characterized by comprising a monitoring unit that sends out signals.