JPS61109344A - Transmission line utilizing rate measuring instrument - Google Patents

Abstract

PURPOSE:To bring a transmission line in the optimum utilizing rate by detecting a carrier on a common transmission line and obtaining a transmission line utilizing rate from the ratio of carrier generating time detected per unit time so as to obtain easily the utilizing rate with simple constitution. CONSTITUTION:A connector 2 is connected to the common transmission line 1 consisting of a coaxial cable to which plural nodes (not shown) of a local area network LAN are connected. A carrier detection circuit 3 detecting the carrier propagated on a transmission line 1 is connected to the connector 2 and the circuit 3 detects the carrier synchronously with a clock CK of a clock generating circuit 4. The clock CK during carrier detection is counted by a counter 5 and the result is fed to a transmission line utilizing rate calculation circuit 7. Further, the clock CK is frequency-divided by a period signal generat ing circuit 6 to generate a timing signal of a basic period T for measuring the utilizing rate, and the signal is fed to the circuit 6 together with the clock CK. Then the circuit 6 calculates easily a transmission line utilizing rate U at each basic period T and the rate is outputted to an external device from a buffer circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to transmission path control in a LAN (Local Area Network), and particularly to a transmission path usage rate measuring device for measuring the usage rate of a common transmission path.

U1 rights Conventional 1 For example, in a LAN that uses a baseband or broadband system based on C8MA (Carrier Sense Multiple Access), the use of a transmission path by multiple nodes (information processing equipment @) connected to a common transmission path No means are taken to limit the number of packets, and multiple access communication is performed using a so-called contention method in which the communication of the node that first sent a packet to the transmission path is prioritized.

However, in such a multiple access communication system in a LAN, there is a trade-off point where as the load on the common transmission path increases, the transmission efficiency according to the packet throughput characteristics and transmission delay characteristics suddenly decreases, resulting in an overload condition. It has become a thing. In addition, when the usage rate of the common transmission path increases to a certain extent, the chances of collision between packets sent from multiple nodes increase, and when a collision occurs, the bucket 1
There is a problem in that the transmission delay increases rapidly due to the retransmission of - and the transmission efficiency decreases.

In recent LANs, the number of nodes connected to the common transmission path tends to increase, so when the load increases, the use of the common transmission path is restricted and due to the reasons mentioned above. It has become necessary to suppress a decrease in transmission efficiency.

The present invention has been made in consideration of the above points, and is applicable to cases in which the use of a common transmission line is restricted depending on the load condition of the common transmission line in a 4ΔN that uses a baseband or broadband system. The present invention provides a transmission path usage rate measurement device that is optimal for

In order to achieve the object, the present invention focuses on the fact that the generation state of carriers for transmitting packets carried on a common transmission path reflects the usage status of that transmission path. Detection is performed, and the transmission path usage rate is determined from the ratio of the detected carrier occurrence time per unit time.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the transmission line utilization rate measuring device according to the present invention uses a plurality of nodes (not particularly shown) in a LAN based on a contensigon type baseband method represented by C8MA. It is connected via a connector 2 to a common transmission line 1 consisting of one connected coaxial cable, and includes a carrier detection circuit 3 that detects a carrier carrying the common transmission line 2, and generates a clock during the carrier detection period. A counter 5 that counts the tally clock CK received from the circuit 4 and its clock generation circuit 11
a 25-period generation circuit 6 that divides the clock CK from the clock CK to generate a timing signal with a basic period T for measuring the usage density of the transmission line; Transmission path usage rate calculation circuit 7 that reads the data and calculates the transmission path usage rate U for each basic period T.
and a buffer circuit 8 that reads the calculated take of the transmission path usage rate U according to the clock CK at the timing of the basic cycle T signal and transfers the transmission to an external device such as a path control device.
It is composed of. FIG. 2 shows the state of connection of the carrier detection circuit 3 to the common transmission line 1. In the figure, 11 indicates the center conductor of the coaxial cable, and 12 indicates its shield wire.

With this configuration, the carrier detection circuit 3 constantly monitors the carrier transport state on the common transmission path 1 and performs carrier detection in synchronization with the clock CK. At this time, since a Manchester code is normally used for bucket 1-, carrier detection can be performed by capturing the continuity of the signal level fluctuation. In addition, the typical waveform of the carrier carried on the common transmission line 1 consisting of a coaxial cable is shown in Figure 3, so carrier detection can be performed by capturing the level change from Ov to "1" at the start of the preamble. It is also possible to have it performed. Note that FIG. 3 shows the specifications of signals on the coaxial cable in Ethernet 1-, and II 1.
As for the II level, the nominal value on the coaxial cable at the transceiver connection is -0°225■, LL OI
The level of I is set to the same <-1,825V, and its rise time is nominally set to 25 ns. Furthermore, the detection output CD of the carrier detection circuit 3 may be delayed in time from the actual carrier transport state on the common transmission line 1, but this is not a problem here. However, if the output time of the carrier detection signal CD becomes shorter than the carrier transport time of the common transmission path 1,
It is necessary to take measures in advance to correct this in the transmission path usage rate calculation circuit 7.

When carrier detection circuit 3 detects a carrier carrying common transmission path 1]2, carrier detection signal CD is applied to counter 5, which counts clock CK while carrier detection is being performed. The carrier detection signal CD becomes a high level signal while the carrier is being detected in the carrier detection circuit 3, and continuously notifies the counter of the carrier detection state.

Further, the notification may be made intermittently, in which case the clock taken out from the carrier is sent to the counter 5.
Try to give it to

When the clock GK is running from 1 onward by the counter 5, the transmission line usage rate calculation circuit 7 is triggered by the basic cycle T signal from the periodic signal generation circuit 6. The count contents of the counter 5 at the time are read, and then the reset 1 signal R3 is given to the counter 5 to cause it to go to the reset 1. Fourth
The figure shows an example of the flow of carriers carrying the common transmission path 1 on the time axis. In the figure t 1.01t12, t
], 4.121.123 is an empty state where the common transmission path 1 is not used, and here the clock count contents for each basic period T] and T2 (T1=T2=T) by carrier detection are respectively t1]-1-t
] 3. It becomes t20+t22.

The transmission line usage rate calculation circuit 7 calculates the usage rate of the common transmission line 1 in the immediately preceding basic cycle T by dividing the read callan 1 contents by the basic cycle T.

In the case of Fig. 4, the transmission path usage rate U1 in the first basic period T1 is Ui = (t11 + t ] 3)/T, and the transmission path usage rate U2 in the subsequent basic period T2 is TJ2 =
(t20+i22)/T. Note that instead of performing the above-mentioned division process, it is also possible to subtract the numbers 1 to 1 in the counter 5 from the total number of clots during the basic period T and simply obtain the result as the transmission path usage rate. .

The data of the transmission line usage rate U calculated by the transmission line usage rate calculation circuit 7 is clocked at the timing of the basic period T.
The data is read into the buffer circuit 8 in accordance with the data, temporarily stored there, and then transferred to an external device. The external device displays the usage rate U of the common transmission path 1 at that time, for example, according to the data of the transmission path usage rate U that has been transferred, and also displays the usage rate U of the common transmission path U at that time. Transmission line 1
It is determined whether or not a predetermined threshold value is exceeded, and if the threshold value is exceeded, the use of the common transmission line is prohibited or restricted to prevent the common transmission line 1 from becoming overloaded. Transmission path control etc. will be performed as appropriate.
'In the above embodiments, we have described the case of using a bare-spant method using a coaxial cable, but when using a broadband method using a modulated frequency signal as a carrier, a filter matching the carrier frequency is used as a carrier detection circuit. and a demodulator may be used. Further, when an optical fiber cable is used as a common transmission path, carrier detection can be performed by capturing the continuity of fluctuations in the optical signal level on the transmission path using a photoelectric conversion circuit.

As described above, the transmission line utilization rate measuring device according to the present invention has the following features:
LA, which uses baseband or broadband method;
N, which is equipped with a means for detecting carriers on a common transmission path and a means for calculating the transmission path usage rate from the ratio of the generation time of the detected carriers per unit time. This configuration has an excellent advantage in that the utilization rate of the common transmission path can be easily detected.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing an embodiment of a transmission path usage rate measuring device according to the present invention, and FIG. 2 is a diagram showing a connection state of a carrier detection circuit to a common transmission path in the same embodiment.
Figure 3 is a waveform diagram of a carrier carrying a common transmission line.
FIG. 4 is a diagram showing an example of the flow of carriers on the time axis. ■... Common transmission path 2... Connector 3... Carrier detection circuit 4... Clock generation circuit 5... Counter 6... Periodic signal generation circuit 7... Transmission path usage rate calculation circuit 8...・Buffer circuit

Claims (1)

[Claims] In a LAN that uses a baseband or broadband system, there is provided a means for detecting carriers on a common transmission path and a means for calculating the transmission path usage rate from the ratio of the detected carrier generation time per unit time. A transmission line utilization measurement device configured by: