JPS61224535A - Simulator of colliding state - Google Patents

Abstract

PURPOSE:To simulate colliding state under actual environment without changing the characteristic of a transmission line and a transceiver by sending immediately a collision generating signal for a prescribed time on a transmission line after detection of a packet and controlling the signal with external designation. CONSTITUTION:A packet detection circuit 1 inputs a reception signal from a transceiver to detect the transmission of a packet on the transmission line. This function is a carrier sense function being one of basic function of the carrier sense multiple access/collision detect (CSMA/CD) system, it is realized by the level detection of an input signal and the level is at binary '1' when the packet is received and the level is at binary '0' when no packet is received. The output of the packet detection circuit 1 is inputted to a collision state generation control circuit 2 and an AND circuit 3. The circuit 2 changes the output to binary '0' or binary '1' according to an external program every time the output is changed from binary '1' to binary '0', and when the circuit 1 detects the packet end.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a testing device for a CSMA/CD type packet communication system, and in particular for checking the normality of collision detection and retransmission mechanisms in the network access functions of nodes. Conventionally, this type of collision simulation test involves removing the terminating resistor of the coaxial transmission line and using reflected waves to simulate a collision, or testing the detection level of the collision detection circuit. Instead, a method was used in which the transmission line or transceiver was modified to generate a collision signal even though no collision had actually occurred.

(Problems to be Solved by the Invention) The conventional collision state simulation method described above uses a method of changing the collision detection characteristics of the transmission line and transceiver, so it has the disadvantage that it cannot be tested under normal usage conditions. There is. Also, it is difficult to dynamically change the state in which a collision occurs and the state in which it does not occur.

The drawback is that it cannot simulate the actual operating conditions.

It is therefore an object of the present invention to overcome these drawbacks and to
It is an object of the present invention to provide a collision state simulation method that can simulate a collision state in a real environment without changing the characteristics of a transmission path or a transceiver, and can also cause a collision state under arbitrary conditions.

(Means for Solving the Problems) The collision state simulating device of the present invention has 1 means connected to a node-side interface of a transceiver in a normal system and detecting that a packet has been transmitted on a transmission path;
Collision signal sending means sends out a collision occurrence signal for a certain period of time on the transmission path immediately after detecting the packet in order to cause a collision in response to the packet transmission; The apparatus is configured to include a determining means for controlling the transmission according to the probability and the transmission a certain number of times in succession.

(Example) Next, the present invention will be explained with reference to the drawings.

The drawing is a block diagram of one embodiment of the present invention.

The packet detection circuit 1 receives a received signal from a transceiver and detects that a packet has been transmitted on a transmission path. This function is a carrier sense function, which is one of the basic functions of the CSMA/CD system, and is realized by detecting the level of the input signal. The output of the packet detection circuit 1 is sent to the collision state generation control circuit 2 and A
It is input to the ND circuit 3. The collision state occurrence control circuit 2 is
Each time the packet detection circuit 1 detects the end of a packet and changes the output from binary "'1" to binary '0, it changes the output to binary "0" or binary °1 according to an external program. change.

Next, an embodiment of the 5gE sudden condition generation control circuit 2 will be described below. One embodiment is a circuit using a shift register having n (n≧1) pits and in which the initial value of each bit can be set. The output of the packet detection circuit 1 is input as the shift clock of this shift register, and the shift is caused by a change from binary '°1' to binary 'O', and the output of the final stage in the shift direction of the shift register is caused to be in a collision state. This is the output of control circuit 2. At the beginning I'(k(
The initial value of the second bit of the shift register determines whether or not to cause a collision for the packet transmitted 1≦≦n times (binary ``'1'' to cause a collision, 2 to not cause a collision)
After setting, by starting the wooden fM, the data is shifted every time the packet end is detected, and when the k-th packet is detected, the value set for the bit is used as the collision state generation control. Output to the output end of the circuit, A
When a trap input is input to the input end of the ND circuit 3 and the set value of the k-th bit is binary "1", the output value of the packet detection circuit 1 is output to the output end of the AND circuit 3, and the set value of the k-th bit is 2
If the leading bit is "0", the output of the packet detection circuit 1 is masked by the AND circuit 3Vc. The output of the AND circuit 3 is input to a collision occurrence signal transmission circuit 4Vc. The collision generation signal sending circuit 4 is activated by a human-powered change from binary ``0#'' to binary ``pa1#'', causes a collision, and transmits a pseudo-1 packet for a sufficient time to prevent the other sending node from detecting it. By the above-described operation, the device of the present invention causes a collision state for any number (where 1≦and≦n) packet transmission.

Next, another embodiment of the collision state generation control circuit 2 will be described. This embodiment is a collision state generation control circuit that outputs binary ``1#'' with a probability of l(/n (n≧1.1≦≦n), and outputs binary ``o'' at (n-k)/. '
This is a circuit that uses a circuit that outputs i.

This circuit uses a modulo n random number generation circuit and compares the output random number with the set value, and when the random number is smaller than k, it is converted into binary ``
This is realized by a comparator circuit that outputs ``1'' and outputs binary ``0'' when the random number is greater than or equal to .

In this embodiment, a collision occurs with respect to packet transmission with a probability of /n. Here, two embodiments of the collision state generation control circuit 2 have been described, but in the present invention, by realizing a collision state generation control circuit having the above-mentioned functions, the collision state generation control circuit 2 can be operated according to various conditions. It is possible and possible for a collision to occur.

(Effects of the Invention) As explained above, the present invention has the effect that a collision state can be simulated in a real environment without changing the transmission path or the characteristics of the transceiver because it is connected to a transceiver and used, and that it is possible to simulate an arbitrary number of transmissions. This has the effect that a collision state can occur under various conditions such as packets and probabilities.

[Brief explanation of drawings]

The drawing is a block diagram of the invention. 1...Packet detection circuit, 2...Collision state occurrence control circuit. 3...AND circuit, 4... Signal sending circuit for collision occurrence.

Claims (1)

[Claims] In a collision state simulating device used to confirm the normality of the collision detection function and retransmission function of a node device connected to a CSMA/CD type packet communication system,
a packet detection means for detecting packet transmission on a transmission path from a received signal from a transceiver; and a packet detection means that is activated by the output of the packet detection means and detects whether or not a collision state is caused for the packet detection when a packet is detected. A collision state simulating device comprising: a determining means for determining according to a specification; and a collision signal transmitting means for transmitting a signal to cause a collision on a transmission path in accordance with an output from the determining means.