JPH05110566A - Bac bridge buffer releasing system - Google Patents

Abstract

PURPOSE:To provide an efficient MAC bridge buffer releasing system. CONSTITUTION:A frame transmitting error detecting part 10 detects a fact of failure in frame transmission in a transmitting port control part (a) 5 or (b) 7 and informs of an error. Every time an error notice is received, a transfer frame counter 11 outputs the number of frames transferred continuously by an MAC bridge counted by a counter provided in advance from the time when a last error notice is received, and also, receives a clear instruction and clears a counter value. A transmission line effective value store part 13 stores a value determined in advance. A transmission line state diagnostic part 12 compares the counter value outputted by the transfer frame counter 11 and a stored value of the transmission line effective value store part 13. In the case it is decided that the counter value is smaller than the stored value by this comparison, a buffer release control part 15 discards a frame stored in a frame buffer 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MAC bridge which connects and relays a plurality of local area networks at a data link layer, and particularly in the frame transfer processing of the MAC bridge, a new frame is transferred faster than the frame in the buffer is transferred. Is received by the MAC bridge and the frame with the transfer request is stored in the buffer.
The present invention relates to a buffer release method for discarding frames by monitoring the quality of the transmission path and the load state of the transmission path in order to prevent a large amount of frames from staying in the buffer.

[0002]

2. Description of the Related Art In a conventional MAC bridge, regardless of the state of the transmission path, all the frames staying in the buffer of the MAC bridge are individually monitored by a timer, and the frames are discarded after a certain period of time.

FIG. 2 shows an example of a conventional system, and shows an internal block of a conventional MAC bridge 16 which connects a local area network LANa17 and a local area network LANb18. A frame relay control unit receives a frame from the LANa17. The reception port control unit a19 that transfers the frame information to H.23, and the LANb
A receiving port control unit b20 that receives a frame from the frame 18 and transfers the frame information to the frame relay control unit 23;
The reception port control unit a1 discards frames related to communication closed in the Na17 and communication closed in the LANb18.
9 and the frames received from the receiving port control unit b20 are stored in the frame buffer 24, the frames to be transferred from the LANa17 to the LANb18 are read from the frame buffer 24, passed to the transmitting port control unit b22, and transferred from the LANb18 to the LANa17. Is read from the frame buffer 24 and passed to the transmission port control unit a21, and the frame received from the frame relay control unit 23 is sent to the LANa17.
To the LAN b18, a transmission port control unit a21 that transmits the frame received from the frame relay control unit 23 to the LAN b18, and a frame relay control unit 2
The frame buffer 24 stores and stores a frame retention timer for each frame received by the frame No. 3, and transfers the frame retention timer assigned to the frame to the frame existence monitoring timer 25 at regular intervals after the frame is stored.
When the frame retention timer is passed from the frame buffer 24, the frame retention timer is incremented by 1 and is passed to the frame retention time determination unit 27 to return the value to the frame buffer 24. When the frame retention time determination unit 27 requests the frame retention time determination unit 27 to store the maximum frame survival time in which frames can be retained in advance, the frame retention time determination unit 2
The maximum frame survival time storage unit 26 that transfers the maximum frame survival time to the frame 7, and the frame maximum survival time when a request is sent to the maximum survival time storage unit 26 at the same time as the newly updated frame retention timer is received from the frame survival monitoring timer 25. The frame retention time determination unit 27 that compares the time with the frame retention timer value and issues an operation instruction to the frame release control unit 28 only when the frame retention timer is greater than the frame maximum lifetime, and the frame retention time determination unit 27.
The frame release control unit 28 discards the corresponding frame retained in the frame buffer 24 from the frame buffer 24 according to the operation instruction from the frame release controller 28.

In the conventional MAC bridge according to FIG.
For all the frames captured by the AC bridge into the frame buffer 24 through the frame relay control unit 23, the frame retention timer is set when the frames are captured, and the frame retention timer is updated at regular intervals.
Every time the value of the timer is updated, it is always compared with the value of the frame maximum lifetime storage unit 26.

[0005]

In the conventional buffer releasing method described above, the MAC bridge sets a timer for displaying the time spent in the buffer in each frame to be transferred, and the MAC bridge stays in the buffer. The timer of each frame is updated at regular intervals, and the comparison between the updated timer value and a certain constant value (maximum time allowed to stay in the buffer) must be performed for each large number of frames to be relayed. However, there is a drawback in that this process requires a lot of time.

[0006]

According to a first aspect of the present invention, in a MAC bridge buffer releasing method in a MAC bridge that connects a plurality of local area networks at a data link layer, a reception for receiving the frame from each of the local area networks. Means, transmitting means for transmitting the frame to each of the local area networks, and the MA of the stored frames stored in the storage means 1 provided in advance with the received frame.
Frame relay control means for discarding the frame transmitted / received in one local area network to which the C-bridge is connected, and transferring only the frame to be transferred to another local area network via the transmitting means. Error detecting means for detecting a failure in frame transmission in the transmitting means and notifying an error,
Each time the error notification is received, the number of frames continuously transferred by the MAC bridge counted by a counter provided in advance after receiving the error notification one before is output, and the counter value is received in response to a clear instruction. Counting means for clearing, storage means 2 for storing a predetermined value, comparison means for comparing the counter value output by the counting means with the storage value of the storage means 2, and the counter value by the comparison means. Has a buffer releasing means for discarding the frame stored in the storing means 1 when it is determined that is smaller than the stored value, and a clearing means for outputting the clear instruction after the comparison by the comparing means is performed. It is characterized by

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The MA of the present invention connecting a local area network LANa2 and a local area network LANb3.
The internal block of the C bridge 1 is shown, and LANa2
A reception port control unit a4 that receives a frame from the frame and transfers the frame information to the frame relay control unit 8;
The reception port control unit b5 that receives the frame from b3 and transfers the frame information to the frame relay control unit 8 and the frames from the reception port control unit a4 and the reception port control unit b5 are stored in the frame buffer 9, and the LANa2 to the LA
The frame to be transferred to Nb3 is read from the frame buffer 9 and sent to the transmission port control unit b7, or LAN
a frame relay unit control unit 8 for reading a frame to be transferred from b3 to LANa2 from the frame buffer 9 and sending it to the transmission port control unit a6, and for discarding frames related to communication closed in LANa2 and communication closed in LANb3; A transmission port control unit a6 for transmitting the frame received from the frame relay control unit 8 to the LAN a2,
The frame received from the frame relay control unit 8 is sent to the LAN
The transmission port control unit b7 that transmits to b3, the frame buffer 9 that stores the frame received by the frame relay control unit 8, and the transmission port control unit a6 or the transmission port control unit b7 detects that the frame transmission has failed, A frame transmission error detection unit 10 that notifies the transfer frame counter 11 that there is a transmission failure, and a frame that the MAC bridge continuously transmits from the notification that the frame transmission error detection unit 10 has detected a frame transmission failure. After counting the number and passing the count value until the frame transmission failure of the next transmission port to the transmission path state diagnosis unit 12, the count value is set to 0 upon receiving an instruction from the statistical value clear control unit 14.
A transfer frame counter 11 that clears and then counts the number of frame transfers until the frame transmission error detection unit 10 receives a frame transmission failure notification again, and a transmission path valid preset as a reference value in the MAC bridge The transmission path effective value storage unit 13 for storing the value, and when the transfer frame counter 11 notifies the transfer frame count value, the transmission path effective value stored in the transmission path effective value storage unit 13 is read to After comparing the count value and the transmission path effective value, unconditionally issuing an operation instruction to the statistical value clear control unit 14 and at the same time, if the count value of the transfer frame is smaller than the transmission path effective value, the buffer release control unit The transmission line state diagnosis unit 12 which issues an operation instruction to the transmission line 15, and the transfer frame counter based on the operation instruction from the transmission line state diagnosis unit 12. And statistics clear control unit 14 issues a 0 clear instruction to coater 11, a buffer release controller 15 for discarding the entire frame remaining in the buffer 9 by the operation instruction from the transmission path condition diagnosis unit 12.

In the MAC bridge of the present invention according to FIG. 1,
In the frame transfer process of the MAC bridge, the frame transmission process is successful without the retransmission process until the frame transmission error detection unit 10 detects the transmission error and the next transmission error is detected. On the other hand, no processing is required, frame transmission fails, and when the frame transmission error detection unit 10 detects a transmission failure, the transfer frame counter 11 starts counting the number of transfer frames. After that, while the transfer process is successful, the process of counting the number of transfer successful frames by the transfer frame counter 11 is continued. When the rate of transmission failure increases due to poor quality of the transmission path or the load of the transmission path is extremely high, and the processing such as retransmission is frequently performed, the frequency of transmission failure detection by the frame error detection unit 10 becomes high. Therefore, the number of successful frame transmissions decreases after a frame transmission failure before the next transmission failure, and the value of the transfer frame counter 11 decreases. Only when this value becomes smaller than the value stored in the transmission path effective value storage unit 13, the frames accumulated in the frame buffer 9 are discarded as described above.

[0010]

As described above, according to the present invention,
In the frame transfer process of the MAC bridge, the frame accumulated in the buffer of the MAC bridge is released only when the number of times the frame transfer process succeeds such as when the quality of the transmission path is bad or the load is extremely high is extremely reduced. Since there is no need to individually update and monitor the frame retention timer for all the frames transferred by, the load on the MAC bridge is reduced, and a higher performance MAC bridge can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional example.

[Explanation of symbols]

 1 MAC Bridge of the Present Invention 2,17 LANa 3,18 LANb 4,19 Reception Port Control Unit a 5,20 Reception Port Control Unit b 6,21 Transmission Port Control Unit a 7,22 Transmission Port Control Unit b 8,23 Frame Relay control unit 9 Frame buffer 10 Frame transmission error detection unit 11 Transfer frame counter 12 Transmission line status diagnosis unit 13 Transmission line effective value storage unit 14 Statistic value clear control unit 15 Buffer release control unit 16 Conventional MAC bridge 24 Frame buffer 25 frames Survival monitoring timer 26 Maximum frame survival time storage unit 27 Frame retention time determination unit 28 Frame release control unit

Claims (1)

[Claims] 1. A MAC in a MAC bridge that connects a plurality of local area networks at a data link layer.
In the bridge buffer release system, a receiving unit that receives the frame from each of the local area networks, a transmitting unit that transmits the frame to each of the local area networks, and a storage unit 1 that includes the received frame in advance. Among the stored and stored frames, only the frame to be transmitted and received in one local area network to which the MAC bridge is connected and to be transferred to another local area network is transmitted via the transmitting means. A frame relay control unit that performs a transfer process, an error detection unit that detects that the frame transmission in the transmission unit has failed, and notifies an error, and 1 each time the error notification is received.
Counting means for outputting the number of frames continuously transferred by the MAC bridge counted by a counter provided in advance after receiving the previous error notification and receiving a clear instruction to clear the counter value; The storage means 2 for storing the stored value, the comparison means for comparing the counter value output by the counting means with the storage value of the storage means 2, and the counter value being smaller than the storage value by the comparison means. M has a buffer releasing means for discarding the frame stored in the storage means 1 when it is determined, and a clearing means for outputting the clear instruction after the comparison by the comparing means is performed.
AC bridge buffer release method.