JP3111543B2 - MAC bridge buffer release method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MAC bridge for connecting and relaying a plurality of local area networks at a data link layer, and in particular, in a frame transfer process of a MAC bridge, a new frame is transferred earlier than a frame in a 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 monitoring the quality of a transmission path and the load state of the transmission path and discarding frames in order to prevent a large amount of frames from staying in a buffer.

[0002]

2. Description of the Related Art In a conventional MAC bridge, regardless of the state of a transmission line, all frames staying in a 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 for connecting a local area network LANa17 and a local area network LANb18. 23, a receiving port control unit a19 for transferring frame information to
A receiving port control unit b20 that receives a frame from the LAN 18 and transfers frame information to the frame relay control unit 23;
The reception port control unit a1 discards the frames related to the communication closed in the Na17 and the communication closed in the LANb18, and
9 and the frame received from the reception port control unit b20 are stored in the frame buffer 24, and the frame to be transferred from the LANa17 to the LANb18 is read out from the frame buffer 24 and passed to the transmission port control unit b22 and the frame to be transferred from the LANb18 to the LANa17. Relay unit control unit 23 which reads out the frame buffer 24 from the frame buffer 24 and passes it to the transmission port control unit a21, and transmits the frame received from the frame relay control unit 23 to the LANa 17
A transmission port control unit a21 that transmits a frame received from the frame relay control unit 23 to the LANb 18, a transmission port control unit b22 that transmits a frame received from the frame relay control unit 23, and a frame relay control unit 2
3. A frame buffer 24 that assigns and stores a frame retention timer for each received frame and transfers the frame retention timer assigned to the frame to the frame survival 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 one, passed to the frame retention time determination unit 27, and the value is returned to the frame buffer 24. The maximum frame survival time in which a frame can stay is stored in advance, and when requested by the frame stay time determination unit 27, the frame stay time determination unit 2
7, a frame maximum survival time storage unit 26 that passes the maximum frame life time to the frame maximum reception unit 26, and a frame maximum survival time frame that receives a newly updated frame retention timer from the frame survival monitoring timer 25 and simultaneously issues a request to the maximum survival time storage unit 26 The frame residence time determining unit 27 compares the time with the frame residence timer value, and issues an operation instruction to the frame release control unit 28 only when the frame residence timer is larger than the frame maximum lifetime.
The frame release control unit 28 discards the corresponding frame staying in the frame buffer 24 from the frame buffer 24 in accordance with the operation instruction from.

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

[0005]

In the above-described conventional buffer release method, the MAC bridge sets a timer for indicating the time spent in the buffer for each frame to be transferred, and stores the time in the buffer. Update of the timer of each frame at a fixed time interval, and comparison of the updated timer value with a certain fixed value (the maximum time allowed to stay in the buffer) must be performed for each large number of frames relayed. In addition, there is a disadvantage that this process requires a long time.

[0006]

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

[0007]

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 for connecting a local area network LANa2 and a local area network LANb3 is shown.
3 shows an internal block of the C bridge 1;
A receiving port control unit a4 that receives a frame from the LAN and transfers the frame information to the frame relay control unit 8;
b3, which receives the frame from b3 and transfers the frame information to the frame relay control unit 8, and stores the frames from the reception port control unit a4 and the reception port control unit b5 in the frame buffer 9;
The frame to be transferred to Nb3 is read from the frame buffer 9 and sent to the transmission port control unit b7, or
a frame relay unit control unit 8 that reads a frame to be transferred from b3 to LANa2 from the frame buffer 9 and sends the frame to the transmission port control unit a6 and discards a frame related to communication closed in LANa2 and communication closed in LANb3; A transmission port control unit a6 for transmitting a frame received from the frame relay control unit 8 to the LANa2,
The frame received from the frame relay control unit 8 is sent to the LAN
b3, a frame buffer 9 for storing a frame received by the frame relay control unit 8, and a detection that the transmission port control unit a6 or the transmission port control unit b7 has failed in frame transmission, A frame transmission error detecting unit 10 for notifying the transfer frame counter 11 that there has been a transmission failure, and a frame continuously transmitted by the MAC bridge from the notification of the detection of the frame transmission failure from the frame transmission error detecting unit 10. After the number is counted and the count value until the frame transmission failure of the next transmission port is passed to the transmission path state diagnostic unit 12, the count value is set to 0 upon receiving an instruction from the statistical value clear control unit 14.
Clear, and again a transfer frame counter 11 for counting the number of frame transfers until a frame transmission failure notification is received from the frame transmission error detection unit 10; and a transmission line validity preset as a reference value in the MAC bridge. When the transfer frame counter 11 is notified of the transfer frame count value from the transfer frame effective value storage unit 13 that stores the transfer frame effective value, the transmission line effective value stored in the transfer line effective value storage unit 13 is read. After comparing the count value with the transmission path effective value, an operation instruction is unconditionally issued 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 15 for transmitting an operation instruction to the transmission frame counter 15; 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 according to the invention according to FIG.
In the frame transfer process of the MAC bridge, the frame transmission process succeeds without retransmission process until the frame transmission error detection unit 10 detects a transmission error and then detects a transmission error. No processing is required, the frame transmission fails, and the transfer frame counter 11 starts counting the number of transfer frames only when the frame transmission error detection unit 10 detects the transmission failure. Thereafter, as long as the transfer process is successful, the process of counting the number of successfully transferred frames by the transfer frame counter 11 is continued. If the quality of the transmission path is poor or the load on the transmission path is extremely high, the rate of transmission failures increases, and if processing such as retransmission is performed frequently, the frequency of transmission failure detection by the frame error detection unit 10 increases. Therefore, the number of successful frame transmissions before the next transmission failure after the frame transmission failure decreases, 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 staying in the frame buffer 9 are discarded as described above.

[0010]

As described above, according to the present invention,
In the frame transfer processing of the MAC bridge, the MAC bridge is released by releasing the frames staying in the buffer of the MAC bridge only when the number of times the frame transfer processing is successful such as when the quality of the transmission path is poor or the load is extremely low is extremely reduced. It is not necessary to update and monitor the frame retention timer for every frame to be transferred for each frame, thereby reducing the load on the MAC bridge and providing a higher-performance MAC bridge.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one 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 Receiving Port Control Unit a 5, 20, Receiving 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 path state diagnosis unit 13 Transmission path effective value storage unit 14 Statistical value clear control unit 15 Buffer release control unit 16 Conventional MAC bridge 24 Frame buffer 25 frames Survival monitoring timer 26 Frame maximum survival time storage unit 27 Frame residence time determination unit 28 Frame release control unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-58142 (JP, A) JP-A-64-78051 (JP, A) JP-A-2-46033 (JP, A) JP-A-3-58 10532 (JP, A) JP-A-4-199941 (JP, A) IEICE Technical Report, Vol. 89 No. 361, IN89-77, Takashi Ikegawa et al., "Dynamic Flow Control for Congestion Control," pages. 13-18 (58) Fields investigated (Int. Cl. ⁷ , DB name) G06F 13/00 H04L 12/28 H04L 29/00 WPI (DIALOG)

Claims (1)

(57) [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 method, 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 has the received frame in advance Of the stored and stored frames, only the frames to be transmitted / received within one local area network connected to the MAC bridge and to be transferred to another local area network are transmitted via the transmitting means. Frame relay control means for performing a transfer process, error detection means for detecting that the transmission means has failed in frame transmission and providing an error notification, and 1 every 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 for receiving a clear instruction to clear the counter value; Storage means 2 for storing the obtained value, comparison means for comparing the counter value output by the counting means with the storage value of the storage means 2, if the counter value is smaller than the storage value by the comparison means. M, characterized by having a buffer releasing means for discarding the frame stored in said storage means 1 when determined, and a clearing means for outputting said clear instruction after the comparison by said comparing means.
AC bridge buffer release method.