JP2000106571A - Bridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the bridge where aborted packet data from a specific transfer source can be reduced. SOLUTION: The bridge is provided with a network interface 1 that connects to a LAN, a backbone bus interface 2 that connects to a backbone bus K, a reception buffer memory 3 that stores packet data received from the network interface 1, an address discrimination section 4 that extracts a destination address from the packet data stored in the reception buffer memory 3 to discriminate a LAN port (bridge circuit) of a transfer destination, a transmission buffer memory 6 that stores the packet data received from the backbone bus interface 2 and has a specific memory area 5 to store packet data from a transfer source whose aborted packet data are desirably to be controlled, and a buffer management section 7 that informs the transfer source of an address of the specific memory area 5 when a transfer request of packet data from a transfer source whose aborted packet data are desirably controlled and allows the specific memory area 5 to transfer packet data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bridge device, and more particularly to a bridge device capable of reducing discard of packet data from a specific transfer source.

[0002]

2. Description of the Related Art Generally, a bridge device is a LAN (Local
Area Network). FIG.
FIG. 2 is a block diagram showing the internal structure of a conventional bridge device. In FIG. 6, A, B, C... Are bridge circuit units each having a network interface 20 and a backbone bus interface 21, and are connected between the bridge circuit units A, B, C. Transmission and reception of packet data are performed. X is a device management unit that transmits and receives packet data to and from the bridge circuit units A, B, C,... The device management unit X is generally composed of a CPU circuit block.

[0003] There are roughly two types of packet data transmitted or received by the above-mentioned bridge device to or from an external network such as Ethernet or ATM (Asynchronous Transfer Mode). One is relay packet data exchanged between an external terminal and another external terminal, and is relayed from one LAN to the other LAN without going through the device management unit X. Another one is a device management unit X
Are packet data transmitted / received to / from the LAN, and are exchanged in order for the bridge device to function as one network terminal. For the latter, the device management unit X
Is required, for example, to perform the following processing. (1) Support of a network protocol specific to a bridge device By using STP (Spanning Tree Protocol) or the like, network route information in a form in which a plurality of bridge devices are connected is exchanged between the bridge devices, and network loop detection and route change are performed. Can be performed. (2) Support of network management function By using SNMP (Simple Network Management Protocol) or the like, unique information (for example, network address information, various statistical information) of the bridge device is collected from an external management terminal, and operation parameters are set. Etc. can be performed. (3) Other higher-level protocols (Telnet, FTP
Support) Remote login to the bridge device, file transfer, etc. are possible. (4) Support for ATM-specific protocols Signaling exchanged with external ATM devices (Signal
The ling) protocol, the bridge protocol, and the like allow the bridge device to operate as one ATM client in the ATM network.

In order to perform these upper layer protocols in the bridge device, it is necessary for the device management unit X to terminate packet data received from the LAN and transmit the packet data to the LAN.

FIG. 7 is a block diagram showing a configuration in a bridge circuit section of a conventional bridge device. As shown in FIG. 7, each bridge circuit unit includes a network interface 20 connected to the LAN, a main bus interface 21 connected to the main bus K, and a reception buffer for storing packet data received from the network interface 20. Memory 23 and reception buffer memory 23
An address determination unit 24 that extracts a destination address from the packet data stored in the storage device and determines the destination LAN port (bridge circuit unit), and a transmission buffer memory 25 that stores the packet data received from the backbone bus interface 21 And

Next, the operation of the conventional bridge device will be described with an example in which packet data is transferred (bridge relay) from the bridge circuit section B to the bridge circuit section A.

[0007] The packet data received from the network interface 20 of the bridge circuit unit B is temporarily stored in the reception buffer memory 23.

[0008] The address determination unit 24 extracts a destination address from the packet data stored in the reception buffer memory 23, and determines a LAN port to be a transfer destination. For example, it is determined that the packet data is to be transferred to the bridge circuit unit A.

The bridge circuit section B includes a reception buffer memory 2
3 is transferred to the bridge circuit unit A, which is the destination, via the trunk bus interface 21.

The transfer destination bridge circuit section A sequentially stores the packet data received from the main bus K in the transmission buffer memory 25 via the main bus interface 21.

Thereafter, after performing processing such as error checking of transmission data and establishment of a transmission procedure to the network interface 20, the network interface 20
Starts transmission to the LAN via.

[0012]

In the conventional bridge circuit, an overflow occurs when data exceeding the capacity of the transmission buffer memory at the transfer destination is sent from the transfer source. In this case, the packet data is discarded by the bridge circuit unit B of the transfer source or the bridge circuit unit A of the transfer destination, and is not transmitted to the transfer destination LAN.

For example, while a bridge operation is being performed at an interface between LANs having the same line speed, packet data is not discarded unless there is a condition that a transfer destination network interface is crowded and transmission cannot be performed. do not do. However, when the bridge from the bridge circuit section C to the bridge circuit section A occurs simultaneously with the bridge from the bridge circuit section B to the bridge circuit section A, or the line speed of the bridge circuit section B is If it is lower, the transmission buffer memory of the bridge circuit unit A overflows, so that data cannot be written from the transfer source. As a result, packet data is discarded.

As discarding packet data which is a problem,
For example, there are the following cases. The bridge device transmits packet data to an arbitrary LAN port, or transmits packet data to an arbitrary LAN port in order to transfer packet data between a plurality of LAN ports transparently and to support protocols such as STP and SNMP. Is required to receive packet data addressed to the device from the LAN port. When the LAN port is an ATM, a function of transmitting and receiving ATM specific packet data to and from an ATM switch in accordance with a signaling protocol is required. These bridge devices themselves are LAN
The lack of packet data exchanged between ports can affect the device itself or the network to which the device is connected, so it is distinguished from packet data relayed between ports, and priorities are set and discarded. It is preferable to suppress as much as possible.

However, in the conventional bridge circuit, packet data may be randomly discarded depending on the transmission state of the buffer at that time. For example, while the bridge operation from the bridge circuit unit B to the bridge circuit unit A is being performed,
Assuming that a request to transfer packet data from the device management unit X to the bridge circuit unit A occurs to support the protocol, the packet data from the device management unit X is discarded regardless of the transmission source.

Therefore, it is difficult for a conventional bridge device to prevent the discarding of specific packet data whose suppression is to be suppressed, such as the packet data from the device management unit X.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a bridge device capable of reducing discard of packet data from a specific transfer source.

[0018]

A bridge device according to the present invention has a plurality of bridge circuit units having a network interface and a device management unit for performing network management and the like. In a bridge device that transfers packet data to and from a device management unit, a buffer memory having a specific memory area for storing transferred packet data and storing packet data from a transfer source whose discarding is to be suppressed. And a buffer management unit that, when there is a packet data transfer request from a transfer source that wants to suppress discarding, notifies the transfer source address of the specific memory area of the buffer memory and transfers the packet data to the specific memory area. And having the following.

When there is a free space in a memory area other than the specific memory area when there is a packet data transfer request from the transfer source which does not need to suppress the discard, the address of the memory area is notified to the transfer source. If the memory area other than the specific memory area overflows, the transfer source is notified that the transfer of the packet data is not permitted, and the transfer of the packet data at the transfer source is performed. It is preferable to cause discard or retransmission.

An identification code is assigned to each of the bridge circuit unit and the device management unit. The identification code of the transfer source is sent to the transfer destination simultaneously with the transfer request, and the bridge of the transfer source is transmitted based on the sent identification code of the transfer source. A main bus interface for identifying a circuit unit or a device management unit may be provided.

The specific memory area may be fixedly reserved. In that case, they may be allocated continuously or discontinuously.

Further, the specific memory area may be variably controlled.

It is preferable to have a specific memory area used for storing packet data from the device management unit.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration inside a bridge circuit unit of the bridge device of the present invention.

As shown in FIG. 1, the bridge circuit section of the bridge device according to the present invention includes, for example, a network interface 1 connected to a LAN, a main bus interface 2 connected to a main bus K, and a network interface 1. A receiving buffer memory 3 for storing the received packet data, an address determining unit 4 for extracting a destination address from the packet data stored in the receiving buffer memory 3 and determining a destination LAN port (bridge circuit); A transmission buffer memory 6 having a specific memory area 5 for storing packet data received from the trunk bus interface 2 and storing packet data from a transfer source whose discard is to be suppressed; If there is a request to transfer the packet data of The address of a specific memory area 5 of the receive buffer memory 6 notifies the transfer source, the buffer management unit 7 to perform the transfer of packet data to a specific memory area 5,
Having.

Further, in the bridge device of the present invention, an identification code (ID) is given to each of the bridge circuit units A, B, C... And the device management unit X. The backbone bus interface 2 has a function of transmitting an identification code of its own transfer source to a transfer destination simultaneously with a transfer request when the transfer source is used. The transfer source bridge circuit units A, B, C,.
Alternatively, it has a function of identifying the device management unit X and notifying the buffer management unit 7 of this.

FIG. 2 is a sequence diagram for explaining a flow until packet data is transferred. First, the transfer source main bus interface 2 issues a transfer request prior to packet data transfer and, at the same time, notifies its own identification code to the transfer destination main bus interface 2 (L1). The transfer destination backbone bus interface 2 identifies the transfer source bridge circuit units A, B, C... Or the device management unit X based on the transmitted transfer source identification code.

Next, when the transfer destination buffer management unit 7 requests the transfer of packet data from the transfer source that wants to suppress the discarding of the device management unit X or the like, the buffer management unit 7 stores the specific memory area 5 of the transmission buffer memory 6. The address is notified to the transfer source via the board bus interface 2 (L2).

The buffer management unit 7 notifies the address of the unspecified memory area 8 when there is a packet data transfer request from a transfer source that does not need to suppress discarding.
When the unspecified memory area 8 overflows, the transfer source is notified that the transfer of the packet data is not permitted, that is, a message indicating a request to discard or retransmit the packet data at the transfer source is returned. It is preferable to be able to

Next, the transfer source transfers the packet data to the specific memory area 5 of the transfer destination (L3),
Alternatively, the packet data is discarded or the transfer is postponed, and a transfer request is sent again.

According to the present invention, packet data from a transfer source whose discard is to be suppressed is preferentially stored in the specific memory area 5 of the buffer memory, so that discard of packet data from a specific transfer source can be reduced. Can be.

FIG. 3 is an explanatory diagram showing the specific memory area 5 of the transmission buffer memory 6. As shown in FIG. 3, a memory area of the transmission buffer memory 6 is a specific memory area 5 used for storing packet data from the apparatus management unit X.
And an unspecified memory area 8 used for storing packet data from other transfer sources.

The specific memory area 5 stores the address A1
To An. A memory slot for one bucket is separated by a dotted line in FIG. 3. For example, a maximum length of 1518 bytes of the Ethernet frame is defined to be included in one slot. That is, the head addresses A1, A2, A3,... An of each slot are fixedly allocated.

In response to the transfer request from the transfer source, the buffer management unit 7 at the transfer destination sequentially returns the fixedly allocated head address to the transfer source. For example, the addresses are sequentially added by the slot size, and for example, A3 is returned for the third transfer request, and when the address reaches An, A1 is returned.
Return to Since the buffer management unit 7 only needs to calculate the addition of the buffer ID (the head address of each slot) and determine whether the last slot of the buffer area has been reached,
The configuration of the transmission buffer memory 6 is very simple.

In the example shown in FIG. 3, the specific memory area 5 is continuously allocated. However, depending on the application, a continuous space cannot be ensured due to a memory space map for another use. In such a case, for example, as shown in FIG. 4A, there is a method of allocating the specific memory area 5 discontinuously.

In this method, a descriptor table 9 as shown in FIG. 4B is used separately from a buffer memory area. The descriptor table 9 is a data block in which information such as a buffer pointer address and a slot size is stored. The buffer management unit 7 sequentially refers to the descriptor table 9 corresponding to each transfer request,
The buffer addresses A1, A2, A3,... An stored in the descriptor table 9 are sequentially transferred.

If the slot size is fixed to the maximum packet length, the efficiency of memory usage when transferring short packet data is reduced. Therefore, for example, a plurality of types of slot sizes are provided (for example, three types of short, medium, and long), and a descriptor table 9 corresponding to each is provided, and the buffer management unit 7 sets the transfer packet size indicated in each transfer request message. Accordingly, the descriptor table 9 to be referred to may be selected.

In the examples shown in FIGS. 3 and 4, the specific memory area 5 is fixedly secured in the transmission buffer memory 6, but when the number of transfers from a specific transfer source is small, the memory area is changed. It cannot be used effectively. Therefore, there is a method of variably controlling the specific memory area 5.

In this method, as shown in FIG. 5, the transmission buffer memory 6 is configured as a ring buffer, and the transfer address is returned to the transmission source sequentially from the buffer head. Return buffer address is threshold (threshol
d) When the branch point indicated by 10 is reached, return to the top,
The area after the threshold 10 is not used.

The setting of the threshold 10 is automatically changed according to predetermined conditions. For example, in the initial setting value, the size of the specific memory area 5 for the device management unit X is reduced, and the size of the specific memory area 5 is increased by reducing the address of the threshold 10 in the following cases. I do. (1) When the device management unit X detects that the transfer frequency of its own transfer packet increases, for example, an ATM signaling packet, LANE (LA
N Emulation) Control packets and the like tend to increase when there is a change in the configuration information of the ATM network, such as when an ATM connection is newly established, but this period can be detected by the device management unit X, so that the setting can be changed. It is. (2) When the Specific Memory Area 5 for the Device Management Unit X is Depleted The depletion is detected by the buffer management unit 7. The buffer management unit 7 sequentially returns the address (buffer pointer) to the transfer source, but confirms that the buffer slot is empty before returning. For the confirmation, a buffer slot is provided with an identification flag indicating whether the data currently stored in the buffer slot has been transmitted or not transmitted. Is not transmitted, it can be detected that the specific memory area 5 is depleted.

In the control of the ring buffer, a read pointer (the latest address at which the transfer is completed) and a write pointer (the latest address returned to the transmission source) are managed, and even if the threshold 10 is dynamically set. If the control for returning the write pointer to the head is appropriately performed, no inconsistency occurs.

The present invention is not limited to the above embodiment, and various changes can be made within the scope of the technical matters described in the claims. For example, two or more specific memory areas 5 may be provided in one buffer memory. Further, the bridge device of the present invention is a WAN (Wide A
rea Network).

[0043]

According to the present invention, packet data from a transfer source whose discard is to be suppressed is preferentially stored in a specific memory area of a buffer memory, so that discard of packet data from a specific transfer source is reduced. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration inside a bridge circuit unit of a bridge device of the present invention.

FIG. 2 is a sequence diagram for explaining a flow until packet data is transmitted.

FIG. 3 is an explanatory diagram showing an example in which a specific memory area is fixedly allocated and continuously allocated.

FIG. 4 is an explanatory diagram showing an example in which a specific memory area is fixedly allocated and allocated discontinuously.

FIG. 5 is an explanatory diagram showing an example in which a specific memory area is variably controlled.

FIG. 6 is a block diagram showing the internal structure of a conventional bridge device.

FIG. 7 is a block diagram showing a configuration inside a bridge circuit unit of a conventional bridge device.

[Explanation of symbols]

 1: Network interface 2: Backbone bus interface 3: Receive buffer memory 4: Address determination unit 5: Specific memory area 6: Transmission buffer memory 7: Buffer management unit 8: Unspecified memory area 9: Descriptor table 10: Threshold

Claims (8)

[Claims] A plurality of bridge circuit units each having a network interface; and a device management unit for performing network management and the like, wherein packet data is transmitted between the bridge circuit units and between the bridge circuit unit and the device management unit. A buffer device that has a specific memory area for storing the packet data from the transfer source that wants to suppress discarding, and a buffer device that has a specific memory area to store the transferred packet data, A buffer management unit that, when a packet data transfer request is issued, notifies a transfer source of an address of a specific memory area of the buffer memory and transfers packet data to the specific memory area. And a bridge device. 2. When there is a packet data transfer request from a transfer source that does not need to suppress discarding, if there is free space in a memory area other than the specific memory area, the address of the memory area is changed to the transfer source. Inform the transfer of the packet data to the memory area, if the memory area other than the specific memory area overflows, notify the transfer source that the transfer of the packet data is not allowed,
2. The bridge device according to claim 1, wherein packet data is discarded or retransmitted at a transfer source. 3. An identification code is assigned to each of the bridge circuit unit and the device management unit. The identification code of the transfer source is transmitted to the transfer destination simultaneously with the transfer request, and the transfer source is identified based on the transmitted identification code of the transfer source. The bridge device according to claim 1, further comprising a backbone bus interface for identifying the bridge circuit unit or the device management unit. 4. The bridge device according to claim 1, wherein the specific memory area is fixedly secured. 5. The bridge device according to claim 4, wherein the specific memory area is continuously allocated. 6. The bridge device according to claim 4, wherein said specific memory area is allocated discontinuously. 7. The bridge device according to claim 1, wherein the specific memory area is variably controlled. 8. The bridge device according to claim 1, further comprising the specific memory area used for storing packet data from the device management unit.