JP2000183966A - Packet transfer system with precedence of switch in lan system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure real time characteristics (communication quality) of a packet by defining a precedence based on necessity/unnecessity of the real time property in the packet, sorting competing packets according to whether they are transferred to an exit or stored in a buffer, setting transmission rate of the packets when they are stored and transferring the packets with high precedence to the exit according to the transmission rate. SOLUTION: When inputted packets arrive, it is discriminated whether they are the packet with high precedence for which the real time property is required or not and discrimination is notified to a control part 13 by packet decision parts 8, 9, 10, 11. The packets inputted in the packet decision parts 8, 9, 10, 11 are sorted to desired competition control parts 15, 16, 17, 18 by a switching part 12. When no competition occurs in the competition control parts 15, 16, 17, 18 and no packet is stored in a common buffer 14, the packets are transferred to the exit. When the competition is generated, the packets with high precedence are transferred to the exit and the packets with low precedence are stored in the common buffer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet transfer system in which a packet is relayed by using a switch in a LAN, and in particular, guarantees the real-time performance of packets requiring real-time performance and requires real-time performance. The present invention relates to a prioritized packet transfer system of a switch in a LAN system for reducing delay of a packet not to be transmitted.

[0002]

2. Description of the Related Art Generally, in a computer network, information is transmitted in units of packets. A switch is known as a device for transferring an input packet to an appropriate outlet for relaying the packet.

FIG. 3 shows a conventional packet transfer mechanism of a switch. Packets arriving at the switch unit 1 and competing at an exit (not shown) are stored in the buffer 2 in the order of arrival. The packets have no priority, and are sequentially transferred to the exit from the packet stored in the buffer 2 in order.

FIG. 4 shows a packet transfer mechanism of another switch. Packets have priority,
Packets competing in the switch unit 3 are stored in different buffers 4 and 5 depending on the priority. Higher priority packets are stored in the buffer 4, and lower priority packets are stored in the buffer 5. The control unit 7 instructs the switch unit 6 to transfer the packets stored in the buffers 4 and 5 to the egress. At this time, until all the packets accumulated in the buffer 4 are transferred, the buffer 5
Does not forward packets. As a result, it is possible to transmit a high-priority packet with a larger bandwidth than a low-priority packet.

[0005]

However, the conventional switch has the following problems.

First, the switch shown in FIG. 3 does not consider the priority of a packet, so that a packet having information such as voice and moving image and a packet having general data are treated the same. Packets having information such as audio and video require real-time performance. That is, transmission must be performed at appropriate time intervals. However, since such a packet requiring real-time performance is treated the same as a packet having general data not requiring real-time performance, the required communication quality (real-time performance) is not satisfied. Become.

On the other hand, in the switch shown in FIG. 4, a high-priority packet is prioritized. Therefore, if a packet requiring real-time performance is given a high priority, a bandwidth of a packet requiring real-time performance is secured. However, when the load on the network due to the high-priority packets increases, the chances of transferring the low-priority packets are reduced, and the low-priority packets suffer a serious communication delay. Further, under a high network load, packets from various transmission sources are mixed in the buffer even for high-priority packets, making it difficult to perform transmission at appropriate time intervals.
That is, real-time performance is not satisfied.

Accordingly, an object of the present invention is to solve the above-mentioned problems, to guarantee the real-time performance of packets that require real-time performance, and to reduce the delay of packets that do not require real-time performance.
An object of the present invention is to provide a packet transfer method with priority of a switch in a system.

[0009]

In order to achieve the above object, the present invention provides an LA using a switch for relaying a packet.
In the N system, a priority is defined for packets based on the necessity / unnecessity of real-time property, and a function of distributing to the switch whether to transfer a competing packet to an egress or to store it in a buffer, Is stored in the buffer, a function of setting a transmission rate of the packet, and a function of transferring a high-priority packet stored in the buffer to an egress according to the transmission rate.

[0010] The switch may be provided with a function of transferring low-priority packets stored in the buffer to the egress during idle time occurring when transferring high-priority packets to the egress according to the transmission rate. .

The switch may have a function of measuring a time interval between packets and setting the transmission rate based on the measured value.

[0012]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows the basic configuration of a switch for implementing the present invention. The switch includes a plurality of packet determination units 8, 9, 10, 11 for identifying the priority of the input packet and setting the transmission rate of the packet. Switch unit 12 for distributing packets to a certain direction), a plurality of conflict control units 15, 16, 17, 18 for distributing whether to transfer or store the packet to the egress based on priority or the like when a packet conflict occurs, A common buffer 14 for storing lost packets and a control unit 13 for sending high-priority packets stored in the common buffer 14 to an appropriate contention control unit according to a set transmission rate are provided.

In a LAN system using this switch, a priority is defined for a packet based on necessity / unnecessity of real-time property. That is, a packet that requires real-time characteristics, such as a packet having audio and video information, is a high-priority packet, and a packet that does not require real-time characteristics, such as a packet having general data, is a low-priority packet.

The packet determination units 8, 9, 10, and 11 identify whether the input packet is a high-priority packet that requires real-time performance or a low-priority packet that does not require real-time performance. In addition to the notification, the control unit 13 is notified of the required transmission rate for communication requiring real-time performance. The switch unit 12 includes a packet determination unit 8, 9, 10,
11 from the appropriate contention control units 15, 16, 1
Send to 7, 18. Contention control units 15, 16, 17, 18
Is the packet from the switch unit 12 and the common buffer 1
If there is no contention due to the packet taken out from No. 4, the packet is sent to the exit regardless of the priority. If a contention occurs, if the high-priority packet and the low-priority packet conflict, , And send the high priority packet to the exit with priority. If there is contention between high-priority packets, packets extracted from the common buffer 14 are preferentially sent to the exit according to the transmission rate, and non-packet-originated high-priority packets are extracted from the common buffer 14 according to the transmission rate. If so, send a randomly selected packet to the egress. The common buffer 14 stores the packet that lost the contention, and notifies the control unit 13 of an address indicating the storage location of the packet. The high-priority packets stored in the common buffer 14 are extracted according to the transmission rate notified to the control unit 13. Common buffer 1
The low-priority packets stored in No. 4 are extracted in the order of arrival on the switch.

As described above, the switch of FIG. 1 has a function of distributing a packet that is to be transferred to the egress or to store the packet in the common buffer, and a function of transmitting a high-priority packet when storing the packet in the common buffer. A function to set the rate and a function to transfer the high-priority packets stored in the common buffer to the egress according to the set transmission rate are provided.

In this switch, when a high-priority packet requiring real-time property is stored in the common buffer 14, this high-priority packet is transferred to the exit according to the transmission rate. Therefore, real-time performance is satisfied.

The nature of a packet that requires real-time characteristics is not bursty (randomly generated in time).
Since the data is transmitted from the transmission source at a constant transmission rate (time interval), the control unit 13 manages the transmission rate to be transferred according to the transmission rate from the transmission source. Specifically, a time interval between packets is measured, a transmission rate is set based on the measured value, and high-priority packets stored in the common buffer 14 are transferred to an egress according to the set transmission rate. . Further, the control unit 13 transfers the low-priority packets stored in the common buffer 14 to the exit in the idle time caused by managing the transmission rate to the switch in the order of arrival on the switch. As a result, as shown in FIG. 2, the transfer of the low-priority packet using the vacant band is performed, and the low-priority packet is prevented from suffering a serious transmission delay due to the high-priority packet.

Next, the operation of the switch shown in FIG. 1 will be described in detail.

First, the packet decision units 8, 9, 10, 11
When an input packet arrives, it identifies whether the input packet is a high-priority packet that requires real-time performance or another packet, that is, a low-priority packet that does not require real-time performance. 13 is notified. If the priority is high or low (requires / does not require real time), the priority information may be stored in the packet, and the switch may read the information. Whether the communication is necessary or not may be reported to the switch.

If the input packet is a packet requiring real-time performance, the packet determination units 8, 9, 10, and 11 notify the control unit 13 of the transmission rate of the packet. As the transmission rate, a rate previously declared by the sender of the packet to the switch can be used. Alternatively, the administrator may set a general transmission rate for audio and video for the switch, or the switch may hold the transmission rate in advance and use this transmission rate. The switch also sets such a general transmission rate as an initial value, and thereafter,
The transmission rate actually observed by the switch may be used. The observation of the transmission rate is the time from the end of a packet to the start of the next packet, that is, the time interval between packets is measured, the time interval is recorded, and the time interval between multiple packets is measured. Say to average.

The packets input to the packet decision units 8, 9, 10, 11 are distributed to the target competition control units 15, 16, 17, 18 by the switch unit 12, and any of the competition control units 15, 16, 17, 17 and 18 are reached.

In the contention control units 15, 16, 17, and 18, no packet contention occurs and the common buffer 14
If no packet is stored in the egress, the packet is forwarded to the egress. When a conflict between the high-priority packet and the low-priority packet occurs, the high-priority packet is transferred to the egress, and the low-priority packet is stored in the common buffer 14. When contention between high-priority packets occurs, a packet is randomly selected, one selected high-priority packet is transferred to the egress, and the other high-priority packet that has lost the contention is sent to the common buffer 14. Is stored in However, the packet extracted from the common buffer 14 according to the transmission rate is transferred to the exit preferentially.

The common buffer 14 stores the packet lost in the competition, and notifies the control unit 13 of an address indicating the storage location of the packet.

When the transfer of the packet is completed, the contention control units 15, 16, 17, and 18 notify the control unit 13 that the exit is available. In response to this notification, the control unit 13 transfers the packet stored in the common buffer 14 to the egress. At this time, if the high-priority packet is stored in the common buffer 14, the control unit 13 extracts the high-priority packet according to the notified transmission rate and transfers the packet to the exit. When the low-priority packet is stored in the common buffer 14, the control unit 13 extracts the low-priority packet during an idle time by extracting the high-priority packet according to the transmission rate, and transfers the low-priority packet to the exit.

As shown in FIG. 2, high-priority packets are transferred according to the transmission rate, which results in vacant bandwidth. A low-priority packet is transferred using this vacant band. Low priority packets are prevented from suffering significant transmission delays due to high priority packets.

[0027]

The present invention exhibits the following excellent effects.

(1) In the conventional method, communication quality assurance for packets requiring real-time performance was insufficient. However, the present invention secures the bandwidth of packets requiring real-time performance and guarantees real-time performance. You.

(2) In the conventional method, when priority control is performed on a packet that requires real-time performance, it is inevitable that a low-priority packet that does not require real-time performance suffers a communication delay. Unnecessary packet delay can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a principle configuration of a switch for implementing the present invention.

FIG. 2 is a time change diagram of a packet transferred to an egress of a switch according to the present invention.

FIG. 3 is a diagram illustrating a conventional packet transfer mechanism of a switch.

FIG. 4 is a diagram illustrating a conventional packet transfer mechanism of a switch.

[Explanation of symbols]

 8, 9, 10, 11 Packet determination unit 12 Switch unit 13 Control unit 14 Common buffer 15, 16, 17, 18 Contention control unit

Claims (3)

[Claims] 1. An L using a switch for relaying a packet.
In an AN system, a priority is defined for a packet based on the necessity / unnecessity of real-time property, and a function of distributing a competing packet to an egress or storing in a buffer in the switch, and a high priority packet When storing in the buffer, a function of setting a transmission rate of the packet, and a function of transferring a high-priority packet stored in the buffer to an exit according to the transmission rate, Priority-based packet transfer method for switches in a LAN system. 2. The switch has a function of transferring a low-priority packet stored in the buffer to an egress during an idle time when transferring a high-priority packet to an egress according to the transmission rate. 2. The method according to claim 1, wherein the packet transfer method is a priority-added packet transfer method for a switch in the LAN system. 3. The switch according to claim 1, wherein the switch has a function of measuring a time interval between packets and setting the transmission rate based on the measured value. Priority-based packet transfer method.