JP3584878B2 - Packet memory management device and memory management method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a packet memory management device used in a packet switch and the like, and more particularly, to a packet memory management device and a memory management method that prevent waste of memory space without impairing transfer performance.
[0002]
[Prior art]
A packet switch or a packet router temporarily stores a packet received from a line in a memory, determines a destination, and processes the packet. The processed packet is read from the memory (packet buffer) and transmitted to an appropriate destination. Such processing is required mainly at a line input unit and a line output unit such as a packet switch and a packet router.
[0003]
The packet data handled by the packet switch and the packet router is fixed length or variable length, and differs depending on the communication protocol. For example, ATM (Asynchronous Communication Mode) uses fixed-length packets, and IP (Internet Protocol) uses variable-length packets.
[0004]
Here, as a method of managing a packet buffer for temporarily storing a packet, a method of managing a memory area by equally dividing a memory area in accordance with the length of the fixed-length packet when handling a fixed-length packet is known. I have. Each equally divided memory area is called a cluster.
[0005]
According to this method, certain packet data is stored in a continuous address space of the memory area, but since it is continuous, burst transfer can be performed at the time of writing and reading data. This burst transfer is a data transfer method that allows access to consecutive sections in each cycle only by specifying the first address when accessing consecutive sections in the address space, enabling high-speed access It becomes. When accessing a group of sections that are not continuous, it is necessary to specify a start address for each section.
[0006]
On the other hand, as a memory management method for storing variable-length packets, two types of methods have been known so far. In the first method, as shown in the schematic explanatory diagram of FIG. 7, a cluster is determined by equally dividing a packet memory area in units of a maximum packet length specified by a communication protocol to be used, and a memory is managed in units of the cluster. In this method, one packet is sequentially stored in each cluster. In this method, continuity of the packet data in the address space is guaranteed, and burst transfer is possible. However, when the length of the stored packet is shorter than the cluster, there is a problem that the memory area is wasted. This tendency becomes more conspicuous as the size of the cluster increases and as the packet length decreases.
[0007]
In the second method, as shown in the schematic diagram of FIG. 8, the memory area is equally divided into short clusters, and the memory is managed in units of clusters. Is a method of dividing into a plurality of clusters and storing them. Here, the clusters are connected by a link list using a pointer.
[0008]
This method can use the memory area more efficiently for storing the packet than the above-described method. However, since data is distributed in a plurality of clusters, burst transfer of data is limited in units of clusters, which has a problem that transfer performance is affected.
[0009]
Note that a proposal for efficiently handling packets of different packet sizes is disclosed in Japanese Patent Application Laid-Open No. 8-1399752. The “buffer management device” disclosed in this publication includes a first buffer table for managing short packets and a long buffer for managing packets of a fixed buffer circuit (corresponding to the aforementioned memory). And a second buffer table for storing short packets in the buffer circuit using the first buffer table, and storing long packets in the buffer circuit using the second buffer table. And store it. As a result, even when packets having different sizes are given, no empty area (missing) which is unused due to the different size on the buffer circuit does not occur, and the limited buffer circuit can be used efficiently. .
[0010]
The data transmission system disclosed in U.S. Pat. No. 6,088,745 manages buffers using different buffer pointer lists according to the characteristics of the packet such as the protocol and the length, so that packets of different sizes can be managed. Is given, the data is stored in a continuous buffer having a constant length. This achieves both efficient use of the buffer memory and continuity of the stored packet data.
[0011]
[Problems to be solved by the invention]
It is another object of the present invention to provide a packet memory management device and a memory management method which ensure continuity in a memory space when storing variable-length packets to obtain good transfer performance, and at the same time prevent waste of the memory space. To provide.
[0012]
[Means for Solving the Problems]
In order to solve the problem, the present invention divides the packet memory management device into a plurality of equal-length sub-clusters that are grouped in correspondence with the length of input packets and are determined for each group according to the packet length. A packet memory divided into a number of fixed-length clusters to be managed, and input packets continuously stored in the sub-clusters of the cluster determined according to the length, and the stored packets are extracted as necessary. And a packet processing unit. Storing each packet in a subcluster of an appropriate length allows the packet memory to be used efficiently, and storing it continuously provides good transfer performance.
[0013]
A primary cluster table controller for managing a primary cluster table for storing an address indicating a free cluster in the packet memory; an address indicating a used cluster of the packet memory; and a used subcluster in the used cluster. Cluster table control unit for managing a secondary cluster table for storing an address designating a secondary cluster table, and a secondary cluster for managing a secondary cluster management table for storing an address of a free area of the secondary cluster table The management unit, temporarily stores the input packet and classifies the stored packet according to its length, from the primary cluster table control unit and the secondary cluster table control unit and from the secondary cluster management unit. Based on the information, the classified input packet is separated. Configuration to which a temporary storage unit packets written continuously in a predetermined sub cluster of the packet memory in accordance with the result. Thereby, appropriate packet memory management can be performed.
[0014]
The element of the primary cluster table is composed of a field 7a indicating the head address of an unused cluster on the packet memory 2 and a pointer 7b to the next element, and each element is connected by a link list. The table is equally divided into a plurality of secondary clusters, and each secondary cluster has a field indicating the start address of a specific cluster in the packet memory and a case where a packet is not written in all subclusters in the cluster. The secondary cluster management table includes a current sub-cluster address field indicating an address to which a packet is to be written next, and a transfer waiting packet number field indicating the number of packets waiting to be transferred in the cluster. Field indicating the top address of the unused secondary cluster above And consists pointer to the next element, by a configuration that is connected in a linked list, you can achieve the desired operation.
[0015]
The number of groups for the grouping may be determined according to the protocol of packet communication or the tendency of traffic, so that more efficient packet memory management can be performed.
[0016]
In addition, the method of the present invention includes a step of dividing the packet memory into clusters of equal length determined for each group and storing an address indicating each cluster in a primary cluster table, and indicating a cluster in use of the packet memory. A step of storing, in a secondary cluster table, an address to be used and an address indicating a used sub-cluster in a used cluster; and a step of storing an address of a free area of the secondary cluster table in a secondary cluster management table. Temporarily storing the stored packets and grouping the stored packets according to their lengths; and determining the packet memory for each group based on the information in the primary cluster table and the secondary cluster table. Subclusters of equal length Storing and adjusting the contents of the primary cluster table, the secondary cluster table, and the secondary cluster management table; extracting the packets stored in each of the clusters; and extracting the packets from the primary cluster table, the secondary cluster table, and the secondary cluster table. Adjusting the contents of the next cluster management table. Efficient use of packet memory and good transfer performance can be achieved.
[0017]
Each element of the primary cluster table comprises a field 7a indicating the head address of an unused cluster on the packet memory 2 and a pointer 7b to the next element, and each element is connected by a link list. The table is equally divided into a plurality of secondary clusters, and each secondary cluster has a field indicating the start address of a specific cluster in the packet memory and a case where a packet is not written in all subclusters in the cluster. A current subcluster address field indicating an address to which a packet is to be written next, and a transfer waiting packet number field indicating the number of packets waiting to be transferred in the cluster. The elements of the secondary cluster management table are defined in the secondary cluster table. Field indicating the start address of the unused secondary cluster of Can be pointers to elements become connected to each other by a linked list.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
[Embodiments] The present invention will be described in detail below with reference to the drawings and embodiments. FIG. 1 is a block diagram showing a configuration of a packet memory management device according to one embodiment of the present invention.
[0019]
The packet memory management device 100 shown in FIG. 1 includes a packet temporary storage unit 1 connected to an input line, a packet memory 2 and a subsequent FIFO memory 6, and a packet processing unit 10 connected to the packet memory and FIFO; , The packet temporary storage unit 1 and the FIFO; 6 and the secondary cluster table control unit 4 connected to the packet processing unit 10, the temporary cluster table control unit 3 and the secondary cluster connected to the secondary cluster table control unit 4. It comprises a management unit 5 and a secondary cluster table 8, a temporary cluster table 7 connected to the temporary cluster table control unit 3, and a secondary cluster management table 9 connected to the secondary cluster management unit 5.
[0020]
The packet temporary storage unit 1 temporarily stores a packet received from the line direction until all the packet data is received, and communicates with the secondary cluster table control unit 4 to obtain an address to which the packet is to be written. 2 is written in the packet data. The packet memory 2 stores the written packet until it is read out by the FIFO; The primary cluster table control unit 3 controls and manages free clusters in the packet memory 2 logically divided into a plurality of clusters by using the primary cluster table 7.
[0021]
The secondary cluster table control unit 4 determines the group to which the packet belongs from the length of the packet received by the packet temporary storage unit 1, and if necessary, communicates with the primary cluster table control unit 3 to write the packet. The address in the packet memory 2 to be determined is determined, notified to the packet temporary storage unit 1, and the information on the secondary cluster table 8 is updated. Communication with the secondary cluster management unit 5 is performed if necessary.
[0022]
The secondary cluster table 8 manages information of the cluster in use in cooperation with the secondary cluster table control unit 4. The secondary cluster management unit 5 manages an empty secondary cluster on the secondary cluster table 8 using the secondary cluster management table 9.
[0023]
FIG. 2 is an explanatory diagram showing a logical configuration of the packet memory 2 according to the embodiment of the present invention. The packet memory 2 is logically divided into a plurality of equal-length clusters for control and management. Each cluster is further divided into a plurality of sub-clusters and controlled and managed. One packet is stored in one subcluster. The number of sub-clusters in one cluster (therefore, the length of the sub-cluster) is not constant in all the clusters, but is different for each cluster group.
[0024]
FIG. 3 is a diagram illustrating an example of group and sub-cluster division, illustrating how the number of sub-clusters differs depending on a specific group. For example, the cluster of group A is equally divided into three sub-clusters, and the cluster of group B is equally divided into two sub-clusters. The received packet is appropriately associated with a cluster belonging to one of the groups and stored in the sub-cluster. Which group it corresponds to is determined by the length of the packet.
[0025]
Specifically, for example, a packet of 64 bytes or less is associated with a group A, and a packet of 65 to 128 bytes is associated with a group B. Decide.
[0026]
Note that the entire length of one cluster is set to a length that can store a plurality of packets of the group to which the longest packet belongs in the device, so that the group to which a packet that is slightly shorter than the longest belongs also has a long length. This is preferable because it can be efficiently stored in one type of cluster having the same size.
[0027]
Next, FIG. 4 is an explanatory diagram showing the configuration of the primary cluster table 7 in the embodiment of the present invention. The primary cluster table 7 manages a free cluster area in the packet memory 2. Each element of the primary cluster table 7 includes a field 7a indicating the head address of an unused cluster on the packet memory 2 and a pointer 7b to the next element, and is connected by a link list.
[0028]
FIG. 5 is an explanatory diagram showing the configuration of the secondary cluster table 8 in the embodiment of the present invention. The secondary cluster table 8 is used for managing a cluster in use. The secondary cluster table 8 is logically equally divided into a plurality of secondary clusters. Each of the secondary clusters has a field 8a indicating the head address of a specific cluster in the packet memory 2, and a current subcluster indicating an address to which a packet should be written next when no packet has been written in all subclusters in the cluster. It comprises an address field 8b and a transfer waiting packet number field 8c indicating the number of packets waiting to be transferred in the cluster.
[0029]
FIG. 6 is an explanatory diagram showing the configuration of the secondary cluster management table 9 in the embodiment of the present invention. The secondary cluster management table 9 manages the free area of the secondary cluster table 8. Each element is composed of a field 9a indicating the head address of an unused secondary cluster on the secondary cluster table 8 and a pointer 9b to the next element, and is connected by a link list.
[0030]
Next, the operation of the apparatus of this embodiment shown in FIG. 1 will be described with reference to the above-mentioned respective drawings. When packet reception is started from the line direction, the packet temporary storage unit 1 waits while holding the packet data until all the packet data is received. When the reception of the packet is completed, the temporary packet storage unit 1 notifies the secondary cluster table control unit 4 of the length of the received packet. The secondary cluster table control unit 4 determines the group to which the packet belongs from the length of the packet.
[0031]
When a packet is received for the first time in the initial operation state of the device, the secondary cluster table control unit 4 requests the unused cluster information from the primary cluster table control unit 3 and sends the secondary cluster management unit 5 the secondary cluster information. Request. The primary cluster table control unit 3 hunts (designates) a cluster from the primary cluster table 7 and transmits it to the secondary cluster table control unit 4. The secondary cluster management unit 5 hunts the secondary cluster and sends it to the secondary cluster table control unit 4.
[0032]
Subsequently, the secondary cluster table control unit 4 writes the cluster start address, the cluster start address + 1, and the address of the subclass (determined according to the group) in the obtained secondary cluster, and writes 1 in the transfer waiting packet field. At the same time, the start address of the sub-cluster (in the initial state, the start address of the cluster) and the start address of the secondary cluster to which the packet is written in the packet temporary storage unit 1 are notified.
[0033]
At this point, there are a plurality of sub-clusters in which packets have not yet been written in the designated cluster (accurately, no packet has been written yet), but the secondary cluster table control unit 4 For a cluster to which a packet can be written, the start address of the corresponding secondary cluster is held for the number of groups. The start address of the secondary cluster held simultaneously in the same group is one. As a result, it is possible to immediately determine to which sub-cluster the packet to be received next should be written.
[0034]
When the packet data is written in all the sub-clusters in the same cluster, the head address of the corresponding secondary cluster is discarded. When the packet data is written to all the sub-clusters in the same cluster, a value indicating that the writing has been completed (here, all 1s) is set in the current sub-cluster address field in the corresponding secondary cluster. Written.
[0035]
The packet temporary storage unit 1 that has obtained the address of the cluster to which the received and held packet is to be written from the secondary cluster table control unit 4 writes the packet to that address. At this time, the packet temporary storage unit 1 writes the secondary cluster head address acquired from the secondary cluster table control unit 4 and the packet length information held by itself, at the head of the packet. Subsequently, the packet processing unit 10 is notified of the reception of the packet.
[0036]
The packet processing unit 10 reads the protocol header of the packet from the packet memory 2 to determine the destination of the packet, and registers the start address of the subcluster in which the packet is stored in the FIFO;
[0037]
The FIFO 6 reads the registered packet from the packet memory 2 and reads out the packet data having the length described in the packet length information, and transmits the packet to the designated destination as a packet. At this time, the secondary cluster head address added to the head of the packet is not transmitted to the destination but is transmitted to the secondary cluster table control unit 4.
[0038]
The secondary cluster table control unit 4 accesses the corresponding secondary cluster of the secondary cluster table 8 using the received secondary cluster head address as a key, and decrements the value of the transfer waiting packet number field. At this time, if the value of the transfer waiting packet number field is 0 and the value of the current sub-cluster address is all 1, the corresponding cluster is returned to the primary cluster table control unit 3 (notified that it is empty). ). At the same time, the secondary cluster is also returned to the secondary cluster management unit 5.
[0039]
In some cases, before the packet data is written to all the sub-clusters of one cluster, the packet is transmitted from that cluster, and as a result, the value of the transfer queue packet number field in the secondary cluster becomes 0. In some cases, the cluster is not returned.
[0040]
The memory area can be used more efficiently by determining the number of groups in the above description to an appropriate number in accordance with the communication protocol and the tendency of traffic.
[0041]
【The invention's effect】
According to the present invention, the packet memory is equally divided into fixed-length clusters, each cluster is further equally divided into a plurality of subclusters according to the packet length, and the packets are classified into a plurality of groups according to the length, and are divided into the same group. Since the belonging packet is stored in the sub-cluster in the same cluster, the packet data is efficiently stored in the memory, and at the same time, the data is stored in a continuous position in the memory space. This has the effect that packet memory management can be performed while preventing waste of memory space.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a packet memory management device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a logical configuration of a packet memory 2 in the embodiment.
FIG. 3 is an explanatory diagram of group and sub-cluster division according to the embodiment.
FIG. 4 is an explanatory diagram illustrating a configuration of a primary cluster table according to the embodiment;
FIG. 5 is an explanatory diagram illustrating a configuration of a secondary cluster table according to the embodiment;
FIG. 6 is an explanatory diagram illustrating a configuration of a secondary cluster management table according to the embodiment;
FIG. 7 is a schematic explanatory view showing a conventional packet memory management example.
FIG. 8 is a schematic explanatory view showing a conventional example of packet memory management.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Packet temporary storage part 2 ... Packet memory 3 ... Primary cluster table control part 4 ... Secondary cluster table control part 5 ... Secondary cluster management part 6 ... FIFO
7 Primary cluster table 8 Secondary cluster table 9 Secondary cluster management table 10 Packet processing unit 100 Packet memory management device

Claims (5)

A packet memory management device used for packet switching,
Packet memory divided into a number of fixed-length clusters that are grouped according to the length of the input packet and that are divided into a plurality of equal-length subclusters that are determined for each group according to the packet length and managed When,
A packet processing unit that continuously stores the input packet in the sub-cluster of the cluster determined according to the length thereof and extracts the stored packet as needed;
A primary cluster table control unit that manages a primary cluster table for storing an address indicating an empty cluster in the packet memory;
A secondary cluster table control unit that manages a secondary cluster table for storing an address indicating a used cluster of the packet memory and an address indicating a used sub-cluster in the used cluster;
A secondary cluster management unit that manages a secondary cluster management table for storing addresses of free areas of the secondary cluster table;
While temporarily storing the input packet and classifying the stored packet according to its length, based on information from the primary cluster table control unit and the secondary cluster table control unit and the secondary cluster management unit A packet temporary storage unit that continuously writes the classified input packet to a predetermined sub-cluster of the packet memory according to the classification result;
A packet memory management device comprising: The elements of the primary cluster table are composed of a field 7a indicating a head address of an unused cluster on the packet memory 2 and a pointer 7b to the next element, and each element is connected by a link list.
The secondary cluster table is equally divided into a plurality of secondary clusters, and each secondary cluster is written with a field indicating the start address of a specific cluster in the packet memory and all subclusters in the cluster. If it is not, a current sub-cluster address field indicating the address to which the packet is to be written next, and a transfer waiting packet number field indicating the number of packets waiting to be transferred in the cluster,
The element of the secondary cluster management table is composed of a field indicating a head address of an unused secondary cluster on the secondary cluster table and a pointer to the next element, and is connected by a link list. The packet memory management device according to claim 1 . 3. The packet memory management device according to claim 1, wherein the number of groups for the grouping is determined according to a protocol of packet communication and a tendency of traffic. A packet memory management method of a packet memory management device used for packet switching,
Dividing the packet memory into clusters of equal length determined for each group and storing addresses indicating individual clusters in a primary cluster table;
Storing an address indicating a used cluster of the packet memory and an address indicating a used sub-cluster in the used cluster in a secondary cluster table;
Storing the address of the free area of the secondary cluster table in a secondary cluster management table;
Temporarily storing the input packets and grouping the stored packets according to their length;
The packets are continuously stored in sub-clusters obtained by dividing the packet memory into equal lengths determined for each group based on the information in the primary cluster table and the secondary cluster table, and the primary cluster table and the secondary cluster are stored. Adjusting the contents of the secondary cluster table and the secondary cluster management table;
Extracting a packet stored in each of the clusters and adjusting the contents of the primary cluster table, the secondary cluster table, and the secondary cluster management table. Each element of the primary cluster table includes a field 7a indicating a head address of an unused cluster on the packet memory 2 and a pointer 7b to the next element, and each element is connected by a link list.
The secondary cluster table is equally divided into a plurality of secondary clusters, and each secondary cluster is written with a field indicating the start address of a specific cluster in the packet memory and all subclusters in the cluster. If not, it consists of a current sub-cluster address field indicating the address to which the packet should be written next, and a transfer waiting packet number field indicating the number of packets waiting to be transferred in the cluster.
The element of the secondary cluster management table is composed of a field indicating a head address of an unused secondary cluster on the secondary cluster table and a pointer to the next element, and is connected by a link list. Item 5. The packet memory management method according to Item 4 .

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