JPH11313079A - Atm communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform flexible priority control in accordance with the kind of a communication service by extracting priority information of an internet protocol(IP) packet from payload information of an ATM cell and allocating an ATM cell to plural different priority buffers with the information, based on a connection identifier VPIVCI value of the ATM cell. SOLUTION: An inputted ATM cell is allocated to a VPIVCI value (corresponding to VC1 to VC3) and each different priority buffer 103 prepared for each IP priority value by an ATM cell header analyzing part 101 and an IP header analyzing part 102. The allocated ATM cell is read according to a schedule that is set with an IP priority value as reference from a cell extracting part 104. Priority control that is conscious of a service of a protocol that is higher than an ATM layer is performed and priority control of a packet unit is performed even in the same VC connection by allocating a cell to the different priority buffer 103 in this way by considering priority information of an IP packet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ATM communication device.

[0002]

2. Description of the Related Art Conventionally, a switching device in an ATM communication network,
In the relay device, various priority controls are performed on ATM cells input into the device in order to guarantee communication quality.

[0003] As one of them, ATM cells of a plurality of connections input into the device are stored in buffers corresponding to defined priorities and classes, and cells stored in high priority buffers are prioritized. There is a technique of reading, multiplexing, and outputting. As a result, the cell discard rate at the time of congestion is reduced, and communication suitable for the content of the communication service is realized.

[0004] As a concrete form of realizing the above priority or class, there is a C / C provided in a header area of an ATM cell.
Techniques for following priority / non-priority cells defined by the LP bit (for example, "ATM cell buffer control method" Aramaki (NEC), Japanese Patent Application No. 7-58663), CBR and VBR standardized in ATM communication, etc. Method of dividing buffers according to service class ("Multi-class A
TM Call Admission Control Method and Apparatus "by Aida (Nippon Telegraph and Telephone Corporation), Japanese Patent Application No. 8-157269, and a technique of providing a buffer for each connection and reading out according to a weighted schedule (" Weighted Round ").
-Robin Cell Multiplexing
in a General-Purpose ATM
SwitchChip ", IEEE JSAC-Fal
l 1991, "Study of Shared Bandwidth Control Method with Guaranteed Minimum Bandwidth", Kobayashi et al. (Nippon Telegraph and Telephone), IEICE Technical Report SSE97-92, etc.

On the other hand, in recent years, Internet technology has attracted attention, and IP has become mainstream.
IP over ATM (IETF R)
FC1577) is widely used. Also recently,
IPv6 (IP version 6, IETFRF) is newly added from the conventional IPv4 (IP version 4).
C1883) has been standardized.

There are several features of IPv6 as compared with IPv4, one of which is the definition of the priority of IP packets. TOS for expressing the service type of the IP packet in the header of the IP packet even in IPv4
Although a (Type Of Service) area has been defined, it is hardly used at present.

In IPv6, an area corresponding to the TOS area of IPv4 is provided as a priority area in the basic header of an IP packet (FIG. 7), and is given a clearer meaning than IPv4.

The value of this priority area takes a value from 0 to 15 and is divided into those for congestion control and those for non-congestion control, and further defines what communication service corresponds to each value. . For example, the value 2 is sporadic data transfer such as e-mail, and the value 6 is interactive communication such as remote login. The value of the I priority is used for the priority control processing of the packet in the IP router device or the end terminal.

[0009]

As described above, while there is a priority control technique according to the service class in the ATM, control in the IP in consideration of the unique service class has been activated.

However, both service classes and priority control,
Communication quality assurance methods do not always match,
In communication using IP as an upper protocol of M, it can be said that the conventional ATM cell buffer priority control method is not completely suitable. For example, various types of packets such as file transfer, mail transfer, and control information may flow in the same ATM connection.
Although priority control can be performed in consideration of these categories based on the priority information of the P packet, the conventional buffer priority control at the ATM level is treated the same in the end, and there is a problem that discarding occurs in units of cells. .

The present invention has been made in view of the above points, and has as its object to provide an ATM communication apparatus capable of performing flexible priority control according to the type of communication service.

[0012]

SUMMARY OF THE INVENTION The present invention provides an ATM (As
In a switching device or a relay device in an asynchronous transfer mode (asynchronous transfer mode) communication network, IP (Int) is obtained from payload information of an ATM cell.
Internet Protocol) packet priority information (hereinafter, referred to as “IP priority value”), and the information and A
Based on the connection identifier VPIVCI value of the TM cell,
Buffers prepared for multiple priorities in the device (hereinafter referred to as
A method and apparatus configuration for distributing ATM cells to "priority buffers".

In FIG. 1, which is a conceptual diagram of the present invention, an ATM cell input into the device is converted into a VPI by an ATM cell header analysis unit 101 and an IP header analysis unit 102.
The VCI values (corresponding to VC1, VC2, and VC3 in FIG. 1) and the priority-based buffers 103 prepared for the respective IP priority values are distributed. The sorted ATM cells are read from the cell extractor 104 according to a schedule set based on the IP priority value.

In this way, by allocating cells to buffers of different priorities in consideration of the priority information of IP packets, priority control can be performed in consideration of services of protocols higher than the ATM layer, and the same VC connection can be used. However, priority control can be performed in packet units.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a configuration of a priority control buffer processing section in an embodiment of the ATM communication apparatus according to the present invention.

The ATM cell is input from the cell input block 201, and is output from the cell extraction block 210 to another block in the device through internal processing.

The VPIVCI extraction block 202 receives the input A
From the VPIVCI area of the TM cell header to the VPIVCI
This is a block that extracts a value, converts the VPIVCI value into an internal connection identifier, and outputs it.

The last cell detection block 203 is an input ATM.
By monitoring the PTI area of the cell header, it detects whether the input ATM cell is the last cell of the packet to which it belongs.

The packet management table 204 holds the information shown in FIG. The packet management table stores information on the reception status and the IP priority value using the connection identifier for identifying the VPIVCI to which the connection is established as a key attribute. The item of the reception status holds a value indicating the reception status of the packet with the corresponding connection identifier. For example, the state where the last cell has been received (packet reception completed state)
0 if not, 1 if not (packet receiving state)
Is written. The IP priority value field holds the IP priority value of the currently received IP packet in the VC connection corresponding to the connection identifier. I in FIG.
As shown by the structure of the basic header of Pv6, the priority area is 4 bits wide and takes a value from 0 to 15,
The packet management table also covers values of 16 or more.
Values greater than 16 are for non-IPv6 packets.

The IP header analysis block 205 extracts the value of the priority area of the IP packet from the payload information of the input cell.

The buffer management table 207 holds the information shown in FIG. The buffer management table in FIG. 4 stores buffer information prepared for each buffer identifier using the buffer identifier as a key attribute. The buffer identifier is an identifier of the buffer 208 for each priority. In FIG. 4, the end address indicates the memory address of the buffer to be stored next in the buffer, and indicates the storage address of the cell information that has arrived most recently in the buffer. The head address indicates the memory address of the buffer to be read next in the buffer, and indicates the storage address of the cell information that has arrived the oldest in the buffer. The number of stored cells indicates the number of cells of the buffer currently stored. The allowable storage cell number indicates the allowable storage cell number of the buffer.

The buffer identifier generation block 206 generates a buffer identifier of the buffer management table 207 from the connection identifier of the packet management table and the IP priority value.

The cell storage block 209 distributes the input cells to the priority-based buffers 208 according to the information in the buffer management table 207.

The cell extraction block 210 includes a scheduler 2
The cells are read and output according to the eleventh read schedule.

The scheduler 211 holds information indicating from which priority-based buffer a cell is to be extracted next based on the IP priority value.

Next, the operation of the embodiment shown in FIG. 2 will be described.

The header and payload of the ATM cell input from the cell input unit 201 are analyzed in a VPIVCI extraction block 202, a last cell detection block 203, and an IP header analysis block 205.

The VPIVCI extraction block 202 extracts a VPIVCI value from the header area of the input ATM cell, converts the VPIVCI value into an internal connection identifier, and converts the value into FIG.
Management table 20 as the connection identifier of
4 is output. The buffer identifier generation block 20
6 also outputs the value of the connection identifier.

In the packet management table 204, the VPI
Reception state information and IP priority value information corresponding to the connection identifier input from the VCI extraction block 202 are held, and read / write is performed in response to a request from another block. Further, the value of the IP priority value corresponding to the referenced connection identifier is output to the buffer identifier generation block 206.

The last cell detection block 203 monitors the PTI area in the header area of the input ATM cell, and receives the connection identifier currently referred to in the packet management table 204 when the last cell of the packet is detected. Updating the status to 0 indicates a packet reception completion status. If it is not the last cell of the packet, the value of the reception state is set to 1 to indicate a packet reception state.

In the IP header analysis block 205, if there is an input cell, it is first determined whether or not the packet is an IPv6 packet by monitoring the payload of the ATM cell. In the case of an IPv6 packet, an IP priority value is subsequently extracted. If the packet is not an IPv6 packet, a default value (for example, 16) is set as the IP priority value. Next, the value of the reception state of the currently referenced connection identifier is read from the packet management table 204.
The value of the IP priority value attribute in the packet management table is updated to the extracted IP priority value. The timing at which the value of the reception state is read from the packet management table 204 is determined by the last cell detection block 203.
Later than the timing of accessing

In the buffer identifier generation block 206,
From the connection identifier input from the VPIVCI extraction block 202 and the IP priority value input from the packet management table 204, a buffer identifier managed by the buffer management table 207 is generated, and the cell storage block 2
09 is output.

The cell storage block 209 uses the buffer identifier input from the buffer identifier generation block 206 as a key to store the buffer address (the value of the end address of the buffer management table 207) as the storage destination of the input cell from the buffer management table 207. get. The cell storage block 209 stores the input cell at the acquired buffer address (corresponding to the buffer 208 for each priority), increments the value of the number of cells stored in the buffer management table 207, and updates the value of the end address.

The input cell sorted by the cell storage block 208 is eventually the connection identifier and I
It will be uniquely identified by the combination of P priority values. That is, the priority-based buffer 208 is classified into the number of target IP priority values (hereinafter, “service category”).
), There is a buffer for each connection in each service category.

The cell extraction block 210 acquires the buffer identifier of the next priority buffer to be extracted next from the priority buffer 208 according to the information of the scheduler 211, and stores the memory address of the first cell of the priority buffer in the buffer. The cell is read from the management table 207 (the value of the head address) and cells are extracted. After cell extraction, the cell extraction block 210 updates the start address of the buffer management table and the value of the number of stored cells.

An example of the operation of the cell extraction block 210 will be described with reference to the flowchart of FIG.

First, the service category to be polled next is determined with reference to the scheduler (501). The scheduler holds a table describing the polling frequency according to the IP priority value, and a configuration using, for example, a CAM is known in the related art (for example, “Weight”).
ed Round-Robin Cell Multi
plexing in a General-Purp
oose ATM Switch Chip ", IEEE
JSAC-Fall 1991). Next, a priority-based buffer to be polled first among the priority-based buffers belonging to the determined service category is determined (50).
2). When a buffer by priority is selected, the address of the first cell of the buffer is obtained from the buffer management table,
Recognize the VPIVCI of the cell existing there (50
3). If the cell of the VPIVCI is not extracting a packet from a buffer belonging to another service category (504), the cell is read out, the buffer management table is updated (505), and the process of 506 is performed. If the buffer is being extracted, it is determined whether or not there is a next priority-based buffer belonging to the service category to be searched (506) without reading, and if so, the priority-based buffer is set as the next polling target. The processing from 503 is repeated. If not, the process is repeated from step 501.

Next, another embodiment of the present invention will be described.

FIGS. 7 and 8 show another embodiment.

This embodiment is an example in the case where a conventional packet-based discard function is provided.

As an outline of the function, when the number of storage cells becomes larger than the preset allowable storage cell size of the buffer for each priority due to factors such as burst transfer of input cells, the corresponding VC connection Is discarded, and thereafter the cell of the VC connection is discarded until the last cell is detected. However, only the last cell is not discarded.

FIG. 7 shows the packet management table of FIG. 3 with an additional discard mode item. If this value is 1, it is defined that the cell with the connection identifier is in the discard mode, and during this time, the cell corresponding to this connection identifier is kept discarded.

The operation will be described with reference to FIG. Since the basic configuration and operation are the same as in FIG. 2, only different parts will be described.

In the last cell detection block 803, when the last cell is detected, the value of the reception state and the value of the discard mode in the packet management table 804 are updated. Specifically, when the value of the discard mode is 1, the discard mode state is canceled by updating to 0, and when the value of the discard mode is 0, it is left as it is.

The cell discard block 812 refers to the information of the packet management table 804 and the information of the buffer management table 807 using the buffer identifier input from the buffer identifier generation block 806 as a key, and performs the following processing. If the value of the receiving state is 0 (when the input cell is the last cell), the input cell is input to the cell storage block 809 as it is. Reception state value is 1 and discard mode value is 1.
If, the input cell is discarded. Reception status value is 1
If the value of the discard mode is 0 and the value of the number of stored cells is larger than the value of the allowable number of stored cells, the input cell is discarded, and the value of the discard mode is set to 1.

[0047]

According to the present invention, in the ATM layer, the IP
For v6 packets, flexible priority control according to the type of communication service can be performed, and priority control can be performed on a packet basis within the same VC connection. As a result, the packet discard rate is suppressed, and quality control according to the actual service becomes possible. For example, a buffer for each priority corresponding to an IP priority value used for a mail service has a large allowable storage cell number, a low polling frequency, and a service such as voice that does not allow delay than packet drop. The communication quality can be improved by setting the number of allowable storage cells small and setting the polling frequency high. Such control is impossible with conventional control only at the ATM cell level.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the concept of the present invention.

FIG. 2 is a diagram showing a configuration of a priority control buffer processing unit in an embodiment of the ATM communication device according to the present invention.

FIG. 3 is a diagram showing a configuration of a packet management table in the embodiment shown in FIG.

FIG. 4 is a diagram showing a configuration of a buffer management table in the embodiment shown in FIG.

FIG. 5 is a flowchart showing an operation example of cell extraction in the embodiment shown in FIG. 2;

FIG. 6 is a diagram showing a basic header configuration of IPv6.

FIG. 7 is a diagram showing a configuration of a packet management table in the embodiment shown in FIG.

FIG. 8 is a diagram showing a configuration of a priority control buffer processing unit in another embodiment of the ATM communication apparatus according to the present invention.

[Explanation of symbols]

 Reference Signs List 101 ATM cell header analysis unit 102 IP header analysis unit 103 Buffer by priority 104 Cell extraction unit 201, 801 Cell input block 202, 802 VPIVCI extraction block 203, 803 Last cell detection block 204, 804 Packet management table 205, 805 IP header analysis Block 206, 806 Buffer identifier generation block 207, 807 Buffer management table 208, 808 Buffer by priority 209, 809 Cell storage block 210, 810 Cell extraction block 211, 811 Scheduler 812 Cell discard block

Claims (6)

[Claims] 1. Priority information of an IP packet is extracted from payload information of an ATM cell, and the priority information and the AT
An ATM cell priority buffer control method, wherein the ATM cells are distributed to buffers prepared for a plurality of priorities based on a VPIVCI value which is a connection identifier of an M cell. 2. The ATM cell priority buffer control method according to claim 1, wherein said ATM cells are read from a buffer prepared for each priority based on said priority. 3. An ATM cell header analysis unit for analyzing a header of an input ATM cell, an IP header analysis unit for analyzing an IP header of the ATM cell, and a priority class prepared for each VPIVCI value and IP priority value. Buffers and
An ATM communication device comprising: a distributing unit that distributes the ATM cells to the priority-based buffers based on a result of analysis by the ATM cell header analyzing unit and the IP header analyzing unit. 4. The method according to claim 1, wherein the scheduler set on the basis of the IP priority value outputs the ATM from the priority buffer.
4. The ATM communication device according to claim 3, further comprising a cell extracting means for reading a cell. 5. A cell input block for inputting an ATM cell and a VPIVCI field in an input ATM cell header.
A VPIVCI extraction block that extracts a PIVCI value, converts the VPIVCI value into an internal connection identifier, and outputs the block; and monitors the PTI area of the input ATM cell header to determine whether the input ATM cell is the last cell of the packet to which it belongs. The reception state, I
A packet management table in which information of the P priority value is stored;
An IP header analysis block for extracting a value of a priority area of an IP packet from payload information of an input cell; a buffer management table for storing buffer information prepared for each buffer identifier using the buffer identifier as a key attribute; A buffer identifier generation block for generating a buffer identifier of the management table from the connection identifier and the IP priority value of the packet management table; a buffer for each priority provided for each priority; A cell storage block to be allocated to the priority-based buffers in accordance with a scheduler that holds information indicating from which priority-based buffer the next cell is to be extracted based on the IP priority value; Cell extraction to read and output ATM communication apparatus characterized by comprising a block. 6. The packet management table stores information on a reception state, an IP priority value, and a discard mode using a connection identifier for identifying a VPIVCI to which a connection is established as a key attribute. When a last cell is detected, information of the discard mode of the packet management table is updated to a discard mode, and a cell discard block for discarding an input cell based on the information of the discard mode of the packet management table is further provided. The ATM communication device according to claim 5, wherein